scholarly journals RamA, a transcriptional regulator conferring florfenicol resistance in Leclercia adecarboxylata R25

2020 ◽  
Vol 65 (6) ◽  
pp. 1051-1060
Author(s):  
Cong Cheng ◽  
Yuanyuan Ying ◽  
Danying Zhou ◽  
Licheng Zhu ◽  
Junwan Lu ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Efflux Pump ◽  
Gene Knockout ◽  
Regulatory Gene ◽  
Resistance Mechanism ◽  
Agricultural Practice ◽  
The Novel ◽  
Inappropriate Use ◽  
Rnd Efflux Pump ◽  
High Level

AbstractDue to the inappropriate use of florfenicol in agricultural practice, florfenicol resistance has become increasingly serious. In this work, we studied the novel florfenicol resistance mechanism of an animal-derived Leclercia adecarboxylata strain R25 with high-level florfenicol resistance. A random genomic DNA library was constructed to screen the novel florfenicol resistance gene. Gene cloning, gene knockout, and complementation combined with the minimum inhibitory concentration (MIC) detection were conducted to determine the function of the resistance-related gene. Sequencing and bioinformatics methods were applied to analyze the structure of the resistance gene-related sequences. Finally, we obtained a regulatory gene of an RND (resistance-nodulation-cell division) system, ramA, that confers resistance to florfenicol and other antibiotics. The ramA-deleted variant (LA-R25ΔramA) decreased the level of resistance against florfenicol and several other antibiotics, while a ramA-complemented strain (pUCP24-prom-ramA/LA-R25ΔramA) restored the drug resistance. The whole-genome sequencing revealed that there were five RND efflux pump genes (mdtABC, acrAB, acrD, acrEF, and acrAB-like) encoded over the chromosome, and ramA located upstream of the acrAB-like genes. The results of this work suggest that ramA confers resistance to florfenicol and other structurally unrelated antibiotics, presumably by regulating the RND efflux pump genes in L. adecarboxylata R25.

scholarly journals Triclosan resistance in clinical isolates of Acinetobacter baumannii

2009 ◽  
Vol 58 (8) ◽  
pp. 1086-1091 ◽  
Author(s):  
Yagang Chen ◽  
Borui Pi ◽  
Hua Zhou ◽  
Yunsong Yu ◽  
Lanjuan Li
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Active Efflux ◽  
Low Level ◽  
High Level ◽  
Resistance Rates ◽  
Triclosan Resistance

The susceptibility to triclosan of 732 clinical Acinetobacter baumannii isolates obtained from 25 hospitals in 16 cities in China from December 2004 to December 2005 was screened by using an agar dilution method. Triclosan MICs ranged between 0.015 and 16 mg l−1, and the MIC90 was 0.5 mg l−1, lower than the actual in-use concentration of triclosan. Twenty triclosan-resistant isolates (MICs ≥1 mg l−1) were characterized by antibiotic susceptibility, clonal relatedness, fabI mutation, fabI expression, and efflux pump phenotype and expression to elucidate the resistance mechanism of A. baumannii to triclosan. The resistance rates of triclosan-resistant isolates to imipenem, levofloxacin, amikacin and tetracycline were higher than those of triclosan-sensitive isolates. Triclosan resistance was artificially classified as low level (MICs 1–2 mg l−1) or high level (MICs ≥4 mg l−1). High-level triclosan resistance could be explained by a Gly95Ser mutation of FabI, whilst wild-type fabI was observed to be overexpressed in low-level resistant isolates. Active efflux did not appear to be a major reason for acquired triclosan resistance, but acquisition of resistance appeared to be dependent on a background of intrinsic triclosan efflux.

scholarly journals Efflux-Related Resistance to Norfloxacin, Dyes, and Biocides in Bloodstream Isolates of Staphylococcus aureus

2007 ◽  
Vol 51 (9) ◽  
pp. 3235-3239 ◽  
Author(s):  
Carmen E. DeMarco ◽  
Laurel A. Cushing ◽  
Emmanuel Frempong-Manso ◽  
Susan M. Seo ◽  
Tinevimbo A. A. Jaravaza ◽  
...  
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Efflux Pump Inhibitor ◽  
Qrt Pcr ◽  
Reverse Transcription Pcr ◽  
Environmental Surfaces ◽  
Genes Encoding ◽  
High Level

