Multilocus Sequence Typing Supports the Hypothesis that Cow- and Human-Associated Salmonella Isolates Represent Distinct and Overlapping Populations

A collection of 179 human and 156 bovine clinical Salmonella isolates obtained from across New York state over the course of 1 year was characterized using serotyping and a multilocus sequence typing (MLST) scheme based on the sequencing of three genes (fimA, manB, and mdh). The 335 isolates were differentiated into 52 serotypes and 72 sequence types (STs). Analyses of bovine isolates collected on different farms over time indicated that specific subtypes can persist over time on a given farm; in particular, a number of farms showed evidence for the persistence of a specific Salmonella enterica serotype Newport sequence type. Serotypes and STs were not randomly distributed among human and bovine isolates, and selected serotypes and STs were associated exclusively with either human or bovine sources. A number of common STs were geographically widespread. For example, ST6, which includes isolates representing serotype Typhimurium as well as the emerging serotype 4,5,12:i:-, was found among human and bovine isolates in a number of counties in New York state. Phylogenetic analyses supported the possibility that serotype 4,5,12:i:- is closely related to Salmonella serotype Typhimurium. Salmonella serotype Newport was found to represent two distinct evolutionary lineages that differ in their frequencies among human and bovine isolates. A number of Salmonella isolates carried two copies of manB (33 isolates) or showed small deletion events in fimA (nine isolates); these duplication and deletion events may provide mechanisms for the rapid diversification of Salmonella surface molecules. We conclude that the combined use of an economical three-gene MLST scheme and serotyping can provide considerable new insights into the evolution and transmission of Salmonella.     

A Comparison of Non-Typhoidal Salmonella from Humans and Food Animals Using Pulsed-Field Gel Electrophoresis and Antimicrobial Susceptibility Patterns

Salmonellosis is one of the most important foodborne diseases affecting humans. To characterize the relationship between Salmonella causing human infections and their food animal reservoirs, we compared pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility patterns of non-typhoidal Salmonella isolated from ill humans in Pennsylvania and from food animals before retail. Human clinical isolates were received from 2005 through 2011 during routine public health operations in Pennsylvania. Isolates from cattle, chickens, swine and turkeys were recovered during the same period from federally inspected slaughter and processing facilities in the northeastern United States. We found that subtyping Salmonella isolates by PFGE revealed differences in antimicrobial susceptibility patterns and, for human Salmonella, differences in sources and invasiveness that were not evident from serotyping alone. Sixteen of the 20 most common human Salmonella PFGE patterns were identified in Salmonella recovered from food animals. The most common human Salmonella PFGE pattern, Enteritidis pattern JEGX01.0004 (JEGX01.0003ARS), was associated with more cases of invasive salmonellosis than all other patterns. In food animals, this pattern was almost exclusively (99%) found in Salmonella recovered from chickens and was present in poultry meat in every year of the study. Enteritidis pattern JEGX01.0004 (JEGX01.0003ARS) was associated with susceptibility to all antimicrobial agents tested in 94.7% of human and 97.2% of food animal Salmonella isolates. In contrast, multidrug resistance (resistance to three or more classes of antimicrobial agents) was observed in five PFGE patterns. Typhimurium patterns JPXX01.0003 (JPXX01.0003 ARS) and JPXX01.0018 (JPXX01.0002 ARS), considered together, were associated with resistance to five or more classes of antimicrobial agents: ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (ACSSuT), in 92% of human and 80% of food animal Salmonella isolates. The information from our study can assist in source attribution, outbreak investigations, and tailoring of interventions to maximize their impact on prevention.     

Substantial within-Animal Diversity of Salmonella Isolates from Lymph Nodes,Feces, and Hides of Cattle at Slaughter

