Occurrence, distribution and health risk assessment of quinolone residues in cultured fish in southeast China

Quinolone antibiotics are widely utilized in aquaculture, but little is known about the health effects of their residues. This study used UPLC-MS/MS to analyze the distribution of 11 quinolone antibiotics in cultured fish sold in a coastal city in southeast China - Fujian Province and to assess their health risks. The study found 35.77% of 260 cultured fish samples detected quinolones, with three exceeding the MRL and one containing the banned drug ofloxacin. Of the 11 quinolones tested, three were found in cultured fish, with enrofloxacin at up to 246.0 μg kg-1, followed by ciprofloxacin and ofloxacin. The distribution of antibiotic detection rates showed no significant differences across regions or time periods; however, notable variations were observed among different fish species. The dietary exposure assessment revealed that consuming cultured fish does not pose a health risk to residents. Nevertheless, there are still instances that exceed regulatory limits. Therefore, routine monitoring and risk assessment are essential for enhancing regulatory measures and protecting public health.

Diversity of evolution in MDR monophasic S. Typhimurium among food animals and food products in Southern China from 2011 to 2018

The monophasic variant of Salmonella enterica serovar Typhimurium with the antigenic formula 1,4,[5],12:i:- is one of the most common pathogenic bacteria causing global food-borne outbreaks. However, the research on molecular characteristics and evolution of monophasic S. typhimurium in China is still lacking. In the current study, 59 monophasic S. typhimurium strains were isolated from food animals and food products in South China between 2011 and 2018. A total of 87.5 % of monophasic S. typhimurium isolates were grouped into one independent clade with other monophasic S. typhimurium strains in China distinct from other countries by phylogenomic analysis. These isolates possess variable genotypes, including multiple ARGs on plasmid IncHI2, diverse evolutions at the fljAB locus, and virulence factors. Our results suggest that the monophasic S. typhimurium isolates currently circulating in China might be an independent epidemic subtype.

Extended Spectrum β-Lactamase-Producing Enterobacterales of Shrimp and Salmon Available for Purchase by Consumers in Canada-A Risk Profile Using the Codex Framework

The extended-spectrum β-lactamase (ESBL)-producing Enterobacterales (ESBL-EB) encompass several important human pathogens and are found on the World Health Organization (WHO) priority pathogens list of antibiotic-resistant bacteria. They are a group of organisms which demonstrate resistance to third-generation cephalosporins (3GC) and their presence has been documented worldwide, including in aquaculture and the aquatic environment. This risk profile was developed following the Codex Guidelines for Risk Analysis of Foodborne Antimicrobial Resistance with the objectives of describing the current state of knowledge of ESBL-EB in relation to retail shrimp and salmon available to consumers in Canada, the primary aquacultured species consumed in Canada. The risk profile found that Enterobacterales and ESBL-EB have been found in multiple aquatic environments, as well as multiple host species and production levels. Although the information available did not permit the conclusion as to whether there is a human health risk related to ESBLs in Enterobacterales in salmon and shrimp available for consumption by Canadians, ESBL-EB in imported seafood available at the retail level in Canada have been found. Surveillance activities to detect ESBL-EB in seafood are needed; salmon and shrimp could be used in initial surveillance activities, representing domestic and imported products.

Beta-lactam, aminoglycoside, and quinolone resistance in Escherichia coli strains isolated from shrimps and mussels in the Marmara Sea

The purpose of the study was to examine the prevalence of Escherichia coli in shrimps and mussels, and to determine the distribution of β-lactam, aminoglycoside, quinolone, and multi-drug resistance phenotypically and genotypically in E. coli isolates obtained from mussels and shrimps in Istanbul. Faecal samples were collected from mussels (n = 96) and shrimps (n = 96) from the Marmara Sea coastline and fish markets in Istanbul. For the detection of antibiotic susceptibilities, seven antibiotic groups were used. β-lactamase, aminoglycoside, and quinolone genes were also determined. A total of 34 (17.7%, 15 shrimps, and 19 mussels) E. coli were isolated, and 17 (50%) were found to be resistant to one or more antimicrobials. The highest resistance was seen against aminoglycosides with 11 isolates (32.35%), followed by quinolones with 10 isolates (29.41%) and extended-spectrum β-lactamase (ESBL) with 4 isolates (11.76%). Multi-drug resistance was detected in 5 isolates (14.7%) from 3 shrimp and 2 mussel samples. The prevalence of ESBL genes was demonstrated at 3.84% in mussels and shrimp samples. There were no AmpC and carbapenemase-producing genes. These samples harbored blaCTX-M-1 (n = 3) and blaTEM (n = 4). Ten isolates were resistant to aminoglycosides genotypically. Resistance genes detected were strB in 2 isolates, aadA in 5, strB and aadA together in 3, ANT('')-Ia, aphA1 and aphA2 simultaneously in 3, aphA1 in 1, aac(3)-IIa in 1 isolate. aac(6')-Ib-cr gene was detected in only one of 10 phenotypically resistant isolates to quinolones.

Quantitative Proteomics Reveal the Inherent Antibiotic Resistance Mechanism against Norfloxacin Resistance in Aeromonas hydrophila

Recently, the prevalence of Aeromonas hydrophila antibiotic-resistant strains has been reported in aquaculture, but its intrinsic antibiotic resistance mechanisms are largely unknown. In the present study, a label-free proteomics technology was used to compare the differential protein abundances in response to norfloxacin (NOR) stress in A. hydrophila. The results showed that there were 186 proteins decreasing and 220 proteins increasing abundances in response to NOR stress. Bioinformatics analysis showed that the differentially expressed proteins were enriched in several biological processes, such as sulfur metabolism and homologous recombination. Furthermore, the antibiotic sensitivity assays showed that the deletion of AHA_0904, cirA, and cysI significantly decreased the resistance against NOR, whereas ΔAHA_1239, ΔcysA, ΔcysD, and ΔcysN significantly increased the resistance against NOR. Our results provide insights into NOR resistance mechanisms and indicate that AHA_0904, cirA, AHA_1239, and sulfur metabolism may play important roles in NOR resistance in A. hydrophila.

Evolution and implementation of One Health to control the dissemination of antibiotic-resistant bacteria and resistance genes: A review

Antibiotic resistance is a serious threat to humanity and its environment. Aberrant usage of antibiotics in the human, animal, and environmental sectors, as well as the dissemination of resistant bacteria and resistance genes among these sectors and globally, are all contributing factors. In humans, antibiotics are generally used to treat infections and prevent illnesses. Antibiotic usage in food-producing animals has lately emerged as a major public health concern. These medicines are currently being utilized to prevent and treat infectious diseases and also for its growth-promoting qualities. These methods have resulted in the induction and spread of antibiotic resistant infections from animals to humans. Antibiotics can be introduced into the environment from a variety of sources, including human wastes, veterinary wastes, and livestock husbandry waste. The soil has been recognized as a reservoir of ABR genes, not only because of the presence of a wide and varied range of bacteria capable of producing natural antibiotics but also for the usage of natural manure on crop fields, which may contain ABR genes or antibiotics. Fears about the human health hazards of ABR related to environmental antibiotic residues include the possible threat of modifying the human microbiota and promoting the rise and selection of resistant bacteria, and the possible danger of generating a selection pressure on the environmental microflora resulting in environmental antibiotic resistance. Because of the connectivity of these sectors, antibiotic use, antibiotic residue persistence, and the existence of antibiotic-resistant bacteria in human-animal-environment habitats are all linked to the One Health triangle. The pillars of support including rigorous ABR surveillance among different sectors individually and in combination, and at national and international level, overcoming laboratory resource challenges, and core plan and action execution should be strictly implemented to combat and contain ABR under one health approach. Implementing One Health could help to avoid the emergence and dissemination of antibiotic resistance while also promoting a healthier One World. This review aims to emphasize antibiotic resistance and its regulatory approaches from the perspective of One Health by highlighting the interconnectedness and multi-sectoral nature of the human, animal, and environmental health or ill-health facets.

Antibiotic Resistance in the Finfish Aquaculture Industry: A Review

Significant challenges to worldwide sustainable food production continue to arise from environmental change and consistent population growth. In order to meet increasing demand, fish production industries are encouraged to maintain high growth densities and to rely on antibiotic intervention throughout all stages of development. The inappropriate administering of antibiotics over time introduces selective pressure, allowing the survival of resistant bacterial strains through adaptive pathways involving transferable nucleotide sequences (i.e., plasmids). This is one of the essential mechanisms of antibiotic resistance development in food production systems. This review article focuses on the main international regulations and governing the administering of antibiotics in finfish husbandry and summarizes recent data regarding the distribution of bacterial resistance in the finfish aquaculture food production chain. The second part of this review examines promising alternative approaches to finfish production, sustainable farming techniques, and vaccination that circumvents excessive antibiotic use, including new animal welfare measures. Then, we reflect on recent adaptations to increasingly interdisciplinary perspectives in the field and their greater alignment with the One Health initiative.

