We would like to thank Nick Lenhard for the critical reading and editing of this manuscript. We would also like to thank Andrew Camilli and Anthony Campagnari for the bacterial strains and Bruce Davidson for the viral strains. This work was supported by the National Institute of Health Grant (R21AG071268-01) to J.L. and the National Institute of Health Grants (R21AI145370-01A1), (R01AG068568-01A1), (R21AG071268-01) to E.N.B.G.

The authors have no conflicts of interest to disclose.

Most of the existing S. pneumoniae/IAV co-infection experimental studies rely on bacterial delivery into the lungs of mice pre-infected with IAV. These models have helped identify changes in the pulmonary environment and systemic immune response that render the host susceptible to secondary bacterial infection15,16,17,32,33,34,35,36,37. However, these models have failed to mimic the transition of S. pneumoniae from an asymptomatic colonizer to a pathogen capable of causing serious lung and systemic infections. Further, these models are not suitable for studying the host factors and host-pathogen interactions in the upper respiratory tract that contribute to susceptibility to infection. A prior model for the movement of pneumococci from the nasopharynx to the lung after IAV infection relied on bacterial infection of the nasopharynx followed by viral infection. However, it failed to reproduce the severe signs of disease observed in human patients21. The modified murine infection model described here recapitulates the transition of S. pneumoniae from asymptomatic carriage to a pathogen that causes severe clinical disease.
A critical step of this model is establishing S. pneumoniae infection in the nasopharynx. Streptococcus pneumoniae form biofilms and colonize the nasopharynx at different efficiencies21,38. To establish consistent infection, at least 5 &#215; 106 CFU of the biofilm-grown bacterial&#160;strains tested so far are required23. It is recommended that any new bacterial strain be tested for stable infection of the nasopharynx prior to viral infection. For viral co-infection, previous studies have found that intranasal infection with IAV is required for the dispersion of the bacteria from the nasopharynx21,22,23. In those prior studies, 500 PFU of IAV for intranasal delivery were used, while in this study, 200 PFU were sufficient to increase bacterial numbers in the nasopharynx. IAV infection is not limited to the upper airways and can spread to the lungs39,40, which is key for rendering the pulmonary environment more permissive for bacterial infection15,16,41. The delivery of IAV to the lungs can be achieved by either intranasal delivery or intratracheal installation of anesthetized mice. Prior work with BALB/cByJ mice found that intranasal delivery results in viral pneumonia21; however, access of the inoculum to the lungs following intranasal inoculation is more restricted in C57BL/6 mice. In C57BL/6 mice, intratracheal installation is required for consistent delivery of the virus23. In this model, prior bacterial colonization accelerates the presentation of disease symptoms after viral infection23. As viral infection can itself cause disease symptoms with potential variation in kinetics, it is recommended to first test a range of doses for any new viral strain tested and choose a dose that reveals accelerated kinetics in co-infected hosts.
The lungs provide another critical readout for disease evaluation in this model. For the assessment of pathogen burden and immune cell influx, a lung from the same mouse can be used. However, as infection and inflammation severity can differ between lobes, it is recommended to not take different lobes of the same lung for the various assessments. Rather, all the lobes can be minced into small pieces, mixed well together, and then parsed out equally for the different assessments. Similarly, the nasopharynx can be used for the enumeration of bacterial CFU or viral PFU and immune response. However, the number of cells obtained from the washes and tissue is too low to perform flow cytometry without pooling the samples from mice within the same group. Alternatively, inflammation in the nasopharynx can be assessed histologically23.
A critical feature of this model is that it recapitulates the clinical disease seen in patients. In humans, secondary pneumococcal pneumonia following IAV infection often results in obvious signs of disease, including cough, dyspnea, fever, and muscle aches that can lead to hospitalizations, respiratory failure, and even death8,15,42,43. This model recapitulates the severe signs of clinical disease observed in humans in terms of difficulty in breathing (reflected in the breathing score) and overall malaise (reflected in posture and movement scores) displayed by the mice, as well as death in some of the healthy young controls. The exacerbated disease symptoms in co-infected mice are likely a result of both bacterial dissemination to the lungs and impaired viral clearance in mice with pneumococcal carriage23. A limitation of the model is that the incidence of clinical disease and bacterial dissemination from the nasopharynx varies between mice and is influenced by bacterial strain, host age, and genotype21,22,23. Reflecting this, for invasive strains, the progression from localized infection (with no detectable bacteremia) to death can occur within 24 h. Therefore, for a true assessment of systemic spread, bacteremia should be followed over shorter intervals (every 6-12 h). Similarly, the disease score can change rapidly, particularly in the first 72 h following co-infection. Therefore, to closely track the disease symptoms, it is advisable to monitor mice three times per day for days 1-3 post IAV infection.
In summary, this model replicates the movement of S. pneumoniae from an asymptomatic colonizer of the nasopharynx to a pathogen capable of causing pulmonary and systemic disease upon IAV infection. In this model, IAV triggers the transition of S. pneumoniae via modifying the bacterial behavior in the nasopharynx, increasing bacterial spread to the lung, and altering antibacterial immunity23. Similarly, bacterial carriage blunts the antiviral immune responses and impairs IAV clearance from the lungs23. This renders this model ideal for parsing out changes in immune responses in single versus polymicrobial infections. Additionally, the course of disease following co-infection is, in part, dependent on the strain of pneumococci present in the nasopharynx. Therefore, the model is suited to dissecting the bacterial factors required for asymptomatic colonization versus pathogenic transition of S. pneumoniae. Lastly, this model reproduces the susceptibility of aging to co-infections, and although this was not tested here, it can be easily used to assess the impact of host background on the disease course. In conclusion, separating carriage and disease into distinct steps provides the opportunity to analyze the genetic variants of both the pathogens and the host, allowing the detailed examination of the interactions of an important pathobiont with the host at different phases of disease progression. Moving forward, this model can be used to tailor treatment options for vulnerable hosts.

