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Activity of cephalosporins against coagulase-negative staphylococci
1Department of Medicine, College of Physicians & Surgeons, Columbia University, New York, New York.
Abstract:
Staphylococcus epidermidis has become an increasingly important pathogen as the cause of serious postoperative infection after heart and orthopedic surgery. We studied the susceptibilities of 80 blood, sternotomy, and hip isolates to vancomycin, cefazolin, cefuroxime, oxacillin, erythromycin, ciprofloxacin, and ofloxacin. The MIC90 of methicillin-susceptible isolates was 4 micrograms/ml for cefazolin and cefamandole, 8 micrograms/ml for cefuroxime, and 4 micrograms/ml for vancomycin. At 48 hr the MIC90 rose to 32 micrograms/ml for cefazolin and greater than 128 micrograms/ml for cefuroxime, and remained at 4 micrograms/ml for cefamandole and vancomycin. The MIC90 of methicillin-resistant isolates at 48 hr was 16 micrograms/ml cefamandole, 64 micrograms/ml cefazolin, greater than 128 micrograms/ml cefuroxime, and 4 micrograms/ml vancomycin. Ciprofloxacin and ofloxacin inhibited the majority of isolates at 1 microgram/ml, and vancomycin at 4 micrograms/ml. The new peptolide, daptomycin, also inhibited S. epidermidis at less than or equal to 1 microgram/ml.
Insights
Staphylococcus epidermidis infections after surgery are a growing concern. Vancomycin and daptomycin show consistent effectiveness against these challenging bacterial isolates.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Pharmacy
Background:
- Staphylococcus epidermidis is a significant cause of postoperative infections, particularly after cardiac and orthopedic procedures.
- The increasing prevalence of antibiotic resistance in S. epidermidis necessitates ongoing surveillance of antimicrobial susceptibilities.
Purpose of the Study:
- To evaluate the in vitro antimicrobial susceptibility of clinical isolates of Staphylococcus epidermidis.
- To assess the efficacy of various antibiotics, including vancomycin, cephalosporins, fluoroquinolones, and daptomycin, against S. epidermidis.
Main Methods:
- Susceptibility testing was performed on 80 clinical isolates of Staphylococcus epidermidis from blood, sternotomy, and hip sites.
- Minimum Inhibitory Concentration 90 (MIC90) values were determined for vancomycin, cefazolin, cefuroxime, oxacillin, erythromycin, ciprofloxacin, and ofloxacin at different time points.
- The activity of daptomycin against S. epidermidis was also evaluated.
Main Results:
- Vancomycin demonstrated consistent MIC90 values of 4 µg/ml for both methicillin-susceptible and methicillin-resistant S. epidermidis isolates.
- Cefazolin and cefuroxime showed reduced efficacy over time, especially against methicillin-resistant strains.
- Ciprofloxacin, ofloxacin, and daptomycin exhibited potent activity, inhibiting the majority of isolates at low concentrations (≤ 1-4 µg/ml).
Conclusions:
- Vancomycin remains a reliable option for treating S. epidermidis infections.
- Emerging resistance to certain cephalosporins highlights the need for careful antibiotic selection.
- Daptomycin shows promise as an effective therapeutic agent against Staphylococcus epidermidis.