scholarly journals AmpC β-Lactamases

2009 ◽  
Vol 22 (1) ◽  
pp. 161-182 ◽  
Author(s):  
George A. Jacoby
Keyword(s):  
Broad Spectrum ◽  
Efflux Pump ◽  
Clinical Laboratory ◽  
Resistance Mechanism ◽  
Enterobacter Aerogenes ◽  
Carbapenem Resistance ◽  
Enterobacter Cloacae ◽  
Outer Membrane Porin ◽  
The World ◽  
Plasmid Genes

SUMMARY AmpC β-lactamases are clinically important cephalosporinases encoded on the chromosomes of many of the Enterobacteriaceae and a few other organisms, where they mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and β-lactamase inhibitor-β-lactam combinations. In many bacteria, AmpC enzymes are inducible and can be expressed at high levels by mutation. Overexpression confers resistance to broad-spectrum cephalosporins including cefotaxime, ceftazidime, and ceftriaxone and is a problem especially in infections due to Enterobacter aerogenes and Enterobacter cloacae, where an isolate initially susceptible to these agents may become resistant upon therapy. Transmissible plasmids have acquired genes for AmpC enzymes, which consequently can now appear in bacteria lacking or poorly expressing a chromosomal blaAmpC gene, such as Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. Resistance due to plasmid-mediated AmpC enzymes is less common than extended-spectrum β-lactamase production in most parts of the world but may be both harder to detect and broader in spectrum. AmpC enzymes encoded by both chromosomal and plasmid genes are also evolving to hydrolyze broad-spectrum cephalosporins more efficiently. Techniques to identify AmpC β-lactamase-producing isolates are available but are still evolving and are not yet optimized for the clinical laboratory, which probably now underestimates this resistance mechanism. Carbapenems can usually be used to treat infections due to AmpC-producing bacteria, but carbapenem resistance can arise in some organisms by mutations that reduce influx (outer membrane porin loss) or enhance efflux (efflux pump activation).

scholarly journals Characterization of resistance mechanisms of Enterobacter cloacae Complex co-resistant to carbapenem and colistin

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Shixing Liu ◽  
Renchi Fang ◽  
Ying Zhang ◽  
Lijiang Chen ◽  
Na Huang ◽  
...  
Keyword(s):  
Lipid A ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Carbapenem Resistance ◽  
Enterobacter Cloacae ◽  
Resistance Mechanisms ◽  
Colistin Resistance ◽  
Carbapenem Resistant ◽  
Horizontal Spread

Abstract Background The emergence of carbapenem-resistant and colistin-resistant ECC pose a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in Enterobacter cloacae Complex (ECC) strains. Results This study showed that the mechanisms of carbapenem resistance in this study are: 1. Generating carbapenemase (7 of 19); 2. The production of AmpC or ESBLs combined with decreased expression of out membrane protein (12 of 19). hsp60 sequence analysis suggested 10 of 19 the strains belong to colistin hetero-resistant clusters and the mechanism of colistin resistance is increasing expression of acrA in the efflux pump AcrAB-TolC alone (18 of 19) or accompanied by a decrease of affinity between colistin and outer membrane caused by the modification of lipid A (14 of 19). Moreover, an ECC strain co-harboring plasmid-mediated mcr-4.3 and blaNDM-1 has been found. Conclusions This study suggested that there is no overlap between the resistance mechanism of co-resistant ECC strains to carbapenem and colistin. However, the emergence of strain co-harboring plasmid-mediated resistance genes indicated that ECC is a potential carrier for the horizontal spread of carbapenems and colistin resistance.

scholarly journals Characterization of resistance mechanisms of Enterobacter cloacae Complex Co-resistant to Carbapenem and Colistin

2020 ◽  
Author(s):  
Tieli Zhou ◽  
Shixing Liu ◽  
Renchi Fang ◽  
Ying Zhang ◽  
Lijiang Chen ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Lipid A ◽  
Efflux Pump ◽  
Medical Center ◽  
Resistance Mechanism ◽  
Carbapenem Resistance ◽  
Enterobacter Cloacae ◽  
Colistin Resistance ◽  
Carbapenemase Gene

