Molecular epidemiological analysis and microbial source tracking of Salmonella enterica serovars in a preharvest turkey production environment.

Epidemiological studies were conducted to source track and delineate horizontal transmission pathways of Salmonella serovars in a turkey production environment. Salmonella enterica serovar Heidelberg (n = 111), Salmonella Senftenberg (n = 14), Salmonella Muenster (n = 10), unidentifiable "roughs" (n = 5), Salmonella Anatum (n = 3), and Salmonella Worthington (n = 2) were isolated from the birds' cecal and crop contents, litter, environmental swabs, drinkers, and feed samples. These strains (n = 145) were analyzed for their antimicrobial susceptibility profiles and the bacterial horizontal transmission pathways were tracked by XbaI-digested pulsed-field gel electrophoresis (PFGE) macrorestriction profiles. Nearly 79% of the strains were resistant to one or more antimicrobials, while 44% of the strains were resistant to two to six antimicrobials. Nearly 21% of the strains were susceptible to all of the antimicrobials tested. Twenty-seven distinct PFGE fingerprint profiles (90-95% similarity) were observed among 110 Salmonella Heidelberg strains (one strain was untypeable), and 13 of the 27 profiles (48%) elicited 100% similarity among the fingerprint patterns. The prevalence of Salmonella Heidelberg strains at weeks 2 (n = 20), 10 (n = 20), and 18 (n = 70) among the sampled pens suggested cross-colonization among pens during the 20-week production cycle. Salmonella Heidelberg strains were first isolated from the birds at week 2, and identical fingerprint profiles of this serovar were subsequently isolated from birds within the same pen; birds in other pens; and litter, air, and swab samples at weeks 10 and 18, suggesting possible horizontal transmission of this serovar across the production facility during the grow-out period.