Mechanisms of Resistance in Clinical Isolates of Enterobacter cloacae that Are Less Susceptible to Cefepime than to Ceftazidime. - Related Documents




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229301.0000Mechanisms of Resistance in Clinical Isolates of Enterobacter cloacae that Are Less Susceptible to Cefepime than to Ceftazidime. Thirty-two Enterobacter cloacae strains that are less susceptible to cefepime than to ceftazidime were collected. This unique phenotype of 8 strains was confirmed using the agar dilution method. OXA1, OXA10, OXA31 and OXA35 were detected in 3, 2, 3, and 2 strains, respectively, whereas all strains were negative for PSE-1 genes. OXA genes were also identified in the plasmid DNA of 5 strains, but only 2 strains were positive in a conjugation experiment. The acrA, acrB and tolC genes were identified in 4, 4 and 6 strains, respectively. Decreased expression of the acrA mRNA and overexpression of the acrB and tolC mRNAs were observed using real-time RT-PCR. Most of the bacteria (n=7) stably expressed the marA gene, which is a regulatory gene in the AcrAB-TolC multidrug efflux system, whereas all strains were negative for ramA. The acrA, acrB, tolC, acrR and marA genes were similar to the genes in reference strains in GenBank, with nucleotide homologies of 96%, 98%, 98%, 98% and 100%, respectively. In conclusion, the mechanism of resistance of Enterobacter cloacae with less susceptibility to cefepime than to ceftazidime is associated with the overexpression of AcrAB-TolC and the production of OXA1, XA10, OXA31 and OXA35.201829970440
229710.9997Efflux Pump Activity and Mutations Driving Multidrug Resistance in Acinetobacter baumannii at a Tertiary Hospital in Pretoria, South Africa. Acinetobacter baumannii (A. baumannii) has developed several resistance mechanisms. The bacteria have been reported as origin of multiple outbreaks. This study aims to investigate the use of efflux pumps and quinolone resistance-associated genotypic mutations as mechanisms of resistance in A. baumannii isolates at a tertiary hospital. A total number of 103 A. baumannii isolates were investigated after identification and antimicrobial susceptibility testing by VITEK2 followed by PCR amplification of bla (OXA-51) . Conventional PCR amplification of the AdeABC efflux pump (adeB, adeS, and adeR) and quinolone (parC and gyrA) resistance genes were performed, followed by quantitative real-time PCR of AdeABC efflux pump genes. Phenotypic evaluation of efflux pump expression was performed by determining the difference between the MIC of tigecycline before and after exposure to an efflux pump inhibitor. The Sanger sequencing method was used to sequence the parC and gyrA amplicons. A phylogenetic tree was drawn using MEGA 4.0 to evaluate evolutionary relatedness of the strains. All the collected isolates were bla (OXA-51) -positive. High resistance to almost all the tested antibiotics was observed. Efflux pump was found in 75% of isolates as a mechanism of resistance. The study detected parC gene mutation in 60% and gyrA gene mutation in 85%, while 37% of isolates had mutations on both genes. A minimal evolutionary distance between the isolates was reported. The use of the AdeABC efflux pump system as an active mechanism of resistance combined with point mutation mainly in gyrA was shown to contribute to broaden the resistance spectrum of A. baumannii isolates.202134659419
229120.9997Multiple 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
229430.9997Antimicrobial Resistance of Clinical Klebsiella pneumoniae Isolates: Involvement of AcrAB and OqxAB Efflux Pumps. BACKGROUND: Over the last several decades, the AcrAB and OqxAB efflux pumps have been found to cause multidrug resistance (MDR) in various bacteria, most notably Klebsiella pneumoniae. Antibiotic resistance surges with increased expression of the acrAB and oqxAB efflux pumps. METHODS: In accordance with CLSI guidelines, a disk diffusion test was carried out using 50 K. pneumoniae isolates obtained from various clinical samples. CT was computed in treated samples and compared to a susceptible ciprofloxacin strain (A111). The final finding is presented as the fold change in the target gene's expression in treated