Phenotypic and molecular detection of CTX-M-beta-lactamases produced by Escherichia coli and Klebsiella spp

Emergence of Salmonella Infantis carrying the pESI-like plasmid from eggs in egg grading and packing plants in Korea

The plasmid of emerging S. Infantis (pESI) or pESI-like plasmid in Salmonella enterica Infantis are consistently reported in poultry and humans worldwide. However, there has been limited research on these plasmids of S. Infantis isolated from eggs. Therefore, this study aimed to analyze the prevalence and characteristics of S. Infantis carrying the pESI-like plasmid from eggs in egg grading and packing plants. In this study, the pESI-like plasmid was only detected in 18 (78.3%) of 23 S. Infantis isolates, and it was absent in the other 9 Salmonella serovars. In particular, S. Infantis isolates carrying the pESI-like plasmid showed the significantly higher resistance to β-lactams, phenicols, cephams, aminoglycosides, quinolones, sulfonamides, and tetracyclines than Salmonella isolates without the pESI-like plasmid (p < 0.05). Moreover, all S. Infantis isolates carrying the pESI-like plasmid were identified as extended-spectrum β-lactamase (ESBL) producer, harboring the blaCTX-M-65 and blaTEM-1 genes, and carried non-β-lactamase resistance genes (ant(3'')-Ia, aph(4)-Ia, aac(3)-IVa, aph(3')-Ic, sul1, tetA, dfrA14, and floR) against five antimicrobial classes. However, all isolates without the pESI-like plasmid only carried the blaTEM-1 gene among the β-lactamase genes, and either had no non-β-lactamase resistance genes or harbored non-β-lactamase resistance genes against one or two antimicrobial classes. Furthermore, all S. Infantis isolates carrying the pESI-like plasmid carried class 1 and 2 integrons and the aadA1 gene cassette, but none of the other isolates without the pESI-like plasmid harbored integrons. In particular, D87Y substitution in the gyrA gene and IncP replicon type were observed in all the S. Infantis isolates carrying the pESI-like plasmid but not in the S. Infantis isolates without the pESI-like plasmid. The distribution of pulsotypes between pESI-positive and pESI-negative S. Infantis isolates was clearly distinguished, but all S. Infantis isolates were classified as sequence type 32, regardless of whether they carried the pESI-like plasmid. This study is the first to report the characteristics of S. Infantis carrying the pESI-like plasmid isolated from eggs and can provide valuable information for formulating strategies to control the spread of Salmonella in the egg industry worldwide.

Exploring the presence, genomic traits, and pathogenic potential of extended-spectrum β-lactamase Escherichia coli in freshwater, wastewater, and hospital effluents

AIMS

The purpose of this work was to study extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) in freshwaters, hospital effluents, and wastewaters during two sampling campaigns in 2021.

METHODS AND RESULTS

Water sampling was performed at 24 stations in the Ourthe watershed in Belgium. A total of 644 ESBL (n = 642) and AmpC (n = 2) E. coli strains were isolated. Disk-diffusion assays were performed following the EUCAST's recommendations. All strains were tested for the presence of blaCTX-M-1, blaCTX-M-2, and blaCTX-M-9 gene groups by PCR. Genes belonging to blaCTX-M-1 and blaCTX-M-9 groups were detected, respectively, in 73.6% and 14.9% of the strains. No blaCTX-M-2 group's gene was found. A subset of strains (n = 40) was selected for whole genome sequencing. Escherichia coli serotype O18: H7 ST 1463 was predominant (n = 14) in the sequenced strains and showed pathogenicity in the Galleria mellonella larvae model. β-lactamase genes identified were blaCTX-M (n = 21), with blaCTX-M-15 mostly represented (n = 15), as well as blaTEM (n = 11), blaOXA (n = 7), blaSHV (n = 9), and carbapenemase (CP) genes were observed in several strains-blaKPC-3 (n = 19), blaNDM-1 (n = 1), blaVIM-1 (n = 2), and blaOXA-244 (n = 2)-even from freshwaters.

CONCLUSIONS

ESBL-EC are widely distributed in the aquatic environment in Belgium and contain a variety of ESBL and CP genes.

Antibiotic resistance genes profile in the surface sediments of typical aquaculture areas across 15 major lakes in China

Aquatic farming is considered as a major source of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) for the natural environment of the lakes. ARB and ARGs in the natural environment have increased quickly because of the human activities. Here, we have profiled the diversity and abundance of ARGs in sediments from the typical aquaculture areas around 15 major lakes in China using PCR and qPCR, and further assessed the risk factor shaping the occurrence and distribution of ARGs. And class 1, 2 and 3 integrons were initially detected by PCR with specific primers. ARGs were widely distributed in the lakes: Weishan Lake and Poyang Lake showed high diversity of ARGs, followed by Dongting Lake, Chao Lake and Tai Lake. Generally, the ARGs in the Middle-Lower Yangtze Plain were more abundant than those in the Qinghai-Tibet Plateau. Tetracycline resistance genes (tet(C), tet(A) & tet(M)) were prominent in sediments, and the next was AmpC β-lactamase gene group BIL/LAT/CMY, and the last was the genes resistance to aminoglycoside (strA-strB). Partial least squares path modeling analysis (PLS-PMA) revealed that livestock had a significant direct effect on the distribution of ARGs in lakes, and population might indirectly influence the profiles of ARGs by affecting the scale of livestock and aquaculture. The detectable rate of class 1, 2 and 3 integrons were 80%, 100% and 46.67%, respectively. The prevalence of integrons might play a key role in promoting more frequent horizontal gene transfer (HGT) events, resulting in the environmental mobilization and dissemination of ARGs between bacteria.

Molecular characterization of Escherichia coli producing extended-spectrum β-lactamase CTX-M-14 and CTX-M-28 in Mexico

The spread of ESBL-producing Escherichia coli has constantly increased in both clinical and community infections. Actually, the main ESBL reported is the CTX-M family, which is widely disseminated between the Enterobacteriaceae family. The epidemiology of the CTX-M family shows the CTX-M-15 variant dominating worldwide, followed by CTX-M-14 and CTX-M-27. The specific ESBL-producing E. coli clones included mainly the sequence types ST131, ST405, and ST648. In this report, we present the molecular characterization of ESBL-producing E. coli clinical isolates from eight hospitals in Mexico. From a collection of 66 isolates, 39 (59%) were identified as blaCTX-M-14 and blaCTX-M-27 belonging to the group CTX-M-9. We identified 25 (38%) isolates, producing blaCTX-M-28 belonging to the group CTX-M-1. blaCTX-M-2 and blaTEM-55 were identified in one isolate, respectively. Fourteen isolates (21%) were positive for blaCTX-M-14 (13%) and blaCTX-M-28 (7.3%) that were selected for further analyses; the antimicrobial susceptibility showed resistance to ampicillin (> 256 µg/mL), cefotaxime (> 256 µg/mL), cefepime (> 64 µg/mL), and ceftazidime (16 µg/mL). The ResFinder analysis showed the presence of the antimicrobial resistance genes aacA4, aadA5, aac(3)lla, sul1, dfrA17, tet(A), cmlA1, and blaTEM-1B. PlasmidFinder analysis identified in all the isolates the replicons IncFIB, which were confirmed by PCR replicon typing. The MLST analysis identified isolates belonging to ST131, ST167, ST405, and ST648. The ISEcp1B genetic element was found at 250 pb upstream of blaCTX-M-14 and flanked by the IS903 genetic element at 35 pb downstream. The IS1380-like element ISEc9 family transposase was identified at 250 pb upstream of blaCTX-M-14 and flanked downstream by the IS5/IS1182 at 80 pb. Our study highlights the significant prevalence of CTX-M-14 and CTX-M-28 enzymes as the second-most common ESBL-producing E. coli among isolates in Mexican hospitals. The identification of specific sequence types in different regions provides valuable insights into the correlation between ESBL and E. coli strains. This contribution to understanding their epidemiology and potential transmission routes is crucial for developing effective strategies to mitigate the spread of ESBL-producing E. coli in healthcare settings.

High levels of multidrug-resistant isolates of genetically similar Salmonella 1,4, [5],12:I:- from Brazil between 1983 and 2020

Introduction. Salmonella 1,4, [5],12:i:- strains with different antimicrobial resistance profiles have been associated with foodborne disease outbreaks in several countries. In Brazil, S. 1,4, [5],12:i:- was identified as one of the most prevalent serovars in São Paulo State during 2004-2020.Gap Statement. However, few studies have characterized this serovar in Brazil.Aim. This study aimed to determine the antimicrobial resistance profiles of S. 1,4, [5],12:i:- strains isolated from different sources in Southeast Brazil and compare their genetic diversity.Methodology. We analysed 113 S. 1,4, [5],12:i:- strains isolated from humans (n=99), animals (n=7), food (n=5) and the environment (n=2) between 1983 and 2020. Susceptibility testing against 13 antimicrobials was performed using the disc diffusion method for all the strains. Plasmid resistance genes and mutations in the quinolone resistance-determining regions were identified in phenotypically fluoroquinolone-resistant strains. Molecular typing was performed using enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) for all strains and multilocus sequence typing (MLST) for 40 selected strains.Results. Of the 113 strains, 54.87 % were resistant to at least one antimicrobial. The highest resistance rates were observed against ampicillin (51.33 %), nalidixic acid (39.82 %) and tetracycline (38.05 %). Additionally, 39 (34.51 %) strains were classified as multidrug-resistant (MDR). Nine fluoroquinolone-resistant strains exhibited the gyrA mutation (Ser96→Tyr96) and contained the qnrB gene. The 113 strains were grouped into two clusters using ERIC-PCR, and most of strains were present in one cluster, with a genetic similarity of ≥80 %. Finally, 40 strains were typed as ST19 using MLST.Conclusion. The prevalence of MDR strains is alarming because antimicrobial treatment against these strains may lead to therapeutic failure. Furthermore, the ERIC-PCR and MLST results suggested that most strains belonged to one main cluster. Thus, a prevalent subtype of Salmonella 1,4, [5],12:i:- strains has probably been circulating among different sources in São Paulo, Brazil, over decades.

