Study on the susceptibility genes that mediate the resistance of Helicobacter pylori to clarithromycin and levofloxacin based on comprehensive antibiotic research database comparison / 中华消化杂志

Objective:Taking clinical strains of Helicobacter pylori ( H. pylori) with different antimicrobial resistance as the research object, to explore the new genes related to the resistance of H. pylori to clarithromycin (CLA) and levofloxacin (LVX) based on whole-genome sequencing. Methods:From September 1st, 2016 to August 31st, 2019, 1 749 patients with upper gastrointestinal symptoms and positive 13C urea breath test who visited the Department of Gastroenterology and Hepatology, the University of Hong Kong-Shenzhen Hospital were enrolled. After gastric mucosal biopsy, H. pylori was isolated and cultured from gastric mucosa. Ninety H. pylori strains were successfully preserved. According to the results of in vitro drug sensitivity test, a total of 40 strains including 10 strains with single-drug resistance to CLA (CLA group), 10 strains with single-drug resistance to LVX (LVX group), 10 strains with dual-resistance to CLA and LVX (dual resistance group) and 10 strains sensitive to CLA, LVX, amoxicillin, furazolidone, tetracycline and metronidazole (all sensitive group) were screened out. By whole-genome sequencing and comparison to the comprehensive antibiotic research database (CARD), single nucleotide variations (SNV) and indels were analyzed, genes related to H. pylori resistance to CLA and LVX were screened out and the differences of new genes among 4 groups were analyzed. Independent sample t test, one-way analysis of variance, least significant difference method and chi-square test were used for statistical analysis. Results:Among the 4 groups there were no statistically significant differences in the number of SNV (74 952.00±8 755.21, 77 128.10±3 191.35, 78 639.90±601.23 and 77 474.60±2 421.05) and Indels (2 582.20±265.45, 2 653.60±108.37, 2 667.10±43.82 and 2 641.10±80.25) (all P>0.05). Compared to CARD, a total of 223 drug resistance-related genes were detected, of which 19 genes related to CLA mono-resistance in CLA group, 24 genes related to LVX mono-resistance in LVX group, 16 genes related to CLA mono-resistance, 14 genes related to LVX mono-resistance, and 12 dual resistance-related genes in dual resistance group, and 11 genes related to CLA mono-resistance, 17 genes related to LVX mono-resistance, and 13 dual resistance-related genes in all sensitive group. Among the genes related to CLA mono-resistance, the detection rates of erythromycin esterase gene ( ere)B in CLA group, LVX group, dual resistance group and all sensitive group were 0/10, 0/10, 3/10, 0/10, respectively, and the difference was statistically significant( χ2=5.79, P=0.049). The detection rate of erythromycin ribosomal methylase gene ( erm) family in CLA group and dual resistance group was higher than that in LVX group and all sensitive group (45.0%, 9/20 vs. 10.0%, 2/20), and the difference was statistically significant ( χ2=6.14, P=0.013). The detection rates of free methionine-(R)-sulfoxide reductase gene ( msrC) in CLA group, LVX group, dual resistance group and all sensitive group were 10/10, 7/10, 6/10, 4/10, respectively, and the difference was statistically significant ( χ2=8.97, P=0.030). Among the genes related to LVX mono-resistance, the detection rate of quinolone resistance pentapeptide repeat protein gene ( qnr) family in LVX group and dual resistance group was higher than that in CLA group and all sensitive group (60.0%, 12/20 vs. 25.0%, 5/20), and the difference was statistically significant ( χ2=5.01, P=0.025). The detection rates of qnrB4 in CLA group, LVX group, dual resistance group and all sensitive group were 1/10, 3/10, 7/10, 1/10, respectively, and the difference was statistically significant ( χ2=10.17, P=0.010). The number of efflux transporter genes related to CLA mono-resistance in 4 groups were less than those of LVX mono-resistance and dual drug resistance (11 vs. 29 and 11 vs. 23), and the differences were statistically significant ( χ2=11.87, 5.80; P=0.001, 0.016). The detected numbers of LVX resistance-related efflux transport genes in CLA group, LVX group, dual resistance group and all sensitive group were 28, 40, 24 and 27, respectively, and the difference was statistically significant ( χ2=10.26, P=0.016). Conclusions:Erm family and msrC may be important genes that mediate the resistance of H. pylori to CLA, and qnr family is related to mediating the resistance of H. pylori to LVX. Efflux transport genes may play a synergistic role in the process of drug efflux, and are more likely to mediate H. pylori resistance to LVX.