samples relative to a control sample (A111), normalized to a reference gene. As ΔΔCT = 0 and 2 to the power of 0 = 1, relative gene expression for reference samples is often set to 1 Results: The highest rates of resistance were recognized with cefotaxime (100%), cefuroxime (100%), cefepime (100%), levofloxacin (98%), trimethoprimsulfamethoxazole (80%), and gentamicin (72%), whereas imipenem (34%) had the lowest rates. Overexpression of acrA and acrB, oqxA and oqxB, regulators marA, soxS, and rarA were greater in ciprofloxacin-resistant isolates compared to the reference strain (strain A111). There was also a moderate connection between ciprofloxacin MIC and acrAB gene expression and a moderate connection between ciprofloxacin MIC and oqxAB gene expression. CONCLUSION: This work provides a deeper knowledge of the role of efflux pump genes, particularly acrAB and oqxAB, as well as transcriptional regulators marA, soxS, and rarA, in bacterial resistance to ciprofloxacin.202436999690
598040.9997Mutation 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
229550.9996The drug resistance profile of Mycobacterium abscessus group strains from Korea. BACKGROUND: Bacteria of the Mycobacterium abscessus group are the second most common pathogens responsible for lung disease caused by nontuberculous mycobacteria in Korea. There is still a lack of studies investigating the genetic mechanisms involved in M. abscessus resistance to antibiotics other than clarithromycin. This study investigated the characteristics of drug resistance exhibited by M. abscessus clinical isolates from Korea. METHODS: We performed drug susceptibility testing for a total of 404 M. abscessus clinical strains. Subspecies were differentiated by molecular biological methods and examined for mutations in drug resistance-related genes. RESULTS: Of the 404 strains examined, 202 (50.00%), 199 (49.26%), and 3 (0.74%) strains were identified as M. abscessus, M. massiliense, and M. bolletii, respectively. Of the 152 clarithromycin-resistant strains, 6 possessed rrl mutations, while 4 of the 30 amikacin-resistant strains contained rrs mutations, and 5 of the 114 quinolone-resistant strains had gyr mutations. All mutant strains had high minimal inhibitory concentration values for the antibiotics. CONCLUSIONS: Our results showed the distribution of the strains with mutations in drug resistance-related genes was low in the M. abscessus group. Furthermore, we performed drug susceptibility testing and sequence analyses to determine the characteristics of these genes in the M. abscessus group.201424422193
229660.9996Multi-drug resistance profiles and the genetic features of Acinetobacter baumannii isolates from Bolivia. INTRODUCTION: Acinetobacter baumannii is opportunistic in debilitated hospitalised patients. Because information from some South American countries was previously lacking, this study examined the emergence of multi-resistant A. baumannii in three hospitals in Cochabamba, Bolivia, from 2008 to 2009. METHODOLOGY: Multiplex PCR was used to identify the main resistance genes in 15 multi-resistant A. baumannii isolates. RT-PCR was used to measure gene expression. The genetic environment of these genes was also analysed by PCR amplification and sequencing. Minimum inhibitory concentrations were determined for key antibiotics and some were determined in the presence of an efflux pump inhibitor, 1-(1-napthylmethyl) piperazine. RESULTS: Fourteen strains were found to be multi-resistant. Each strain was found to have the blaOXA-58 gene with the ISAba3-like element upstream, responsible for over-expression of the latter and subsequent carbapenem resistance. Similarly, ISAba1, upstream of the blaADC gene caused over-expression of the latter and cephalosporin resistance; mutations in the gyrA(Ser83 to Leu) and parC (Ser-80 to Phe) genes were commensurate with fluoroquinolone resistance. In addition, the adeA, adeB efflux genes were over-expressed. All 15 isolates were positive for at least two aminoglycoside resistance genes. CONCLUSIONS: This is one of the first reports analyzing the multi-drug resistance profile of A. baumannii strains isolated in Bolivia and shows that the over-expression of theblaOXA-58, blaADC and efflux genes together with aminoglycoside modifying enzymes and mutations in DNA topoisomerases are responsible for the multi-resistance of the bacteria and the subsequent difficulty in treating infections caused by them.201323592642