Multicenter molecular investigation of recurrent Escherichia coli bacteriuria in dogs

Escherichia coli is the most common cause of recurrent urinary tract infection (UTI) in dogs. UTI recurrence comprises of persistent, unresolved E. coli infection or reinfection with a different strain of E. coli. Differentiating between these processes is clinically important but is often impossible with routine diagnostics. We tested the hypothesis that most recurrent canine E. coli bacteriuria is due to recurrence of the same E. coli strain involved in the initial infection. Molecular typing was performed on 98 urinary E. coli isolated from dogs with recurrent bacteriuria from five veterinary diagnostic laboratories in the United States. Of the 42 dogs in this study with multiple E. coli bacteriuria observations, a single strain of E. coli caused recurrent bacteriuria in 26 (62 %) dogs, in some cases on multiple occasions for prolonged periods of time (up to eight months). A single E. coli strain was detected during both subclinical bacteriuria and clinically-apparent UTI in three dogs. Isolates with the P-fimbrial adhesin genes papA and papC were associated with recurrence by the same strain of E. coli. Multiple isolations of a single strain of E. coli associated with recurrent bacteriuria suggests that E. coli may be maintained within the urinary tract of some dogs for prolonged periods of time. In some patients, the same strain can cause both clinical UTI and subclinical bacteriuria. This indicates that in dogs, the urinary bladder may serve as a subclinical, long-term reservoir of E. coli that may cause clinical UTI in the future.

Current status of β-lactam antibiotic use and characterization of β-lactam-resistant Escherichia coli from commercial farms by integrated broiler chicken operations in Korea

β-Lactam antibiotics are one of the most clinical importance in human and veterinary medicine because they are used for both preventive and therapeutic purposes against several gram-positive, gram-negative, and anaerobic organisms. In this study, it was confirmed that β-lactams (81.1%) were found to be significantly prescribed the most among 74 farms in 5 integrated broiler operations, and single prescription (84.6%), 2-day (41.5%) or 3-day (40.0%) administration, and 15 to 22 d of age (67.7%) administration was significantly higher in the farms (P < 0.05). Among the E. coli isolated from 74 farms in 5 integrated broiler operations, β-lactam-resistant E. coli isolates were detected more frequently in fecal sample (94.6%) than in dust sample (60.8%) (P < 0.05). The prevalence of MDR in β-lactam-resistant isolates, ranging from 88.1 to 96.5%, was significantly higher than that in non-β-lactam-resistant isolates (P < 0.05), without significant differences among operations. Of 466 β-lactam-resistant isolates, 432 (92.7%) isolates harbored β-lactamase genes. The non-extended-spectrum β-lactamase (ESBL) gene blaTEM-1 (81.8%) showed the highest prevalence among isolates, followed by the non-ESBL gene blaTEM-135 (6.4%) (P < 0.05). Five ESBL genes, SHV-12, OXA-1, CTX-M-27, CTX-M-55, and CTX-M-65, were found in 0.9 to 6.0% of the isolates. The pAmpC gene blaCMY-2 was detected in 17 isolates (3.6%). These results suggest that feces and dust are important reservoirs of antimicrobial-resistant bacteria, highlighting the need to strengthen farm management regulations, such as cleaning, disinfection, and litter disposal and to reduce the use of antibiotics in broiler operations.

Understanding the genetic basis of the incompatibility of IncK1 and IncK2 plasmids

Antimicrobial resistance is a persistent challenge in human and veterinary medicine, which is often encoded on plasmids which are transmissible between bacterial cells. Incompatibility is the inability of two plasmids to be stably maintained in one cell which is caused by the presence of identical or closely related shared determinants between two plasmids originating from partition or replication mechanisms. For I-complex plasmids in Enterobacteriacae, replication- based incompatibility is caused by the small antisense RNA stem-loop structure called RNAI. The I-complex plasmid group IncK consists of two compatible subgroups, IncK1 and IncK2, for which the RNAI differs only by five nucleotides. In this study we focussed on the interaction of the IncK1 and IncK2 RNAI structures by constructing minireplicons containing the replication region of IncK1 or IncK2 plasmids coupled with a kanamycin resistance marker. Using minireplicons excludes involvement of incompatibility mechanisms other than RNAI. Additionally, we performed single nucleotide mutagenesis targeting the five nucleotides that differ between the IncK1 and IncK2 RNAI sequences of these minireplicons. The obtained results show that a single nucleotide change in the RNAI structure is responsible for the compatible phenotype of IncK1 with IncK2 plasmids. Only nucleotides in the RNAI top loop and interior loop have an effect on minireplicon incompatibility with wild type plasmids, while mutations in the stem of the RNAI structure had no significant effect on incompatibility. Understanding the molecular basis of incompatibility is relevant for future in silico predictions of plasmid incompatibility.

Analyses of Extended-Spectrum-β-Lactamase, Metallo-β-Lactamase, and AmpC-β-Lactamase Producing Enterobacteriaceae from the Dairy Value Chain in India

The consumption of milk contaminated with antibiotic-resistant bacteria poses a significant health threat to humans. This study aimed to investigate the prevalence of Enterobacteriaceae producing β-lactamases (ESBL, MBL, and AmpC) in cow and buffalo milk samples from two Indian states, Haryana and Assam. A total of 401 milk samples were collected from dairy farmers and vendors in the specified districts. Microbiological assays, antibiotic susceptibility testing, and PCR-based genotyping were employed to analyze 421 Gram-negative bacterial isolates. The overall prevalence of β-lactamase genes was 10% (confidence interval (CI) (7-13)), with higher rates in Haryana (13%, CI (9-19)) compared to Assam (7%, CI (4-11)). The identified β-lactamase genes in isolates were blaCMY, blaMOX, blaFOX, blaEBC, and blaDHA, associated with AmpC production. Additionally, blaCTX-M1, blaSHV, and blaTEM were detected as ESBL producers, while blaVIM, blaIMP, blaSPM, blaSIM, and blaGIM were identified as MBL producers. Notably, Shigella spp. were the dominant β-lactamase producers among identified Enterobacteriaceae. This study highlights the presence of various prevalent β-lactamase genes in milk isolates, indicating the potential risk of antimicrobial-resistant bacteria in dairy products. The presence of β-lactam resistance raises concern as this could restrict antibiotic options for treatment. The discordance between genotypic and phenotypic methods emphasizes the necessity for comprehensive approaches that integrate both techniques to accurately assess antibiotic resistance. Urgent collaborative action incorporating rational and regulated use of antibiotics across the dairy value chain is required to address the global challenge of β-lactam resistance.

Comparative genetic characterisation of third-generation cephalosporin-resistant Escherichia coli isolated from integrated and conventional pig farm in Korea

OBJECTIVES

Pig-farming systems consist of integrated or conventional farms, and many antimicrobials are used to treat bacterial infections. The objective of this study was to compare characteristics of third-generation cephalosporin resistance and extended-spectrum β-lactamase (ESBL)/pAmpC β-lactamase-producing Escherichia coli between integrated and conventional farms.

METHODS

Third-generation cephalosporin-resistant E. coli was collected from integrated and conventional pig farms from 2021 to 2022. Polymerase chain reaction and DNA sequencing were performed for the detection of β-lactamase-encoding genes, molecular analysis, and identification of genetic relationships. To determine the transferability of β-lactamase genes, conjugation assays were conducted.

RESULTS

Antimicrobial resistance rates were higher in conventional farms than in integrated farms; ESBL- and pAmpC-lactamase-producing E. coli rates were higher in conventional farms (9.8%) than in integrated farms (3.4%). Fifty-two (6.5%) isolates produced ESBL/pAmpC β-lactamase genes. Isolates from integrated farms harboured CTX-15 (3 isolates), CTX-55 (9 isolates), CTX-229 (1 isolate), or CMY-2 (1 isolate) genes; isolates from conventional farms harboured CTX-1 (1 isolate), CTX-14 (6 isolates), CTX-15 (2 isolates), CTX-27 (3 isolates), CTX-55 (14 isolates), CTX-229 (1 isolate), and CMY-2 (11 isolates) genes. Of the 52 ESBL/pAmpC β-lactamase-producing E. coli isolates, class 1 integrons with 11 different gene cassette arrangements were detected in 39 (75.0%) isolates, and class 2 integrons were detected in 3 isolates. The most common sequence type in both integrated and conventional farms was ST5229, followed by ST101, and then ST10.

CONCLUSION

Third-generation cephalosporin-resistant patterns and molecular characteristics differed between integrated and conventional farms. Our findings suggest that continuous monitoring of third-generation cephalosporin resistance on pig farms is necessary to prevent the dissemination of resistant isolates.

Detection of blaCTX-M and blaDHA genes in stool samples of healthy people: comparison of culture- and shotgun metagenomic-based approaches

We implemented culture- and shotgun metagenomic sequencing (SMS)-based methods to assess the gut colonization with extended-spectrum cephalosporin-resistant Enterobacterales (ESC-R-Ent) in 42 volunteers. Both methods were performed using native and pre-enriched (broth supplemented with cefuroxime) stools. Native culture screening on CHROMID® ESBL plates resulted in 17 positive samples, whereas the pre-enriched culture (gold-standard) identified 23 carriers. Overall, 26 ESC-R-Ent strains (24 Escherichia coli) were identified: 25 CTX-M and 3 DHA-1 producers (2 co-producing CTX-Ms). Using the SMS on native stool ("native SMS") with thresholds ≥60% for both identity and coverage, only 7 of the 23 pre-enriched culture-positive samples resulted positive for blaCTX-M/blaDHA genes (native SMS reads mapping to blaCTX-M/blaDHAs identified in gold-standard: sensitivity, 59.0%; specificity 100%). Moreover, an average of 31.5 and 24.6 antimicrobial resistance genes (ARGs) were detected in the 23 pre-enriched culture-positive and the 19 negative samples, respectively. When the pre-enriched SMS was implemented, more blaCTX-M/blaDHA genes were detected than in the native assay, including in stools that were pre-enriched culture-negative (pre-enriched SMS reads mapping to blaCTX-M/blaDHAs identified in gold-standard: sensitivity, 78.3%; specificity 75.0%). In addition, the pre-enriched SMS identified on average 38.6 ARGs/sample, whereas for the corresponding native SMS it was 29.4 ARGs/sample. Notably, stools resulting false-negative by using the native SMS had lower concentrations of ESC-R-Ent (average: ~105 vs. ~107 CFU/g) and E. coli classified reads (average: 193,959 vs. 1.45 million) than those of native SMS positive samples. Finally, the detection of blaCTX-M/blaDHA genes was compared with two well-established bioinformatic tools. In conclusion, only the pre-enriched SMS assured detection of most carriers of ESC-R-Ent. However, its performance was not comparable to the pre-enriched culture-based approach.

