Plasmid copy number and qnr gene expression in selection of fluoroquinolone-resistant Escherichia coli. - Related Documents




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298301.0000Plasmid copy number and qnr gene expression in selection of fluoroquinolone-resistant Escherichia coli. Fluoroquinolone resistance in Enterobacteriales is developed by chromosomal and plasmid-mediated mechanisms. Plasmids play an important role in dissemination of resistant genes and they carry genes that protect bacteria in different stress-induced situations. In this study, we studied Escherichia coli strains, each carried one plasmid-mediated quinolone resistance determinant namely, qnrA1, qnrB1, qnrC1, and qnrD1. We exposed 0.5 McFarland density of each strain to 0.5 mg/L ciprofloxacin from the period of 30, 60, 90, and 120 min over 24 h. All treated strains were further exposed to a constantly increasing 1, 2, 4, and 8 mg/L ciprofloxacin solution through 24, 48, and 120 h. In given timepoints, RNA was extracted from all treated strains. Expression of qnrA1, qnrB1, qnrC1, and qnrD1 was investigated by quantitative PCR. Mutations in gyrA and parC genes were analyzed by PCR and nucleic acid sequencing. In this study, during 0.5 mg/L ciprofloxacin exposition, the following expression levels were detected: 1.2 for qnrA1, 1.47 for qnrD1, 12.44 for qnrC1, and 80.63 for qnrB1. In case of long-term study, we selected a resistant strain in qnrB1-positive E. coli, and its expression increased from 105.91 to 212.31. On the contrary, plasmid copy number increased in time from 1 to 4.13. No mutations in gyrA or in parC chromosomal genes of treated strains were detected. Our results show that qnrB1-positive E. coli strain was able to develop fluoroquinolone resistance by upregulated qnrB1 expression that was linked to a minor increase in plasmid copy number but no mutations occurred in gyrA or parC.201930465448
205810.9997Occurrence of fluoroquinolones and fluoroquinolone-resistance genes in the aquatic environment. Fluoroquinolones (FQs) have been detected in aquatic environments in several countries. Long-term exposure to low levels of antimicrobial agents provides selective pressure, which might alter the sensitivity of bacteria to antimicrobial agents in the environment. Here, we examined FQ levels and the resistance of Escherichia coli (E. coli) to FQs by phenotyping and genotyping. In the aquatic environment in Osaka, Japan, ciprofloxacin, enoxacin, enfloxacin, lomefloxacin, norfloxacin, and ofloxacin were detected in concentrations ranging from 0.1 to 570 ng L(-1). FQ-resistant E. coli were also found. Although no obvious correlation was detected between the concentration of FQs and the presence of FQ-resistant E. coli, FQ-resistant E. coli were detected in samples along with FQs, particularly ciprofloxacin and ofloxacin. Most FQ-resistant E. coli carried mutations in gyrA, parC, and parE in quinolone resistance-determining regions. No mutations in gyrB were detected in any isolates. Amino acid changes in these isolates were quite similar to those in clinical isolates. Six strains carried the plasmid-mediated quinolone resistance determinant qnrS1 and expressed low susceptibility to ciprofloxacin and nalidixic acid: the minimum inhibitory concentrations ranged from 0.25 μg mL(-1) for ciprofloxacin, and from 8 to 16 μg mL(-1) for nalidixic acid. This finding confirmed that plasmids containing qnr genes themselves did not confer full resistance to quinolones. Because plasmids are responsible for much of the horizontal gene transfer, these genes may transfer and spread in the environment. To our knowledge, this is the first report of plasmid-mediated quinolone resistance determinant qnrS1 in the aquatic environment, and this investigation provides baseline data on antimicrobial resistance profiles in the Osaka area.201323291652
