Micro Q: Staph species

[GellaBella]

Hey guys,

I'm trying to help the vet hospital I shadow at become competent at identifying MRSA in an infected patient. So far we've got the methicillin-resistant part taken care of.

What we really need is a way to distinguish between the different species of Staph. Now I'm a PhD student in Micro, but most of my micro books are related to human medicine, so they deal almost exclusively with S. aureus and S. epidermidis.

What I would love to know are what are the other common Staph species that infect dogs/cats etc. (it's exclusively small animal).

So far I've found (via google):

S. dermatitis, S. intermedius, and S. hyicus (although this looks to be almost exclusively for pigs?)

We don't want to have to do a coagulase test (if we can avoid it, besides it looks like S. intermedius is coagulase + along with S. aureus).

I was thinking maybe hemolysis on blood agar plates might be indicative along with mannitol salt fermentation?

I know S. aureus is beta-hemolytic and a mannitol salt fermenter.

Do you guys know of any other Staph species we could frequently encounter in a small animal hospital and whether they are alpha/beta/non-hemolytic and fermenters of mannitol salts?

it's probably a long shot. I'm just having trouble finding things on google and in my books.

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[Angelo84]

The most common bacteria is staph pseudintermedius. You can also find Staph schleiferi. I am not sure of their hemolytic abilities.

Good luck.

 

[camboo]

Hmmm, S. aureus (subspecies aureus), S. felis (coag negative. See http://ijs.sgmjournals.org/cgi/reprint/39/4/373 ), S. schleiferi (subspecies schleiferi or subspecies coagulans) . . .

and then the good old "S. intermedius" coag positive Staph from dogs and cats (intermediate because the organisms exhibit some S. aureus-like properties and some S. epidermidis-like properties). This group has been broken down into S. pseudintermedius (most common in dogs), S. delphini, and S. intermedius. These three organisms are commonly referred to as the "Staph intermedius Group." For more info see http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2643665 or http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2045239 or
http://ijs.sgmjournals.org/cgi/content/full/55/4/1569

I've only heard of S. hyicus in pigs. I'd be really interested to hear what you find out. Have you posted your question on VIN yet?

 

[causticus]

For dogs and cats, you'll mainly be dealing with S. aureus and S. pseudintermedius (used to be referred to as intermedius, but the "real" intermedius has only been isolated from pigeons), and depending on what sites you're sampling, probably an odd smattering of coag-negatives.

Both species are coagulase positive (I know the coagulase is expensive, but it's a pretty crucial test). Both species are beta-hemolytic, but S. pseud will often exhibit a "double zone" hemolysis (though this is not reliable enough to use to ID between the two species - both species can have double zones, and I've seen S. pseud's without a double zone).

Other distinguishing biochemicals between these two species:

Pseud is ONPG and PYR positive, Aureus is ONPG and PYR negative. (You can get ONPG in tablet form and add it to a few mL of sterile water, and PYR comes as a dryslide but I think they are kind of expensive).

Clasically, Auerus is a mannitol fermenter, and Pseud is not. HOWEVER, in my time working in Veterinary Microbiology in a hospital setting, I have recently started seeing Pseud's that DO ferment mannitol (which is why we started using the ONPG and PYR), so I wouldn't recommend using this as your only test.

PolymixinB is probably the most relaible way of distinguishing these two: Pseud is predictably susceptible, and Aureus is predictably resistant. It's good to have other "backup" tests though, in cases of intermediate resistance (rare, but it happens).

Other Staph species you might come across:
S. schleiferi (subspecies coagulans) - beta hemolytic, coagulase positive, urea positive and trehalose negative (Pseud and Aur are treahalose and urea positive), does not ferment mannitol
S. schleiferi (subspecies schleiferi) - beta hemolytic, coagulase negative, urea and trehalose negative, does not ferment mannitol
S. felis in cats - coagulase negative, urea and trehalose positive

Hope this helps! Let me know if you have any other questions, and feel free to PM me any time.

 

[GellaBella]

Awesome! Thanks everyone!