Escherichia ruysiae May Serve as a Reservoir of Antibiotic Resistance Genes across Multiple Settings and Regions

Gut colonization with multidrug-resistant Enterobacterales (MDR-Ent) has reached worrisome levels worldwide. In this context, Escherichia ruysiae is a recently described species mostly found in animals. However, its spread and impact on humans is poorly understood. A stool sample from a healthy individual living in India was screened for the presence of MDR-Ent using culture-based methods. Colonies were routinely identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and phenotypically characterized by broth microdilution. Illumina and Nanopore whole-genome sequencing (WGS) platforms were implemented to generate a complete assembly. E. ruysiae genomes deposited in international databases were used for a core genome phylogenetic analysis. An extended-spectrum β-lactamase (ESBL)-producing E. coli strain (S1-IND-07-A) was isolated from the stool. WGS confirmed that S1-IND-07-A was indeed E. ruysiae, belonged to sequence type 5792 (ST5792), core genome (cg) ST89059, serotype O13/O129-:H56-like, clade IV phylogroup, and possessed five virulence factors. A copy of blaCTX-M-15 and five other antimicrobial resistance genes (ARGs) were detected in a conjugative IncB/O/K/Z plasmid. A database search identified 70 further E. ruysiae strains from 16 countries (44, 15, and 11 strains isolated from animals, the environment, and humans, respectively). The core genome phylogeny revealed five major STs: ST6467, ST8084, ST2371, ST9287, and ST5792. Three out of the seventy strains possessed important ARGs: OTP1704 (blaCTX-M-14; ST6467), SN1013-18 (blaCTX-M-15; ST5792), and CE1758 (blaCMY-2; ST7531). These strains were of human, environmental, and wild animal origin, respectively. E. ruysiae may acquire clinically important ARGs and transmit them to other species. Due to its zoonotic potential, further efforts are needed to improve routine detection and surveillance across One Health settings. IMPORTANCE Escherichia ruysiae is a recently described species of the cryptic clades III and IV of the genus Escherichia and is commonly found in animals and the environment. This work highlights the zoonotic potential of E. ruysiae, as it has been shown to colonize the human intestinal tract. Importantly, E. ruysiae may be associated with conjugative plasmids carrying clinically relevant antibiotic resistance genes. Therefore, it is important to closely monitor this species. Overall, this study highlights the need for improved identification of Escherichia species and continued surveillance of zoonotic pathogens in One Health settings.

Comparative Genetic Characterization of CTX-M-Producing Escherichia coli Isolated from Humans and Pigs with Diarrhea in Korea Using Next-Generation Sequencing

Pathogenic E. coli causes intra- and extraintestinal diseases in humans and pigs and third-generation cephalosporins are the primary option for the treatment of these diseases. The objective of this study was to investigate the characteristics and correlation between CTX-M-producing E. coli from humans and pigs regarding CTX-M-producing E. coli using next-generation sequencing and bioinformatic tools. Among the 24 CTX-M-producing E. coli, three types of CTX-M genes (CTX-M-12, CTX-M-14, and CTX-M-15) were detected in humans and four types of CTX-M genes (CTX-M-14, CTX-M-15, CTX-M-55, and CTX-M-101) were detected in pigs. A total of 24 CTX-M-producing E. coli isolates also showed the following antimicrobial resistance genes: other B-Lactam resistance gene (75.0%); aminoglycoside resistance genes (75.0%); phenicol resistance genes (70.8%); tetracycline resistance genes (70.8%); sulfonamide resistance genes (66.7%); quinolone resistance genes (62.5%); trimethoprim resistance genes (54.2%); and fosfomycin resistance genes (8.3%). FII (92.3%) and FIB (90.9%) were the most common plasmid replicon in humans and pigs, respectively. A total of thirty-eight different genes associated with virulence 24 CTX-M-producing E. coli and all isolates contained at least more than one virulence gene. A total of 24 CTX-M-producing E. coli isolates showed 15 diverse sequence types (STs): thirteen isolates from human belonged to 6 different STs, and 11 isolates from pig belonged to 9 different STs. The presence of virulence genes in E. coli together with antimicrobial resistance genes (including CTX-M genes) emphasizes the necessity of comprehensive surveillance and persistent monitoring of the food chain to avoid all types of bacterial contamination, regardless of human or pig origin.

Prevalence and Risk Factors Associated with Multidrug Resistance and Extended-Spectrum β-lactamase Producing E. coli Isolated from Healthy and Diseased Cats

Household cats have been identified as potential antimicrobial resistance (AMR) reservoirs, and the extended-spectrum β-lactamases (ESBL) producing E. coli circulating among cats has been more frequently reported globally, but the factors linked to its colonization remain poorly understood. Thus, the objectives of this study were to determine E. coli shedding and the occurrence of multidrug resistant (MDR)- and ESBL-producing E. coli, as well as to determine risk factors associated with colonization of MDR and ESBL-producing E. coli isolated from both healthy and diseased cats in the Eastern Province of Saudi Arabia. In a cross-sectional study, 2000 swabs were collected from five anatomical regions (anus, skin, ear canal, nares, and conjunctival sac) of 209 healthy and 191 diseased cats that were admitted to a veterinary clinic in the Eastern Province of Saudi Arabia. In addition, each cat owner filled out a questionnaire about their cat's demographics, management, health status, and antimicrobial usage. E. coli was detected in 165 (41.3%) of all cats, including 59 (28.2%) healthy and 106 (55.5%) diseased cats. In total, 170 E. coli isolates were found in healthy (35.3%) and diseased (64.7%) cats. Susceptibility testing revealed that 123 (72.4%) of the E. coli isolates were resistant to at least one of the tested antimicrobials. Overall, 17.6% (30/170) of E. coli isolates were MDR, with 10 (5.9%) and 20 (11.8%) isolates found in healthy and diseased cats, respectively. However, only 12 (7.1%) E. coli isolates were resistant to cefotaxime and harbored the bla_CTX-M gene (ESBL-producer), with seven (4.1%) in healthy and five (2.9%) in diseased cats. Risk factor analysis showed that the odds of MDR and ESBL-producing E. coli were (20 and 17) and (six and eight) times higher when the family and cats were previously treated with antimicrobials, respectively. The presence of a child in the cat's family was also linked to an increased risk of MDR E. coli colonization (OR = 3.4). In conclusion, a high frequency of MDR and ESBL-producing E. coli was detected among healthy and diseased cats in Saudi Arabia, raising concerns about transmission to humans and supporting the need of a "One Health" approach to address the potential threats of cats as AMR reservoirs.

Genetic characterization of third- or fourth-generation cephalosporin-resistant avian pathogenic Escherichia coli isolated from broilers

The third- or fourth-generation cephalosporins (3GC or 4 GC) are classified as "critically important antimicrobials for human medicine" by WHO, but resistance to these drugs is increasing rapidly in avian pathogenic E. coli (APEC). This study investigated the distribution and genetic characteristics of 3GC- or 4 GC-resistant APEC isolates from five major integrated broiler operations in Korea. The prevalence of 3GC- or 4GC-resistant APEC isolates in 1-week-old broilers was the highest in farms of operation C (53.3%); however, the highest prevalence of these isolates in 4-week-old broilers was the highest on the farms of operation A (60.0%), followed by operations E (50.0%) and C (35.7%). All 49 3GC- or 4GC-resistant APEC isolates had at least one β-lactamase-encoding gene. The most common β-lactamase-encoding genes was extended-spectrum β-lactamase gene, bla _CTX-M-15, detected in 24 isolates (49.0%), followed by bla _TEM-1 (32.7%). Sixteen isolates (32.7%) harbored class 1 integrons, and four isolates (8.2%) showed different gene cassette-arrangements. However, only 1 of 26 isolates harboring class 2 integrons carried a gene cassette. Furthermore, both CRISPR 1 and 2 arrays were detected in most isolates (36 isolates; 73.5%), followed by CRISPR 2 (18.4%) and CRISPR 1 (4.1%). Interestingly, CRISPR 2 was significantly more prevalent in multidrug resistant (MDR)-APEC isolates than in non-MDR APEC isolates, whereas CRISPR 3 and 4 were significantly more prevalent in non-MDR APEC isolates (each 11.1%; p < 0.05). None of the protospacers of CRISPR arrays were directly associated with antimicrobial resistance. Our findings indicate that the distribution and characteristics of 3GC or 4GC-resistant APEC isolates differed among the integrated broiler operations; moreover, improved management protocols are needed to control the horizontal transmission of 3GC or 4GC-resistant APEC isolates.

Extended-Spectrum Beta-Lactamases Producing Enterobacteriaceae in the USA Dairy Cattle Farms and Implications for Public Health

Antimicrobial resistance (AMR) is one of the top global health threats of the 21th century. Recent studies are increasingly reporting the rise in extended-spectrum beta-lactamases producing Enterobacteriaceae (ESBLs-Ent) in dairy cattle and humans in the USA. The causes of the increased prevalence of ESBLs-Ent infections in humans and commensal ESBLs-Ent in dairy cattle farms are mostly unknown. However, the extensive use of beta-lactam antibiotics, especially third-generation cephalosporins (3GCs) in dairy farms and human health, can be implicated as a major driver for the rise in ESBLs-Ent. The rise in ESBLs-Ent, particularly ESBLs-Escherichia coli and ESBLs-Klebsiella species in the USA dairy cattle is not only an animal health issue but also a serious public health concern. The ESBLs-E. coli and -Klebsiella spp. can be transmitted to humans through direct contact with carrier animals or indirectly through the food chain or via the environment. The USA Centers for Disease Control and Prevention reports also showed continuous increase in community-associated human infections caused by ESBLs-Ent. Some studies attributed the elevated prevalence of ESBLs-Ent infections in humans to the frequent use of 3GCs in dairy farms. However, the status of ESBLs-Ent in dairy cattle and their contribution to human infections caused by ESBLs-producing enteric bacteria in the USA is the subject of further study. The aims of this review are to give in-depth insights into the status of ESBL-Ent in the USA dairy farms and its implication for public health and to highlight some critical research gaps that need to be addressed.

