coagulasenegative

Coagulasesnegative, in microbiology, refers to a group of Staphylococcus species that do not produce the enzyme coagulase. They contrast with Staphylococcus aureus, which is coagulase-positive. Coagulase-negative staphylococci (CoNS) are common inhabitants of human skin and mucous membranes and are generally less virulent, though they can cause opportunistic infections, particularly in hospital settings or with indwelling devices.

Identification and species: Most clinically relevant CoNS are Gram-positive cocci that grow in clusters, are catalase-positive, and yield a negative coagulase test. Common species include Staphylococcus epidermidis, S. saprophyticus, S. haemolyticus, and S. lugdunensis. Distinguishing CoNS from S. aureus relies on the coagulase test; S. saprophyticus is typically novobiocin resistant, while S. epidermidis is usually susceptible.

Clinical significance: Although often contaminants in cultures, CoNS are important pathogens in hospitalized patients, especially with implanted devices such as prosthetic joints, catheters, and heart valves. They can cause bacteremia, endocarditis, wound infections, and device-associated infections.

Pathogenesis: Biofilm formation on artificial surfaces contributes to persistence and antibiotic resistance, aided by surface adhesins and extracellular polysaccharide matrix; the icaADBC operon is involved in many strains.

Treatment and resistance: Management relies on susceptibility testing. Methicillin resistance is common due to mecA. Severe infections are treated with vancomycin; alternatives include linezolid or daptomycin. For device-associated infections, removal of the infected device plus antibiotics is often necessary; rifampin may be used in combination for biofilms.

Epidemiology and prevention: CoNS are frequent causes of nosocomial bacteremia and prosthetic-device infections. Prevention focuses on aseptic technique, careful device management, and minimizing indwelling lines; interpretation of culture results should distinguish true infection from contamination.