Streptococcus pneumoniae (pneumococcus) are Gram-positive bacteria that asymptomatically reside in the nasopharynx of most healthy individuals1,2. Promoted by factors that are not completely defined, pneumococci can transition from benign colonizers of the nasopharynx to pathogens that spread to other organs resulting in serious infections, including otitis media, pneumonia, and bacteremia3. Pneumococcal disease presentation is, in part, dependent on strain-specific differences, including the serotype, which is based on the composition of capsular polysaccharides. There have been over 100 serotypes characterized so far, and some are associated with more invasive infections4,5. Several other factors increase the risk of pneumococcal disease. One such factor is viral infection, where the risk of pneumococcal pneumonia is increased 100-fold by IAV6,7. Historically, S. pneumoniae is one of the most common causes of secondary bacterial pneumonia following influenza and is associated with worse outcomes8. Another major risk factor is advanced age. In fact, S. pneumoniae is the leading cause of community-acquired bacterial pneumonia in elderly individuals above 65 years old9,10. Elderly individuals account for the majority (&#62;75%) of deaths due to pneumonia and influenza, indicating that the two risk factors-aging and IAV infection-synergistically worsen disease susceptibility11,12,13,14. However, the mechanisms by which viral infection prompts the transition of pneumococci from asymptomatic colonizer to invasive pathogen and how this is shaped by host factors remain poorly defined. This is largely due to the absence of a small animal model that recapitulates the transition from asymptomatic pneumococcal colonization to critical clinical disease.
Co-infection studies have classically been modeled in mice inoculated with pneumococci directly into the lungs 7 days following influenza infection15,16. This reproduces the susceptibility to secondary bacterial pneumonia and is ideal for studying how antiviral immune responses impair antibacterial defenses17. However, longitudinal studies in humans have demonstrated that pneumococcal carriage in the nasopharynx, where the bacteria can form asymptomatic biofilms18, is uniformly associated with invasive diseases19,20. Bacterial isolates from infections of the middle ear, lung, and blood are genetically identical to those found in the nasopharynx20. Thus, to study the transition from asymptomatic carriage to invasive disease following IAV infection, a model was established in which mice were intranasally administered biofilm-grown pneumococci followed by IAV infection of the nasopharynx21,22. Viral infection of the upper airway led to changes in the host environment that led to the dispersal of pneumococci from biofilms and their spread to the lower airways21. These dispersed bacteria had upregulated expression of virulence factors important for infection, converting them from colonizers to pathogens21. These observations highlight the complex interaction between the virus, host, and bacteria and demonstrate that the changes to the host triggered by viral infection have a direct impact on the pneumococcal behavior, which, in turn, alters the course of bacterial infection. However, this model fails to recapitulate the severe signs of illness observed in humans, likely because the virus is limited to the nasal cavity, and the systemic effects of viral infection on host immunity and lung damage are not recapitulated.
We recently established a model that incorporates the complex interaction between the host and pathogens but also more closely mimics the disease severity observed in humans23. In this model, mice are first infected intranasally with biofilm-grown pneumococci to establish asymptomatic carriage, followed by IAV infection of both the nasopharynx and lungs. This resulted in bacterial dissemination to the lungs, pulmonary inflammation, and illness that progressed to lethality in a fraction of young mice23. This previous study demonstrated that both viral and bacterial infection altered host defense: viral infection promoted bacterial dissemination, and prior bacterial colonization impaired the ability of the host to control pulmonary IAV levels23. Examining the immune response revealed that IAV infection diminished the antibacterial activity of neutrophils, while bacterial colonization blunted the type I interferon response critical to antiviral defense23. Importantly, this model reproduced the susceptibility of aging. Compared to young mice, old mice displayed signs of disease earlier, showed more severe clinical illness, and succumbed to infection more frequently23. The work presented in this manuscript shows that the degree of disease is also dependent on the bacterial strain, because invasive pneumococcal strains display more efficient dissemination upon IAV infection, show more overt signs of pulmonary inflammation, and result in accelerated rates of disease compared to non-invasive strains. Thus, this S. pneumoniae/IAV co-infection model permits the detailed examination of both pathogen and host factors and is well-suited for studying immune responses to polymicrobial infections at the different phases of disease progression.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-Aminobenzoic acid&#160;</td>
			<td>Fisher</td>
			<td>AAA1267318</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>96-well round bottom plates</td>
			<td>Greiner Bio-One</td>
			<td>650101</td>
			<td></td>
		</tr>
		<tr>
			<td>100 &#181;m Filters</td>
			<td>Fisher</td>
			<td>07-201-432</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenine</td>
			<td>Fisher</td>
			<td>AC147440250</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>Avicel</td>
			<td>Fisher</td>
			<td>501785325</td>
			<td>Microcyrstalline cellulose&#160;</td>
		</tr>
		<tr>
			<td>BD Cytofix Fixation Buffer&#160;</td>
			<td>Fisher</td>
			<td>BDB554655</td>
			<td>Fixation Buffer</td>
		</tr>
		<tr>
			<td>BD Fortessa</td>
			<td></td>
			<td></td>
			<td>Flow cytometer&#160;</td>
		</tr>
		<tr>
			<td>BD Intramedic Polyethylene Tubing&#160;</td>
			<td>Fisher</td>
			<td>427410</td>
			<td>Tubing for nasal lavage</td>
		</tr>
		<tr>
			<td>BD&#160;Disposable Syringes with Luer-Lok Tips (1 mL)</td>
			<td>Fisher</td>
			<td>14-823-30</td>
			<td></td>
		</tr>
		<tr>
			<td>BD&#160;Microtainer Capillary Blood Collector and BD Microgard Closure</td>
			<td>Fisher</td>
			<td>02-675-185</td>
			<td>Blood collection tubes</td>
		</tr>
