Differences in immune responses of pigs vaccinated with Salmonella Typhimurium and S. Choleraesuis strains and challenged with S. Choleraesuis

S. Choleraesuis (Choleraesuis) and S. Typhimurium (Typhimurium) cause salmonellosis in pigs and humans. The effects of vaccine strains pSV-less Typhimurium OU5048 and Choleraesuis OU7266 and SPI-2-mutant Choleraesuis SC2284 on the immune responses of pigs against Typhimurium, Choleraesuis, and S. Enteritidis (Enteritidis) with or without the virulence plasmid (pSV) were determined. After oral vaccination of three vaccine groups and challenge with Choleraesuis CN36, the level of Salmonella-specific IgG in sera and the bactericidal effects and superoxide generation of peripheral blood mononuclear cells (PBMCs) and polymorphonuclear leukocytes (PMNs) against the above strains were determined using ELISA and NBT assay, respectively. Among three vaccine strains tested, OU7266 stimulated the highest Salmonella-specific IgG levels. Complement inactivation increased IgG concentration, while E. coli absorption reduced IgG levels. The pSV-containing strains were less resistant to serum killing than the pSV-less strains, and Enteritidis exhibited the lowest resistance to serum killing. Serovars tested, vaccine strains, and timeline periods postvaccination and challenge were important factors affecting superoxide production. The two Choleraesuis vaccine strains stimulated greater levels of superoxide from PMNs and PBMCs than the Typhimurium strains. The PMNs and PBMCs in challenged and vaccinated pigs reduced more superoxide than those in challenged hosts. In vaccinated hosts, pSV-less Salmonella strains triggered lower levels of PMN/PBMC-generated superoxide upon challenge than strains with pSV against Enteritidis and Choleraesuis. Overall, Choleraesuis OU7266 may be better than the other vaccine strains in generating the greatest IgG levels, serum bactericidal activity and superoxide levels. The pSV likely influences the immune responses.     

Molecular typing and antimicrobial resistance of Salmonella enterica subspecies enterica serovar Choleraesuis isolates from diseased pigs in Japan

Salmonella enterica serovar Choleraesuis (S. Choleraesuis) isolates derived from diseased pigs in Japan during 2001 and 2005 were analyzed for biotype, based on H(2)S production and dulcitol fermentation, pulsed-field gel electrophoresis (PFGE) profile, and antimicrobial resistance profile. S. Choleraesuis biotype Choleraesuis (biotype Choleraesuis) was classified into one genotype, while varietas Kunzendorf (var. Kunzendorf) was classified into two genotypes. The isolates of var. Kunzendorf belonging to one genotype were isolated in a limited area of Japan. Variation in the antimicrobial resistance pattern was observed in isolates of both biotypes Choleraesuis and var. Kunzendorf. We have also shown that the PFGE profile was associated with the biotype and isolation region of each isolate.     

Use of an avirulent live Salmonella Choleraesuis vaccine to reduce the prevalence of Salmonella carrier pigs at slaughter

This study evaluated the use of an avirulent live Salmonella Choleraesuis vaccine to reduce the seroprevalence and number of Salmonella carrier pigs at slaughter. Seven batches of 500 pigs were included in each of the two study groups: the vaccinated group (VG) that was orally vaccinated and the control group (CG) that received a placebo on the first day of life. The groups were managed in a three-site system and followed up from birth to slaughter. Blood samples (n=378) were collected from each VG and CG to monitor the on-farm seroprevalence in both groups. Mesenteric lymph nodes and blood from animals (n=390) belonging to each group were collected at slaughter. At the first day of life, the seroprevalence in control batches ranged from 77.9 to 96.3 per cent, while in vaccinated batches, it ranged from 66.6 to 92.6 per cent. At weaning (21 days of age), the number of seropositives decreased in both groups (mean of 12 and 3.7 per cent for CG and VG, respectively). At slaughter, batches of VG had a significantly (P<0.0001) lower seroprevalence (46.6±5 per cent) and isolation of Salmonella from lymph nodes (33.1±5 per cent) compared with CG batches (79.7±4 per cent and 59.5±5 per cent, respectively). The results indicate that administration of a Salmonella choleraesuis-attenuated vaccine on the first day of life decreases Salmonella isolation and seroprevalence in pigs at slaughter.     

