Association between antimicrobial usage in livestock and antimicrobial resistance in Escherichia coli isolates from human urinary tract infections in the Netherlands, 2009-2020.

BACKGROUND: In the last decade, veterinary antimicrobial usage (AMU) and antimicrobial resistance (AMR) among indicator bacteria in livestock have decreased substantially in the Netherlands. The extent to which this decrease has affected AMR levels among human infections remains unclear. OBJECTIVES: To assess the association between AMU in livestock and AMR in Escherichia coli isolates from human urinary tract infections (UTIs). METHODS: Data on AMR and AMU between 2009 and 2020 from Dutch national surveillance programmes for humans and livestock were used. Associations between AMU in four major livestock sectors and AMR in humans were assessed for 10 antimicrobial classes and the ESBL resistance profile, using logistic regression analysis. Associations between AMU and AMR in livestock, between AMR in livestock and in humans, and between AMU and AMR in humans were also assessed. RESULTS: Statistical significance was reached for 16/31 of the tested associations between AMU in livestock and AMR in human E. coli UTIs. Of the significant associations, 11 were positive (OR 1.01-1.24), whereas 5 were negative (OR 0.96-0.99). All associations between human AMU and AMR in E. coli isolates from UTIs were positive and statistically significant. Weak but significant positive correlations were also observed between livestock AMR and human AMR. CONCLUSIONS: Although several significant associations between AMU in livestock and AMR in human UTIs caused by E. coli were observed, the associations between AMU and AMR were generally stronger within the human and animal populations. This indicates that potential zoonotic spread of AMR in E. coli causing human UTIs from livestock sources is limited.

Horsing around: Escherichia coli ST1250 of equine origin harbouring epidemic IncHI1/ST9 plasmid with bla CTX-M-1 and an operon for short-chain fructooligosaccharides metabolism.

The relatedness of the equine-associated Escherichia coli ST1250 and its single- and double-locus variants (ST1250-SLV/DLV), obtained from horses in Europe, was studied by comparative genome analysis. A total of 54 isolates of E. coli ST1250 and ST1250-SLV/DLV from healthy and hospitalized horses across Europe [Czech Republic (n=23), the Netherlands (n=18), Germany (n=9), Denmark (n=3) and France (n=1)] from 2008-2017 were subjected to whole-genome sequencing. An additional 25 draft genome assemblies of E. coli ST1250 and ST1250-SLV/DLV were obtained from the public databases. The isolates were compared for genomic features, virulence genes, clade structure and plasmid content. The complete nucleotide sequences of eight IncHI1/ST9 and one IncHI1/ST2 plasmids were obtained using long-read sequencing by PacBio or MinION. In the collection of 79 isolates, only 10 were phylogenetically close (<8 SNP). The majority of isolates belonged to phylogroup B1 (73/79, 92.4%) and carried bla CTX-M-1 (58/79, 73.4%). The plasmid content of the isolates was dominated by IncHI1 of ST9 (56/62, 90.3%) and ST2 (6/62, 9.7%), while 84.5% (49/58) bla CTX-M-1 genes were associated with presence of IncHI1 replicon of ST9 and 6.9% (4/58) with IncHI1 replicon of ST2 within the corresponding isolates. The operon for the utilization of short chain fructooligosaccharides (fos operon) was present in 55 (55/79, 69.6%) isolates, and all of these carried IncHI1/ST9 plasmids. The eight complete IncHI1/ST9 plasmid sequences showed the presence of bla CTX-M-1 and the fos operon within the same molecule. Sequences of IncHI1/ST9 plasmids were highly conserved (>98% similarity) regardless of country of origin and varied only in the structure and integration site of MDR region. E. coli ST1250 and ST1250-SLV/DLV are phylogenetically-diverse strains associated with horses. A strong linkage of E. coli ST1250 with epidemic multi-drug resistance plasmid lineage IncHI1/ST9 carrying bla CTX-M-1 and the fos operon was identified.

