scholarly journals Determination of MIC Distribution and Mechanisms of Decreased Susceptibility to Bedaquiline among Clinical Isolates of Mycobacterium abscessus

2018 ◽  
Vol 62 (7) ◽  
Author(s):  
Bing Li ◽  
Meiping Ye ◽  
Qi Guo ◽  
Zhemin Zhang ◽  
Shiyi Yang ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Efflux Pump ◽  
Mycobacterium Abscessus ◽  
Clinical Isolates ◽  
Whole Genome Sequencing Data ◽  
Pcr Analysis ◽  
Sequencing Data ◽  
Gene Encoding ◽  
Content Type

ABSTRACT Chemotherapeutic options against Mycobacterium abscessus infections are very limited. Bedaquiline, a new antituberculosis (anti-TB) drug, is effective for the treatment of multidrug-resistant TB. However, few data are available on bedaquiline for treatment of M. abscessus infections. In this study, we determined the profile for in vitro susceptibility of M. abscessus clinical isolates to bedaquiline and investigated the potential molecular mechanisms of decreased susceptibility. A total of 197 M. abscessus clinical isolates were collected from sputum and bronchoalveolar fluid of patients with lung infections. Standard broth microdilution test revealed that bedaquiline exhibited high in vitro killing activity against M. abscessus isolates, with a MIC 50 of 0.062 and a MIC 90 of 0.125 mg/liter. Whole-genome sequencing data showed that no nonsynonymous mutation occurred in atpE , the gene encoding the bedaquiline-targeted protein. However, of 6 strains with decreased susceptibility of bedaquiline (MIC = 0.5 to 1 mg/liter), 3 strains had nonsynonymous mutations in mab_4384 , the gene encoding the repressor of efflux pump MmpS5/MmpL5. Quantitative reverse transcription-PCR (qRT-PCR) analysis showed that the expression of MmpS5/MmpL5 in the group with decreased susceptibility to bedaquiline was significantly higher than in those with medium MICs (MIC = 0.125 to 0.5 mg/liter) or in the low-MIC group (MIC ≤ 0.062 mg/liter). Two isolates with increased MICs did not show overexpression of MmpS5/MmpL5, which could not be explained by known molecular mechanisms. This is the first report showing the association of MmpS5/MmpL5 with decreased bedaquiline susceptibility in M. abscessus clinical isolates and suggesting the presence of other, yet-to-be identified mechanisms for decreased bedaquiline susceptibility in M. abscessus .

scholarly journals Involvement of the AcrAB-TolC Efflux Pump in the Resistance, Fitness, and Virulence of Enterobacter cloacae

2012 ◽  
Vol 56 (4) ◽  
pp. 2084-2090 ◽  
Author(s):  
Astrid Pérez ◽  
Margarita Poza ◽  
Ana Fernández ◽  
Maria del Carmen Fernández ◽  
Susana Mallo ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Efflux Pump ◽  
Enterobacter Cloacae ◽  
Efflux Pumps ◽  
Clinical Isolates ◽  
Wild Type ◽  
Content Type