Evaluation of cross-protection afforded by a Salmonella Choleraesuis vaccine against Salmonella infections in pigs under field conditions

This field study investigated the efficacy of a Salmonella Choleraesuis live vaccine (Argus SC) to reduce the number of infections with Salmonella. Twelve groups of about 380 pigs each were randomly allocated to either vaccination (V) or no vaccination (C). The vaccine was applied orally at 3 and 16 weeks. Forty pigs per group were blood sampled at 3, 10, 16, and 24 weeks to detect possible antibodies against Salmonella. The prevalence of Salmonella in the lymph nodes was the major variable. In the V groups, only 0.6% of the lymph nodes were positive, whereas 7.2% were positive in the C groups (p < 0.001). The percentage of seropositive pigs at 24 weeks (cut-off OD > 10) was 26% and 9% in the V and C groups, respectively (p < 0.001). The present study documented that vaccination with a live modified S. Choleraesuis vaccine is a useful tool to lower the prevalence of Salmonella in swine herds.     

Virulence of Salmonella enteritidis phagetypes 4, 8 and 13 and other Salmonella spp. for day-old chicks, hens and mice.

Virulence of three Canadian poultry strains of Salmonella enteritidis, namely phagetypes (PT) 4, 8 and 13, and one Salmonella heidelberg strain was assessed in orally and intraperitoneally inoculated one-day old chickens and compared to the virulence of a human S. enteritidis PT 4 strain from the United Kingdom (UK). The two PT 4 strains were also compared in orally inoculated adult laying hens. In addition, orally inoculated Balb/c mice were used to evaluate virulence of the above strains and two strains of Salmonella typhimurium containing different plasmids. In orally inoculated one-day old chickens, the UK S. enteritidis PT 4 strain was more virulent than the Canadian PT 4 strain. The UK PT 4 strain was also more virulent and invasive in adult laying hens than the Canadian PT 4 strain. The S. enteritidis PT 8 strain and one S. typhimurium strain isolated from a chicken hatchery were the most virulent for orally inoculated Balb/c mice. This strain of S. typhimurium contained the 60 megadalton plasmid associated with virulence for Balb/c mice which was not present in the S. typhimurium strain isolated from a pig with septicemic disease.     

Contribution of enhanced efflux to reduced susceptibility of Salmonella enterica serovar Choleraesuis to fluoroquinolone and other antimicrobials

We examined antimicrobial susceptibility and efflux systems in laboratory-derived mutants of Salmonella enterica serovar Choleraesuis selected by culture on fluoroquinolone-containing plates. The mutants exhibited decreased susceptibilities to quinolones and several other antimicrobials. Mutations in the gyrA gene were not always found in the mutants. Accumulation assays revealed that intracellular enrofloxacin concentrations were significantly lower in the mutants compared with parent isolates. Increased expression of acrB mRNA can explain the decreased susceptibilities to several antimicrobials but not in the case of carbonyl cyanide m-chlorophenylhydrazone (CCCP). Decreased susceptibility to CCCP may result from the increased expression of emrA mRNA. These results suggest that the enhancement of multiple efflux pumps is responsible for decreased susceptibilities to several antimicrobials in the laboratory-derived mutants.     

Risk factors for Salmonella spp in Portuguese breeding pigs using a multilevel analysis

