Antimicrobial use in lactating sows, piglets, nursery, and grower-finisher pigs on swine farms in Ontario, Canada during 2017 and 2018

Prevalence and Characterization of Salmonella Species on U.S. Swine Sites as Part of the NAHMS 2021 Swine Enteric Study

Salmonella species are an important cause of systemic and gastrointestinal disease in animals and humans worldwide; they are also increasingly resistant to multiple classes of antimicrobials which may aid in their treatment and control. Salmonella can also be shed asymptomatically. The aim of this study was to survey the U.S. swine industry to determine and update estimates of Salmonella prevalence, antimicrobial resistance (AMR), replicon distribution, and biofilm potential as part of the United States Department of Agriculture (USDA) National Animal Health Monitoring System (NAHMS) 2021 Swine Study. A total of 1,043 fecal samples were collected from finishing swine 20 weeks and older on 39 sites, from November 2021 through April 2022. Salmonella detection was culture-based and antimicrobial susceptibility was determined by broth microdilution; replicon typing was completed by PCR. Biofilm potential was assessed using a crystal violet assay and normalized to a positive control strain. Overall, the prevalence of Salmonella in swine feces was low (3.9%; 41 of 1,043) and comprised of a broad range of serotypes including S. Derby (34.1%) and S. I 4,[5],12:i:- (22.0%), also found previously. Resistance to at least one antimicrobial agent was detected in 61.0% of isolates with the most prevalent resistance to tetracycline (53.7%). Multidrug resistance (≥3 antimicrobial classes) was found in 26.8% of isolates. The most prevalent replicon types detected were IncHI2 (24.4%) and IncA/C (24.4%), both of which have previously been associated with Salmonella isolated from swine. The majority (85.4%) of isolates formed some biofilm in vitro, characterized as weak (36.6%), moderate (39.0%), or strong (9.8%), with no major associations among common serotype or AMR pattern. Surveillance programs updating the prevalence and characteristics of Salmonella in the U.S. swine population will inform ongoing farm-level and public health efforts to mitigate animal and human health risks.

Florfenicol administration in piglets co-selects for multiple antimicrobial resistance genes

Antimicrobial use in food-producing animals such as pigs is a significant issue due to its association with antimicrobial resistance. Florfenicol is a broad-spectrum phenicol antibiotic used in swine for various indications; however, its effect on the swine microbiome and resistome is largely unknown. This study investigated these effects in piglets treated intramuscularly with florfenicol at 1 and 7 days of age. Fecal samples were collected from treated (n = 30) and untreated (n = 30) pigs at nine different time points up until 140 days of age, and the fecal metagenomes were sequenced. The fecal microbiomes of the two groups of piglets were most dissimilar in the immediate period following florfenicol administration. These differences were driven in part by an increase in the relative abundance of Clostridium scindens, Enterococcus faecalis, and Escherichia spp. in the florfenicol-treated piglets and Fusobacterium spp., Pauljensenia hyovaginalis, and Ruminococcus gnavus in the control piglets. In addition to selecting for florfenicol resistance genes (floR, fexA, and fexB), florfenicol also selected for genes conferring resistance to the aminoglycosides, beta-lactams, or sulfonamides up until weaning at 21 days of age. Florfenicol-resistant Escherichia coli isolated from these piglets were found to carry a plasmid with floR, along with tet(A), aph(6)-Id, aph(3″)-Ib, sul2, and blaTEM-1/blaCMY-2. A plasmid carrying fexB and poxtA (phenicols and oxazolidinones) was identified in florfenicol-resistant Enterococcus avium, Enterococcus faecium, and E. faecalis isolates from the treated piglets. This study highlights the potential for co-selection and perturbation of the fecal microbial community in pre-weaned piglets administered florfenicol.IMPORTANCEAntimicrobial use remains a serious challenge in food-animal production due to its linkage with antimicrobial resistance. Antimicrobial resistance can reduce the efficacy of veterinary treatment and can potentially be transferred to humans through the food chain or direct contact with animals and their environment. In this study, early-life florfenicol treatment in piglets altered the composition of the fecal microbiome and selected for many unrelated antimicrobial resistance genes up until weaning at 21 days of age. Part of this co-selection process appeared to involve an Escherichia coli plasmid carrying a florfenicol resistance gene along with genes conferring resistance to at least four other antimicrobial classes. In addition, florfenicol selected for certain genes that provide resistance to multiple antimicrobial classes, including the oxazolidinones. These results highlight that florfenicol can co-select for multiple antimicrobial resistance genes, and their presence on mobile genetic elements suggests the potential for transfer to other bacteria.