Abstract Background: The emergence of carbapenem-resistant and colistin-resistant ECC pose a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in Enterobacter cloacae Complex (ECC) strains.Methods: Nineteen ECC isolates co-resistant to carbapenems and colistin were collected from a regional medical center in China. Carbapenemase gene, extended-spectrum β-lactamase gene, AmpC cephalosporinase gene ampC, mcr series genes, and ecr gene were detected by PCR. Expression levels of outer membrane protein OmpC/OmpF and efflux pump protein AcrA/AcrB were investigated. And the structural modification of lipid A of 19 ECC strains was analyzed.Results: This study showed that the mechanisms of carbapenem resistance in this study are: 1. Generating carbapenemase (7 of 19); 2. The production of AmpC or ESBLs combined with decreased expression of out membrane protein (12 of 19). And the mechanism of colistin resistance is increaseing expression of acrA in the efflux pump AcrAB-TolC alone (5 of 19) or accompanied by a decrease of affinity between colistin and outer membrane caused by the modification of lipid A (14 of 19). Moreover, an ECC strain co-harboring plasmid-mediated mcr-4.3 and blaNDM-1 has been found.Conclusions: This study suggested that there is no overlap between the resistance mechanism of co-resistant ECC strains to carbapenem and colistin. However, the emergence of strain co-harboring plasmid-mediated resistance genes indicated that ECC is a potential carrier for the horizontal spread of carbapenems and colistin resistance.

KPC-2 carbapenemase and DHA-1 AmpC determinants carried on the same plasmid in Enterobacter aerogenes

2014 ◽  
Vol 63 (3) ◽  
pp. 367-370 ◽  
Author(s):  
Shougang Kuai ◽  
Haifeng Shao ◽  
Lihua Huang ◽  
Hao Pei ◽  
Zhonghua Lu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Clinical Isolate ◽  
Southern Blotting ◽  
Antimicrobial Agents ◽  
Resistance Mechanism ◽  
Enterobacter Aerogenes ◽  
Carbapenem Resistance ◽  
Jiangsu Province ◽  
Republic Of China

This study was conducted to analyse the presence of a plasmid-mediated carbapenem resistance mechanism in a clinical Enterobacter aerogenes isolate from a patient from Jiangsu province, People’s Republic of China. PCR and sequencing confirmed that the isolate harboured Klebsiella pneumoniae carbapenemase (KPC)-2, DHA-1 and TEM-1 β-lactamase genes. Both the KPC-2 and DHA-1 genes were transferred to Escherichia coli C600 by transconjugation, and Southern blotting confirmed that these two genes were located on the same plasmid, which was of approximately 56 kb in size. The Enterobacter aerogenes isolate was resistant to carbapenems and other tested antimicrobial agents. The Escherichia coli transconjugant showed reduced susceptibility but not resistance to carbapenems and other β-lactams, indicating the presence of another, possibly permeability-related, resistance mechanism in the clinical isolate.

scholarly journals Characterization of IncHI1B Plasmids Encoding Efflux Pump TmexCD2-ToprJ2 in Carbapenem-Resistant Klebsiella variicola, Klebsiella quasipneumoniae, and Klebsiella michiganensis Strains

2021 ◽  
Vol 12 ◽  
Author(s):  
Yujiao Wang ◽  
Bo Zhu ◽  
Min Liu ◽  
Xiutao Dong ◽  
Jianping Ma ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Carbapenem Resistance ◽  
Health Concern ◽  
Close Monitoring ◽  
Carbapenem Resistant ◽  
Resistance Nodulation Division ◽  
Tertiary Hospitals ◽  
Severe Infections

