Distribution characteristics of integrons and plasmid-mediated quinolone resistance genes in Klebsiella aerogenes clinical isolates / 中华微生物学和免疫学杂志

Objective:To investigate the distribution of integrons and plasmid-mediated quinolone resistance (PMQR) genes in clinical isolates of Klebsiella aerogenes and to analyze the relationship between integrons and bacterial resistance to antimicrobial agents. Methods:Ninety-one Klebsiella aerogenes strains isolated from clinical samples in the Fengxian District Central Hospital from November 2015 to March 2021 were used in this study. Class 1 and class 2 integron-integrase genes ( intI1 and intI2) and PMQR genes were screened by PCR. The types of promoters and gene cassette arrays of variable regions were determined by sequencing. Besides, the relationship between integrons and antimicrobial resistance was analyzed. Results:The resistance rate of the 91 Klebsiella aerogenes isolates to aztreonam was more than 40.00% and the resistance rates to other commonly used antimicrobial agents were less than 35.00%. Among the 91 isolates, 30 carried the intI1 gene, while none of them carried the intI2 gene. Seven class 1 integron gene cassette arrays of variable regions were detected and the gene cassette array of aac(6′)-11 C- ΔereA2- IS1247- aac3- arr- ΔereA2 was detected in Klebsiella aerogenes. PcH1 with weak activity was the predominant variable region promoter of class 1 integrons. The detection rates of intI1-positive and intI1-negative isolates in ICU, neurosurgery and other clinical departments were statistically different ( P<0.05). The resistance rate of intI1-positive isolates to some commonly used antibiotics was significantly higher than that of intI1-negative isolates ( P<0.05). qnrS gene was the prevalent PMQR gene. The detection rates of integrons and PMQR genes in Klebsiella aerogenes isolates was low except for the strains isolated in 2016. Conclusions:Antimicrobial resistance in Klebsiella aerogenes was closely related to integrons. The distribution of integrons in Klebsiella aerogenes strains isolated from different clinical departments was different, and the monitoring of drug-resistant strains should be strengthened in ICU and neurosurgery. The resistance to quinolones in Klebsiella aerogenes strains in this region was mainly related to qnrS gene.

Molecular characteristics of qnrS1-positive Escherichia coli resistant to quinolone / 中华微生物学和免疫学杂志

Objective To analyze the molecular characteristics of qnrS-positive Escherichia coli ( E. coli) strains resistant to quinolone. Methods A total of 57 qnrS1-positive clinical isolates were collect-ed from Fujian Medical University Union Hospital. Plasmid-mediated quinolone resistance ( PMQR) genes [qnrA, qnrB, qnrC, qnrD, aac(6′)-Ib-cr, qepA and oqxAB] andβ-lactamase genes (blaCTX-M-1, blaCTX-M-2, blaCTX-M-8 , blaCTX-M-9 , blaSHV and blaTEM ) were detected by PCR and then sequenced. Agar dilution method was used to analyze the antimicrobial susceptibility of the qnrS1-positive strains. Phylogenetic analysis was conducted using PCR. Multilocus sequence typing ( MLST) was performed for phenotyping. Enterobacterial repetitive intergenic consensus-polymerase chain reaction ( ERIC-PCR) was used to evaluate the genetic sim-ilarity between those isolates. Transferability of the qnrS1 genes carried by the 57 strains was examined by conjugation test with the sodiumazide-resistant E. coli J53 as the recipient strain. Mutations in the quinolone resistance-determining regions ( QRDR) in those strains were analyzed by PCR. Results All of the qnrS1-positive E. coli strains showed high resistance to quinolones. PMQR genes were harbored by 14 (24. 6％) isolates. Extended spectrum β-lactamases (ESBLs)-producing isolates accounted for 68. 4％. Mutations in the QRDR of gyrA, gyrB, parC and parE genes were found in 56 (98. 2％) strains and the most frequent point mutations were S83L (89. 5％) in gyrA gene, S80I (54. 4％) in parC gene and P415V (28. 1％) in parE gene. The qnrS1 gene was successful transferred from 13 (22. 8％) isolates to E. coli J53 by conjuga-tion. Five plasmid incompatibility groups were detected. Phylogenetic analysis showed that there were 36 (63. 2％), 13 (22. 8％), 1 (1. 8％) and 7 (12. 3％) isolates belonging to groups A, B1, B2 and D, respectively. The 57 qnrS1-positive E. coli strains were assigned to 50 ERIC types and 39 sequence types ( ST) based on the results of ERIC-PCR and MLST. Conclusions Mutations in the QRDR in E. coli strains were associated with qnrS1 gene and might play a critical role in the dissemination of quinolone-resistant bacteria.