Genomic comparison of mecC-carrying methicillin-resistant Staphylococcus aureus from hedgehogs and humans in the Netherlands.

OBJECTIVES: MRSA carrying the mecC gene (mecC-MRSA) have been found in humans and animals worldwide. A high carriage rate of mecC-MRSA has been described among hedgehogs in different countries. We performed genomic comparison of mecC-MRSA from hedgehogs and humans using next-generation sequencing (NGS) to investigate possible zoonotic transmission in the Netherlands. METHODS: Nasal swabs from hedgehogs (n = 105) were cultured using pre-enrichment and selective plates. Isolates were sequenced using Illumina NGS platforms. These data were compared with sequence data of mecC-MRSA (n = 62) from the Dutch national MRSA surveillance in humans. RESULTS: Fifty hedgehogs were found to be MRSA positive, of which 48 carried mecC. A total of 60 mecC-MRSA isolates derived from 50 hedgehogs were compared with the human isolates. Fifty-nine mecC-MRSA from hedgehogs and all but one isolate from humans belonged to clonal complexes CC130 and CC1943. The mecC gene was located within the SCCmec XI element. Most mecC-MRSA did not carry other resistance genes besides mecC and blaZ. Two human isolates carried erm(C). Isolates differed in the presence of various virulence genes, which were linked to distinct STs and clonal complexes. Some isolates had up to 17 virulence genes, which underlines their pathogenic potential. No genetic clusters of hedgehog and human isolates were found. CONCLUSIONS: mecC-MRSA from hedgehogs and humans mainly belonged to the same two clonal complexes, indicating a common source. No firm evidence for recent zoonotic transmission was found. Further studies are needed to investigate the role of hedgehogs in the occurrence of mecC-MRSA in humans.

The use of aminopenicillins in animals within the EU, emergence of resistance in bacteria of animal and human origin and its possible impact on animal and human health.

Aminopenicillins have been widely used for decades for the treatment of various infections in animals and humans in European countries. Following this extensive use, acquired resistance has emerged among human and animal pathogens and commensal bacteria. Aminopenicillins are important first-line treatment options in both humans and animals, but are also among limited therapies for infections with enterococci and Listeria spp. in humans in some settings. Therefore, there is a need to assess the impact of the use of these antimicrobials in animals on public and animal health. The most important mechanisms of resistance to aminopenicillins are the ß-lactamase enzymes. Similar resistance genes have been detected in bacteria of human and animal origin, and molecular studies suggest that transmission of resistant bacteria or resistance genes occurs between animals and humans. Due to the complexity of epidemiology and the near ubiquity of many aminopenicillin resistance determinants, the direction of transfer is difficult to ascertain, except for major zoonotic pathogens. It is therefore challenging to estimate to what extent the use of aminopenicillins in animals could create negative health consequences to humans at the population level. Based on the extent of use of aminopenicillins in humans, it seems probable that the major resistance selection pressure in human pathogens in European countries is due to human consumption. It is evident that veterinary use of these antimicrobials increases the selection pressure towards resistance in animals and loss of efficacy will at minimum jeopardize animal health and welfare.

Rhodococcus equiU19 strain harbors a nonmobilizable virulence plasmid.