Lymph nodes (mandibular, mesenteric, mediastinal, and subiliac; n = 68) and fecal (n = 68) and hide (n = 35) samples were collected from beef carcasses harvested in an abattoir in Mexico. Samples were analyzed for Salmonella, and presumptive colonies were subjected to latex agglutination. Of the isolates recovered, a subset of 91 was characterized by serotyping, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility phenotyping. Salmonella was isolated from 100% (hide), 94.1% (feces), 91.2% (mesenteric), 76.5% (subiliac), 55.9% (mandibular), and 7.4% (mediastinal) of samples. From the 87 typeable isolates, eight Salmonella enterica serotypes, including Kentucky (32.2%), Anatum (29.9%), Reading (17.2%), Meleagridis (12.6%), Cerro (4.6%), Muenster (1.1%), Give (1.1%), and Mbandaka (1.1%), were identified. S. Meleagridis was more likely (P = 0.03) to be recovered from lymph nodes than from feces or hides, whereas S. Kentucky was more likely (P = 0.02) to be recovered from feces and hides than from lymph nodes. The majority (59.3%) of the Salmonella isolates were pansusceptible; however, multidrug resistance was observed in 13.2% of isolates. Typing by PFGE revealed that Salmonella strains generally clustered by serotype, but some serotypes (Anatum, Kentucky, Meleagridis, and Reading) were comprised of multiple PFGE subtypes. Indistinguishable PFGE subtypes and, therefore, serotypes were isolated from multiple sample types, and multiple PFGE subtypes were commonly observed within an animal. Given the overrepresentation of some serotypes within lymph nodes, we hypothesize that certain Salmonella strains may be better at entering the bovine host than other Salmonella strains or that some may be better adapted for survival within lymph nodes. Our data provide insight into the ecology of Salmonella within cohorts of cattle and offer direction for intervention opportunities.     

Comparative Phenotypic and Genotypic Characterization of Salmonella spp. in Pig Farms and Slaughterhouses in Two Provinces in Northern Thailand

Salmonella spp. are an important group of bacterial zoonotic pathogens which can cause acute food-borne diseases in humans. Pork products are the main source of salmonellosis, but the origins and transmission routes of the disease have not been clearly determined. The purpose of this study was to characterize Salmonella spp. isolated in pig production lines both from pig farms and from slaughterhouses in Chiang Mai and Lamphun provinces in northern Thailand. The study focuses on the association among serotypes, antimicrobial resistance patterns and Pulse Field Gel Electrophoresis (PFGE) patterns to investigate possible sources of infection and to provide information which could help strengthen salmonellosis control programs in the region. A total of 86 strains of Salmonella comprising five majority serotypes were identified. Antibiotic resistance to tetracycline was found to be the most prevalent (82.56%) followed by ampicillin (81.40%) and streptomycin (63.95%). Seven clusters and 28 fingerprint-patterns generated by PFGE were identified among strains recovered from various locations and at different times, providing information on associations among the strains as well as evidence of the existence of persistent strains in some areas. Study results suggest that Salmonella control programs should be implemented at slaughterhouse production lines, including surveillance to insure good hygiene practices, in addition to regular monitoring of large populations of farm animals.     

Use of Pulsed-Field Gel Electrophoresis To Characterize the Heterogeneity and Clonality of Salmonella Isolates Obtained from the Carcasses and Feces of Swine at Slaughter

Salmonella enterica isolates were recovered from swine at a collaborating processing plant over a 2-month period in the spring of 2000. In the present study, molecular subtyping by pulsed-field gel electrophoresis (PFGE) was performed on the 581 confirmed Salmonella isolates from the 84 Salmonella-positive samples obtained from the previous study. A total of 32 different PFGE pulsotypes were observed visually, and a BioNumerics software analysis clustered those pulsotypes into 12 PFGE groups. The B, F, and G groups predominated throughout the sampling period and were isolated from 39, 22, and 13% of the swine, respectively. In addition, multiple isolates were obtained from 67 of the 84 Salmonella-positive samples, and subtyping revealed multiple PFGE profiles in 35 of these 67 (62%) samples. Both carcass and fecal isolates of Salmonella were recovered from 13 swine, resulting in “matched” samples. Molecular typing of the 252 isolates recovered from the matched samples revealed that 7 (54%) of the 13 carcasses were contaminated with Salmonella pulsotypes that were not isolated from the feces of the same animal. Conversely, from 6 of the 13 (46%) matched animals, Salmonella clonal types were isolated from the feces that were not isolated from the carcass of the same animal. These data establish that each lot of swine introduces new contaminants into the plant environment and that swine feces from one animal can contaminate many carcasses. In addition, these results indicate that the examination of multiple Salmonella isolates from positive samples is necessary to determine the variety of potential contaminants of swine carcasses during slaughter and processing.     