ABSTRACT Efflux is an important resistance mechanism in Staphylococcus aureus, but its frequency in patients with bacteremia is unknown. Nonreplicate bloodstream isolates were collected over an 8-month period, and MICs of four common efflux pump substrates, with and without the broad-spectrum efflux pump inhibitor reserpine, were determined (n = 232). A reserpine-associated fourfold decrease in MIC was considered indicative of efflux. Strains exhibiting efflux of at least two of the four substrates were identified (“effluxing strains” [n = 114]). For these strains, MICs with or without reserpine for an array of typical substrates and the expression of mepA, mdeA, norA, norB, norC, and qacA/B were determined using quantitative real-time reverse transcription-PCR (qRT-PCR). A fourfold or greater increase in gene expression was considered significant. The most commonly effluxed substrates were ethidium bromide and chlorhexidine (100 and 96% of effluxing strains, respectively). qRT-PCR identified strains overexpressing mepA (5 [4.4%]), mdeA (13 [11.4%]), norA (26 [22.8%]), norB (29 [25.4%]), and norC (19 [16.7%]); 23 strains overexpressed two or more genes. Mutations probably associated with increased gene expression included a MepR-inactivating substitution and norA promoter region insertions or deletions. Mutations possibly associated with increased expression of the other analyzed genes were also observed. Effluxing strains comprised 49% of all strains studied (114/232 strains), with nearly half of these overexpressing genes encoding MepA, MdeA, and/or NorABC (54/114 strains). Reduced susceptibility to biocides may contribute to persistence on environmental surfaces, and efflux of drugs such as fluoroquinolones may predispose strains to high-level target-based resistance.

Tigecycline efflux in Acinetobacter baumannii is mediated by TetA in synergy with RND-type efflux transporters

2020 ◽  
Vol 75 (5) ◽  
pp. 1135-1139 ◽  
Author(s):  
Wuen Ee Foong ◽  
Jochen Wilhelm ◽  
Heng-Keat Tam ◽  
Klaas M Pos
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Gene Knockout ◽  
Drug Susceptibility ◽  
Major Facilitator Superfamily ◽  
Rt Pcr ◽  
E Coli ◽  
Rnd Efflux Pump ◽  
Major Facilitator

Abstract Objectives To investigate the role of Major Facilitator Superfamily (MFS)-type transporters from Acinetobacter baumannii AYE in tigecycline efflux. Methods Two putative tetracycline transporter genes of A. baumannii AYE (tetA and tetG) were heterologously expressed in Escherichia coli and drug susceptibility assays were conducted with tigecycline and three other tetracycline derivatives. The importance of TetA in tigecycline transport in A. baumannii was determined by complementation of tetA in WT and Resistance Nodulation cell Division (RND) gene knockout strains of A. baumannii ATCC 19606. Gene expression of the MFS-type tetA gene and RND efflux pump genes adeB, adeG and adeJ in A. baumannii AYE in the presence of tigecycline was analysed by quantitative real-time RT–PCR. Results Overproduction of TetA or TetG conferred resistance to doxycycline, minocycline and tetracycline in E. coli. Cells expressing tetA, but not those expressing tetG, conferred resistance to tigecycline, implying that TetA is a determinant for tigecycline transport. A. baumannii WT and RND-knockout strains complemented with plasmid-encoded tetA are significantly less susceptible to tigecycline compared with non-complemented strains. Efflux pump genes tetA and adeG are up-regulated in A. baumannii AYE in the presence of subinhibitory tigecycline concentrations. Conclusions TetA plays an important role in tigecycline efflux of A. baumannii by removing the drug from cytoplasm to periplasm and, subsequently, the RND-type transporters AdeABC and AdeIJK extrude tigecycline across the outer membrane. When challenged with tigecycline, tetA is up-regulated in A. baumannii AYE. Synergy between TetA and the RND-type transporters AdeABC and/or AdeIJK appears necessary for A. baumannii to confer higher tigecycline resistance via drug efflux.

scholarly journals Effect of MexXY Overexpression on Ceftobiprole Susceptibility in Pseudomonas aeruginosa

2009 ◽  
Vol 53 (7) ◽  
pp. 2785-2790 ◽  
Author(s):  
Ellen Z. Baum ◽  
Steven M. Crespo-Carbone ◽  
Brian J. Morrow ◽  
Todd A. Davies ◽  
Barbara D. Foleno ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Broad Spectrum ◽  
Efflux Pump ◽  
Regulatory Gene ◽  
Resistance Mechanism ◽  
Common Mechanism ◽  
Spontaneous Mutant ◽  
Minimal Effect ◽  
Strain Pao1