205920.9997Acetylation of fluoroquinolone antimicrobial agents by an Escherichia coli strain isolated from a municipal wastewater treatment plant. AIMS: To isolate environmental bacteria capable of transforming fluoroquinolones to inactive molecules. METHODS AND RESULTS: Bacteria were isolated from the aerobic liquor of a wastewater treatment plant on a medium containing norfloxacin (100 mg l(-1)). Twenty-two isolates were highly resistant (minimal inhibitory concentration: 6.25-200 microg ml(-1)) to five fluoroquinolones and six of them were positive by PCR amplification for the aminoglycoside resistance gene aac(6')-Ib. Of these, only Escherichia coli strain LR09 had the ciprofloxacin-acetylating variant gene aac(6')-Ib-cr; HPLC and mass spectrometry showed that this strain transformed both ciprofloxacin and norfloxacin by N-acetylation. This bacterium also had mutations in the quinolone-resistance determining regions of the gyrA and parC genes. CONCLUSIONS: An E. coli isolate from wastewater, which possessed at least two distinct fluoroquinolone resistance mechanisms, inactivated ciprofloxacin and norfloxacin by N-acetylation. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of N-acetylation of fluoroquinolones by an aac(6')-Ib-cr-containing bacterium from an environmental source.200919200322
206230.9996Expulsion of plasmid-mediated antibiotic resistance genes in E. coli by ethidium bromide and acridine orange treatment. Plasmid borne antibiotics resistance is the global threat to healthcare facilities. Such antibiotics resistance is inherited stably within the same bacterial generations and transmitted horizontally to other species of bacteria. The elimination of such resistance plasmid is of great importance to contain dispersal of antibiotics resistance. E. coli strains were identified, screened for the presence of antibiotics resistance by disc diffusion method, and cured by sub-lethal concentrations of Ethidium bromide and Acridine orange. After curing, again antibiotic resistance was determined. Before and after curing, plasmids were extracted by column spin Kit and subjected to 1% agarose gel electrophoresis and antibiotic resistance genes were identified by PCR. The Ethidium bromide was more effective than Acridine orange in eliminating antibiotics resistance and resistance genes bearing plasmids (4, 5, 6, 8, 9, 10 and <10kb). The most frequently eliminated antibiotic resistance was against Imipenem and Meropenem followed by Cefoperazone-sulbactam, Amikacin and cephalosporins in sequence. The loss of antibiotic resistance was associated with the elimination of plasmid-borne antibiotic resistance genes; bla-TEM, bla-SHV, bla-CTX-M, qnrA, qnrB, qnrC and qnrD. Some E. coli strains did not show the removal of antibiotics resistance and plasmids, suggesting the presence of resistance genes on main chromosome and or non-curable plasmids.202337548194
598040.9996Mutation in the gyrA gene of quinolone-resistant clinical isolates of Acinetobacter baumannii. The gyrA gene mutations associated with quinolone resistance were determined in 21 epidemiologically unrelated clinical isolates of Acinetobacter baumannii. Our studies highlight the conserved sequences in the quinolone resistance-determining region of the gyrA gene from A. baumannii and other bacteria. All 15 isolates for which the MIC of ciprofloxacin is > or = 4 micrograms/ml showed a change at Ser-83 to Leu. Six strains for which the MIC of ciprofloxacin is 1 microgram/ml did not show any change at Ser-83, although a strain for which the MIC of ciprofloxacin is 1 microgram/ml exhibited a change at Gly-81 to Val. Although it is possible that mutations in other locations of the gyrA gene, the gyrB gene, or in other genes may also contribute to the modulation of the MIC level, our results suggest that a gyrA mutation at Ser-83 is associated with quinolone resistance in A. baumannii.19957625818
229150.9996Multiple mechanisms contributing to ciprofloxacin resistance among Gram negative bacteria causing infections to cancer patients. Fluoroquinolones have been used for prophylaxis against infections in cancer patients but their impact on the resistance mechanisms still require further investigation. To elucidate mechanisms underlying ciprofloxacin (CIP) resistance in Gram-negative pathogens causing infections to cancer patients, 169 isolates were investigated. Broth microdilution assays showed high-level CIP resistance in 89.3% of the isolates. Target site mutations were analyzed using PCR and DNA sequencing in 15 selected isolates. Of them, all had gyrA mutations (codons 83 and 