title: [Frequency of enzymes associated with reduced sensitivity to beta-lactam antibiotics in enterobacteria isolates, Caracas, Venezuela].
abstract: OBJECTIVE
  To determine the frequency of enzymatic mechanisms associated with reduced sensitivity to broad-spectrum beta-lactam antibiotics in enterobacteria isolates obtained at hospital centers in Caracas, Venezuela.
  
  
  METHODS
  A cross-sectional study was conducted on enterobacteria isolated from patients at eight hospital centers in Caracas, Venezuela, from 15 October 2009 to 15 January 2010. The species were identified using conventional biochemical tests, and their susceptibility to antimicrobial drugs was assessed by antibiogram (Kirby-Bauer method), using the 2010 performance standards published by the Clinical and Laboratory Standards Institute. Beta-lactam-resistant genes were detected using an enhanced polymerase chain reaction assay.
  
  
  RESULTS
  Of 1 235 isolates, 207 (16.8%) exhibited resistance to third- and fourth-generation cephalosporins, carbapenems, or both. They presented the following phenotypes: extended-spectrum beta-lactamase (ESBL), 93.8%; depressed AmpC, 4.3%; and carbapenemase, 1.9%. Further characterization of the first two phenotypes yielded the following breakdown of types: SHV, 36.7%; CTX-M-1 group, 22.3%; TEM, 21.7%; CTX-M-1 group with impermeability, 5.2%; two-enzyme combinations, 4.5%; CTX-M-2 group, 4.3%; PER, 3.4%; and KPC, 1.9%. The SHV type was predominant in the public hospital strains, whereas the CTX-M-1 group was most common in the strains from the private hospitals.
  
  
  CONCLUSIONS
  Of the enzymatic mechanisms investigated, the SHV type was the most frequent, followed by the CTX-M-1 group and the TEM type. Also, a high percentage of type KPC was found. The research reported here is one of only a few multicenter studies that have been conducted in Venezuela to evaluate the frequency of this type of antimicrobial resistance mechanism, including phenotypical and molecular characterization. It was shown that the detection methods require proper interpretation of sensitivity profiles and molecular confirmation of the mechanism present.
authors.affiliation: Instituto Nacional de Higiene "Rafael Rangel", Caracas, Venezuela. danielmarcano2000@yahoo.com
authors.forename: Daniel
authors.initials: D
authors.lastname: Marcano
authors.forename: Andreína
authors.initials: A
authors.lastname: De Jesús
authors.forename: Luis
authors.initials: L
authors.lastname: Hernández
authors.forename: Luis
authors.initials: L
authors.lastname: Torres
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics; D015780:Carbapenems / Q000378:metabolism / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics; D002511:Cephalosporins / Q000378:metabolism / Q000494:pharmacology; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D003430:Cross-Sectional Studies; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000453:epidemiology / Q000382:microbiology*; D005798:Genes, Bacterial; D005838:Genotype; D006786:Hospitals, Urban / Q000706:statistics & numerical data; D006801:Humans; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D013379:Substrate Specificity; D014687:Venezuela / Q000453:epidemiology; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000032:analysis* / Q000145:classification / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; D002511:Cephalosporins; D001618:beta-Lactamases