Aquatic Environments as Hotspots of Transferable Low-Level Quinolone Resistance and Their Potential Contribution to High-Level Quinolone Resistance

The disposal of antibiotics in the aquatic environment favors the selection of bacteria exhibiting antibiotic resistance mechanisms. Quinolones are bactericidal antimicrobials extensively used in both human and animal medicine. Some of the quinolone-resistance mechanisms are encoded by different bacterial genes, whereas others are the result of mutations in the enzymes on which those antibiotics act. The worldwide occurrence of quinolone resistance genes in aquatic environments has been widely reported, particularly in areas impacted by urban discharges. The most commonly reported quinolone resistance gene, qnr, encodes for the Qnr proteins that protect DNA gyrase and topoisomerase IV from quinolone activity. It is important to note that low-level resistance usually constitutes the first step in the development of high-level resistance, because bacteria carrying these genes have an adaptive advantage compared to the highly susceptible bacterial population in environments with low concentrations of this antimicrobial group. In addition, these genes can act additively with chromosomal mutations in the sequences of the target proteins of quinolones leading to high-level quinolone resistance. The occurrence of qnr genes in aquatic environments is most probably caused by the release of bacteria carrying these genes through anthropogenic pollution and maintained by the selective activity of antimicrobial residues discharged into these environments. This increase in the levels of quinolone resistance has consequences both in clinical settings and the wider aquatic environment, where there is an increased exposure risk to the general population, representing a significant threat to the efficacy of quinolone-based human and animal therapies. In this review the potential role of aquatic environments as reservoirs of the qnr genes, their activity in reducing the susceptibility to various quinolones, and the possible ways these genes contribute to the acquisition and spread of high-level resistance to quinolones will be discussed.

Prevalence and Characterization of Extended-Spectrum β-Lactamase- and Carbapenemase-Producing Enterobacterales from Tunisian Seafood

Aquaculture is a rapidly expanding sector in which it is important to monitor the occurrence of multi-drug resistant (MDR) bacteria. The presence of extended-spectrum β-lactamase (ESBL-) or carbapenemase-producing Enterobacterales is a commonly used indicator of the resistance burden in a given sector. In this study, 641 pieces of farmed fish (sea bream and sea bass), as well as 1075 Mediterranean clams, were analyzed. All ESBL- and carbapenemase-producing Enterobacterales collected were whole-genome sequenced. The proportion of ESBL-producing Enterobacterales was 1.4% in fish and 1.6% in clams, carried by Escherichia coli (n = 23) and Klebsiella pneumoniae (n = 4). The ESBL phenotype was exclusively due to the presence of bla_CTX-M genes, the most frequent one being bla_CTX-M-15. The bla_CTX-M-1 gene was also identified in six E. coli, among which four were carried by IncI1/pST3 plasmids, possibly betraying an animal origin. Carbapenemases were absent in fish but identified in two K. pneumoniae isolates from clams (bla_NDM-1 and bla_OXA-48). Several sequence types (STs) identified were associated with human MDR clones such as E. coli ST131 and ST617, or K. pneumoniae ST307 and ST147. Our results might indicate that bacteria from hospital or farm effluents can reach the open sea and contaminate seafood and fish that are living or raised nearby. Therefore, monitoring the quality of water discharged to the sea and the presence of MDR bacteria in seafood is mandatory to ensure the quality of fishery products.

Enrofloxacin Promotes Plasmid-Mediated Conjugation Transfer of Fluoroquinolone-Resistance Gene qnrS

This study aimed to determine the effect of enrofloxacin (ENR) on the transfer of the plasmid-mediated quinolone resistance (PMQR) gene qnrS from opportunistic pathogen Escherichia coli (E2) to Salmonella Enteritidis (SE211) and to analyze the resistance characteristics of SE211-qnrS isolates. The plasmid carrying qnrS gene of E2 was sequenced by Oxford Nanopore technology. The plasmid carrying qnrS gene belonged to incompatibility group IncY. In vitro, the transfer experiment of IncY plasmid was performed by the liquid medium conjugation method. The conjugation transfer frequency of the IncY plasmid was 0.008 ± 0.0006 in the absence of ENR, 0.012 ± 0.003 in 1/32 MIC_ENR, 0.01 ± 0.008 in 1/8 MIC_ENR, and 0.03 ± 0.015 (Mean±SD) in 1/2 MIC_ENR, respectively. After inoculation of E. coli E2 and SE211, chickens were treated with different doses of ENR (3.03, 10, and 50 mg/kg b.w.) for 7 days consecutively. To screen the SE211-qnrS strains from intestinal tract of chickens, the resistance genes and susceptibility of isolates were identified. The amount of E. coli E2 and the copy number of qnrS gene in the chicken intestinal tract were determined by colony counting and qPCR, respectively. In vivo, more SE211-qnrS strains were isolated from the treated group compared with the untreated group. SE211-qnrS strains not only obtained IncY plasmid, but also showed similar resistance phenotype as E2. In conclusion, ENR treatment can promote the spread of a IncY-resistance plasmid carrying the qnrS fluoroquinolone-resistance gene in Escherichia coli and the development of drug-resistant bacteria.

Effects of aquaculture waste feeds and antibiotics on marine benthic ecosystems in the Mediterranean Sea

Intensive aquaculture is an important source of organic waste and antibiotics into the marine environment. Yet, their impacts on benthic marine ecosystems are poorly understood. Here, we investigated the ecological impacts of fish feed waste alone and in combination with three different antibiotics (i.e., oxytetracycline, florfenicol and flumequine) in benthic ecosystems of the Mediterranean Sea by performing a field experiment. We assessed the fate of the antibiotics in the sediment and their accumulation in wild fauna after two weeks of exposure. Moreover, we investigated the impact of the feed waste alone and in combination with the antibiotics on sediment physico-chemical properties, on benthic invertebrates, as well as on the microbiota and resistome of the sampled sediments. One week after the last antibiotic application, average oxytetracycline and flumequine concentrations in the sediment were <1% and 15% of the applied dose, respectively, while florfenicol was not detected. Flumequine concentrations in wild invertebrates reached 3 μg g^-1, while concentrations of oxytetracycline were about an order of magnitude lower, and florfenicol was not detected. Feed waste, with and without antibiotics, increased the concentration of fine particulate matter, affected the pH and redox conditions, and significantly reduced the biodiversity and abundance of benthic invertebrates. Feed waste also had a significant influence on the structure of sediment microbial communities, while specific effects related to the different antibiotics ranged from insignificant to mild. The presence of antibiotics significantly influenced the normalized abundance of the measured antibiotic resistance genes. Florfenicol and oxytetracycline contributed to an increase of genes conferring resistance to macrolides, tetracyclines, aminoglycosides and chloramphenicol, while flumequine had a less clear impact on the sediment resistome. This study demonstrates that feed waste from aquaculture farms can rapidly alter the habitat and biodiversity of Mediterranean benthic ecosystems, while antibiotic residual concentrations can contribute to the enrichment of bacterial genes resistant to antibiotic classes that are of high relevance for human medicine.

Antibiotic Resistance Profiles and Molecular Characteristics of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli and Klebsiella pneumoniae Isolated From Shrimp Aquaculture Farms in Kerala, India

This study was undertaken to evaluate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in selected shrimp aquaculture farms (n = 37) in Kerala, South India and to characterize the isolates using molecular tools. Overall, a low prevalence of ESBL-producers was found in the farms, most likely due to the reduced antibiotic usage in the shrimp farming sector. Out of the 261 samples (77 shrimp and 92 each of water and sediment), 14 (5.4%) tested positive for ESBL-E. coli or ESBL-K. pneumoniae. A total of 32 ESBL-E. coli and 15 ESBL- K. pneumoniae were recovered from these samples. All ESBL isolates were cefotaxime-resistant with minimal inhibitory concentration (MIC) ≥32 μg/ml. Of all isolates, 9 (28.1%) E. coli and 13 (86.7%) K. pneumoniae showed simultaneous resistance to tetracycline, ciprofloxacin, and trimethoprim-sulfamethoxazole. PCR analysis identified CTX-M group 1 (bla CTX-M-15 ) as the predominant ESBL genotype in both E. coli (23, 71.9%) and K. pneumoniae (15, 100%). Other beta-lactamase genes detected were as follows: bla TEM and bla SHV (11 K. pneumoniae), bla CTX-M group 9 (9 E. coli), and bla CMY-2 (2 E. coli). Further screening for AMR genes identified tetA and tetB (13, 40.6%), sul1 (11, 34.4%), sul2 (9, 28.1%), catA and cmlA (11, 34.4%), qepA and aac(6')-Ib-cr (9, 28.1%) and strAB and aadA1 (2, 6.3%) in E. coli, and qnrB (13, 86.7%), qnrS (3, 20%), oqxB (13, 86.7%), tetA (13, 86.7%), and sul2 (13, 86.7%) in K. pneumoniae isolates. Phylogenetic groups identified among E. coli isolates included B1 (4, 12.5%), B2 (6, 18.8%), C (10, 31.3%), D (3, 9.4%), and E (9, 28.1%). PCR-based replicon typing (PBRT) showed the predominance of IncFIA and IncFIB plasmids in E. coli; however, in K. pneumoniae, the major replicon type detected was IncHI1. Invariably, all isolates of K. pneumoniae harbored virulence-associated genes viz., iutA, entB, and mrkD. Epidemiological typing by pulsed-field gel electrophoresis (PFGE) revealed that E. coli isolates recovered from different farms were genetically unrelated, whereas isolates of K. pneumoniae showed considerable genetic relatedness. In conclusion, our findings provide evidence that shrimp aquaculture environments can act as reservoirs of multi-drug resistant E. coli and K. pneumoniae.