Survey on the genes conferring plasmid-mediated quinolone resistance and those encoding β-lactamases in Escherichia coli isolates / 中国感染与化疗杂志

Objective To examine the prevalence of plasmid mediated quinolone resistance (PMQR) genes and their correlation with the genes encoding β-lactamases in E.coli isolates.Methods A total of 200 levofloxacin-and/or ciprofloxacin-resistant E.coli isolates were collected from Fujian Medical University Union Hospital during the period from July to December 2013.PCR method was used to screen these E.coli isolates for the presence of qnrA,qnrB,qnrC,qnrD,qnrS,aac(6')-Ib-cr,qepA,oqxAB genes,and the blaTEM,blasnv and blacTx-M genes in the PMQR positive strains.Agar dilution method was utilized to measure the antimicrobial susceptibility of PMQR-positive strains.Phylogenetic analysis was conducted by triplex PCR.Enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) was used to evaluate the genetic similarity between the PMQR-positive isolates.Results Of the 200 clinical isolates of E.coli,58 (29.0％)were PMQR-positive.And qnr,aac(6')-Ib-cr,oqxAB,and qepA genes were positive in 11 (5.5％),41 (20.5％),16 (8.0％),1 (0.5％) strains,respectively.The genes encoding CTX-M-1,CTX-M-9 and TEM type enzymes was positive in 32 (55.2％),17 (29.3％),and 1 (1.7％) of the PMQR-positive strains,respectively.The blasHv gene was not identified in any isolate.PMQR-positive strains were multi-drug resistant.Phylogenetic analysis indicated that 21 (36.2％),17 (29.3％),11 (19.0％),and 9 (15.5％) of the PMQR-positive strains belonged to group A,group D,group B2 and group B 1,respectively.ERIC-PCR suggested the PMQR-positive isolates belonged to 50 different types.Only one strain was non-typeable.Conclusions Most of the PMQR-related genes in E.coli are aac(6')-Ib-cr,qnr,and oqxAB in our hospital,which are highly relevant to β-1actamase genes.PMQR-positive strains may spread by way of non-clonal dissemination in our hospital.

Distribution of plasmid‑mediated quinolone resistance in Gram‑negative bacteria from a tertiary hospital in Nigeria.

Background: Until recently, mechanisms of resistance to quinolones in Gram‑negative bacteria were believed to be only chromosome encoded. However, emergence of plasmid‑mediated quinolone resistance (PMQR) has been reported worldwide. Aim: This study investigated distribution of PMQR in Gram‑negative bacteria from a tertiary hospital in eastern part of Nigeria. Materials and Methods: Seventy‑one nonduplicate Gram‑negative bacterial isolates of eight species were analyzed for antimicrobial susceptibility, genotypic detection of various PMQRs, typed by random amplified polymorphic DNA (RAPD) and analysis of plasmids present, including replicon typing. Results: The minimum inhibitory concentrations showed MIC90 values as high as 256 μg/ml for fluoroquinolones. Carriage of PMQR was found to be 35.2%. Twenty (28.2%) isolates carried various qnr genes, of which seven (9.9%) qnrA1; four (5.6%) qnrB1; eight (11.3%) qnrS1 while one (1.4%) encoded qnrD1. Eighteen (25.4%) isolates were positive for aac(6’)‑Ib‑cr while carriage of multiple genes exists in some strains. Similarly, 13 isolates (18.7%) were found to carry PMQR efflux pump gene, qepA. Conjugation experiments revealed that the plasmids once transferred coded for fluoroquinolone resistance. The transconjugant strains carried a common plasmid estimated to be 65 kb. These plasmids were untypable for replicon/incompatibility. Typing revealed high diversity among all species tested with no identical RAPD pattern seen. Conclusion: This study further confirms high level resistance to many antimicrobials in different species of Gram‑negative bacteria including fluoroquinolones and spread of PMQR genes in Southern Nigeria.

