scholarly journals Mechanisms Accounting for Fluoroquinolone Resistance in Escherichia coli Clinical Isolates

2008 ◽  
Vol 53 (1) ◽  
pp. 235-241 ◽  
Author(s):  
Sonia K. Morgan-Linnell ◽  
Lauren Becnel Boyd ◽  
David Steffen ◽  
Lynn Zechiedrich
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Multidrug Efflux Pump ◽  
Topoisomerase Iv ◽  
E Coli ◽  
Genes Encoding

ABSTRACT Fluoroquinolone MICs are increased through the acquisition of chromosomal mutations in the genes encoding gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE), increased levels of the multidrug efflux pump AcrAB, and the plasmid-borne genes aac(6′)-Ib-cr and the qnr variants in Escherichia coli. In the accompanying report, we found that ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant E. coli clinical isolates were very high and widely varied (L. Becnel Boyd, M. J. Maynard, S. K. Morgan-Linnell, L. B. Horton, R. Sucgang, R. J. Hamill, J. Rojo Jimenez, J. Versalovic, D. Steffen, and L. Zechiedrich, Antimicrob. Agents Chemother. 53:229-234, 2009). Here, we sequenced gyrA, gyrB, parC, and parE; screened for aac(6′)-Ib-cr and qnrA; and quantified AcrA levels in E. coli isolates for which patient sex, age, location, and site of infection were known. We found that (i) all fluoroquinolone-resistant isolates had gyrA mutations; (ii) ∼85% of gyrA mutants also had parC mutations; (iii) the ciprofloxacin and norfloxacin MICs for isolates harboring aac(6′)-Ib-cr (∼23%) were significantly higher, but the gatifloxacin and levofloxacin MICs were not; (iv) no isolate had qnrA; and (v) ∼33% of the fluoroquinolone-resistant isolates had increased AcrA levels. Increased AcrA correlated with nonsusceptibility to the fluoroquinolones but did not correlate with nonsusceptibility to any other antimicrobial agents reported from hospital antibiograms. Known mechanisms accounted for the fluoroquinolone MICs of 50 to 70% of the isolates; the remaining included isolates for which the MICs were up to 1,500-fold higher than expected. Thus, additional, unknown fluoroquinolone resistance mechanisms must be present in some clinical isolates.

scholarly journals Genetic Characterization of Highly Fluoroquinolone-Resistant Clinical Escherichia coli Strains from China: Role ofacrR Mutations

2001 ◽  
Vol 45 (5) ◽  
pp. 1515-1521 ◽  
Author(s):  
Hui Wang ◽  
Joann L. Dzink-Fox ◽  
Minjun Chen ◽  
Stuart B. Levy
Keyword(s):  
Escherichia Coli ◽  
Blot Analysis ◽  
Genetic Basis ◽  
Efflux Pump ◽  
Pcr Amplification ◽  
Fluoroquinolone Resistance ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
E Coli ◽  
High Level

ABSTRACT The genetic basis for fluoroquinolone resistance was examined in 30 high-level fluoroquinolone-resistant Escherichia coliclinical isolates from Beijing, China. Each strain also demonstrated resistance to a variety of other antibiotics. PCR sequence analysis of the quinolone resistance-determining region of the topoisomerase genes (gyrA/B, parC) revealed three to five mutations known to be associated with fluoroquinolone resistance. Western blot analysis failed to demonstrate overexpression of MarA, and Northern blot analysis did not detect overexpression of soxS RNA in any of the clinical strains. The AcrA protein of the AcrAB multidrug efflux pump was overexpressed in 19 of 30 strains of E. colitested, and all 19 strains were tolerant to organic solvents. PCR amplification of the complete acrR (regulator/repressor) gene of eight isolates revealed amino acid changes in four isolates, a 9-bp deletion in another, and a 22-bp duplication in a sixth strain. Complementation with a plasmid-borne wild-type acrR gene reduced the level of AcrA in the mutants and partially restored antibiotic susceptibility 1.5- to 6-fold. This study shows that mutations in acrR are an additional genetic basis for fluoroquinolone resistance.

scholarly journals Intensity and Mechanisms of Fluoroquinolone Resistance within theH30 andH30Rx Subclones of Escherichia coli Sequence Type 131 Compared with Other Fluoroquinolone-Resistant E. coli

2015 ◽  
Vol 59 (8) ◽  
pp. 4471-4480 ◽  
Author(s):  
James R. Johnson ◽  
Brian Johnston ◽  
Michael A. Kuskowski ◽  
Evgeni V. Sokurenko ◽  
Veronika Tchesnokova
Keyword(s):  
Escherichia Coli ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Sequence Type ◽  
Fluoroquinolone Resistance ◽  
Solvent Tolerance ◽  
Organic Solvent Tolerance ◽  
Content Type ◽  
E Coli ◽  
Pump Activity