Whole-Genome Sequencing and Machine Learning Analysis of Staphylococcus aureus from Multiple Heterogeneous Sources in China Reveals Common Genetic Traits of Antimicrobial Resistance

Staphylococcus aureus is a worldwide leading cause of numerous diseases ranging from food-poisoning to lethal infections. Methicillin-resistant S. aureus (MRSA) has been found capable of acquiring resistance to most antimicrobials. MRSA is ubiquitous and diverse even in terms of antimicrobial resistance (AMR) profiles, posing a challenge for treatment. Here, we present a comprehensive study of S. aureus in China, addressing epidemiology, phylogenetic reconstruction, genomic characterization, and identification of AMR profiles. The study analyzes 673 S. aureus isolates from food as well as from hospitalized and healthy individuals. The isolates have been collected over a 9-year period, between 2010 and 2018, from 27 provinces across China. By whole-genome sequencing, Bayesian divergence analysis, and supervised machine learning, we reconstructed the phylogeny of the isolates and compared them to references from other countries. We identified 72 sequence types (STs), of which, 29 were novel. We found 81 MRSA lineages by multilocus sequence type (MLST), spa, staphylococcal cassette chromosome mec element (SCCmec), and Panton-Valentine leukocidin (PVL) typing. In addition, novel variants of SCCmec type IV hosting extra metal and antimicrobial resistance genes, as well as a new SCCmec type, were found. New Bayesian dating of the split times of major clades showed that ST9, ST59, and ST239 in China and European countries fell in different branches, whereas this pattern was not observed for the ST398 clone. On the contrary, the clonal transmission of ST398 was more intermixed in regard to geographic origin. Finally, we identified genetic determinants of resistance to 10 antimicrobials, discriminating drug-resistant bacteria from susceptible strains in the cohort. Our results reveal the emergence of Chinese MRSA lineages enriched of AMR determinants that share similar genetic traits of antimicrobial resistance across human and food, hinting at a complex scenario of evolving transmission routes. IMPORTANCE Little information is available on the epidemiology and characterization of Staphylococcus aureus in China. The role of food is a cause of major concern: staphylococcal foodborne diseases affect thousands every year, and the presence of resistant Staphylococcus strains on raw retail meat products is well documented. We studied a large heterogeneous data set of S. aureus isolates from many provinces of China, isolated from food as well as from individuals. Our large whole-genome collection represents a unique catalogue that can be easily meta-analyzed and integrated with further studies and adds to the library of S. aureus sequences in the public domain in a currently underrepresented geographical region. The new Bayesian dating of the split times of major drug-resistant enriched clones is relevant in showing that Chinese and European methicillin-resistant S. aureus (MRSA) have evolved differently. Our machine learning approach, across a large number of antibiotics, shows novel determinants underlying resistance and reveals frequent resistant traits in specific clonal complexes, highlighting the importance of particular clonal complexes in China. Our findings substantially expand what is known of the evolution and genetic determinants of resistance in food-associated S. aureus in China and add crucial information for whole-genome sequencing (WGS)-based surveillance of S. aureus.

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.

Emergence of ciprofloxacin heteroresistance in foodborne Salmonella enterica serovar Agona

BACKGROUND

Bacterial heteroresistance has been increasingly identified as an important phenomenon for many antibiotic/bacterium combinations.

OBJECTIVES

To investigate ciprofloxacin heteroresistance in Salmonella and characterize mechanisms contributing to ciprofloxacin heteroresistance.

METHODS

Ciprofloxacin-heteroresistant Salmonella were identified by population analysis profiling (PAP). Target mutations and the presence of PMQR genes were detected using PCR and sequencing. Expression of acrB, acrF and qnrS was conducted by quantitative RT-PCR. Competition ability and virulence were also compared using pyrosequencing, blue/white screening, adhesion and invasion assays and a Galleria model. Two subpopulations were whole-genome sequenced using Oxford Nanopore and Illumina platforms.

RESULTS

PAP identified one Salmonella from food that yielded a subpopulation demonstrating heteroresistance to ciprofloxacin at a low frequency (10-9 to 10-7). WGS and PFGE analyses confirmed that the two subpopulations were isogenic, with six SNPs and two small deletions distinguishing the resistant from the susceptible. Both subpopulations possessed a T57S substitution in ParC and carried qnrS. The resistant subpopulation was distinguished by overexpression of acrB and acrF, a deletion within rsxC and altered expression of soxS. The resistant population had a competitive advantage against the parental population when grown in the presence of bile salts but was attenuated in the adhesion and invasion of human intestinal cells.

CONCLUSIONS

We determined that heteroresistance resulted from a combination of mutations in fluoroquinolone target genes and overexpression of efflux pumps associated with a deletion in rsxC. This study warns that ciprofloxacin heteroresistance exists in Salmonella in the food chain and highlights the necessity for careful interpretation of antibiotic susceptibility.

Phenotypic and Genotypic Properties of Fluoroquinolone-Resistant, qnr-Carrying Escherichia coli Isolated from the German Food Chain in 2017

Fluoroquinolones are the highest priority, critically important antimicrobial agents. Resistance development can occur via different mechanisms, with plasmid-mediated quinolone resistance (PMQR) being prevalent in the livestock and food area. Especially, qnr genes, commonly located on mobile genetic elements, are major drivers for the spread of resistance determinants against fluoroquinolones. We investigated the prevalence and characteristics of qnr-positive Escherichia (E.) coli obtained from different monitoring programs in Germany in 2017. Furthermore, we aimed to evaluate commonalities of qnr-carrying plasmids in E. coli. We found qnr to be broadly spread over different livestock and food matrices, and to be present in various sequence types. The qnr-positive isolates were predominantly detected within selectively isolated ESBL (extended spectrum beta-lactamase)-producing E. coli, leading to a frequent association with other resistance genes, especially cephalosporin determinants. Furthermore, we found that qnr correlates with the presence of genes involved in resistance development against quaternary ammonium compounds (qac). The detection of additional point mutations in many isolates within the chromosomal QRDR region led to even higher MIC values against fluoroquinolones for the investigated E. coli. All of these attributes should be carefully taken into account in the risk assessment of qnr-carrying E. coli from livestock and food.

A Novel Structure Harboring blaCTX-M-27 on IncF Plasmids in Escherichia coli Isolated from Swine in China

The aim of this study was to elucidate the prevalence of bla_CTX-M-27-producing Escherichia coli and transmission mechanisms of bla_CTX-M-27 from swine farms in China. A total of 333 E. coli isolates were collected from two farms from 2013 to 2016. Thirty-two CTX-M-27-positive E. coli were obtained, and all were multidrug-resistant. Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) profiles indicated a wide range of strain types that carried bla_CTX-M-27, and the sequence type ST10 predominated. Conjugation, replicon typing, S1-PFGE and hybridization experiments confirmed that 28 out of 32 CTX-M-27 positive isolates carried bla_CTX-M-27 genes on plasmids F18:A-:B10 (16) and F24:A-:B1 (12).The bla_CTX-M-27 genes for 24 isolates were transmitted by plasmids with sizes ranging from 40 to 155 kb. A comparative analysis with bla_CTX-M-27-plasmids indicated that the tra-trb region of F24:A-:B1 plasmids was destroyed by insertion of a complex region (eight isolates) and a novel structure containing bla_CTX-M-27 in the F18:A-:B10 plasmids (12 isolates). The novel structure increased the stability of the bla_CTX-M-27 gene in E. coli. This study indicated that the predominant vehicle for bla_CTX-M-27 transmission has diversified over time and that control strategies to limit bla_CTX-M-27 transmission in farm animals are necessary.

Characterization of a Novel Variant of the Quinolone-Resistance Gene qnrB (qnrB89) Carried by a Multi-Drug Resistant Citrobacter gillenii Strain Isolated from Farmed Salmon in Chile

The main objective of this study was to characterize using whole-genome sequencing analysis, a new variant of the qnrB gene (qnrB89) carried by a fluoroquinolone-susceptible bacterium isolated from mucus of farmed Salmo salar fingerling in Chile. Citrobacter gillenii FP75 was identified by using biochemical tests and 16S ribosomal gene analysis. Nucleotide and amino acid sequences of the qnrB89 gene exhibited an identity to qnrB of 81.24% and 91.59%, respectively. The genetic environment of qnrB89 was characterized by the upstream location of a sequence encoding for a protein containing a heavy metal-binding domain and a gene encoding for a N-acetylmuramoyl-L-alanine amidase protein, whereas downstream to qnrB89 gene were detected the csp and cspG genes, encoding cold-shock proteins. The qnrB89 gene was located on a large chromosomal contig of the FP75 genome and was not associated with the 10-kb plasmid and class 1 integron harbored by the FP75 strain. This study reports for the first time the carriage of a qnrB gene by the C. gillenii species, and its detection in a bacterial strain isolated from farmed salmon in Chile.

