In vivo passage of Salmonella Typhimurium results in minor mutations in the bacterial genome and increases in vitro invasiveness

AbstractEggs and raw or undercooked egg-containing food items are frequently identified as the bacterial source during epidemiolocal investigation ofSalmonella outbreaks. Multi-locus variable number of tandem repeats analysis (MLVA) is a widely usedSalmonella typing method enabling the study of diversity within populations of the same serotype. In vivo passage, however, has been linked with changes in MLVA type and more broadly theSalmonella genome. We sought to investigate whether in vivo passage through layer hens had an effect on MLVA type as well as the bacterial genome and whether any mutations affected bacterial virulence. Layer hens were infected with eitherSalmonella Typhimurium DT9 (03-24-11-11-523) as part of a single infection or were co-infected with an equal amount ofSalmonella Mbandaka.Salmonella shedding in both single and co-infected birds was variable over the course of the 16-week experiment.Salmonella Typhimurium andSalmonella Mbandaka were identified in feces of co-infected birds.Salmonella colonies isolated from fecal samples were subtyped using MLVA. A single change in SSTR-6 was observed inSalmonella Typhimurium strains isolated from co-infected birds. Isolates ofSalmonella Typhimurium of both the parent (03-24-11-11-523) and modified (03-24-12-11-523) MLVA type were sequenced and compared with the genome of the parent strain. Sequence analysis revealed that in vivo passaging resulted in minor mutation events. Passaged isolates exhibited significantly h...
Source: Veterinary Research - Category: Veterinary Research Source Type: research