Approach to enhance antibiotics efficiency towards uropathogenic bacteria

@#Aims: Urinary tract infection (UTI) is a common infection caused by many virulent bacteria. Multidrug resistance (MDR) by bacteria represents a major therapeutic challenge worldwide. MRD bacteria have different mechanisms to avoid antibiotics; one of them is horizontal gene transfer. Such genes, encoding antimicrobial resistance, are easily transferred from one bacterium to another. Magnesium and calcium chloride (MgCl2 and CaCl2) have an effect on the permeability of bacterial cell membrane. We aimed these chemical materials could increase the antibiotics efficiency on multidrug resistance bacteria. 250 UTI specimens were collected to isolate multidrug resistant bacteria. Depending on antibiotics resistance, we selected three species of virulent bacteria: Escherichia coli, Staphylococcus aureus and Proteus mirabilis. Then, we tested the effect of MgCl2 and CaCl2 on their antibiotics resistance. Methodology and results: The results showed that percentage of E. coli in UTI infection is the highest (45%), while Enterococcus faecalis is the lowest (3%). The effect of MgCl2 and CaCl2 on bacterial antibiotics resistance has been tested using different types of antibiotics. The findings showed that MgCl2 has significant effect to aid antibiotics against bacteria. In particular, nalidixic acid has shown more efficiency against E. coli and S. aureus but not P. mirabilis. Using different concentrations of CaCl2 increased the efficiency of gentamycin, amoxicillin and trimethoprim against S. aureus, while has increased the efficiency of ampicillin and nalidixic acid against E. coli. However, CaCl2 has no effect on the efficiency of antibiotics against P. mirabilis. In addition, MgCl2, and CaCl2 had no toxic effects in both T24 and 5637 urinary bladder cell lines. Finally, plasmids were isolated from these species to detect any antimicrobial resistance gene such as qnr-A. Conclusion, significance and impact of study: MDR distribution in the worldwide was increased, we highly recommend the avoidance of the random antibiotic usages. The salts CaCl2 and/or MgCl2 can be used at specific concentration to enhance the antibiotics permeability and therefore to decrease the antibiotic resistance.

Prevalence of qnr Genes among Multidrug Resistance Staphylococcus aureus from Clinical Isolates

Objectives: Staphylococcus aureus(S.aureus) is regarded as an important aetiological agent of various human infections. Fluoroquinolonesare routinely used in the chemotherapeutic management of these infections; nonetheless, in recent years, a growing rate of resistance to these drugs has been reported worldwide. The aims of this study were to isolate and discover the prevalence of plasmid-mediated (qnrA, qnrB, and qnrS) genes among the quinolone-resistant clinical S. aureusisolates in Bayelsa State, Nigeria.Methods: A total of 25 (31.25%) clinical isolates of S. aureuswere collected from hospitalized patients. The bacterial isolates were identified through standard laboratory protocols and further confirmed using the API Staph system (bioMérieux, France) test strips. The antimicrobial susceptibility and minimum inhibitory concentration (MIC) were determined by the standard disk diffusionand serial dilutions methods respectively. Polymerase chain reaction (PCR) was used for detecting qnrA, qnrB, and qnrSgenes.Results: Of the 25 S. aureus isolates, 19(76.00%) were resistant to ampicillin-cloxacillin, while 14 (56.00%) each were resistantto norfloxacin and Amoxicillin, 13 (52.00%) each to gentamicin and erythromycin, 11 (44.00%) were resistant to streptomycin, rifampicin and ciprofloxacin, respectively. The resistance pattern among the isolates to chloramphenicol and levofloxacin were 10 (40.00%) and 7 (28.00%) respectively. All the eleven ciprofloxacin resistant were high-level (1000 μg/mL) resistance isolates and only one (9.00%) of these isolates was positive for the qnrBgene.Conclusion: The study results were indicative of the presence of low frequency of qnrgenes among the clinical isolates of S. aureusin Yenagoa, indicating that other mechanisms are employed in resisting to these fluoroquinolones. This, however, emphasizes the need for establishing discreet policies associated with infection-control measures in hospital settings

Antimicrobial resistance, virulence & plasmid profiles among clinical isolates of Shigella serogroups

Background & objectives: Bacillary dysentery caused by Shigella spp. remains an important cause of the crisis in low-income countries. It has been observed that Shigella species have become increasingly resistant to most widely used antimicrobials. In this study, the antimicrobial resistance, virulence and plasmid profile of clinical isolates of Shigella species were determined. Methods: Sixty clinical Shigella isolates were subjected to whole-genome sequencing using Ion Torrent platform and the genome sequences were analyzed for the presence of acquired resistance genes, virulence genes and plasmids using web-based software tools. Results: Genome analysis revealed more resistance genes in Shigella flexneri than in other serogroups. Among ?-lactamases, blaOXA-1was predominantly seen followed by the blaTEM-1B and blaEC genes. For quinolone resistance, the qnr S gene was widely seen. Novel mutations in gyr B, par C and par E genes were observed. Cephalosporins resistance gene, blaCTX-M-15 was identified and plasmid-mediated AmpC ?-lactamases genes were found among the isolates. Further, a co-trimoxazole resistance gene was identified in most of the isolates studied. Virulence genes such as ipaD, ipaH, virF, senB, iha, capU, lpfA, sigA, pic, sepA, celb and gad were identified. Plasmid analysis revealed that the IncFII was the most commonly seen plasmid type in the isolates. Interpretation & conclusions: The presence of quinolone and cephalosporin resistance genes in Shigella serogroups has serious implications for the further spread of this resistance to other enteric pathogens or commensal organisms. This suggests the need for continuous surveillance to understand the epidemiology of the resistance.