Rhodococcus equiis the causative agent of pyogenic pneumonia in foals, and a virulence-associated protein A (VapA) encoded on the pVAPA virulence plasmid is important for its pathogenicity. In this study, we analyzed the virulence of R. equi strain U19, originally isolated in the Netherlands in 1997 and the genetic characteristics of the pVAPA_U19 plasmid. U19 expressed VapA that was regulated by temperature and pH and underwent significant intracellular proliferation in macrophages. The restriction fragment length polymorphism of pVAPA_U19 digested with EcoRI was similar to that of pREAT701 (85 kb Type I) harbored by R. equi ATCC33701, although the band pattern at 10-20 kb differed. Whole-genome sequencing showed that pVAPA_U19 was 51,684 bp in length and that the vapA pathogenicity island region and the replication/participation were almost identical to those in pREAT701. By contrast, the open reading frames (ORF26-ORF45) genes of pREAT701 (approximately 29,000 bp) were absent from pVAPA_U19. In this lacking region, mobility (MOB) genes, such as relaxase, which allow conjugative DNA processing, and the mating pair formation (MPF) genes, which are a form of the Type IV secretion system and provide the mating channel, were present. Coculture between U19 and five different recipient strains (two plasmid-cured strains and three cryptic plasmid-harboring strains) demonstrated that pVAPA_U19 could not support conjugation. Therefore, pVAPA_U19 does not differ significantly from the previously reported pVAPA in terms of virulence and plasmid replication and maintenance but is a nonmobilizable plasmid unable to cause conjugation because of the absence of genes related to MOB and MPF.

Faecal carriage of Clostridioides difficile is low among veterinary healthcare workers in the Netherlands.

Veterinary healthcare workers are in close contact with many different animals and might be at an increased risk of acquiring Clostridioides difficile. In this cross-sectional study, we assessed the prevalence and risk factors of C. difficile carriage in Dutch veterinary healthcare workers. Participants provided a faecal sample and filled out a questionnaire covering potential risk factors for C. difficile carriage. C. difficile culture positive isolates were polymerase chain reaction (PCR) ribotyped and the presence of toxin genes tcdA, tcdB and cdtA/cdtB was determined. Eleven of 482 [2.3%; 95% confidence interval (CI) 1.3-4.0] veterinary healthcare workers were carriers of C. difficile. Three persons carried C. difficile ribotype 078 (0.6%; 95% CI 0.2-1.8). Risk factors for carriage were health/medication and hygiene related, including poor hand hygiene after patient (animal) contact, and did not include occupational contact with certain animal species. In conclusion, the prevalence of C. difficile carriage in veterinary healthcare workers was low and no indications were found that working in veterinary care is a risk for C. difficile carriage.

Dynamics of Intestinal Carriage of Extended-Spectrum Beta-lactamase-Producing Enterobacteriaceae in the Dutch General Population, 2014-2016.

BACKGROUND: In the Netherlands, the prevalence of intestinal extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) carriage in community-dwelling subjects is ~5%. Little is known about the dynamics of ESBL-E carriage. METHODS: In a nationwide, population-based study (2014-2016) with 4177 community-dwelling subjects, fecal samples from 656 subjects were collected after 1 (time point [T] = 1) and 6 (T = 2) months. The growth of ESBL-E was quantified and a whole-genome sequence analysis was performed. Subjects were categorized as either an incidental, short-term, or long-term carrier or as a noncarrier. Risk factors were determined by random forest models and logistic regression. The transmissibility and duration of ESBL-E carriage was quantified using a transmission model, which also incorporated previous study data. RESULTS: Out of 656 participants, 96 were ESBL-E carriers at T = 0. Of these, 66 (10.1%) subjects were incidental carriers, 22 (3.3%) were short-term carriers, and 38 (5.8%) were long-term carriers; the remaining 530 (80.8%) were noncarriers. The risk factors for long-term carriage were travelling to Asia, swimming in a sea/ocean, and not changing the kitchen towel daily. The log-transformed colony forming units ratio at T = 0 was predictive for ESBL-E carriage at T = 1 (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.2-1.6) and T = 2 (OR, 1.2; 95% CI, 1.1-1.4). Model simulations revealed a median decolonization rate of 2.83/year, an average duration of carriage of 0.35 years, and an acquisition rate of 0.34/year. The trend of the acquisition rate during the study period was close to 0. CONCLUSIONS: The risk factors for long-term ESBL-E carriage were travel- and hygiene-related. The dynamics of ESBL-E carriage in the general Dutch population are characterized by balancing decolonization and acquisition rates.

