Welcome to the Microbiology Information

Did you know that among the E. coli human pathogens, Verotoxin (Shiga-like toxin) forming strains (VTEC) have gained in importance in recent years. The group of enterohaemorrhagic E. coli (EHEC) with its highly pathogenic serovars 0157:H7, 026, 0103, 0111, 0145, and other strains are of particular concern.

Verotoxins can be classified into two main categories Verotoxin 1 (VT1, SLT1, Stx1) and Verotoxin 2 (VT2, SLT2, Stx2). EHEC strains may produce either VT1 or VT2 only or both VT1 and VT2 simultaneously. EHEC are capable of initiating life threatening illnesses, particularly in those with immune deficiency, young children and the elderly.

Detection of verotoxin is the easist way in which you can determine if the E.coli of interest is a pathogen of real concern.

E.coli is common everywhere with the main sources of infection being contaminated, raw or insufficiently heated foods of animal origin, e.g. meat and dairy products.

The reservoir for EHEC is the feces of cattle, sheep and goats. These microorganisms can enter food during the processing of meat and dairy products if hygienic conditions are inadequate. The drastic increase in the incidence of food infection caused by E. coli 0157 demands reliable and rapid methods of detection. In addition to traditional culture methods, immunological techniques are becoming more useful due to their improved specificity and sensitivity.

Duopath® Verotoxins is an immunological screening test based on the immune flow principle. The Duopath® Verotoxins GLISA test is an immunochromatographic rapid test intended to be used in food-analysing laboratories for the qualitative detection of Verotoxins (Shiga-like toxins) 1 and 2 from Verotoxinogenic E. coli (including E. coli O157:H7) isolated from food enrichments using FDA, USDA or other food enrichment methods.

This test has been validated and received AOAC approval for detection of Verotoxins 1 and 2 from isolated Verotoxin-producing E.coli (including E. coli O157:H7). Duopath® Verotoxin is also intended to be used in clinical laboratories for the qualitative identification of Verotoxins 1 and 2 (Shiga-like toxins 1 and 2) produced by E. coli isolated in cultures derived from clinical stool specimens. The identification aids in the diagnosis of diseases caused by enterohemorrhagic E. coli infections.

Did you know E. coli are divided into four different subgroups. These are A, B1, B2 and D based on a
range of factors including genetics, phenotype and ecology. Group A and B1 strains occur in all vertebrate hosts and in water; Group B2 strains are found in warm-blooded vertebrates with hindgut fermentation; Group D strains are found in warm-blooded vertebrates.

In general, A and B1 strains appear to be generalists, acquired by their hosts from the environment, and which colonise
well but persist poorly. B2 and D strains, which encode the most virulence factors, appear to be acquired from other host animals, colonise poorly but persist well.

The distribution of the subgroups in human populations varies in different parts of the world. The prevalence of subgroups in humans may change with age in population and there appears to be a gender effect.

In water, B1 strains are by far the most dominant, with B2 and D strains rarely found. Interestingly, B1 strains have similar sugar utilisation patterns and optimal growth temperatures whether isolated from water or faeces, while A strains differ in both these characteristics depending on their origin. B1 strains appear to survive the transition to the aquatic environment best, with B2 and D strains surviving relatively poorly in water. Exposure to the aquatic environment appears to select for a subset of group A strains.

The presence of E. coli in ready-to-eat foods is undesirable because it indicates poor hygienic conditions which have lead to contamination or inadequate heat treatment.

Ideally E. coli should not be detected and as such a level of <3 cfu per gram (the limit of the Most Probable Number test) has been given as the satisfactory criteria by regulatory authority around the world in food for this organism. Levels exceeding 100 cfu per gram are unacceptable and indicate a level of contamination which may have introduced pathogens or that pathogens, if present in the food prior to processing, may have survived.

Coliforms and E. Coli No Synopsis Available

The family Enterobacteriaceae are indicators microorganism and includes many bacteria that are found in the human or animal intestinal tract, including human pathogens such as Salmonella and Shigella.

Enterobacteriaceae are useful indicators of hygiene and of post-processing contamination of heat processed foods. Their presence in high numbers (>10000 cfu per gram) in ready-to-eat foods indicates that an unacceptable level of contamination has occurred or there has been underprocessing (e.g. inadequate cooking)

Testing for Enterobacteriaceae is not applicable to fresh fruits and vegetables or foods containing these.

The Microbiology of Safe Food No Synopsis Available