Genes qnr en Enterobacteriaceae aisladas en un hospital de Venezuela / qnr genes in Enterobacteriaceae isolated from at a hospital in Venezuela

Resumen Introducción: La resistencia de enterobacterias a quinolonas se ha difundido por el mundo, fenómeno presente también en Venezuela. El mecanismo de esta resistencia pudiera estar mediado por genes incluidos en el cromosoma bacteriano o transmitirse en el interior de plásmidos. Objetivo: Evaluar la resistencia a quino-lonas, codificada por genes qnr, presentes en cepas de enterobacterias, aisladas en el Hospital Universitario de Cumaná, Venezuela. Métodos: A las cepas obtenidas se les realizaron pruebas de susceptibilidad antimicrobiana a quinolonas, β-lactámicos y aminoglucósidos. La presencia del gen qnr se determinó por RPC. Las enterobacterias portadoras del gen qnr fueron sometidas al proceso de conjugación bacteriana para comprobar su capacidad de transferencia. A las transconjugantes obtenidas se les realizó pruebas de susceptibilidad antimicrobiana y RPC para comprobar la transferencia de los genes. Resultados: Se encontraron elevados porcentajes de resistencia antimicrobiana a quinolonas y betalactámicos. El 33,6% de las cepas eran portadoras del gen qnrB, y 0,9% del gen qnrA. Se obtuvieron 23 cepas transconjugantes; de éstas, 20 portaban el gen qnrB, no se observó la presencia de qnrA. Discusión: En conclusión, el elevado porcentaje de genes qnr encontrado en las enterobacterias aisladas, y comprobada la presencia de éstos en plásmidos transferibles, complica la aplicación de tratamientos basados en quinolonas y fluoroquinolonas, por lo que es recomendable el uso racional de estos antimicrobianos, y proponer la rotación de la terapia antimicrobiana, a fin de evitar la selección de cepas resistentes.

Background: Enterobacteria resistant to quinolones is increasing worldwide, including Venezuela. The mechanism for this resistance could be due to genes included in the chromosome or in transmissible plasmids. Aim: To evaluate the resistance to quinolones, coded by qnr genes present in enterobacteria species, isolated in the University Hospital of Cumana, Venezuela. Methods: Antimicrobial susceptibility tests to quinolones, beta-lactams and aminoglycosides were carried out to all the isolates. The presence of qnr genes were determined by PCR. The isolates carrying the qnr genes were used for bacterial conjugation tests to determine the presence of transferable plasmids. Antimicrobial susceptibility tests and PCR were carried out in the transconjugants to verify the transfer of the genes. Results: High levels of antimicrobial resistance to quinolones and beta-lactams were found among the isolates. We found that 33.6% of the isolates carry the qnrB gene and 0.9% qnr A gene. Of the 23 transconjugants, 20 showed to have qnrB gene, but none qnrA. Discussion: We concluded that the high frequency of qnr genes found in the enterobacteria isolates and their presence on transferable plasmids, complicate the use of quinolones for the treatment of bacterial infections, thus, a treatment plan should be designed with the rational use and the rotation of different types of antimicrobials, in order to avoid the selection of increasingly resistant strains.

Quinolone susceptibility and genetic characterization of Salmonella enterica subsp. enterica isolated from pet turtles / 한국실험동물학회지

Turtle-borne Salmonella enterica owns significance as a leading cause in human salmonellosis. The current study aimed to determine the quinolone susceptibility and the genetic characteristics of 21 strains of S. enterica subsp. enterica isolated from pet turtles. Susceptibility of four antimicrobials including nalidixic acid, ciprofloxacin, ofloxacin, and levofloxacin was examined in disk diffusion and MIC tests where the majority of the isolates were susceptible to all tested quinolones. In genetic characterization, none of the isolates were positive for qnr or aac(6')-Ib genes and no any target site mutations could be detected in gyrA, gyrB, and parC quinolone resistance determining regions (QRDR). In addition, neighbor-joining phylogenetic tree derived using gyrA gene sequences exhibited two distinct clads comprising; first, current study isolates, and second, quinolone-resistant isolates of human and animal origin. All results suggest that studied strains of S. enterica subsp. enterica isolated from pet turtles are susceptible to quinolones and genetically more conserved with regards to gyrA gene region.