High prevalence of plasmid-mediated quinolone resistance determinants in Enterobacter cloacae isolated from hospitals of the Qazvin, Alborz, and Tehran provinces, Iran

Abstract: INTRODUCTION: Plasmid-mediated quinolone resistance (PMQR) is a growing clinical concern worldwide. The main aims of this study were to detect qnr-encoding genes and to evaluate the clonal relatedness of qnr-positive Enterobacter cloacae isolates. METHODS: A total of 116 E. cloacae isolates that were not susceptible to quinolone were obtained from seven hospitals in Tehran, five hospitals in Qazvin, and two hospitals in Karaj (Iran). Bacterial identification was performed using standard laboratory methods and API 20E strips. Quinolone resistance was determined using the Kirby-Bauer disk diffusion method according to the Clinical Laboratory Standards Institute (CLSI) guidelines. PCR and sequencing were employed to detect qnrA, qnrB, and qnrS genes, and clonal relatedness was assessed using the enterobacterial repetitive intergenic consensus (ERIC)-PCR method. RESULTS: In total, 45 (38.8%) and 71 (61.2%) of isolates showed high- and low-level quinolone resistance, respectively, and qnr-encoding genes were detected in 70 (60.3%) of them. qnrB1 [45 (38.8%) isolates] was the most commonly detected gene, followed by qnrS1 [28 (24.1%) isolates] and qnrB4 [18 (15.5%) isolates] either alone or in combination with other genes. The results of the ERIC-PCR revealed that 53 (75.7%) qnr-positive isolates were genetically unrelated. CONCLUSIONS: This study describes, for the first time, the high prevalence of the qnrB1, qnrS1, and qnrB4 genes among E. cloacae isolates in Iran. The detection of qnr genes emphasizes the need for establishing tactful policies associated with infection control measures in hospital settings in Iran.

Plasmid-mediated quinolone resistance in typhoidal Salmonellae: A preliminary report from South India.

Background: Fluoroquinolones are the drugs extensively employed for the treatment of Salmonella infections. Over the couple of decades that have elapsed since the introduction of fl uoroquinolones, resistance to these agents by Enterobacteriaceae family members has become common and widespread. Although fl uoroquinolone resistance is mediated by genomic DNA (deoxyribonucleic acid) as well as plasmid DNA, the plasmid-mediated quinolone resistance (PMQR) facilitates higher level resistance by interacting with genomic mechanism and is capable of horizontal spread. Materials and Methods: During a period of 1-year, 63 typhoidal Salmonellae were isolated from 14,050 blood cultures and one parietal wall abscess. 36 (56.25%) were Salmonella Typhi and 27 (42%) were Salmonella Paratyphi A. They were all screened for resistance by the disc diffusion method and their minimum inhibitory concentrations were determined using agar dilution, broth dilution and E-strip method. Ciprofl oxacin resistant isolates were screened for PMQR determinants by polymerase chain reaction assay. Results: All the 63 isolates were resistant to nalidixic acid. Among the 36 S. Typhi isolates 20 were resistant to ciprofl oxacin, of which 14 carried the plasmid gene qnrB and one carried the aac(6’)-Ib-cr gene. qnrA and qnrS genes were not detected. Ciprofl oxacin resistance was not seen in any of the S. Paratyphi A isolates. Conclusion: The antibiotic sensitivity pattern of typhoidal Salmonellae shows an increasing trend of PMQR. The allele B of qnr gene was found to be the predominant cause of PMQR in this study.

Pesquisa de genes de resistência a quinolonas em bacilos Gram negativos de origem clínica e ambiental / Research for genes of quinolone resistance in Gram negative bacilli from clinical and environmental origin