Prevalence and molecular subtyping of Blastocystis from dairy cattle in Kanagawa,Japan

Blastocystis is an intestinal protist, commonly found in the human population and in a wide range of animals globally. Currently, isolates from mammalian and avian hosts are classified into 17 subtypes (STs) based on phylogeny of the small subunit rRNA gene (SSU rDNA), of which ten (ST1-9, 12) are reported in humans. ST10 is a major ST reported from livestock cattle. However, other STs including ST1, 3, 4, 5, and 6, which have the potential to be transmitted to humans, are also reported from cattle in several countries. Although a survey has been conducted previously in western Japan for livestock cattle, there is no information available regarding other parts of Japan. Therefore, this study surveyed the prevalence of Blastocystis and its STs in cattle from Kanagawa prefecture, eastern Japan. Fecal specimens, collected from 133 dairy cattle on four different farms, were subjected to a short-term xenic in vitro culture and Blastocystis were identified by microscopic examination. Seventy-two cattle were positive for Blastocystis (54.1%). Direct sequences for the partial SSU rDNA were obtained for 45 samples. Based on nucleotide sequence homology search and phylogenetic analysis, 44 isolates were identified as ST14 and one as ST10. Our study confirms the presence of these STs in dairy cattle in Japan for the first time. The STs identified here, ST10 and ST14, support previous findings that Bovidae may be the natural host for both STs.     

Molecular Characterization of Motile Serovars of Salmonella enterica from Breeder and Commercial Broiler Poultry Farms in Bangladesh

Contaminated poultry and poultry products are a major source of motile Salmonellae for human salmonellosis worldwide. Local circulation of any motile Salmonella serovar in poultry has a wider public health impact beyond its source of origin for being dispersed elsewhere through poultry trades or human travels. To investigate the status of motile Salmonella serovars in breeder farms in Bangladesh, multiple flocks of two breeder farms were observed for a period of six months. In addition, a cross-sectional survey was carried out to determine the prevalence and serovar distribution of motile Salmonella by randomly selecting 100 commercial broiler poultry farms. Five pooled faecal samples representing an entire housed flock of breeders or broilers were screened for presence of motile Salmonella following conventional bacteriological procedures. The Salmonella isolates obtained were subsequently serotyped, and characterized by plasmid profiling and pulsed-field gel electrophoresis (PFGE). The results revealed that both the breeder farms were positive with three Salmonella serovars: S. Virchow, S. Paratyphi B var Java (S. Java) and S. Enteritidis. Eleven of the 100 broiler farms investigated were positive for motile Salmonella, giving a farm-level prevalence of 11% (95% confidence interval 5–17%). S. Virchow and S. Kentucky were the two predominant serovars isolated from the broiler farms. The PFGE genotyping demonstrated that the isolates belonging to the same serovars were closely related due to variation in only 1–4 bands. All the S. Virchow and S. Java isolates, irrespective of breeder or broiler farm origin, were plasmid-free, except for one S. Virchow isolate from a broiler farm that harboured a 9.7 kb-sized plasmid. The S. Kentucky isolates belonged to three plasmid profiles having plasmids of four different sizes, ranging from 2.7 to 109 kb. This is the first report of any motile Salmonella serovars from breeder and commercial broiler poultry farms in Bangladesh.     

Epidemiological relationships of <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> strains isolated from humans and chickens in South Korea

Thirty-nine human isolates of Campylobacter jejuni obtained from a national university hospital during 2007–2010 and 38 chicken isolates of C. jejuni were collected from poultry farms during 2009–2010 in South Korea were used in this study. Campylobacter genomic species and virulence-associated genes were identified by PCR. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to compare their genetic relationships. All isolates were highly resistant to ciprofloxacin, nalidixic acid, and tetracycline. Of all isolates tested, over 94% contained seven virulence associated genes (flaA, cadF, racR, dnaJ, cdtA, cdtB, and cdtC). All isolates were classified into 39 types by PFGE clustering with 90% similarity. Some chicken isolates were incorporated into some PFGE types of human isolates. MLST analysis for the 39 human isolates and 38 chicken isolates resulted in 14 and 23 sequence types (STs), respectively, of which 10 STs were new. STs overlapped in both chicken and human isolates included ST-21, ST-48, ST-50, ST-51, and ST-354, of which ST-21 was the predominant ST in both human and chicken isolates. Through combined analysis of PFGE types and STs, three chicken isolates were clonally related to the three human isolates associated with food poisoning (VII-ST-48, XXII-ST-354, and XXVIII-ST-51). They were derived from geographically same or distinct districts. Remarkably, clonal spread of food poisoning pathogens between animals and humans was confirmed by population genetic analysis. Consequently, contamination of campylobacters with quinolone resistance and potential virulence genes in poultry production and consumption may increase the risk of infections in humans.     