Transmission of ESBL-producing Escherichia coli between broilers and humans on broiler farms.

BACKGROUND: ESBL and AmpC ß-lactamases are an increasing concern for public health. Studies suggest that ESBL/pAmpC-producing Escherichia coli and their plasmids carrying antibiotic resistance genes can spread from broilers to humans working or living on broiler farms. These studies used traditional typing methods, which may not have provided sufficient resolution to reliably assess the relatedness of these isolates. METHODS: Eleven suspected transmission events among broilers and humans living/working on eight broiler farms were investigated using whole-genome short-read (Illumina) and long-read sequencing (PacBio). Core genome MLST (cgMLST) was performed to investigate the occurrence of strain transmission. Horizontal plasmid and gene transfer were analysed using BLAST. RESULTS: Of eight suspected strain transmission events, six were confirmed. The isolate pairs had identical ESBL/AmpC genes and fewer than eight allelic differences according to the cgMLST, and five had an almost identical plasmid composition. On one of the farms, cgMLST revealed that the isolate pairs belonging to ST10 from a broiler and a household member of the farmer had 475 different alleles, but that the plasmids were identical, indicating horizontal transfer of mobile elements rather than strain transfer. Of three suspected horizontal plasmid transmission events, one was confirmed. In addition, gene transfer between plasmids was found. CONCLUSIONS: The present study confirms transmission of strains as well as horizontal plasmid and gene transfer between broilers and farmers and household members on the same farm. WGS is an important tool to confirm suspected zoonotic strain and resistance gene transmission.

Do vegetarians less frequently carry ESBL/pAmpC-producing Escherichia coli/Klebsiella pneumoniae compared with non-vegetarians?

BACKGROUND: ESBL and plasmid-mediated AmpC (pAmpC)-producing Enterobacteriaceae are frequently found on meat products in Dutch retail, especially on poultry. OBJECTIVES: We investigated whether vegetarians are at lower risk of carrying ESBL/pAmpC-producing Escherichia coli/Klebsiella pneumoniae (ESBL-E/K) compared with persons who consume meat. METHODS: Vegetarians, pescatarians (vegetarians who eat fish) and non-vegetarians (persons who eat meat at least three times per week) were asked to send in a faecal sample and a questionnaire. ESBL-E/K were cultured and MLSTs were determined. ESBL/pAmpC genes were analysed using PCR and sequencing. The risk of ESBL-E/K carriage in the three study groups was analysed using multivariable logistic regression. RESULTS: Prevalence of ESBL-E/K carriage was 8.0% in vegetarians (63/785; 95% CI 6.3-10.1), 6.9% in pescatarians (27/392; 95% CI 4.8-9.8) and 3.8% in non-vegetarians (14/365; 95% CI 2.3-6.3). Multivariable analysis showed an OR for ESBL-E/K carriage of 2.2 for vegetarians (95% CI 1.2-4.0) and 1.6 for pescatarians (95% CI 0.8-3.2) compared with non-vegetarians. The predominant MLST was E. coli ST131 and the most common ESBL genes were blaCTX-M-15, blaCTX-M-27, blaCTX-M-14 and blaCTX-M-1 in all diet groups. Independent risk factors for ESBL-E/K carriage were travel to Africa/Latin America/Asia (OR 4.6; 95% CI 2.8-7.7) in the past 6 months and rarely/never washing hands before food preparation (OR 2.5; 95% CI 1.2-5.0). CONCLUSIONS: Vegetarians and pescatarians did not have a lower risk of ESBL-E/K carriage compared with non-vegetarians, indicating that eating meat is not an important risk factor for ESBL-E/K carriage.

Prolonged carriage of (livestock-associated) MRSA in individuals without professional livestock contact.

