#microbiological lab testing

Today consumers become very sensitive to their food quality.  Their growing demand for fresh and appropriate forms of foodstuffs leads to the advancement of safety practices in the food industry. Day by day outbreaks of foodborne diseases across countries rise up resulting in mounting concern and intensive investigation of foodborne pathogens. This is why the demand of for the microbiological testing of food products is fast increasing.

What's the purpose of Microbiological Testing?

The purpose of microbiological testing is to identify and contain harmful microbes that damage foods, and ensure protection from foodborne diseases. It means that the experts at microbiological testing lab must establish a thorough testing procedure to recognize all the possible threats that could lead to one of the two results: pathogen detected or not detected.

Prior to carrying out a microbiology test, the professionals need to know the importance, purpose, and primary expectations underlying the test along with the expected certainty of identifying an issue, and possible results, which may result from the test.

As a result, it will help know the sampling procedure to be conducted, the kind of samples to be gathered, the specific test method to be used, and appropriate actions to be taken before and after the test results are got.

Reasons for a Microbiology Test

The common reasons for microbiological testing are to:

Spot risk factors

Meet precise specifications for raw material, intermediate, and finished product

Process verification

Confirm that all regulatory guidelines are practiced properly

Why Microbiological Testing?

Microbiological testing is a component of the food safety system even though it cannot guarantee 100% of the product safety. Microbiological testing is a requirement and key part that must be performed to ensure food safety. It can outline essential information about a manufacturing process, processing environment, and a specific product batch. With it, one can know whether a sampling or testing procedure is properly designed and completed based on regulatory guidelines or not.

The microbiological testing mostly ensures that no pathogens are identified from the sample and/or, comprehend the levels of sensitivity and assurance given by the testing procedures and sampling plans used.

Common Test Methods

Various technologies are being used for the detection and verification of microbes. Some of the popular types are described below. Have a look at them.

1. Culture Media

2. Immunoassay

3. Polymerase chain reaction

Culture Media

A kind of medium which is used in microbial laboratory to identify various types of microorganisms is known as culturing or growing. A culture medium generally comprises of some nutrients to augment microbial growth.

Today the culture techniques witness low popularity because the modern developments of the testing methods and validation studies already confirmed that cultural methods aren't appropriate for all food groups.

Immunoassay

Immunoassay is considered as a microbiological test commonly used to measure the concentration of a macromolecule present in a solution by using an antibody or immunoglobulin. The found macromolecule from an immunoassay method is more like a protein and is broadly coined as an "analyte".

Such analytes in biological liquids are frequently measured following immunoassay test methods for different purposes. Enzyme-Linked ImmunoSorbent Assay (ELISA) i.e. “pregnancy test” or “dipstick” type method) is among the most commercially accessible immunoassay types.

Polymerase Chain Reaction (PCR)

Polymerase Chain Reaction (PCR) is the latest and revolutionary method developed during 1983. Presently PCR is used in medical and biological research laboratories as a normal and an essential technique for many applications. A PCR test identifies pieces of DNA or RNA that are likely unique to the target microbe.

Water contamination is one of the most serious problems come to our notice every day. Microbiological analysis by a reputable microbial laboratory is considered an effective way to check the contaminated water. The laboratory undertakes different test methods specifically designed for water and Environment.

Water generally gets contaminated by potential pathogens, viruses, or parasites. Instead of conducting separate tests for each of the microorganisms, microbiologists having experience in water and environment testing go for indicator organisms that are always available with enteric pathogens and viruses.

Coliforms & Other Indicator Organisms

Coliforms are bacteria found in the digestive tracts of animals including humans. They are found in faecal matter. Coliforms ferment lactose with a production of gas within 48 hours at either 35ºC or 44/44.5ºC. Such traits enable it for easy isolation, detection, and enumeration in the microbiological lab and are the gold standard for microbial water testing.

  They are found at the time enteric pathogens or viruses are spotted during water testing. But keep in mind a high 'total coliform' does not always indicate faecal contamination. It further requires test the faecal coliforms to from coliforms present in the environment.

However, a high 'total coliform' count doesn't necessarily mean faecal contamination and requires a second step to identify the faecal coliforms from coliforms found in the environment. Enterobacter, Escherichia, and Klebsiella are the faecal coliforms, Serratiaand Citrobacterare present in soil and plants.

Microbiologists make sure of faecal contamination upon finding faecal streptococci/Enterococci. As compared to thermotolerant or total coliforms, faecal streptococci can exist in the environment longer and also are highly resistant to drying. This is why it is easier to isolate faecal streptococci from water which has few or no thermotolerant coliforms.

Faecal streptococci are mostly detected by the reduction of a dye or the hydrolysis of aesculin. Using traditional methods might produce "false positives," and further confirmatory tests are required then.

  Rapid Methods: Using the latest technology, eminent Microbiological Lab Testing can produce results within 24 hours. Acolourimetric ONPG assay is used to detect coliforms whereas a fluorescence MUG assay is used for E. coli.

Membrane filtration: For analysis of water, a typical membrane filtration method is carried out by passing a specific volume of water through a sterile membrane filter with a pore size small enough to preserve bacterial cells. After that the filter is transmitted to the surface of an agar plate or something like an absorbent pad, which is saturated with an appropriate selective medium and incubated. Colonies are also permitted to grow on the filter surface and can be counted and tested directly.

The membrane filtration methods are quick and simple to perform. The methods need little incubator space and manage large volumes of water when required. For decades, they are the popular methods for the microbiological examination of water for indicator organisms.

Culture media: For the detection of indicator organisms in water by membrane filtration methods, much selective media have been developed. Most popular media for coliforms and E. coli are membrane lactose glucuronide agar, membrane lauryl sulphate broth or agar and MI agar and broth

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Membrane-Enterococcus Indoxyl-ß-D-Glucoside Agar (mEI) and membrane enterococcus agar (mEA) can be utilized for detection and enumeration of enterococci. On the other hand, tryptosesulphitecycloserine agar sans egg yolk is implemented to culture Clostridium perfringens on membrane filters. Using Pseudomonas agar, one kind of membrane filtration method detect Pseudomonas aeruginosa.

Traditional culture: Procedures using pour and spread plate count ways are not so sensitive to detect pathogens and indicator organisms in water. However, they are used for enumerating heterotrophic bacteria. Methods that are effective for testing a larger volume of water are essential. Most probable number is a kind of technique had been widely used for many years. With it, volumes of the water sample are mixed to a series of tubes holding differential media and incubated.

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