Comparative phenotypic and genotypic analyses of Salmonella Rissen that originated from food animals in Thailand and United States.

Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready-to-eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby-Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse-field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan-susceptible and roughly 30% were resistant to only tetracycline (R-type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter-regional transmission and dissemination is warranted.

A cross-sectional study of hepatitis E virus infection in healthy people directly exposed and unexposed to pigs in a rural community in northern Thailand.

A cross-sectional study of the association between occupational pig exposure and hepatitis E virus (HEV) infection in adult pig farmers and the general population who were not directly exposed to pigs was conducted in Nan Province, Thailand, from November 2010 to April 2011. All participants were interviewed to provide information on their job history, eating habits and other potential confounders. The prevalence of anti-HEV immunoglobulin G antibodies (IgG) among 513 subjects was 23.0%. Hand washing with water and soap was associated with a lower seroprevalence of HEV infection, whereas living in an area with frequent flooding (OR 1.64, 95% CI: 1.00-2.68) and consuming internal pig organs more than twice per week (OR 3.23, 95%CI: 1.15-9.01) were both associated with a higher seroprevalence of anti-HEV IgG. There was no association between HEV seroprevalence and frequent, direct occupational pig contact.

Prevalence, quantitative load, and antimicrobial resistance of Campylobacter spp. from broiler ceca and broiler skin samples in Thailand.

This study was conducted to determine the prevalence of Campylobacter spp. in broiler flocks by testing cecal contents at slaughter and to detect and quantify Campylobacter on broiler carcass skin samples of the corresponding slaughter batches, to determine antimicrobial resistance patterns of the Campylobacter isolates, and to genotype selected Campylobacter jejuni isolates using multilocus sequence typing analysis. Ninety-eight broiler flocks were included in the study. Intact ceca were randomly taken at the time of evisceration throughout a slaughter batch to detect Campylobacter spp. at the broiler flock level and one whole carcass per slaughter batch was taken for the detection of Campylobacter spp. on broiler skin. The prevalences of Campylobacter spp. in broiler ceca and broiler skin samples were 11.2% (11/98) and 51% (50/98), respectively. Even though most Campylobacter-positive broiler skin samples were contaminated with only up to 230 most probable number per gram, a substantial share (13.3%) showed very high Campylobacter numbers on the broiler skin samples (most probable number = ∞; lower confidence limit T(0) 580/g). From 32 C. jejuni and Campylobacter coli isolates tested, the highest antimicrobial resistance rates were found for ciprofloxacin (81.2%), followed by tetracycline (40.6%), ampicillin (31.2%), and erythromycin (9.4%). All tested strains were sensitive to gentamicin. By multilocus sequence typing analysis, a total of 9 different sequence types were identified among 16 C. jejuni isolates. Campylobacter jejuni isolated from cecal content and carcass skin of the same farm or slaughter batch showed corresponding allelic profiles. Our data suggest that intense cross-contamination during the slaughter process led to a strong increase of Campylobacter prevalence on broiler skin compared with the prevalence in broiler ceca. To reduce Campylobacter prevalences on broiler skin, on-farm biosecurity measures need to be accompanied by control measures at the slaughterhouse to reduce fecal contamination of broiler skin and to minimize cross-contamination.

Antimicrobial resistance and genotypic characterization of coagulase-negative staphylococci over the dry period.

Coagulase-negative staphylococci (CNS) have become the most frequently isolated organisms from bovine intramammary infections in recent years. While antimicrobial resistance (AR) is not considered a major problem among mastitis pathogens, concerns over emerging AR in general are increasing worldwide. Little information exists about the association between AR and one of the most common mastitis control measures, antibiotic dry cow therapy. The primary objective of the current study was to determine the prevalence of AR in CNS isolated before and after antimicrobial dry cow therapy. An additional objective was to genotypically characterize selected CNS isolates using pulsed-field gel electrophoresis (PFGE), to assess diversity and persistence of organisms over the dry period. Resistance against 10 antimicrobials was determined using a broth microdilution method and compared between CNS isolates collected at dry-off and at calving and from cows treated or not treated with intramammary antimicrobial products at dry-off (752 cows in total). Results suggested that increasing age of a cow and dry cow treatment when combined with high milk somatic cell count at dry-off and positive clinical mastitis history, were associated with increased AR to most beta-lactam antimicrobials and sulfadimethoxine. PFGE results suggested considerable diversity among the tested isolates as well as some clusters within cows and herds. PFGE would be useful in distinguishing between potentially persisting infections and cures and reinfections with different CNS strains.