title: Genetic basis of antimicrobial drug resistance in clinical isolates of Salmonella enterica serotype Hadar from a Spanish region.
abstract: The genetic bases of antimicrobial drug resistance (R) of 79 Salmonella enterica serotype Hadar clinical isolates (recovered during 1995-2001 in a Spanish region) was investigated. The isolates showed a limited genomic variation, as demonstrated by PFGE analysis using XbaI (three profiles, S>or=0.77) and BlnI (seven profiles, S>or=0.49; with 95% of the isolates falling into two clusters, S>or=0.75). Thirteen R-profiles, ranging from susceptible to multidrug resistant, were recognized. All susceptible isolates (14%) were recovered before or during 1998, when multidrug resistance (MDR) was still uncommon (20% from 1995-1998). In later years, the percentage of MDR increased considerably (92% in 2001). Resistance to nalidixic acid, tetracycline, streptomycin and ampicillin-cefalotin, encoded by gyrA-Asp87/Asn, tet(A), strA/B, and bla (TEM) genes, respectively, were the most common, appearing together in 38% of the isolates. In all tetracycline- and streptomycin-resistant isolates, strA/B and tet(A) were chromosomally located, whereas bla (TEM) was plasmid-born. Five different bla (TEM) plasmids (pUO-ShR1 to pUO-ShR5, of about 9.4, 23, 30, 45, and 95 kb, respectively) were identified. pUO-ShR3 and pUO-ShR5 harbored additional R-genes: [dfrA1] and [acc(3)IV-strA/B], respectively. pUO-Sh2, pUO-Sh3, pUO-ShR4, and pUO-Sh5 were self-transferable, and the latter could also mobilize pUOShR1. The reported data constitute a useful background for further epidemiological studies of MDR in S. Hadar.
authors.affiliation: Departamento de Biología Funcional, Area Microbiología, Universidad de Oviedo, Oviedo, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Martinez
authors.forename: M C
authors.initials: MC
authors.lastname: Mendoza
authors.forename: B
authors.initials: B
authors.lastname: Guerra
authors.forename: M A
authors.initials: MA
authors.lastname: Gonzalez-Hevia
authors.forename: M R
authors.initials: MR
authors.lastname: Rodicio
mesh_terms: D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D032023:Integrons; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics