title: Molecular basis of antimicrobial drug resistance in Staphylococcus aureus isolates recovered from young healthy carriers in Spain.
abstract: The frequency and genetic bases of antimicrobial drug resistance was determined for 111 Staphylococcus aureus recovered from young healthy carriers in a Spanish region. Resistances to ampicillin (84.7%), kanamycin (27%), erythromycin (25.2%), clindamycin (22.5%), tetracycline (11.7%), amikacin and tobramycin (6.3% each), gentamicin (5.4%), chloramphenicol (2.7%), ciprofloxacin (0.9%; MIC 4 μg/ml), moxifloxacin (0.9%) and mupirocin (0.9%; MIC 60 μg/ml) were found, and all were susceptible to methicillin (MSSA). Nearly 50% of the isolates were resistant to one antibiotic, 30% to two, 15.3% to three and 1.8% to four, while only 6.3% remained fully susceptible. A total of 31 profiles were found. For each phenotypic resistance, at least one gene accounting for it was identified. The detected genes were blaZ; erm(A)-erm(B)-erm(C)-msr(A)-msr(B)-lnu(A), aphA-aadE-sat4-aacA + aphD-aadD, tet(K), cat, and qacA/B, for resistance to ampicillin, macrolides and/or lincosamides, aminoglycosides, tetracycline, chloramphenicol, and quaternary ammonium compounds, respectively. In all isolates carrying cat genes, in all except one of the isolates positive for tet(K), and in most isolates with blaZ, erm(C), msr(A), or msr(B), the gene(s) mapped on resistance plasmids, which were detected in 69.2% of the resistant isolates (65% of the total). The S. aureus from young healthy carriers analysed in the present study do not constitute a reservoir of MRSA, but they represent a repository of multiple determinants conferring resistance to "old" antimicrobials. Some of these have still clinical applications and, considering the increasing resistance to recently introduced antimicrobials, none of them can be disregarded.
authors: Department of Functional Biology (Microbiology Section), Faculty of Medicine, University of Oviedo, Julián Clavería 6, 33006 Oviedo, Spain.
authors: M Angeles
authors: MA
authors: Argudín
authors: Department of Functional Biology (Microbiology Section), Faculty of Medicine, University of Oviedo, Julián Clavería 6, 33006 Oviedo, Spain.
authors: M Carmen
authors: MC
authors: Mendoza
authors: Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Paseo Río Linares s/n, 33300 Villaviciosa, Spain.
authors: M Cruz
authors: MC
authors: Martín
authors: Department of Functional Biology (Microbiology Section), Faculty of Medicine, University of Oviedo, Julián Clavería 6, 33006 Oviedo, Spain. Electronic address: rrodicio@uniovi.es.
authors: M Rosario
authors: MR
authors: Rodicio
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002353:Carrier State / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D013030:Spain; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents
keywords: MSSA; Plasmids; Resistance; Staphylococcus aureus