OBJECTIVES: To investigate prolonged carriage of MRSA in adults from the general population living in a livestock-dense area, using WGS. METHODS: A cross-sectional study during 2014-15 among 2492 adults without professional livestock contact identified 14 (0.6%) nasal MRSA carriers, 10 of which carried livestock-associated (LA)-MRSA of multiple-locus variable-number tandem repeat analysis (MLVA) complex (MC) 398. Two years later, 12 MRSA-positive and 88 MRSA-negative participants provided a second nasal swab and filled in a short questionnaire. Isolates from persons who were MRSA positive at both timepoints were compared using MLVA and isolates with the same MLVA type were sequenced. The WGS data were used for core-genome MLST (cgMLST) and resistome analysis, including sequenced isolates from the national MRSA surveillance. RESULTS: All MRSA-negative persons tested negative again, while 6 of the 12 initially MRSA-positive persons tested positive again. MLVA revealed that isolate pairs from five individuals had the same MLVA type, of which three were LA-MRSA. cgMLST showed that the distance between these isolate pairs ranged between 3 and 13 genes, while the minimum distance to unrelated isolates from the national MRSA surveillance was 38 genes. Moreover, the resistome present in the five isolate pairs was identical within each pair. None of the prolonged carriers was hospitalized during the 3 months before the sampling moment and none of them with LA-MRSA had contact with livestock in this period. CONCLUSIONS: Prolonged carriage of MRSA, including LA-MRSA, can be demonstrated after more than 30 months in persons without professional livestock contact.

The use of aminoglycosides in animals within the EU: development of resistance in animals and possible impact on human and animal health: a review.

Aminoglycosides (AGs) are important antibacterial agents for the treatment of various infections in humans and animals. Following extensive use of AGs in humans, food-producing animals and companion animals, acquired resistance among human and animal pathogens and commensal bacteria has emerged. Acquired resistance occurs through several mechanisms, but enzymatic inactivation of AGs is the most common one. Resistance genes are often located on mobile genetic elements, facilitating their spread between different bacterial species and between animals and humans. AG resistance has been found in many different bacterial species, including those with zoonotic potential such as Salmonella spp., Campylobacter spp. and livestock-associated MRSA. The highest risk is anticipated from transfer of resistant enterococci or coliforms (Escherichia coli) since infections with these pathogens in humans would potentially be treated with AGs. There is evidence that the use of AGs in human and veterinary medicine is associated with the increased prevalence of resistance. The same resistance genes have been found in isolates from humans and animals. Evaluation of risk factors indicates that the probability of transmission of AG resistance from animals to humans through transfer of zoonotic or commensal foodborne bacteria and/or their mobile genetic elements can be regarded as high, although there are no quantitative data on the actual contribution of animals to AG resistance in human pathogens. Responsible use of AGs is of great importance in order to safeguard their clinical efficacy for human and veterinary medicine.

Long-term Carriage of Extended-Spectrum ß-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae in the General Population in The Netherlands.

Background: This longitudinal study aimed to investigate (risk factors for) persistence of carriage and molecular characteristics of extended-spectrum and plasmid-encoded AmpC ß-lactamase-producing (ESBL/pAmpC) Escherichia coli and Klebsiella pneumoniae (ESBL-E/K) in adults in the Dutch community. Methods: Following a cross-sectional study (ESBL-E/K prevalence, 4.5%), a subset of ESBL-E/K-positive (n = 76) and -negative (n = 249) individuals volunteered to provide 5 monthly fecal samples and questionnaires. ESBL-E/K was cultured using selective enrichment/culture, and multilocus sequence types (MLSTs) were determined. ESBL/pAmpC-genes were analyzed using polymerase chain reaction (PCR) and sequencing. Plasmids were characterized and subtyped by plasmid MLST. Risk factors for persistent carriage were analyzed using logistic regression. Results: Of the initially ESBL-E/K-positive participants, 25 of 76 (32.9%) remained positive in all subsequent samples; 51 of 76 persons (67.1%) tested ESBL-E/K negative at some time point during follow-up, of which 31 (40.8%) stayed negative throughout the longitudinal study. Carriers often carried the same ESBL gene and plasmid, but sometimes in different ESBL-E/K strains, indicative for horizontal transfer of plasmids. Of the 249 initially ESBL-E/K-negative participants, the majority (n = 218 [87.6%]) tested negative during 8 months of follow-up, whereas 31 of 249 (12.4%) participants acquired an ESBL-E/K. Escherichia coli phylogenetic group B2 and D and travel to ESBL high-prevalence countries were associated with prolonged carriage. Conclusions: ESBL-E/K carriage persisted for >8 months in 32.9% of the initially ESBL-positive individuals, while 12.4% of initially negative individuals acquired ESBL-E/K during the study. A single positive test result provides no accurate prediction for prolonged carriage. Acquisition/loss of ESBL-E/K does not seem to be a random process, but differs between bacterial genotypes.

