Abstract
IntroductionThe increase of Salmonella enterica isolates multi-resistant to different antibiotics, including β-lactams and fluoroquinolones, is a problem of clinical importance. The dissemination of Salmonella Typhimurium resistant to ampicillin (AMP)-chloramphenicol (CHL)-streptomycin (STR)-sulphonamides and (SUL)-tetracycline (TET), that harbour the Salmonella Genomic Island type1 (SGI1), and the acquisition of transferable genetic material have favoured the multi-resistance in this genus. MethodsA total of 114clinical S.enterica isolates were studied (period 2009-2010). The susceptibility to 20antibiotics was determined by disc diffusion and microdilution. The antimicrobial resistance mechanisms and the integrons were analysed by PCR, and sequencing in the AMPR isolates. In all the blaPSE-1-positive isolates, the clonal relationship was determined by PFGE, as well as the presence of SGI1 and 29 virulence genes by PCR. ResultsEighteen different serotypes were found among the 114isolates studied, Typhimurium (61%) and Enteritidis (16%) being the most prevalent. High percentages of resistance to SUL (68%), TET (58%), AMP (55%) and STR (46%) were observed. The great majority (92%) of 63 AMPR isolates were multi-resistant, with the AMP-STR-TET-SUL phenotype (19 isolates) being the most frequent one and associated with the blaTEM-1b+strA-strB+tet(B)+sul2 genotype. Class1 integrons (7different structures) were observed in 48% AMPR isolates, highlighting the blaOXA-1+aadA1 structure (8isolates), one empty integron and non-classical integrons (5isolates). The blaPSE-1 gene was detected inside the classical SGI1 structure in 13clonally-related isolates that showed the same virulence profile. ConclusionsThe high percentage of multi-resistant S.enterica isolates, especially associated to S.Typhimurium, to the AMP, STR, TET and SUL phenotype, and to the blaTEM-1b+strA-strB+tet(B)+sul2 genotype, shows an important risk of possible failures in the treatment of serious infections caused by this serotype.
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