87) with parC mutations (codons 80 and 84) in 93.3%. All isolates were screened for plasmid-mediated quinolone resistance (PMQR) genes and 56.8% of them were positive in this respect. Among PMQR genes, aac(6')-Ib-cr predominated (42.6%) while qnr genes were harbored by 32.5%. This comprised qnrS in 26.6% and qnrB in 6.5%. Clonality of the qnr-positive isolates using ERIC-PCR revealed that most of them were not clonal. CIP MIC reduction by CCCP, an efflux pump inhibitor, was studied and the results revealed that contribution of efflux activity was observed in 18.3% of the isolates. Furthermore, most fluoroquinolone resistance mechanisms were detected among Gram-negative isolates recovered from cancer patients. Target site mutations had the highest impact on CIP resistance as compared to PMQRs and efflux activity.201830115947
207260.9996Interplay between IncF plasmids and topoisomerase mutations conferring quinolone resistance in the Escherichia coli ST131 clone: stability and resistance evolution. The Escherichia coli ST131 H30-Rx subclone vehicles CTX-M-15 plasmids and mutations in gyrA and parC conferring multidrug resistance successfully in the clinical setting. The aim of this study was (1) to investigate the relationship of specific topoisomerase mutations on the stability of IncF (CTX-M producing) plasmids using isogenic E. coli mutants and (2) to investigate the impact of the IncF-type plasmids present in the E. coli clone ST131 on the evolution of quinolone resistance. E. coli ATCC 25922 (background strain) and derived mutants encoding specific QRDR substitutions were used. Also, NGS-characterized IncFIA and IncFIB plasmids (encoding CTX-M genes) were included. Plasmid stability was evaluated by sequential dilutions into Luria broth medium without antibiotics for 7 days. Mutant frequency to ciprofloxacin was also evaluated. Moderate differences in the IncF plasmids stability were observed among E. coli ATCC 25922 and isogenic mutants. Under our experimental conditions, the fluctuation of bacteria harboring plasmids was less than 0.5-log((10)) in all cases. In the mutant frequency tests, it was observed that the presence of these IncF plasmids increased this value significantly (10-1000-fold). Quinolone resistance substitutions in gyrA or parC genes, frequently found associated with E. coli clone ST131, do not modify the stability of ST131-associated IncFIA and IncFIB plasmids under in vitro conditions. IncF-type plasmids present in E. coli clone ST131 facilitate the selection of resistance to quinolones. These results are consistent with the clinical scenario in which the combination of resistance to quinolones and beta-lactams is highly frequent in the E. coli clone ST131.202134787748
205070.9996Identification of a novel fosfomycin resistance gene (fosA2) in Enterobacter cloacae from the Salmon River, Canada. AIMS: To investigate the occurrence of fosfomycin-resistant (fos(R) ) bacteria in aquatic environments. METHODS AND RESULTS: A fos(R) strain of Enterobacter cloacae was isolated from a water sample collected at a site (50°41'33·44″N, 119°19'49·50″W) near the mouth of the Salmon River at Salmon Arm, in south-central British Columbia, Canada. The strain was identified by PCR screening for plasmid-borne, fosA-family amplicons, followed by selective plating. Sequencing of the resistance gene cloned using PCR primers to conserved flanking DNA revealed a new allele (95% amino acid identity to fosA), and I-Ceu I PFGE showed that it was chromosomally located. In Escherichia coli, the cloned DNA conferred a greater resistance to fosfomycin than its fosA counterpart. CONCLUSIONS: Gene fosA2 conferred fosfomycin resistance in an environmental isolate of Ent. cloacae. SIGNIFICANCE AND IMPACT OF THE STUDY: The repurposing of older antibiotics should be considered in the light of existing reservoirs of resistance genes in the environment.201121392044