Salmonella is the second most frequent cause of foodborne illness in the European Union (EU), so EU enforced legislation to achieve a reduction in Salmonella prevalence in the swine sector. To set the reduction target each country carried out a baseline survey to estimate Salmonella prevalence. The aim of our study was to identify risk factors for the presence of Salmonella in breeding pigs based on the data of the Baseline Study for Salmonella in Breeding Pigs in Portugal. In total, 1670 pen fecal samples from 167 herds were tested by culture and 170 samples tested positive. Along with the collection of the samples a survey was applied to collect information about the herd management and potential risk factors. Multilevel analysis was applied to the data using generalized linear mixed models and a logit link function. The outcome variable was the presence/absence of Salmonella in the pen fecal samples. The first level was assigned to the pen fecal samples and the second level to the herds. The results showed significant associations between Salmonella occurrence and the factors (p < 0.05): maternity pens versus mating pens (OR = 0.39, 95%CI: 0.24–0.63), feed from external or mixed source versus home source (OR = 2.81, 95%CI: 1.19–6.61), more than 10 animals per pen versus 10 animals per pen (OR = 2.02, 95%CI: 1.19–3.43), North Region versus Alentejo Region (OR = 3.86, 95%CI: 1.08–13.75), rodents control (OR = 0.23, 95%CI: 0.090–0.59), more than 90% of boars homebred or no boars versus more than 90% of boars from an external source (OR = 0.54, 95%CI: 0.3–0.97), semen from another herd versus semen from insemination centers (OR = 4.47, 95%CI: 1.38–14.43) and herds with a size of 170 or more sows (OR = 1.82, 95%CI: 1.04–3.19). This study offers very relevant information for both the Portuguese veterinary authorities and the pig farmers currently developing control programmes for Salmonella. This is the first study providing evidence for semen and boars source as risk factors for Salmonella in breeding pigs.     

Accuracy of two commercial enzyme-linked immunosorbent assays for the detection of antibodies to Salmonella spp. in slaughter pigs from Canada

Large discrepancies are usually found when different ELISAs for the diagnosis of pig salmonellosis are compared. Thus, our main goal was to estimate the diagnostic accuracy through Bayesian approaches of two commercial assays (Svanovir™ “test A” and HerdCheck™ “test B”) for the detection of antibodies to Salmonella spp. in slaughter pigs. Previously, we estimated the agreement between both tests and their relative sensitivity (Se) and specificity (Sp) with respect to bacteriology on caecal content and ileocaecal lymph nodes. Test A, at a cut-off OD% ≥20%, indicated higher prevalence than test B (OD% ≥10%) (14.6% vs. 8.6%). Relative Se with respect to overall bacteriology was low (≈30%) and similar for both tests, but the relative Sp was significantly lower for test A compared to B (88% vs. 95%). Both tests failed to detect some pigs infected with Salmonella serogroups B and C₁, which they were supposed to identify. In general, tests showed only fair-to-moderate agreement when they were compared (kappa: 0.41). In the Bayesian models, Se of test A varied between 63% and 77%, while Se of test B was 73%. Sp of A was always lower than that of test B (89% vs. 95%). The implications derived from the use of these imperfect serological tests will have to be accounted for in large-scale Salmonella-control programs.     

Differential molecular identification of Taeniid spp. and Sarcocystis spp. cysts isolated from infected pigs and cattle

In the present work, the species-specific identification of Taeniid spp. cysticerci and sarcocystis cysts isolated from infected pigs and cattle was achieved by PCR. In particular: (i) multiplex-PCR derived from HDP2 DNA fragment, specific for Taenia saginata/Taenia solium; (ii) PCRs and PCR-RFLPs of the rDNA internal transcribed spacers 1 and 2 (ITS1 and ITS2) for the differential diagnosis of taeniids; (iii) PCR derived from the 18S rRNA gene and sequencing, specific for Sarcoystis spp. The combined application of these three PCR protocols provided an unequivocally specific diagnosis of T. saginata, T. solium, T. hydatigena, Sarcocystis hominis and Sarcocystis suihominis, and may have practical application in the identification of calcified degenerating or morphologically dubious cysts, for example in the slaughter house situation or in human biopsy samples.     

Prevalence of Salmonella spp. in pigs, chickens and ducks in the Mekong Delta, Vietnam

In order to determine the prevalence of Salmonella spp. in domestic animals in 6 provinces of the Mekong Delta, Vietnam, 1,098 fecal or intestinal content samples from pigs, chickens, and ducks were examined in the period from July to October, 2000. Salmonella spp. were isolated from 78 (7.1%) of the total samples, which included 23 (5.2%) of 439 pigs, 24 (7.9%) of 302 chickens, and 31 (8.7%) of 357 ducks. From those samples, 80 Salmonella strains were isolated and 25 serovars were identified. The predominant serovars were S. Javiana, S. Derby, and S. Weltevreden. S. Javiana and S. Weltevreden were detected together in pigs, chickens, and ducks. These results indicate that the serovars of Salmonella are widely distributed in domestic animals in the Mekong Delta, Vietnam.     

