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

Molecular characteristics of fluoroquinolone-resistant Escherichia coli isolated from suckling piglets with colibacillosis

Objectives

Colibacillosis is a frequent enteric disease in the pig industry that causes significant economic losses. The objective of this study was to investigate the molecular characteristics of fluoroquinolone (FQ)-resistant E. coli isolates from suckling piglets with colibacillosis.

Results

A total of 43 FQ-resistant E. coli isolates were tested in this study and all isolates showed multi-drug resistance (MDR) and mutations in quinolone resistance determining regions (gyrA or parC). Especially, FQ-resistant E. coli isolates with double mutations in both gyrA and parC were shown a high FQs minimum inhibitory concentration (≥ 64 mg/L for ciprofloxacin, ≥ 128 mg/L for enrofloxacin, and ≥ 256 mg/L for norfloxacin). Among 43 FQ-resistant E. coli isolates, 12 (27.9%) were showed plasmid-mediated quinolone resistance (PMQR) positive E. coli. Prevalence of PMQR gene, aac(6’)-Ib-cr, qnrS, and qepA, were identified in 7, 3, and 2 E. coli isolates, respectively. We identified the following in PMQR-positive E. coli isolates: the tetracycline resistance genes tetD (12 isolates, 100.0%), tetE (12 isolates, 100.0%), tetA (11 isolates, 91.7%), and tetB (1 isolate, 8.3%); β-lactamases–encoding blaCMY-2 (10 isolates, 83.3%), blaTEM-1 (7 isolates, 58.3%), blaOXA-1 (7 isolates, 58.3%), blaSHV-1 (3 isolates, 16.7%), and blaAAC-2 (1 isolate, 8.3%); and the chloramphenicol resistance genes (10 isolates, 83.3%); the sulfonamide resistance genes sul1 (9 isolates, 75.0%) and sul2 (10 isolates, 83.3%); the aminoglycoside modifying enzyme gene aac(3)-II (2 isolates, 16.7%). The F4 (7 isolates, 58.3%), LT:STb:EAST1 (5 isolates, 41.7%), and paa (3 isolates, 25.0%) were most common fimbrial antigen, combinations of toxin genes, and non-fimbrial adhesins genes, respectively. All PMQR-positive E. coli carried class I integrons but only 4 isolates carried the gene cassette. The most prevalent plasmid replicon was FIB (9 isolates, 75.0%), followed by FIC, HI1, and N (7 isolates, 58.3%), respectively.

Conclusions

Because FQ-resistant E. coli can serve as a reservoir of FQ resistant genetic determinants that can be transferred to pathogenic bacteria in humans or pigs, this represents a public health hazard.

Plasmid-mediated quinolone resistance determinants in fluoroquinolone-nonsusceptible Escherichia coli isolated from patients with urinary tract infections in a university hospital, 2009-2010 and 2020: PMQR in UTI E. coli

OBJECTIVES

This study aimed to characterize the plasmid-mediated quinolone resistance (PMQR) in fluoroquinolone non-susceptible E. coli (FQNSEC) isolated from patients with urinary tract infections (UTIs) in 2019-2010 and 2020.

METHODS

A total of 844 E. coli isolates were collected from UTI patients at National Cheng Kung University Hospital (NCKUH). The antimicrobial susceptibility of E. coli isolates to 21 antibiotics was determined by disk diffusion tests. The distribution of phylogenetic groups, virulence factor, and PMQR genes, was determined by PCR. Conjugation assays were performed to investigate the transferrability of qnr genes from FQNSEC isolates to E. coli C600.

RESULTS

We found 211 (41.9%) and 152 (44.7%) E. coli isolates were FQNSEC in 2009-2010 and 2020, respectively. Phylogenetic group B2 was dominant in FQNSEC isolates (52.34%), followed by group F (10.47%), group B1 (9.64%), and group D (9.64%). FQNSEC isolates were more resistant to 17 of 19 tested antimicrobial agents, compared to the FQ susceptible E. coli. PMQR screening results showed that 34, 22, and 10 FQNSEC isolates containing aac(6')-Ib-cr, qnr genes, and efflux pump genes (qepA or oqxAB), respectively. PMQR E. coli isolates were more non-susceptible to gentamicin, amoxicillin, ampicillin/sulbactam, imipenem, cefazolin, cefuroxime, cefmetazole, ceftriaxone, ceftazidime, and cefepime, compared to non-PMQR FQNSEC. Moreover, 16 of 22 qnr-carrying plasmids were transferrable to the recipient C600.

