Pulsed-Field Gel Electrophoresis Diversity of Human and Bovine ClinicalSalmonellaIsolates

Abstract

Pulsed-field gel electrophoresis (PFGE) characterization of 335 temporally and spatially matched clinical, bovine, and human Salmonella enterica subsp. enterica isolates revealed 167 XbaI PFGE patterns. These isolates were previously classified into 51 serotypes and 73 sequence types, as determined by multilocus sequence typing. Discriminatory power of PFGE (Simpson's index, D ¼ 0.991) was considerably higher than that of multilocus sequence typing (D ¼ 0.920) or serotyping (D ¼ 0.913). Although 128 PFGE types each only represented a single isolate, 8 PFGE types represented >4 isolates, including (i) three serotype Enteritidis and Heidelberg patterns that were only identified among human isolates, (ii) two PFGE patterns (each representing serotypes Bardo and Newport) that were significantly more common among bovine isolates as compared with human isolates; (iii) two PFGE types that each includes two serotypes (4,5,12:i:-and Typhimurium; Thompson and 1,7:-:1,5); and (iv) one PFGE type that includes eight Typhimurium isolates from humans and cattle. Characterization of isolates collected over multiple farm visits indicated that given specific PFGE types persisted over time on 11 farms. On an additional seven farms, isolates with a given sequence type represented multiple PFGE type, which typically only differed by <3 bands, suggesting PFGE type diversification during strain persistence. Sixteen PFGE types were isolated from 2 or more farms, including two widely distributed serotype Newport-associated PFGE types each found on 10 farms. In six instances two or three human isolates collected in the same county in the same or consecutive months represented the same subtypes, suggesting small human case clusters. PFGE-based characterization and surveillance of human and animal isolates can provide improved understanding of Salmonella diversity and epidemiology, including identification of possible host-associated and common, widely distributed PFGE types.

Genotyping and study of the pauA and sua genes of Streptococcus uberis isolates from bovine mastitis

“…The analysis of the 137 isolates revealed 61 types of PFGE patterns, 29 of which were unique isolates, and 32 types, containing 2---8 isolates per type. Isolate distribution in groups was: 19 types with 2 isolates (PF 04, 9,11,12,15,16,18,21,23,25,27,37,43,45,46,47,55, 56 and 57), 5 types with 3 isolates (PF 13, 19, 32, 33 and 40), 5 types with 4 isolates (PF 20, 31, 34, 35 and 39), 2 types with 6 isolates (PF14 and PF29) and 1 type with 8 isolates (PF1) ( Table 1). Genotype grouping appeared to be neither related to the mastitis type (clinical or subclinical) nor to the farm origin.…”

“…PFGE is the most discriminatory method for typing bacteria 22 , whereas RAPD is a more straightforward method given its relatively lower costs, execution time demanded, less expensive equipment requirements and sensitivity. Both methods have been widely used to study the genetic variability of many bacterial species, including important human pathogens 22,37 .…”

Within-Farm Changes in Dairy Farm-Associated Salmonella Subtypes and Comparison to Human Clinical Isolates in Michigan, 2000-2001 and 2009

“…Salmonella found on dairy farms could be transmitted through contamination and inadequate pasteurization of dairy products, contamination of carcasses and lymph nodes (cull dairy cattle), or indirect transmission through the environment. There is substantial overlap in the antimicrobial resistance (AMR) phenotypes, serotypes, and pulsed-field gel electrophoresis (PFGE) patterns of Salmonella strains recovered from dairy cattle and those that cause disease in humans (5)(6)(7). In general, a diverse population of Salmonella serotypes are recovered from cattle, but only a small number of serotypes account for the majority of illnesses.…”

Antibiotic Resistance in Salmonella enterica Serovar Typhimurium Associates with CRISPR Sequence Type

“…These methods differ greatly in their resolution and are often combined in order to unravel phylogenetic and epidemiologically relevant relationships among strains. For instance, a recent study by Soyer et al used a combination of PFGE and MLST to identify overlapping populations of S. Typhimurium from bovine and human sources (6). Several MLST subtypes were found repeatedly on the same farms over time, but PFGE patterns from these isolates showed diversification, suggesting that PFGE might not be an appropriate method for monitoring the persistence of clonal populations.…”