Mobilization of Tn1721-like structure harboring blaCTX-M-27 between P1-like bacteriophage in Salmonella and plasmids in Escherichia coli in China

The aim of this study was to explore the characteristics of bla_CTX-M-27 carriage and mobilization in Salmonella and Escherichia coli isolates from food-producing animals in China. A total of 2280 E. coli and 229 Salmonella isolates collected from food animals from June 2003 to September 2014 were screened for the presence of bla_CTX-M-27 gene. The bla_CTX-M-27-positive isolates were typed and plasmid DNA sequenced to determine the genetic context of bla_CTX-M-27 and plasmid types present. Bacterial fitness was evaluated by growth curve and plasmid stability in vitro. CTX-M-27-positive E. coli (18, 0.79 %) and Salmonella (34, 14.85 %) were detected. PFGE profiles of CTX-M-27-positive strains revealed a wide variety of genotypes and S. Indiana was the most prevalent serotype. Replicon typing, S1-PFGE and hybridization of CTX-M-27-carrying plasmids confirmed that bla_CTX-M-27 gene was located on IncFII (12/18), IncN (4/18), and non-typeable (2/18) plasmids in E. coli and on P1-like bacteriophage (21/34), IncP (4/34), IncFIB (4/34), IncN (2/34), IncHI2 (2/34), and IncA/C (1/34) plasmids in Salmonella. Comparison and analysis of gene context of bla_CTX-M-27 in P1-like bacteriophage and plasmids revealed they shared the same structure and contained an identical genetic context with the Tn1721-like structure ΔISEcp1B-bla_CTX-M-27-IS903D-iroN-Δmap-Tn1721. In addition, plasmid stability tests indicated that the bla_CTX-M-27 P1-like bacteriophage were more stable than plasmids in the absence of cefotaxime selective pressure. These results demonstrate that Tn1721-like transposons harboring CTX-M-27 could be mobilized between different plasmids in E. coli and P1-like bacteriophage disseminated among Salmonella.

Bacterial Diversity and Antibiotic Susceptibility of Sparus aurata from Aquaculture

In a world where the population continues to increase and the volume of fishing catches stagnates or even falls, the aquaculture sector has great growth potential. This study aimed to contribute to the depth of knowledge of the diversity of bacterial species found in Sparus aurata collected from a fish farm and to understand which profiles of diminished susceptibility to antibiotics would be found in these bacteria that might be disseminated in the environment. One hundred thirty-six bacterial strains were recovered from the S. aurata samples. These strains belonged to Bacillaceae, Bacillales Family XII. Incertae Sedis, Comamonadaceae, Enterobacteriaceae, Enterococcaceae, Erwiniaceae, Micrococcaceae, Pseudomonadaceae and Staphylococcaceae families. Enterobacter sp. was more frequently found in gills, intestine and skin groups than in muscle groups (p ≤ 0.01). Antibiotic susceptibility tests found that non-susceptibility to phenicols was significantly higher in gills, intestine and skin samples (45%) than in muscle samples (24%) (p ≤ 0.01) and was the most frequently found non-susceptibility in both groups of samples. The group of Enterobacteriaceae from muscles presented less decreased susceptibility to florfenicol (44%) than in the group of gills, intestine and skin samples (76%). We found decreased susceptibilities to β-lactams and glycopeptides in the Bacillaceae family, to quinolones and mupirocin in the Staphylococcaceae family, and mostly to β-lactams, phenicols and quinolones in the Enterobacteriaceae and Pseudomonadaceae families. Seven Enterobacter spp. and five Pseudomonas spp. strains showed non-susceptibility to ertapenem and meropenem, respectively, which is of concern because they are antibiotics used as a last resort in serious clinical infections. To our knowledge, this is the first description of species Exiguobacterium acetylicum, Klebsiella michiganensis, Lelliottia sp. and Pantoea vagans associated with S. aurata (excluding cases where these bacteria are used as probiotics) and of plasmid-mediated quinolone resistance qnrB19-producing Leclercia adecarboxylata strain. The non-synonymous G385T and C402A mutations at parC gene (within quinolone resistance-determining regions) were also identified in a Klebsiella pneumoniae, revealing decreased susceptibility to ciprofloxacin. In this study, we found not only bacteria from the natural microbiota of fish but also pathogenic bacteria associated with fish and humans. Several antibiotics for which decreased susceptibility was found here are integrated into the World Health Organization list of "critically important antimicrobials" and "highly important antimicrobials" for human medicine.

Spread of resistance genes from duck manure to fish intestine in simulated fish-duck pond and the promotion of cefotaxime and As

Integrated culture is a widespread culture mode in South China, in which resistance genes (RGs) also spread in the circulation system with nutrients. Accordingly, the aim of the present study was to investigate the spread of RGs in a fish-duck pond and the RGs and bacterial community of fish intestines. Five fish tanks, including a control tank and four experimental tanks (duck manure, duck manure + cefotaxime, duck manure + As, and duck manure + cefotaxime + As), were tested for 100 days. The results showed that duck manure increased both the diversity and relative abundance of RGs in fish intestines, and the addition of stress factors (cefotaxime, As) increased the relative abundance of RGs by one to two orders of magnitude. The stress-inducing effect of cefotaxime was greater than that of As. Tetracycline resistance genes were more sensitive to stress factors and were the predominant RGs in fish intestines. RGs in duck manure preferentially spread from the water to biofilm and then to fish intestines, whereas co-stress of cefotaxime and As obviously promoted the spread of RGs to fish intestines. In comparison to the control tank, duck manure and stress factors significantly changed the bacterial community of fish intestines. Correlation analysis also revealed that arsB, MOX, tetA and sul1 were significantly correlated with intI1 (P < 0.01), which hinted a potentially dissemination risk of RGs in fish intestines. These findings provide a theoretical basis for further investigating the dissemination of RGs in integrated culture systems and for evaluating the ecological risk of antibiotic and As use in aquaculture.

Prevalence and associated factors for carriage of Enterobacteriaceae producing ESBLs or carbapenemase and methicillin-resistant Staphylococcus aureus in Hong Kong community

OBJECTIVES

We conducted a cross-sectional study in Hong Kong community to estimate the carriage prevalence, associated factors and genotypes of extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E), methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase-producing Enterobacteriaceae (CPE).

METHODS

Seemingly healthy subjects were asked to provide nasal, handprint and stool samples from March to April 2017. Isolates were characterized by molecular methods. We used multivariable logistic regression models within a generalized estimating equation framework to identify risk factors for ESBL-E carriage. Characteristics of MRSA/CPE carriage were summarized.

RESULTS

The prevalence of ESBL-E, MRSA and CPE were 52.8% (104/197), 2.5% (5/197) and 0.5% (1/197) respectively. Most ESBL-E isolates were E. coli (85.6%; 113/132). Most ESBL genes belonged to bla_CTX-M-G9 (68.9%) and bla_TEM (53.0%) types. Self-reported antibiotic consumption (≥2 courses) in the past six months was associated with ESBL-E carriage (adjusted odds ratio: 4.71-5.47).

CONCLUSIONS

Abundance of ESBL-E in the community are causes of concern, and antibiotic use is associated with its carriage. Presence of MRSA and CPE in community members without clear healthcare exposure hints on a change in their epidemiology. This study establishes a baseline to formulate infection control policies and future studies in combating antimicrobial resistance.

Detection of multidrug resistance and extended-spectrum/plasmid-mediated AmpC beta-lactamase genes in Enterobacteriaceae isolates from diseased cats in Italy

OBJECTIVES

The aim of this study was to determine the antimicrobial susceptibility of Enterobacteriaceae isolated from cats affected by diseases commonly encountered in practice, and to characterise the third-generation cephalosporin (3GC)-resistance molecular mechanisms involved.

METHODS

Clinical samples (n = 100) included 58 rectal swabs from cats with diarrhoea, 31 nasal swabs from cats with clinical signs of upper respiratory tract disease, four ear swabs from cats with otitis, three conjunctival swabs from cats with conjunctivitis, two oral swabs from cats with stomatitis, one swab from a skin abscess and one urine sample from a cat with cystitis. A total of 125 Enterobacteriaceae were isolated from 90 cats. Escherichia coli was the most frequently isolated species (n = 65), followed by Enterobacter species (n = 20), Proteus species (n = 13), Citrobacter species (n = 12) and others (n = 15). Bacterial susceptibility testing was performed with respect to eight antimicrobial classes. Beta (β)-lactamase genes were identified by PCR and nucleotide sequencing.

RESULTS

Overall, the higher frequency of resistance was to amoxicillin-clavulanate (61.3%), trimethoprim/sulfamethoxazole (33.6%) and cefotaxime (32.8%). Thirty-six percent of the isolates (n = 45) were resistant to 3GCs. Of these isolates, 34 were tested by PCR and nucleotide sequencing and 23 were confirmed as encoding β-lactamase genes. Fourteen 3GC-resistant isolates harboured extended-spectrum β-lactamases (ESBLs) belonging to groups CTX-M-1 (n = 12, two of which were CTX-M-79), CTX-M-2 (n = 1) and CTX-M-9 (n = 1), as well as SHV-12 (n = 1) and TEM-92 (n = 1). Nine isolates had CMY-2 plasmid-mediated AmpC β-lactamases (pAmpC). Thirty-one percent (n = 39) of the isolates were multidrug resistant (MDR) and were isolated from 34% (n = 31/90) of the cats.

