Coagulase negative staphylococci

Note that Staph aureus is coagulase positive, as it helps in the conversion of fibrinogen to fibrin which assists in the aggregation process. They are generally whitish in appearance, are DNAase and Phosphatase negative. Such organisms have great affinity to plastic, IV lines, catheters etc. The organisms (i.e.: staph epidermidis) are introduced at the time of valve replacement (for example), with clinical signs developing only after 1 year after the inoculation. Eventually can lead to an abscess formation, separation of the suture line – therefore valve ‘separates” – mechanical heart failure results?

Other organisms of importance are S. saprophyticus, S haemolyticus, S lugdunensis, S schleiferi.

These organisms can cause the following infections/contamination:

Endocarditis: This occurs usually on artificial valves

Catheter and Shunt infections: Have recently become problem due to long usage of lines, catheters and shunts for the management of critically ill patients. Produce a polysaccharide slime that can protect themselves against antibiotics, and inflammatory cells.

Prosthetic Joint infections: Hip joints commonly infected, risk of re-infection is common after being infected again and treated with re-hip-replacement and antimicrobial therapy.

Category: Microbiology Notes