ABSTRACT
Salmonella enterica serovar Rissen is one of the most common serovars found in pigs and pork products in different countries, including Spain. However, information on the molecular bases of antimicrobial drug resistance and the population structure of Salmonella Rissen from different sources in Spain is limited. The present study focused on 84 isolates collected in Spain from pig and beef carcasses, foods and clinical samples associated with sporadic cases of gastroenteritis, and one outbreak. The majority of the isolates were resistant to tetracycline (73.8%), mainly conferred by tet(A). Resistances to streptomycin (aadA1-like, aadA2, and strAB), sulfonamides (sul1, sul2, and sul3), trimethoprim (dfrA1-like and dfrA12), ampicillin (blaTEM-1-like), and chloramphenicol (cmlA1-like) were also detected, with frequencies ranging from 12% to 20.2%. Most of the identified genes were carried by integrons, including three class 1 integrons of the sul1 type, a class 1 integron of the sul3 type, and the class 2 integron of Tn7. Two sul1 integrons, the sul3 integron, and the class 2 integron are first reported in Salmonella Rissen. Typing of the isolates with XbaI pulsed-field gel electrophoresis detected a major clone, which was circulating in humans and animals during the past decade, and was responsible for the outbreak. The obtained results are relevant for food safety and public health.
Subject(s)
Drug Resistance, Multiple, Bacterial/genetics , Red Meat/microbiology , Salmonella enterica/genetics , Salmonella enterica/isolation & purification , Animals , Cattle , Feces/microbiology , Genes, Bacterial/genetics , Humans , Integrons/genetics , Microbial Sensitivity Tests/methods , Molecular Typing/methods , Salmonella Infections, Animal/microbiology , Swine/microbiology , Urine/microbiologyABSTRACT
OBJECTIVE: Epidemiological and microbiological study of a salmonellosis outbreak, affecting 22 children in a nursery school in Oviedo (Spain). METHODS: Attack rates and epidemic curves were determined, and bacterial typing methods were applied. RESULTS: The outbreak was attributed to a Salmonella enterica serovar Typhimurium strain, belonging to an emergent type characterized by the presence of a hybrid virulence-resistance plasmid of 125-130 kb, named pUO-StVR2. The attack rate of confirmed cases vs. possible cases was 27.2% vs. 23.5% for the children and 0 vs. 26.5% for the staff of the affected center. The source of the infection could not be identified. Nevertheless, according to the evolution of the cases over time, the transmission route was likely to be personal contact between the staff and children, which facilitates fecal-oral dissemination. All but one of the 27 isolates analyzed (from 22 patients) showed identical features: R-profile, plasmid-profile, RAPD-type, PFGE-type; all were non-phage-typeable, with the exception of a DT104b isolate. pUO-StVR2 is probably a derivative of the virulence plasmid pSLT from the LT2 type strain that acquired an R-region complex (ACSSuT/blaOXA-catA1-strA/ B-aadA1-sul1-sul2-tet[B]), in which the blaOXA-aadA1 genes are part of the variable region of a class 1 integron. CONCLUSION: This outbreak is an example of how a Salmonella enterica serovar Typhimurium strain belonging to a type that is probably endemic in Spain can be transferred to the community and affect a susceptible population.
Subject(s)
Disease Outbreaks , Gastroenteritis/epidemiology , Gastroenteritis/microbiology , Salmonella Infections/epidemiology , Salmonella typhimurium , Schools, Nursery , Adult , Child, Preschool , Humans , Plasmids , Salmonella Infections/microbiology , Salmonella typhimurium/classification , Salmonella typhimurium/genetics , Salmonella typhimurium/pathogenicity , Serotyping , Spain , Virulence , Virulence FactorsABSTRACT
Objetivo. El estudio epidemiológico y microbiológico de un brote de salmonelosis ocurrido en 2004, que afectó a 22 niños de una guardería en Oviedo. Métodos. Se determinaron las tasas de ataque y curvas epidémicas y se aplicaron técnicas de tipificación bacteriana. Resultados. El brote pudo atribuirse a una cepa de Salmonella enterica serovar Typhimurium perteneciente a un grupo emergente que alberga un plásmido híbrido de virulencia-resistencia de 125-130 kb, denominado pUO-StVR2. Las tasas de ataque para los casos confirmados frente a los posibles fue 27,2% frente a 23,5% para los niños y 0 frente a 26,5% para el personal del centro. La fuente de infección no pudo ser identificada, aunque según la evolución temporal de los casos se podría considerar que el modo de transmisión fue el contacto cuidadoras-niños, facilitando la diseminación fecal-oral. Todos menos uno de los 27 aislamientos analizados (de 22 pacientes) presentaban características idénticas: perfil-R, perfil de plásmidos, RAPD-tipo, PFGE-tipo y eran no fagotipificables (la excepción fue un aislamiento con fagotipo DT104b). pUO-StVR2 es un derivado del plásmido de virulencia, pSLT, de la cepa tipo LT2 que ha ganado una región-R compleja (ACSSuT/blaOXA-catA1-strA/ B-aadA1-sul1-sul2-tet[B]) en la que los genes blaOXA-aadA1 forman parte de la región variable de un integrón de clase 1. Conclusión. Este brote constituye un ejemplo de cómo una cepa de S. enterica serovar Typhimurium, perteneciente a un tipo probablemente ya endémico en la península Ibérica, puede transmitirse a la comunidad y afectar a un colectivo susceptible (AU)
Objective. Epidemiological and microbiological study of a salmonellosis outbreak, affecting 22 children in a nursery school in Oviedo (Spain). Methods. Attack rates and epidemic curves were determined, and bacterial typing methods were applied. Results. The outbreak was attributed to a Salmonella enterica serovar Typhimurium strain, belonging to an emergent type characterized by the presence of a hybrid virulence-resistance plasmid of 125-130 kb, named pUO-StVR2. The attack rate of confirmed cases vs. possible cases was 27.2% vs. 23.5% for the children and 0 vs. 26.5% for the staff of the affected center. The source of the infection could not be identified. Nevertheless, according to the evolution of the cases over time, the transmission route was likely to be personal contact between the staff and children, which facilitates fecal-oral dissemination. All but one of the 27 isolates analyzed (from 22 patients) showed identical features: R-profile, plasmid-profile, RAPD-type, PFGE-type; all were non-phage-typeable, with the exception of a DT104b isolate. pUO-StVR2 is probably a derivative of the virulence plasmid pSLT from the LT2 type strain that acquired an R-region complex (ACSSuT/blaOXA-catA1-strA/ B-aadA1-sul1-sul2-tet[B]), in which the blaOXA-aadA1 genes are part of the variable region of a class 1 integron. Conclusion. This outbreak is an example of how a Salmonella enterica serovar Typhimurium strain belonging to a type that is probably endemic in Spain can be transferred to the community and affect a susceptible population (AU)