CONCLUSIONS AND RELEVANCE

A high frequency of MDR and ESBL/pAmpC β-lactamase-producing Enterobacteriaceae were detected among bacteria isolated from a feline population in southern Italy with a variety of common clinical conditions, which poses limitations on therapeutic options for companion animals. We describe the first detection of CTX-M-79 and TEM-92 ESBL genes in isolates from cats.

Antimicrobial Resistance in Swine Fecal Specimens Across Different Farm Management Systems

Antimicrobial use in agricultural animals is known to be associated with increases in antimicrobial resistance. Most prior studies have utilized culture and susceptibility testing of select organisms to document these phenomena. In this study we aimed to detect 66 antimicrobial resistance (AMR) genes for 10 antimicrobial agent classes directly in swine fecal samples using our previously developed antimicrobial resistance TaqMan array card (AMR-TAC) across three different swine farm management systems. This included 38 extensive antimicrobial use (both in treatment and feed), 30 limited antimicrobial use (treatment only), and 30 no antimicrobial use farms. The number of resistance genes detected in extensive antimicrobial use farms was higher than in limited and no antimicrobial use farms (28.2 genes ± 4.2 vs. 24.0 genes ± 4.1 and 22.8 genes ± 3.6, respectively, p < 0.05). A principal component analysis and hierarchical clustering of the AMR gene data showed the extensive use farm samples were disparate from the limited and no antimicrobial use farms. The prevalence of resistance genes in extensive use farms was significantly higher than the other farm categories for 18 resistance genes including bla SHV, bla CTX-M1 group, bla CTX-M9 group, bla VEB, bla CMY2-LAT, aac(6')-lb-cr, qnrB1, gyrA83L-E. coli, armA, rmtB, aac(3)-IIa, mphA, 23S rRNA 2075G-Campylobacter spp., mcr-1, catA1, floR, dfrA5-14, and dfrA17. These genotypic findings were supported by phenotypic susceptibility results on fecal E. coli isolates. To examine the timing of AMR gene abundance in swine farms, we also performed a longitudinal study in pigs. The results showed that AMR prevalence occurred both early, presumably from mothers, as well as after weaning, presumably from the environment. In summary, detection of AMR genes directly in fecal samples can be used to qualitatively and quantitatively monitor AMR in swine farms.

Prevalence and Characteristics of Extended-Spectrum-β-Lactamase-Producing and Carbapenemase-Producing Enterobacteriaceae from Freshwater Fish and Pork in Wet Markets of Hong Kong

Extended-spectrum-β-lactamase-producing Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) are of global health importance, yet there is a paucity of surveillance studies on food animals in Hong Kong. Here, we report a high prevalence of ESBL-E (ranging from 0.5% to 52.4%) and CPE (0% to 9.9%) from various food animal samples procured from wet markets across Hong Kong. All CPE strains were characterized by whole-genome sequencing and possessed NDM-1 and -5 genes and other resistance determinants. Given the increased resistance profile of these strains, this study highlights the emerging threat of ESBL-E and CPE disseminated in farmed animals. Furthermore, our data enriched our understanding of antibiotic resistance reservoirs from a One Health perspective that can widely spread across various niches, beyond health care settings.

This study identified and characterized extended-spectrum-β-lactamase-producing Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) from farmed freshwater fish and pig offal procured from the wet markets across Hong Kong. During March 2018 to January 2019, 730 food animal samples, namely, 213 snakehead fish, 198 black carp, and 339 pig organs, were examined. ESBL-E and CPE were isolated from the homogenized samples plated on selective media and identified by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF-MS). All ESBL-E and CPE strains were tested for antimicrobial susceptibilities. ESBL-E and CPE gene groups were detected by multiplex PCR and bla_{CTX-M-1/-2/-9} group strains were Sanger sequenced for CTX-M types. All CPE isolates were whole-genome sequenced. Isolation of ESBL-E from pig small (52.4%) and large (50%) intestines and tongues (25.1%) was significantly (P < 0.05) more frequent than from snakehead (0.94%) and black carp (0.5%) fish. ESBL-E isolates (n = 171) revealed resistance rates of 16.3%, 29.8%, 35.6%, 53.2%, 55.0%, and 100% to piperacillin-tazobactam, amoxicillin-clavulanate, cefepime, gentamicin, ciprofloxacin, and ampicillin, respectively, whereas CPE (n = 28) were resistant to almost all the antibiotics tested except gentamicin, ciprofloxacin, and fosfomycin. The predominant ESBL gene groups in fishes and pig offals were bla_CTX, where bla_CTX-M-55 was the major subtype in the bla_CTX-M-1 group (64.4% of isolates in the group). bla_CTX-M-14/-17 was the major genotype in the bla_CTX-M-9 group (32.2%). All CPE strains possessed bla_NDM genes. High rates of ESBL-E and CPE were identified in food animals from wet markets of Hong Kong, which may serve as a potential reservoir of antimicrobial-resistant genes and increase the challenges in tackling antimicrobial resistance beyond health care settings.

IMPORTANCE Extended-spectrum-β-lactamase-producing Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) are of global health importance, yet there is a paucity of surveillance studies on food animals in Hong Kong. Here, we report a high prevalence of ESBL-E (ranging from 0.5% to 52.4%) and CPE (0% to 9.9%) from various food animal samples procured from wet markets across Hong Kong. All CPE strains were characterized by whole-genome sequencing and possessed NDM-1 and -5 genes and other resistance determinants. Given the increased resistance profile of these strains, this study highlights the emerging threat of ESBL-E and CPE disseminated in farmed animals. Furthermore, our data enriched our understanding of antibiotic resistance reservoirs from a One Health perspective that can widely spread across various niches, beyond health care settings.

Genome-Based Analysis of Extended-Spectrum β-Lactamase-Producing Escherichia coli in the Aquatic Environment and Nile Perch (Lates niloticus) of Lake Victoria, Tanzania

Extended-spectrum β-lactamase (ESBL)-producing bacteria constitute an emerging global health issue with food products being vehicles of transmission and the aquatic environments serving as potential reservoirs. This study aimed to characterize ESBL-producing Escherichia coli in Nile perch and water from Lake Victoria in Tanzania. A total of 180 samples of Nile perch and 60 water samples were screened for ESBL-producing E. coli on MacConkey agar supplemented with 2 μg/ml of cefotaxime and confirmed by bla_CTX–M and bla_TEM PCR. Antimicrobial resistance was determined by the disk diffusion method, and the ESBL-producing isolates were whole genome sequencing (WGS). ESBL-producing E. coli were detected in eight of the 180 analyzed Nile perch samples, and only one water sample was positive (1.7%, n = 60). Isolates were resistant to sulfamethoxazole–trimethoprim (100%), ampicillin/cloxacillin (100%), erythromycin 72.7% (8/11), tetracycline 90.9% (10/11), and nalidixic acid 63.6% (7/11). This mostly corroborates the resistance genes that they carried for sulfonamides (sul1 and sul2), trimethoprim (dfrA and dfrB), aminoglycosides [aac(3)-IId, strA, and strB], tetracycline [tet(B) and tet(D)], and fluoroquinolones (qepA4). They harbored plasmid replicon types IncF, IncX, IncQ, and Col and carried bla_CTX–M–15 and bla_TEM–1B genes generally found on the same contigs as the IncF plasmid replicon. Although epidemiologically unrelated, the strains formed three separate sequence type–phylogroup–serotype-specific clusters: C1, C2, and C3. Cluster C1 included five strains (3 to 13 SNPs) belonging to ST167, phylogroup A, and serotype O9:H21; the two C2 strains (11 SNPs) belong to ST156, phylogroup B1, and serotype ONT:H28; and C3 was made up of four strains (SNPs ranged from 4 to 17) of ST636, phylogroup B2, and serotype O45:H7. The common virulence gene gad was reported in all strains. In addition, strains in C2 and C3 possessed iss, lpfA, and nfaE virulence genes, and the vat gene was found only in C3. The present study reports the occurrence of multidrug-resistant ESBL-producing E. coli carrying plasmid-mediated ESBL genes in offshore water and Nile perch in Lake Victoria. Strains formed three clonal clusters of unknown origin. This study reveals that the Lake may serve as reservoir for ESBL-producing bacteria that can be transmitted by fish as a food chain hazard of One-Health concern.

Antimicrobials and resistant bacteria in global fish farming and the possible risk for public health

ABSTRACT: The use of antimicrobials in fish farming is a reflection of the fast aquaculture development worldwide. The intensification of aquaculture to achieve market demands could lead to an increase in infectious diseases by pathogenic bacteria. Consequently, antimicrobials act as controls for emerging infectious diseases, but their use must follow the rules and regulations of the country where the activity is performed. Although the regulations impose limits to the use of antimicrobials in fish farming, many studies show that resistant bacteria are isolated from this system. The selection of resistant bacteria is not limited only to the use of antimicrobials, but also to co-selection of resistance genes or even with cross-resistance processes. Resistant bacteria from fish farming are a serious concern because they can be acquired by humans with handling or food chain, which may represent a public health problem. In the present review, we present an overview of antimicrobials use in aquaculture, the antimicrobial resistance and the impact of antimicrobial and bacterial resistance from a public health perspective.

