Low prevalence of methicillin-resistant strains among Staphylococcus aureus colonizing young and healthy members of the community in Portugal

Recent reports suggest that methicillin-resistant Staphylococcus aureus (MR SA) may be emerging as a community pathogen. In Portuguese hospitals, the i ncidence of MRSA among disease causing isolates is extremely high (48-50%). To determine the prevalence of MRSA in the Portuguese community, nasal sam ples were obtained from 823 draftees, 484 nonmedical university students, a nd 107 high-school students. In addition, throat samples were obtained from the 823 draftees and S. aureus isolates were also recovered from 283 (13%) nasopharyngeal samples obtained from 2,111 children attending day-care cen ters. The rate of nasal colonization of S. aureus was 34%, 25%, and 46% for draftees, nonmedical university students, and high-school students, respec tively. The rate of pharyngeal colonization of the draftees was 33%. Of the 1,001 S. aureus isolates obtained, seven were MRSA and eight were borderli ne oxacillin-resistant S. aureus (BORSA). By molecular typing techniques, f ive of the seven MRSA were identified as belonging to one of three highly e pidemic clones, the Brazilian, Iberian, and Pediatric clones of MRSA, which were identified as endemic in Portuguese hospitals. The eight BORSA were a ll members of clones previously identified in international samples. In spi te of the extremely high prevalence of MRSA in Portuguese hospitals, the ca rriage rate of MRSA in healthy and young individuals remains low.