Serological characterization of Salmonella spp. infection in finishing pigs from NE Spain

The seroprevalence of salmonella spp. In finishing pigs in Aragón (NE of Spain) and the potential factors associated with it were assessed. Serum samples were collected directly from the Regional Diagnostic Laboratory (RDL). Only farms submitting a minimum of 30 serum samples to the RDL were included, i.e. exporting and farrow-to-finish farms, and those in the last stages of the Aujezsky\u27s disease eradication program

Salmonellosis in wild birds and its relationship with the infection in finishing pigs

The potential relationship between Salmonella infection in wild birds and pigs was investigated. Feces from pigs, wild birds, and bird droppings or other environmental samples from 25 finishing farms were cultured for Salmonella isolation. In 17 (68%) farms Salmonella was isolated. Out of 57 Salmonella isolates found, 32 (56.1%) were Typhimurium. In 6 (24%) farms the same Salmonella serotype was isolated from samples from different origins and similar AR and PFGE patterns were found, which would support the existence of a transmission cycle of Salmonella infection between birds and pigs in this area. Preventing bird access to farm premises is highly recommended

Estudio serológico de la infección por Salmonella spp. en cerdos de engorde del Noreste de España y factores de riesgo asociados

The results of a serological survey carried out in northeastern Spain to estimate the seroprevalence to Salmonella spp. and to determine potential risk factors are presented. Sera were obtained from farms submitting serum samples to the Regional Diagnostic Laboratory (RDL) for the diagnosis of other infectious diseases included within official eradication/surveillance programs, and farm data collected through a questionnaire. Out of 6,182 pig sera (217 farms) analyzed 1,219 (19.7%) were positive (optical density, OD ≥ 40%). More than 70% of the herds presented ≥ 1 seropositive animal indicating that salmonellosis was widespread. In a multivariable logistic mixed regression model seroprevalence was associated with farms where birds were visible inside the fattening units (OR = 2.1; 95% CI: 1.3-3.2) or that shared workers with other pig farms (OR = 2.5; 95% CI: 1.4-4.7). Seropositivity also increased when farmers used footwear exclusive for the farm (OR = 3.1; 95% CI: 1.3-7.3) or pigs were fed mostly with pellets (OR = 1.7; 95% CI: 1.1-2.6). It was also higher during the fall and winter months. The presence of a changing room and shower in the farm was negatively associated with it (OR = 0.5; 95% CI: 0.3-0.8). Most risk factors could be mitigated through strict hygiene and biosecurity measures, but the high (> 40%) within-herd seroprevalence observed in many herds may challenge the capacity of intervention of animal health authorities.Se presentan los resultados de un estudio serológico realizado en explotaciones porcinas del Noreste de España para estimar la seroprevalencia frente a Salmonella spp. y determinar posibles factores de riesgo asociados. Los sueros se obtuvieron a partir de aquellos enviados por las explotaciones al Laboratorio Regional de Diagnóstico para el diagnóstico de otras enfermedades infecciosas sometidas a erradicación/vigilancia oficial, y los datos sobre las explotaciones se recogieron mediante un cuestionario. De un total de 6.182 sueros de cerdo (217 granjas) analizados 1.219 (19,7%) resultaron positivos (densidad óptica, DO ≥ 40%). Más del 70% de los rebaños presentaron al menos un animal positivo, indicando que la salmonelosis está ampliamente distribuida en la región. Según un modelo multivariable mixto de regresión logística, la seroprevalencia se asoció con granjas en las cuales se veían aves en el interior de las naves (OR = 2,1; IC 95%: 1,3-3,2) y también con granjas que compartían trabajadores (OR = 2,5; IC 95%: 1,4-4,7). Se observó que la seropositividad se incrementaba cuando los trabajadores usaban botas exclusivas en la explotación (OR = 3,1; IC 95%: 1,3-7,3) o al alimentar a los cerdos principalmente con alimento granulado (OR = 1,7; IC 95%: 1,1-2,6). La seroprevalencia también fue superior durante los meses de otoño e invierno. La existencia en las granjas de vestuarios y duchas para el personal se asoció negativamente con la seroprevalencia (OR = 0,5; IC 95%: 0,3-0,8). La mayoría de los factores de riesgo podrían controlarse a través de estrictas medidas de higiene y bioseguridad, pero el gran número de rebaños que presentaron alta seroprevalencia (> 40%) puede poner a prueba la capacidad de intervención de las autoridades sanitarias oficiales