Sensitivity and specificity of different methods for the isolation of Salmonella from pigs.

Three different selective enrichment media, Rappaport-Vassiliadis broth (RV), selenite broth (SB) and Müller-Kauffmann tetrathionate broth (MKTB), in combination with plating on modified brilliant green agar (BGA), were compared for the isolation of Salmonella from samples of pig feces. These conventional methods were also compared with a new ELISA kit in conjunction with RV and SB enrichment. Of the conventional methods, enrichment in RV had a higher sensitivity and selectivity than SB and MKTB. Recovery of S. typhimurium from MKTB was significantly poorer than recovery of other serotypes. The combination of RV enrichment and ELISA was as good as the conventional method involving RV enrichment, with a similar high sensitivity and specificity.     

Salmonella enteritidis and other Salmonella in laying hens and eggs from flocks with Salmonella in their environment.

Seven Canadian layer flocks with Salmonella enteritidis in their environment were investigated to determine the numbers of hens infected with S. enteritidis, the localization of S. enteritidis in organs of infected hens and the numbers of S. enteritidis-infected eggs produced by two affected flocks. By a microagglutination test (MAT) using S. pullorum antigens, these flocks had more seropositive hens (mean 51.9 +/- 16.9%) than two Salmonella-free flocks (mean 13.0 +/- 4.2%). Culture of tissues of 580 hens (433 seropositive) from the seven flocks detected 26 (4.5%) S. enteritidis-infected hens from two flocks. In one flock, 2/150 hens were infected with S. enteritidis phage type (PT) 8, which was confined to the ceca, and no Salmonella spp. were isolated from 2520 eggs (one day's lay). In the second flock, where 24/150 hens were infected with S. enteritidis PT13, extraintestinal infection was found in nine hens and involved the ovaries and/or oviduct in two hens. Salmonella enteritidis PT13 was isolated from one sample of egg contents and from one sample of cracked shells from among 14,040 eggs (one day's lay) from this flock. The overall prevalence of S. enteritidis-contaminated eggs from the two flocks with infected hens was less than 0.06%. Other Salmonella spp. isolated were S. heidelberg from 58 hens (10%), and S. hadar, S. mbandaka and S. typhimurium from one hen (0.2%) each. The MAT with antigens of S. pullorum had a sensitivity of 81% and a specificity of 24% for detecting S. enteritidis-infected hens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Excretion in feces and mucosal persistence of Salmonella ser. Typhimurium in pigs subclinically infected with Oesophagostomum spp

OBJECTIVE: To determine interactions between Oesophagostomum spp and Salmonella ser. Typhimurium in pigs. ANIMALS: 30 healthy 5- to 6-week-old pigs. PROCEDURE: Pigs were allotted to 3 groups (n = 10 pigs/group) and treated as follows: group A was given Oesophagostomum dentatum and O quadrispinulatum; group B was given O dentatum, O quadrispinulatum, and S Typhimurium; and group C was given S Typhimurium only. Pigs in groups A and B were trickle infected with Oesophagostomum spp 3 times weekly throughout the study. After 19 days, groups B and C were inoculated once with S Typhimurium. One pig from each group was euthanatized on the day of Salmonella exposure and 2 and 4 days after Salmonella exposure. The remaining pigs were euthanatized on days 16 and 17 after Salmonella exposure. RESULTS: Pigs with dual infections of nematodes and bacteria (group B) excreted significantly higher amounts of S Typhimurium in feces, compared with nematode-free pigs (group C). In addition, group-B pigs excreted S Typhimurium on more days than pigs in group C. Salmonella Typhimurium was detected in the cecum and colon in the majority of pigs in group B, whereas S Typhimurium was only detected in the colon in pigs in group C. Immunohistochemical examination detected S Typhimurium in 7 of 9 pigs in group B but only 2 of 9 pigs in group C. CONCLUSIONS AND CLINICAL RELEVANCE: Interactions between intestinal nematodes and bacteria may play an important role in the dynamics of S Typhimurium infections.     

