title: Surveillance of antibiotic resistance evolution and detection of class 1 and 2 integrons in human isolates of multi-resistant Salmonella Typhimurium obtained in Uruguay between 1976 and 2000.
abstract: OBJECTIVE
  To study the evolution of antibiotic resistance in isolates of Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) obtained in Uruguay between the years 1976 and 2000, and to determine the incidence of class 1 and 2 integrons in the multi-resistant isolates.
  
  
  METHODS
  We studied 258 strains of Salmonella Typhimurium from various sources, isolated between 1976 and 2000. We determined the evolution of antibiotic resistance and the distribution of class 1 and 2 integrons in all isolates by means of disk diffusion assays and PCR.
  
  
  RESULTS
  During the period 1989-2000 resistance to streptomycin was 56.8%, tetracycline 13.6%, sulfonamides 11.2%, and ampicillin 7.2%. Resistance to gentamicin, kanamycin, chloramphenicol, and nalidixic acid were lower than 5%; no resistance was detected to fluoroquinolones, oxyiminocephalosporins, and amikacin. These results show a dramatic decrease with respect to values found in the period 1976-1988. In this period, resistance to streptomycin was 63.2%, tetracycline 36.8%, sulfonamides 32.3%, and ampicillin 27.8%. Throughout the two periods, 29 multi-resistant Salmonella Typhimurium strains were isolated harboring some class of integron: 15 strains had only intI2, 11 strains presented both intI1 and intI2, and three isolates only intI1.
  
  
  CONCLUSIONS
  Our results show a marked decrease in resistance throughout these years, along with a correlation between resistance to different antibiotics and the presence of integrons.
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, 11600 Montevideo, Uruguay.
authors.forename: Marina
authors.initials: M
authors.lastname: Macedo-Viñas
authors.forename: Nicolás F
authors.initials: NF
authors.lastname: Cordeiro
authors.forename: Inés
authors.initials: I
authors.lastname: Bado
authors.forename: Silvia
authors.initials: S
authors.lastname: Herrera-Leon
authors.forename: Magdalena
authors.initials: M
authors.lastname: Vola
authors.forename: Luciana
authors.initials: L
authors.lastname: Robino
authors.forename: Ruben
authors.initials: R
authors.lastname: Gonzalez-Sanz
authors.forename: Soledad
authors.initials: S
authors.lastname: Mateos
authors.forename: Felipe
authors.initials: F
authors.lastname: Schelotto
authors.forename: Gabriela
authors.initials: G
authors.lastname: Algorta
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ayala
authors.forename: Aurora
authors.initials: A
authors.lastname: Echeita
authors.forename: Rafael
authors.initials: R
authors.lastname: Vignoli
mesh_terms: D001434:Bacteriophage Typing; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D032023:Integrons / Q000187:drug effects / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D015995:Prevalence; D012480:Salmonella Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D018571:Sentinel Surveillance; D014583:Uruguay / Q000453:epidemiology