Abstract

This study was undertaken to determine the species distribution and antibiotic resistance patterns of coagulase-negative Staphylococci (CoNS) other than Staphylococcus epidermidis. A total of 142 CoNS (except S. epidermidis) strains were isolated from a variety of clinical specimens in neutropenic patients at the Bone Marrow Transplant Centre of Tunisia between 2002 and 2004. All CoNS isolates were further identified by Api ID32 STAPH and ITS-PCR and antibiotic sensitivity was performed by disc diffusion method. Staphylococcus haemolyticus was the commonest species (38%) followed by Staphylococcus hominis (36%). All isolates were sensitive to vancomycin and 8 (6%) strains showed a reduced sensitivity to teicoplanin. Resistance to penicillin G and methicillin was 84 and 60%, respectively. Methicillin-resistant CoNS strains were determined to be more resistant to antibiotics than methicillin-susceptible CoNS strains. The mecA gene was detected by PCR in 65% (92/142) CoNS isolates. Out of 92 mecA-positive isolates, 90 were phenotypically methicillin-resistant and two were methicillin-susceptible. Phylogenetic analysis, carried out to study the evolution of mecA genes between different Staphylococcal species, revealed a high homology for such genes among Staphylococci.

Key words: Coagulase-negative Staphylococci, methicillin-resistance, mecA gene.