227570.9996Contribution of β-lactamase and efflux pump overproduction to tazobactam-piperacillin resistance in clinical isolates of Escherichia coli. INTRODUCTION: Tazobactam-piperacillin (TZP) is a mixture of a broad-spectrum penicillin and an irreversible β-lactamase inhibitor. TZP is effective against Gram-negative bacteria that produce extended-spectrum β-lactamases, and it is used as a first-line or second-line drug to treat serious infections. METHODS: This study identified three TZP-resistant and two TZP-intermediate strains among 514 clinical isolates of Escherichia coli. RESULTS: These five isolates possessed one or more β-lactamase genes, bla(TEM-1), bla(CTX-M-2), bla(CTX-M-14), and/or bla(CMY-8). The expression levels of β-lactamase genes and acrAB genes in the strains were examined by using real-time reverse transcription PCR. The total enzymatic piperacillin-degrading activity in cells was determined. Two TZP-resistance mechanisms were identified: hyperproduction of TEM-1 in the two resistant strains; and simultaneous high production of β-lactamase and efflux pump AcrAB in the two TZP-intermediate isolates. The latter are an international high-risk clone O25b:H4-ST131-H30R. CONCLUSION: TZP resistance is still rare in clinical isolates of E. coli. However, resistance can develop on high production and/or combinations of known antimicrobial resistance mechanisms in different ways.202032062000
228280.9996Cross resistance of quinolone derivatives in gram-negative bacteria. A total of 127 Gram-negative bacteria resistant to nalidixic acid were isolated from as many patients affected by urinary tract infections and hospitalized in the first Clinic of Infectious Diseases, University of Naples. Enterobacteria were identified by Enterotube system (Roche) and API 20 system (Ayerst). Non-fermentative bacteria were identified by OXI/FERM system (Roche). The following bacteria were collected: Escherichia coli 50, Proteus spp. 35, Enterobacter agglomerans 12, Serratia sp. 5, Pseudomonas aeruginosa 25. The in vitro antibacterial activity of nalidixic acid and three other quinoline derivatives (pipemidic acid, oxolinic acid and ciprofloxacin) were studied by determining the MICs by a miniaturized dilution broth method. The MICs were compared to evaluate the eventual cross resistance to the drugs under examination within each bacterial species. The results showed that 23% of bacteria were resistant to nalidixic acid, pipemidic acid and oxolinic acid; 49.6% to nalidixic and pipemidic acid and 0.7% to nalidixic acid and oxolinic acid. On the other hand none of the bacteria were resistant to ciprofloxacin. The last showed very low MICs against all the bacteria under examination, including Pseudomonas and Serratia. The high antibacterial activity of ciprofloxacin even against bacteria highly resistant to the other quinolines could be due to a greater affinity of the target sites or to the better permeability of resistant strains to the newer drug or because it is unaffected until now by mutations of genes responsible for cross resistance.19853159488
245790.9995Prevalence and molecular mechanisms of colistin resistance in Acinetobacter baumannii clinical isolates in Tehran, Iran. Colistin is one of the last remaining active antibiotics against multidrug resistant Gram-negative bacteria. However, several recent studies reported colistin-resistant (ColR) Acinetobacter baumannii from different countries. In the current study, we investigated molecular mechanisms involved in colistin resistance in A. baumannii isolates from different clinical samples. A total of 110 clinical A. baumannii isolates were collected from two hospitals in Tehran. Minimum inhibitory concentrations (MICs) were determined by broth microdilution according to the Clinical and Laboratory Standards Institute. For the ColR isolates, mutation was detected in pmrA, pmrB, lpxA, lpxC, and lpxD genes using the polymerase chain reaction (PCR) and sequencing. Moreover, the relative expression of the pmrC gene was calculated using quantitative reverse transcription PCR. Three colistin resistant isolates were identified with MIC between 8 and 16 μg/mL and were resistant to all the tested antimicrobial agents. All the three isolates had a mutation in the pmrB, pmrA, lpxA, lpxD, and lpxC genes. Moreover, the overexpression of pmrC gene was observed in all isolates. Our results showed that the upregulation of the PmrAB two component system was the primary mechanism linked to colistin resistance among the studied colistin resistant A. baumannii isolates.202134370684
