German researchers have isolated a strain of Salmonella in pork that is closely related to the bacteria commonly found in chickens and linked to human food-borne illness. They report their findings in the July 2010 issue of the journal Applied and Environmental Microbiology.
First emerging overseas in the mid-1990's in pigs, initial studies showed the genetic make-up of Salmonella enterica subsp. enterica serovar Typhimurium (or S. enterica serovar 4,,12:i:-) to be very similar to S. enterica serovar Typhimurium, the strain commonly found in chickens. It is a known cause of gastroenteritis and has become increasingly associated with worldwide outbreaks over the last few years.
"Interestingly, the number of S. enterica serovar 4, ,12:i:- strains isolated from humans and sent on voluntary basis to the National Reference Centre for Salmonella and other Enterics increased from 0.1% in 1999 to 14.0% in 2008," say the researchers.
In the study researchers collected and analyzed strains of S. enterica serovar 4,,12:i:-from pigs, pork, and humans over a two-year period in an attempt to better understand its transmission capabilities. Additionally, the strains' genetic relatedness, pathogenicity and antimicrobial resistance were compared to that of S. enterica serovar Typhimurium. Two major clonal lineages were observed among the two strains and 65% of isolates from both lineages were resistant to ampicillin, streptomycin, tetracycline and sulfamethoxazole.
"Overall the study indicates that in Germany S. enterica serovar 4, ,12:i:- strains isolated from pig, pork, and human are highly related, showing their transmission along the food chain," say the researchers. "Since the pathogenicity gene repertoire is highly similar to that of S. enterica serovar Typhimurium, it is essential that interventions are introduced at the farm level in order to limit human infection."
(E. Hauser, E. Tietze, R. Helmuth, E. Junker, K. Blank, R. Prager, W. Rabsch, B. Appel, A. Fruth, B. Malorny. 2010. Pork contaminated with Salmonella enterica serovar 4, , 12:i:-, an emerging health risk for humans. Applied and Environmental Microbiology, 76. 14: 4601-4610.)