ABSTRACTThe recent expansion of theH30 subclone ofEscherichia colisequence type 131 (ST131) and its CTX-M-15-associatedH30Rx subset remains unexplained. Although ST131H30 typically exhibits fluoroquinolone resistance, so do multiple otherE. colilineages that have not expanded similarly. To determine whetherH30 isolates have more intense fluoroquinolone resistance than other fluoroquinolone-resistantE. coliisolates and to identify possible mechanisms, we determined the MICs for four fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin, and norfloxacin) among 89 well-characterized, genetically diverse fluoroquinolone-resistantE. coliisolates (48 non-H30 and 41H30 [23H30Rx and 18H30 non-Rx]). We compared the MICs with theH30 andH30Rx status, the presence/number of nonsynonymous mutations ingyrA,parC, andparE, the presence ofaac(6′)-1b-cr(an aminoglycoside/fluoroquinolone agent-modifying enzyme), and the efflux pump activity (measured as organic solvent tolerance [OST]). Among 1,518 recentE. coliclinical isolates, ST131H30 predominated clonally, both overall and among the fluoroquinolone-resistant isolates. Among the 89 study isolates, compared with non-H30 isolates,H30 isolates exhibited categorically higher MICs for all four fluoroquinolone agents, higher absolute ciprofloxacin and norfloxacin MICs, more nonsynonymous mutations ingyrA,parC, andparE(specificallygyrAD87N,parCE84V, andparEI529L), and a numerically higher prevalence of (H30Rx-associated)aac(6′)-1b-crbut lower OST scores. All putative resistance mechanisms were significantly associated with the MICs [foraac(6′)-1b-cr: ciprofloxacin and norfloxacin only].parCD87N corresponded with ST131H30 andparEI529L with ST131 generally. Thus, more intense fluoroquinolone resistance may provide ST131H30, especiallyH30Rx [ifaac(6′)-1b-crpositive], with subtle fitness advantages over other fluoroquinolone-resistantE. colistrains. This urges both parsimonious fluoroquinolone use and a search for other fitness-enhancing traits within ST131H30.

scholarly journals Tigecycline Nonsusceptibility Occurs Exclusively in Fluoroquinolone-Resistant Escherichia coli Clinical Isolates, Including the Major Multidrug-Resistant Lineages O25b:H4-ST131-H30R and O1-ST648

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Toyotaka Sato ◽  
Yuuki Suzuki ◽  
Tsukasa Shiraishi ◽  
Hiroyuki Honda ◽  
Masaaki Shinagawa ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Parental Strain ◽  
Efflux Pump ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Content Type ◽  
E Coli ◽  
Line Drug

ABSTRACT Tigecycline (TGC) is a last-line drug for multidrug-resistant Enterobacteriaceae. We investigated the mechanism(s) underlying TGC nonsusceptibility (TGC resistant/intermediate) in Escherichia coli clinical isolates. The MIC of TGC was determined for 277 fluoroquinolone-susceptible isolates (ciprofloxacin [CIP] MIC, <0.125 mg/liter) and 194 fluoroquinolone-resistant isolates (CIP MIC, >2 mg/liter). The MIC50 and MIC90 for TGC in fluoroquinolone-resistant isolates were 2-fold higher than those in fluoroquinolone-susceptible isolates (MIC50, 0.5 mg/liter versus 0.25 mg/liter; MIC90, 1 mg/liter versus 0.5 mg/liter, respectively). Two fluoroquinolone-resistant isolates (O25b:H4-ST131-H30R and O125:H37-ST48) were TGC resistant (MICs of 4 and 16 mg/liter, respectively), and four other isolates of O25b:H4-ST131-H30R and an isolate of O1-ST648 showed an intermediate interpretation (MIC, 2 mg/liter). No TGC-resistant/intermediate strains were found among the fluoroquinolone-susceptible isolates. The TGC-resistant/intermediate isolates expressed higher levels of acrA and acrB and had lower intracellular TGC concentrations than susceptible isolates, and they possessed mutations in acrR and/or marR. The MICs of acrAB-deficient mutants were markedly lower (0.25 mg/liter) than those of the parental strain. After continuous stepwise exposure to CIP in vitro, six of eight TGC-susceptible isolates had reduced TGC susceptibility. Two of them acquired TGC resistance (TGC MIC, 4 mg/liter) and exhibited expression of acrA and acrB and mutations in acrR and/or marR. In conclusion, a population of fluoroquinolone-resistant E. coli isolates, including major extraintestinal pathogenic lineages O25b:H4-ST131-H30R and O1-ST648, showed reduced susceptibility to TGC due to overexpression of the efflux pump AcrAB-TolC, leading to decreased intracellular concentrations of the antibiotics that may be associated with the development of fluoroquinolone resistance.