Widespread distribution of CTX-M and plasmid-mediated AmpC β-lactamases in Escherichia coli from Brazilian chicken meat

The dissemination of plasmid-mediated antimicrobial resistance genes may pose a substantial public health risk. In the present work, the occurrences of blaCTX-M and plasmid-mediated ampC and qnr genes were investigated in Escherichia coli from 16 chicken carcasses produced by four commercial brands in Brazil. Of the brands tested, three were exporters, including one of organic chicken. Our study assessed 136 E. coli isolates that were grouped into 77 distinct biotypes defined by their origin, resistance profiling, the presence of β-lactamase and plasmid-mediated quinolone resistance genes and enterobacterial repetitive intergenic consensus-polimerase chain reaction typing. The blaCTX-M-15, blaCTX-M-2 and blaCTX-M-8 genes were detected in one, 17 and eight different biotypes, respectively (45 isolates). Twenty-one biotypes (46 isolates) harboured blaCMY-2. Additionally, blaCMY-2 was identified in isolates that also carried either blaCTX-M-2 or blaCTX-M-8. The qnrB and/or qnrS genes occurred in isolates carrying each of the four types of β-lactamase determinants detected and also in oxyimino-cephalosporin-susceptible strains. Plasmid-mediated extended-spectrum β-lactamase (ESBL) and AmpC determinants were identified in carcasses from the four brands tested. Notably, this is the first description of blaCTX-M-15 genes in meat or food-producing animals from South America. The blaCTX-M-8, blaCTX-M-15 and blaCMY-2 genes were transferable in conjugation experiments. The findings of the present study indicate that plasmid-mediated ESBL and AmpC-encoding genes are widely distributed in Brazilian chicken meat.

The dissemination mode of drug-resistant genes in Enterobacter cloacae.

Background: Enterobacter cloacae (E. cloacae) infection has the highest mortality rate among Enterobacter infections. This study aimed to determine the prevalence and the transmission route of the class I integron, qnr genes, and CTX-M ESBLs genes in clinical isolates and to analyse the association between the prevalence of MDR genes and the antibiotic resistance of E. cloacae. Materials and Methods: The antibiotic susceptibility was tested the agar dilution method. The class I integron, qnr genes, and CTX-M ESBLs genes were detected by polymerase chain reaction (PCR). The prevalence data were analysed with the Chi-square test. Results: In the 100 clinical isolates, the class I integron-positive rate was 65%, with 12% on chromosome, 15% on plasmids and 38% on both. The positive rate of qnr genes was 37% with plasmid location. The positive rates for qnrA, qnrB and qnrS were 6%, 23% and 8%, respectively. The CTX-M ESBLs-positive rate was 34%. For CTX-M-1 ESBLs, 15% were on chromosome, 6% on plasmids and 4% on both; for CTX-M-9 ESBLs, 1% was on chromosome and 7% on plasmid; for CTX-M-25 ESBLs, 3% were on chromosome and 1% on plasmid. Conclusion: Antibiotic resistance genes may be horizontally and vertically disseminated among E. cloacae, which helps multidrug-resistant (MDR) strains of E. cloacae to be successful nosocomial agents.

Investigation of plasmid-mediated quinolone resistance in Pseudomonas aeruginosa clinical isolates.

Aims: To investigate plasmid‑mediated quinolone resistance in clinical isolates of Pseudomonas aeruginosa with the polymerase chain reaction (PCR). The plasmid‑mediated quinolone resistance genes have been identified in many bacteria within the Enterobactericeae family, they have not been detected in P. aeruginosa isolates. Subjects and Methods: Identification of the isolates and testing of antibiotic susceptibility was performed in Vitek2 Compact (Biomeriux, France) and Phoinex (BD, USA) automated systems. Screening for the qnrA, qnrB, qnrS, qnrC, aac (6′)‑Ib‑cr and qepA genes was carried out by PCR amplification and aac (6′)‑Ib‑cr DNA sequencing. Results: The qnr and the qepA genes were not detected in any of P. aeruginosa isolates. The aac (6’)‑Ib gene was detected in six of the isolates and positive isolates for aac (6’)‑Ib were sequenced for detection of the aac (6’)‑Ib‑cr variant but aac (6’)‑Ib‑cr was not detected in any isolates. Conclusions: Plasmid‑mediated quinolone resistance genes have so far not been identified in P. aeruginosa isolates. However, qnrB have detected in P. florescens and P. putida isolates. This is the first study conducted on the qnrA, qnrB, qnrS and qnrC genes as well as the qepA and aac (6’)‑Ib‑cr genes in P. aeruginosa clinical isolates.

