Identification of unknown Lab

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Student: Manoj

Phases Complete 8 of 8 phases.

Phase Resets Phase 1: 0 Phase 2: 0 Phase 3: 0 Phase 4: 0 Phase 5: 0 Phase 6: 0 Phase 7: 0 Phase 8: 0 Phase 9: 0

CASE REPORT: The severe storm had damaged the sewage treatment plant, which was now flooded and leaking raw sewage into the nearby creek. This creek emptied into a large lake that serves as the water supply for a metropolitan area and surrounding counties. Local agencies tasked with monitoring water quality noted greatly increased numbers of bacteria. Individuals that drank water from the contaminated reservoir developed nausea and vomiting, along with diarrhea, which could appear bloody (dysentery). Samples were taken from affected patients and sent for unknown organism identification of the cause of these gastrointestinal illnesses. The laboratory team isolated the organism into pure culture and it was provided to you on a nutrient agar plate and in a liquid broth culture tube for further investigation.

Case Introduction Questions Based on the information in the case, what organism(s) could or should be suspected to cause this scenario? Select all that apply. Escherichia coli Salmonella typhimurium Shigella sonnei

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Now that a pure culture has been isolated for you, what would be a good starting procedure to begin classifying your unknown organism?

Gram staining

Collected Lab Data Test Result

Gram staining

Gram (-) bacilli

Oxidase test No color was noted on swab, concluded as oxidase (-)

Lactose fermentation Colorless colonies were noted on MacConkey agar, unknown bacteria was concluded as lactose fermentation (-)

H S production test No black color was noted in tube, unknown bacterium was concluded to be (-) for H2S production

Citrate test Green color was noted in tube, unknown bacterium was concluded to be (-) for citrate production

Unknown bacterium identification Shigella sonnei

Completed Dichotomous Key

2

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