• Journal of Life Science
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• v.20 no.6
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• pp.964-967
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• 2010

Plasmid-mediated quinolone resistance (PMQR) determinants have been contributed to quinolone resistance of gram-negative bacteria worldwide. However, little data on the prevalence of these determinants in bacteria from animals are available in Korea. In this study, the prevalence of PMQR genes was investigated with E. coli originating from diseased animals. Among 55 E. coli tested, 11 showed PMQR genes by PCR. The most prevalent genotype was qepA (14.5%), followed by aac(6')-Ib-cr (7.3%) and qnrS (1.8%). Interestingly, two isolates with PMQR genes did not show quinolone resistance in this study. The isolates exhibited higher fluoroquinolone resistance in aac(6')-Ib-cr in combination with qnrS or qepA compared with aac(6')-Ib-cr only. In a conjugal transfer test, PMQR genes were transferred from donor to recipient.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1180-1183
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• 2020

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.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.422-430
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• 2018

The inappropriate and widespread use of quinolones in humans and animals may cause accelerated emergence and spread of antimicrobial-resistant determinants. In this study, we investigated quinolone resistance mechanisms in a total of 65 nalidixic acid-resistant E. coli isolated from swine rectal swabs (N=40) and clinical specimens (N=25). Antimicrobial susceptibilities were determined by the disk diffusion method. PCR and DNA sequencing were performed for investigations of genes and mutations associated with quinolone resistance. In our study, 62 of 65 nalidixic acid-resistant E. coli harbored mutations in gyrA, parC, and/or parE genes; of the 65 isolates, 62 (95.4%) had mutations in the gyrA gene, 35 (53.8%) had mutations in the parC gene, 7 (10.8%) had mutations in the parE gene. The 35 isolates harbored mutations in two genes, gyrA and parC. Plasmid-mediated quinolone resistance (PMQR) determinants were investigated in the 65 isolates. Thirteen of 65 nalidixic acid-resistant E. coli contained the qnrS gene and 10 of those isolates had mutations in the gyrA, parC, and/or parE genes. We confirmed that an important mechanism of quinolone resistance in E. coli isolated from human and swine involves chromosomal mutations in the gyrA, parC, and/or parE genes with increasing use of quinolone for treatment or additives.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.210-216
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• 2016

Recently, there has been a considerable increase in the prevalence of CTX-M type extended-spectrum ${\beta}$-lactamase (ESBL)-producing E. coli isolates worldwide, including Korea. To investigate the ESBL genes in the E. coli strains isolated from a university hospital in the Chungcheong area, a study was conducted using PCR amplification and nucleotide sequence analysis of the amplified products to detect the plasmid mediated quinolone resistance (PMQR) genes in ESBL producing E. coli isolates. The number of CTX-M-14 producing isolates was 25 (16.0%) isolates, and of them, 9 (5.8%) isolates also produced CTX-M-15. All CTX-M type ESBL producing E. coli isolates showed resistance to cefotaxime. Twelve (48%) CTX-M type ESBL producing E. coli isolates contained the PMQR genes, 8 contained qnrS1, and 8 contained aac(6')-Ib-cr. Four isolates harbored both qnrS1 and aac(6')-Ib-cr genes. In our study, we confirmed that the plasmid mediated antimicrobial resistant determinants-the ESBL and PMQR genes-were distributed in the E. coli isolates. To prevent further spreading of the resistant genes among the E. coli isolates, consistent effort is required to investigate and monitor the resistant genes.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.185-190
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• 2014

The aim of this study was to investigate the prevalence of quinolone resistant E. coli from raw bulk milk and to characterize the resistance determinants. In this study, the gyrA, gyrB, parC, and parE quinolone resistance determining regions (QRDR) were sequenced from quinolone resistant E. coli isolates. Also, the presence of plasmid-mediated quinolone resistance (PMQR) and the expression of efflux pump genes based on quantitative real-time PCR (qRT-PCR) were investigated. Of the 487 coliform bacteria, 9 strains showed nalidixic acid resistance, and 6 of the 9 nalidixic acid resistant isolates were also ciprofloxacin resistant. These 9 strains had a single mutation at codon 83 (S83L) in gyrA, 2 of them had double mutations at codon 83 and 87 (S83L and D87N) in gyrA and 3 of the 9 isolates had single mutations at codon 80 (S80I) in parC. None of the 9 isolates harbored PMQR determinants. Compared with wild-type E. coli ATCC 25922, an over-expression of the acrB gene (2.15-5.74 fold), encoding the pump component of the AcrAB-TolC efflux pump was observed in 4 of 6 ciprofloxacin resistant isolates. This study identified the quinolone resistance mechanism of E. coli isolated from raw milk samples in Gyeonggi-do.

