Coagulase-negative staphylococci (CoNS) are a group of bacteria that are part of the normal flora of the human skin and mucous membranes. Despite being less virulent than their coagulase-positive counterpart,
Staphylococcus aureus, CoNS are increasingly recognized as significant pathogens, especially in the context of healthcare-associated infections. This discussion will address common questions about CoNS, focusing on their epidemiology, pathogenesis, clinical significance, diagnosis, and treatment.
What are Coagulase-Negative Staphylococci?
How do CoNS cause infections?
CoNS are typically commensal organisms; however, they can cause infections when they breach the skin barrier or colonize implanted medical devices. They possess several
virulence factors that enable them to adhere to surfaces and form biofilms, which shield them from the host immune response and antibiotic treatment. The ability to form biofilms is particularly important in their role as pathogens in device-related infections.
What is the clinical significance of CoNS?
While CoNS are often dismissed as mere contaminants in blood cultures, they are significant
nosocomial pathogens. They are the most common cause of catheter-related bloodstream infections, prosthetic joint infections, and infections associated with other implanted devices such as cardiac pacemakers and prosthetic heart valves. Staphylococcus saprophyticus is a well-recognized cause of
urinary tract infections in young women. In patients with weakened immune systems, such as those undergoing chemotherapy, CoNS can cause severe infections.
How are CoNS infections diagnosed?
Diagnosing CoNS infections can be challenging due to their presence as normal skin flora and frequent contamination of blood cultures. A true CoNS infection is suggested by multiple positive blood cultures, clinical signs of infection, and the absence of other identifiable causes. Molecular methods, such as
PCR, and advanced techniques like mass spectrometry, can aid in the rapid identification and differentiation of CoNS species, which is critical for appropriate management.
How are CoNS infections treated?
Treatment of CoNS infections can be complex due to their ability to resist many antibiotics. Methicillin-resistant coagulase-negative staphylococci (MRCoNS) are common, necessitating the use of
vancomycin or other last-resort antibiotics like
linezolid and
daptomycin. Biofilm-associated infections often require removal of the infected device in addition to antibiotic therapy. The selection of antibiotics should be guided by susceptibility testing, and treatment duration depends on the site and severity of the infection.
Preventing CoNS infections involves stringent adherence to
infection control practices, including hand hygiene, aseptic techniques during catheter insertion, and timely removal of unnecessary medical devices. Developing anti-biofilm strategies and coatings for medical devices is an active area of research aimed at reducing the incidence of CoNS infections.
In conclusion, while coagulase-negative staphylococci are part of the normal human microbiota, they are significant pathogens in certain contexts, particularly in healthcare settings. Understanding their clinical implications, diagnostic challenges, and treatment options is crucial for effectively managing these infections.
