In this work, we describe a multiplex PCR assay for the detection of clinically relevant antibiotic resistance genes harbored by some Staphylococcus aureus isolates and for the simultaneous identification of such isolates at the species level. Conditions were optimized for the simultaneous detection of the 310-, 456-, and 651-bp regions of the mecA (encoding high-level methicillin resistance), ileS-2 (encoding high-level mupirocin resistance), and femB (encoding a factor essential for methicillin resistance) genes, respectively, from a single colony in a single reaction tube. The femB PCR fragment allows the specific identification of S. aureus. Validation of the method was performed using 50 human isolates of methicillin-resistant S. aureus (MRSA) and the appropriate control strains. This assay offers a rapid, simple, feasible, specific, sensitive, and accurate identification of mupirocin-resistant MRSA clinical isolates and could be systematically applied as a diagnostic test in clinical microbiology laboratories, facilitating the design and use of antibiotic therapy.The selective pressure resulting from the extensive use of antibiotics over the last 50 years has led to the emergence of bacterial resistance and to the dissemination of resistance genes among pathogenic microorganisms (2,17,18). The progressive emergence and rapid dissemination of antibiotic resistance in staphylococci and its association with the use and consumption of antibiotics constitute a major health concern and have been considered a global crisis (7,11,16,32). Staphylococci are ubiquitous microorganisms present in the respiratory tract and on the skin of a high percentage of adults. However, several population groups are at serious risk of suffering pathogenic staphylococcal infections. Within the genus Staphylococcus, S. aureus is the causal agent of most staphylococcal infections and is associated with serious communityacquired and nosocomial diseases. Serious complications occur because of multiple-antibiotic-resistant S. aureus. The introduction of new antibiotics in the fight against staphylococcal infections has stimulated a remarkable case of bacterial evolution in the face of changing selective pressures. Thus, the use of a new drug has always been followed by the prompt appearance of new staphylococcal resistance.The first semisynthetic penicillin, namely, methicillin, was introduced in 1959 to overcome the problems that arose from the increasing prevalence of penicillinase-producing S. aureus resistant to penicillin (15). During the 1980s, methicillin-resistant S. aureus (MRSA) started to constitute a widespread human health concern (7). Methicillin resistance in S. aureus is primarily mediated by the overproduction of PBP2a, an additional altered penicillin-binding protein with low affinity for beta-lactam antibiotics. The mecA gene, the structural determinant encoding PBP2a, is therefore considered a useful molecular marker of putative methicillin resistance in S. aureus. MRSA is one of the most important pathogens that caus...