Introdução. Quinolonas são antimicrobianos sintéticos que inibem as enzimas DNA-girase e topoisomerase IV resultando na morte bacteriana. São altamente eficazes no tratamento de infecções bacterianas, especialmente causadas por bactérias Gram negativas, e portanto amplamente utilizados na medicina humana e veterinária, na qual também são empregados como profiláticos. Porém, o uso indiscriminado e inadequado levou ao aumento de bactérias resistentes a estes compostos. Esta resistência pode ocorrer devido a mutações nas enzimas DNA-girase e topoisomerase IV, e também por genes contidos em plasmídeos. Estes últimos são os principais responsáveis pela disseminação e circulação da resistência entre o meio ambiente e o ambiente hospitalar. Objetivos. Pesquisar genes de resistência a antimicrobianos do grupo das quinolonas em bactérias Gram negativas de origem clínica e ambiental que apresentam resistência fenotípica a este grupo. Material e Métodos. 73 cepas de Enterobacteriaceae e Aeromonas sp. de origem clínica e ambiental foram selecionadas para o estudo, e avaliadas quanto à sensibilidade aos antimicrobianos do grupo das quinolonas e à pesquisa de genes de resistência a este mesmo grupo e mutações no gene que codifica a enzima DNA-girase por meio de PCR e sequenciamento. Resultados. Das 73 cepas previamente selecionadas para compor o estudo, 65 foram utilizadas, devido à exclusão de perfis clonais similares. Nestas, foram observados os genes, qnrS1 (1,5 por cento ), qnrS2 (26,2 por cento ), qnrB1 (3,1 por cento ), qnrB19 (12,3 por cento ), qnrD1 (1,5 por cento ), aac(6)-Ib-cr (10,8 por cento ), oqxA (43,1 por cento ) e oqxB (41,5 por cento ), e duas variantes determinadas qnrB-like (3,1 por cento ) e qnrB69-like (1,5 por cento ). Os genes qnrA, qnrC e qepA não foram identificados. Mutações na enzima DNA-girase foram observadas em 97,9 por cento das cepas positivas para algum dos genes pesquisados...

Introduction. Quinolones are synthetic antimicrobial agents that inhibit DNA gyrase and topoisomerase IV enzymes resulting in bacterial death. They are highly effective in the treatment of bacterial infections, especially the ones caused by Gram negative bacteria, as well as for prophylaxy. Therefore they are widely used in human and veterinary medicine. However, indiscriminate and improper use led to an increase of bacteria resistance to these compounds. This resistance can be due to mutations in DNA gyrase and topoisomerase IV enzymes and also by genes contained in plasmids, which are mainly responsible for the spread and transmission of resistance between the environment and the hospital set. Objectives. To search for genes of resistance to quinolone antimicrobial agents in Gram-negative bacteria from clinical and environmental strains that present phenotypic resistance to this group. Material and Methods. 73 strains of Enterobacteriaceae and Aeromonas spp., from clinical and environmental origin, were selected for this study, and evaluated for antimicrobial susceptibility of quinolone and search of resistance genes in this same group and also for mutations in the gene encoding the enzyme DNA gyrase by PCR and sequencing. Results. Of the 73 strains previously selected to compose this study, 65 were used, due to the exclusion of similar clonal profiles. In these, genes qnrS1 (1.5 per cent ), qnrS2 (26.2 per cent ) qnrB1 (3.1 per cent ), qnrB19 (12.3 per cent ) qnrD1 (1.5 per cent ) aac(6')-Ib-cr (10.8 per cent ) oqxA (43.1 per cent ) and oqxB (41.5 per cent ) were observed, and two variants were named as qnrB-like (3.1 per cent ) and qnrB69-like (1.5 per cent ). The qnrA, qnrC and qepA genes were not identified. Mutations in DNA gyrase enzyme were observed in 97.9 per cent of the positive strains for at least one of the genes studied. It was possible to establish the association of aac(6')-Ib-cr with class 1 integron gene in four strains...

A Korean Nationwide Surveillance Study for Non-Typhoidal Salmonella Isolated in Humans and Food Animals from 2006 to 2008: Extended-Spectrum beta-Lactamase, Plasmid-Mediated AmpC beta-Lactamase, and Plasmid-Mediated Quinolone Resistance qnr Genes / 대한임상미생물학회지

BACKGROUND: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study. METHODS: National Institute of Health and National Veterinary Research and Quarantine Service collected NTS strains from 219 clinical and 293 non-clinical specimens from 2006 to 2008. The antimicrobial susceptibilities were determined using the Clinical and Laboratory Standards Institute disk diffusion test. ESBL, PABL, and qnr genotyping were performed using PCR and nucleotide sequencing. Pulsed-field gel electrophoresis was used for the molecular epidemiologic study. RESULTS: The resistance to ampicillin in clinical and non-clinical NTS was 49% and 18 to 47%, respectively. The resistance rates to trimethoprim-sulfamethoxazole in clinical and non-clinical NTS were 8% and 0 to 41%, respectively. The rates to extended-spectrum cephalosporin were 0 to 1%. One CTX-M-15-producing isolate and four CMY-2-producing isolates were detected. Notably, PFGE analysis showed four isolates carrying bla CMY-2, including one non-clinical strain had high clonality. Although the rate of ciprofloxacin resistance was very low, two qnrS1-carrying NTS strains were detected in non-clinical specimens. CONCLUSION: The resistance rates to ampicillin in both clinical and non-clinical NTS were high, while those to trimethoprim-sulfamethoxazole varied depending on the specimen. NTS strains harboring CTX-M-15-type ESBL or CMY-2-type PABL were detected even though the resistance rates to cephalosporins were very low. Four NTS strains carrying the blaCMY-2-gene implied zoonotic infection. Continuous effort to minimize transfer of resistance genes in NTS is necessary.

