Question

For my Microbiology Lab we are instructed to design an experiment to test for food pathogens. The food that we have selected is sushi in our cafeteria versus the sushi from a restaraunt. We are in need of help for the methods of how to perform this experiment. We are able to request inoculating loops, incubators, multiple types of media, etc. We are considering testing for the presence of: Salmonella, listeria, Staph. aureus, and Bacillus cereus. Help on this procedure!

Answer 1

All these bacteria can be grown on macConkey and blood agar medua.

The food is intially plated on blood agar and macConkey media. Salmonella is gram negative bacteria whereas all others are gram positive. Only staph aureus is cocci. All others are bacilli. Except salmonella all bacteria shows hemolysis on blood agar. Except salmonella all others ferment lactose and show pink colonies. Only listeria is anaerobic, all others grow well in aerobic environment. Only staph aureus is non motile. All others are motile. Only bacillus cereus form spores, all others are non sporting.

Salmonella is oxidase negative.

You can perform biochemical tests on the isolated colonies and can identify the genus of the bacteria grown.

Tests like oxidase, catalase, indole, urease, citrate, coagulase can be employed to identify the bacteria.