Scenario You have graduated from your degree and are looking for a job. There isn't much available, so you decide to be proactive about your future.

Scenario

You have graduated from your degree and are looking for a job. There isn't much available, so you decide to be proactive about your future. You call your uni friends who have managed to land a job (the ones that did a major in microbiology) and manage to convince enough of your friends to pitch in a total of $100,000, which is enough to start up the Victorian Chocolate Company. You aren't going to make just another chocolate, you are going to make the finest chocolate in the country, drawing on local fresh milk and the highest quality cocoa beans imported from South America.

You want your chocolate to be as natural as possible, so you decide against any "unnecessary" treatment of your raw ingredients. Things seem to be going well in the first few months - that is until you have a phone call from a person claiming to have eaten your chocolate and developed diarrhoea, stomach cramps and malaise after consuming your chocolate. Through grimaced teeth, you politely tell the customer that while you are sorry that they have recently been sick, it is highly unlikely that their illness was the result of consumption of chocolate produced by the Victorian Chocolate Company.

By chance, you run into your old microbiology lecturer in town one day. You tell your former lecturer with some pride of your chocolate venture. Through the progression of the conversation you asked about the likelihood of someone getting sick from consuming chocolate. Your former lecturer offers to do a review of your manufacturing practises.

One week later your former lecturer comes to your manufacturing plant and takes numerous swabs of your equipment. The swabs were taken back to the Fed Uni microbiology lab and cultured on various selective and differential agars. Two days later, your lecturer calls you and says "I have found numerous bacteria with the following characteristics". Those characteristics are listed below.

MacConkey agar: Gram stain: Motility test: Catalase: Oxidase: Glucose: Mannitol:

ONPG:

Urease:

Methyl Red: Voges Proskauer: Indole:

Good growth, beige coloured colonies Gram negative rod

Positive

Positive

Negative Fermentation Positive Negative Negative Positive Negative Negative

1. 1.1 Based on these data, what is the likely identification of the bacteria isolated? Use your lecture notes and text book to guide your identification.
2. 1.2 List two additional tests that you could perform to verify/confirm your identification in 1.1. How does the test work, and is it a phenotypic or genotypic test? (N.B. this question builds on your answer in question 1, so the additional tests should be applicable to your suspected bacteria).
3. 1.3 Do you think this organism could be responsible for the illness of your customer? Base your answer on (a) the known pathogenicity of the organism; and (b) does the literature support the possibility of this organism causing foodborne illness in chocolate or similar/associated foods? Use references to support your answer.