ABSTRACT Ceftobiprole, an anti-methicillin-resistant Staphylococcus aureus broad-spectrum cephalosporin, has activity (MIC for 50% of strains tested, ≤4 μg/ml) against many Pseudomonas aeruginosa strains. A common mechanism of P. aeruginosa resistance to β-lactams, including cefepime and ceftazidime, is efflux via increased expression of Mex pumps, especially MexAB. MexXY has differential substrate specificity, recognizing cefepime but not ceftazidime. In ceftobiprole clinical studies, paired isolates of P. aeruginosa from four subjects demonstrated ceftobiprole MICs of 2 to 4 μg/ml at baseline but 16 μg/ml posttreatment, unrelated to β-lactamase levels. Within each pair, the level of mexXY RNA, but not mexAB, mexCD, and mexEF, increased by an average of 50-fold from baseline to posttreatment isolates. Sequencing of the negative regulatory gene mexZ indicated that each posttreatment isolate contained a mutation not present at baseline. mexXY expression as a primary ceftobiprole and cefepime resistance mechanism was further examined in isogenic pairs by using cloned mexXY and mexZ. Expression of cloned mexXY in strain PAO1 or in a baseline isolate increased the ceftobiprole MIC to that for the posttreatment isolate. In contrast, in posttreatment isolates, lowering mexXY expression via introduction of cloned mexZ decreased the ceftobiprole MIC to that for the baseline isolates. Similar changes were observed for cefepime. A spontaneous mutant selectively overexpressing mexXY displayed a fourfold elevation in its ceftobiprole MIC, while overexpression of mexAB, -CD, and -EF had a minimal effect. These data indicate that ceftobiprole, like cefepime, is an atypical β-lactam that is a substrate for the MexXY efflux pump in P. aeruginosa.

scholarly journals Characterization of TMexCD3-TOprJ3, an RND-type efflux system conferring resistance to tigecycline in Proteus mirabilis, and its associated Integrative Conjugative Element

2021 ◽  
Author(s):  
Qian Wang ◽  
Kai Peng ◽  
Yuan Liu ◽  
Xia Xiao ◽  
Zhiqiang Wang ◽  
...  
Keyword(s):  
Proteus Mirabilis ◽  
Efflux Pump ◽  
Current Knowledge ◽  
Gene Clusters ◽  
The Novel ◽  
Genomic Epidemiology ◽  
Integrative Conjugative Element ◽  
Antimicrobial Resistance Genes ◽  
Rnd Efflux Pump

The emergence and transmission of novel antimicrobial resistance genes pose a great threat to public health globally. Recently, the plasmid-encoding RND efflux pump TMexCD1-TOprJ1 in Klebsiella pneumoniae was reported to reduce the sensitivity of multiple antimicrobials. Herein, we identified a pandrug-resistant Proteus mirabilis isolate, which harbored the novel tmexCD3-toprJ3 gene cluster located on SXT/R391 ICE. This study expands current knowledge in transfer mechanism of tmexCD1-toprJ1-like gene clusters among P. mirabilis and warrant further genomic epidemiology investigations.

scholarly journals Transferable Multidrug-Resistance Plasmid Carrying a Novel Macrolide-Clindamycin Resistance Gene, erm(50), in Cutibacterium acnes

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Sae Aoki ◽  
Keisuke Nakase ◽  
Hidemasa Nakaminami ◽  
Takeaki Wajima ◽  
Nobukazu Hayashi ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Acne Vulgaris ◽  
Tetracycline Resistance ◽  
23S Rrna ◽  
The Novel ◽  
Content Type ◽  
Resistance Determinants ◽  
Cutibacterium Acnes ◽  
High Level ◽  
Rrna Mutation

ABSTRACT Antimicrobial-resistant Cutibacterium acnes strains have emerged and disseminated throughout the world. The 23S rRNA mutation and erm(X) gene are known as the major resistance determinants of macrolides and clindamycin in C. acnes. We isolated eight high-level macrolide-clindamycin-resistant C. acnes strains with no known resistance determinants, such as 23S rRNA mutation and erm(X), from different acne patients in 2008 between 2013 and 2015. The aim of this study was to identify the novel mechanisms of resistance in C. acnes. Whole-genome sequencing revealed the existence of a plasmid DNA, denoted pTZC1 (length, 31,440 bp), carrying the novel macrolide-clindamycin resistance gene erm(50) and tetracycline resistance gene tet(W). pTZC1 was detected in all C. acnes isolates (eight strains) exhibiting high-level macrolide-clindamycin resistance, with no known resistance determinants (MIC of clarithromycin, ≥256 μg/ml; clindamycin, ≥256 μg/ml). Transconjugation experiments demonstrated that the pTZC1 was horizontally transferred among C. acnes strains and conferred resistance to macrolides, clindamycin, and tetracyclines. Our data showed, for the first time, the existence of a transferable multidrug-resistant plasmid in C. acnes. Increased prevalence of this plasmid will be a great threat to antimicrobial therapy for acne vulgaris.