Clonal Dissemination of Escherichia coli O157:H7 Subtypes among Dairy Farms in Northeast Ohio

To ascertain the extent to which indistinguishable strains of Escherichia coli O157:H7 are shared between farms, molecular characterization was performed on E. coli O157:H7 isolates recovered during a longitudinal study of 20 dairy farms in northeast Ohio. Of the 20 dairy farms sampled, 16 were located in a primary area and 4 were located in two other distant geographical areas. A total of 92 E. coli O157:H7 isolates obtained from bovine fecal samples, water trough sediment samples, free-stall bedding, and wild-bird excreta samples were characterized. Fifty genetic subtypes were observed among the isolates using XbaI and BlnI restriction endonucleases. Most restriction endonuclease digestion profiles (REDPs) were spatially and temporally clustered. However, four REDPs from multiple sources were found to be indistinguishable by pulsed-field gel electrophoresis between four pairs of farms. The geographical distance between farms which shared an indistinguishable E. coli O157:H7 REDP ranged from 9 to 50 km, and the on-farm sources sharing indistinguishable REDPs included cattle and wild bird feces and free-stall bedding. Within the study population, E. coli O157:H7 REDP subtypes were disseminated with considerable frequency among farms in close geographic proximity, and nonbovine sources may contribute to the transmission of this organism between farms.     

Salmonella enterica Diversity in Central Californian Coastal Waterways

Salmonella enterica is one of the most important bacterial enteric pathogens worldwide. However, little is known about its distribution and diversity in the environment. The present study explored the diversity of 104 strains of Salmonella enterica isolated over 2 years from 12 coastal waterways in central California. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing were used to probe species diversity. Seventy-four PFGE patterns and 38 sequence types (STs) were found, including 18 newly described STs. Nineteen of 25 PFGE patterns were indistinguishable from those of clinical isolates in PulseNet. The most common ST was consistent with S. enterica serovar Typhimurium, and other frequently detected STs were associated with the serovars Heidelberg and Enteritidis; all of these serovars are important etiologies of salmonellosis. An investigation into S. enterica biogeography was conducted at the level of ST and subspecies. At the ST and subspecies level, we found a taxon-time relationship but no taxon-area or taxon-environmental distance relationships. STs collected during wet versus dry conditions tended to be more similar; however, STs collected from waterways adjacent to watersheds with similar land covers did not tend to be similar. The results suggest that the lack of dispersal limitation may be an important factor affecting the diversity of S. enterica in the region.     

Distributions of Salmonella Subtypes Differ between Two U.S. Produce-Growing Regions

Salmonella accounts for approximately 50% of produce-associated outbreaks in the United States, several of which have been traced back to contamination in the produce production environment. To quantify Salmonella diversity and aid in identification of Salmonella contamination sources, we characterized Salmonella isolates from two geographically diverse produce-growing regions in the United States. Initially, we characterized the Salmonella serotype and subtype diversity associated with 1,677 samples collected from 33 produce farms in New York State (NYS). Among these 1,677 samples, 74 were Salmonella positive, yielding 80 unique isolates (from 147 total isolates), which represented 14 serovars and 23 different pulsed-field gel electrophoresis (PFGE) types. To explore regional Salmonella diversity associated with production environments, we collected a smaller set of samples (n = 65) from South Florida (SFL) production environments and compared the Salmonella diversity associated with these samples with the diversity found among NYS production environments. Among these 65 samples, 23 were Salmonella positive, yielding 32 unique isolates (from 81 total isolates), which represented 11 serovars and 17 different PFGE types. The most common serovars isolated in NYS were Salmonella enterica serovars Newport, Cerro, and Thompson, while common serovars isolated in SFL were Salmonella serovars Saphra and Newport and S. enterica subsp. diarizonae serovar 50:r:z. High PFGE type diversity (Simpson''s diversity index, 0.90 ± 0.02) was observed among Salmonella isolates across both regions; only three PFGE types were shared between the two regions. The probability of three or fewer shared PFGE types was <0.000001; therefore, Salmonella isolates were considerably different between the two sampled regions. These findings suggest the potential for PFGE-based source tracking of Salmonella in production environments.     

