Characterization of porcine S. typhimurium strains isolated in the state of Rio Grande do Sul, Brazil, by phage typing, antimicrobial resistance profile, REP-PCR and ERIC-PCR

Abstract

A collection of 96 S. Typhimurium porcine strains isolated in state of Rio Grande do Sul, Brazil during 1999/2001 was submitted to phage typing, antimicrobial susceptibility test and rep- PCR. DT 177 was the most frequent phage type identified. The antibiotic resistance profile showed a high diversity even among strains from the same phage type. The rep-PCR profile was highly conserved among the strains isolated in this region. Introduction Salmonella is an important food-borne pathogen that can be associated with pork consumption (Davies, 2001). The investigation of phenotypic and molecular profiles is an impor- tant step to the epidemiological characterization of Salmonella strains (Olsen et al., 1993). Among the methods that have been used for this purpose, the phage typing and the antibiotic resistance pattern have been adopted worldwide, often associated with molecular methods (Ang-Kucuker et al., 2000;Rahman,2002).The aim of this study was to characterize strains of S.Typhimurium isolat- ed from pigs in Southern Brazil, using phage typing, antimicrobial resistance pattern and REP and ERIC-PCR profiles. Materials and Methods Ninety six porcine strains os S. Typhimurium isolated between 1999 and 2001 were used in this study. Strains were isolated from submandibular lymph nodes, mesenteric lymph nodes, tonsils and intestinal content of healthy pigs slaughtered in three slaughterhouses (I, II, III) located in the state of Rio Grande do Sul, Brazil. Furthermore, strains isolated from pork sausage samples, collected in slaughterhouse I, were also included in this study.The phage typing was conducted at the Robert Koch Institut, Wernigerode Branch, Germany. Antimicrobial suscepti- bility was tested according to the Guidelines of the National Committee for Clinical Laboratory Standards (NCCLS,2001) for the disk method on Mueller-Hinton agar, using fourteen antimicro- bials. Total DNA was prepared according to the method of Rademaker and Bruijn (1997). REP-PCR and ERIC-PCR were conducted as previouly described by Versalovic et al. (1994). Results Phage types DT 177 (49,0%), DT 194 (8,3%) and DT 193 (5,3%) were the most prevalent among porcine strains. Twenty seven percent of the strains react with typing phages, but do not confirm with any definitive phage types, and were called RDNC. In slaughterhouse II DT177 was the only phage type detected among strains isolated in a two years period (Table 1). Among the Typhimurium strains isolated, only two were sensible to all tested antibiotics. The porcine strains showed resistance against tetracycline (91,7%), streptomycin (74%), sulphonamide (62,5%), nalidixic acid (41,7%), chloramphenicol (35,4%), sulfamethoxazole-trimethoprim (31,2%), ampi- cillin (25%), neomicin (10,4%), tobramycin (8,3%), gentamicin (7,3%), amikacin (2,1%), cefaclor (2,1%). All strains were susceptible to ciprofloxacin and to amoxicillin/clavulanic acid. Only one fin- gerprinting profile was obtained for each, ERIC-PCR and REP-PCR method.