Eurasian griffon vultures carry widespread antimicrobial resistant Salmonella and Campylobacter of public health concern

The global emergence of antimicrobial-resistant (AMR) strains of Salmonella and Campylobacter is a serious public health concern. Both bacteria are leading causes of human gastrointestinal foodborne infections and the two most reported zoonoses in the European Union. By feeding on livestock carcasses, especially from intensive farming, as well as on landfill sites, obligate avian scavengers can become infected with zoonotic pathogens and AMR strains, and can be considered large-scale sentinels of the environmental burden. In this study, we assessed the occurrence and AMR of Salmonella spp. and Campylobacter spp. in 218 Eurasian griffon vultures (Gyps fulvus) captured in north-eastern Spain. We isolated Salmonella from 8.1 % of individuals and Campylobacter lari from 4.7 %. Among the 10 different Salmonella serovars found, monophasic S. Typhimurium was the most frequent. Genotyping analysis revealed same strains of monophasic S. Typhimurium shared by gulls, livestock and humans. Isolates from both bacterial species presented AMR to important antimicrobials (tetracyclines, fluoroquinolones and β-lactams). In conclusion, this study shows that Eurasian griffon vultures in north-eastern Spain are carriers of widespread AMR zoonotic Salmonella and Campylobacter. More comprehensive analyses are still needed to understand the potential risk of spill-over from those wild birds to humans.

Observations on the distribution and persistence of monophasic Salmonella Typhimurium on infected pig and cattle farms

Following a rapid rise in cases of monophasic Salmonella Typhimurium DT193 (mST) in humans and pigs since 2007 a detailed study of the prevalence and persistence of mST on pig and cattle farms in Great Britain (GB) was undertaken. Thirteen commercial pig farms and twelve cattle farms, identified as mST-positive from surveillance data, were intensively sampled over a three year period. Five indoor and eight outdoor pig farms and four beef and eight dairy farms were included. Individual and pooled faecal samples were collected from each epidemiological group and environmental samples throughout each farm and the antimicrobial resistance profile determined for a selection of mST-positive isolates. Indoor pig farms had a higher mST prevalence than outdoor pig farms, and across both cattle and pig farms the juvenile animals had a higher mST prevalence than the adult animals. Overall, mST prevalence decreased with time across all pig farms, from 25% to less than 15% of environmental samples and 22% to 15% of pooled faecal samples; only one organic outdoor breeding farm was Salmonella-negative at the end of the study. Across the cattle farms no mST was detected by the end of the study, apart from one persistent farm. Clearance time of mST was between seven and twenty-five months. Farms were selected based on having the antimicrobial resistance profile ampicillin, streptomycin, sulphonamides and tetracycline (A, S, SU, T), although resistance to trimethoprim-potentiated sulphamethoxazole was also identified on five pig farms sampled. This study provided a detailed insight into the distribution and persistence of mST on individual pig and cattle farms in GB. It has identified variation in mST shedding of individual animals, and the data can be applied to the wider livestock industry when considering the distribution of mST once identified on an individual farm.

Observations on the introduction and dissemination of Salmonella in three previously low prevalence status pig farms in the United Kingdom

In the United Kingdom a serological Salmonella surveillance scheme was run in pigs up to 2012. Farms that maintained a low seroprevalence (<10%) were recognised as "Platinum" pig farms. The aim of this study was to investigate the occurrence and distribution of Salmonella in three farms (17P, 18P and 46P) that had lost their "Platinum" status. Four visits to each farm were made over a period of 15 months. The sampling was carried out by collecting pooled pen floor faecal swab and environmental samples. All samples were tested for Salmonella by a modification of ISO6579 Annex D, and serovars were determined for all isolates. The Salmonella prevalence peaked in the Summer/Autumn months and all farms were still positive at the end of the study. The overall sample prevalence was higher in farm 17P (46%) and 18P (35%) than 46P (19%). Monophasic S. Typhimurium (mST) represented 77.8% of the Salmonella isolates, mainly from farms 17P and 46P. The mST isolated at the initial visit may have been introduced via other livestock present on farm or introduction into the herd of infected animals. The results of this study suggest that incursion of mST was likely to be the main cause of the loss of "Platinum" status and confirm that mST can persist in pigs and their environment.