		<tr>
			<td>Beta-Nicotinamide adenine dinucleotide</td>
			<td>Fisher</td>
			<td>AAJ6233703</td>
			<td>Mix IV stock</td>
		</tr>
		<tr>
			<td>Biotin</td>
			<td>Fisher</td>
			<td>AC230090010</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>C57BL/6J mice</td>
			<td>The Jackson Laboratory</td>
			<td>#000644</td>
			<td>Mice used in this study</td>
		</tr>
		<tr>
			<td>Calcium Chloride Anhydrous</td>
			<td>Fisher Chemical</td>
			<td>C77-500</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>CD103 BV 421</td>
			<td>BD Bioscience</td>
			<td>BDB562771</td>
			<td>Clone: M290 DF 1:200</td>
		</tr>
		<tr>
			<td>CD11b APC</td>
			<td>Invitrogen</td>
			<td>50-112-9622</td>
			<td>Clone: M1/70, DF 1:300</td>
		</tr>
		<tr>
			<td>CD11c PE</td>
			<td>BD Bioscience</td>
			<td>BDB565592</td>
			<td>Clone: N418 DF 1:200</td>
		</tr>
		<tr>
			<td>CD3 AF 488</td>
			<td>BD Bioscience</td>
			<td>OB153030</td>
			<td>Clone: 145-2C11 DF 1:200</td>
		</tr>
		<tr>
			<td>CD4 V450</td>
			<td>BD Horizon</td>
			<td>BDB560470</td>
			<td>Clone: RM4.5 DF 1:300</td>
		</tr>
		<tr>
			<td>CD45 APC eF-780</td>
			<td>BD Bioscience</td>
			<td>50-112-9642</td>
			<td>Clone: 30-F11 DF 1:200</td>
		</tr>
		<tr>
			<td>CD45 PE</td>
			<td>Invitrogen</td>
			<td>50-103-70</td>
			<td>Clone: 30-F11 DF 1:200</td>
		</tr>
		<tr>
			<td>CD8&#945; BV 650</td>
			<td>BD Horizon</td>
			<td>BDB563234</td>
			<td>Clone: 53-6.7 DF 1:200</td>
		</tr>
		<tr>
			<td>Choline chloride</td>
			<td>Fisher</td>
			<td>AC110290500</td>
			<td>Final supplement to CDM</td>
		</tr>
		<tr>
			<td>Corning Disposable Vacuum Filter/Storage Systems</td>
			<td>Fisher</td>
			<td>09-761-107</td>
			<td>Filter sterilzation apparatus&#160;</td>
		</tr>
		<tr>
			<td>Corning Tissue Culture Treated T-25 Flasks</td>
			<td>Fisher</td>
			<td>10-126-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning&#160;Costar Clear Multiple Well Plates</td>
			<td>Fisher</td>
			<td>07-201-590</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning&#160;DMEM With L-Glutamine and 4.5 g/L Glucose; Without Sodium Pyruvate</td>
			<td>Fisher</td>
			<td>MT10017CM</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyanocobalamin</td>
			<td>Fisher</td>
			<td>AC405925000</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>D39</td>
			<td>National Collection of Type Culture (NCTC)</td>
			<td>NCTC 7466</td>
			<td>Streptococcus pneumoniae strain</td>
		</tr>
		<tr>
			<td>D-Alanine</td>
			<td>Fisher</td>
			<td>AAA1023114</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>D-Calcium pantothenate</td>
			<td>Fisher</td>
			<td>AC243301000</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>Dextrose</td>
			<td>Fisher Chemical</td>
			<td>D16-500</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>Dnase&#160;</td>
			<td>Worthington Biochemical&#160;</td>
			<td>LS002147</td>
			<td></td>
		</tr>
		<tr>
			<td>Eagles Minimum Essential Medium</td>
			<td>ATCC</td>
			<td>30-2003</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>VWR</td>
			<td>BDH4616-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>EF3030</td>
			<td>Center for Disease Control and Prevention&#160;</td>
			<td>Available via the isolate bank request</td>
			<td>Streptococcus pneumoniae strain, request using strain name</td>
		</tr>
		<tr>
			<td>F480 PE Cy7</td>
			<td>BD Bioscience</td>
			<td>50-112-9713</td>
			<td>Clone: BMB DF 1:200</td>
		</tr>
		<tr>
			<td>Falcon 50 mL Conical Centrifuge Tubes</td>
			<td>Fisher</td>
			<td>14-432-22</td>
			<td>50 mL round bottom tube</td>
		</tr>
		<tr>
			<td>Falcon&#160;Round-Bottom Polypropylene Test Tubes With Cap</td>
			<td>Fisher</td>
			<td>14-959-11B</td>
			<td>15 mL round bottom tube</td>
		</tr>
		<tr>
			<td>Falcon&#160;Round-Bottom Polystyrene Test Tubes (5 mL)</td>
			<td>Fisher</td>
			<td>14-959-5</td>
			<td>FACS tubes&#160;</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Thermofisher</td>
			<td>10437-028</td>
			<td></td>
		</tr>
		<tr>
			<td>Ferric Nitrate Nonahydrate</td>
			<td>Fisher</td>
			<td>I110-100</td>
			<td>Mix III stock</td>
		</tr>
		<tr>
			<td>Fisherbrand Delicate Dissecting Scissors</td>
			<td>Fisher</td>
			<td>08-951-5</td>
			<td>Instruments used for harvest</td>
		</tr>
		<tr>
			<td>Fisherbrand Disposable Inoculating Loops&#160;</td>
			<td>Fisher</td>
			<td>22-363-602</td>
			<td>Inoculating loops&#160;</td>
		</tr>
		<tr>
			<td>Fisherbrand Dissecting Tissue Forceps</td>
			<td>Fisher</td>
			<td>13-812-38</td>
			<td>Forceps for harvest</td>
		</tr>
		<tr>
			<td>Fisherbrand Premium Microcentrifuge Tubes: 1.5 mL</td>
			<td>Fisher</td>
			<td>05-408-137</td>
			<td>Micocentrifuge tubes</td>
		</tr>
		<tr>
			<td>Fisherbrand&#160;Sterile Syringes for Single Use (10 mL)</td>
			<td>Fisher</td>
			<td>14-955-459</td>
			<td></td>
		</tr>
		<tr>
			<td>Folic Acid</td>
			<td>Fisher</td>
			<td>AC216630500</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>Gibco RPMI 1640 (ATCC)</td>
			<td>Fisher</td>
			<td>A1049101</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;DPBS, no calcium, no magnesium</td>
			<td>Fisher</td>
			<td>14190250</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;HBSS, calcium, magnesium, no phenol red</td>
			<td>Fisher</td>
			<td>14025134</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;MEM (Temin&#39;s modification) (2x), no phenol red</td>
			<td>Fisher</td>
			<td>11-935-046</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;Penicillin-Streptomycin (10,000 U/mL)</td>
			<td>Fisher</td>
			<td>15-140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;Trypan Blue Solution, 0.4%</td>
			<td>Fisher</td>
			<td>15-250-061</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibco&#160;Trypsin-EDTA (0.25%), phenol red</td>
			<td>Fisher</td>
			<td>25-200-056</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol (Certified ACS)</td>
			<td>Fisher</td>
			<td>G33-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Fisher</td>
			<td>AA3643530</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>Guanine</td>
			<td>Fisher</td>
			<td>AAA1202414</td>
			<td>Mix II stock</td>
		</tr>
		<tr>
			<td>Invitrogen UltraComp eBeads Compensation Beads</td>
			<td>Fisher</td>
			<td>50-112-9040</td>
			<td></td>
		</tr>
		<tr>
			<td>Iron (II) sulfate heptahydrate</td>
			<td>Fisher</td>
			<td>AAA1517836</td>
			<td>Mix III stock</td>
		</tr>
		<tr>
			<td>L-Alanine</td>
			<td>Fisher</td>
			<td>AAJ6027918</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Arginine</td>
