Coagulase-negative staphylococcus

An overview of coagulase-negative staphylococci, their characteristics, clinical significance, and treatment.

Coagulase-negative staphylococci (CoNS) are a group of Staphylococcus species that do not produce the enzyme coagulase. Unlike their coagulase-positive counterpart, Staphylococcus aureus, CoNS are generally less virulent but are significant as opportunistic pathogens, particularly in hospital-acquired infections.

Characteristics

Coagulase-negative staphylococci are Gram-positive bacteria that appear as clusters under a microscope. They are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen. CoNS are part of the normal human microbiota, commonly found on the skin and mucous membranes.

Species

There are over 40 species of CoNS, but the most clinically significant include:

• Staphylococcus epidermidis - The most common CoNS species, often associated with infections related to indwelling medical devices such as catheters and prosthetic joints.
• Staphylococcus saprophyticus - Known for causing urinary tract infections in young women.
• Staphylococcus lugdunensis - Can cause more severe infections similar to those caused by S. aureus.

Clinical Significance

CoNS are a leading cause of nosocomial infections, particularly in patients with compromised immune systems or those with implanted medical devices. They are known for their ability to form biofilms, which protect them from the host immune response and antibiotic treatment.

Infections

CoNS can cause a variety of infections, including:

• Bacteremia
• Endocarditis
• Surgical site infections
• Peritonitis

Diagnosis

Diagnosis of CoNS infections typically involves blood cultures and other microbiological techniques. It is important to distinguish between true infection and contamination, as CoNS are common skin commensals.

Treatment

Treatment of CoNS infections can be challenging due to their intrinsic resistance to many antibiotics. Vancomycin is often used as a first-line treatment, especially for methicillin-resistant strains. Removal of infected devices is also a critical component of treatment.

Prevention

Preventive measures include strict adherence to aseptic techniques during medical procedures and careful monitoring of patients with indwelling devices.

Also see

• Staphylococcus aureus
• Methicillin-resistant Staphylococcus aureus (MRSA)
• Biofilm
• Nosocomial infection