CONCLUSION

Here, we reported the high prevalence of MDR- and XDR-E. coli in FQNSEC isolates. Moreover, qnr-carrying plasmids were highly transferable and lead to the resistance to other classes of antibiotics in the transconjugants.

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.

Molecular characterization of fluoroquinolone-resistant Escherichia coli from broiler breeder farms

Fluoroquinolones (FQs) have been used effectively antimicrobial agents of choice for treatment of various infections caused by E. coli and FQs-resistance of E. coli from broiler breeders has been implicated in its vertical transmission to their offspring. The objective of this study investigated the phenotypic and genotypic characteristics of FQ-resistant E. coli isolates from broiler breeder farms in Korea. A total of 106 FQ-resistant E. coli isolates were tested in this study and all isolates had mutations in quinolone resistance determining regions; all (100%) had mutations in gyrA, 89 (84.0%) had mutations in parE, 8 (7.5%) isolates showed the mutations with parC and parE, and none had mutations in gyrB. The predominant mutation type was double mutation in gyrA (S83L and D87N), and all FQ-resistant E. coli isolates that had mutations in parC or parE also had double mutations in gyrA. Especially, FQ-resistant E. coli isolates which possessed double mutations in gyrA in combination with double mutations in parC or single mutations in both parC and parE were shown high levels of minimum inhibitory concentrations rage. Of the 23 plasmid-mediated quinolone resistance (PMQR)-positive E. coli isolates, qnrS was detected in 10 (9.4%) isolates, and followed by qnrA (7 isolates, 6.6%), qnrB (4 isolates, 3.8%), and aac(6′)-Ib-cr (2 isolates, 1.9%). Sixteen (69.6%) of the 23 PMQR-positive E. coli isolates harbored class 1 integrons with four different gene cassette arrangements and total of 9 plasmid replicon types were also identified in 23 PMQR-positive E. coli isolates. This is the first study to investigate the prevalence and characteristics of FQ-resistant and PMQR-positive E. coli isolated from the broiler breeder in Korea; it supports that constant monitoring and studies at the broiler breeder level are required to prevent the pyramidal transmission of FQ-resistant E. coli.

Antimicrobial Resistance Profiles, Virulence Genes, and Genetic Diversity of Thermophilic Campylobacter Species Isolated From a Layer Poultry Farm in Korea

Thermophilic Campylobacter species are among the major etiologies of bacterial enteritis globally. This study aimed at assessing the antimicrobial resistance (AMR) profiles, virulence genes, and genetic diversity of thermophilic Campylobacter species isolated from a layer poultry farm in South Korea. One hundred fifty-three chicken feces were collected from two layer poultry farms in Gangneung, South Korea. The Campylobacter species were isolated by cultural techniques, while PCR and sequencing were used for species confirmation. Antimicrobial susceptibility testing for six antimicrobials [ciprofloxacin (CIP), nalidixic acid (NAL), sitafloxacin (SIT), erythromycin (ERY), tetracycline (TET), and gentamicin (GEN)] was carried out by broth microdilution. Three AMR and nine virulence genes were screened by PCR. Genotyping was performed by flaA-restriction fragment length polymorphism (RFLP) and multilocus sequence typing (MLST). Of the 153 samples, Campylobacter spp. were detected in 55 (35.9%), with Campylobacter jejuni and Campylobacter coli being 49 (89.1%) and six (10.9%), respectively. High-level resistance was observed for CIP (100%), NAL (100%), and TET (C. jejuni, 93.9%; C. coli: 83.3%). No resistance was observed for SIT. The missense mutation (C257T) in gyrA gene was confirmed by sequencing, while the tet(O) gene was similar to known sequences in GenBank. The rate of multidrug-resistant (MDR) strains was 8.2%, and they all belonged to C. jejuni. All Campylobacter isolates possessed five virulence genes (cdtB, cstII, flaA, cadF, and dnaJ), but none possessed ggt, while the rates for other genes (csrA, ciaB, and pldA) ranged between 33.3 and 95.9%. The flaA-RFLP yielded 26 flaA types (C. jejuni: 21 and C. coli: five), while the MLST showed 10 sequence types (STs) for C. jejuni and three STs for C. coli, with CC-607 (STs 3611) and CC-460 (ST-460) being predominant. Among the 10 STs of C. jejuni, three were newly assigned. The findings of this study highlight the increased resistance to quinolones and TET, the virulence potential, and the diverse genotypes among Campylobacter strains isolated from the layer poultry farm.