Serotypes and multidrug-resistance profiles of Salmonellae isolated from pigs infected simultaneously with various strains

VICTORIA GARRIDO; BEATRIZ SAN ROMÁN; SAMANTA SANCHEZ; JUAN PABLO VICO; RAUL CARLOS MAINAR JAIME; MARÍA JESÚS GRILLÓ

Tours

Congreso; 4th Symposium on Antimicrobial Resistance in Animals and the Environment.; 2011

Salmonellosis is a major zoonosis worlwide distributed. Pigs infected asymptomatically are an important source of human salmonelosis. To determine whether pigs could be simultaneously infected by multiple strains of Salmonella spp., 2-12 (when available) isolated colonies of Salmonella spp. were analyzed from mesenteric lymph nodes in each of 13 infected pigs, selected from farms previously identified with multiple circulating strains. Isolated strains were serotyped by Kauffman-White ans analyzwb by Kirby-Bauer against 19 agents. A total of 60 Salmonella spp. strains, belonging to 7 serotypes and 5 serogroups, and showing 12 antimicrobial resistance (AR) patterns were isolated. The most frecuent was Typhimurium, Rissen and Kapemba serotypes, and ACSSuT(Nx) and CSSuT multidrug resistance patterns. Most of animals were coinfected with strains of 2-3 serotypes (7 out 13) and AR patterns (all). Strikingly, serotype coinfections were caused by strains of different serogroups, suggesting infections from multiple sources in a period and/or reinfections at different periods of its productive life, and also a possible specific serogroup protyection against reinfection. If this latter observation is confirmed in controlled experiments in pigs, it would be crucial in the development of effective vaccines against porcine salmonellosis. Only 3 isolated were susceptible to all the agents tested, but they occupied the same niche that multi-AR strains. The ACSSuT(Nx) family was predominnatly associated to S. Typhimurium (6 pigs) and CSSuT to S. Kapemba (3 pigs). However, horizontal transfer of mobile genetics elements between serotypes could exists. To our knowledge, this is the first report describing the existence of coinfections with Salmonella strains in pigs. Epidemiologically, it could explain differences between baseline studies and to amend some of the results on prevalent Salmonella strains in pigs. Further experiments are now being conducted to genetic characterization of these strains.