Prevalence of Multidrug-Resistant CTX-M Extended Spectrum Beta-Lactamase-Producing Escherichia coli From Different Bovine Faeces in China

CTX-M extended spectrum beta-lactamase-producing Escherichia coli cause severe health hazards in livestock breeding. To date, little is known about antibiotic resistance differences among bacterial isolates from yaks, cows, and beef cattle; therefore, the aims of this study were to analyse the prevalence of CTX-M-producing E. coli in yak, beef cattle, and dairy cattle feces from different provinces in China. A total of 790 fecal samples from yaks, beef cattle, and dairy cows were used. Among all the samples, 523 non duplicate E. coli isolates were identified, and 29.6% of samples harbored CTX-M producers. The results showed that these E. coli strains harbored 15 clusters of CTX-M genes: CTX-M-79, CTX-M-55, CTX-M-15, CTX-M-14, CTX-M-28, CTX-M-179, CTX-M-65, CTX-M-24, CTX-M-27, CTX-M-102, CTX-M-105, CTX-M-173, CTX-M-238, CTX-M-196, and CTX-M-10. The dominant resistance genes were CTX-M-15, CTX-M-14, and CTX-M-55. Moreover, the distribution of CTX-M genes was related to geographical region. Based on the above findings, we reasoned that bovines are potential reservoirs of antibiotic resistance, and this problem should be given adequate attention.

Molecular Characterization of Clinically Relevant Extended-Spectrum β-Lactamases blaCTX-M-15-Producing Enterobacteriaceae Isolated from Free-Range Chicken from Households in Bangladesh

The study explored the potential colonization and characterization of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in the gut of free-range poultry from the rural households in Bangladesh. From 48 households located in several rural regions (eastern, western, and southern) of Bangladesh, 180 poultry fecal samples were collected to isolate ESBL-producing Enterobacteriaceae. ESBL producers were characterized by susceptibility testing, conjugation experiment, conventional polymerase chain reactions (PCRs), and multilocus sequence typing (MLST) followed by sequencing. Total 23% (42/180) poultry were ESBL positive consisting of Escherichia coli (n = 41) and Klebsiella pneumoniae (n = 1). ESBL producers were resistant to Cefotaxime (CTX; 100%), Cefepime (100%), Amoxicillin-clavulanic acid (36%), Ciprofloxacin (31%), and Trimethoprim-sulfamethoxazole (24%), and 12% isolates were multidrug resistant. All ESBL producers were carrying bla_CTX-M-15-like genotype.Isolates were also carrying genes for quinolone resistance [qnrS1, aac(6')-Ib-cr], silver resistance (silE), and mercury resistance (merA). Isolates were negative for 025b-ST131 clone, mcr-1, and bla_OXA-48 gene. The repetitive element PCR revealed 15 different clones of E. coli and some of these clones were found to be common in 3 sampling locations. MLST analysis of E. coli revealed 9 different sequence types (STs); ST4, ST156, ST542, ST1140, ST1290, ST4628, ST5114, ST9768, and ST11317. ESBL producers were carrying transferable plasmids and 4 different plasmid replicon types; IncI1 (29%), IncY (7%), IncFIB (7%), and IncF1A (5%). The findings from the study confirmed that free-range poultry are potential ESBL carriers with coresistance to other antibiotic classes, metals, and biocides. This study confirms that free-range poultry in Bangladesh living close to humans without any direct antibiotic exposure could carry ESBL bacteria. Free-range poultry could be reservoir as well as a potential spreader of pathogenic E. coli and antibiotic- or biocide-resistant genes.

Occurrence and characterization of genetic determinants of β-lactam-resistance in Escherichia coli clinical isolates

β-lactamase mediated resistance in Escherichia coli is a significant problem that requires immediate attention. Herein, we aim to characterize and understand the dynamics of the genetic determinants of β-lactam resistance (i.e. ESBL, AmpC, and MBL) in E. coli. Out of 203 E. coli isolates, genetic determinants of β-lactam resistance were identified in 50% (n = 101) of isolates. ESBL, AmpC, and MBL resistance determinants were detected in 78%, 40%, and 18% of isolates, respectively with bla_{CTX-M group 4} (48%), bla_CMY (40%), and bla_SIM (33%) as the most prevalent β-lactam resistance genes. Among these isolates, 45% harbored plasmid replicon types, with L/M (40%) and Y (33%) as the most dominant replicon types. Integrons were detected in 40% of such isolates, with Class-1 and Class-3 representing 62% and 55%, respectively. Overall, we observed high rate of genetic determinants of β-lactam-resistance in E. coli isolates recovered from patients in clinical settings. The co-occurrence of antimicrobial resistance genes and mobile genetic elements in a high percentage of isolates is a major concern and relates to complex resistance mechanisms. To combat the serious threat of antimicrobial resistance, it is imperative to develop strategies for robust surveillance and understand the molecular basis of resistance acquisition and transmission.

Genetic Diversity, Biofilm Formation, and Antibiotic Resistance of Pseudomonas aeruginosa Isolated from Cow, Camel, and Mare with Clinical Endometritis

Pseudomonas aeruginosa is a ubiquitous opportunistic bacterium that causes diseases in animals and humans. This study aimed to investigate the genetic diversity, antimicrobial resistance, biofilm formation, and virulence and antibiotic resistance genes of P. aeruginosa isolated from the uterus of cow, camel, and mare with clinical endometritis and their drinking water. Among the 180 uterine swabs and 90 drinking water samples analysed, 54 (20%) P. aeruginosa isolates were recovered. Isolates were identified biochemically to the genus level by the automated Vitek 2 system and genetically by the amplification of the gyrB gene and the sequencing of the 16S rRNA gene. Multilocus sequence typing identified ten different sequence types for the P. aeruginosa isolates. The identification of ST2012 was significantly (p ≤ 0.05) higher than that of ST296, ST308, ST111, and ST241. The isolates exhibited significantly (p ≤ 0.05) increased resistance to piperacillin (77.8%), ciprofloxacin (59.3%), gentamicin (50%), and ceftazidime (38.9%). Eight (14.8%) isolates showed resistance to imipenem; however, none of the isolates showed resistance to colistin. Multidrug resistance (MDR) was observed in 24 isolates (44.4%) with a multiple antibiotic resistance index ranging from 0.44 to 0.77. MDR was identified in 30 (33.3%) isolates. Furthermore, 38.8% and 9.2% of the isolates exhibited a positive extended-spectrum-β-lactamase (ESBL) and metallo-β-lactamase (MBL) phenotype, respectively. The most prevalent β-lactamase encoding genes were bla_TEM and bla_CTX-M, however, the bla_IPM gene was not detected in any of the isolates. Biofilm formation was observed in 49 (90.7%) isolates classified as: 11.1% weak biofilm producers; 38.9% moderate biofilm producers; 40.7% strong biofilm producers. A positive correlation was observed between the MAR index and biofilm formation. In conclusion, the results highlighted that farm animals with clinical endometritis could act as a reservoir for MDR and virulent P. aeruginosa. The emergence of ESBLs and MBLs producing P. aeruginosa in different farm animals is a public health concern. Therefore, surveillance programs to monitor and control MDR P. aeruginosa in animals are required.

Transferability of ESBL-encoding IncN and IncI1 plasmids among field strains of different Salmonella serovars and Escherichia coli

OBJECTIVES

This study aimed to sequence, assemble and annotate three plasmids (two IncN and one IncI1) carrying the bla_CTX-M-1 gene and assess their transmissibility rates between homologous and heterologous serovars and/or species of bacteria.

METHODS

First, the plasmids were sequenced, assembled, and annotated. They were then transferred from three donor strains (E. coli/IncN, S. Heidelberg/IncN, and S. Heidelberg/IncI1) into nine recipient strains (S. Enteritidis, S. Heidelberg, S. Saint Paul, S. Cero, S. Infantis, S. Braenderup, E. coli 50, and E. coli 2010). The bla_CTX-M-1 gene PCR, plasmid isolation, and antimicrobial susceptibility testing were used on the transconjugants to confirm the successful transfer of ESBL plasmids into the recipient strains.

RESULTS

Both IncN plasmids were 42,407 bp in size and showed >99.4% similarity to the S. Bredeney pET1.2-IncN (GenBank accession CP043224.1) whereas the IncI1 plasmid was 107,635 bp in size and demonstrated >99.9% similarity to the E. coli pCOV33 plasmid (GenBank accession MG649046.1). Successful plasmid transfer was observed between donor ​E. coli (IncN) and all recipient strains except for E. coli 50 and between donor S. Heidelberg (IncN) and all recipient strains. Successful plasmid transfer was also observed between S. Heidelberg (IncI1) and E. coli 50.

CONCLUSIONS

Transfer of the bla _CTX-M-1 encoding IncN and IncI1 plasmids via conjugation is possible yet occurs at different frequencies depending on the donor strain of bacteria with S. Heidelberg (IncN) having the highest donor-dependent transfer frequency, followed by E. coli 9079 (IncN) and S. Heidelberg (IncI1).

Comparative analysis of antimicrobial resistance and genetic characteristics of Escherichia coli from broiler breeder farms in Korea

Broiler breeder farms could be a reservoir of Escherichia coli, disseminating antimicrobial resistance and virulence factors. We investigated the antimicrobial resistance of E. coli from nine broiler breeder farms and characterised their resistance and virulence genes. A total of 256 E. coli showed a high level of resistance to tetracycline, nalidixic acid, ampicillin, and cephalothin, followed by trimethoprim-sulfamethoxazole and chloramphenicol. The resistance to nalidixic acid, ampicillin, trimethoprim–sulfamethoxazole, and chloramphenicol showed significant differences among the farms. Among 202 β-lactam-resistant E. coli, 138 carried β-lactamase genes. The most prevalent β-lactamase gene was blaTEM-1, of which the presence differed significantly across the farms. Out of 197 tetracycline-resistant E. coli isolates, tetA and tetB were detected in 164 and 50, with significant differences among the farms. Also, 45 of 196 nalidixic acid-resistant E. coli carried qnrS while 67 of 149 trimethoprim–sulfamethoxazole-resistant E. coli carried sul2. Among the five virulence genes tested, ompT was the most prevalent, and all genes except for iutA distributed significantly different among the farms. The phenotypic and genotypic characteristics of E. coli were significantly different among the farms; therefore, management at the breeder level is required to control the vertical transmission of E. coli.

