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not a nbme question :) - luckyluke
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11-18-2011, 06:05 PM
Which of the following agents (by its own characteristics) would most likely spread infection invivo?
A. beta hemolytic Streptococcus group A B. Proteus mirabilis C. Streptococcus pneumoniae D. Staphylococcus aureus E. Neisseria menigitidis
11-19-2011, 07:51 AM
Sorry guys
 Answer is A. Only Streptococcus group A has spreading factors: hyaluronidase, streptokinase, streptococcal DNAse.. that help them spread the infection.
11-19-2011, 08:16 AM
Hi. but staph. aureus also has all of those spreading factors: hyaluronidase, staphylokinase(like streptokinase), lipase, protease...examples of diseases caused partially due sp. factors are: osteomyelitis, pneumonia, cellulitis, impetigo...etc.
But i remember Dr, Goljan saying that Cellulitis is caused mainly by streptococci. thanks
11-19-2011, 08:48 AM
@uragan I remember in Kaplan lecture notes, they don't mention abt Staphylococcus aureus has spreading factors, as well as Prof Kim she said that S aureus has coagulase so the infection can't spread out. Where did you have the info about S aureus has spreading factors? Please tell me because this is important.
11-19-2011, 08:53 AM
Uragan is right..... please take a look at this link
http://www.life.umd.edu/classroom/bsci42...coccus.htm Hyaluronidase: "spreading factor" of S. aureus
11-19-2011, 08:57 AM
*****Pathogenesis:*****
Extracellular virulence factors: Enzymes: Coagulases: bound (clumping factor) free (coagulase-reacting factor) **** Hyaluronidase: "spreading factor" of S. aureus**** Nucleases: S. aureus; Cleaves DNA (DNase) and RNA (RNase) Fibrinolysin: staphylokinase Lipases: esterases Penicillinase
11-19-2011, 09:03 AM
@luckyluke, I read this in MRS book, I agree with you that is has Coagulase which activates prothrombin, thus converting fibrin ----> fibrinogen-----> blocks small vessels ---> then neutrophils, monocytes can not get in to the area of inflammation. C. is involved in the formation of skin abscesses, mastitis, osteomyelitis...etc.
also in case of Osteomyelitis, Pneumonia St.Aureus needs spread. factors to invade the tissue...  hope it helps @Maryam, thanks |
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