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.
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.
Macedo-Viñas
Marina
M
Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, 11600 Montevideo, Uruguay.
Cordeiro
Nicolás F
NF
Bado
Inés
I
Herrera-Leon
Silvia
S
Vola
Magdalena
M
Robino
Luciana
L
Gonzalez-Sanz
Ruben
R
Mateos
Soledad
S
Schelotto
Felipe
F
Algorta
Gabriela
G
Ayala
Juan A
JA
Echeita
Aurora
A
Vignoli
Rafael
R
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