Determinants of quinolone resistance in Escherichia coli causing community-acquired urinary tract infection in Bejaia, Algeria

OBJECTIVE@#To investigate the mechanisms of quinolone resistance and the association with other resistance markers among Esherichia coli (E. coli) strains isolated from outpatient with urinary tract infection in north of Algeria.@*METHODS@#A total of 30 nalidixic acid-resistant E. coli isolates from outpatient with urinary tract infections from January 2010 to April 2011 in north of Algeria (Bejaia) were studied. Antimicrobial susceptibility was determined by disc diffusion assay, minimal inhibitory concentrations (MIC) of quinolone were determined by microdilution. Mutations in the Quinolone Resistance-Determining Region (QRDR) of gyrA and parC genes and screening for qnr (A, B and S) and bla genes were done by PCR and DNA sequencing.@*RESULTS@#Most of the E. coli isolates (56.66%) were shown to carry mutations in gyrA and parC (gyrA: Ser83Leu + Asp87Asn and parC:Ser80Ile). While, 16.66% had only an alteration in gyrA: Ser83Leu. One isolate produced qnrB-like and two qnrS-like. Four isolates were CTX-M-15 producers associated with TEM-1 producing in one case. Co-expression of blaCTX-M-15 and qnrB was determined in one E. coli isolate.@*CONCLUSIONS@#Our findings suggested the community emergence of gyrA and parC alterations and Qnr determinants that contributed to the development and spread of fluoroquinolone resistance in Algerian E. coli isolates.

Smqnr VARIANTS IN CLINICAL ISOLATES OF Stenotrophomonas maltophilia IN BRAZIL / Variantes de Smqnr de isolados clínicos de Stenotrophomonas maltophilia no Brasil

SUMMARY Stenotrophomonas maltophilia contains a novel chromosomally-encoded qnr gene named Smqnr that contributes to low intrinsic resistance to quinolone. We described Smqnr in 13 clinical isolates of S. maltophilia from two Brazilian hospitals, over a 2-year period. The strains were identified by API 20 NE (bioMérieux, France). Susceptibility by microdilution method to trimetroprim/sulfamethoxazole, ciprofloxacin, levofloxacin, minocycline, ceftazidime, chloramphenicol and ticarcillin/clavulanate was performed according to CLSI. PCR detection of Smqnr gene was carried out. The sequence of Smqnr was compared with those deposited in GenBank. Pulsed-field gel electrophoresis (PFGE) of all strains was performed. Thirteen Smqnr positives isolates were sequenced and three novel variants of Smqnr were identified. All 13 Smqnr isolates had distinguishable patterns by PFGE. This is the first report of Smqnr in S. maltophilia isolated in Brazil. .

RESUMO S. maltophilia contem um novo gene qnr cromossômico denominado Smqnr que contribui para baixa resistência intrínseca a quinolonas. Descrevemos Smqnr em 13 isolados clínicos de S. maltophilia de dois hospitais brasileiros, ao longo do período de dois anos. Os isolados foram identificados pela API 20 NE (bioMérieux, França). Susceptibilidade pelo método de microdiluição dos seguintes antibióticos trimetroprim/sulfametoxazol, ciprofloxacina, levofloxacina, minociclina, ceftazidima, cloranfenicol e ticarcilina/clavulanato foi realizada segundo o CLSI. Detecção do gene de Smqnr foi realizada por PCR. A sequência de Smqnr foi comparada com aquelas depositadas no GenBank. Foi realizada eletroforese em gel de campo pulsado (PFGE) de todos os isolados. Treze isolados contendo Smqnr foram sequenciados e identificados três variantes do gene Smqnr. Todos os 13 isolados de Smqnr apresentaram diferentes padrões por PFGE. Este é o primeiro relato de Smqnr em isolados de S. maltophilia no Brasil. .

Plasmid-mediated fluoroquinolone-resistance qnrA and qnrB genes among Escherichia coli from cattle in Ado-Ekiti, Nigeria / Genes qnrA y qnrB de la resistencia a la fluoroquinolona mediada por plásmidos entre las bacterias Escherichia coli del ganado en Ado-Ekiti, Nigeria

OBJECTIVE: This is to investigate the implication of fluoroquinolone usage in veterinary practice and the food chain system. SUBJECTS AND METHODS: Five hundred isolates of commensal E coli were recovered from the faeces of apparently healthy cattle in Ado-Ekiti, Nigeria. The susceptibility of the bacteria was tested using standard laboratory procedures. Polymerase chain reaction (PCR) was carried out to detect the presence of qnrA and qnrB genes, which were selected on the basis of their fluoroquinolone-resistant patterns. RESULTS: The agar disc diffusion technique revealed that the representative isolates showed multiple fluoroquinolone-resistance and this formed the basis for their selection for PCR amplification. The PCR revealed that ten of the 17 quinolone-resistant representative isolates showed distinct bands which are specific for the qnrB gene; in addition, only one strain of the 20 representative isolates of commensal E coli carried plasmids on which the qnrA gene was detected. CONCLUSION: This study has confirmed that plasmid-mediated quinolone resistance is a possible mechanism among the fluoroquinolone-resistant commensal E coli isolated from faeces of apparently healthy cattle in the study location.

