Ninety-six clinical isolates ofStaphylococcus aureus is a major cause of both hospital-and community-acquired infections. In particular, methicillin (meticillin)-resistant S. aureus (MRSA) strains have been detected worldwide (15), and the prevalence of MRSA varies among countries and health institutions (2,4,27). The emergence of MRSA strains resistant to glycopeptides, as well as the increasing prevalence in the community (7), highlights the need for worldwide epidemiological studies of this pathogen. However, data about the epidemiology and prevalence of staphylococcal infections in Africa are scarce compared to information about such infections in the rest of the world. Studies have indicated low prevalences of MRSA in Nigeria, Somalia, and Tanzania (1), but high prevalences in South Africa, Zimbabwe, Kenya, Ethiopia, Egypt, Senegal, and the Ivory Coast have been reported (2,9,18). In addition, a recent study of the genetic diversity of S. aureus strains in a carriage population from Mali showed a high frequency of a PantonValentine leukocidin (PVL)-positive clone (25). The mechanisms for the emergence and spread of S. aureus clones in Africa are largely unknown; hence, the characterization of isolates may provide baseline information needed in establishing effective infection control measures in Nigeria.In this study, a total of 96 S. aureus isolates obtained between January and December 2007 from clinical specimens in six tertiary-care hospitals located in northeastern Nigeria were characterized. The isolates were identified based on standard bacteriological procedures (i.e., Gram staining and catalase, tube coagulase, and DNase testing), and susceptibilities to 12 antibiotics (Table 1) were determined by the disk diffusion method according to the CLSI guidelines. All the isolates were susceptible to vancomycin, fusidic acid, and mupirocin, and 12 (12.5%) were resistant to methicillin (i.e., oxacillin and cefoxitin resistant) ( Table 1). The MRSA isolates were multidrug resistant (i.e., resistant to beta-lactams, along with at least three other classes of antibiotics), a finding similar to previously reported findings in other African countries like Morocco, Kenya, Cameroon, and South Africa (17). MRSA resistance to non-beta-lactams may further increase the medical expenses and the complexity of patient management, as well as morbidity and mortality rates since alternative antibiotics may not be affordable in many African countries.The genetic diversity of the S. aureus population was assessed by the highly discriminatory double-locus sequence typing (DLST) method as described previously (20). This method is based on the analysis of partial sequences (about 500 bp) of the variable clfB and spa genes. A total of 41 clfB and 46 spa alleles were observed among the 96 S. aureus isolates evaluated by DLST, and these alleles represented 53 different DLST types. The eBURST software was used to cluster DLST types with identical sequences of at least one allele. Cluster analysis showed a low level of diversity amon...