Longitudinal study of ESBL Escherichia coli carriage on an organic broiler farm.

Objectives: To determine the molecular characteristics of ESBL-producing Escherichia coli (ESBL-E) collected during a longitudinal study on an organic broiler farm in order to investigate clonal expansion and horizontal gene transfer. Methods: Isolates were obtained from a longitudinal study performed previously on an organic broiler fattening farm. Samples from individually followed-up broilers, the broiler house, the transport van and persons that took the samples, taken at several timepoints (days 1, 3, 4, 7, 10, 42 and 70) within a production round and during the consecutive one (days 1, 2, 3 and 70), had been investigated for the occurrence of ESBL-E. In the current study, ESBL genes and MLST STs of these ESBL-E were determined. Plasmids were characterized and subtyped. Results: On arrival in round_1, ESBL-E of ST88 predominated, while on days 3, 4, 7 and 10 ST10 was most often found and at slaughter age ST155 and ST1551 prevailed. A shift in STs was also observed in round_2. None of the 35 individually selected broilers followed up in round_1 was positive for the same ESBL-E ST at all sampling times. All isolates carried CTX-M-1 group genes, confirmed as blaCTX-M-1 in 158 isolates. Further analysis of 36 isolates of different STs showed blaCTX-M-1 on IncI1/ST3 plasmids. Conclusions: The rapid dissemination of ESBL-E on this broiler farm was not due to the spread of one specific E. coli clone, but most likely the result of horizontal transfer of an IncI1/ST3 plasmid carrying blaCTX-M-1 resulting in a shift in the predominant ESBL-E population in broilers.

Molecular relatedness of ESBL/AmpC-producing Escherichia coli from humans, animals, food and the environment: a pooled analysis.

Background: In recent years, ESBL/AmpC-producing Escherichia coli (ESBL/AmpC-EC) have been isolated with increasing frequency from animals, food, environmental sources and humans. With incomplete and scattered evidence, the contribution to the human carriage burden from these reservoirs remains unclear. Objectives: To quantify molecular similarities between different reservoirs as a first step towards risk attribution. Methods: Pooled data on ESBL/AmpC-EC isolates were recovered from 35 studies in the Netherlands comprising >27 000 samples, mostly obtained between 2005 and 2015. Frequency distributions of ESBL/AmpC genes from 5808 isolates and replicons of ESBL/AmpC-carrying plasmids from 812 isolates were compared across 22 reservoirs through proportional similarity indices (PSIs) and principal component analyses (PCAs). Results: Predominant ESBL/AmpC genes were identified in each reservoir. PCAs and PSIs revealed close human-animal ESBL/AmpC gene similarity between human farming communities and their animals (broilers and pigs) (PSIs from 0.8 to 0.9). Isolates from people in the general population had higher similarities to those from human clinical settings, surface and sewage water and wild birds (0.7-0.8), while similarities to livestock or food reservoirs were lower (0.3-0.6). Based on rarefaction curves, people in the general population had more diversity in ESBL/AmpC genes and plasmid replicon types than those in other reservoirs. Conclusions: Our 'One Health' approach provides an integrated evaluation of the molecular relatedness of ESBL/AmpC-EC from numerous sources. The analysis showed distinguishable ESBL/AmpC-EC transmission cycles in different hosts and failed to demonstrate a close epidemiological linkage of ESBL/AmpC genes and plasmid replicon types between livestock farms and people in the general population.