Topoisomerase mutations and efflux are associated with fluoroquinolone resistance in Enterococcus faecalis

2006 ◽  
Vol 55 (10) ◽  
pp. 1395-1401 ◽  
Author(s):  
Yoshihiro Oyamada ◽  
Hideaki Ito ◽  
Matsuhisa Inoue ◽  
Jun-ichi Yamagishi
Keyword(s):  
Enterococcus Faecalis ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Fluoroquinolone Resistance ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Topoisomerase Iv ◽  
Gram Positive Bacteria ◽  
Efflux Pump Inhibitors ◽  
Resistant Mutants

To understand better the mechanisms of fluoroquinolone resistance in Enterococcus faecalis, fluoroquinolone-resistant mutants isolated from Ent. faecalis ATCC 29212 by stepwise selection with sparfloxacin (SPX) and norfloxacin (NOR) were analysed. The results showed the following. (i) In general, fluoroquinolone-resistance mechanisms in Ent. faecalis are similar to those in other Gram-positive bacteria, such as Staphylococcus aureus and Streptococcus pneumoniae, namely, mutants with amino acid changes in both GyrA and ParC exhibited high fluoroquinolone resistance, and single GyrA mutants and a single ParC mutant were more resistant to SPX and NOR, respectively, than the parent strain, indicating that the primary targets of SPX and NOR in Ent. faecalis are DNA gyrase and topoisomerase IV, respectively. (ii) Alterations in GyrB (ΔKGA, residues 395–397) and ParE (Glu-459 to Lys) were associated with fluoroquinolone resistance in some mutants. Moreover, the facts that the NOR MIC, but not the SPX MIC, decreased in the presence of multidrug efflux pump inhibitors, that NOR accumulation decreased in the cells, and that the EmeA mRNA expression level did not change, strongly suggested that a NorA-like efflux pump, rather than EmeA, was involved in resistance to NOR.

scholarly journals Post-Covid-19 Era: What is Next?

2021 ◽  
Author(s):  
Shiela Chetri
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Carbapenem Resistance ◽  
Resistance Mechanisms ◽  
Multidrug Efflux Pump ◽  
High Risk Factors ◽  
Clinical Complications

Antimicrobial resistance (AMR) is a natural phenomenon in bacteria which becomes a threat for health-care settings around the world. A concerted global response is needed to tackle rising rates of antibiotic resistance, without it we risk returning to the pre antibiotic era. As bacteria evolve very fast according to the environment in which they inhabit via developing different defence mechanisms to combat with the noxious agents like different classes of antibiotics including carbapenems. This results into treatment failure and clinical complications. Global emergence of antibiotic resistance due to bacterial multidrug efflux pump systems are a major and common mechanism of intrinsic antimicrobial resistance employed by bacteria which are spreading rapidly due to over use or misuse of antimicrobial agents. This review mainly focusses on the transcriptional expression of efflux pump system AcrAB-TolC, local regulatory genes (AcrR and AcrS), mediating carbapenem resistance in clinical isolates of Escherichia coli under antibiotic stress, a genetic interplay study between intrinsic and acquired antibiotic resistance mechanisms along with a brief summary on high risk factors and prevalence of urinary tract infections by multidrug resistant Uropathogenic Escherichia coli.

scholarly journals Klebsiella pneumoniae Major Porins OmpK35 and OmpK36 Allow More Efficient Diffusion of β-Lactams than Their Escherichia coli Homologs OmpF and OmpC

2016 ◽  
Vol 198 (23) ◽  
pp. 3200-3208 ◽  
Author(s):  
Etsuko Sugawara ◽  
Seiji Kojima ◽  
Hiroshi Nikaido
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Fourth Generation ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Content Type