scholarly journals Plasmid-Mediated OqxAB Is an Important Mechanism for Nitrofurantoin Resistance in Escherichia coli

2015 ◽  
Vol 60 (1) ◽  
pp. 537-543 ◽  
Author(s):  
Pak-Leung Ho ◽  
Ka-Ying Ng ◽  
Wai-U Lo ◽  
Pierra Y. Law ◽  
Eileen Ling-Yi Lai ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Efflux Pump ◽  
Geometric Mean ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Content Type ◽  
E Coli ◽  
High Level ◽  
Tract Infections

ABSTRACTIncreasing consumption of nitrofurantoin (NIT) for treatment of acute uncomplicated urinary tract infections (UTI) highlights the need to monitor emerging NIT resistance mechanisms. This study investigated the molecular epidemiology of the multidrug-resistant efflux geneoqxABand its contribution to nitrofurantoin resistance by usingEscherichia coliisolates originating from patients with UTI (n= 205; collected in 2004 to 2013) and food-producing animals (n= 136; collected in 2012 to 2013) in Hong Kong. TheoqxABgene was highly prevalent among NIT-intermediate (11.5% to 45.5%) and -resistant (39.2% to 65.5%) isolates but rare (0% to 1.7%) among NIT-susceptible (NIT-S) isolates. In our isolates, theoqxABgene was associated with IS26and was carried by plasmids of diverse replicon types. Multilocus sequence typing revealed that the clones ofoqxAB-positiveE. coliwere diverse. The combination ofoqxABandnfsAmutations was found to be sufficient for high-level NIT resistance. Curing ofoqxAB-carrying plasmids from 20 NIT-intermediate/resistant UTI isolates markedly reduced the geometric mean MIC of NIT from 168.9 μg/ml to 34.3 μg/ml. In the plasmid-cured variants, 20% (1/5) of isolates withnfsAmutations were NIT-S, while 80% (12/15) of isolates withoutnfsAmutations were NIT-S (P= 0.015). The presence of plasmid-basedoqxABincreased the mutation prevention concentration of NIT from 128 μg/ml to 256 μg/ml and facilitated the development of clinically important levels of nitrofurantoin resistance. In conclusion, plasmid-mediatedoqxABis an important nitrofurantoin resistance mechanism. There is a great need to monitor the dissemination of this transferable multidrug-resistant efflux pump.

scholarly journals Fluoroquinolone resistance conferred by gyrA, parC mutations, and AbaQ efflux pump among Acinetobacter baumannii clinical isolates causing ventilator-associated pneumonia

2019 ◽  
pp. 1-5 ◽  
Author(s):  
Nancy M. Attia ◽  
Amira ElBaradei
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Quinolone Resistance ◽  
Fluoroquinolone Resistance ◽  
Ventilator Associated Pneumonia ◽  
Drug Resistant ◽  
The Novel ◽  
New Mutation ◽  
Extensively Drug Resistant ◽  
High Level

Acinetobacter baumannii has emerged as an important nosocomial pathogen due to its ability to survive in hospital settings and its antimicrobial resistance. It is one of the key pathogens in ventilator-associated pneumonia (VAP). The aim of this study was to characterize the mechanisms of quinolone resistance among A. baumannii isolates causing VAP and to investigate the presence of the novel abaQ gene among them. Quinolone-resistant A. baumannii isolates causing VAP were collected over a period of 4 months. Mutations within gyrA and parC were analyzed and the presence of qnrA, qnrB, qnrS, and abaQ was investigated genotypically. Twenty-one A. baumannii isolates were collected, most of them (76.2%) were extensively drug-resistant (XDR) and only one isolate (4.8%) was pandrug-resistant (PDR). All isolates showed high level of resistance to ciprofloxacin, while qnrA, qnrB and qnrS were absent among our isolates. This is the first report of A. baumannii isolates co-harboring Ser81Leu in gyrA and Ser84Leu in parC together with the novel abaQ gene. Interestingly, a new mutation in gyrA quinolone resistance-determining region Arg89Cys was detected among two of our isolates. The emergence of XDR and PDR isolates among A. baumannii causing VAP is an alarming threat.

