title: Extended-spectrum β-lactamase-producing enterobacteriaceae causing nosocomial infections in Mexico. A retrospective and multicenter study.
abstract: OBJECTIVE
  Extended-spectrum β-lactamase (ESBLs) production is still the most frequent mechanism of resistance to cephalosporins in gram-negative bacteria. The aim of the study was to identify the types of ESBL-producing Enterobacteriaceae clinical isolates causing nosocomial infections in Mexico.
  
  
  METHODS
  ESBL production was performed using a disk diffusion method. The MIC for several antibiotics was performed by agar dilution on Mueller-Hinton. PFGE typing was carried out on all enterobacteria assayed. The β-lactamase pattern was obtained by IEF and bioassay. Genes of β-lactamases were amplified by PCR with specific primers and products were sequenced and analyzed using informatics programs. Plasmid isolation and conjugation experiments were carried out using standard methodologies.
  
  
  RESULTS
  There were 134 isolates of Enterobacteriaceae included from a retrospective and multicenter study that included eight Mexican hospitals from 1999 to 2005. The most prevalent species were K. pneumoniae (56%), Enterobacter cloacae (29%), and Escherichia coli (15%). Molecular analysis identified the underlying endemic and polyclonal spread of enterobacterials in each hospital. The most frequent ESBLs identified were SHV-type (84%), TLA-1 (11%), and CTX-M-15 (5%). Successful matings were detected in 68.4% (71/104) isolates.
  
  
  CONCLUSIONS
  ESBL-producer K. pneumoniae remains the most frequent bacterial species obtained in nosocomial infections. The SHV-type and TLA-1 ESBLs were disseminated in most hospitals analyzed and CTX-M-15 was emerging in one of the studied hospitals. This work highlights the proper use of antibiotics to avoid the selection of these types of multiresistant bacteria.
authors.affiliation: Departamento de Diagnóstico Epidemiológico, Instituto Nacional de Salud Pública, CISEI, Cuernavaca, Morelos, Mexico.
authors.forename: Jesus
authors.initials: J
authors.lastname: Silva-Sanchez
authors.forename: Jesus Ulises
authors.initials: JU
authors.lastname: Garza-Ramos
authors.forename: Fernando
authors.initials: F
authors.lastname: Reyna-Flores
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sánchez-Perez
authors.forename: Teresa
authors.initials: T
authors.lastname: Rojas-Moreno
authors.forename: Veronica
authors.initials: V
authors.lastname: Andrade-Almaraz
authors.forename: Josefina
authors.initials: J
authors.lastname: Pastrana
authors.forename: Julieta Ivone
authors.initials: JI
authors.lastname: Castro-Romero
authors.forename: Pablo
authors.initials: P
authors.lastname: Vinuesa
authors.forename: Humberto
authors.initials: H
authors.lastname: Barrios
authors.forename: Carlos
authors.initials: C
authors.lastname: Cervantes
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002439:Cefotaxime / Q000494:pharmacology; D003226:Congresses as Topic; D003428:Cross Infection / Q000453:epidemiology*; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D004756:Enterobacteriaceae Infections / Q000453:epidemiology*; D006801:Humans; D007526:Isoelectric Point; D008800:Mexico; D008826:Microbial Sensitivity Tests; D011815:R Factors / Q000378:metabolism; D012189:Retrospective Studies; D001618:beta-Lactamases / Q000737:chemistry / Q000145:classification / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; C071167:beta-lactamase CTX-2; D001618:beta-Lactamases; D002439:Cefotaxime