• Biomedical Science Letters
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• v.26 no.2
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• pp.120-126
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• 2020

Fluoroquinolone (FQ) resistant uropathogenic Escherichia coli (UPEC) have become a major problem in urinary tract infections (UTIs). The purpose of this study was to compare the quinolone resistance-determining region (QRDR) and plasmid mediated quinolone resistance (PMQR) determinants of FQ resistant UPEC between 1989 and 2010-2014. A total of 681 strains of UPEC clinical isolates was collected from Korean healthcare facility in 1989 (123 strains) and in 2010-2014 (558 strains). The minimum inhibitory concentrations (MICs) of FQs were determined by agar dilution method. QRDRs (gyrA, gyrB, parC and parE) and PMQR determinants (qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA) were analyzed polymerase chain reaction and sequencing method. Among 681 isolates, FQ resistant UPEC were 3 strains (2.4%) in 1989 isolates and 220 strains (39.4%) in 2010-2014 isolates. The rate of the FQ resistant UPEC strains in 2010-2014 isolates was increased than that of in 1989 isolates. UPEC isolates from 1989 and 2010-2014 were shown to carry mutations in gyrA (Ser83 and Asp87), gyrB (Ser464 and Thr469), parC (Ser80 and Glu84) and parE (Glu460, Ser458, Ile464 and Leu445). The most common mutations of QRDRs in 1989 isolates were Ser83Leu and Asp87Gly in gyrA and Ser80Ile in parC (2 strains: 66.7%) while those in 2010-2014 isolates were Ser83Leu and Asp87Asn in gyrA and Ser80Il2 and Glu84Val in parC (88 strains: 40.0%). PMQR determinants were detected only in 2010-2014 UPEC strains (47 strains: 21.4%).

• YAKHAK HOEJI
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• v.60 no.1
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• pp.1-7
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• 2016

The aim of this study was to investigate the prevalence of quinolone resistant E. coli from retail meat and to characterize the resistant determinants. Determination of minimum inhibitory concentration, the sequence analysis of gyrA, gyrB, parC, and parE quinolone resistance determining regions (QRDR), the presences of plasmid mediated quinolone resistance (PMQR) and the expression of efflux pump genes were investigated. Of the total 277 retail meat samples, 67 coli form bacteria were isolated. 15 of 67 isolates showed nalidixic acid resistance and 7 of 15 nalidixic acid resistant isolates were also resistant to ciprofloxacin, moxifloxacin and levofloxacin. 11 of 15 nalidixic acid resistant strains were isolated from chicken, 2 of 15 were isolated from beef and 2 of 15 were isolated from pork samples. 11 of 15 nalidixic acid resistant strains have single mutation at codon 87 (D87N or D87G) in gyrA, 2 of 11 gyrA mutants have double mutations at codon 86 and 87 (L86A and L87I) in parC with mutations at codon 434+445+465 or 429 in gyrB. 2 of 15 resistant isolates harbored qnrS, a PMQR determinant. Over expression of the acrB gene, efflux pump gene (3.93~16.53 fold), was observed in 10 of 15 resistant isolates.

• Journal of Microbiology and Biotechnology
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• v.26 no.9
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• pp.1605-1612
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• 2016

