In vitroactivities of vancomycin and linezolid against biofilm-producing methicillin-resistant staphylococci species isolated from catheter-related bloodstream infections from an Egyptian tertiary hospital

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Purpose.Catheter-related bloodstream infections (CRBSIs) are among the most common hospital-acquired infections. We aimed to survey methicillin resistance, biofilm production and susceptibility to vancomycin, linezolid and other antibiotics for staphylococci isolated from CRBSIs.Methodology.Fifty-eight isolates [20 S. aureus and 38 coagulase-negative staphylococci (CoNS; 20 Staphylococcusepidermidis, nine Staphylococcushaemolyticus, three Staphylococcusschleiferi, two Staphylococcuswarneri and four Staphylococcuslugdunensis)] were tested for methicillin resistance by cefoxitin disk diffusion and detection of the mecA gene by PCR; biofilm-forming ability using Congo red agar and tissue culture plate methods; susceptibility to ciprofloxacin, clindamycin, cotrimoxazole, erythromycin, gentamicin, linezolid, rifampicin and tetracycline; and MIC determination for vancomycin.Results/Key findings.Cefoxitin resistance was detected among 40% (8/20) S. aureus isolates, 70% (14/20) S. epidermidis isolates and 16.7% (3/18) of other CoNS, although the mecA gene was detected in 45% (9/20) S. aureus isolates, 35% (7/20) S. epidermidis isolates and 16.7% (3/18) of other CoNS. Biofilm-forming ability ranged from 45 to 75%. Methicillin-resistant S. aureus and other CoNS were considered to be more virulent than methicillin-resistant S. epidermidis due to the higher biofilm forming abilities of the former. All tested isolates exhibited 100% sensitivity to vancomycin and linezolid, irrespective of their methicillin resistance or biofilm-forming ability. Rifampicin showed overall sensitivity of 75.9%. Varying degrees of multi-resistance were found for the other antibiotics.Conclusion.Vancomycin, linezolid and rifampicin could be used effectively against methicillin-resistant staphylococci isolated from CRBSIs.

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