Investigation of in-feed organic acids as a low cost strategy to combat Salmonella in grower pigs

Salmonella carriage in pigs is a significant food safety issue. Dietary supplementation with organic acids has previously been shown to reduce shedding and transmission of Salmonella. Therefore, this study aimed to examine the effect of three commercially available organic acid-based products on Salmonella levels in grower pigs, using a model of experimental infection that closely mimics natural exposure to the organism. Seven week old trial pigs (n=40) with a mean weight of 14.7kg were placed in one of four pens with 10 pigs/pen. Pens had previously been contaminated with Salmonella Typhimurium 4,[5],12;i;- via seeder pigs. Trial pigs received one of four diets for 28days: 1, control diet; 2, sodium butyrate supplemented diet; 3, benzoic acid supplemented diet and 4, formic-citric acid supplemented diet. A further 10 pigs were placed in a Salmonella-free pen receiving the control diet. Pigs were weighed and blood sampled on days 0 and 28. Faeces was collected on day 0, 2, 3, 5, 7, 14, 21 and 28 and examined for Salmonella. On day 28, 5 pigs/group were euthanised and ileocaecal lymph nodes (ILN) and caecal contents sampled for culture. The remaining 5 pigs/pen were then fed the control diet and faeces were collected on days 35 and 42. On day 42 pigs were euthanised and ILN and caecal contents tested for Salmonella levels. The trial was repeated once. Within the first two days of exposure to the contaminated environment, 96% (77/80) of pigs became infected. Most pigs shed Salmonella at levels of between 10⁰-10³ CFU/g faeces for at least 7days post-exposure. A significant reduction in Salmonella faecal concentration was observed after supplementation with sodium butyrate (p=0.001) and a formic citric acid blend (p<0.0001). Average daily weight gain (ADWG) was significantly increased in all groups fed the supplemented feed when compared to the positive control group. The use of sodium butyrate or a blend of formic and citric acid in feed could be considered a cost-effective control measure to reduce Salmonella faecal shedding and improve ADWG in Salmonella infected herds.

Longitudinal characterization of monophasic Salmonella Typhimurium throughout the pig's life cycle

Swine have been described as an important reservoir of multidrug resistant monophasic Salmonella Typhimurium, though information on its ecology is scarce. A longitudinal study was performed in order to elucidate the Salmonella 4,[5],12:i:- dynamics throughout the pig's production cycle. A total of 209 faecal samples were collected from 10 sows and in six sampling times during the life of 70 pigs from a Portuguese industrial farm, and 43 isolates of S. 4,[5],12:i:- were identified and characterized regarding clonality and antimicrobial resistance phenotype and genotype. Most isolates (n=42) exhibited resistance to at least ampicillin, kanamycin, neomycin, streptomycin, tetracycline and sulfonamides (encoded by blaTEM, aphAI-IAB, strA, strB, tetB and sul2, respectively). Isolates obtained during the finishing phase showed additional resistance to chloramphenicol and florfenicol (floR), gentamicin and netilmicin (aac(3')-IV). To our knowledge, this study is the first description of aphAI-IAB in S. 4,[5],12:i:-. PFGE analysis showed uneven distribution of isolates into three clusters, A (n=34), B (n=8) and C (n=1). PFGE cluster A was predominant in sows (n=5) and piglets in the farrowing phase (n=17) and in pigs in the early finishing phase (n=11) suggesting a carryover from birth to adult age. The introduction of PFGE cluster B isolates in adulthood could have had an external source, reinforcing the relevance of environmental transmission in the farm ecosystem. This study reveals a dynamic interaction between monophasic S. Typhimurium and the pressures exerted under an intensive swine production setting.