Tigecycline serves as one of the last-resort antibiotics to treat severe infections caused by carbapenem-resistant Enterobacterales. Recently, a novel plasmid-mediated resistance-nodulation-division (RND)-type efflux pump gene cluster, TmexCD1-ToprJ1, and its variants, TmexCD2-ToprJ2 and TmexCD3-ToprJ3, encoding tetracyclines and tigecycline resistance, were revealed. In this study, we reported three TmexCD2-ToprJ2-harboring Klebsiella species strains, collected from two teaching tertiary hospitals in China, including one K. quasipneumoniae, one K. variicola, and one K. michiganensis. The three strains were characterized by antimicrobial susceptibility testing (AST), conjugation assay, WGS, and bioinformatics analysis. AST showed that K. variicola and K. quasipneumoniae strains were resistant to tigecycline with MIC values of 4μg/ml, whereas the K. michiganensis was susceptible to tigecycline with an MIC value of 1μg/ml. The TmexCD2-ToprJ2 clusters were located on three similar IncHI1B plasmids, of which two co-harbored the metallo-β-lactamase gene blaNDM-1. Conjugation experiments showed that all three plasmids were capable of self-transfer via conjugation. Our results showed, for the first time, that this novel plasmid-mediated tigecycline resistance mechanism TmexCD2-ToprJ2 has spread into different Klebsiella species, and clinical susceptibility testing may fail to detect. The co-occurrence of blaNDM-1 and TmexCD2-ToprJ2 in the same plasmid is of particular public health concern as the convergence of “mosaic” plasmids can confer both tigecycline and carbapenem resistance. Its further spread into other clinical high-risk Klebsiella clones will likely exacerbate the antimicrobial resistance crisis. A close monitoring of the dissemination of TmexCD-ToprJ encoding resistance should be considered.

scholarly journals Insights into the Resistome and Phylogenomics of a ST195 Multidrug-Resistant Acinetobacter baumannii Clinical Isolate from the Czech Republic

Life ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1079
Author(s):  
Patrik Mlynarcik ◽  
Monika Dolejska ◽  
Iva Vagnerova ◽  
Jana Petrzelova ◽  
Iva Sukkar ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Clinical Isolate ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Carbapenem Resistance ◽  
Multidrug Resistant ◽  
Clinical Settings ◽  
Sequencing Analysis ◽  
Pump System ◽  
The Czech Republic

Increasing antimicrobial resistance in nosocomial pathogens, such as Acinetobacter baumannii, is becoming a serious threat to public health. It is necessary to detect β-lactamase-producing microorganisms in clinical settings to be able to control the spread of carbapenem resistance. This study was conducted to evaluate the presence of β-lactamases in a selected clinical isolate of A. baumannii of ST2P/ST195Ox and to characterize possible enzymes, as well as its β-lactam resistome, using PCR and whole-genome sequencing analysis. PCR and sequencing confirmed that the isolate harbored five bla gene alleles, namely, blaADC-73, blaTEM-1, blaOXA-23, blaOXA-58 and blaOXA-66, as well as aminoglycosides, macrolides, sulfonamides and tetracyclines resistance determinants, which were either chromosomally and/or plasmid located. Furthermore, a gene order comparison using MAUVE alignment showed multiple changes compared with the clinical isolate of Malaysian A. baumannii AC30 genome and 76 regions with high homology. This study suggests that resistance to β-lactams in this A. baumannii isolate is mainly due to an overproduction of β-lactamases in combination with other resistance mechanism (efflux pump system).

scholarly journals A Novel CTX-M β-Lactamase (CTX-M-8) in Cefotaxime-ResistantEnterobacteriaceae Isolated in Brazil

2000 ◽  
Vol 44 (7) ◽  
pp. 1936-1942 ◽  
Author(s):  
R. Bonnet ◽  
J. L. M. Sampaio ◽  
R. Labia ◽  
C. De Champs ◽  
D. Sirot ◽  
...  
Keyword(s):  
Protein Sequence ◽  
Clinical Laboratory ◽  
Enterobacter Aerogenes ◽  
Enterobacter Cloacae ◽  
Cloning And Sequencing ◽  
E Coli ◽  
Class A ◽  
The Family ◽  
Synergy Test ◽  
Citrobacter Amalonaticus