Abundance of colistin-resistant Escherichia coli harbouring mcr-1 and extended-spectrum β-lactamase-producing E. coli co-harbouring blaCTX-M-55 or -65 with blaTEM isolates from chicken meat in Vietnam

Although the spread of plasmid-mediated antibiotic-resistant bacteria is a public health concern, food contamination with plasmid-mediated antibiotic-resistant Escherichia coli in Vietnam has not been well investigated. This study aimed to describe the prevalence of colistin-resistant, carbapenem-resistant, and endemic bla_CTX-M in extended-spectrum β-lactamase (ESBL) producing E. coli isolates. Colistin and carbapenem-resistant ESBL-producing E. coli were isolated from chickens in Vietnam and Japan. Colistin-resistant and AmpC/ESBL-producing E. coli (52% and 93%, respectively) were detected in chickens from Vietnam, in comparison to 52.7%, AmpC/ESBL-producing E. coli found in chicken from Japan. Carbapenem-resistant E. coli has not been isolated in Vietnam and Japan. Genotyping revealed that colistin-resistant E. coli harboured mcr-1, and most of the AmpC/ESBL-related genes were bla_CTX-M-55 and bla_CTX-M-65 together with bla_TEM in Vietnamese chickens and bla_CMY-2 in Japanese chickens. Multi-drug resistance analysis showed that ESBL-producing E. coli isolates had greater resistance to quinolones, streptomycin, and chloramphenicol than colistin-resistant E. coli isolates from Vietnam, suggesting the selection of multiple antibiotic resistance genes in ESBL-producing E. coli. In conclusion, colistin-resistant E. coli was detected in approximately half of the chicken samples, the majority of which harboured mcr-1. The high prevalence of ESBL-producing E. coli has remained constant in the last 5 years. The predominant bla_CTX-M in ESBL-producing E. coli was bla_CTX-M-55 or bla_CTX-M-65, with the coexistence of bla_TEM in Vietnam. These results can be implemented in monitoring systems to overcome the development of antimicrobial resistance.

Comparison of antimicrobial resistance and molecular characterization of Escherichia coli isolates from layer breeder farms in Korea

In Korea, 4 big layer companies that possess one grandparent and 3 parent stocks are in charge of 100% of the layer chicken industry. In this study, we investigated the antimicrobial resistance of commensal 578 E. coli isolated from 20 flocks of 4-layer breeder farms (A, B, C, and D), moreover, compared the characteristics of their resistance and virulence genes. Isolates from farms B and D showed significantly higher resistance to the β-lactam antimicrobials (amoxicillin, ampicillin, and 1st-, 2nd-, and 3rd-generation cephalosporins). However, resistance to ciprofloxacin, nalidixic acid, and tetracycline was significantly higher in the isolates from farm A (P < 0.05). Interestingly, the isolates from farm C showed significantly lower resistance to most antimicrobials tested in this study. The isolates from farms B, C, and D showed the high multiple resistance to the 3 antimicrobial classes. Furthermore, the isolates from farm A showed the highest multiple resistance against the 5 classes. Among the 412 β-lactam-resistant isolates, 123 (29.9%) carried bla_TEM-1, but the distribution was significantly different among the farms from 17.5% to 51.4% (P < 0.05). Similarly, the most prevalent tetracycline resistance gene in the isolates from farms B, C, and D was tetA (50.0–77.0%); however, the isolates from farm A showed the highest prevalence in tetB (70.6%). The distribution of quinolone (qnrB, qnrD, and qnrS) and sulfonamide (su12)-resistant genes were also significantly different among the farms but that of chloramphenicol (catA1)- and aminoglycoside (aac [3]-II, and aac [6′]-Ib)-resistant genes possessed no significant difference among the farms. Moreover, the isolates from farm C showed significantly higher prevalence in virulence genes (iroN, ompT, hlyF, and iss) than the other 3 farms (P < 0.05). Furthermore, the phenotypic and genotypic characteristics of E. coli isolates were significantly different among the farms, and improved management protocols are required to control of horizontal and vertical transmission of avian disease, including the dissemination of resistant bacteria in breeder flocks.

Prevalence of Methicillin-Resistant Staphylococcus Species Among Filarial Lymphedema Patients in Ahanta West District of Ghana

Background

Filarial pathologies such as lymphedema may be associated with complications such as chronic non-healing wounds. Nonetheless, the role of bacterial population colonizing the lymphedematous legs has been posited to worsen the conditions of those living with the infection. These bacteria are usually composed of staphylococcal species partly because they are commensals. Thus, this present study sought to type the methicillin-resistant Staphylococcus aureus (MRSA) prevalence among individuals presenting with filarial lymphedema, particularly as MRSA tends to affect treatments options.

Methods

We recruited individuals (n = 321) with stages I–VII of lymphedema in a cross-sectional study in the Ahanta West district of the Western Region of Ghana. Swabs from lymphedematous limb ulcers, pus, and cutaneous surfaces were cultured using standard culture-based techniques. The culture isolates were later identified using Matrix-assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) mass spectrometry.

Results

A total of 192 Staphylococci species were isolated, with an overall prevalence of 39.7% (95% CI: 35%–44%; N = 483). S. hominis was the most prevalent species (23.95%), followed by S. haemolyticus (20.83%), S. epidermidis (15.10%), S. aureus (10.41%), and S. saprophyticus (9.32%). The remaining 20.34% were distributed among S. wanneri, S. sciuri, S. pasteuri, S. xylosus, S. simulans, S. cohnii, S. caprae, S. lugdunensis, and S. capitis. MRSA, containing mecA gene, was detected in 21 out of 31 Staphylococci isolates tested, with an overall prevalence of 68% (95% CI: 51%–84%). In addition, a virulent gene, Panton–Valentine leukocidin (PVL), which is usually associated with S. aureus, was detected in 20/31 (64.5%) S. aureus in the study.

Conclusion

These results suggest that MRSA species may pose a challenge to the treatment of filarial lymphedema with antibiotics particularly, as doxycycline is currently being piloted in some endemic areas to treat the infection. Thus, intensive antimicrobial resistance surveillance should be conducted in endemic areas by health authorities to forestall the dilemma of multidrug resistance not only against lymphatic filariasis (LF) infection but other diseases.

Molecular Characterization of Antibiotic Resistance Associated with TEM and CTX-M ESBL in Uropathogenic E. coli Strains Isolated from Outpatients

Background & Objective

Escherichia coli (E. coli) is a leading cause of urinary tract infections becoming resistant against beta-lactams and cephalosporins through different mechanisms, including ESBL production due to the presence of ESBL specific genes, including blaCTX-M and blaTEM. The purpose of the present study was to detect the uropathogenic E. coli strains producing the ESBL.

Methods

A total of 100 isolates of uropathogenic E. coli were randomly selected in a period of 6 months and their resistances to a number of antibiotics including amoxicillin, amikacin, gentamicin, ciprofloxacin, ceftazidime, cefotaxime, ceftriaxone, ceftizoxime, nalidixic acid, and nitrofurantoin were determined. Then, DDT test was used to detect the presence of ESBL. Finally, the presence of blaCTX-M and blaTEM resistance genes was analyzed by PCR method.

Results

The resistance profile of bacterial isolates to the antibiotics was as follows: amoxicillin: 16.7%, amikacin: 7.8%, gentamicin: 20.3%, ciprofloxacin: 35.5/%, ceftazidime: 35.0%, cefotaxime: 40.0%, ceftriaxone: 41.3%, nalidixic acid: 64.0%, nitrofurantoin: 9.7%, and ceftizoxime: 100%. Of these, 28 isolates (28%) were reported to be resistant to cefotaxime, ceftazidime, and ceftriaxone. In DDT test, 21 ESBL positive cases (21%) were detected. PCR results showed that the presence of blaCTX-M and blaTEM genes in the isolates were 21% and 20%, respectively.

Conclusion

Regarding the production of ESBL by some E. coli isolates, phenotypic detection of ESBL-producing isolates is routinely suggested in the laboratories. Likewise, the treatment regimen should be selected regarding the ESBL production to avoid treatment failure.

Comparative analysis of genetic characterization of β-lactam-resistant Escherichia coli from bulk tank milk in Korea

BACKGROUND

This study was conducted to analyze the genetic characteristics of 41 β-lactam-resistant Escherichia coli isolates, which are one of the common causes of environmental mastitis, isolated from the bulk tank milk of 290 dairy farms in five factories operated by three dairy companies in Korea.

RESULTS

Analysis of the phenotypic and genotypic characteristics of β-lactam-resistant E. coli isolates revealed differences between factories even within the same company. Isolates from factory A1 and C1 showed high resistance to cephalothin (76.9 and 100%, respectively), which is a first-generation cephalosporins, whereas resistance to tetracycline was showed by only the isolates from factories B1 (60.0%), C2 (66.7%), and C3 (100%). Although all the 41 β-lactam-resistant E. coli isolates were positive for blaOXA-1, blaTEM-1 was highly prevalent in isolates from factories C2 (100%) and C3 (100%). Among 17 isolates resistant to both β-lactams and aminoglycosides, the most common multilocus sequence type was ST399 (13isolates, 76.5%). Furthermore, 2 (11.8%) and 12 (70.6%) isolates belonged to the phylogenetic groups B2 and D, respectively, which are invasive strains that cause intestinal infections, respectively. The predominant serogroup was O15 (70.6%), which is a globally distributed extraintestinal pathogen. Interestingly, one isolate from factory A1 belonged to O157 and carried six virulence genes, simultaneously.

CONCLUSIONS

Although E. coli isolates were isolated from bulk tank milk, and not the clinical mastitis samples, the presence of the phylogenetic groups B2 and D, and the serogroups O15 and O157, which harbor antimicrobial resistance genes and virulence factors, can pose a threat to public health.

Prevalence and antimicrobial resistance of Klebsiella species isolated from clinically ill companion animals

Background

Klebsiella spp. is an important conditional pathogen in humans and animals. However, due to the indiscriminate use of antibiotics, the incidence of antimicrobial resistance has increased.

Objectives

The purpose of this study was to investigate antimicrobial resistance in strains of Klebsiella strains and the phylogenetic relatedness of extended-spectrum cephalosporin (ESC)-resistance among Klebsiella strains isolated from clinically ill companion animals.

Methods

A total of 336 clinical specimens were collected from animal hospitals. Identification of Klebsiella species, determination of minimum inhibitory concentrations, detection of ESC resistance genes, polymerase chain reaction-based replicon typing of plasmids by conjugation, and multilocus sequence typing were performed.