			<td>Fisher</td>
			<td>AAA1573814</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Asparagine</td>
			<td>Fisher</td>
			<td>AAB2147322</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Aspartic acid&#160;</td>
			<td>Fisher</td>
			<td>AAA1352022</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Cysteine</td>
			<td>Fisher</td>
			<td>AAA1043518</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Cysteine hydrochloride monohydrate</td>
			<td>Fisher</td>
			<td>AAA1038914</td>
			<td>Final supplement to CDM</td>
		</tr>
		<tr>
			<td>L-Cystine</td>
			<td>Fisher</td>
			<td>AAA1376218</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Glutamic acid&#160;</td>
			<td>Fisher</td>
			<td>AC156211000</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Fisher</td>
			<td>O2956-100</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Histidine</td>
			<td>Fisher</td>
			<td>AC166150250</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>LIFE TECHNOLOGIES LIVE/DEAD Fixable Blue Dead Cell Stain Kit, for UV excitation</td>
			<td>Invitrogen</td>
			<td>50-112-1524</td>
			<td>Clone: N/A DF 1:500</td>
		</tr>
		<tr>
			<td>L-Isoleucine</td>
			<td>Fisher</td>
			<td>AC166170250</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Leucine</td>
			<td>Fisher</td>
			<td>BP385-100</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Lysine</td>
			<td>Fisher</td>
			<td>AAJ6222514</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Methionine</td>
			<td>Fisher</td>
			<td>AAA1031822</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>Low endotoxin BSA&#160;</td>
			<td>Sigma Aldrich</td>
			<td>A1470-10G</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Phenylalanine</td>
			<td>Fisher</td>
			<td>AAA1323814</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Proline</td>
			<td>Fisher</td>
			<td>AAA1019922</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Serine</td>
			<td>Fisher</td>
			<td>AC132660250</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Threonine</td>
			<td>Fisher</td>
			<td>AC138930250</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Tryptophan</td>
			<td>Fisher</td>
			<td>AAA1023014</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>L-Valine</td>
			<td>Fisher</td>
			<td>AAA1272014</td>
			<td>Amino acid stock</td>
		</tr>
		<tr>
			<td>Ly6C BV 605</td>
			<td>BD Bioscience</td>
			<td>BDB563011</td>
			<td>Clone: AL-21 DF 1:300</td>
		</tr>
		<tr>
			<td>Ly6G AF 488&#160;</td>
			<td>Biolegend</td>
			<td>NC1102120</td>
			<td>Clone: IA8, DF 1:300</td>
		</tr>
		<tr>
			<td>Madin-Darby Canine Kidney (MDCK) cells&#160;</td>
			<td>American Type Culture Collection (ATCC)</td>
			<td>CCL-34</td>
			<td>MDCK cell line for PFU analuysis&#160;</td>
		</tr>
		<tr>
			<td>Magnesium Sulfate 7-Hydrate</td>
			<td>Fisher</td>
			<td>60-019-68</td>
			<td>CDM starter stock</td>
		</tr>
		<tr>
			<td>Manganese Sulfate</td>
			<td>Fisher</td>
			<td>M113-500</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>MilQ water</td>
			<td></td>
			<td></td>
			<td>Ultra-pure water</td>
		</tr>
		<tr>
			<td>Mouse Fc Block</td>
			<td>BD Bioscience</td>
			<td>BDB553142</td>
			<td>Clone: 2.4G2 DF 1:100</td>
		</tr>
		<tr>
			<td>MWI VETERINARY&#160;PURALUBE VET OINTMENT</td>
			<td>Fisher</td>
			<td>NC1886507</td>
			<td>Eye lubricant for infection</td>
		</tr>
		<tr>
			<td>NCI-H292 mucoepidermoid carcinoma cell line&#160;</td>
			<td>ATCC</td>
			<td>CRL-1848</td>
			<td>H292 lung epithelial cell line for biofilm growth</td>
		</tr>
		<tr>
			<td>Niacinamide</td>
			<td>Fisher</td>
			<td>18-604-792</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>NK 1.1 AF 700</td>
			<td>BD Bioscience</td>
			<td>50-112-4692</td>
			<td>Clone: PK136 DF 1:200</td>
		</tr>
		<tr>
			<td>Oxyrase For Broth 50Ml Bottle 1/Pk</td>
			<td>Fisher</td>
			<td>50-200-5299</td>
			<td>To remove oxygen from liquid cultures</td>
		</tr>
		<tr>
			<td>Paraformaldehyde 4% in PBS</td>
			<td>Thermoscientific</td>
			<td>J19932-K2</td>
			<td></td>
		</tr>
		<tr>
			<td>Pivetal Isoflurane&#160;</td>
			<td>Patterson Veterinary</td>
			<td>07-893-8440</td>
			<td>Isoflurane for anesthesia during infection&#160;</td>
		</tr>
		<tr>
			<td>Potassium Phosphate Dibasic</td>
			<td>Fisher Chemical</td>
			<td>P288-500</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>Potassium Phosphate Monobasic</td>
			<td>Fisher Chemical</td>
			<td>P285-500</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>Pyridoxal hydrochloride&#160;</td>
			<td>Fisher</td>
			<td>AC352710250</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>Pyridoxamine dihydrochloride</td>
			<td>Fisher</td>
			<td>AAJ6267906</td>
			<td>Mix I stock</td>
		</tr>
		<tr>
			<td>Riboflavin</td>
			<td>Fisher</td>
			<td>AC132350250</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>Sodium Acetate</td>
			<td>VWR</td>
			<td>0530-500G</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>Sodium Azide&#160;</td>
			<td>Fisher Bioreagents</td>
			<td>BP922I-500</td>
			<td>For FACS buffer</td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate</td>
			<td>Fisher Chemical</td>
			<td>S233-500</td>
			<td>Starter stock and final supplement to CDM</td>
		</tr>
		<tr>
			<td>Sodium Phosphate Dibasic</td>
			<td>Fisher Chemical</td>
			<td>S374-500</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>Sodium Phosphate Monobasic</td>
			<td>Fisher Chemical</td>
			<td>S369-500</td>
			<td>Starter stock</td>
		</tr>
		<tr>
			<td>TCR APC&#160;</td>
			<td>BD Bioscience</td>
			<td>50-112-8889</td>
			<td>Clone: GL-3 DF 1:200</td>
		</tr>
		<tr>
			<td>TCR&#946; APC-Cy7</td>
			<td>BD Pharmigen</td>
			<td>BDB560656</td>
			<td>Clone: H57-597 DF 1:200</td>
		</tr>
		<tr>
			<td>Thermo Scientific Blood Agar with Gentamicin</td>
			<td>Fisher</td>
			<td>R01227</td>
			<td>Blood agar plates with the antibiotic gentamicin&#160;</td>
		</tr>
		<tr>
			<td>Thermo Scientific&#160;Trypsin, TPCK Treated</td>
			<td>Fisher</td>
			<td>PI20233</td>
			<td></td>
		</tr>
		<tr>
			<td>Thiamine hydrochloride</td>
			<td>Fisher</td>
			<td>AC148991000</td>
			<td>Vitamin stock</td>
		</tr>
		<tr>
			<td>TIGR4</td>
			<td>ATCC</td>
			<td>BAA-334</td>
			<td>Streptococcus pneumoniae strain</td>
		</tr>
		<tr>
			<td>Uracil</td>
			<td>Fisher</td>
			<td>AC157300250</td>
			<td>Mix II stock</td>
		</tr>
		<tr>
			<td>Worthington Biochemical Corporation&#160;Collagenase, Type 2, 1 g</td>
			<td>Fisher</td>
			<td>NC9693955</td>
			<td></td>
		</tr>
	</tbody>
</table>