ABSTRACT To estimate the diversity of extended-spectrum β-lactamases in Brazil, 18 strains from different species of the familyEnterobacteriaceae exhibiting a positive double-disk synergy test were collected by a clinical laboratory from several hospitals in Rio de Janeiro, Brazil, in 1996 and 1997. Four strains (Proteus mirabilis, Enterobacter cloacae,Enterobacter aerogenes, and Citrobacter amalonaticus) hybridized with a 550-bp CTX-M probe. The P. mirabilis strain produced a CTX-M-2 enzyme. The E. cloacae, E. aerogenes, and C. amalonaticus isolates harbored a bla gene which was identified by cloning and sequencing as abla CTX-M gene. E. coli HB101 transconjugants and the E. coli DH5α transformant harboring a recombinant plasmid produced a CTX-M β-lactamase with an isoelectric point of 7.6 conferring a resistance phenotype characterized by a higher level of resistance to cefotaxime than to ceftazidime, as observed with the other CTX-M enzymes. The deduced protein sequence showed a novel Ambler class A CTX-M enzyme, named CTX-M-8, which had 83 to 88% identity with the previously described CTX-M enzymes. The phylogenic study of the CTX-M family including CTX-M-8 revealed four CTX-M types, CTX-M-8 being the first member of a new phylum of CTX-M enzymes. The evolutionary distances between the four types of CTX-M were large, suggesting that the four clusters branched off early from a distant unknown enzyme and that intermediate enzymes probably existed.

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 Stepwise evolution of carbapenem-resistance, captured in patient samples and evident in global genomics of Klebsiella pneumoniae

2021 ◽  
Author(s):  
Laura Perlaza-Jimenez ◽  
Jonathan J. Wilksch ◽  
christopher J. Stubenrauch ◽  
Tao Chen ◽  
Yajie Zhao ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Efflux Pump ◽  
Carbapenem Resistance ◽  
Forensic Analysis ◽  
World Health ◽  
Beta Lactamases ◽  
Carbapenem Resistant ◽  
Large Numbers ◽  
Plasmid Genes ◽  
Health Organization

The World Health Organization ranks Klebsiella pneumoniae as a priority antimicrobial-resistant (AMR) pathogen requiring urgent study. New strategies for diagnosis and treatment, particularly for those Klebsiella that are classified as carbapenem-resistant Enterobacteriaceae (CRE) need to recognize the increased prevalence of non-carbapenemase producing CRE (non-CP CRE). By integrating diverse Klebsiella genomes with known CRE phenotypes, we successfully identified a synchronized presence of CRE phenotype-related genes in plasmids and chromosomes in comparison to strains with carbapenem susceptible phenotypes. The data revealed a major contribution to CRE comes from the combined effect of chromosome and plasmid genes potentiated by modifications of outer membrane porins. Our computational workflow identified key gene contributors to the non-CP CRE phenotype, including those that lead to an increase of antibiotic expulsion by enhanced efflux pump activity and mobile elements that reduce antibiotic intake, such as IS1 and Tn3-like elements. These findings are consistent with a new model wherein a change to the balance in drug influx and efflux potentiates the ability of some beta-lactamases to enable survival in the presence of carbapenems. Analysis of the large numbers of documented CRE infections, as well as forensic analysis of a case study, showed that this potentiation can occur in short timeframes to deliver a non-CP CRE infection. Our results suggest that the multiple genes that function to build an AMR phenotype can be diagnosed, so that strains that will resist treatment with carbapenem treatment will be evident if a comprehensive genome-based diagnostic for CRE considers all of these sequence-accessible features.

scholarly journals Activity of Cefepime in Combination with the novel ß-Lactamase inhibitor taniborbactam (VNRX-5133) against ESBL-producing isolates in in vitro checkerboard assays

2021 ◽  
Author(s):  
Wendy Kloezen ◽  
Ria J. Melchers ◽  
Panagiota-Christina Georgiou ◽  
Johan W. Mouton ◽  
Joseph Meletiadis
Keyword(s):  
Clinical Laboratory ◽  
Wide Spectrum ◽  
Resistance Mechanism ◽  
Enterobacter Aerogenes ◽  
Beta Lactamase ◽  
The Novel ◽  
Extended Spectrum Beta Lactamase ◽  
Fixed Concentration ◽  
Lactamase Inhibitor