ABSTRACTMultidrug efflux pumps have emerged as important mechanisms of antimicrobial resistance in bacterial pathogens. In order to cause infection, pathogenic bacteria require mechanisms to avoid the effects of host-produced compounds, and express efflux pumps may accomplish this task. In this study, we evaluated the effect of the inactivation of AcrAB-TolC on antimicrobial resistance, fitness, and virulence inEnterobacter cloacae, an opportunistic pathogen usually involved in nosocomial infections. Two different clinical isolates ofE. cloacaewere used, EcDC64 (multidrug resistance overexpressing the AcrAB-TolC efflux pump) and Jc194 (basal AcrAB-TolC expression). TheacrAandtolCgenes were deleted in strains EcDC64 and Jc194 to produce, respectively, EcΔacrAand EcΔtolCand JcΔacrAand JcΔtolCknockout (KO) derivatives. Antibiotic susceptibility testing was performed with all isolates, and we discovered that these mechanisms are involved in the resistance ofE. cloacaeto several antibiotics. Competition experiments were also performed with wild-type and isogenic KO strains. The competition index (CI), defined as the mutant/wild-type ratio, revealed that theacrAandtolCgenes both affect the fitness ofE. cloacae, as fitness was clearly reduced in theacrAandtolCKO strains. The median CI values obtainedin vitroandin vivowere, respectively, 0.42 and 0.3 for EcDC64/EcΔacrA, 0.24 and 0.38 for EcDC64/EcΔtolC, 0.15 and 0.11 for Jc194/JcΔacrA, and 0.38 and 0.39 for Jc194/JcΔtolC. Use of an intraperitoneal mouse model of systemic infection revealed reduced virulence in bothE. cloacaeclinical strains when either theacrAortolCgene was inactivated. In conclusion, the structural components of the AcrAB-TolC efflux pump appear to play a role in antibiotic resistance as well as environmental adaptation and host virulence in clinical isolates ofE. cloacae.

scholarly journals Antibacterial activity of high-dose nitric oxide against pulmonary Mycobacterium abscessus disease

2020 ◽  
Vol 2 (9) ◽  
Author(s):  
Kristijan Bogdanovski ◽  
Trisha Chau ◽  
Chevalia J. Robinson ◽  
Sandra D. MacDonald ◽  
Ann M. Peterson ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Antibacterial Activity ◽  
Type Species ◽  
Mycobacterium Abscessus ◽  
Clinical Isolates ◽  
Content Type ◽  
Link Type ◽  
Susceptibility Tests ◽  
Inhaled No

Introduction. Mycobacterium abscessus is an emerging pulmonary pathogen with limited treatment options. Nitric oxide (NO) demonstrates antibacterial activity against various bacterial species, including mycobacteria. In this study, we evaluated the effect of adjunctive inhaled NO therapy, using a novel NO generator, in a CF patient with pulmonary M. abscessus disease, and examined heterogeneity of response to NO in vitro. Methods. In the compassionate-use treatment, a 24-year-old CF patient with pulmonary M. abscessus was treated with two courses of adjunctive intermittent NO, first at 160 p.p.m. for 21 days and subsequently by escalating the dose up to 240 p.p.m. for 8 days. Methemoglobin, pulmonary function, 6 min walk distance (6MWD), qualify of life and sputum microbiology were assessed. In vitro susceptibility tests were performed against patient’s isolate and comparison clinical isolates and quantified by Hill’s slopes calculated from time–kill curves. Results. M. abscessus lung infection eradication was not achieved, but improvements in selected qualify of life domains, lung function and 6MWD were observed during the study. Inhaled NO was well tolerated at 160 p.p.m. Dosing at 240 p.p.m. was stopped due to adverse symptoms, although methemoglobin levels remained within safety thresholds. In vitro susceptibility tests showed a dose-dependent NO effect on M. abscessus susceptibility and significant heterogeneity in response between M. abscessus clinical isolates. The patient’s isolate was found to be the least susceptible strain in vitro. Conclusion. These results demonstrate heterogeneity in M. abscessus susceptibility to NO and suggest that longer treatment regimens could be required to see the reduction or eradication of more resistant pulmonary strains.

scholarly journals Elucidating the Genetic Basis of Crystalline Biofilm Formation in Proteus mirabilis

2014 ◽  
Vol 82 (4) ◽  
pp. 1616-1626 ◽  
Author(s):  
N. Holling ◽  
D. Lednor ◽  
S. Tsang ◽  
A. Bissell ◽  
L. Campbell ◽  
...  
Keyword(s):  
Urinary Tract ◽  
Proteus Mirabilis ◽  
Biofilm Formation ◽  
Efflux Pump ◽  
Model Systems ◽  
Multidrug Efflux Pump ◽  
Gene Encoding ◽  
Content Type ◽  
Biofilm Development