2316100.9995Clinical Klebsiella pneumoniae isolates and their efflux pump mechanism for antibiotic resistance challenge. BACKGROUND: Klebsiella pneumoniae is a serious pathogen that causes many disorders in humans and animals. Klebsiella pneumoniae, which is one of the most important pathogens in hospitals, often causes many clinical manifestations, including pneumonia, urinary tract infections, and meningitis. Interest in this bacterium has increased due to the increasing incidence of infection caused by it, as well as its high resistance to antibiotics, especially broad-spectrum antibiotics. AIM: This study showed the efflux pump mechanism of clinical K. pneumoniae isolates and antibiotic resistance in samples collected from sheep and human respiratory tract infection in southern Iraq. METHODS: Three hundred samples were collected, and the samples included: 150 nasal swabs from sheep and 150 sputum samples from humans. Through bacteriological and biochemical examinations. The isolates were identified K. pneumoniae isolates were also confirmed by 16S rRNA. Susceptibility testing of the antibiotics used in the study. To determine the phenotypic efflux pump activity, the agar ethidium bromide cartwheel method was used. RESULTS: Of 150 sputum human specimens and 150 nasal swabs from sheep were tested, 25 and 17 K. pneumoniae species isolates from patients and sheep, respectively, for the resistance of the bacteria isolated from humans to antibiotics. The highest rate of resistance was to piperacillin (88%), and the lowest rate was to antibiotics (36%), imipenem. The highest of bacterial susceptibility to the antibiotic imipenem was (44%) and (36%) for levofloxacin, respectively. For the bacterial isolates from sheep, the highest percentage of resistance to rifampin was (82.3%), and the highest percentage of sensitivity was to imipenem and Levofloxacin antibiotics. The results showed that most of the 39 bacterial isolates (92.8%) possessed an efflux pump mechanism. The result of genotyping to identify the efflux pump genes tolC and acrAB revealed that all isolates carried the genes. CONCLUSION: All the isolates were resistant to antibiotics, and the bacterial isolates under study most possess the efflux pump mechanism. All bacteria also have efflux pump genes, and this gives the bacteria more resistance against many antibiotics.202541036356
2059110.9995Acetylation 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
2317120.9995Molecular Detection of Adefg Efflux Pump Genes and their Contribution to Antibiotic Resistance in Acinetobacter baumannii Clinical Isolates. BACKGROUND: Acinetobacter baumannii (A. baumannii) is one of the most important bacteria causing nosocomial infections worldwide. Over the past few years, several strains of A. baumannii have shown antibiotic resistance, which may be due to the activity of efflux pumps. This study was aimed to detect AdeFG efflux pump genes and their contribution to antibiotic resistance in A. baumannii clinical isolates. METHODS: A total of 200 A. baumannii clinical isolates were collected from clinical specimens of ulcers, pus, sputum, and blood. All isolates were identified using standard biochemical tests. After identifying and cleaving the genome by boiling, PCR was performed on samples using specific primers. The antimicrobial susceptibility patterns were determined by disk diffusion, with and without CCCP efflux pump inhibitor were determined according to CLSI guidelines. RESULTS: We identified 60 clinical isolates of A. baumannii using biochemical differential tests. Identification of all A. baumannii isolates was confirmed by blaOXA-51-like PCR. According to the results of our study, 98.37% of A. baumannii isolates were resistant to ciprofloxacin, norfloxacin, and levofloxacin. PCR results indicated that all 60 A. baumannii isolates contained the AdeF and 76.66% contained AdeG. CONCLUSION: the results of this study demonstrated that most of the A. baumannii isolates contained AdeF and AdeG efflux pump genes, and more than 98% of the isolates were resistant to ciprofloxacin, norfloxacin, and levofloxacin. This reflected the significant contribution of efflux pumps to the development of resistance to these antibiotics.202032582800