High-Level Genotypic Variation and Antibiotic Sensitivity among Escherichia coli O157 Strains Isolated from Two Scottish Beef Cattle Farms

Escherichia coli O157:H7 is a human pathogen that is carried and transmitted by cattle. Scotland is known to have one of the highest rates of E. coli O157 human infections in the world. Two hundred ninety-three isolates were obtained from naturally infected cattle and the environment on two farms in the Scottish Highlands. The isolates were typed by pulsed-field gel electrophoresis (PFGE) with XbaI restriction endonuclease enzyme, and 19 different variations in patterns were found. There was considerable genomic diversity within the E. coli O157 population on the two farms. The PFGE pattern of one of the observed subtypes matched exactly with that of a strain obtained from a Scottish patient with hemolytic-uremic syndrome. To examine the stability of an individual E. coli O157 strain, continuous subculturing of a strain was performed 110 times. No variation from the original PFGE pattern was observed. We found three indistinguishable subtypes of E. coli O157 on both study farms, suggesting common sources of infection. We also examined the antibiotic resistance of the isolated strains. Phenotypic studies demonstrated resistance of the strains to sulfamethoxazole (100%), chloramphenicol (3.07%), and at a lower rate, other antibiotics, indicating the preservation of antibiotic sensitivity in a rapidly changing population of E. coli O157.     

Phenotypic and genotypic typing of<Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Enteritidis isolates from poultry farms environments in Tunisia

Salmonella enterica serovar Enteritidis is one of the majorSalmonella serovars which may cause animal infections and human salmonellosis. In this study, two hundred forty five samples (faeces, water and environmental swabs) were taken from eight poultry farms localized in different geographical areas of Tunisia. We foundSalmonella serovar Enteritidis (16 strains),Salmonella typhimirium (2),Salmonella scharzengrund (2), andSalmonella braenderup (1).Salmonella Enteritidis strains were characterized by pulsed field gel electrophoresis (PFGE) analysis, plasmid analysis and antibiotic resistance profiles.XbaI PFGE analysis revealed two PFGE types and plasmid profiling identified four plasmid types. The majority of isolates were susceptible to all antibiotic tested. The combined use of phenotypic and genotypic methods indicates the spread of a particularSalmonella Enteritidis clone. This clone is highly related to a major world-wide clone identified in many other countries.     

Genetic diversity and microevolution of Burkholderia pseudomallei in the environment

Background

The soil dwelling Gram-negative pathogen Burkholderia pseudomallei is the cause of melioidosis. The diversity and population structure of this organism in the environment is poorly defined.

Methods and Findings

We undertook a study of B. pseudomallei in soil sampled from 100 equally spaced points within 237.5 m² of disused land in northeast Thailand. B. pseudomallei was present on direct culture of 77/100 sampling points. Genotyping of 200 primary plate colonies from three independent sampling points was performed using a combination of pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Twelve PFGE types and nine sequence types (STs) were identified, the majority of which were present at only a single sampling point. Two sampling points contained four STs and the third point contained three STs. Although the distance between the three sampling points was low (7.6, 7.9, and 13.3 meters, respectively), only two STs were present in more than one sampling point. Each of the three samples was characterized by the localized expansion of a single B. pseudomallei clone (corresponding to STs 185, 163, and 93). Comparison of PFGE and MLST results demonstrated that two STs contained strains with variable PFGE banding pattern types, indicating geographic structuring even within a single MLST-defined clone.

Conclusions

We discuss the implications of this extreme structuring of genotype and genotypic frequency in terms of micro-evolutionary dynamics and ecology, and how our results may inform future sampling strategies.     

Head-to-Head Comparison of Two Multi-Locus Sequence Typing (MLST) Schemes for Characterization of Acinetobacter baumannii Outbreak and Sporadic Isolates

To compare the two Acinetobacter baumannii multi-locus sequence typing (MLST) schemes and to assess their suitability to aid in outbreak analysis we investigated the molecular epidemiology of 99 Acinetobacter baumannii isolates representing outbreak-related and sporadic isolates from 24 hospitals in four different countries (Germany, Poland, Sweden, and Turkey). Pulsed-field gel electrophoresis (PFGE) was used as the reference method to determine the epidemiologic relatedness of isolates and compared to MLST using both the Oxford and Pasteur scheme. Rep-PCR was used to define international clonal lineages (IC). We identified 26 unique outbreak strains and 21 sporadic strains. The majority of outbreaks were associated with carbapenem-resistant A. baumannii harbouring oxacillinase OXA-23-like and corresponding to IC 2. Sequence types (STs) obtained from the Oxford scheme correlate well with PFGE patterns, while the STs of the Pasteur scheme are more in accordance with rep-PCR grouping, but neither one is mirroring completely the results of the comparator. On two occasions the Oxford scheme identified two different STs within a single outbreak where PFGE patterns had only one band difference. The CCs of both MLST schemes were able to define clonal clusters that were concordant with the ICs determined by rep-PCR. IC4 corresponds to the previously described CC15 Pasteur (= CC103 Oxford). It can be concluded that both MLST schemes are valuable tools for population-based studies. In addition, the higher discriminatory power of the Oxford scheme that compares with the resolution obtained with PFGE can often aid in outbreak analysis.     