Food-to-Humans Bacterial Transmission

Microorganisms vehiculated by food might benefit health, cause minimal change within the equilibrium of the host microbial community or be associated with foodborne diseases. In this chapter we will focus on human pathogenic bacteria for which food is conclusively demonstrated as their transmission mode to human. We will describe the impact of foodborne diseases in public health, the reservoirs of foodborne pathogens (the environment, human and animals), the main bacterial pathogens and food vehicles causing human diseases, and the drivers for the transmission of foodborne diseases related to the food-chain, host or bacteria features. The implication of food-chain (foodborne pathogens and commensals) in the transmission of resistance to antibiotics relevant to the treatment of human infections is also evidenced. The multiplicity and interplay of drivers related to intensification, diversification and globalization of food production, consumer health status, preferences, lifestyles or behaviors, and bacteria adaptation to different challenges (stress tolerance and antimicrobial resistance) from farm to human, make the prevention of bacteria-food-human transmission a modern and continuous challenge. A global One Health approach is mandatory to better understand and minimize the transmission pathways of human pathogens, including multidrug-resistant pathogens and commensals, through food-chain.

Characterization of Mechanisms Lowering Susceptibility to Flumequine among Bacteria Isolated from Chilean Salmonid Farms

Despite their great importance for human therapy, quinolones are still used in Chilean salmon farming, with flumequine and oxolinic acid currently approved for use in this industry. The aim of this study was to improve our knowledge of the mechanisms conferring low susceptibility or resistance to quinolones among bacteria recovered from Chilean salmon farms. Sixty-five isolates exhibiting resistance, reduced susceptibility, or susceptibility to flumequine recovered from salmon farms were identified by their 16S rRNA genes, detecting a high predominance of species belonging to the Pseudomonas genus (52%). The minimum inhibitory concentrations (MIC) of flumequine in the absence and presence of the efflux pump inhibitor (EPI) Phe-Arg-β-naphthylamide and resistance patterns of isolates were determined by a microdilution broth and disk diffusion assays, respectively, observing MIC values ranging from 0.25 to >64 µg/mL and a high level of multi-resistance (96%), mostly showing resistance to florfenicol and oxytetracycline. Furthermore, mechanisms conferring low susceptibility to quinolones mediated by efflux pump activity, quinolone target mutations, or horizontally acquired resistance genes (qepA, oqxA, aac(6′)-lb-cr, qnr) were investigated. Among isolates exhibiting resistance to flumequine (≥16 µg/mL), the occurrence of chromosomal mutations in target protein GyrA appears to be unusual (three out of 15), contrasting with the high incidence of mutations in GyrB (14 out of 17). Bacterial isolates showing resistance or reduced susceptibility to quinolones mediated by efflux pumps appear to be highly prevalent (49 isolates, 75%), thus suggesting a major role of intrinsic resistance mediated by active efflux.

The Emergence of Chromosomally Located bla CTX-M-55 in Salmonella From Foodborne Animals in China

The emergence and increase in prevalence of resistance to cephalosporins amongst isolates of Salmonella from food animals imposes a public health threat. The aim of the present study was to investigate the prevalence and characteristics of CTX-M-producing Salmonella isolates from raw meat and food animals. 27 of 152 (17.76%) Salmonella isolates were ESBL-positive including 21/70 (30%) from food animals and 6/82 (7.32%) from raw meat. CTX-M-55 was the most prevalent ESBL type observed (12/27, 44.44%). 7 of 12 CTX-M-55-positive Salmonella isolates were Salmonella Indiana, 2 were Salmonella Typhimurium, 2 were Salmonella Chester, and the remaining isolate was not typeable. Eight CTX-M-55-positive Salmonella isolates were highly resistant to fluoroquinolones (MIC_CIP = 64 ug/mL) and co-harbored aac(6’)-Ib-cr and oqxAB. Most of the CTX-M-55 positive isolates (11/12) carried bla_CTX-M-55 genes on the chromosome, with the remaining isolate carrying this gene on a transferable 280 kb IncHI2 plasmid. A chromosomal bla_CTX-M-55 gene from one isolate transferred onto a 250 kb IncHI2 plasmid which was subsequently conjugated into recipient strain J53. PFGE and MLST profiles showed a wide range of strain types were carrying bla_CTX-M-55. Our study demonstrates the emergence and prevalence of foodborne Salmonella harboring a chromosomally located bla_CTX-M-55 in China. The co-existence of PMQR genes with bla_CTX-M-55 in Salmonella isolates suggests co-selection and dissemination of resistance to both fluoroquinolones and cephalosporins in Salmonella via the food chain in China represents a public health concern.

Human, animal and environmental contributors to antibiotic resistance in low-resource settings: integrating behavioural, epidemiological and One Health approaches

Antibiotic resistance (ABR) is recognized as a One Health challenge because of the rapid emergence and dissemination of resistant bacteria and genes among humans, animals and the environment on a global scale. However, there is a paucity of research assessing ABR contemporaneously in humans, animals and the environment in low-resource settings. This critical review seeks to identify the extent of One Health research on ABR in low- and middle-income countries (LMICs). Existing research has highlighted hotspots for environmental contamination; food-animal production systems that are likely to harbour reservoirs or promote transmission of ABR as well as high and increasing human rates of colonization with ABR commensal bacteria such as Escherichia coli However, very few studies have integrated all three components of the One Health spectrum to understand the dynamics of transmission and the prevalence of community-acquired resistance in humans and animals. Microbiological, epidemiological and social science research is needed at community and population levels across the One Health spectrum in order to fill the large gaps in knowledge of ABR in low-resource settings.

Dissemination of Escherichia coli carrying plasmid-mediated quinolone resistance (PMQR) genes from swine farms to surroundings

Different samples were collected from three swine farms in China to investigate the spread of antibiotic-resistant Escherichia coli. A total of 130 E. coli isolates were obtained from feces, air, river water, silt, and soil samples and characterized. The susceptibility of the E. coli isolates to 19 antibiotics was tested. The results revealed that the resistance rates of the E. coli isolates against 9 antibiotics were high. The minimum inhibitory concentration (MIC) values of ciprofloxacin, ofloxacin, and nalidixic acid were mainly in the ranges of 2-64, 8-64, and 8-64 μg/ml. The plasmid-mediated quinolone resistance (PMQR) genes qnr, aac(6')-Ib-cr, qepA, and oqxAB were detected by polymerase chain reaction (PCR), and the similarity of E. coli from different samples was identified by pulsed-field gel electrophoresis (PFGE). The detection rates of the qnrA, qnrB, qnrS, aac(6')-Ib-cr, qepA, and oqxAB genes in the E. coli isolates from three swine farms were in the range of 10.87-23.08%, 13.04-20.51%, 40.00-43.48%, 30.43-38.46%, 6.52-12.82%, and 7.69-17.39%, respectively. The PFGE result showed that 49% (49/100) of isolates originating from air, river water, soil, and silt samples had ≥85% similarity to fecal-obtained isolates, and 40.82% (20/49) of them shared the same PMQR genes with fecal-obtained isolates. This indicated that E. coli carrying PMQR genes and originating from feces in swine farms could spread to the external environment, which could be a potential threat to the public environment and human health.

Comparative Analysis of Antimicrobial Resistance, Integrons, and Virulence Genes Among Extended-Spectrum β-Lactamase-Positive Laribacter hongkongensis from Edible Frogs and Freshwater Fish

Aquatic animals are now recognized to be major hosts of potentially pathogenic Laribacter hongkongensis. A comparative study was carried out among extended-spectrum β-lactamase (ESBL)-producing L. hongkongensis isolated from frogs (47 isolates) and fish (41 isolates) to examine phenotypic and genotypic antimicrobial resistance profiles, integrons, virulence factors, and genetic relatedness. Isolates from frogs showed a higher incidence of antibiotic resistance compared with those from fish for most of the antimicrobials tested, especially trimethoprim-sulfamethoxazole, tetracycline, ciprofloxacin, levofloxacin, and streptomycin. Multidrug-resistant strains were also found more frequently among frog isolates (5.44 traits on average) than among fish isolates (3.29 traits). In frog isolates, class 1 integrons and the resistance genes sul1, sul2, tetA, tetR, and aac(6')-Ib-cr showed a clearly higher incidence compared with isolates from fish. In contrast, bla_TEM-1 was higher in fish isolates than in frog isolates. Correlation analysis showed that sul1, sul2, tetA, and tetR were significantly associated with class 1 integrons in frog isolates. The correlations indicated a potential co-selection risk of bacterial resistance to antibiotics. In addition, the distribution of three virulence-associated determinants for the type IV bundle-forming pili gene (bfpA), ferric aerobactin receptor gene (iucD), and iron-responsive element gene (ireA) was markedly higher in strains isolated from frogs than in those isolated from fish. No obvious genetic relatedness was observed between both populations. The large differences found in the incidence of antibiotic resistance, integrons along with the multiple resistance genes, virulence factors, and genetic fingerprints determined by pulsed-field gel electrophoresis suggest a high degree of antibiotic resistance and pathogenicity potential of ESBL-producing L. hongkongensis from isolates found in frogs.

