K2 pts) Which of the following best describes Salmonella? A Usually a human path
ID: 253974 • Letter: K
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K2 pts) Which of the following best describes Salmonella? A Usually a human pathogen B. Sometimes a human pathogen C. Never a human pathogen (2 pts) Which of the following best describes Shigella? A. Usually a human pathogen B. Sometimes a human pathogen C. Never a human pathogen (2 pts) Define coliform (2 pts) Because there are so many bacteria commonly found in feces, what must be used in order. to isolate pathogens? (2 pts) How are enteric pathogens biochemically different from most other enteric bacteria?Explanation / Answer
Salmonella is an enteric bacteria which are usually pathogens.
They are associated with typhoid fever and some of the species also cause non typhoidal infections resulting in disorders of the GI tract and also septic shock
Shigella is also an enteric pathogen. They cause dysentery and had been a major cause of child death in African and Asian continents
answer for both the question is they are usually human pathogens
They are also found to affect primates
Coliforms are defined as gram negative rod shaped bacteria which are motile or non-motile and are non sporing and lactose fermenting. These bacteria are predominantly found in the gastrointestinal tract and are found to enter the bacteria through food. Thus they are also referred to as enteric bacteria. Some coliforms like E coli are commensals and are found in the intestinal tract even in a healthy individual.
Lactose fermentation is the major aspect that is used in general to differentiate the enteric bacteria. Thus in order to identify pathogens from feces serial dilutions of the feces can be plated on to a Mac-Conkey agar and then the resulting colonies can further be subtyped to identify the specific pathogen.
The enteric pathogens are biochemically diferentiated using a set of tests termed IMViC test. Indole test, Methyl red-Voges Proskauer test, Citrate test.
In the Indole test the pathogen to be tested will be inoculated into a peptone broth and then Kovacs reagent will be used to detect the production of Indole.
In the MR-VP test the pathogens grown in an MRVP broth will be separately assessed for acid fermentation reaction using Methyl red a pH indicator and a mixture of alpha naphthol and potassium hydroxide to detect acetoin formation.
In the citrate test the bactria will be grown on a Simmons citrate agar which has bromothymol blue as an indicator.
growth in the medium with colored colonies indicate citrate fermentation and gas bubbles if formed during the reaction will also be detected with cracks on the agar medium
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