Quinolone-resistant Salmonella strains were isolated from patient samples, and several quinolone-sensitive strains were used to analyze mutations in the quinolone resistance-determining region (QRDR) of gyrA, gyrB, parC, and parE and to screen for plasmid-mediated quinolone resistance. Among the 21 strains that showed resistance to nalidixic acid and ciprofloxacin (MIC 0.125-2.0 μg/ml), 17 strains had a mutation in QRDR codon 87 of gyrA, and 3 strains had a single mutation (Ser83 → Phe). Another cause of resistance, efflux pump regulation, was studied by examining the expression of acrB, ramA, marA, and soxS. Five strains, including Sal-KH1 and Sal-KH2, showed no increase in relative expression in an analysis using the qRT-PCR method (p < 0.05). In order to determine the genes involved in the resistance, the Sal-9 isolate that showed decreased susceptibility and did not contain a mutation in the gyrA QRDR was used to make the STM (MIC 8 μg/ml) and STH (MIC 16 μg/ml) ciprofloxacin-resistant mutants. The gyrA QRDR Asp87 → Gly mutation was identified in both the STM and STH mutants by mutation analysis. qRT-PCR analysis of the efflux transporter acrB of the AcrAB-TolC efflux system showed increased expression levels in both the STM (1.79-fold) and STH (2.0-fold) mutants. In addition, the expression of the transcriptional regulator marA was increased in both the STM (6.35-fold) and STH (21.73-fold) mutants. Moreover, the expression of soxS was increased in the STM (3.41-fold) and STH (10.05-fold) mutants (p < 0.05). Therefore, these results indicate that AcrAB-TolC efflux pump activity and the target site mutation in gyrA are involved in quinolone resistance.

• Korean Journal of Veterinary Service
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• v.42 no.1
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• pp.17-24
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• 2019

The aim of this study was to investigate the prevalence and characterization of plasmid-mediated quinolone resistance (PMQR) gene in 79 Enterobacteriaceae isolated from dogs and cats. Of 79 isolates, PMQR genes were found in 10 (12.7%) isolates, including aac(6')-lb-cr, qnrB, qnrS and qnrA detected alone or in combination in 8 (10.1%), 4 (5.1%), 2 (2.5%) and 1 (1.3%) isolates, respectively. Interestingly, two qnrS genes were detected in nalidixic acid and ciprofloxacin susceptible isolates. Extended-spectrum ${\beta}$-lactamase (ESBL) was detected in 90% (9 isolates) of PMQR positives isolates. Among ESBL genes, CTX-M, TEM and SHV were detected in 9, 8 and 3 isolates, respectively. Almost all PMQR genes were detected in co-existence with ESBL genes. All PMQR positives isolates were multidrug resistance (i.e. resistant to five or more antibiotics). qepA, OXA and CMY-2 genes were not found. The six transconjugants were obtained by conjugation experiment. The aac(6')-lb-cr, qnrB and qnrS were co-transferred with CTX-M, TEM and/or SHV, whereas qnrA was not observed among transconugants. This is the first report of the presence of aac(6')-lb-cr and qnrA gene among Enterobacteriaceae isolates from dogs in Korea. The prudent use of antimicrobials and continuous monitoring for companion animals are required.

• Korean Journal of Clinical Laboratory Science
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• v.53 no.3
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• pp.217-224
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• 2021

Fluoroquinolone (FQ) resistant gram-negative pathogens have emerged worldwide, and the recent increase in FQ resistant Escherichia coli is of great concern in Korea. This study investigated FQ resistance determinants and the epidemiological relationship of 56 ciprofloxacin-resistant E. coli isolated from a tertiary hospital in Daejeon, South Korea from June to December 2018. Molecular epidemiology was investigated by multilocus sequence typing (MLST). Polymerase chain reaction (PCR) and sequence analysis were performed to identify chromosomal mutations in the quinolone resistance determining regions (QRDR) of gyrA, gyrB, parC, and parE and to describe the occurrence of the following plasmid-mediated quinolone resistance (PMQR) genes: aac(6)-Ib-cr, qepA, qnrA, qnrB, qnrC, qnrD, and qnrS. MLST analysis showed 12 sequence types (STs) and the most prevalent ST was ST131 (31/56, 55.4%), followed by ST1193 (13/56, 23.2%), and ST405 (3/56, 5.4%). In 56 ciprofloxacin-resistant E. coli isolates, Ser83→Leu and Asp87→Asn in gyrA and Ser80→Ile and Glu84→Val in parC (51.8%, 29/56) were the most frequent amino acid substitutions and aac(6)-Ib-cr (33.9%, 19/56) was the most common PMQR gene. These results of FQ resistance determinants were more frequently observed in ST131 compared with other clones. Continuous monitoring of the epidemiological characteristics of ciprofloxacin-resistant E. coli isolates and further investigation of FQ resistance determinants are necessary.