ABSTRACTKlebsiella pneumoniae, one of the most important nosocomial pathogens, is becoming a major problem in health care because of its resistance to multiple antibiotics, including cephalosporins of the latest generation and, more recently, even carbapenems. This is largely due to the spread of plasmid-encoded extended-spectrum β-lactamases. However, antimicrobial agents must first penetrate the outer membrane barrier in order to reach their targets, and hydrophilic and charged β-lactams presumably diffuse through the porin channels. Unfortunately, the properties ofK. pneumoniaeporin channels are largely unknown. In this study, we made clean deletions ofK. pneumoniaeporin genesompK35andompK36and examined the antibiotic susceptibilities and diffusion rates of β-lactams. The results showed that OmpK35 and OmpK36 produced larger more permeable channels than theirEscherichia colihomologs OmpF and OmpC; OmpK35 especially produced a diffusion channel of remarkably high permeability toward lipophilic (benzylpenicillin) and large (cefepime) compounds. These results were also confirmed by expressing various porins in anE. colistrain lacking major porins and the major multidrug efflux pump AcrAB. Our data explain why the development of drug resistance inK. pneumoniaeis so often accompanied by the mutational loss of its porins, especially OmpK35, in addition to the various plasmid-carried genes of antibiotic resistance, because even hydrolysis by β-lactamases becomes inefficient in producing high levels of resistance if the bacterium continues to allow a rapid influx of β-lactams through its wide porin channels.IMPORTANCEIn Gram-negative bacteria, drugs must first enter the outer membrane, usually through porin channels. Thus, the quantitative examination of influx rates is essential for the assessment of resistance mechanisms, yet no such studies exist for a very important nosocomial pathogen,Klebsiella pneumoniae. We found that the larger channel porin of this organism, OmpK35, produces a significantly larger channel than itsEscherichia colihomolog, OmpF. This makes unmodifiedK. pneumoniaestrains more susceptible to relatively large antibiotics, such as the third- and fourth-generation cephalosporins. Also, even the acquisition of powerful β-lactamases is not likely to make them fully resistant in the presence of such an effective influx process, explaining why so many clinical isolates of this organism lack porins.

scholarly journals oqxAB Encoding a Multidrug Efflux Pump in Human Clinical Isolates of Enterobacteriaceae

2009 ◽  
Vol 53 (8) ◽  
pp. 3582-3584 ◽  
Author(s):  
Hong Bin Kim ◽  
Minghua Wang ◽  
Chi Hye Park ◽  
Eui-Chong Kim ◽  
George A. Jacoby ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Efflux Pump ◽  
Clinical Isolates ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump

ABSTRACT The genes for multidrug efflux pump OqxAB, which is active on fluoroquinolones, were found in human clinical isolates on a plasmid in Escherichia coli and on the chromosome of Klebsiella pneumoniae. IS26-like sequences flanked the plasmid-mediated oqxAB genes, suggesting that they had been mobilized as part of a composite transposon.

scholarly journals Heterogeneous and Flexible Transmission ofmcr-1in Hospital-AssociatedEscherichia coli

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Yingbo Shen ◽  
Zuowei Wu ◽  
Yang Wang ◽  
Rong Zhang ◽  
Hong-Wei Zhou ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genomic Analysis ◽  
Multidrug Resistant ◽  
Fluoroquinolone Resistance ◽  
Gram Negative Bacteria ◽  
Colistin Resistance ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Genes Encoding

ABSTRACTThe recent emergence of a transferable colistin resistance mechanism, MCR-1, has gained global attention because of its threat to clinical treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, the possible transmission route ofmcr-1amongEnterobacteriaceaespecies in clinical settings is largely unknown. Here, we present a comprehensive genomic analysis ofEscherichia coliisolates collected in a hospital in Hangzhou, China. We found thatmcr-1-carrying isolates from clinical infections and feces of inpatients and healthy volunteers were genetically diverse and were not closely related phylogenetically, suggesting that clonal expansion is not involved in the spread ofmcr-1. Themcr-1gene was found on either chromosomes or plasmids, but in most of theE. coliisolates,mcr-1was carried on plasmids. The genetic context of the plasmids showed considerable diversity as evidenced by the different functional insertion sequence (IS) elements, toxin-antitoxin (TA) systems, heavy metal resistance determinants, and Rep proteins of broad-host-range plasmids. Additionally, the genomic analysis revealed nosocomial transmission ofmcr-1and the coexistence ofmcr-1with other genes encoding β-lactamases and fluoroquinolone resistance in theE. coliisolates. These findings indicate thatmcr-1is heterogeneously disseminated in both commensal and pathogenic strains ofE. coli, suggest the high flexibility of this gene in its association with diverse genetic backgrounds of the hosts, and provide new insights into the genome epidemiology ofmcr-1among hospital-associatedE. colistrains.IMPORTANCEColistin represents one of the very few available drugs for treating infections caused by extensively multidrug-resistant Gram-negative bacteria. The recently emergentmcr-1colistin resistance gene threatens the clinical utility of colistin and has gained global attention. Howmcr-1spreads in hospital settings remains unknown and was investigated by whole-genome sequencing ofmcr-1-carryingEscherichia coliin this study. The findings revealed extraordinary flexibility ofmcr-1in its spread among genetically diverseE. colihosts and plasmids, nosocomial transmission ofmcr-1-carryingE. coli, and the continuous emergence of novel Inc types of plasmids carryingmcr-1and newmcr-1variants. Additionally,mcr-1was found to be frequently associated with other genes encoding β-lactams and fluoroquinolone resistance. These findings provide important information on the transmission and epidemiology ofmcr-1and are of significant public health importance as the information is expected to facilitate the control of this significant antibiotic resistance threat.

