From the Guidelines
Coagulase-negative staphylococci (CoNS) infections should be treated with vancomycin as the first-line therapy, given its effectiveness against methicillin-resistant strains, which are commonly encountered in clinical practice, as noted in the 2015 American Heart Association guidelines 1. When treating CoNS infections, particularly those involving prosthetic valves, it is crucial to consider the potential for methicillin resistance and the formation of biofilms on medical devices.
- Vancomycin is typically administered at 15-20 mg/kg IV every 8-12 hours, adjusted for renal function, for a duration of 7-14 days depending on the severity of the infection.
- For methicillin-susceptible strains, nafcillin or oxacillin at 2g IV every 4 hours may be used as alternatives.
- Daptomycin (6-10 mg/kg IV daily) or linezolid (600 mg IV/PO twice daily) are options for resistant strains.
- The addition of rifampin to vancomycin, along with an aminoglycoside for the initial 2 weeks, is recommended for prosthetic valve endocarditis caused by CoNS, as suggested by the European Society of Cardiology guidelines 1.
- Device-related infections often require the removal of the infected device in addition to antibiotic therapy, highlighting the importance of a comprehensive approach to managing CoNS infections.
- Susceptibility testing is vital due to the high prevalence of methicillin resistance among CoNS, which can guide the selection of appropriate antibiotic therapy, as emphasized in the guidelines for the management of infective endocarditis 1.
From the Research
Coagulase-Negative Staphylococci
- Coagulase-negative staphylococci (CoNS) are Gram-positive organisms that are a known component of normal skin flora and the most common cause of nosocomial bacteremia 2.
- CoNS resistance to meticillin and other semisynthetic penicillins is now common, and elevated vancomycin minimal inhibitory concentrations (MICs) have been reported and are associated with worse treatment outcomes 3.
Vancomycin Susceptibility
- The vancomycin MIC breakpoint for susceptibility set by the Clinical and Laboratory Standards Institute is ≤4 µg/mL 2.
- Low susceptibility to vancomycin is frequent in the CoNS strains studied in some hospitals, with 61% of strains showing loss of susceptibility to vancomycin, MIC = 2 mg/L 4.
- However, other studies have found that vancomycin MICs decreased over the study period despite widespread use of vancomycin 5.
Alternative Antibiotics
- Daptomycin has good activity against all CoNS isolates, with a susceptibility range between 0.032-1 mg/L and modal value of 0.25 mg/L 4.
- Telavancin tended to have MICs that were 1-2 dilutions lower than vancomycin 3.
- Linezolid resistance was observed in 11.5% of CoNS strains, and the massive and continuous use of linezolid has led to the appearance of resistance 4.
Clinical Outcomes
- There was no difference in clinical outcomes in adult patients with a CoNS bloodstream infection with a vancomycin MIC <2 µg/mL versus ≥2 µg/mL 2.
- However, vancomycin heteroresistance was associated with poor clinical outcomes, including treatment failure and persistent bacteremia, in pediatric patients with leukemia 6.