Pediococcus pentosaceus RC007 and Saccharomyces boulardii RC009 as antibiotic alternatives for gut health in post-weaning pigs

AIMS

The aim of the present study was to evaluate a novel probiotic Pediococcus pentosaceus RC007 used alone and convined with Saccharomyces cerevisiae var. boulardii RC009, as in-feed additives to substitute the nontherapeutic use of antibiotics, and evaluate the different structural characteristics of intestinal bacterial populations between groups, correlated with pig production performance.

METHODS AND RESULTS

The in vivo study was conducted on post-weaning pigs, from 21 to 56 days old. Three dietary treatments were included: T1-basal diet (BD-control group); T2-BD with P. pentosaceus RC007; and T3-BD with a mix of P. pentosaceus RC007 and S. boulardii RC009. The weight gain increase of pigs consuming non-therapeutic antibiotics was similar to those that did not consume antibiotics during the study (P = 0.0234), but had better health indicators. The use of a probiotic combination increased carcass weight and significantly reduced the lumbar fat thickness. In terms of taxonomic composition, there was a tendency to modify the abundance of Proteobacteria, Cyanobacteria, Enterobacteriaceae, and Lactobacillaceae in pigs that consumed the additives. The genus Butyricicoccus, Collinsella, and Ruminococcus tended to be more abundant in the microbiota of pigs at T3.

CONCLUSIONS

For the first time, the results of the present study indicate that P. pentosaceus RC007 and S. boulardii RC009, a probiotic combination, could be a good substitute for antibiotics in improving pig production performance, while also contributing to a healthier gut microbiota, especially with the reduced abundance of Proteobacteria and Cyanobacteria.

First detection of multidrug-resistant and toxigenic Pasteurella aerogenes in sow vaginal discharge: a novel threat to swine health in Thailand

Pasteurella aerogenes has been implicated in reproductive disorders in sows, yet its prevalence and characteristics in vaginal discharge are not well understood. This study aimed to detect P. aerogenes in sow vaginal discharge samples and investigate its antibiotic resistance profile, toxin genes, and toxicity. P. aerogenes was isolated from 40% (8/20) of samples. Antimicrobial susceptibility testing revealed universal resistance to amoxicillin-clavulanate (4:1), with 87.5% of isolates also resistant to oxytetracycline, amoxicillin, ceftriaxone, and enrofloxacin. The colistin resistance gene mcr-2 was detected in 75% of isolates, while class 1 integron (int1) was found in 12.5%. The pax toxin gene cluster was present in 75% of isolates. Toxicity assays using Panagrellus redivivus demonstrated dose-dependent effects of P. aerogenes supernatant containing pax toxins. This study represents the first report of P. aerogenes isolation from sow vaginal discharge in Thailand. The high prevalence of antibiotic resistance, presence of the mcr-2 gene, and toxicity of pax toxin-positive isolates suggest that P. aerogenes may be an underestimated factor in swine reproductive health. These findings highlight the need for further investigation into the role of P. aerogenes in sow reproductive disorders and its potential impact on swine production.