Evaluation of three commercial enzyme-linked immunosorbent assays for the detection of antibodies against Salmonella spp. in meat juice from finishing pigs in Spain

The control of animal salmonellosis is considered as a major objective in Europe and indirect ELISAs will be important tools for the implementation of control programs for this infection in pigs. We analyse the results yielded by three commercial ELISAs (Herdcheck Swine Salmonella, SALMOTYPE Pig Screen, and PrioCHECK Salmonella) on meat juice samples from a population of slaughter pigs of Aragon, NW Spain, to assess their efficacy using traditional and latent-class approaches. Overall, the Herdcheck Swine Salmonella detected more Salmonella-infected pigs than the other two tests, but its relative sensitivity was low (65.9%). A similar result was observed when only serotypes detectable by this test were considered (69.1%). When a Bayesian approach was used the Herdcheck Swine Salmonella showed also the highest overall accuracy (sensitivity = 88% and specificity = 74%). Our results suggest that a relatively small proportion of the observed prevalence in herds would be explained by using these ELISAs. Also, this study points out that when different ELISA tests are used within the same herd, results may differ substantially. Thus, caution is advised if it is decided to use these assays for herd health classification in Spanish Salmonella control programs.     

鸭源沙门菌江苏分离株的生物学特性研究

为了解鸭源沙门菌江苏分离株的主要生物学特性,本研究对2012年至2013年从发病或死亡鸭中分离的33株沙门菌分离株进行鉴定,即采用玻片凝集法对分离的沙门菌进行血清学分型,多重PCR方法检测17种毒力基因的分布,按照美国临床和实验室标准化研究所制定的方法进行药物敏感性检测,通过结晶紫半定量法检测分离菌株的生物被膜形成能力.33株鸭源沙门菌的血清学分型结果显示,查理沙门菌占48.5％,为优势血清型.毒力基因检测结果显示,pagC、msgA、sipB、prgH、spaN、tolC、iroN、sopB及pefA为保守基因.药物敏感性检测显示,42.4％的菌株耐受8种以上药物.生物被膜检测显示,有14株细菌生物被膜形成能力为中等以上,其中57.1％的菌株耐8种以上的药物.     

Identification of Salmonella spp. isolates from chicken abattoirs by multiplex-PCR

The present study was carried out to report the occurrence Salmonella spp., Salmonella Enteritidis, and Salmonella Typhimurium in chicken abattoirs. Samples of feces; feathers; scald, evisceration, and chiller water; and rinse water of non-eviscerated, eviscerated, and chilled carcass were collected from six chicken abattoirs. Salmonella isolates were identified by a multiplex-PCR using three sets of primers targeting the invA, pefA, and sefA gene sequences from Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. Salmonella spp. was detected in 10% (29/288) of the samples, whereas serovars Enteritidis and Typhimurium were identified in 62% (7/288), respectively. The results indicate the need to improve hygiene and sanitary standards in poultry slaughter lines, besides the education of food handlers and information to consumers.     

Cross-sectional study on Brucella spp., Leptospira spp. and Salmonella spp. in bats from Montes Claros,Minas Gerais,Brazil

The understanding on the role of bats in the ecology of zoonotic diseases, especially its relevance as a carrier of pathogens, is important for the determination of preventive measures considering the One Health context. The present study aimed to investigate the presence of Brucella spp., Leptospira spp. and Salmonella spp. in blood (n = 163), liver (n = 35) and spleen (n = 62) samples from bats captured in Montes Claros, Minas Gerais, Brazil. Only Salmonella spp. was found in a blood sample of an insectivorous female bat of the species Lasiurus blossevilli, evidencing the capacity of this animal species to host this pathogen. In conclusion, our results in bats from Montes Claros indicate that they do not act as hosts for Brucella spp. and Leptospira spp., although being potential carriers of Salmonella spp. in a low prevalence.     

动物源性食品中沙门氏菌快速检测技术的应用研究

采用自动酶标免疫测试仪(m in i-VIDAS)与PCR技术,对上海地区的174份鸡蛋、580份原料牛奶、253份猪肉、248份牛肉和58份虾仁样品进行了沙门氏菌检测。与国标法对比,M in i-VIDAS的敏感性和特异性达100%和98.8%,PCR法的敏感性和特异性均为100%。同时上述动物源性食品中均检出沙门氏菌,说明存在被沙门氏菌污染的可能,应引起足够重视。