Abstract

We investigated the prevalence of methicillin-resistant staphylococci (MRS) and evaluated the antimicrobial resistance patterns of 284 Staphylococcus strains isolated from two hospitals, as well as from community and the environment in Puebla City, Mexico. Isolates were identified by Gram-stain and biochemical reactions and antimicrobial susceptibility testing was performed by Kirby-Bauer and in some cases by determination of minimal inhibitory concentrations of antimicrobial agents. Result showed that from 284 strains studied, 32% (90 strains) were multidrug-resistant, of which 82% (74 strains) were methicillin-resistant. From 154 Staphylococcus aureus isolates tested, 41 strains showed methicillin-resistance (27%) and 84 of 130 coagulase-negative staphylococci showed methicillin-resistance (65%). The mecA gene was detected in 38 of 43 oxacillin-resistant staphylococci tested (14/14 S. aureus and 24/29 coagulase negative staphylococci). Nevertheless, this gene was also identified in 14 S. aureus that exhibited oxacillin and cefoxitin susceptibility. The percentages of resistance detected among S. aureus and coagulase negative staphylococcal isolates were: penicillin (79 and 67%, respectively), oxacillin (27 and 65%), erythromycin (18 and 36%), tetracycline (6 and 24%), gentamicin (71 and 45%), and trimethoprim sulfamethoxazole (19 and 37%). The b-lactamase production was positive in more than 80% of isolates. These results show the presence of multiresistant strains in these three sources, which supports the control measures taken by health authorities with respect to avoiding the misuse and abuse of antibiotics.

Key words: Staphylococcus, methicillin resistance Staphylococcus aureus (MRSA), methicillin resistance coagulase-negative staphylococci (MRCoNS), emerging infections.