Arcobacter butzleri in Sheep Ricotta Cheese at Retail and Related Sources of Contamination in an Industrial Dairy Plant

This study aimed to evaluate Arcobacter species contamination of industrial sheep ricotta cheese purchased at retail and to establish if the dairy plant environment may represent a source of contamination. A total of 32 sheep ricotta cheeses (1.5 kg/pack) packed in a modified atmosphere were purchased at retail, and 30 samples were collected in two sampling sessions performed in the cheese factory from surfaces in contact with food and from surfaces not in contact with food. Seven out of 32 samples (21.9%) of ricotta cheese collected at retail tested positive for Arcobacter butzleri at cultural examination; all positive samples were collected during the same sampling and belonged to the same batch. Ten surface samples (33.3%) collected in the dairy plant were positive for A. butzleri. Cluster analysis identified 32 pulsed-field gel electrophoresis (PFGE) patterns. The same PFGE pattern was isolated from more than one ricotta cheese sample, indicating a common source of contamination, while more PFGE patterns could be isolated in single samples, indicating different sources of contamination. The results of the environmental sampling showed that A. butzleri may be commonly isolated from the dairy processing plant investigated and may survive over time, as confirmed by the isolation of the same PFGE pattern in different industrial plant surface samples. Floor contamination may represent a source of A. butzleri spread to different areas of the dairy plant, as demonstrated by isolation of the same PFGE pattern in different production areas. Isolation of the same PFGE pattern from surface samples in the dairy plant and from ricotta cheese purchased at retail showed that plant surfaces may represent a source of A. butzleri postprocessing contamination in cheeses produced in industrial dairy plants.     

Plasmid Profile and Pulsed–Field Gel Electrophoresis Analysis of Salmonella enterica Isolates from Humans in Turkey

This study was conducted for typing Salmonella enterica subspecies enterica strains in Turkey using pulsed–field gel electrophoresis (PFGE) and plasmid DNA profile analysis. Fourty-two strains were isolated from clinical samples obtained from unrelated patients with acute diarrhea. The samples were collected from state hospitals and public health laboratories located at seven provinces in different regions of Turkey at different times between 2004 and 2010. The strains were determined to belong to 4 different serovars. The Salmonella enterica strains belonged to the serovars Salmonella Enteritidis (n = 23), Salmonella Infantis (n = 14), Salmonella Munchen (n = 2), and Salmonella Typhi (n = 3). Forty-two Salmonella enterica strains were typed with PFGE methods using XbaI restriction enzyme and plasmid analysis. At the end of typing, 11 different PFGE band profiles were obtained. Four different PFGE profiles (type 1, 4, 9, and 10) were found among serotype S. Enteritidis species, 3 different PFGE profiles (type 3, 5, 6) were found among S. Infantis species, 2 different PFGE profiles were found among S. Typhi species (type 2 and 11), and 2 different PFGE profiles were found among S. Munchen species (type 7, 8). The UPGMA dendrogram was built on the PFGE profiles. In this study, it was determined that 4 strains of 42 Salmonella enterica strains possess no plasmid, while the isolates have 1–3 plasmids ranging from 5.0 to 150 kb and making 12 different plasmid profiles (P1–P12). In this study, we have applied the analysis of the PFGE patterns and used bioinformatics methods to identify both inter and intra serotype relationships of 4 frequently encountered serotypes for the first time in Turkey.     