Occurrence and molecular characteristics of ESBL/AmpC-producing Escherichia coli in faecal samples from horses in an equine clinic.

Objectives: To investigate the occurrence and characteristics of ESBL/AmpC-producing Escherichia coli in faecal samples from horses at one equine clinic in the Netherlands. Methods: A total of 91 horses, including residents and patients, were sampled. ESBL/AmpC-producing E. coli were identified by a combination disc diffusion test. Phylogenetic groups and MLST were determined. ESBL/AmpC genes were analysed using PCR and sequencing. Plasmids were characterized by transformation and PCR-based replicon typing. Subtyping of plasmids was done by plasmid MLST. Results: At least one E. coli isolate with a confirmed ESBL/AmpC gene was found in samples from 76 horses (84%). Although phylogenetic group B1 E. coli bla CTX-M-1 predominated, a diverse E. coli population was found, indicating that clonal nosocomial spread was not the only reason for the high occurrence found. MLST analysis revealed the presence of 47 E. coli STs, organized in four clusters of genetically related strains. ST10, ST641, ST1079 and ST1250 were most commonly found. With regard to the genes, bla CTX-M-1 was most prevalent ( n = 91), followed by bla CTX-M-2 ( n = 26). The most frequently found plasmid type was IncHI1, but plasmids belonging to the IncF, IncI1 and IncN groups were also identified. Conclusions: A high occurrence of ESBL-producing E. coli in faecal samples was found among horses in an equine clinic and the variety of STs, ESBL genes and plasmid types suggests nosocomial transmission. ESBL E. coli can cause difficult-to-treat infections in horses and prudent use of antimicrobials is warranted. A further assessment of the risks of transmission to persons in close contact with horses, such as caretakers or veterinarians, is crucial.

MRSA in persons not living or working on a farm in a livestock-dense area: prevalence and risk factors.

Objectives: MRSA emerged in livestock and persons in contact with livestock is referred to as livestock-associated MRSA (LA-MRSA). We assessed the prevalence and risk factors for MRSA carriage in persons not living or working on a farm. Methods: A cross-sectional study was performed among 2492 adults living in close proximity of livestock farms. Persons working and/or living on farms were excluded. Nasal swabs were cultured using selective media. Participants completed questionnaires and the distance from the residential address to the nearest farm was calculated. The Mann-Whitney U -test was used to compare median distances. Risk factors were explored with logistic regression. Results: Fourteen persons carried MRSA (0.56%; 95% CI 0.32%-0.92%), 10 of which carried LA-MRSA of multiple-locus variable-number tandem repeat analysis complex (MC) 398 (0.40%; 95% CI 0.20%-0.71%). MRSA MC 398 carriers lived significantly closer to the nearest farm than non-carriers (median: 184 versus 402 m; P < 0.01). In bivariate analyses correcting for contact with livestock, this difference remained significant. Conclusions: Although the prevalence was low, living near farms increased the risk of MRSA MC 398 carriage for persons not living or working on a farm. Further research is necessary to identify the transmission routes.

Public health risk of antimicrobial resistance transfer from companion animals.