Assessment of the diagnostic accuracy of bacteriological culture and the invA-gen-based PCR for the detection of Salmonella organisms from caecal content from slaughtered pigs through Bayesian approaches

The goal of this study was to determine the accuracy of a culture technique and the invA-gen-based PCR, for the detection of Salmonella spp. From caecal samples from slaughtered pigs. For this purpose a Bayesian approach was used. Two hundred and three pigs were used. Animals were grouped into 2 populations: 96 from small farms and 107 from large farms. Sensitivity was 56% (95% Credible Interval: 40-76) for culture and 91% (95% CI: 81-97) for PCR

The addition of galacto-oligosaccharides on the feed for the control of salmonellosis in fattening pigs

Prebiotics that block intestinal harmful bacteria and stimulate both the activity of beneficial bacteria and the animal immune system may help in controlling pig salmonellosis. We added a galacto-oligosaccharide (Salmosan®) on the diet of pigs during the whole period of fattening to assess its potential effect on the prevalence of Salmonella spp. In a first trial 56 pigs from a small fattening unit (fewer than 200 animals) were fed with a diet where Salmosan® (0.5 kg/Ton of feed) was added, while the rest of the animals were fed with the same feed without the galacto-oligosaccharide

Relationship between Salmonella shedding at the slaughter and pig Salmonella status during the fattening period

In this study, the pig’s risk of shedding at slaughter with regard to its previous Salmonella status was estimated. A total of 133 pigs were serologically monitored monthly to determine their Salmonella status during the fattening period. Mesenteric lymph nodes (MLN) and faecal (FEC) samples were collected further at slaughter for bacteriology. Pigs were grouped as non-infected pigs (group A); animals likely infected at the end of the fattening period (B); and animals infected at least two weeks before the end of the fattening period (C). The probability of shedding in group A was high (36.5%) and likely related to Salmonella exposure during transport or lairage, but also to possible false-negative bacteriological results. The odds of shedding for groups B and C was 3.1 (95%CI=1.1-9.2) and 8.2 (1.4-48.6) times higher, respectively, when compared to group A. Overall most of the infected pigs from groups B and C showed same serotype in MLN and FEC samples (61% and 77%, respectively) and PFGE analysis confirmed majority were genetically related. In conclusion, the control of Salmonella infection along the fattening period appears to be of utmost importance to prevent slaughter contamination

Salmonella Shedding in Slaughter Pigs and the Use of Esterified Formic Acid in the Drinking Water as a Potential Abattoir-Based Mitigation Measure

Pigs shedding Salmonella at slaughter are considered a source of carcass contamination and human infection. To assess this potential risk, the proportion of Salmonella shedders that arrive for slaughter was evaluated in a population of 1068 pigs from 24 farms. Shedding was present in 27.3% of the pigs, and the monophasic variant of Salmonella Typhimurium, an emerging zoonotic serotype, was the most prevalent (46.9%). Antimicrobial resistance (AMR) in Salmonella isolates was common, but few isolates showed AMR to antimicrobials of critical importance for humans such as third-generation cephalosporins (5%), colistin (0%), or carbapenems (0%). However, AMR to tigecycline was moderately high (15%). The efficacy of an esterified formic acid in the lairage drinking water (3 kg formic acid/1000 L) was also assessed as a potential abattoir-based strategy to reduce Salmonella shedding. It was able to reduce the proportion of shedders (60.7% in the control group (CG) vs. 44.3% in the treatment group (TG); p < 0.01). After considering clustering and confounding factors, the odds of shedding Salmonella in the CG were 2.75 (95% CI = 1.80–4.21) times higher than those of the TG, suggesting a potential efficacy of reduction in shedding as high as 63.6%. This strategy may contribute to mitigating the burden of abattoir environmental contamination

