Epidemiological Analysis of Salmonella Enterica Serovar Typhimurium and Serovar 1,4,[5],12:i:- Isolates Determined by Pulsed Field Gel Electrophoresis and Antibiotic Susceptibility: Comparison of Isolates from Broiler Chickens, Humans and the Environment in Reunion Island

Abstract

Salmonella enterica ssp. enterica is a leading cause of bacterial food-borne disease outbreaks worldwide and is also an economic burden particularly in Reunion Island because its population consumes large amounts of chicken and cooks 100% chicken sausages (35 kg per capita per year). The aim of this study was to investigate the epidemiology of Salmonella Typhimurium and Salmonella 1,4,[5],12:i:-from broiler chickens, humans and the environment by using pulsed field gel electrophoresis (PFGE) and antibiotic susceptibility and to assess the significance of broiler chicken meat as a source of human infection. A total of 157 Salmonella Typhimurium and 19 S. I 4,[5],12:i:-were collected and isolated from broiler chickens, humans and the environment between October 2007 and January 2009. The PFGE of Xba1 digested chromosomal DNA gave 30 distinct profiles for Salmonella Typhimurium and S. 1,4,[5],12:i:-. Salmonella Typhimurium was characterized by a main pulsotype (B54) and accounted for 32% of all isolates. This pulsotype included isolates from many sources such as broiler chickens, poultry houses, slaughterhouses, other animal species (ducks, pigs and rodents) and humans, suggesting that it had already colonized every step of the food chain. Antibiotic susceptibility tests showed that most isolates were resistant to ampicillin, streptomycin, sulfonamides and tetracycline. The similarity of PFGE profiles of isolates from various sources and particularly from poultry and humans underlined possible transmission of Salmonella from contaminated broiler meat, but most of the isolates remained drug-sensitive. Significance and impact of study: Efforts are needed to eliminate Salmonella from poultry meat destined for human consumption. This study has also shown the importance of monitoring antimicrobial resistance in bacteria associated with animals and humans.

Horizontal Dissemination of Antimicrobial Resistance Determinants in Multiple Salmonella Serotypes following Isolation from the Commercial Swine Operation Environment after Manure Application

“…The pS24 plasmid isolated from S. enterica 4,12:i:Ϫ had a profile similar to that of S. Typhimurium plasmids, and the parent strain was also isolated from a different swine farm environment. During the last decade, S. enterica 1,4,12:i:Ϫ, 1,4, [5],12:i:Ϫ, and 4,12:i;Ϫ have emerged around the world and have frequently been isolated from human, animal, agricultural production, and environmental sources (37)(38)(39). These serotypes are believed to be a mosaic variant of S. Typhimurium and are related to plasmid-mediated colistin resistance encoded by the mcr-1 gene (37,39,81).…”