207380.9996Plasmid-related quinolone resistance determinants in epidemic Vibrio parahaemolyticus, uropathogenic Escherichia coli, and marine bacteria from an aquaculture area in Chile. Marine bacteria from aquaculture areas with industrial use of quinolones have the potential to pass quinolone resistance genes to animal and human pathogens. The VPA0095 gene, related to the quinolone resistance determinant qnrA, from clinical isolates of epidemic Vibrio parahaemolyticus conferred reduced susceptibility to quinolone after cloning into Escherichia coli K-12 either when acting alone or synergistically with DNA gyrase mutations. In addition, a plasmid-mediated quinolone resistance gene from marine bacteria, aac(6')-Ib-cr, was identical to aac(6')-Ib-cr from urinary tract isolates of E. coli, suggesting a recent flow of this gene between these bacteria isolated from different environments. aac(6')-Ib-cr from E. coli also conferred reduced susceptibility to quinolone and kanamycin when cloned into E. coli K-12.201424760167
205690.9996Mechanisms of resistance in nontyphoidal Salmonella enterica strains exhibiting a nonclassical quinolone resistance phenotype. Nontyphoidal Salmonella enterica strains with a nonclassical quinolone resistance phenotype were isolated from patients returning from Thailand or Malaysia to Finland. A total of 10 isolates of seven serovars were studied in detail, all of which had reduced susceptibility (MIC > or = 0.125 microg/ml) to ciprofloxacin but were either susceptible or showed only low-level resistance (MIC < or = 32 microg/ml) to nalidixic acid. Phenotypic characterization included susceptibility testing by the agar dilution method and investigation of efflux activity. Genotypic characterization included the screening of mutations in the quinolone resistance-determining regions (QRDR) of gyrA, gyrB, parC, and parE by PCR and denaturing high-pressure liquid chromatography and the amplification of plasmid-mediated quinolone resistance (PMQR) genes qnrA, qnrB, qnrS, qnrD, aac(6')-Ib-cr, and qepA by PCR. PMQR was confirmed by plasmid analysis, Southern hybridization, and plasmid transfer. No mutations in the QRDRs of gyrA, gyrB, parC, or parE were detected with the exception of a Thr57-Ser substitution within ParC seen in all but the S. enterica serovar Typhimurium strains. The qnrA and qnrS genes were the only PMQR determinants detected. Plasmids carrying qnr alleles were transferable in vitro, and the resistance phenotype was reproducible in Escherichia coli DH5alpha transformants. These data demonstrate the emergence of a highly mobile qnr genotype that, in the absence of mutation within topoisomerase genes, confers the nontypical quinolone resistance phenotype in S. enterica isolates. The qnr resistance mechanism enables bacteria to survive elevated quinolone concentrations, and therefore, strains carrying qnr alleles may be able to expand during fluoroquinolone treatment. This is of concern since nonclassical quinolone resistance is plasmid mediated and therefore mobilizable.200919596880
5925100.9996Antimicrobial Resistance and Transconjugants Characteristics of sul3 Positive Escherichia coli Isolated from Animals in Nanning, Guangxi Province. Sulfonamides are the second most popular antibiotic in many countries, which leads to the widespread emergence of sulfonamides resistance. sul3 is a more recent version of the gene associated with sulfonamide resistance, whose research is relatively little. In order to comprehend the prevalence of sul3 positive E. coli from animals in Nanning, a total of 146 strains of E. coli were identified from some farms and pet hospitals from 2015 to 2017. The drug resistance and prevalence of sul3 E. coli were analyzed by polymerase chain reaction (PCR) identification, multi-site sequence typing (MLST), drug sensitivity test, and drug resistance gene detection, and then the plasmid containing sul3 was conjugated with the recipient strain (C600). The effect of sul3 plasmid on the recipient was analyzed by stability, drug resistance, and competitive test. In this study, forty-six sul3 positive E. coli strains were separated. A total of 12 ST types were observed, and 1 of those was a previously unknown type. The ST350 is the most numerous type. All isolates were multidrug-resistant E. coli, with high resistant rates to penicillin, ceftriaxone sodium, streptomycin, tetracycline, ciprofloxacin, gatifloxacin, and chloramphenicol (100%, 73.9%, 82.6%, 100%, 80.4%, 71.7%, and 97.8%, respectively). They had at least three antibiotic resistance genes (ARGs) in