Sensitivity of the ISO 6579:2002/Amd 1:2007 standard method for detection of Salmonella spp. on mesenteric lymph nodes from slaughter pigs

The ISO 6579:2002/Amd 1:2007 (ISO) standard has been the bacteriological standard method used in the European Union for the detection of Salmonella spp. in pig mesenteric lymph nodes (MLN), but there are no published estimates of the diagnostic sensitivity (Se) of the method in this matrix. Here, the Se of the ISO (SeISO) was estimated on 675 samples selected from two populations with different Salmonella prevalences (14 farms with a =20% prevalence and 13 farms with a <20% prevalence) and through the use of latent-class models in concert with Bayesian inference, assuming 100% ISO specificity, and an invA-based PCR as the second diagnostic method. The SeISO was estimated to be close to 87%, while the sensitivity of the PCR reached up to 83.6% and its specificity was 97.4%. Interestingly, the bacteriological reanalysis of 33 potential false-negative (PCR-positive) samples allowed isolation of 19 (57.5%) new Salmonella strains, improving the overall diagnostic accuracy of the bacteriology. Considering the usual limitations of bacteriology regarding Se, these results support the adequacy of the ISO for the detection of Salmonella spp. from MLN and also that of the PCR-based method as an alternative or complementary (screening) test for the diagnosis of pig salmonellosis, particularly considering the cost and time benefits of the molecular procedure

Characterization of Salmonella enterica serovars Tyhimurium and 4,5,[12]:i:- isolated from pigs and pig environmental-related sources in the NE of Spain

A total of 117 Salmonella Typhimurium and 59 monophasic Salmonella Typhimurium (S. 4,[5],12:i:-) strains isolated from pig, wild bird, rodent, and farm environmental samples were characterized by phage typing, antibiotic susceptibility testing and Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA) in order to evaluate their phenotypic and genetic relatedness. In S. 4,[5],12:i:- the most prevalent phage types were U311 (40.7%) and DT195 (22%) which did not correspond with the so-called Spanish clone, and generally showed a different resistant pattern (ASSuT). Antibiotic resistance was found in 85.8% of the isolates, with 94.1% of them displaying multidrug resistance (MDR). MLVA identified 92 different profiles, six of them shared by both serovars. The Minimum Spanning Tree showed one major cluster that included 95% of the S. 4,[5],12:i:- isolates, which came from different animal sources, geographic locations and time periods, suggesting high clonality among those Salmonella strains and the ability to spread among pig farms. Phenotypically, isolates of S. 4,[5],12:i:- were closer to European strains than to the well-characterized Spanish clone. The spread of these new strains of S. 4,[5],12:i:- would have been likely favoured by the important pig trade between this Spanish region and other European countries

Presence of Clostridium difficile in pig faecal samples and wild animal species associated with pig farms

Aims: to determine the presence of Clostridium difficile on fattening pig farms in north-eastern Spain. Methods and results: Twenty-seven farms were sampled. Pools of pig faecal samples (n = 210), samples of intestinal content from common farm pest species (n = 95) and environment-related samples (n = 93) were collected. Isolates were tested for toxin genes of C. difficile, and typed by PCR-ribotyping and toxinotyping. The minimal inhibitory concentrations of six antimicrobial agents were determined using Etest. Thirty-four isolates were obtained from 12 farms, and 30 (88·2%) had toxin genes. Seven ribotypes were identified. Ribotype 078 and its variant 126 were predominant (52·9%). The same ribotypes were isolated from different animal species on the same farm. None of the isolates were resistant to metronidazole or vancomycin. Conclusions: Clostridium difficile was common within the pig farm environment. Most of the positive samples came from pest species or were pest-related environmental samples. Significance and Impact of the Study: Pest species were colonized with toxigenic and antimicrobial-resistant C. difficile strains of the same ribotypes that are found in humans and pigs. Rodents and pigeons may transmit toxigenic and antimicrobial-resistant C. difficile strains that are of the same ribotypes as those occuring in humans