Dissemination of CTX-M-Producing Escherichia coli in Freshwater Fishes From a French Watershed (Burgundy)

The burden of extended-spectrum β-lactamases producing Escherichia coli (ESBL-Ec), has increased over several decades. Freshwater ecosystems are suspected to play an important ecological and evolutionary role in driving the dissemination of antimicrobial resistance. The aim of our study was to decipher the occurrence of ESBL-Ec in a small watershed (Ouche river, Burgundy, France), targeting environmental matrices and fishes. Among cefotaxime resistant E. coli (ctxR Ec) isolates, we detected and characterized 36 ESBL-Ec from water, biofilm and fish guts. ctxR Ec and ESBL-Ec were found in samples from sites near the first small town, located downstream from the watershed which was studied. Treatment of urban wastewater by waste water treatment plants (WWTP), might therefore be a major potential source of ctxR Ec and thus of ESBL-Ec. Prevalence of total E. coli and ctxR Ec in fish guts ranged between 0 to 92% and 0 to 85%; respectively, depending on the sampling site and the fish species. The diet of fish (predator or omnivore) seems to strongly influence the prevalence of total E. coli and ESBL-Ec. Extended spectrum beta-lactamases produced by the isolates from this study belonged to the CTX-M family (CTX-M group 1 and 9). Moreover, some environmental ESBL-Ec proved to share genotypic features (MLST types) with isolates which originated from 8 WWTP effluents discharged in the Ouche river and with the sequence type ST131, which is widely described in clinical isolates. Ninety-seven % (97%) of ESBL-Ec from the study harbored additional antibiotic resistances and can thus be considered as multi drug resistant (MDR) bacteria. Finally, 53% of the ESBL-Ec strains harbored class 1 integron-integrase (intl1). These results are discussed with the perspective of defining indicators of antibiotic resistance contamination in freshwater ecosystems.

Inflow water is a major source of trout farming contamination with Salmonella and multidrug resistant bacteria

The impact of European aquaculture, namely trout farms, in the spread of antibiotic resistance and/or zoonotic pathogens has been scarcely addressed. Moreover, aquaculture contamination sources and bacterial dissemination routes have been barely explored. In this study, we assessed the contribution of Portuguese land-based intensive rainbow trout farms and retailed market trout to the spread of Salmonella and bacteria carrying clinically-relevant antibiotic resistance genes (ARGs) as well as inflow water and feed as possible sources of those contaminants. Cultural and molecular methods were used to analyse 53 fish farm samples (upstream/downstream water and sediments, tanks and trout) and 25 marketed trout. Plasmid-mediated quinolone resistance (PMQR) genes were found in 21% (n = 11/53) of samples (water/sediment/feed/trout), from all collection points (upstream/within/downstream tanks) and seasons, as well as in 12% (n = 3/25) of marketed trout (3 supermarkets). PMQR genes (qnrS1-S2-S3, qnrB7-B19, qnrD1, oqxAB) were detected in Enterobacteriaceae or Aeromonas hydrophila. An E. coli strain producing extended-spectrum-beta-lactamase SHV-12 was detected in all sampled points of a fish farm. Salmonella (4 serotypes, including S. Newport-ST118) was detected in 26% (n = 14/53) of the samples from both farms (water/sediment upstream/within tanks). The clinically-relevant plasmid-mediated colistin resistance mcr genes were not detected. However, colistin resistant S. Abony with new mutations in the chromosomal pmrA and pmrB genes was observed. Identical Salmonella and SHV-12-producing E. coli strains (by PFGE/MLST) in water upstream and within trout tanks points to inflow-water of trout farms as an important source of pathogenic bacteria and ARG contamination. These results highlight the need to define microbiological standards for water supplying fish farms in the EU and to establish surveillance and control strategies to limit bacterial transmission associated with this fastest growing food sector worldwide.

Early-Onset Neonatal Sepsis with Extended Spectrum Beta-Lactamase Producing Escherichia Coli in Infants Born to South and South East Asian Immigrants: A Case Series

Extended-spectrum β -lactamase (ESBL)-producing Enterobacteriaceae represent a major worldwide threat. We present three cases of early onset ESBL Escherichia coli sepsis in infants born to families from South and Southeast Asia to inform the practitioner community about this emerging threat. Infants with suspected sepsis, whose mother is from Asia or Southeast Asia, should be suspected of having an infection with an ESBL-producing organism, and practitioners should strongly consider adding a carbapenem to their usual initial antibiotic regimen.

The 2017 Garrod Lecture: Genes, guts and globalization

The widespread use of antibacterial drugs over the last 70 years has brought immense benefits to human health at the price of increasing drug inefficacy. Antibacterial agents have a strong selective effect in both favouring resistant strains and allowing particular species and families of bacteria to prosper, especially in the healthcare setting. Whilst important Gram-positive bacterial pathogens such as Staphylococcus aureus and Streptococcus pneumoniae caused concern over the last 20 years because of the spread of antibiotic-resistant strains, Enterobacteriaceae have become the biggest challenge. They have very efficient mechanisms for genetic exchange, as illustrated by the emergence and rapid spread of CTX-M β-lactamases and the carbapenemases. The unique epidemiology of Enterobacteriaceae, with substantial numbers colonizing the mammalian gut and subsequent release into and spread in the environment, presents a significant threat to human health because of the high levels of exposure for the whole community. The use of antimicrobials in agriculture combined with global movements of people, animals and food, arising from worldwide industrialization, generates a diversity and level of resistance not seen previously. Control will require globally coordinated interventions similar to those needed to ameliorate climate change.

Complex pollution of antibiotic resistance genes due to beta-lactam and aminoglycoside use in aquaculture farming

The prevalence of antibiotic resistance in the modern world has raised global concerns for public health. Establishing relationships between antibiotic use and antibiotic resistance genes (ARGs) is essential to understanding the dissemination and accumulation of ARGs in a human-impacted environment. In this study, ARG profiles in the sediments from a bullfrog farm, where penicillin and amoxicillin (beta-lactams) and gentamicin (aminoglycoside) were used for prophylactic purposes, were analyzed using metagenomic approaches. Analysis of both extracellular and intracellular DNA (eDNA and iDNA) demonstrated that use of the above-mentioned antibiotics led to complex pollution of ARGs not only related to beta-lactams and aminoglycoside but also to sulfonamides, tetracyclines, and macrolides. Most of the ARGs in the sediments from the bullfrog farm were likely carried by plasmids. A significant correlation was observed between the total abundance of ARG-related plasmids and that of plasmid-carrying ARGs. Approximately 85% of the plasmids likely present in the sediment from the bullfrog farm possessed at least 3 ARG subtypes, which conferred the resistance of bacterial hosts to different antibiotic categories. Our results suggest that antibiotics could lead to complex pollution of ARGs unrelated to those administered due to the concurrence of ARGs in the plasmids.

Abundance of antibiotic resistance genes and bacterial community composition in wild freshwater fish species

This study was aimed to determine the abundance of four antibiotic resistance genes (bla_TEM, ermB, qnrS and sulI), as well as bacterial community composition associated with the intestinal mucus of wild freshwater fish species collected from the Foix and La Llosa del Cavall reservoirs, which represent ecosystems with high and low anthropogenic disturbance, respectively. Water and sediments from these reservoirs were also collected and analyzed to determine the pollution level by antibiotics. The bla_TEM gene was only detected in brown trout and Ebro barbel, which were collected from La Llosa del Cavall reservoir. In contrast, the sulI and qnrS genes were only detected in common carp, which were collected from the Foix reservoir. Although the ermB gene was also detected in common carp, the values were below the limit of quantification. Likewise, water and sediment samples from the Foix reservoir had higher concentrations and more classes of antibiotics than those from La Llosa del Cavall. Pyrosequencing analysis of 16S rRNA genes revealed significant differences in bacterial communities associated with the intestinal mucus of fish species. Therefore, these findings suggest that anthropogenic activities are not only increasing the pollution of aquatic environments, but also contributing to the emergence and spread of antibiotic resistance in organisms that inhabit such environments.

Occurrence and human dietary assessment of fluoroquinolones antibiotics in cultured fish around tai lake, China

Fluoroquinolone antibiotics are widely used in the production of aquatic products and considered to be a significant contributing factor to the burden of both natural and aquaculture environments. However, the main types of fluoroquinolones present in aquaculture systems have not been determined. The objectives of the present study were to explore the occurrence of residual fluoroquinolone antibiotics in fish muscle tissues sampled from across the entire aquaculture season in the Tai Lake basin in China and to assess the dietary risks associated with the upcoming vendible fish in the last month of the aquaculture season. Fluoroquinolones were detected in 95.69% of all fish samples, and the concentrations ranged from the limit of quantification (LOQ) to 47 108.00 μg · kg^-1 . Enrofloxacin contributed the most among the 9 fluoroquinolone antibiotics tested. Of the 4 fish species studied, enrofloxacin was present in bream at significant (p < 0.05) concentrations in August, with an average value of 321.45 μg · kg^-1 , while enrofloxacin concentrations peaked in crab and shrimp in September, with average values of 6949.60 and 460.82 μg · kg^-1 , respectively. However, different patterns were observed in perch, suggesting that other categories of antibiotics may be used in the production of this fish. Dietary risk assessment showed that the residual levels and estimated daily intake in bream, perch, and shrimp were far below the maximum residual level and acceptable daily intake. However, the average residual level in crab exceeded the maximum residual level, and the estimated daily intake value accounted for 78.49% of the acceptable daily intake, indicating potential consumption risk. In summary, the present study aims to guide the production and consumption of aquatic products. Environ Toxicol Chem 2017;36:2899-2905. © 2017 SETAC.