a mouse model for the transition of streptococcus pneumoniae from colonizer to pathogen upon viral co-infection recapitulates age-exacerbated illness

Streptococcus pneumoniae (pneumococcus) is an asymptomatic colonizer of the nasopharynx in most individuals but can progress to a pulmonary and systemic pathogen upon influenza A virus (IAV) infection. Advanced age enhances host susceptibility to secondary pneumococcal pneumonia and is associated with worsened disease outcomes. The host factors driving those processes are not well defined, in part due to a lack of animal models that reproduce the transition from asymptomatic colonization to severe clinical disease. 
This paper describes a novel mouse model that recreates the transition of pneumococci from asymptomatic carriage to disease upon viral infection. In this model, mice are first intranasally inoculated with biofilm-grown pneumococci to establish asymptomatic carriage, followed by IAV infection of both the nasopharynx and lungs. This results in bacterial dissemination to the lungs, pulmonary inflammation, and obvious signs of illness that can progress to lethality. The degree of disease is dependent on the bacterial strain and host factors. 
Importantly, this model reproduces the susceptibility of aging, because compared to young mice, old mice display more severe clinical illness and succumb to disease more frequently. By separating carriage and disease into distinct steps and providing the opportunity to analyze the genetic variants of both the pathogen and the host, this S. pneumoniae/IAV co-infection model permits the detailed examination of the interactions of an important pathobiont with the host at different phases of disease progression. This model can also serve as an important tool for identifying potential therapeutic targets against secondary pneumococcal pneumonia in susceptible hosts.

