Thursday, 26 November 2015

TVC, Bacterial endotoxin testing and bacterial identification (Part I of III)

Whenever I find jobs more related to practical microbiology and not so much 'free range' like research is, I happen to meet very defined routines and modes of action. The job requirements for these very straightforward microbiology roles almost always cover three basic aspects: Total Viable Counts (TVC), Bacterial endotoxin testing and Bacterial identification. 

As with basically everything in life, there are numerous different ways of performing these techniques and obtain a successful outcome. But for those who are just starting or aren't so familiar with these techniques, I believe it is of great help if we look into these in more depth.

Total Viable Counts is a test to estimate total numbers of viable (biologically functional) individual microorganisms (usually bacteria) present in a defined volume of sample. This is a technique abundantly used in verifying water and food quality. Different samples demand different parameters as so well explained in [1, 2] and a rigid set of conditions is just not feasible. Media, incubation temperature and even counting procedures change depending on the organism's metabolic requirements and the environment it is coming from. Because a TVC is simply an estimation they are usually interpreted as colony forming units (CFU) per a certain volume or area. A high TVC can tell one about how a vending machine is operating in terms of cooling efficacy, about the maintenance of the water reservoirs, etc.

When performing a TVC it is important to know exactly how to perform a serial dilution (see video for more details on a tenfold gravimetric dilution). Even though a serial dilution is considered to be a very simple and straightforward procedure the tiniest mistake can actually produce surreal results. To overcome counting difficulties a few companies developed tools that can help one on the process. There are plenty of great websites where you can collect important practical info on each tool and procedure techniques. The ones described in RapidMicrobiology are very well developed, especially good for reporting on TVC of food and beverages [4]. 

If you'd like to take a look at practical TVC protocols that are also designed for fungal counting, access here on [3]. 

Next post we will be visiting the Bacterial endotoxin testing as well as the bacterial identification.Stay tuned!

[1] TVC Total viable count, Cheshire Scientific, [], last visited on the 26th of November 2015, last update unknown.

[2] The significance of total viable counts, Watercoolers Europe, [], last visited on the 26th of November 2015, last updated on the 28th of September 2012.

[3] Total viable count with enrichment microbiological procedure, Lubrizol, [file:///C:/Users/mrxil/Downloads/TP-6TV0001_Total_Viable_Count_with_Enrichment.pdf], last visited on the 26th of November 2015, last updated on the 25th of August 2009.

[4] Rapid methods for total viable counts in food and beverages, RapidMicrobiology, [], last visited on the 26th of November 2015, last update unknown.

Video by Shomu's Biology, [].

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