OBJETIVO: El propósito de este trabajo es investigar las implicaciones del uso de las fluoroquinolonas en la práctica veterinaria y el sistema de la cadena alimentaría. SUJETOS Y MÉTODOS: Quinientos aislados de E Coli comensales fueron obtenidos de las heces de ganado ostensiblemente sano en Ado-Ekiti, Nigeria. Se sometió a prueba la susceptibilidad de las bacterias usando los procedimientos de laboratorio normales. Se llevó a cabo una reacción en cadena de la polimerasa (RCP) a fin de detectar la presencia de genes qnrA y qnrB, los cuales fueron seleccionados sobre la base de sus patrones de resistencia a la fluoroquinolona. RESULTADOS: La técnica de difusión con disco en agar reveló que los aislados representativos mostraban resistencia múltiple a la fluoroquinolona, lo cual constituyó la base para su selección a fin de amplificar la RCP. La RCP reveló que 10 de cada 17 asilados representativos de la resistencia a la quinolona, mostraban bandas claramente específicas del gen qnrB. Además, sólo una cepa de 20 aislados representativos de las E Coli portaba plásmidos en los que el gen qnrA fue detectado. CONCLUSIÓN: Este estudio confirmó que la resistencia a la quinolona mediada por plásmidos, es un posible mecanismo entre las E Coli comensales aisladas de la haces del ganado sano en la localidad del estudio.

Prevalence of Plasmid-mediated Quinolone Resistance and Its Association with Extended-spectrum Beta-lactamase and AmpC Beta-lactamase in Enterobacteriaceae / 대한진단검사의학회지

BACKGROUND: We investigated the prevalence of plasmid-mediated quinolone resistance and its association with extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase in Enterobacteriaceae. METHODS: A total of 347 non-duplicated isolates of Enterobacteriaceae were collected between August and October 2006 from 2 hospitals. Qnr determinant screening was conducted using PCR amplification, and all positive results were confirmed by direct sequencing. Qnr-positive strains were determined on the basis of the presence of ESBL and AmpC beta-lactamase genes. RESULTS: The qnr gene was detected in 47 of 347 clinical Enterobacteriaceae isolates. Among the 47 qnr-positive strains, Klebsiella pneumoniae (N=29) was the most common, followed by Escherichia coli (N=6), Enterobacter cloacae (N=6), Citrobacter freundii (N=5), and Enterobacter aerogenes (N=1). These isolates were identified as qnrA1 (N=6), 8 qnrB subtypes (N=40), and qnrS1 (N=1). At least 1 ESBL was detected in 38 of the 47 qnr-positive strains. Qnr-positive strains also showed high positive rates of ESBL or AmpC beta-lactamase, such as TEM, SHV, CTX-M, and DHA. DHA-1 was detected in 23 of 47 qnr-positive strains, and this was co-produced with 1 qnrA1 and 22 qnrB4. Strains harboring MIR-1T and CMY were also detected among the qnr-positive strains. Antimicrobial-resistance rates of qnr-positive strains to ciprofloxacin, levofloxacin, norfloxacin, nalidixic acid, and moxifloxacin were 51.1%, 46.8%, 46.8%, 74.5%, and 53.2%, respectively. CONCLUSIONS: The qnr genes were highly prevalent in Enterobacteriaceae, primarily the qnrB subtypes. They were closely associated with EBSL and AmpC beta-lactamase.

Prevalence of qnr and aac(6')-Ⅰ b-cr genes in water-borne environmental bacteria and clinical isolates of Citrobacter freundii in China / 中华微生物学和免疫学杂志

Objective To investigate the prevalence of qnr and aac(6')-Ⅰ b-cr genes in water-borne environmental bacteria and clinical isolates of Citrobacter freundii, and the subtypes of qnr gene. Methods Environmental bacteria were isolated from surface water samples obtained from 10 distinct loca-tions in Hangzhou city, and clinical isolates of C. Freundii were isolated from several hospitals of 4 cities in China. Minimum inhibitory concentrations (MICa) of ciprofloxacin, levofloxacin and nalidixic acid were de-termined by agar dilution method, qnrA, qnrB, qnrS and aac(6')-Ⅰ b-cr genes were screened by PCR, and the genotypes were analyzed by DNA sequencing. Results Seventy-eight gram negative bacilli (including 33 Enterobacteriaceae, 21 Aeromonas spp., 10 Acinetobacter spp., 10 Pseudomonas app., 2 Alcaligenes app. , and 2 Plesiomonas app.) were isolated from water samples. Among these isolates, 8 of 10 C. Freundii were positive for qnrB gene. qnrS1 and aac (6')-Ⅰ b-cr were detected in two distinct Escherichia coil, and qnrS2 was detected in a Aeromonas punctata qnr and aac(6')-Ⅰ b-cr genes were present in 75 (72.8%) and 12 (11.6%) of 103 clinical isolates of C. Freundii, respectively. Three (2.9%) C. Freundii isolates were positive for qnrA1 gene, 65 (63.1%) qnrB, 1 (1.0%) qnrS2, 5 (4.8%) were positive for both qnrA1 and qnrB, and 1 was positive for both qnrS1 and qnrB. Within the subtypes of qnrB gene, qnrB9 predominated, followed by qnrB8 and qnrB6. Conclusion It was the first isolate of Aeromonas spp. Harboring qnrS2 gene outside Europe. The prevalence of qnrB in water-borne environmental and clinical isolates of C.freundii was particularly high and qnrB9, qnrB8 and qnrB6 were the most common subtypes, aac(6')-Ⅰ b-cr gene widely spread in clinical isolates of C. Freundii.