addition to sul3. The plasmids transferred from three sul3-positive isolates to C600, most of which brought seven antimicrobial resistance (AMR) and increased ARGs to C600. The transferred sul3 gene and the plasmid carrying sul3 could be stably inherited in the recipient bacteria for at least 20 days. These plasmids had no effect on the growth of the recipient bacteria but greatly reduced the competitiveness of the strain at least 60 times in vitro. In Nanning, these sul3-positive E. coli had such strong AMR, and the plasmid carrying sul3 had the ability to transfer multiple resistance genes that long-term monitoring was necessary. Since the transferred plasmid would greatly reduce the competitiveness of the strain in vitro, we could consider limiting the spread of drug-resistant isolates in this respect.202235454223
2046110.9996QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India. BACKGROUND & OBJECTIVES: Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to several antimicrobials in a diarrhoea outbreak at Ahmedabad during 2000. The present study was done to identify several genes responsible for antimicrobial resistance and mobile genetic elements in the ETEC strains. METHODS: Seventeen ETEC strains isolated from diarrhoeal patients were included in this study. The antimicrobial resistance was confirmed by conventional disc diffusion method. PCR and DNA sequencing were performed for the identification of mutation in the quinolone resistance-determining regions (QRDRs). Efflux pump was tested by inhibiting the proton-motive force. DNA hybridization assay was made for the detection of integrase genes and the resistance gene cassettes were identified by direct sequencing of the PCR amplicons. RESULTS: Majority of the ETEC had GyrA mutations at codons 83 and 87 and in ParC at codon 80. Six strains had an additional mutation in ParC at codon 108 and two had at position 84. Plasmid-borne qnr gene alleles that encode quinolone resistance were not detected but the newly described aac(6')-Ib-cr gene encoding a fluoroquinolne-modifying enzyme was detected in 64.7 per cent of the ETEC. Class 1 (intI1) and class 2 (intI2) integrons were detected in six (35.3%) and three (17.6%) strains, respectively. Four strains (23.5%) had both the classes of integrons. Sequence analysis revealed presence of dfrA17, aadA1, aadA5 in class 1, and dfrA1, sat1, aadA1 in class 2 integrons. In addition, the other resistance genes such as tet gene alleles (94.1%), catAI (70.6%), strA (58.8%), bla TEM-1 (35.2%), and aphA1-Ia (29.4%) were detected in most of the strains. INTERPRETATION & CONCLUSIONS: Innate gene mutations and acquisition of multidrug resistance genes through mobile genetic elements might have contributed to the emergence of multidrug resistance (MDR) in ETEC. This study reinforces the necessity of utilizing molecular techniques in the epidemiological studies to understand the nature of resistance responsible for antimicrobial resistance in different species of pathogenic bacteria.201121911975
2982120.9996Assessment of cooperative antibiotic resistance of Salmonella Typhimurium within heterogeneous population. This study was designed to investigate the cooperative resistance in the mixed culture of antibiotic-sensitive and antibiotic-resistant Salmonella Typhimurium. Strains of S. Typhimurium ATCC 19585 (ST(S)) and clinically isolated antibiotic-resistant S. Typhimurium CCARM 8009 (ST(R)) grown in single and mixture with 1 × MIC ceftriaxone (CEF) were used to determine the viability, β-lactamase activity, and gene expression. The MIC(50) values of ST(R) to CEF was increased by more than 5-fold with increasing inoculum densities from 10(2) to 10(7) CFU/mL. ST(S) was resistant to 1 × MIC CEF in the mixed culture of ST(S) and ST(R), showing the more than 10(8) CFU/mL after 20 h of incubation at 37 °C. The highest β-lactamase activity was 18 μmol/min/mL in the mixed culture, corresponding to the highest relative expression of β-lactamase-related genes (bla(TEM)). These results shed new light on the cooperative resistance of antibiotic-sensitive bacteria within a heterogeneous population including β-lactamase-producing bacteria.202134029657