Results

Forty-three Klebsiella strains were isolated and, subsequently, 28 were identified as K. pneumoniae, 11 as K. oxytoca, and 4 as K. aerogenes. Eleven strains were isolated from feces, followed by 10 from ear, 7 from the nasal cavity, 6 from urine, 5 from genitals, and 4 from skin. Klebsiella isolates showed more than 40% resistance to penicillin, cephalosporin, fluoroquinolone, and aminoglycoside. ESCresistance genes, CTX-M groups (CTX-M-3, CTX-M-15, and CTX-M-65), and AmpC (CMY-2 and DHA-1) were most common in the K. pneumoniae strains. Some K. pneumoniae carrying CTX-M or AmpC were transferred via IncFII plasmids. Two sequence types, ST709 and ST307, from K. pneumoniae were most common.

Conclusions

In conclusion, this is the first report on the prevalence, ESCresistance genotypes, and sequence types of Klebsiella strains isolated from clinically ill companion animals. The combination of infectious diseases and antimicrobial resistance by Klebsiella in companion animals suggest that, in clinical veterinary, antibiotic selection should be made carefully and in conjunction with the disease diagnosis.

Effect of ciprofloxacin and in vitro gut conditions on biofilm of Escherichia coli isolated from clinical and environmental sources

AIM

This study aimed at characterizing the biofilm-forming ability of drug-resistant and sensitive Escherichia coli under in vitro gut conditions and in the presence of ciprofloxacin.

METHODS AND RESULTS

153 E. coli isolates comprising 80 from clinical and 73 from environment source were studied for their ability to form biofilm under control and in vitro simulated gut conditions. The integrity of preformed biofilm on exposure to ciprofloxacin was assessed. Expression of biofilm-associated genes was analysed using qPCR. A high degree of resistance was observed in clinical isolates with a concomitant prevalence of bla_TEM . Bile, pH and low temperature enabled the E. coli biofilm to resist the effect of ciprofloxacin. Clinical isolates of E. coli formed strong biofilms in in vitro gut conditions following exposure to high concentration of ciprofloxacin. The expression of biofilm genes varied between different gut conditions viz., presence of bile, pH and low temperature, included in this study.

CONCLUSIONS

This study demonstrates the importance of papC and csgA for maintaining the biofilm integrity upon antibiotic exposure. Escherichia coli form biofilm as a survival strategy to adapt to the conditions in their environment irrespective of their drug resistance status.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study provides an understanding of the effect of different parameters of the gut conditions during infection and the effect of antibiotic on survival and biofilm-forming ability of clinical and environmental E. coli isolates. It further suggests that bacteria resort to biofilm formation as one of the mechanisms to adjust to alterations in gut conditions and once the biofilm is formed, it requires high concentration of ciprofloxacin to eradicate it.

Evaluation of selective media in antimicrobial surveillance programs capturing broad-spectrum β-lactamase producing Escherichia coli from chickens at slaughter

Antimicrobial resistance surveillance targeting agricultural animals is practiced in many countries but does not often include media selective for cephalosporin resistance. Here, we compared the frequency of recovery of resistant Escherichia coli using selective and non-selective media from the cecal contents of 116 chickens collected by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). Third generation cephalosporin resistance was detected in 24 samples including 12, 10, and 2 on selective, non-selective, and both media, respectively. Isolates producing the CTX-M-1 ESBL were grown from 11 samples, 10 on selective medium only. Our results suggest that current surveillance approaches underestimate the true prevalence of resistance to critically important antimicrobials.

Genetic Characterization of CTX-M-2-Producing Klebsiella pneumoniae and Klebsiella oxytoca Associated With Bovine Mastitis in Japan

CTX-M-2-producing Klebsiella oxytoca (K. oxytoca) has not received much attention in animal husbandry compared with Klebsiella pneumoniae (K. pneumoniae), a major reservoir of extended-spectrum β-lactamase (ESBL) genes. Bacteriological examinations of 1,466 mastitic milk samples between October 2012 and December 2014 were conducted. Ninety-five K. pneumoniae isolates (total prevalence: 6.5%) and 81 K. oxytoca isolates (total prevalence: 5.5%) were obtained. Seventeen K. pneumoniae isolates obtained from 15 animals reared on 11 farms and 9 K. oxytoca isolates obtained from 9 animals reared on the same farm were phenotypically confirmed to be ESBL producers. All nine ESBL-producing K. oxytoca isolates were obtained from one farm between June and November 2013 and related to a significantly (p < 0.05) higher monthly prevalence of mild mastitis (in June, August, September, October, and November 2013). Pulsed-field gel electrophoresis (PFGE) patterns of ESBL-producing K. pneumoniae isolates were distinguished from each other by more than 6-band differences except for two isolates from two animals, whereas all nine K. oxytoca isolates showed an identical PFGE pattern. Transferability of the bla _CTX-M-2 gene was found in 14 K. pneumoniae and 9 K. oxytoca isolates by conjugation analysis. Of these isolates, the bla _CTX-M-2 gene was detected on plasmids belonging to the incompatibility (Inc) groups P and N derived from five K. pneumoniae and nine K. oxytoca isolates, respectively, although the plasmids from the remaining nine K. pneumoniae were untypeable. All the transconjugants exhibited elevated minimum inhibitory concentrations of ampicillin, cefotaxime, and ceftiofur compared with those in the wild-type, recipient strain. Restriction fragment length polymorphism analysis demonstrated that the IncN plasmids extracted from eight of nine transconjugants, which received resistance against β-lactams from K. oxytoca, showed an identical DraI digestion pattern. These results suggest that the CTX-M-2-producing K. oxytoca strain with the above-mentioned characteristics may have clonally spread within a farm, whereas the bla _CTX-M-2 gene in K. pneumoniae possibly disseminated among the farms through different plasmids. Thus, monitoring of ESBL genes, including the bla _CTX-M-2 gene, among causative agents of bacterial mastitis in cows can help to develop relevant treatments and control practices.

Comparative Characteristics and Zoonotic Potential of Avian Pathogenic Escherichia coli (APEC) Isolates from Chicken and Duck in South Korea

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, which is an economically important disease in the poultry industry worldwide. The present study investigated O-serogroups, phylogenetic groups, antimicrobial resistance, and the existence of virulence-associated genes (VAGs) and antimicrobial resistance genes in 125 APEC isolates between 2018 and 2019 in Korea. The phylogenetic group B2 isolates were confirmed for human-related sequence types (STs) through multi-locus sequence typing (MLST). O-serogroups O2 (12.5%) and O78 (10.3%) and phylogenetic group B1 (36.5%) and A (34.5%) were predominant in chicken and duck isolates, respectively. Out of 14 VAGs, iucD, iroN, hlyF, and iss were found significantly more in chicken isolates than duck isolates (p < 0.05). The resistance to ampicillin, ceftiofur, ceftriaxone, and gentamicin was higher in chicken isolates than duck isolates (p < 0.05). The multidrug resistance (MDR) rates of chicken and duck isolates were 77.1% and 65.5%, respectively. One isolate resistant to colistin (MIC 16 μg/mL) carried mcr-1. The B2-ST95 APEC isolates possessed more than 9 VAGs, and most of them were MDR (82.4%). This report is the first to compare the characteristics of APEC isolates from chickens and ducks in Korea and to demonstrate that B2-ST95 isolates circulating in Korea have zoonotic potential and pose a public health risk.

Migratory Wild Birds as a Potential Disseminator of Antimicrobial-Resistant Bacteria around Al-Asfar Lake, Eastern Saudi Arabia

Migratory wild birds acquire antimicrobial-resistant (AMR) bacteria from contaminated habitats and then act as reservoirs and potential spreaders of resistant elements through migration. However, the role of migratory wild birds as antimicrobial disseminators in the Arabian Peninsula desert, which represents a transit point for birds migrating all over Asia, Africa, and Europe not yet clear. Therefore, the present study objective was to determine antimicrobial-resistant bacteria in samples collected from migratory wild birds around Al-Asfar Lake, located in Al-Ahsa Oasis, Eastern Saudi Arabia, with a particular focus on Escherichia coli virulence and resistance genes. Cloacal swabs were collected from 210 migratory wild birds represent four species around Al-Asfar. E. coli, Staphylococcus, and Salmonella spp. have been recovered from 90 (42.9%), 37 (17.6%), and 5 (2.4%) birds, respectively. Out of them, 19 (14.4%) were a mixed infection. All samples were subjected to AMR phenotypic characterization, and results revealed (14-41%) and (16-54%) of E. coli and Staphylococcus spp. isolates were resistant to penicillins, sulfonamides, aminoglycoside, and tetracycline antibiotics. Multidrug-resistant (MDR) E. coli and Staphylococcus spp. were identified in 13 (14.4%) and 7 (18.9%) isolates, respectively. However, none of the Salmonella isolates were MDR. Of the 90 E. coli isolates, only 9 (10%) and 5 (5.6%) isolates showed the presence of eaeA and stx2 virulence-associated genes, respectively. However, both eaeA and stx2 genes were identified in four (4.4%) isolates. None of the E. coli isolates carried the hlyA and stx1 virulence-associated genes. The E. coli AMR associated genes bla_CTX-M, bla_TEM, bla_SHV, aac(3)-IV, qnrA, and tet(A) were identified in 7 (7.8%), 5 (5.6%), 1 (1.1%), 8 (8.9%), 4 (4.4%), and 6 (6.7%) isolates, respectively. While the mecA gene was not detected in any of the Staphylococcus spp. isolates. Regarding migratory wild bird species, bacterial recovery, mixed infection, MDR, and AMR index were relatively higher in aquatic-associated species. Overall, the results showed that migratory wild birds around Al-Asfar Lake could act as a reservoir for AMR bacteria enabling them to have a potential role in maintaining, developing, and disseminating AMR bacteria. Furthermore, results highlight the importance of considering migratory wild birds when studying the ecology of AMR.

Bloodstream Infections Caused by Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Patients with Liver Cirrhosis

Background: This study aimed to investigate the frequency of sequence type (ST) 131 strains and outcome of cirrhotic patients with bloodstream infections (BSIs) caused by extended-spectrum beta-lactamase-producing Escherichiacoli (ESBLEC) and non-extended-spectrum beta-lactamase-producing Escherichiacoli (NESBLEC). Methods: The incidence of ST 131 strains, hospital stay, and 30-day re-admission/mortality were compared between 51 ESBLEC and 51 NESBLEC bacteremic patients with cirrhosis. Results: ST 131 strains were found in 35.3% of the ESBLEC group and 0% of the NESBLEC group (p < 0.001). Mean hospital stay was 26.5 days in the ESBLEC group and 17.1 days in the NESBLEC group (p = 0.006). Thirty-day re-admission rates were 11.8% in the ESBLEC group and 5.9% in the NESBLEC group (p = 0.5). ST 131 strains were associated with 30-day re-admission (odds ratio: 4.5, 95% confidence interval: 1.1–18.9). Thirty-day mortality rate was 31.4% in the ESBLEC group and 23.5% in the NESBLEC group (p = 0.4). Conclusion: In patients with cirrhosis, the ESBLEC BSIs group had a higher frequency of ST 131 strains and longer hospital stay than the NESBLEC BSIs group with similar 30-day re-admission/mortality. ST 131 strains were associated with 30-day re-admission.