2045130.9995Molecular characterization of multidrug-resistant Shigella species isolated from epidemic and endemic cases of shigellosis in India. Shigella species represent one of the growing numbers of antimicrobial-resistant bacteria in developing countries. Fluoroquinolone-resistant strains of Shigella dysenteriae type 1 and Shigella flexneri type 2a emerged in India during 2002 and 2003, respectively. Sixty strains of Shigella from different parts of India were analysed for antimicrobial susceptibility, the presence of the qnr plasmid, mutations in the quinolone resistance determining regions (QRDRs), fluoroquinolone accumulation, and the presence of other genes encoding resistance to various antimicrobials. Fluoroquinolone-resistant strains had mutations in gyrA and parC genes and had an active efflux system. They were also resistant to several other antimicrobials but were susceptible to azithromycin and ceftriaxone. The majority of the strains harboured genes encoding resistance to ampicillin (97 %), tetracycline (95 %), streptomycin (95 %) and chloramphenicol (94 %). PFGE analysis revealed clonality among strains of S. dysenteriae types 1 and 5, S. flexneri type 2a and Shigella boydii type 12.200818566144
2276140.9995Role of gyrase A/B double mutations along with Qnr genes in development of higher ciprofloxacin resistance among pathogenic Escherichia coli and Klebsiella pneumoniae. Contribution of quinolone resistant (QR) genes, efflux pumps (AcrB) over-expression and outer membrane proteins (OMPs) loss/reduction, gyrA/B mutation towards development of quinolone resistance of pathogenic E.coli and Klebsiella sp was explored. Phenotypic characterization of 715 bacteria, isolated from Indian patients during 2011-2017 was performed by Kirby-Bauer disc diffusion assay. Minimum inhibitory concentration of ciprofloxacin was determined by broth microdilution assay. Presence of QR, gyrA/B genes was examined by PCR; acrB upregulation by quantitative PCR and porin profile by SDS-PAGE. Catalytic pockets of modelled proteins were characterized and their interaction with ciprofloxacin was analyzed using AutoDock. Isolates were phenotypically categorized into QR1-QR4 groups according to their resistance against single-four quinolones. Percent prevalence of QR-genes among isolates increased gradually with resistance against increasing number of quinolone antibiotics. Gradual increase in % partial reduction/complete loss of porins was observed from QR1 to QR4 groups with highest fold of Omp reduction. Similar trend was also observed in % prevalanace of upregulated acrB genes among these phenotypic groups with highest fold of upregulation observed among QR2 group. Isolates with GyrA-Ser83Leu + Asp87Asn and GyrB-Asn440Thr + Ser463Ala mutants harbouring Qnr genes mostly demonstrated highest MICs. This is also evident from greater hydrolytic efficiency (ΔG◦ value) of double mutants than their wild types. Dislocation of drug binding site among mutated-GyrA might explain their lower affinity towards quinolones -thus lowering their drug susceptibility. These findings underscore GyrA/B double mutants' role in higher QR among pathogenic E.coli and Klebsiella species, which might guide future antimicrobial therapy.202540784534