2048130.9996The Role of Plasmids in the Multiple Antibiotic Resistance Transfer in ESBLs-Producing Escherichia coli Isolated From Wastewater Treatment Plants. We compared the diversity of extended-spectrum β-lactamases (ESBLs) producing Escherichia coli (E. coli) in wastewater of a municipal wastewater treatment plant. This was done by analyzing multiple antibiotic resistant phenotypes and genotypes. Also, we investigated the antibiotic resistance transfer mechanism of the plasmid by comparing the antibiotic resistance gene linked transfer using a conjugative test, and by analyzing the full-length DNA sequence of one plasmid. The results showed that 50 ESBLs-producing E. coli isolates were isolated from 80 wastewater samples at the rate of 62.5% (50/80), out of which 35 transconjugants were obtained with the multiple antibiotic resistant transfer rate as high as 70.0% (35/50). Multiple antibiotic resistance was shown in all transconjugants and donor bacteria, which were capable of resistance to 11 out of 15 kinds of antibiotics. Both transconjugants and donors were capable of resistance to the Ampicillin and Cefalotin at a rate of 100.00% (35/35), while the total antibiotic resistant spectrum of transconjugants narrowed at the rate of 94.29% (33/35) and broadened at the rate of 5.71% (2/35) after conjugate to the donor bacteria. PCR showed that the resistant genotypes decreased or remained unchanged when compared to donor bacteria with transconjugants while the bla(TEM) and bla(CTX-M) genes were transferred and linked at a rate of 100.00% (35/35) and the bla(SHV) gene was at the rate as high as 94.29% (33/35). However, the qnrS gene was transferred at a low rate of 4.17% (1/24). In addition, the major resistance gene subtypes were bla(TEM-) (1), bla(SHV -11) , and bla(CTX-M-15) according to sequencing and Blast comparison. Plasmid wwA8 is a closed-loop DNA molecule with 83157 bp, and contains 45 predicted genes, including three antibiotic resistant resistance genes, bla(CTX-M-15) , bla(TEM-1) and qnrS1, which can be transferred with E. coli in vitro. This study shows that E. coli isolated from wastewater was capable of transferring resistance genes and producing antibiotic resistant phenotypes. The plasmids containing different resistance genes in E. coli play an important role in the multiple antibiotic resistant transfer. Most importantly, antibiotic resistant resistance genes have different transfer efficiencies, the bla(TEM) and bla(CTX-M) genes transferred at a rate of 100.00% and linked transfer in all 35 transconjugants.201931001218
5955140.9996Integrons and gene cassettes in clinical isolates of co-trimoxazole-resistant Gram-negative bacteria. Despite a trend of declining consumption, resistance to co-trimoxazole has increased during a 12-year period in Stockholm. The molecular background to this surprising development was investigated by using PCR to screen for integrons and specific resistance genes, followed by sequence analysis of selected integrons, in 105 clinical urinary isolates of Gram-negative bacteria selected partly for trimethoprim resistance. Sixty-five integrons of class 1 or 2 were detected in a subset of 59 isolates, and of these positive isolates, all but one were resistant to trimethoprim. However, 11 isolates were resistant to trimethoprim, but negative for integrons. Isolates positive for integrons were resistant to an average of 4.2 antibiotics, compared with 1.9 antibiotics for integron-negative isolates. Despite this, the only gene cassettes identified in 19 class 1 integrons analysed were dfr and aadA cassettes. Thus, only resistance to trimethoprim, streptomycin, spectinomycin and sulphonamides could be explained by the presence of integrons in these isolates. A new dfr gene, named dfrA22, was discovered as a single gene cassette in a class 1 integron. In addition, sulphonamide resistance in many isolates was caused by carriage of sul2, which has no known association with integrons. Resistance to co-trimoxazole and many other antibiotics was thus not accounted for fully by the presence of integrons in these isolates.200515715715