Watch this Scientific Journal Video about A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness at JoVE.

A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

This paper describes a novel mouse model for the transition of pneumococcus from an asymptomatic colonizer to a disease-causing pathogen during viral infection. This model can be readily adapted to study polymicrobial and host-pathogen interactions during the different phases of disease progression and across various hosts.

A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

Streptococcus pneumoniae (pneumococcus) is an asymptomatic colonizer of the nasopharynx in most individuals but can progress to a pulmonary and systemic ...

a-mouse-model-for-transition-streptococcus-pneumoniae-from-colonizer

Research

JoVE Journal

Immunology and Infection

2.2K Views.  University at Buffalo School of Medicine. This paper describes a novel mouse model for the transition of pneumococcus from an asymptomatic colonizer to a disease-causing pathogen during viral infection. This model can be readily adapted to study polymicrobial and host-pathogen interactions during the different phases of disease progression and across various hosts. 

Video: A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

Live Cell Imaging of Bacillus subtilis and Streptococcus pneumoniae using Automated Time-lapse Microscopy

During the last few years scientists became increasingly aware that average data obtained from microbial population based experiments are not representative of the behavior, status or phenotype of single cells. Due to this new insight the number of single cell studies rises continuously (for recent reviews see 1,2,3). However, many of the single cell techniques applied do not allow monitoring the development and behavior of one specific single cell in time (e.g. flow cytometry or standard microscopy).
Here, we provide a detailed description of a microscopy method used in several recent studies 4, 5, 6, 7, which allows following and recording (fluorescence of) individual bacterial cells of Bacillus subtilis and Streptococcus pneumoniae through growth and division for many generations. The resulting movies can be used to construct phylogenetic lineage trees by tracing back the history of a single cell within a population that originated from one common ancestor. This time-lapse fluorescence microscopy method cannot only be used to investigate growth, division and differentiation of individual cells, but also to analyze the effect of cell history and ancestry on specific cellular behavior. Furthermore, time-lapse microscopy is ideally suited to examine gene expression dynamics and protein localization during the bacterial cell cycle. The method explains how to prepare the bacterial cells and construct the microscope slide to enable the outgrowth of single cells into a microcolony. In short, single cells are spotted on a semi-solid surface consisting of growth medium supplemented with agarose on which they grow and divide under a fluorescence microscope within a temperature controlled environmental chamber. Images are captured at specific intervals and are later analyzed using the open source software ImageJ.

Live Cell Imaging of Bacillus subtilis and Streptococcus pneumoniae using Automated Time-lapse Microscopy

This protocol provides a step-by-step procedure to monitor single cell behavior of different bacteria in time using automated fluorescence time-lapse microscopy. Furthermore, we provide guidelines how to analyze the microscopy images.

During the last few years scientists became increasingly aware that average data obtained from microbial population based experiments are not ...

Use of the EpiAirway Model for Characterizing Long-term Host-pathogen Interactions

Nontypeable Haemophilus influenzae (NTHi) are human-adapted Gram-negative bacteria that can cause recurrent and chronic infections of the respiratory mucosa 1; 2. To study the mechanisms by which these organisms survive on and inside respiratory tissues, a model in which successful long-term co-culture of bacteria and human cells can be performed is required. We use primary human respiratory epithelial tissues raised to the air-liquid interface, the EpiAirway model (MatTek, Ashland, MA). These are non-immortalized, well-differentiated, 3-dimensional tissues that contain tight junctions, ciliated and nonciliated cells, goblet cells that produce mucin, and retain the ability to produce cytokines in response to infection. 
This biologically relevant in vitro model of the human upper airway can be used in a number of ways; the overall goal of this method is to perform long-term co-culture of EpiAirway tissues with NTHi and quantitate cell-associated and internalized bacteria over time. As well, mucin production and the cytokine profile of the infected co-cultures can be determined. This approach improves upon existing methods in that many current protocols use submerged monolayer or Transwell cultures of human cells, which are not capable of supporting bacterial infections over extended periods3. For example, if an organism can replicate in the overlying media, this can result in unacceptable levels of cytotoxicity and loss of host cells, arresting the experiment. The EpiAirway model allows characterization of long-term host-pathogen interactions. Further, since the source for the EpiAirway is normal human tracheo-bronchial cells rather than an immortalized line, each is an excellent representation of actual human upper respiratory tract tissue, both in structure and in function4.
For this method, the EpiAirway tissues are weaned off of anti-microbial and anti-fungal compounds for 2 days prior to delivery, and all procedures are performed under antibiotic-free conditions. This necessitates special considerations, since both bacteria and primary human tissues are used in the same biosafety cabinet, and are co-cultured for extended periods.

This method allows characterization of extended bacterial co-culture with EpiAirways, primary human respiratory epithelial tissue grown at the air-liquid interface, a biologically relevant in vitro model. The approach can be used with any microbe that is amenable to long-term co-culture.

Nontypeable Haemophilus influenzae  (NTHi) are human-adapted Gram-negative bacteria that can cause recurrent and chronic infections of the respiratory ...

The Citrobacter rodentium Mouse Model: Studying Pathogen and Host Contributions to Infectious Colitis

This protocol outlines the steps required to produce a robust model of infectious disease and colitis, as well as the methods used to characterize Citrobacter rodentium infection in mice. C. rodentium is a gram negative, murine specific bacterial pathogen that is closely related to the clinically important human pathogens enteropathogenic E. coli and enterohemorrhagic E. coli. Upon infection with C. rodentium, immunocompetent mice suffer from modest and transient weight loss and diarrhea. Histologically, intestinal crypt elongation, immune cell infiltration, and goblet cell depletion are observed. Clearance of infection is achieved after 3 to 4 weeks. Measurement of intestinal epithelial barrier integrity, bacterial load, and histological damage at different time points after infection, allow the characterization of mouse strains susceptible to infection.
The virulence mechanisms by which bacterial pathogens colonize the intestinal tract of their hosts, as well as specific host responses that defend against such infections are poorly understood. Therefore the C. rodentium model of enteric bacterial infection serves as a valuable tool to aid in our understanding of these processes. Enteric bacteria have also been linked to Inflammatory Bowel Diseases (IBDs). It has been hypothesized that the maladaptive chronic inflammatory responses seen in IBD patients develop in genetically susceptible individuals following abnormal exposure of the intestinal mucosal immune system to enteric bacteria. Therefore, the study of models of infectious colitis offers significant potential for defining potentially pathogenic host responses to enteric bacteria. C. rodentium induced colitis is one such rare model that allows for the analysis of host responses to enteric bacteria, furthering our understanding of potential mechanisms of IBD pathogenesis; essential in the development of novel preventative and therapeutic treatments.