In-situ growth of MOF-derived Co3S4@MoS2 heterostructured electrocatalyst for the detection of furazolidone

The over-exploitation of antibiotics in food and farming industries ruined the environmental and human health. Consequently, electrochemical sensors offer significant advantages in monitoring these compounds with high accuracy. Herein, MOF-derived hollow Co3S4@MoS2 (CS@MS) heterostructure has been prepared hydrothermally and applied to fabricate an electrochemical sensor to monitor nitrofuran class antibiotic drug. Various spectroscopic methodologies have been employed to elucidate the structural and morphological information. Our prepared electrocatalyst has better electrocatalytic performance than bare and other modified glassy carbon electrodes (GCE). Our CS@MS/GCE sensor exhibited a highly sensitive detection by offering a low limit of detection, good sensitivity, repeatability, reproducibility, and stability results. In addition, our sensor has shown a good selectivity towards the target analyte among other potential interferons. The practical reliability of the sensor was measured by analyzing various real-time environmental and biological samples and obtaining good recovery values. From the results, our fabricated CS@MS could be an active electrocatalyst material for an efficient electrochemical sensing application.

Ceftiofur treatment of sows results in long-term alterations in the nasal microbiota of the offspring that can be ameliorated by inoculation of nasal colonizers

BACKGROUND

The nasal microbiota of the piglet is a reservoir for opportunistic pathogens that can cause polyserositis, such as Glaesserella parasuis, Mycoplasma hyorhinis or Streptococcus suis. Antibiotic treatment is a strategy to control these diseases, but it has a detrimental effect on the microbiota. We followed the piglets of 60 sows from birth to 8 weeks of age, to study the effect of ceftiofur on the nasal microbiota and the colonization by pathogens when the treatment was administered to sows or their litters. We also aimed to revert the effect of the antibiotic on the nasal microbiota by the inoculation at birth of nasal colonizers selected from healthy piglets. Nasal swabs were collected at birth, and at 7, 15, 21 and 49 days of age, and were used for pathogen detection by PCR and bacterial culture, 16S rRNA amplicon sequencing and whole shotgun metagenomics. Weights, clinical signs and production parameters were also recorded during the study.

RESULTS

The composition of the nasal microbiota of piglets changed over time, with a clear increment of Clostridiales at the end of nursery. The administration of ceftiofur induced an unexpected temporary increase in alpha diversity at day 7 mainly due to colonization by environmental taxa. Ceftiofur had a longer impact on the nasal microbiota of piglets when administered to their sows before farrowing than directly to them. This effect was partially reverted by the inoculation of nasal colonizers to newborn piglets and was accompanied by a reduction in the number of animals showing clinical signs (mainly lameness). Both interventions altered the colonization pattern of different strains of the above pathogens. In addition, the prevalence of resistance genes increased over time in all the groups but was significantly higher at weaning when the antibiotic was administered to the sows. Also, ceftiofur treatment induced the selection of more beta-lactams resistance genes when it was administered directly to the piglets.

CONCLUSIONS

This study shed light on the effect of the ceftiofur treatment on the piglet nasal microbiota over time and demonstrated for the first time the possibility of modifying the piglets' nasal microbiota by inoculating natural colonizers of the upper respiratory tract.

In-feed nutritional additive probiotic Saccharomyces boulardii RC009 can substitute for prophylactic antibiotics and improve the production and health of weaning pigs

Background and Aims

Non-therapeutic antibiotic use is associated with the current decrease in antibiotic therapeutic efficiency and the emergence of a wide range of resistant strains, which constitutes a public health risk. This study aimed to evaluate the use of Saccharomyces cerevisiae var. boulardii RC009 as a nutritional feed additive to substitute the prophylactic use of antibiotics and improve the productive performance and health of post-weaning piglets.

Materials and Methods

Four regular nutritional phases were prepared. Post-weaning pigs (21-70 days old) received one of two dietary treatments: T1-basal diet (BD-control group) with in-feed antibiotics as a prophylactic medication (one pulse of Tiamulin in P3 and one pulse of Amoxicillin in P4); and T2-BD without in-feed antibiotics but with Saccharomyces boulardii RC009 (1 × 1012 colony forming unit/T feed). The feed conversion ratio (FCR), total weight gain (TWG-kg), and daily weight gain (DWG-kg) were determined. A post-weaning growth index (GI) was calculated and animals (160 days old) from each treatment were analyzed at the abattoir after sacrifice for carcass weight and respiratory tract lesions.