Plasmid-mediated quinolone resistance in Escherichia coli strains isolated from food animals / 中华微生物学和免疫学杂志

Objective To study on plasmid-mediated quinolone-resistant in Escherichia coli strains isolated from fecal samples of chicken and swine from the nine farms around our country.Methods Antimi-crobial susceptibility testing was carried out by broth microdilution testing,gyrA,gyrB,parC,qnr and aac (6')- Ⅰ b-cr were examined by PCR,and the products were sequenced.Conjugation experiment was carried out to proved that the plasmid-mediated quinolone resistance was transferable.Results In the total 818 animal isolates,qnr and aac genes were detected in 38 (4.6%) and 75 (9.2%) strains.The qnrA,qnrB,and qnrS genes were detected in 1 (0.1%),9 (1.1%) and 28 (3.4%) of the isolates.All isolates were negative for qnrC,qnrD genes.Conclusion There is a close relationship between high level quinolone resistance and plasmid-mediated quinolone resistance.The results of the current study highlight food-producing animals as a potential reservoir of antimicrobial-resistant bacteria and clinically important resistance genes.More attention should be paid to the surveillance of such strains.

Molecular Characteristics of Extended Spectrum beta-Lactamases in Escherichia coli and Klebsiella pneumoniae and the Prevalence of qnr in Extended Spectrum beta-Lactamase Isolates in a Tertiary Care Hospital in Korea

PURPOSE: Extended spectrum beta-lactamases (ESBLs) are cephalosporinases that confer resistance to a wide variety of oxyimino cephalosporins and create serious therapeutic problems. In addition, the quinolone resistance qnr genes are becoming increasingly prevalent in clinical isolates, some of which also produce ESBL. This study was designed to evaluate the occurrence and genotypic distribution of ESBL producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) as well as the prevalence and distribution of qnr genes in ESBL-producing isolates in a tertiary care hospital in Korea. MATERIALS AND METHODS: We tested a total of 111 ESBL-producing isolates of E. coli and K. pneumoniae, which were collected at Kyung Hee Medical Center from November 2006 to June 2008. ESBL production was determined by the Clinical and Laboratory Standards Institute (CLSI) ESBL confirmatory test. The cefotaxime and ceftazidime resistance of the ESBL-producers were transferred to azide-resistant E. coli J53 by conjugation. The presence and identity of ESBL and qnr genes were determined by polymerase chain reaction (PCR) and nucleotide sequencing. RESULTS: The prevalence of ESBLs was 17.7% (297/1,680) of E. coli and 26.5% (240/904) of K. pneumoniae in our hospital during the study periods. Of the 111 collected isolates, 69 isolates were E. coli and 42 isolates were K. pneumoniae. The most prevalent ESBL genotype was CTX-M15. Among the ESBL-producing isolates, 4 E. coli (5.8%) and 17 K. pneumoniae (40.5%) contained qnr genes. qnrB4 was the most frequent type in both E. coli and K. pneumoniae. CONCLUSION: CTX-M15 was the most frequently encountered ESBL. In addition, a high prevalence of qnr genes among ESBL-producing K. pneumoniae was identified in this study.

Prevalence and Characterization of Plasmid-Medicated Quinolone Resistance Genes among Clinical Isolates of Extended-Spectrum Cephalosporin Resistant Enterobacter cloacae

BACKGROUND: Extended-spectrum cephalosporins (ESCs)-resistant Enterobacter cloacae is one of the pathogens of nosocomial infection the incidence of which is on the rise. Moreover, plasmid-mediated quinolone resistance genes (PMQR genes) that reduce quinolone sensitivity have been shown to be widely distributed among clinical isolates of Enterobacteriaceae. This study was carried out to observe the distribution of PMQR genes in clinical isolates of E. cloacae resistant to ESCs. MATERIALS AND METHODS: Fourty-three ESCs-resistant E. cloacae strains from the blood collected during the span of 7 years, from 1994 to 2001, at Seoul National University Children's Hospital (SNUCH) were included in this study. Isoelectric focusing and enzyme specific PCR were performed to characterize beta-lactamase. The presence of qnrA, qnrB, qnrC, qnrS, qepA, and aac(6')-Ib-cr was determined by PCR, restriction enzyme analyses of PCR products, and DNA sequencing. Minimal inhibitory concentration (MIC) of several quinolones was measured by agar dilution method. RESULTS: The PMQR genes were detected in 9 (21%) of 43 ESCs-resistant E. cloacae isolates. Among them, five isolates were positive for qnrB2, and each two isolates harbored qnrB4 or qnrB5, respectively. qnrA, qnrC, qnrS or qepA was not identified. aac(6')-Ib was detected in 27 isolates, but aac(6')-Ib-cr was not found. Among the 9 qnrB-positive isolates, 5 produced SHV-12, 3 were derepressed mutants, and 1 produced pI 7.5 beta-lactamase. MIC ranges and percent resistances of nalidixic acid, ofloxacin, levofloxacin, and moxifloxacin for the PMQR genes-positive isolates were higher than PMQR genes-negative isolates. CONCLUSION: In this study, ESCs-resistant E. cloacae showed a high prevalence of PMQR genes, and qnrB was the only PMQR gene identified.