The Citrobacter rodentium Mouse Model: Studying Pathogen and Host Contributions to Infectious Colitis

Citrobacter rodentium infection provides a valuable model to study enteric bacterial infections as well as host immune responses and colitis in mice. This protocol outlines the measurement of barrier integrity, pathogen load and histological damage allowing for the thorough characterization of pathogen and host contributions to murine infectious colitis.

This protocol  outlines the steps required to produce a robust model of infectious disease and  colitis, as well as the methods used to characterize ...

Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae

Nasopharyngeal colonization by Streptococcus pneumoniae is a prerequisite to invasion to the lungs or bloodstream1. This organism is capable of colonizing the mucosal surface of the nasopharynx, where it can reside, multiply and eventually overcome host defences to invade to other tissues of the host. Establishment of an infection in the normally lower respiratory tract results in pneumonia. Alternatively, the bacteria can disseminate into the bloodstream causing bacteraemia, which is associated with high mortality rates2, or else lead directly to the development of pneumococcal meningitis. Understanding the kinetics of, and immune responses to, nasopharyngeal colonization is an important aspect of S. pneumoniae infection models.
Our mouse model of intranasal colonization is adapted from human models3 and has been used by multiple research groups in the study of host-pathogen responses in the nasopharynx4-7. In the first part of the model, we use a clinical isolate of S. pneumoniae to establish a self-limiting bacterial colonization that is similar to carriage events in human adults. The procedure detailed herein involves preparation of a bacterial inoculum, followed by the establishment of a colonization event through delivery of the inoculum via an intranasal route of administration. Resident macrophages are the predominant cell type in the nasopharynx during the steady state. Typically, there are few lymphocytes present in uninfected mice8, however mucosal colonization will lead to low- to high-grade inflammation (depending on the virulence of the bacterial species and strain) that will result in an immune response and the subsequent recruitment of host immune cells. These cells can be isolated by a lavage of the tracheal contents through the nares, and correlated to the density of colonization bacteria to better understand the kinetics of the infection.

Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae

Colonization of the murine nasopharynx with Streptococcus pneumoniae and the subsequent extraction of adherent or recruited cells is described. This technique involves flushing the nasopharynx and collection of the fluid through the nares and is adaptable for various readouts, including differential cell quantification and analysis of mRNA expression in situ.

Nasopharyngeal colonization by Streptococcus pneumoniae is a prerequisite to invasion to the lungs or bloodstream1. This organism is capable of colonizing ...

Monitoring Changes in Membrane Polarity, Membrane Integrity, and Intracellular Ion Concentrations in Streptococcus pneumoniae Using Fluorescent Dyes

Membrane depolarization and ion fluxes are events that have been studied extensively in biological systems due to their ability to profoundly impact cellular functions, including energetics and signal transductions. While both fluorescent and electrophysiological methods, including electrode usage and patch-clamping, have been well developed for measuring these events in eukaryotic cells, methodology for measuring similar events in microorganisms have proven more challenging to develop given their small size in combination with the more complex outer surface of bacteria shielding the membrane. During our studies of death-initiation in Streptococcus pneumoniae (pneumococcus), we wanted to elucidate the role of membrane events, including changes in polarity, integrity, and intracellular ion concentrations. Searching the literature, we found that very few studies exist. Other investigators had monitored radioisotope uptake or equilibrium to measure ion fluxes and membrane potential and a limited number of studies, mostly in Gram-negative organisms, had seen some success using carbocyanine or oxonol fluorescent dyes to measure membrane potential, or loading bacteria with cell-permeant acetoxymethyl (AM) ester versions of ion-sensitive fluorescent indicator dyes. We therefore established and optimized protocols for measuring membrane potential, rupture, and ion-transport in the Gram-positive organism S. pneumoniae. We developed protocols using the bis-oxonol dye DiBAC4(3) and the cell-impermeant dye propidium iodide to measure membrane depolarization and rupture, respectively, as well as methods to optimally load the pneumococci with the AM esters of the ratiometric dyes Fura-2, PBFI, and BCECF to detect changes in intracellular concentrations of Ca2+, K+, and H+, respectively, using a fluorescence-detection plate reader. These protocols are the first of their kind for the pneumococcus and the majority of these dyes have not been used in any other bacterial species. Though our protocols have been optimized for S. pneumoniae, we believe these approaches should form an excellent starting-point for similar studies in other bacterial species.

Monitoring Changes in Membrane Polarity, Membrane Integrity, and Intracellular Ion Concentrations in Streptococcus pneumoniae Using Fluorescent Dyes

Unlike that seen for eukaryotes, there is a paucity of studies that detail membrane depolarization and ion concentration changes in bacteria, primarily as their small size makes conventional methods of measurement difficult. Here, we detail protocols for monitoring such events in the significant Gram-positive pathogen Streptococcus pneumoniae utilizing fluorescence techniques.

Membrane depolarization and ion fluxes are events that have been studied extensively in biological systems due to their ability to profoundly impact ...