Results

Pigs consuming probiotics had higher TWG and DWG than the control group. The group of animals with low body weight obtained the same results. Saccharomyces boulardii administration decreased diarrhea, and FCR reduction was related to a GI improvement. A significant increase in carcass weight and muscle thickness reduction was observed in animals received the probiotic post-weaning.

Conclusion

Saccharomyces boulardii RC009, a probiotic additive, was found to improve the production parameters of pigs post-weaning and enhance their health status, indicating that it may be a promising alternative to prophylactic antibiotics.

Mobile colistin resistance (MCR), extended-spectrum beta-lactamase (ESBL) and multidrug resistance monitoring in Escherichia coli (commensal and pathogenic) in pig farming: need of harmonized guidelines and clinical breakpoints

Current data on antimicrobial resistance in pig production is essential for the follow-up strategic programs to eventually preserve the effectiveness of last-resort antibiotics for humans. Here, we characterized 106 Escherichia coli recovered in routine diagnosis (2020-2022) from fecal sample pigs, belonging to 74 Spanish industrial farms, affected by diarrhea. The analysis of virulence-gene targets associated with pathotypes of E. coli, determined 64 as pathogenic and 42 as commensal. Antimicrobial susceptibility testing (AST) performed by minimal inhibitory concentration (MIC) assay, was interpreted by applying breakpoints/cut-off values from the different standards EUCAST/TECOFF 2022, CLSI VET ED5:2020, and CASFM VET2020. Comparisons taking EUCAST as reference exhibited moderate to high correlation except for enrofloxacin, neomycin, and florfenicol. Of note, is the lack of clinical breakpoints for antibiotics of common use in veterinary medicine such as cefquinome, marbofloxacin, or florfenicol. AST results determined multidrug resistance (MDR) to ≥3 antimicrobial categories for 78.3% of the collection, without significant differences in commensal vs pathogenic isolates. Plasmid-mediated mobile colistin resistance gene (mcr) was present in 11.3% of 106 isolates, all of them pathogenic. This means a significant decrease compared to our previous data. Furthermore, 21.7% of the 106 E. coli were ESBL-producers, without differences between commensal and pathogenic isolates, and mcr/ESBL genes co-occurred in 3 isolates. Phylogenetic characterization showed a similar population structure (A, B1, C, D, and E), in both commensal and pathogenic E. coli, but with significant differences for B1, C, and E (38.1 vs 20.3%; 19 vs 1.6%; and 7.1 vs 25%, respectively). Additionally, we identified one B2 isolate of clone O4:H5-B2-ST12 (CH13-223), positive for the uropathogenic (UPEC) status, and in silico predicted as human pathogen. We suggest that a diagnosis workflow based on AST, detection of mcr and ESBL genes, and phylogenetic characterization, would be a useful monitoring tool under a "One-Health" perspective.

Insights in the Development and Uses of Alternatives to Antibiotic Growth Promoters in Poultry and Swine Production

The overuse and misuse of antibiotics has contributed to the rise and spread of multidrug-resistant bacteria. To address this global public health threat, many countries have restricted the use of antibiotics as growth promoters and promoted the development of alternatives to antibiotics in human and veterinary medicine and animal farming. In food-animal production, acidifiers, bacteriophages, enzymes, phytochemicals, probiotics, prebiotics, and antimicrobial peptides have shown hallmarks as alternatives to antibiotics. This review reports the current state of these alternatives as growth-promoting factors for poultry and swine production and describes their mode of action. Recent findings on their usefulness and the factors that presently hinder their broader use in animal food production are identified by SWOT (strength, weakness, opportunity, and threat) analysis. The potential for resistance development as well as co- and cross-resistance with currently used antibiotics is also discussed. Using predetermined keywords, we searched specialized databases including Scopus, Web of Science, and Google Scholar. Antibiotic resistance cannot be stopped, but its spreading can certainly be hindered or delayed with the development of more alternatives with innovative modes of action and a wise and careful use of antimicrobials in a One Health approach.