November 01, 2013


 Pathogen’s drug resistance varied across species in study

A study in the U.K. found that drug resistance patterns among Salmonella enterica Typhimurium DT104 isolates from humans differed from those isolated from livestock.

Officials with the Wellcome Trust Sanger Institute, a genomic research organization, announced in September that genetic variation and differences in drug resistance were found among 373 S Typhimurium isolates obtained from 1990-2011, mostly in Scotland, indicating that humans and livestock had separate populations of such bacteria. Those bacterial populations were more varied than expected, and domesticated animals may not be the primary source of antimicrobial-resistant Salmonella organisms that infects humans, the announcement states.

The announcement cites a scientific article, “Distin­guished Epidemics of Multidrug-Resistant Salmonella Typhimurium DT104 in Different Hosts,” which was published Sept. 27 (Science 2013;341:1514-1517).

The article indicates that multidrug-resistant S Typhimurium DT104 caused a global epidemic in humans and animals throughout the 1990s, and animal populations were thought to be the primary source of infections in humans, through food and through contact between people and livestock.

The authors used whole-genome sequencing to examine the relationships among 142 isolates collected from humans and 120 isolates from animals in Scotland, as well as 111 isolates from other countries. The article indicates antimicrobial resistance, abbreviated in the article as “AMR,” was more diverse in the human population, and isolate transmission appeared to occur within each host population, with little spillover in either direction.

“With humans having a more diverse source of infections than the local animal population, it is probably that imported food, foreign travel, and environmental reservoirs are significant sources of Salmonella and AMR in humans in our study,” the article states.