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal epidemiology, capsular serotyping can provide useful information for vaccine efficacy and impact studies.&#160;The Quellung reaction is the gold standard method for pneumococcal capsular serotyping. The method involves testing a pneumococcal cell suspension with pooled and specific antisera directed against the capsular polysaccharide. The antigen-antibody reactions are observed microscopically. The protocol has three main steps: 1) preparation of a bacterial cell suspension, 2) mixing of cells and antisera on a glass slide, and 3) reading the Quellung reaction using a microscope. The Quellung reaction is reasonably simple to perform and can be applied wherever a suitable microscope and antisera are available.

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction

The Quellung reaction is the gold standard technique for serotyping Streptococcus pneumoniae. This technique utilizes a microscope and specific pneumococcal antisera and is commonly used in reference and research laboratories worldwide.

There are over 90 different capsular serotypes of Streptococcus pneumoniae (the pneumococcus). As well as being a tool for understanding pneumococcal ...

A Mouse Model for Pathogen-induced Chronic Inflammation at Local and Systemic Sites

Chronic inflammation is a major driver of pathological tissue damage and a unifying characteristic of many chronic diseases in humans including neoplastic, autoimmune, and chronic inflammatory diseases. Emerging evidence implicates pathogen-induced chronic inflammation in the development and progression of chronic diseases with a wide variety of clinical manifestations. Due to the complex and multifactorial etiology of chronic disease, designing experiments for proof of causality and the establishment of mechanistic links is nearly impossible in humans. An advantage of using animal models is that both genetic and environmental factors that may influence the course of a particular disease can be controlled. Thus, designing relevant animal models of infection represents a key step in identifying host and pathogen specific mechanisms that contribute to chronic inflammation.
Here we describe a mouse model of pathogen-induced chronic inflammation at local and systemic sites following infection with the oral pathogen Porphyromonas gingivalis, a bacterium closely associated with human periodontal disease. Oral infection of specific-pathogen free mice induces a local inflammatory response resulting in destruction of tooth supporting alveolar bone, a hallmark of periodontal disease. In an established mouse model of atherosclerosis, infection with P. gingivalis accelerates inflammatory plaque deposition within the aortic sinus and innominate artery, accompanied by activation of the vascular endothelium, an increased immune cell infiltrate, and elevated expression of inflammatory mediators within lesions. We detail methodologies for the assessment of inflammation at local and systemic sites. The use of transgenic mice and defined bacterial mutants makes this model particularly suitable for identifying both host and microbial factors involved in the initiation, progression, and outcome of disease. Additionally, the model can be used to screen for novel therapeutic strategies, including vaccination and pharmacological intervention.

Animal models have proven to be invaluable tools in defining host and pathogen specific mechanisms that contribute to the development of chronic inflammation. Here we describe a mouse model of oral infection with the human pathogen Porphyromonas gingivalis and detail methodologies to assess the progression of inflammation at local and systemic sites.

Chronic inflammation is a major driver of pathological tissue damage and a unifying characteristic of many chronic diseases in humans including ...

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major cause of morbidity and mortality world-wide. Current vaccines target the pneumococcal capsule, and there are over 90 capsular serotypes. Serotyping pneumococcal isolates is therefore important for assessing the impact of vaccination programs and for epidemiological purposes. The World Health Organization has recommended latex agglutination as an alternative method to the &#8216;gold standard&#8217; Quellung test for serotyping pneumococci. Latex agglutination is a relatively simple, quick and inexpensive method; and is therefore suitable for resource-poor settings as well as laboratories with high-volume workloads. Latex agglutination reagents can be prepared in-house utilizing commercially-sourced antibodies that are passively attached to latex particles. This manuscript describes a method of production and quality control of latex agglutination reagents, and details a sequential testing approach which is time- and cost-effective. 
This method of production and quality control may also be suitable for other testing purposes.

Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination

Latex agglutination testing is a simple, rapid and inexpensive method for serotyping Streptococcus pneumoniae, and has also been widely applied in diagnostic microbiology. This manuscript describes the in-house production of latex agglutination reagents, quality control procedures and the application of this technique to pneumococcal serotyping.

Latex agglutination reagents are widely used in microbial diagnosis, identification and serotyping. Streptococcus pneumoniae (the pneumococcus) is a major ...

An In Vitro Model for Measuring Immune Responses to Malaria in the Context of HIV Co-infection

Malaria and HIV co-infection is a growing health priority. However, most research on malaria or HIV currently focuses on each infection individually. Although understanding the disease dynamics for each of these pathogens independently is vital, it is also important that the interactions between these pathogens are investigated and understood. 
We have developed a versatile in vitro model of HIV-malaria co-infection to study host immune responses to malaria in the context of HIV infection. Our model allows the study of secreted factors in cellular supernatants, cell surface and intracellular protein markers, as well as RNA expression levels. The experimental design and methods used limit variability and promote data reliability and reproducibility. 
All pathogens used in this model are natural human pathogens (Plasmodium falciparum and HIV-1), and all infected cells are naturally infected and used fresh. We use human erythrocytes parasitized with P. falciparum and maintained in continuous in vitro culture. We obtain freshly isolated peripheral blood mononuclear cells from chronically HIV-infected volunteers. Every condition used has an appropriate control (P. falciparum parasitized vs. normal erythrocytes), and every HIV-infected donor has an HIV uninfected control, from which cells are harvested on the same day. This model provides a realistic environment to study the interactions between malaria parasites and human immune cells in the context of HIV infection.

An In Vitro Model for Measuring Immune Responses to Malaria in the Context of HIV Co-infection

Human co-infection is difficult to replicate in vitro. However, human malaria parasites can readily be cultured in vitro, as can freshly isolated human peripheral blood mononuclear cells naturally infected with HIV. This provides an excellent model for studying early immune responses to malaria parasites in the context of HIV co-infection.

Malaria and HIV co-infection is a growing health priority. However, most research on malaria or HIV currently focuses on each infection individually. ...