Micro Lab 12 - Bacteriological Examination Of Food

Front 1

Enterotoxin

Back 1

Chemical secreted by microorganisms 
that affects cells lining the intestinal tract

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Coliform

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Gram‐negative bacteria that ferment lactose to 
produce gas; found in the intestinal tracts of 
animals and humans

Front 3

Lower temperatures have bacteriostatic effects on many microorganisms. Refrigeration can slow down, but not necessarily inhibit, microbial growth

Back 3

How does refrigeration affect the microorganisms 
found in milk and food?

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Microorganisms that can grow under anaerobic conditions, such as Clostridium botulinum, can
grow and thrive under vacuum sealed conditions and release toxins that cause food poisoning.

Back 4

If improperly treated canned foods are vacuum 
sealed, what kind of bacteria might survive to  cause food poisoning?

Front 5

Mannitol Salt agar (MSA)

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The addition of high amounts of salts makes 
this medium highly  selective for the halophilic 
(salt‐preferring) organisms, such as the genus 
Staphylococcus;

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Phenylethyl Alcohol agar (PEA)

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Gram-negative organisms are partially inhibited 
by the addition of alcohol, making this medium 
selective for the growth of Gram‐positive organisms.

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Mannitol Salt agar (MSA)

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it is also differential for mannitol fermentation. Halophiles that ferment mannitol will appear yellow.

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Phenylethyl Alcohol agar (PEA)

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Streptococcus species such as Streptococcus enterococci produce small, pinpoint, white colonies.

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Mannitol Salt agar (MSA)

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For example, Staphylococcus aureus will ferment mannitol to produce yellow colonies surrounded by yellow zones, while Staphylococcus epidermidis will not ferment mannitol, growing as white colonies with no yellow zones.

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Hektoen Enteric agar (HE)

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A selective and differential medium designed to 
isolate and differentiate species of Salmonella and 
Shigella from other Enterobacteriaceae.

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Salmonella‐Shigella agar (SSA)

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Used to isolate Salmonella and Shigella, while 
coliforms are  inhibited.

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Hektoen Enteric agar (HE)

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Bile salts and the dyes bromthymol blue and acid fuchsin inihibit the growth of most Gram positive organisms.

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Salmonella‐Shigella agar (SSA)

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Species of the genus Salmonella will produce dark colonies.

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Hektoen Enteric agar (HE)

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Salmonella and Shigella species produce blueish/green colonies.

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Salmonella‐Shigella agar (SSA)

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Species of the genus Shigella are inhibited or produce green or brownish colonies.

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Hektoen Enteric agar (HE)

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Coliforms such as Escherichia coli produce salmon to orange colored colonies.

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Bacteriological Examination Of Food

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Micro Lab 12 - is