Management practices as risk factors for the presence of bulk milk antibodies to Salmonella,Neospora caninum and Leptospira interrogans serovar hardjo in Irish dairy herds

A survey of management practices in 309 Irish dairy herds was used to identify risk factors for the presence of antibodies to Salmonella, Neospora caninum and Leptospira interrogans serovar hardjo in extensively managed unvaccinated dairy herds. A previous study documented a herd-level seroprevalence in bulk milk of 49%, 19% and 86% for Salmonella, Neospora caninum and leptospira interrogans serovar hardjo, respectively in the unvaccinated proportion of these 309 herds in 2009. Association analyses in the present study were carried out using multiple logistic regression models. Herds where cattle were purchased or introduced had a greater likelihood of being positive to leptospira interrogans serovar hardjo (P<0.01) and Salmonella (P<0.01). Larger herds had a greater likelihood of recording a positive bulk milk antibody result to leptospira interrogans serovar hardjo (P<0.05). Herds that practiced year round calving were more likely to be positive to Neospora caninum (P<0.05) compared to herds with a spring-calving season, with no difference in risk between herds that practiced split calving compared to herds that practiced spring calving. No association was found between presence of dogs on farms and prevalence of Neospora caninum possibly due to limited access of dogs to infected materials including afterbirths. The information from this study will assist in the design of suitable control programmes for the diseases under investigation in pasture-based livestock systems.     

Diversity and Antimicrobial Resistance of Salmonella enterica Isolates from Surface Water in Southeastern United States

A study of prevalence, diversity, and antimicrobial resistance of Salmonella enterica in surface water in the southeastern United States was conducted. A new scheme was developed for recovery of Salmonella from irrigation pond water and compared with the FDA''s Bacteriological Analytical Manual (8th ed., 2014) (BAM) method. Fifty-one isolates were recovered from 10 irrigation ponds in produce farms over a 2-year period; nine Salmonella serovars were identified by pulsed-field gel electrophoresis analysis, and the major serovar was Salmonella enterica serovar Newport (S. Newport, n = 29), followed by S. enterica serovar Enteritidis (n = 6), S. enterica serovar Muenchen (n = 4), S. enterica serovar Javiana (n = 3), S. enterica serovar Thompson (n = 2), and other serovars. It is noteworthy that the PulseNet patterns of some of the isolates were identical to those of the strains that were associated with the S. Thompson outbreaks in 2010, 2012, and 2013, S. Enteritidis outbreaks in 2011 and 2013, and an S. Javiana outbreak in 2012. Antimicrobial susceptibility testing confirmed 16 S. Newport isolates of the multidrug resistant-AmpC (MDR-AmpC) phenotype, which exhibited resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (ACSSuT), and to the 1st, 2nd, and 3rd generations of cephalosporins (cephalothin, amoxicillin-clavulanic acid, and ceftriaxone). Moreover, the S. Newport MDR-AmpC isolates had a PFGE pattern indistinguishable from the patterns of the isolates from clinical settings. These findings suggest that the irrigation water may be a potential source of contamination of Salmonella in fresh produce. The new Salmonella isolation scheme significantly increased recovery efficiency from 21.2 (36/170) to 29.4% (50/170) (P = 0.0002) and streamlined the turnaround time from 5 to 9 days with the BAM method to 4 days and thus may facilitate microbiological analysis of environmental water.     

Antimicrobial Resistance in Escherichia coli Isolates from Swine and Wild Small Mammals in the Proximity of Swine Farms and in Natural Environments in Ontario, Canada

Wild animals not normally exposed to antimicrobial agents can acquire antimicrobial agent-resistant bacteria through contact with humans and domestic animals and through the environment. In this study we assessed the frequency of antimicrobial resistance in generic Escherichia coli isolates from wild small mammals (mice, voles, and shrews) and the effect of their habitat (farm or natural area) on antimicrobial resistance. Additionally, we compared the types and frequency of antimicrobial resistance in E. coli isolates from swine on the same farms from which wild small mammals were collected. Animals residing in the vicinity of farms were five times more likely to carry E. coli isolates with tetracycline resistance determinants than animals living in natural areas; resistance to tetracycline was also the most frequently observed resistance in isolates recovered from swine (83%). Our results suggest that E. coli isolates from wild small mammals living on farms have higher rates of resistance and are more frequently multiresistant than E. coli isolates from environments, such as natural areas, that are less impacted by human and agricultural activities. No Salmonella isolates were recovered from any of the wild small mammal feces. This study suggests that close proximity to food animal agriculture increases the likelihood that E. coli isolates from wild animals are resistant to some antimicrobials, possibly due to exposure to resistant E. coli isolates from livestock, to the resistance genes of these isolates, or to antimicrobials through contact with animal feed.