Antimicrobials are important tools for the therapy of infectious bacterial diseases in companion animals. Loss of efficacy of antimicrobial substances can seriously compromise animal health and welfare. A need for the development of new antimicrobials for the therapy of multiresistant infections, particularly those caused by Gram-negative bacteria, has been acknowledged in human medicine and a future corresponding need in veterinary medicine is expected. A unique aspect related to antimicrobial resistance and risk of resistance transfer in companion animals is their close contact with humans. This creates opportunities for interspecies transmission of resistant bacteria. Yet, the current knowledge of this field is limited and no risk assessment is performed when approving new veterinary antimicrobials. The objective of this review is to summarize the current knowledge on the use and indications for antimicrobials in companion animals, drug-resistant bacteria of concern among companion animals, risk factors for colonization of companion animals with resistant bacteria and transmission of antimicrobial resistance (bacteria and/or resistance determinants) between animals and humans. The major antimicrobial resistance microbiological hazards originating from companion animals that directly or indirectly may cause adverse health effects in humans are MRSA, methicillin-resistant Staphylococcus pseudintermedius, VRE, ESBL- or carbapenemase-producing Enterobacteriaceae and Gram-negative bacteria. In the face of the previously recognized microbiological hazards, a risk assessment tool could be applied in applications for marketing authorization for medicinal products for companion animals. This would allow the approval of new veterinary medicinal antimicrobials for which risk levels are estimated as acceptable for public health.

Evidence for Human Adaptation and Foodborne Transmission of Livestock-Associated Methicillin-Resistant Staphylococcus aureus.

We investigated the evolution and epidemiology of a novel livestock-associated methicillin-resistant Staphylococcus aureus strain, which colonizes and infects urban-dwelling Danes even without a Danish animal reservoir. Genetic evidence suggests both poultry and human adaptation, with poultry meat implicated as a probable source.

Changes in the Population of Methicillin-Resistant Staphylococcus pseudintermedius and Dissemination of Antimicrobial-Resistant Phenotypes in the Netherlands.

Methicillin-resistant Staphylococcus pseudintermedius (MRSP), which is often multidrug resistant (MDR), has recently emerged as a threat to canine health worldwide. Knowledge of the temporal distribution of specific MRSP lineages, their antimicrobial resistance phenotypes, and their association with clinical conditions may help us to understand the emergence and spread of MRSP in dogs. The aim of this study was to determine the yearly proportions of MRSP lineages and their antimicrobial-resistant phenotypes in the Netherlands and to examine possible associations with clinical conditions. MRSP was first isolated from a canine specimen submitted for diagnostics to the Faculty of Veterinary Medicine of Utrecht University in 2004. The annual cumulative incidence of MRSP among S. pseudintermedius increased from 0.9% in 2004 to 7% in 2013. MRSP was significantly associated with pyoderma and, to a lesser extent, with wound infections and otitis externa. Multilocus sequence typing (MLST) of 478 MRSP isolates yielded 39 sequence types (ST) belonging to 4 clonal complexes (CC) and 15 singletons. CC71 was the dominant lineage that emerged since 2004, and CC258, CC45, and several unlinked isolates became more frequent during the following years. All but two strains conferred an MDR phenotype, but strains belonging to CC258 or singletons were less resistant. In conclusion, our study showed that MDR CC71 emerged as the dominant lineage from 2004 and onward and that less-resistant lineages were partly replacing CC71.

40 years of veterinary papers in JAC - what have we learnt?

This review, for the occasion of the 40th anniversary of the Journal of Antimicrobial Chemotherapy (JAC), gives an overview of the manuscripts related to veterinary bacteriology published in the journal in the past 40 years with a focus on 'One Health' aspects. From 1975 to 2000 the number of manuscripts related to veterinary medicine was limited, but thereafter, the number steadily increased. Most manuscripts published were related to food-producing animals, but companion animals and minor species were also covered. Subjects included antimicrobial usage in animals and the consequences for human medicine, new resistance genes and mechanisms, the prevalence and epidemiology of antimicrobial resistance, and the emergence of resistant bacteria in animals with zoonotic potential such as livestock-associated MRSA (LA-MRSA), methicillin-resistant Staphylococcus pseudintermedius (MRSP) and ESBL-producing Enterobacteriaceae. These manuscripts have added to our knowledge on the risks of transmission of resistant bacteria from animals to humans and the importance of the prudent use of antimicrobial agents in veterinary medicine.