Identification of plasmid-mediated quinolone resistance genes qnrA1, qnrB1 and aac(6')-1b-cr in a multiple drug-resistant isolate of Klebsiella pneumoniae from Chennai. Indian Journal of Medical Microbiology. 2011 Jul-Sept; 29(3): 262-268.

Purpose: Resistance to fluoroquinolones, a commonly prescribed antimicrobial for Gram-negative and Gram-positive microorganisms, is of importance in therapy. The purpose of this study was to screen for the presence of Plasmid-Mediated Quinolone Resistance (PMQR) determinants in clinical isolates of Klebsiella pneumoniae. Materials and Methods: Extended-Spectrum Beta-Lactamase (ESBL) isolates of K. pneumoniae collected during October 2009 were screened by the antimicrobial susceptibility test. The plasmids from these isolates were analysed by specific Polymerase chain Reaction (PCR) for qnrA, qnrB and aac(6')-1b. The amplified products were sequenced to confirm the allele. Results: Our analysis showed that 61% out of the 23 ESBL K. pneumoniae isolates were resistant to ciprofloxacin and 56% to levofloxacin. The PMQR was demonstrated by transforming the plasmids from two isolates P12 and P13 into E. coli JM109. The PMQR gene qnrA was found in 16 isolates and qnrB in 11 isolates. The plasmid pKNMGR13 which conferred an minimum inhibitory concentration (MIC) of more than 240 ΅g/ml in sensitive E. coli was found to harbour the qnrA1 and qnrB1 allele. Furthermore, the gene aac(6')-1b-cr encoding a variant aminoglycoside 6'-N Acetyl transferase which confers resistance to fluoroquinolones was found in the same plasmid. Conclusions: Our report shows the prevalence of PMQR mediated by qnrA and qnrB in multidrug-resistant K. pneumoniae isolates from Chennai. A multidrug-resistant plasmid conferring high resistance to ciprofloxacin was found to harbour another PMQR gene, aac(6')-1b-cr mutant gene. This is the first report screening for PMQR in K. pneumoniae isolates from India.

Identification of plasmid-mediated quinolone resistance genes qnrA1, qnrB1 and aac(6')-1b-cr in a multiple drug-resistant isolate of Klebsiella pneumoniae from Chennai.

Purpose: Resistance to fluoroquinolones, a commonly prescribed antimicrobial for Gram-negative and Gram-positive microorganisms, is of importance in therapy. The purpose of this study was to screen for the presence of Plasmid-Mediated Quinolone Resistance (PMQR) determinants in clinical isolates of Klebsiella pneumoniae. Materials and Methods: Extended-Spectrum Beta-Lactamase (ESBL) isolates of K. pneumoniae collected during October 2009 were screened by the antimicrobial susceptibility test. The plasmids from these isolates were analysed by specific Polymerase chain Reaction (PCR) for qnrA, qnrB and aac(6')-1b. The amplified products were sequenced to confirm the allele. Results: Our analysis showed that 61% out of the 23 ESBL K. pneumoniae isolates were resistant to ciprofloxacin and 56% to levofloxacin. The PMQR was demonstrated by transforming the plasmids from two isolates P12 and P13 into E. coli JM109. The PMQR gene qnrA was found in 16 isolates and qnrB in 11 isolates. The plasmid pKNMGR13 which conferred an minimum inhibitory concentration (MIC) of more than 240 ΅g/ml in sensitive E. coli was found to harbour the qnrA1 and qnrB1 allele. Furthermore, the gene aac(6')-1b-cr encoding a variant aminoglycoside 6'-N Acetyl transferase which confers resistance to fluoroquinolones was found in the same plasmid. Conclusions: Our report shows the prevalence of PMQR mediated by qnrA and qnrB in multidrug-resistant K. pneumoniae isolates from Chennai. A multidrug-resistant plasmid conferring high resistance to ciprofloxacin was found to harbour another PMQR gene, aac(6')-1b-cr mutant gene. This is the first report screening for PMQR in K. pneumoniae isolates from India.