scholarly journals Plasmid-Mediated 16S rRNA Methylase in Serratia marcescens Conferring High-Level Resistance to Aminoglycosides

2004 ◽  
Vol 48 (2) ◽  
pp. 491-496 ◽  
Author(s):  
Yohei Doi ◽  
Keiko Yokoyama ◽  
Kunikazu Yamane ◽  
Jun-ichi Wachino ◽  
Naohiro Shibata ◽  
...  
Keyword(s):  
16S Rrna ◽  
Serratia Marcescens ◽  
Resistance Gene ◽  
Pathogenic Bacteria ◽  
Treatment Options ◽  
Resistance Mechanism ◽  
Aminoglycoside Resistance ◽  
Reading Frame ◽  
High Level ◽  
16S Rrna Methylase

ABSTRACT Serratia marcescens S-95, which displayed an unusually high degree of resistance to aminoglycosides, including kanamycins and gentamicins, was isolated in 2002 from a patient in Japan. The resistance was mediated by a large plasmid which was nonconjugative but transferable to an Escherichia coli recipient by transformation. The gene responsible for the aminoglycoside resistance was cloned and sequenced. The deduced amino acid sequence of the resistance gene shared 82% identity with RmtA, which was recently identified as 16S rRNA methylase conferring high-level aminoglycoside resistance in Pseudomonas aeruginosa. Histidine-tagged recombinant protein showed methylation activity against E. coli 16S rRNA. The novel aminoglycoside resistance gene was therefore designated rmtB. The genetic environment of rmtB was further investigated. The sequence immediately upstream of rmtB contained the right end of transposon Tn3, including bla TEM, while an open reading frame possibly encoding a transposase was identified downstream of the gene. This is the first report describing 16S rRNA methylase production in S. marcescens. The aminoglycoside resistance mechanism mediated by production of 16S rRNA methylase and subsequent ribosomal protection used to be confined to aminoglycoside-producing actinomycetes. However, it is now identified among pathogenic bacteria, including Enterobacteriaceae and P. aeruginosa in Japan. This is a cause for concern since other treatment options are often limited in patients requiring highly potent aminoglycosides such as amikacin and tobramycin.

scholarly journals Resistance-Nodulation-Division Efflux Pump, LexABC, Contributes to Self-Resistance of the Phenazine Di-N-Oxide Natural Product Myxin in Lysobacter antibioticus

2021 ◽  
Vol 12 ◽  
Author(s):  
Yangyang Zhao ◽  
Jiayu Liu ◽  
Tianping Jiang ◽  
Rongxian Hou ◽  
Gaoge Xu ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Efflux Pump ◽  
Essential Gene ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Biosynthesis Gene Cluster ◽  
Regulatory Pathways ◽  
Redox Active ◽  
Resistance Nodulation Division ◽  
Rnd Efflux Pump

Antibiotic-producing microorganisms have developed several self-resistance mechanisms to protect them from autotoxicity. Transporters belonging to the resistance- nodulation-division (RND) superfamily commonly confer multidrug resistance in Gram-negative bacteria. Phenazines are heterocyclic, nitrogen-containing and redox-active compounds that exhibit diverse activities. We previously identified six phenazines from Lysobacter antibioticus OH13, a soil bacterium emerging as a potential biocontrol agent. Among these phenazines, myxin, a di-N-oxide phenazine, exhibited potent activity against a variety of microorganisms. In this study, we identified a novel RND efflux pump gene cluster, designated lexABC, which is located far away in the genome from the myxin biosynthesis gene cluster. We found a putative LysR-type transcriptional regulator encoding gene lexR, which was adjacent to lexABC. Deletion of lexABC or lexR gene resulted in significant increasing susceptibility of strains to myxin and loss of myxin production. The results demonstrated that LexABC pump conferred resistance against myxin. The myxin produced at lower concentrations in these mutants was derivatized by deoxidation and O-methylation. Furthermore, we found that the abolishment of myxin with deletion of LaPhzB, which is an essential gene in myxin biosynthesis, resulted in significant downregulation of the lexABC. However, exogenous supplementation with myxin to LaPhzB mutant could efficiently induce the expression of lexABC genes. Moreover, lexR mutation also led to decreased expression of lexABC, which indicates that LexR potentially positively modulated the expression of lexABC. Our findings reveal a resistance mechanism against myxin of L. antibioticus, which coordinates regulatory pathways to protect itself from autotoxicity.

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