Name: Micro-Colony Forming Unit Assay to Quantify Mycobacteria
Uploaded: 2023-07-28T13:10:00
Description: Watch this Scientific Journal Video about Micro-Colony Forming Unit Assay to Quantify Mycobacteria at JoVE.com

micro-colony forming unit assay to quantify mycobacteria

Accélération de la détermination de la tuberculose à l’aide de la méthode micro-UFC

Tuberculosis (TB) is the leading cause of death worldwide by a single infectious agent, bacterium Mycobacterium tuberculosis (M.tb), killing more people than any other pathogen. In 2021, TB was responsible for 1.6 million deaths and was surpassed by COVID-19 during the 2019-2021 pandemic1. Moreover, according to the World Health Organization&#180;s global TB report of 2022, the COVID-19 pandemic was responsible for an increase in new TB cases. The WHO also reports large drops in the number of people diagnosed with TB during this period, which could increase further the number of TB cases1.
The Bacillus Calmette-Gu&#233;rin (BCG) is a live-attenuated strain of the pathogenic Mycobacterium bovis, used for the first time as a vaccine more than 100 years ago. This is the only vaccine against TB and is the oldest licensed vaccine in the world still in use2,3. Currently, there are 12 vaccines in different phases of clinical trials4, and dozens of vaccines are under pre-clinical development5,6. Pre-clinical assessment of vaccines against TB includes the evaluation of the safety and immunogenicity7, which can be obtained in diverse animal models such as zebrafish, mice, guinea pigs, rabbits, cattle, and non-human primates8,9,10. Additionally, assessing the capacity of a vaccine to induce protection against M.tb infection and/or transmission, i.e., the vaccine efficacy, requires an M.tb challenge in vivo5,11. Interestingly, BCG vaccination induces non-specific effects that affect the survival of other bacterial and viral pathogens12,13&#160;through the mechanism of trained immunity14. To quantify the viable bacterial burden in an infected animal, the method of choice is the enumeration of bacterial colonies through the colony-forming units (CFU) assay5,15. CFU is a unit that estimates the number of microorganisms (bacteria or fungi) that form colonies under specific growth conditions. CFUs originate from viable and replicative microorganisms, and the absolute number of living microorganisms within each colony is difficult to estimate. It is uncertain whether a colony has originated from one or more microorganisms. The CFU unit reflects this uncertainty, hence a great variability can be observed in replicates of the same sample. This time-consuming assay requires specialized technicians trained to work in a biosafety level 3 (BSL3) facility, substantial laboratory and incubator space, takes from 4 to 6 weeks to conclude, and is prone to contamination.
In this study, we describe an optimized method for colony enumeration, the micro-CFU (mCFU), and offer a simple and rapid solution to analyze the results15,16,17,18,19,20. The mCFU assay requires tenfold fewer reagents, reduces the incubation period threefold, taking 1 to 2 weeks to conclude, reduces lab space and reagent cost, and minimizes the health and safety risks associated with working with large numbers of M.tb. We propose that this method should be universally adopted for pre-clinical studies of vaccine efficacy determination, ultimately leading to time reduction in the development of vaccines against TB. Finally, this optimized method of CFU enumeration has been used to quantify not only Mycobacteria but also other bacteria, such as Escherichia coli and Ralstonia solanacearum21.

Pleins feux sur l’auteur : Optimiser la détermination des UFC pour une évaluation efficace de l’efficacité du vaccin antituberculeux et une analyse de la présentation de l’antigène 

Dosage d’unités formant des microcolonies pour l’évaluation de l’efficacité des vaccins contre la tuberculose

CFU determination is necessary to measure the efficacy of the immune response against bacteria. However, it is very low throughput and becomes cumbersome and expensive when applied to pathogenic bacteria such as Mycobacterium tuberculosis. This is a significant limitation when we need to test large panels of treatments.The research focuses on tuberculosis and on the assessments of TB vaccines. It explores safety, immunogenicity, and efficacy of vaccines against Mycobacterium tuberculosis. The study presents an optimized method to micro-CFU for enumerating bacterial colonies to assess vaccine efficacy in preclinical studies.This protocol aims to optimize CFU determination by generating results from a small droplet similar to those from a regular Petri dish. Quantifying bacteria viability from such a small sample allows us to analyze thousands of data points using a fraction of the materials and time necessary for the classical method. Our research aims to dissect the antigen presentation machinery and to identify the most relevant antigens to optimize antigen presentation.This will inform us to design and develop better vaccines to improve or replace the current TB vaccine, which is BCG.

Watch this Scientific Journal Video about Micro-Colony Forming Unit Assay to Quantify Mycobacteria at JoVE.com

Micro-Colony Forming Unit Assay to Quantify Mycobacteria  

Dosage d’unités formant des microcolonies pour quantifier les mycobactéries

Pour effectuer une dilution en série à l’aide d’une plaque à puits, placez d’abord les suspensions de Mycobacterium sur les rangées A et E d’une plaque à 96 puits. Ajouter 180 microlitres d’eau déminéralisée dans les puits restants pour le processus de dilution en série. À l’aide d’une pipette à 12 canaux, remettre en suspension les suspensions de la rangée A et transférer 20 microlitres dans la rangée B.Répéter le transfert en suspension pour les rangées B et C jusqu’à ce que la dernière dilution soit atteinte dans la rangée D.Pour le placage par microgouttelettes, utiliser une pipette multicanaux de 0,5 à 10 microlitres avec des pointes minces pour transférer cinq microlitres de chaque rangée de la plaque à 96 puits vers la plaque carrée moyenne solide.Laissez les gouttelettes toucher légèrement la gélose, ce qui assure un transfert correct et minimise la rétention de liquide à l’intérieur de l’embout. Laissez sécher les gouttelettes et fermez la plaque de gélose. Incubez-le à 37 degrés Celsius tout en surveillant la croissance bactérienne.Si vous le souhaitez, placez les plaques de gélose dans un sac en plastique scellé pour éviter qu’elles ne sèchent. Après six à 10 jours d’incubation, vérifiez s’il y a des colonies individuelles visibles à l’œil nu. Placez la plaque sous un microscope inversé en utilisant l’objectif de grossissement le plus faible.Vous pouvez également utiliser un appareil photo pour prendre une photo de la gouttelette et compter manuellement les colonies sur l’ordinateur à l’aide d’ImageJ pour le comptage automatisé des colonies. Le test de l’unité formant des micro-colonies ou micro-UFC a été utilisé pour produire de grandes quantités de données à partir d’une petite quantité de plaques de gélose. L’utilisation de liposomes pour l’administration de saquinavir a augmenté l’efficacité du traitement contre les souches de microbactéries présentant différentes résistances aux médicaments.

Research

JoVE Journal

Medicine

Micro-Colony Forming Unit Assay to Quantify Mycobacteria

Micro-Colony Forming Unit Assay for Efficacy Evaluation of Vaccines Against Tuberculosis

Tuberculosis (TB), the leading cause of death worldwide by an infectious agent, killed 1.6 million people in 2022, only being surpassed by COVID-19 during ...

Recherche

Médecine

Bacillus Calmette-Gu&#233;rin (BCG) Vaccine Production

Production du vaccin contre le bacille de Calmette-Guérin (BCG)

Micro-Colony Forming Unit Counting of Mycobacteria Using Fiji &#40;Image J&#41;

Micro-Colony Forming Unit Counting of Mycobacteria Using Fiji (Image J)  

Comptage d’unités formant des microcolonies de mycobactéries à l’aide de Fidji (Image J)