2053150.9996Replicon typing of plasmids in environmental Achromobacter sp. producing quinolone-resistant determinants. This study aimed to investigate the antimicrobial resistance profile to quinolones, the presence of quinolone-resistant determinants and the plasmid replicon typing in environmental Achromobacter sp. isolated from Brazil. Soil and water samples were used for bacterial isolation. The antimicrobial susceptibility testing was performed by minimum inhibitory concentration method. The detection of mutations in the quinolone resistance-determining regions (QRDR) genes, the presence of plasmid-mediated quinolone resistance (PMQR) genes, and plasmid replicons were performed by PCR. A total of 16 isolates was obtained from different cultures, cities, and states of Brazil. All isolates were non-susceptible to ciprofloxacin, norfloxacin, and levofloxacin. Some mutations in QRDR genes were found, including Gln-83-Leu and Asp-87-Asn in the gyrA and Gln-80-Ile and Asp-84-Ala in the parC. Different PMQR genes were detected, such as qnrA, qnrB, qnrS, oqxA, and oqxB. Three different plasmid families were detected, being most presented the ColE-like, followed by IncFIB and IncA/C. The presence of different PMQR genes and plasmids in the isolates of the present study shows that environmental bacteria can act as reservoir of important genes of resistance to fluoroquinolones, which is of great concern, due to the potential of horizontal dissemination of these genes. Besides that, there are no studies reporting these results in Achromobacter sp. isolates.201830357960
2074160.9996Drug Resistance and Integron Genes in Escherichia coli Isolated from Urinary Tract Infection. Escherichia coli (E. coli) is a major cause of urinary tract infections. Treatment of these infections with antibiotics is often not effective due to the acquisition of drug-resistance genes by the bacteria. This process is mediated by integrons which belong to bacterial mobile genetic elements. Therefore, the present study addressed the issue of the relation between antibiotic resistance and integron genes in E. coli isolated from patients affected by urinary tract infection. Multiplex PCR assay employed to detect the E. coli integrase gene demonstrated that out of 49 bacterial strains, 26 were carrying class 1 integron and there was no case of bacteria harboring class 2 or class 3 integrons. Correlation analysis documented that E. coli strains harboring class 1 integron exhibited higher resistance towards tobramycin. The variable region gene cassette contained combinations of four genes responsible for antibiotic resistance: dfr17, aadA2, aadA5, and aac(6')-Ib-cr, of which the latter conferred tobramycin resistance. Together, the collected data underscore the need for identification and analysis of integrons in E. coli-induced urinary infections.201930961771
2055170.9996Prevalence and characterization of plasmid-mediated quinolone resistance genes in Salmonella isolated from poultry in Korea. The purpose of this study was to investigate the prevalence and characteristics of plasmid-mediated quinolone resistance (PMQR) genes qnr, aac(6')-Ib-cr, and qepA in a total of 185 non-duplicate Salmonella spp. isolated from hatcheries, poultry farms, and poultry slaughterhouses during the period 2001 to 2010 in Korea. Additionally, mutation analysis of quinolone resistance determining regions (QRDRs), conjugation experiments, and plasmid analysis were performed in the PMQR-positive isolates. Among the 185 isolates, six (3.2%) contained qnr genes (two qnrB4 and four qnrS1) but none carried the aac(6')-Ib-cr or qepA genes. Among the six PMQR-positive isolates, one showed a single mutation (Ser83-Phe substitution) in the QRDRs of gyrA. Among them, three were non-susceptible (intermediate or resistant) to nalidixic acid (minimum inhibitory concentration [MIC] ≥256 µg/ml), ciprofloxacin (MIC 2 µg/ml), and levofloxacin (MIC 4 µg/ml), but others were susceptible to all of the three fluoroquinolones. They were resistant to six or more antimicrobial agents tested and were able to transfer quinolone resistance to recipient Escherichia coli J53 by conjugation. By performing a hybridization test, plasmids harbouring qnrB4 and qnrS1 genes were less than 8 kb and about 70 kb in size, respectively. The horizontal dissemination of qnrS1 gene was mediated by IncN plasmid. Compared with the recipient strain, MICs of the transconjugants increased two-fold to four-fold for nalidixic acid, and eight-fold to 16-fold for ciprofloxacin and levofloxacin. This report is the first to describe the detection of qnr genes in Salmonella spp. isolated from poultry in Korea. Widespread horizontal transfer of these genes among bacteria may be a serious public health concern because these can rapidly increase fluoroquinolone resistance. To ensure the public health, it is essential to continuously survey and carefully monitor the spread of PMQR genes in Salmonella from poultry.201323607509
