What do Staphylococcus and
Micrococcus have in common? - ANSWERS• Location: widespread in nature and on
human skin, although Micrococcus is more
transient
• Catalase Reaction: Strongly Positive
• Appearance on Gram Stain: Gram Positive
Cocci, nonmotile
Pathogenicity - ANSWERSMi...
Micrococcus have in common? - ANSWERS• Location: widespread in nature and on
human skin, although Micrococcus is more
transient
• Catalase Reaction: Strongly Positive
• Appearance on Gram Stain: Gram Positive
Cocci, nonmotile
Pathogenicity - ANSWERSMicrococcus is a harmless saprophyte; Staph is opportunistic, especially if skin
is penetrated
Oxygen Requirements - ANSWERSMicrococcus is a strict aerobe (it is also oxidase positive); Staph
species are facultative anaerobes
Arrangement - ANSWERSMicrococcus makes tetrads more often than Staph; both also make clusters
Resistance to Salt - ANSWERSStaph is a halophile, Micrococcus less so
Micrococcus vs Staphylococcus - ANSWERS* Since they are both commonly isolated from clinical
specimens, it is important to be able to differentiate whether the isolate is a harmless bystander or a
potential cause of infection.
* Remember Koch's Postulates? Isolating
something from a clinical specimen does
NOT prove it is the cause of the disease.
, Two Species of Staph Associated with Human Disease - ANSWERS• Staphylococcus aureus -the more
virulent
• Staphylococcus epidermidis - usually harmless unless inserted through skin via a catheter, surgical
procedure or needle
Exotoxins - Categories - ANSWERS- Neurotoxins work on neurons
- Enterotoxins work on the enteric tract; Gl symptoms
- Cytotoxins destroy cells, entire tissues
Optional Toxins Present in Staph aureus - ANSWERS• Cytolytic toxins that act against WBCs
• Exfoliative toxins dissolve desmosomes which lock epithelial cells together, causing skin cells to
separate and slough off
• TSS Toxin: causes toxic shock
• Enterotoxins: 5 proteins, A through E, which stimulate intense intestinal spasms, vomiting, nausea and
diarrhea.
S. aureus Food Intoxication - ANSWERS• NOT food poisoning - bacteria may be dead, but toxin is left
behind
• High-protein, creamy foods contaminated with skin flora, then kept at RT for several hours
• Re-heating food will not break down toxin: stable at boiling temps. for 30 minutes
• Food has no off taste or smell
• Rapid symptoms -within 4 hours
• Rapid resolution, once toxin is expelled
What Determines Pathogenicity in Staph? - ANSWERS• Coagulase is an enzyme bound to the outer
surface and secreted into environment
• Coagulase causes blood to clot by activating the conversion of fibrinogen to fibrin
• Fibrin clots hide the bacteria from phagocytic cells
• ONLY Staphylococcus aureus produces
coagulase!
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller papersmaster01. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $15.99. You're not tied to anything after your purchase.