Background. Extended spectrum beta-lactamase (ESBL) producing strains are increasing worldwide limiting therapeutic options. Taniborbactam (VNRX-5133) is a newly developed beta-lactamase inhibitor with a wide spectrum of activity covering both serine and metallo enzymes. We therefore, evaluated cefepime-taniborbactam activity against ESBL-producing isolates and determined the concentrations to be used in MIC determinations in the clinical laboratory. Methods. The in vitro activity of cefepime (0.06-256 mg/l) combined with taniborbactam (0.03-32 mg/l) against 129 clinically and molecularly well-documented ESBL producing isolates (42 Escherichia coli, 39 Klebsiella pneumoniae, 28 Pseudomonas aeruginosa, 16 Enterobacter cloacae, 2 Citrobacter freundii, 2 Enterobacter aerogenes) was tested with a broth microdilution checkerboard method based on ISO standard. The MICs of cefepime alone and in combination together with % of resistance at different concentrations of taniborbactam was calculated for each species and resistance mechanism. Results. The median (range)/MIC90 of cefepime were 32(0.125-256)/256 mg/l for all Enterobacterales isolates (n=101) with 72% being resistant and 32(8-256)/128 mg/l for the 28 P. aeruginosa isolates with 86% being resistant. The median(range)/90th percentile concentration of taniborbactam required to restore Enterobacterales susceptibility to cefepime (MIC ≤1 mg/l) was 0.06(≤0.03-32)/4 mg/l and P. aeruginosa susceptibility to increased exposure to cefepime (MIC ≤8 mg/l) 1(≤0.032-32)/32 mg/l. At a fixed concentration of 4 mg/liter of taniborbactam, cefepime median(range)/MIC90 were reduced to 0.125(0.06-4)/1 mg/l for Enterobacterales with no resistance detected and to 8(2-64)/16 mg/liter for P. aeruginosa isolates where 36% remained resistant. Conclusion. The combination cefepime/taniborbactam demonstrated a potent activity against ESBL isolates restoring susceptibility of all Enterobacterales and 2/3 of P. aeruginosa isolates.

scholarly journals Cloning, Nucleotide Sequencing, and Analysis of the AcrAB-TolC Efflux Pump of Enterobacter cloacae and Determination of Its Involvement in Antibiotic Resistance in a Clinical Isolate

2007 ◽  
Vol 51 (9) ◽  
pp. 3247-3253 ◽  
Author(s):  
Astrid Pérez ◽  
Delia Canle ◽  
Cristina Latasa ◽  
Margarita Poza ◽  
Alejandro Beceiro ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Clinical Isolate ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Enterobacter Aerogenes ◽  
Enterobacter Cloacae ◽  
Pcr Analysis ◽  
Nucleotide Sequencing ◽  
Efflux Pump Inhibitor ◽  
Antibiotic Resistance Profile

ABSTRACT Enterobacter cloacae is an emerging clinical pathogen that may be responsible for nosocomial infections. Management of these infections is often difficult, owing to the high frequency of strains that are resistant to disinfectants and antimicrobial agents in the clinical setting. Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role as a mechanism of antimicrobial resistance in gram-negative pathogens. In the present study, we cloned and sequenced the genes encoding an AcrAcB-TolC-like efflux pump from an E. cloacae clinical isolate (isolate EcDC64) showing a broad antibiotic resistance profile. Sequence analysis showed that the acrR, acrA, acrB, and tolC genes encode proteins that display 79.8%, 84%, 88%, and 82% amino acid identities with the respective homologues of Enterobacter aerogenes and are arranged in a similar pattern. Deletion of the acrA gene to yield an AcrA-deficient EcDC64 mutant (EcΔacrA) showed the involvement of AcrAB-TolC in multidrug resistance in E. cloacae. However, experiments with an efflux pump inhibitor suggested that additional efflux systems also play a role in antibiotic resistance. Investigation of several unrelated isolates of E. cloacae by PCR analysis revealed that the AcrAB system is apparently ubiquitous in this species.

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