2305150.9995In-vitro activity of tigecycline against multidrug-resistant Gram negative bacteria: The experience of a university hospital. The emergence of multidrug-resistant Gram negative bacteria has given rise to significant therapeutic challenges. These pathogens may have developed resistance to tigecycline, which is an alternative antibiotic used empirically in the treatment of serious infections. The objectives of this study were to identify the in-vitro activity of tigecycline against multidrug-resistant Gram negative strains isolated from clinical specimens and their related genes, at a university hospital. For this, 150 clinical isolates of multidrug-resistant Gram negative cultures from various clinical specimens were collected. Bacterial isolates were cultured, identified and their antibiotic susceptibilities were determined. Polymerase chain reaction was performed to amplify AcrB, AmpC, RamR, MexR, AdeB, TetA genes. Results revealed that all isolates were multidrug-resistant. The resistance of isolates was 91.4% to aztreonam, 94.6% to piperacillin, 34% to imipenem, 38.7% to meropenem, 71.3% to levofloxacin, 97.3% to ceftriaxone, 94.7% to cefepime, 9.3% to colistin, 78% to tetracycline, 21.4% to tigecycline and 68% to trimethoprim. AcrB, AmpC, RamR, MexR, AdeB, TetA genes were present in multidrug-resistant Gram negative bacteria. AcrB, RamR, TetA genes were related to tigecycline resistance. It is concluded that infections caused by multidrug-resistant Gram negative bacteria occur at a high rate. Most isolates were multi drug resistant, with 21.4% being resistant to tigecycline.202133743369
2158160.9995Relationship of OqxAB efflux pump to antibiotic resistance, mainly fluoroquinolones in Klebsiella pneumoniae, isolated from hospitalized patients. OBJECTIVES: This research was designed to study the prevalence of OqxAB efflux pump genes and also to investigate the relationship between efflux pump and resistance to antibiotics, especially to fluoroquinolones, evaluate the expression levels of OqxAB genes, and molecular typing of Klebsiella pneumoniae isolated from hospitalized patients in Hamadan hospitals, west of Iran. MATERIALS AND METHODS: In a cross-sectional study, 100 clinical strains of K. pneumoniae were isolated from hospitalized patients in three major teaching hospitals from January to June 2021. The antibiotic susceptibility of isolates was evaluated by the disk-diffusion agar method. The frequency of genes encoding oqxA and oqxB of efflux pump genes was investigated by PCR, and the expression of the oqxA efflux pump gene was investigated by the Real-time PCR method. The genetic relationship of K. pneumoniae isolates was analyzed by the Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR technique. RESULTS: According to our results, the multi-drug resistance phenotype (MDR) in 65% and high prevalence resistance to ciprofloxacin in 89% of K. pneumoniae isolates was detected. The higher prevalence of oqxA (95%) and oqxB (98%) was also detected. There was a significant relationship between ciprofloxacin resistance and the oqxB gene as well as between ceftriaxone and chloramphenicol resistance and the oqxA gene. The expression of the oqxA gene was higher in ciprofloxacin-resistant isolates. CONCLUSION: The results of this study suggest a potential reservoir for the spread of OqxAB genes among hospital-acquired bacteria. Infection control strategies should be used prudently to reduce the spread of resistant strains of K. pneumoniae in hospitals.202336594055
5979170.9995Mutations in gyrA, gyrB, parC, and parE in quinolone-resistant strains of Neisseria gonorrhoeae. Mutations in the genes for the subunits GyrA and ParC of the target enzymes DNA gyrase and topoisomerase IV are important mechanisms of resistance in quinolone-resistant bacteria, including Neisseria gonorrhoeae. The target enzymes also consist of the subunits GyrB and ParE, respectively, though their role in quinolone-resistance has not been fully investigated. We sequenced the quinolone-resistance-determining regions (QRDR) of gyrA, gyrB, parC, and parE in 25 ciprofloxacin-resistant strains from Bangladesh (MIC 4-->32 mg/l) and 5 susceptible strains of N. gonorrhoeae. All the resistant strains had three or four mutations. Two of these were at positions 91 and 95 of gyrA. Fourteen strains had an additional mutation in parC at position 91, and 17 strains had an additional mutation in parE in position 439. No alterations were found in gyrB. The five susceptible strains had identical DNA sequences. Data indicate that the mutations detected in the QRDR of gyrA and parC may be important in the development of quinolone resistance. According to transformation experiments we assume that the alteration in parE is not related to a high degree of quinolone resistance. There was no correlation between ciprofloxacin MICs and pattern or number of mutations in the target genes.200212529019