First Detection of CTX-M-1 in Extended-Spectrum β-Lactamase-Producing Escherichia coli in Seafood from Tunisia

The purpose of this study was to determine the carriage rate of Escherichia coli isolates in seafood, to analyze the phenotype and genotype of antimicrobial resistance in the recovered isolates, and to characterize extended-spectrum β-lactamase (ESBL) E. coli producers. E. coli isolates were recovered from 24 (34.3%) of the 70 seafood samples analyzed, and one isolate per sample was further characterized. Antibiotic resistance was determined by the disk diffusion method in the 24 isolates, with the following results (number of resistant isolates): tetracycline (8), streptomycin (7), ampicillin (6), trimethoprim-sulfamethoxazole (4), chloramphenicol (4), ciprofloxacin (3), cefotaxime (2), and ceftazidime (2). Six isolates showed a multiresistant phenotype (including at least three families of antibiotics). Among tetracycline-resistant E. coli isolates, tet(A) was detected in five isolates and tet(B) in two isolates. The qnr(A) or aac(6')-1b-cr genes were detected in two ciprofloxacin-resistant E. coli isolates, and the sul2 gene in two trimethoprim-sulfamethoxazole-resistant isolates. ESBL-containing E. coli isolates, carrying the blaCTX-M-1 gene, were detected in 2 of the 70 seafood samples, obtained from gilt-head bream aquaculture. The ESBL isolates were typed phylogenetically and by multilocus sequence typing, and they were ascribed to lineage ST48/A and to the new ST3497/B1; these isolates carried the fimA, aer, and papGIII virulence genes. One of the ESBL-producing E. coli isolates carried an unusual class 1 integron (with the array dfr32-ereA-aadA1). Seafood could be a source of multiresistant E. coli isolates for the aquatic environment, and these could enter the food chain.

High Prevalence of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Wild Fish from the Mediterranean Sea in Algeria

AIM

We investigated the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae among wild fish from the coast of Bejaia (Algeria) in the Mediterranean Sea.

RESULTS

From March 2012 to August 2013, gut and gill samples of wild fish were screened for the presence of ESBL-producing Enterobacteriaceae. Strains were characterized with regard to antibiotic resistance, β-lactamase content, plasmid-mediated quinolone resistance, aminoglycoside resistance genes, and clonality (repetitive sequence-based polymerase chain reaction profiles and multilocus sequence typing). Virulence traits were performed for Escherichia coli and Klebsiella pneumoniae isolates. Of the 300 fish studied, 64 (21.3%) isolates were screened as positive for ESBL producing by the double-disc method. The isolates corresponded to E. coli, K. pneumoniae, Enterobacter cloacae, Morganella morganii, Citrobacter freundii, and Proteus vulgaris. A predominance of bla_CTX-M gene was observed with a prevalence of 60.5% (n = 46). Furthermore, our study describes the association of important coresistance and virulence factors in E. coli and K. pneumoniae. Twelve of the ESBL producers carried genes of the qnr family and oqxAB gene and six carried the aac(6')-Ib-cr gene.

CONCLUSIONS

Our results highlight for the first time the diffusion of multidrug-resistant Enterobacteriaceae isolates carrying resistance and virulence genes in fish from the Mediterranean Sea in Algeria.

The Rising Tide of Antimicrobial Resistance in Aquaculture: Sources, Sinks and Solutions

As the human population increases there is an increasing reliance on aquaculture to supply a safe, reliable, and economic supply of food. Although food production is essential for a healthy population, an increasing threat to global human health is antimicrobial resistance. Extensive antibiotic resistant strains are now being detected; the spread of these strains could greatly reduce medical treatment options available and increase deaths from previously curable infections. Antibiotic resistance is widespread due in part to clinical overuse and misuse; however, the natural processes of horizontal gene transfer and mutation events that allow genetic exchange within microbial populations have been ongoing since ancient times. By their nature, aquaculture systems contain high numbers of diverse bacteria, which exist in combination with the current and past use of antibiotics, probiotics, prebiotics, and other treatment regimens-singularly or in combination. These systems have been designated as "genetic hotspots" for gene transfer. As our reliance on aquaculture grows, it is essential that we identify the sources and sinks of antimicrobial resistance, and monitor and analyse the transfer of antimicrobial resistance between the microbial community, the environment, and the farmed product, in order to better understand the implications to human and environmental health.

Characterization of a P1-like bacteriophage carrying CTX-M-27 in Salmonella spp. resistant to third generation cephalosporins isolated from pork in China

The aim of this study was to elucidate the epidemiology of third generation cephalosporin resistant Samonella isolates from pork of a slaughterhouse in China and the features of transferable elements carrying bla_CTX-M genes. One hundred and twenty-six (7.3%) Salmonella isolates were identified; S. Derby and S. Rissen were the most two prevalent serotypes. Among these isolates 20 (15.8%) were resistant to third generation cephalosporins and nine of them carried bla_CTX-M-27. S1-PFGE and replicon typing of bla_CTX-M-27-carrying plasmids showed that seven were untypeable plasmids of about 104 Kb and two were IncP plasmids of about 300 Kb. Complete sequence analysis of one PBRT-untypeable plasmid showed it was a P1-like bateriophage, named SJ46, which contained a non-phage-associated region with several mobile elements, including Tn1721, ISEcp1B and IS903D. The other six 104 Kb PBRT-untypeable bla_CTX-M-27-carrying plasmids also harboured the same phage-insertion region of SJ46 suggesting that they were the same P1-like bacteriophage. PFGE profiles of the parental strains revealed both potential vertical and horizontal spread of this P1-like bla_CTX-M-27-containing element. Additionally, the representative gene of the P1 family bacteriophage, repL, was detected in 19.0% (24/126) of the isolates. This study indicated a potential role of P1-family bacteriophage in capture and spread of antimicrobial resistance in pathogens.

Bacterial plasmid-mediated quinolone resistance genes in aquatic environments in China

Emerging antimicrobial resistance is a major threat to human’s health in the 21^st century. Understanding and combating this issue requires a full and unbiased assessment of the current status on the prevalence of antimicrobial resistance genes and their correlation with each other and bacterial groups. In aquatic environments that are known reservoirs for antimicrobial resistance genes, we were able to reach this goal on plasmid-mediated quinolone resistance (PMQR) genes that lead to resistance to quinolones and possibly also to the co-emergence of resistance to β-lactams. Novel findings were made that qepA and aac-(6′)-Ib genes that were previously regarded as similarly abundant with qnr genes are now dominant among PMQR genes in aquatic environments. Further statistical analysis suggested that the correlation between PMQR and β-lactam resistance genes in the environment is still weak, that the correlations between antimicrobial resistance genes could be weakened by sufficient wastewater treatment, and that the prevalence of PMQR has been implicated in environmental, pathogenic, predatory, anaerobic, and more importantly, human symbiotic bacteria. This work provides a comprehensive analysis of PMQR genes in aquatic environments in Jinan, China, and provides information with which combat with the antimicrobial resistance problem may be fought.

Current and future antimicrobial resistance issues for the Australian pig industry

Antimicrobial use and antimicrobial resistance (AMR) in intensive pig production and its potential impacts to human and animal health are very much under the spotlight, both internationally, and within Australia. While the majority of AMR of medical importance is associated with the exclusive use of antimicrobials in humans, resistance in zoonotic foodborne pathogens such as Salmonella and Campylobacter, and livestock commensal bacteria such as Escherichia coli and Enterococcus spp., is under increased scrutiny. This is primarily due to the current reliance on many of the same drug classes as used in human medicine for treatment and control of bacterial diseases of livestock. Furthermore, the development of multidrug resistance in pathogens such as enterotoxigenic E. coli may drive off-label use of critically important drug classes such as 3rd-generation cephalosporins. This could lead to the emergence and amplification of resistance genes of potential public health significance in both pathogens and commensal bacteria. Livestock-associated and community-associated methicillin-resistant Staphylococcus aureus has also recently been detected in Australian pigs as a result of human-to-animal transmission and are a potential public health issue for in-contact piggery workers. Australia is in a unique position compared with many of its international trading partners due to its isolation, ban on importation of livestock and conservative approach to antimicrobial registration, including reservation of the fluoroquinolone class for use in humans and companion animals only. Cross-sectional AMR surveys of pathogens and commensals in healthy pigs have identified only low frequency of resistance to critically important drug classes. Nevertheless, resistance to critically important antimicrobials has emerged and careful antimicrobial stewardship is required to ensure that these low levels do not increase. In this report, we review AMR of significance to the Australian pig industry and identify potential prevention and control measures.