High frequency of simultaneous presence of ESBL and carbapenemase producers among nosocomial coliform isolates in Faisalabad, Pakistan

Objectives:

The objective of the current study was to find prevalence of relevant ESBL and carbapenemase producing genes in nosocomial E. coli and K. pneumoniae isolates and to check phenotypic susceptibility of all ESBL positive isolates to carbapenems.

Methods:

Forty ESBL producing clinical isolates of Escherichia coli (n=33) and Klebsiella pneumoniae (n=7) were examined for the presence of β-lactamase genes (CTX-M, CTX-M-1, 2, 3, 4 and TEM). Carbapenem resistance was checked phenotypically and by presence of blaNDM-1 gene.

Results:

Nine (27%) were positive for CTX-M genes, and 10 (30%) for TEM among E. coli isolates. Importantly, six isolates showed co-existence of CTX-M and TEM genes. In K. pneumoniae, two (28%) isolates were positive for CTX-M and one (14%) for TEM genes. Eight (24%) E. coli and one (14%) K. pneumoniae isolates were positive for CTX-M-1. Respective figures for CTX-M-4 were three (10%) and one (14%). CTX-M-2 and CTX-M-3 groups were not represented. Twenty (50%) isolates were resistant to both imipenem and meropenem out of which only four isolates expressed blaNDM-1 gene.

Conclusions:

The significant presence of both ESBL and carbapenemase producers and co-existence of ESBL and carbapenemases in the same isolates is worrisome.

Wound dressing of chitosan-based-crosslinked gelatin/ polyvinyl pyrrolidone embedded silver nanoparticles, for targeting multidrug resistance microbes

Wound dressing composed of chitosan, based crosslinked gelatin/ polyvinyl pyrrolidone, embedded silver nanoparticles were fabricated using solution casting method. The membrane was characterized by FTIR, SEM and TGA. Glutaraldehyde (0.5 %) was used for the crosslinking of membrane components and associated with 7-folds boosted mechanical performance, 28 % more hydrolytic stability, 3-folds thickness reduction and morphological roughness. Silver nanoparticles were characterized by UV-vis, XRD and TEM for an average size of 9.9 nm. The membrane with higher concentration of silver nanoparticles showed maximum antibacterial activity against human pathogenic bacteria; and the measured inhibition zones ranged from 1.5 to 3 cm. The activity of the particles ranged from severe to complete reduction in Penicillin, Erythromycin and Macrolide family's resistance genes expression such as β-Lactamase, mecA and erm. This developed membrane can serve as promising and cost-effective system against severe diabetic and burn wound infections.

The occurrence of CTX-M-producing E. coli in the broiler parent stock in Korea

A large number of antimicrobials are used for the treatment of bacterial infections, and the emergence of antimicrobial-resistant Escherichia coli (E. coli) in livestock and the transfer of resistant isolates to humans poses a serious potential risk to public health. In particular, broiler parent stock produce thousands of eggs for commercial broiler chickens and can transfer antimicrobial-resistant bacteria and drug-resistance genes to chicks. This study was conducted to investigate the prevalence and characteristics of third-generation cephalosporin-resistant and extended-spectrum β-lactamases (ESBL)-producing E. coli isolated from the broiler parent stock in Korea. Among 51 cefotaxime-resistant E. coli isolates, 45 (88.2%) isolates were identified as multidrug resistant and 21 isolates showed phenotypic and genotypic characteristics of CTX-M-producing E. coli. The CTX-M genes CTX-M-14, CTX-M-15, CTX-M-1, and CTX-M-1 were detected in 10, 7, 3, and 1 isolates, respectively. ISEcp1 or IS26 + ISEcp1 were identified upstream of all CTX-M-type genes, and orf477 and IS903 were detected downstream of 9 and 10 CTX-M-type genes, respectively. Thirteen (61.9%) of the 21 CTX-M-producing E. coli isolates harbored class 1 integrons with 4 different gene cassette arrangements. Among the plasmid replicons, CTX-M-1 was located on I1, F, and FIB; CTX-M-14 on F and FII; CTX-M-15 on FII, FIA, and FIB; and CTX-M-65 on FIB. This is the first study to investigate the presence and distribution of third-generation cephalosporin-resistant and CTX-M-producing E. coli isolated from the broiler parent stock level in Korea, and the results indicate that comprehensive surveillance and persistent monitoring systems in broiler parent stock farms are necessary to prevent the dissemination of resistant isolates.

Evaluation of Two Methods for the Detection of Third Generation Cephalosporins Resistant Enterobacterales Directly From Positive Blood Cultures

Due to the importance of a rapid determination of patients infected by multidrug resistant bacteria, we evaluated two rapid diagnostic tests for the detection of third-generation cephalosporins (3GC)-resistant Enterobacterales directly from positive blood cultures within 1 h: BL-RED^TM (electrochemical method) and β-LACTA^TM test (chromogenic method). A panel of 150 clinical strains characterized for their resistance profiles (e.g., penicillinases, extended-spectrum beta-lactamases (ESBLs), overproduction of cephalosporinase, carbapenemases, impermeability) was tested. Approximately 100 CFU of each isolate was spiked into sterile blood culture bottles and incubated in a BD BACTEC^TM FX automated system (Becton Dickinson, USA). Positive blood cultures were examined to parallel testing using the BL-RED^TM and β-LACTA^TM tests and conventional susceptibility method (disc diffusion following EUCAST recommendations). For all phenotypes combined, the sensitivity, specificity, positive predictive value, and negative predictive value in the detection of 3GC resistance were, respectively (i) with BL-RED^TM: 45.7, 100, 100, and 54.2% and (ii) with β-LACTA^TM test: 52.2, 100, 100, and 56.9%. The positivity of tests allows to adapt antibiotic treatment whereas the negative result requires other tests. Moreover, these tests detect most Ambler class A-producing Enterobacterales (KPC, ESBL, extended-spectrum OXY) with sensitivities and specificities of 87.5 and 99% for BL-RED^TM, respectively and both 100% for β-LACTA^TM test (47/47 isolates). These two rapid tests failed to detect AmpC overexpressed (sensitivities of 2.7% for BL-RED^TM and 0% for β-LACTA^TM test) and Ambler class B-producing Enterobacterales (sensitivities of 40% for both tests) notably strains without ESBLs associated (sensitivities of 0% for both tests). BL-RED^TM and β-LACTA^TM tests are easy-to-use and mainly attractive when a positive result is obtained notably to detect most of the Ambler class A-producing Enterobacterales in <1 h after the positivity of the blood culture, allowing a rapid adaptation of the antibiotic therapy in patients.

Prevalence and Characterization of Plasmid-Mediated Quinolone Resistance Determinants qnr and aac(6')-Ib-cr in Ciprofloxacin-Resistant Escherichia coli Isolates from Commercial Layer in Korea

The prevalence and characterization of plasmid-mediated quinolone resistance (PMQR) determinants in ciprofloxacin-resistant Escherichia coli isolated from a Korean commercial layer farm were studied. A total of 45 ciprofloxacin-resistant E. coli isolates were recovered and all isolates were multidrug-resistant. Eight isolates have the PMQR genes aac(6')-Ib-cr, qnrS1, and qnrB4, and seven isolates exhibited double amino acid exchange at both gyrA and parC, and have high fluoroquinolone minimum inhibitory concentrations. Five transconjugants demonstrated transferability of PMQR and β-lactamase genes and similar antimicrobial resistance. Because PMQR genes in isolates from commercial layer chickens could enter the food supply and directly affect humans, control of ciprofloxacin resistance is needed.

Molecular characteristics of fluoroquinolone-resistant avian pathogenic Escherichia coli isolated from broiler chickens

Avian pathogenic Escherichia coli (APEC) is a major pathogen in the poultry industry worldwide including Korea. In this study, the phenotypic and genotypic characteristics of 33 fluoroquinolone (FQ)-resistant APEC isolates from broilers were analyzed. All FQ-resistant APEC isolates showed amino acid exchanges at both gyrA and parC and high minimal inhibitory concentrations for FQs. A total of 11 (33.3%) isolates were positive for the plasmid-mediated quinolone resistance (PMQR) genes, qnrA (8 isolates) and qnrS (3 isolates), and showed multidrug resistance. Among the 11 PMQR-positive isolates, 1 and 2 isolates carried blaCTX-1 and blaCTX-15, respectively, as extended-spectrum β-lactamase (ESBL) producers, and the non-ESBL gene, blaTEM-1, was found in 4 isolates. Among 3 aminoglycoside-resistant isolates, aac(3)-II was only detected in 1 isolate. All 8 APEC isolates with resistance to tetracycline carried the tetA gene. Overall, 6 of the 7 trimethoprim-sulfamethoxazole-resistant isolates carried the sul1 or sul2 genes, while only 2 of the 8 chloramphenicol-resistant isolates carried the catA1 gene. Although 9 isolates carried class I integrons, only 4 isolates carried the gene cassettes dfrA12-aadA2 (2 isolates), dfrA17-aadA5 (1 isolate), extX-psp-aadA2 (1 isolate), and dfrA27 (1 isolate). The most common plasmid replicon was FIB (8 isolates, 72.7%), followed by K/B (4 isolates, 36.4%). Antimicrobial resistance monitoring and molecular analysis of APEC should be performed continuously to surveil the transmission between poultry farms.