2446180.9995Low selection of topoisomerase mutants from strains of Escherichia coli harbouring plasmid-borne qnr genes. OBJECTIVES: To investigate mutations in the type II topoisomerase genes in quinolone-resistant mutants selected from bacteria harbouring plasmid-borne qnr genes. METHODS: Mutants were selected by nalidixic acid, ciprofloxacin and moxifloxacin from two Escherichia coli reference strains and corresponding transconjugants harbouring qnrA1, qnrA3, qnrB2 or qnrS1 genes. RESULTS: The proportion of resistant mutants selected by the three quinolones was, respectively, in the same range for qnr-positive transconjugants and reference strains. Only 20% (65/329) of the mutants selected from the transconjugants showed a gyrase mutation, whereas 79% (94/119) of those from the reference strains without a qnr gene did (P < 0.0001). At four times the MIC of the selector quinolone, gyrA mutants represented 49% and 95% of the mutants selected with nalidixic acid, 4% and 94% with ciprofloxacin and 0% and 54% with moxifloxacin for qnr-positive transconjugants and reference strains, respectively. Mutations within gyrA were distributed at codon 87 (D87G, H, N or Y) and at codon 83 (S83L) with three novel mutations (gyrA Ser83stop, gyrA Asp82Asn and gyrB insertion of Glu at 465) and three rare mutations (gyrA Gly81Asp, gyrA Asp82Gly and gyrA Ser431Pro), mainly obtained from reference strains after moxifloxacin selection. Strikingly, none of the mutants selected by moxifloxacin from qnr-positive transconjugants harboured a mutation in the topoisomerase genes. CONCLUSIONS: Topoisomerase mutants are rarely selected by ciprofloxacin and moxifloxacin from strains harbouring qnr. This suggests that the quinolone resistance-determining region domains are protected from quinolones by the Qnr protein and consequently other mechanisms are developed to acquire a further step of fluoroquinolone resistance.200818325893
2331190.9995Bacteriological and molecular study of fosfomycin resistance in uropathogenic Escherichia coli. The identification of genes associated with resistance has the potential to facilitate the development of novel diagnostic tests and treatment methods. The objective of this study was to examine the antibiotic resistance and Fosfomycin resistance genes in uropathogenic Escherichia coli (UPEC) in patients in Baghdad, Iraq. After analyzing 250 urine samples using various identification methods, including the examination of morphological characteristics, biochemical tests, and genetic detection, it was determined that E. coli was the most common bacteria present, accounting for 63.6% of the samples. Antibiotic susceptibility testing showed a significant prevalence of resistance to various antibiotics, with 99.3% of E. coli isolates exhibiting multiple drug resistance (MDR). Fosfomycin showed antibacterial properties against UPEC. The minimum inhibitory concentration (MIC) ranged from 512 to 1024 μg/mL, while the minimum bactericidal concentration (MBC) was 2048 μg/mL. In the time-kill assay, fosfomycin was effective against fosfomycin-resistant isolates within 8-12 h. The genetic determinants associated with fosfomycin resistance were examined through the utilization of polymerase chain reaction (PCR). The findings indicated that the genes murA, glpT, and cyaA were detected in all the isolates when genomic DNA was used as a template. However, all the tests yielded negative results when plasmid was used as a template. The genes fosA3 and fosA4 were detected in 8.6% and 5% of the isolates when genomic DNA was used as a template. When plasmid was used as a template, the genes fosA3 and fosA4 were found in 5.7% and 2.9% of the isolates, respectively. In conclusion, there is an increasing problem with antibiotic resistance in UPEC, with elevated rates of resistance to several antibiotics. The study also offers novel insights into the genetic foundation of fosfomycin resistance in UPEC.202438367167