Prevalence and Characterization of Plasmid-Medicated Quinolone Resistance Genes among Clinical Isolates of Extended-Spectrum Cephalosporin Resistant Enterobacter cloacae

BACKGROUND: Extended-spectrum cephalosporins (ESCs)-resistant Enterobacter cloacae is one of the pathogens of nosocomial infection the incidence of which is on the rise. Moreover, plasmid-mediated quinolone resistance genes (PMQR genes) that reduce quinolone sensitivity have been shown to be widely distributed among clinical isolates of Enterobacteriaceae. This study was carried out to observe the distribution of PMQR genes in clinical isolates of E. cloacae resistant to ESCs. MATERIALS AND METHODS: Fourty-three ESCs-resistant E. cloacae strains from the blood collected during the span of 7 years, from 1994 to 2001, at Seoul National University Children's Hospital (SNUCH) were included in this study. Isoelectric focusing and enzyme specific PCR were performed to characterize beta-lactamase. The presence of qnrA, qnrB, qnrC, qnrS, qepA, and aac(6')-Ib-cr was determined by PCR, restriction enzyme analyses of PCR products, and DNA sequencing. Minimal inhibitory concentration (MIC) of several quinolones was measured by agar dilution method. RESULTS: The PMQR genes were detected in 9 (21%) of 43 ESCs-resistant E. cloacae isolates. Among them, five isolates were positive for qnrB2, and each two isolates harbored qnrB4 or qnrB5, respectively. qnrA, qnrC, qnrS or qepA was not identified. aac(6')-Ib was detected in 27 isolates, but aac(6')-Ib-cr was not found. Among the 9 qnrB-positive isolates, 5 produced SHV-12, 3 were derepressed mutants, and 1 produced pI 7.5 beta-lactamase. MIC ranges and percent resistances of nalidixic acid, ofloxacin, levofloxacin, and moxifloxacin for the PMQR genes-positive isolates were higher than PMQR genes-negative isolates. CONCLUSION: In this study, ESCs-resistant E. cloacae showed a high prevalence of PMQR genes, and qnrB was the only PMQR gene identified.

The examination of qnr and aac(6')- Ⅰ b-cr genes of clinical isolates resistant to ciprofloxacin in Enterobacteriaceae / 中华微生物学和免疫学杂志

Objective To investigate the distribution of qnr and aac(6')- Ⅰ b-cr genes of clinical isolates resistant to ciprofloxacin in Enterobacteriaceae in Wenzhou. Methods From August 2005 to April 2008 a total of 461 clinical isolates resistant to ciprofloxacin in Enterobacteriaceae (370 isolates of Escherichia coli, 39 isolates of Enterobacter cloacae and 52 isolates of Klebsiella) were collected from the First Affiliated Hospital of Wenzhou Medical College. qnr and aac(6')- Ⅰ b genes were detected by PCR for all the clinical isolates, DNA sequencing was used for qnr and aac(6')-Ⅰ b-cr identification and conjugation experiment was proved to find ways of transmission of antimicrobial resistance. Results Fifteen qnr-positive isolates were detected among 461 Enterobacteriaceae isolates, including 5 qnrA-positive isolates (4 Enterobacter cloacae isolates and 1 Klebsiella ornithinolytica isolate), 4 qnrB-positive isolates( 2 Klebsiclla paeunoniae isolates and 2 Escherichia coli isolates), 6 qnrS-positive isolates(2 Klebsiella pneunoniae isolates and 4 Escherichia coli isolates). Fifty-two among 461 Enterobacteriaceae isolates harbored aac(6')- Ⅰ b-cr gene, including 42 Escherichia coil isolates, 4 Enterobacter cloacae isolates and 6 Klebsiella isolates. DNA sequencing for 15 qnr-positive isolates found they harbored aac(6')- Ⅰ b-cr gene simultaneously. Fifteen qnr-positive isolates were susceptible to imipenem but resistant to some other drugs. Conjugation experiments were successfully carried out in 7 of 15 isolates harbored qnr and aac(6')-Ⅰ b-cr genes, and their resistance to quinolones and aminoglycosides was partly transmitted to the recipient isolates. Conclusion The qnr genes are few in clinical isolates resistant to ciprofloxaein in Enterubacteriaceae in Wenzhou, however the aac(6')- Ⅰ b-cr gene is popular.