Genetic Characterization of Fluoroquinolone Resistance in Salmonella enterica Serovar Gallinarum Isolates from Chicken in Korea

Salmonella enterica serovar Gallinarum is a nonmotile host-adapted Salmonella that causes fowl typhoid (FT), and an outbreak of FT is characterized by anorexia, greenish-yellow diarrhea, paleness, and sudden death with high mortality in poultry. To control and treat FT in commercial chickens, fluoroquinolones are widely used in Korea. This study aimed to investigate the genetic characteristics of fluoroquinolone-resistant Salmonella Gallinarum isolates from 2014-18 from chicken in Korea. A total of 35 ciprofloxacin (CIP)-resistant Salmonella Gallinarum was tested, and 22 (62.9%) isolates were observed to have multidrug resistance. All isolates had a mutation at the Ser83 or Asp87 codon in the gyrA gene, whereas three isolates had only double mutations at Ser83 → Phe and Asp87 → Asn or Ser83 → Phe and Asp87 → Gly. Minimum inhibitory concentrations of isolates with double mutations were relatively higher (≥8 mg/L for CIP and ≥16 mg/L for enrofloxacin) than those of other isolates with a single mutation in gyrA. Among 35 CIP-resistant Salmonella Gallinarum, plasmid-mediated quinolone resistance genes were detected in six (17.1%) isolates, and qnrB and qnrS were detected in four and two isolates, respectively. In the distribution of antimicrobial resistance genes in 35 CIP-resistant Salmonella Gallinarum, ant(2″)-I (54.3%) was the most prevalent gene, followed by TEM-1 (14.3%), sul1 (11.4%), and cmlA (5.7%). Fifteen (42.9%) of the 35 CIP-resistant Salmonella Gallinarum also carried class 1 integrons, which showed five types of resistance gene cassettes: aadA2 (7 isolates), aadA2 + dfrA12 (5 isolates), and aadA1 + aad A2 (3 isolates). Among plasmid replicons, 23 isolates (65.7%) carried five different plasmid replicons: Frep (9 isolates), FIB (7 isolates), FIIA (6 isolates), B/O (4 isolates), and I1 (3 isolates). These results suggest that continued monitoring of fluoroquinolone resistance is necessary to preserve the effectiveness of fluoroquinolones in poultry and to surveil the transmission to humans through the food chain.

Detection of multidrug-resistant Gram-negative bacteria from imported reptile and amphibian meats

AIMS

The food supply is a potential source of antimicrobial resistance. Current surveillance programmes targeting food are limited to beef, pork and poultry and do not capture niche products. In this study, imported reptile and amphibian products were screened for antimicrobial-resistant bacteria.

METHODS AND RESULTS

In all, 53 items including soft shell turtles, frog legs, geckos, snakes and a turtle carapace were purchased from specialty markets in Vancouver and Saskatoon, Canada. Samples were selectively cultured for Salmonella sp., Escherichia coli, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and meropenem-resistant organisms. Salmonella, all pan-susceptible, were grown from six dried geckos. Escherichia coli were isolated from 19 samples, including ESBL producers from six items. One multidrug-resistant E. coli possessed both the bla_CTX-M-55 and mcr-1 genes. An NDM-1-producing Acinetobacter sp. was also isolated from a dried turtle carapace.

CONCLUSIONS

Our results suggest that imported reptile and amphibian meats are an underappreciated source of resistant bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

The international trade of food may play a role in the dissemination of resistant bacteria. The presence of these bacteria in niche market foods represents a risk of unknown magnitude to public health and a gap in current national resistance surveillance programmes.

Antibiotic-resistant Escherichia coli isolated from urban rodents in Hanoi, Vietnam

Antimicrobial resistance (AMR) is a global public health concern for both clinical and veterinary medicine. Rodent feces are one of the major infectious sources of zoonotic pathogens including AMR bacteria. So far, there are limited studies reported focused on Escherichia coli isolated in rodent feces from rural and suburban areas in Vietnam. In this study, we investigated the prevalence of antimicrobial resistance in E. coli isolated from feces samples of 144 urban rodents caught in Hanoi, Vietnam. A total of 59 AMR E. coli was isolated from urban rodents of which 42 were multidrug-resistant (MDR) isolates (resistance to at least three classes of antimicrobial agents), four were extended-spectrum β-lactamase (ESBL) producing isolates and five were colistin-resistant isolates. The highest prevalence of the resistance was against ampicillin (79.7%: 47/59), followed by tetracycline (78.0%: 46/59), nalidixic acid (67.8%: 40/59), sulfamethoxazole-trimethoprim (59.3%: 35/59), chloramphenicol (45.8%: 27/59), ciprofloxacin (44.1%: 26/59), cefotaxime (30.5%: 18/59), cefodizime (23.7%: 14/59), amoxicillin-clavulanate (22.0%: 13/59), and gentamicin (22.0%: 13/59). With regard to the virulence genes associated with diarrheagenic E. coli (DEC), only aaiC gene found in one AMR isolate. In general, the use of antimicrobials does not aim to treat rodents except for companion animals. However, our findings show the carriage of AMR and MDR E. coli in urban rodents and highlight the potential risk of rodents in Hanoi acting as a reservoir of transferable MDR E. coli, including ESBL-producing, colistin-resistant E. coli, and virulence-associated with DEC.

Alliance of Efflux Pumps with β-Lactamases in Multidrug-Resistant Klebsiella pneumoniae Isolates

Nosocomial infections caused by Klebsiella pneumoniae are primarily characterized by a high prevalence of extended-spectrum β-lactamases (ESBL's) and a soaring pace of carbapenemase dissemination. Availability of limited antimicrobial agents as a therapeutic option for multidrug-resistant bacteria raises an alarming concern. This study aimed at the molecular characterization of multidrug-resistant K. pneumoniae clinical isolates and studied the role of efflux pumps in β-lactam resistance. Thirty-three isolates confirmed as ESBL-positive K. pneumoniae that harbored resistance genes to major classes of antibiotics. The results showed that CTX-M15 was the preeminent β-lactamase along with carbapenemases in ESBL-positive isolates. However, the efficacy of different antibiotics varied in the presence of lactamase inhibitors and efflux pump inhibitors (EPIs). Those showing increased efficacy of antibiotics with EPI were further explored for the expression of efflux pump genes and expressed a significantly different level of efflux pumps. We found that an isolate had higher expression of kpnF (SMR family) and kdeA (MATE family) pump genes relative to RND family pump genes. No mutations were observed in the genes for porins. Together, the findings suggest that β-lactamases are not the only single factor responsible for providing resistance against the existing β-lactam drugs. Resistance may increase many folds by simultaneous expression of RND family (the most prominent family in Gram-negative bacteria) and other efflux pump family.

Molecular characteristic of antimicrobial resistance of Salmonella Gallinarum isolates from chickens in Korea, 2014 to 2018

Fowl typhoid (FT), which is caused by Salmonella enterica serovar Gallinarum (S. Gallinarum), leads to high morbidity and acute or subacute mortality in chickens of all ages. Although a live S. Gallinarum 9R vaccine was introduced in 2001 for commercial layer chickens in Korea, until recently, a variety of antimicrobials were widely used to prevent or treat FT. In this study, we investigated antimicrobial resistance in S. Gallinarum strains isolated from 2014 to 2018 and characterized the multidrug-resistant (MDR) strains to better understand the resistance trends in recent isolates. A total of 130 S. Gallinarum isolates were collected from chickens with FT, and the isolates showed highest rates of resistance to nalidixic acid (78.5%), followed by gentamicin (52.3%), ciprofloxacin (26.9%), and ampicillin (14.6%). Particularly, significant increases (P < 0.05) in the frequencies of resistance to the following antimicrobials were observed: ampicillin (from 7.7 to 28.6%), amoxicillin-clavulanate (from 0.0 to 10.7%), nalidixic acid (from 69.2 to 100.0%), ciprofloxacin (from 15.4 to 50.0%), chloramphenicol (from 0.0 to 17.9%), and colistin (from 0.0 to 14.3%). The prevalence of MDR isolates also rapidly increased from 23.1% in the 2014 to 60.7% in the 2018 (P < 0.05). The distribution of antimicrobial resistance genes in the 39 MDR S. Gallinarum isolates was as follows: ant(2")-I gene (22 isolates), blaTEM-1 gene (13 isolates), sul1 (9 isolates), sul2 (3 isolates), cmlA (3 isolates), and qnrB (3 isolates). Of 39, 25 (64.1%) MDR S. Gallinarum isolates also carried class 1 integrons, and these showed 5 types of resistance gene cassettes: dfrA12+aadA2 (36.0%), aadA2 (36.0%), aadA1-aadA2 (20.0%), dfrA12+catB3+aadA2 (4.0%), and dfrA12 (4.0%). Among the plasmid replicons, B/O (33.3%) was more prevalent than the other replicon types, followed by Frep (25.0%), FIIA (19.4%), FIB (13.9%), and I1 (8.3%). Antimicrobial resistance may become a serious problem because many drugs are likely ineffective for the treatment of FT. Therefore, these data support the critical need for comprehensive surveillance of antimicrobial resistance in poultry.

Identification of antimicrobial resistant bacteria from plant-based food products imported into Canada

The role of plant-based foods in the epidemiology of antimicrobial resistance has been inadequately studied. In this investigation, resistant organisms from vegetables, fruits and spices imported into Canada were identified and characterized. A total of 143 products imported from primarily Asian and African countries were purchased from international markets in Saskatoon, Saskatchewan. Samples were selectively cultured for bacterial species where resistance is known to be emerging. The proportions of samples positive for each organism were as follows: E. coli (n = 13, 9.1%), Salmonella spp. (n = 2, 1.4%), ESBL producing Enterobacter spp. (n = 2, 1.4%) and K. pneumoniae (n = 2, 1.4%), S. aureus (n = 7, 4.9%) and Enterococcus spp. (n = 66, 46.2%). Antimicrobial minimum inhibitory concentrations were determined by broth micro-dilution and agar-dilution. Based on the susceptibility of each organism, isolates were screened for resistance genes (β-lactamases and plasmid mediated quinolones resistance determinants) by PCR. Extended-spectrum β-lactamase producing Enterobacteriaceae and methicillin resistant S. aureus (MRSA) were identified from 6/143 (4.2%) and 2/143 (1.4%) of samples respectively. The qnrB, qnrS and aac(6')-Ib-cr plasmid mediated quinolone resistance determinants were identified in 2/143 (1.4%) of samples tested. None of the Enterobacteriaceae isolates were resistant to meropenem or colistin. Similarly, all Enterococcus isolates remained susceptible to ampicillin, penicillin and vancomycin. Finding multi-drug resistant bacteria which are frequently isolated from human infections is concerning, although the contribution of the global food trade to the dissemination of resistance remains cryptic. These results suggest that imported plant-based foods may be an underappreciated source of clinically relevant resistant organisms. Further study is required to address these gaps in our understanding of the epidemiology of resistance, and the magnitude of the risk posed to human health by these organisms.