scholarly journals EfrAB, an ABC Multidrug Efflux Pump in Enterococcus faecalis

2003 ◽  
Vol 47 (12) ◽  
pp. 3733-3738 ◽  
Author(s):  
Eun-Woo Lee ◽  
M. Nazmul Huda ◽  
Teruo Kuroda ◽  
Tohru Mizushima ◽  
Tomofusa Tsuchiya
Keyword(s):  
Enterococcus Faecalis ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Amino Acid Sequences ◽  
Open Reading Frames ◽  
Multidrug Efflux ◽  
Chromosomal Dna ◽  
Multidrug Efflux Pump ◽  
E Coli ◽  
Dna Fragment

ABSTRACT A DNA fragment responsible for resistance to antimicrobial agents was cloned from the chromosomal DNA of Enterococcus faecalis ATCC 29212 by using drug-hypersensitive mutant Escherichia coli KAM32 as a host cell. Cells of E. coli KAM32 harboring a recombinant plasmid (pAEF82) carrying the DNA fragment became resistant to many structurally unrelated antimicrobial agents, such as norfloxacin, ciprofloxacin, doxycycline, acriflavine, 4′,6-diamidino-2-phenylindole, tetraphenylphosphonium chloride, daunorubicin, and doxorubicin. Since the sequence of the whole genome of E. faecalis is known, we sequenced several portions of the DNA insert in plasmid pAEF82 and identified two open reading frames within the insert. We designated the genes efrA and efrB. A search of the deduced amino acid sequences of EfrA and EfrB revealed that they are similar to each other and that they belong to the ATP-binding cassette (ABC) family of multidrug efflux transporters. Transformed E. coli KAM32 cells harboring efrAB showed energy-dependent efflux of acriflavine. The efflux activity was inhibited by reserpine, verapamil, and sodium-o-vanadate, known inhibitors of ABC efflux pumps.

Antimicrobial Resistance and Association with Class 1 Integrons in Escherichia coli Isolated from Turkey Meat Products

2008 ◽  
Vol 71 (8) ◽  
pp. 1679-1684 ◽  
Author(s):  
M. L. KHAITSA ◽  
J. OLOYA ◽  
D. DOETKOTT ◽  
R. KEGODE
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Population Attributable Fraction ◽  
Meat Products ◽  
Resistance Mechanisms ◽  
E Coli ◽  
Class 1 Integrons ◽  
Turkey Meat ◽  
Class 1

The objective of this study was to quantify the role of class 1 integrons in antimicrobial resistance in Escherichia coli isolated from turkey meat products purchased from retail outlets in the Midwestern United States. Of 242 E. coli isolates, 41.3% (102 of 242) tested positive for class 1 integrons. A significant association was shown between presence of class 1 integrons in E. coli isolates and the resistance to tetracycline, ampicillin, streptomycin, gentamicin, sulfisoxazole, and trimethoprim-sulfamethoxazole. Attributable risk analysis revealed that for every 100 E. coli isolates carrying class 1 integrons, resistance was demonstrated for ampicillin (22%), gentamycin (48%), streptomycin (29%), sulfisoxazole (40%), trimethoprimsulfamethoxazole (7%), and tetracycline (26%). Non–integron-related antimicrobial resistance was demonstrated for ampicillin (65%), gentamycin (16.9%), streptomycin (42.1%), sulfisoxazole (35.8%), and tetracycline (49.7%). Population-attributable fraction analysis showed that class 1 integrons accounted for the following resistances: gentamycin, 71% (50 of 71), amoxicillin–clavulanic acid, 19.6% (6 of 33), nalidixic acid, 34% (7 of 21), streptomycin, 28% (30 of 107), sulfisoxazole, 38% (40 of 106), and tetracycline, 14%, (26 of 185). In conclusion, although class 1 integrons have been implicated in resistance to antimicrobial agents, other non–integron resistance mechanisms seem to play an important part.

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