5924180.9995In vivo transfer of an incFIB plasmid harbouring a class 1 integron with gene cassettes dfrA1-aadA1. Transfer of resistance genes from bacteria from food producing animals to human pathogens is a potential risk to human health. The aim of this study was to determine in vivo transfer of a plasmid harbouring a class 1 integron containing gene cassettes dfrA1-aadA1 from Salmonella to Escherichia coli and the influence of the use of antimicrobials on this transfer. Thirty four-day-old SPF chickens colonized with E. coli K12 were divided into 3 groups of 10 animals each, and placed in separate isolators. Eleven days after inoculation with E. coli K12 the chickens were inoculated orally with 10(4)CFU of S. enterica spp. enterica serovar Typhimurium containing a plasmid harbouring a class 1 integron with gene cassettes dfrA1-aadA1. Two days after the administration of S. Typhimurium 1 group was treated orally with doxycycline, 1 group orally with trimethoprim/sulphamethoxazole and 1 group remained untreated (control group). E. coli K12, S. Typhimurium and the transconjugants were isolated from cloacal samples on selective MacConkey agar plates. Transfer of the plasmid was confirmed by plasmid characterization, PCR, PFGE and hybridization. Plasmid mediated transfer of a class 1 integron was observed almost immediately after inoculation with S. Typhimurium. Treatment of the chickens with antibiotics had neither a positive nor a negative effect on the transfer rates. In addition to the resistance genes located on the integron, resistance genes encoding for tetracycline and amoxicillin resistance transferred from the donor strain as well. The resistance genes and the integron were located on a 130 kb sized IncFIB plasmid. Our data demonstrate in vivo transfer of an IncFIB plasmid harbouring a class 1 integron containing gene cassettes dfrA1-aadA1 from Salmonella to E. coli, with or without selective pressure of antibiotics in chickens.200919264430
5926190.9995Prevalence and Characterization of Gentamicin Resistance Genes in Escherichia coli Isolates from Beef Cattle Feces in Japan. Gentamicin is an important antibiotic for the treatment of opportunistic infections in the clinical field. Gentamicin-resistant bacteria have been detected in livestock animals and can be transmitted to humans through the food supply or direct contact. We have previously revealed that gentamicin-resistant Escherichia coli are distributed at a comparatively high rate from beef cattle in Japan, but few studies have focused on the molecular epidemiology of gentamicin-resistant bacteria. To understand these bacteria, this study examined the prevalence of various gentamicin resistance genes in gentamicin-resistant E. coli isolates from beef cattle feces. Of the 239 gentamicin-resistant E. coli isolates, the presence of the aacC2, aadB, or aac(3)-VIa genes was confirmed in 147, 84, and 8 isolates, respectively. All aac(3)-VIa-harboring isolates had an MIC value of 64 μg/mL for gentamicin and exhibited resistance to 11 antibiotic agents. An analysis of the representative aac(3)-VIa-harboring E. coli strain GC1-3-GR-4 revealed that the aac(3)-VIa gene was present on the IncA/C plasmid together with the aadA and bla(CMY) genes. Furthermore, the upstream region of the aac(3)-VIa gene contained the aadA gene and the class 1 integron-integrase gene (intI1). The aac(3)-VIa gene was detected for the first time in Japan and is expected to be able to transfer between bacteria via the IncA/C plasmid and integron. These results reveal the expansion of the distribution or diversity of gentamicin resistance genes in Japan.202235704076