ABSTRACTProteus mirabilisforms extensive crystalline biofilms on urethral catheters that occlude urine flow and frequently complicate the management of long-term-catheterized patients. Here, using random transposon mutagenesis in conjunction within vitromodels of the catheterized urinary tract, we elucidate the mechanisms underpinning the formation of crystalline biofilms byP. mirabilis. Mutants identified as defective in blockage of urethral catheters had disruptions in genes involved in nitrogen metabolism and efflux systems but were unaffected in general growth, survival in bladder model systems, or the ability to elevate urinary pH. Imaging of biofilms directly on catheter surfaces, along with quantification of levels of encrustation and biomass, confirmed that the mutants were attenuated specifically in the ability to form crystalline biofilms compared with that of the wild type. However, the biofilm-deficient phenotype of these mutants was not due to deficiencies in attachment to catheter biomaterials, and defects in later stages of biofilm development were indicated. For one blocking-deficient mutant, the disrupted gene (encoding a putative multidrug efflux pump) was also found to be associated with susceptibility to fosfomycin, and loss of this system or general inhibition of efflux pumps increased sensitivity to this antibiotic. Furthermore, homologues of this system were found to be widely distributed among other common pathogens of the catheterized urinary tract. Overall, our findings provide fundamental new insight into crystalline biofilm formation byP. mirabilis, including the link between biofilm formation and antibiotic resistance in this organism, and indicate a potential role for efflux pump inhibitors in the treatment or prevention ofP. mirabiliscrystalline biofilms.

scholarly journals Activity of Aztreonam in Combination with Avibactam, Clavulanate, Relebactam, and Vaborbactam against Multidrug-Resistant Stenotrophomonas maltophilia

2020 ◽  
Vol 64 (12) ◽  
Author(s):  
M. Biagi ◽  
D. Lamm ◽  
K. Meyer ◽  
A. Vialichka ◽  
M. Jurkovic ◽  
...  
Keyword(s):  
Stenotrophomonas Maltophilia ◽  
Molecular Mechanisms ◽  
Efflux Pump ◽  
Treatment Strategies ◽  
Multidrug Resistant ◽  
Content Type ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Novel Treatment Strategies

ABSTRACT The intrinsic L1 metallo- and L2 serine-β-lactamases in Stenotrophomonas maltophilia make it naturally multidrug resistant and difficult to treat. There is a need to identify novel treatment strategies for this pathogen, especially against isolates resistant to first-line agents. Aztreonam in combination with avibactam has demonstrated potential, although data on other aztreonam–β-lactamase inhibitor (BLI) combinations are lacking. Additionally, molecular mechanisms for reduced susceptibility to these combinations have not been explored. The objectives of this study were to evaluate and compare the in vitro activities and to understand the mechanisms of resistance to aztreonam in combination with avibactam, clavulanate, relebactam, and vaborbactam against S. maltophilia. A panel of 47 clinical S. maltophilia strains nonsusceptible to levofloxacin and/or trimethoprim-sulfamethoxazole were tested against each aztreonam-BLI combination via broth microdilution, and 6 isolates were then evaluated in time-kill analyses. Three isolates with various aztreonam-BLI MICs were subjected to whole-genome sequencing and quantitative reverse transcriptase PCR. Avibactam restored aztreonam susceptibility in 98% of aztreonam-resistant isolates, compared to 61, 71, and 15% with clavulanate, relebactam, and vaborbactam, respectively. The addition of avibactam to aztreonam resulted in a ≥2-log10-CFU/ml decrease at 24 h versus aztreonam alone against 5/6 isolates compared to 1/6 with clavulanate, 4/6 with relebactam, and 2/6 with vaborbactam. Molecular analyses revealed that decreased susceptibility to aztreonam-avibactam was associated with increased expression of genes encoding L1 and L2, as well as the efflux pump (smeABC). Aztreonam-avibactam is the most promising BLI-combination against multidrug-resistant S. maltophilia. Decreased susceptibility may be due to the combination of overexpressed β-lactamases and efflux pumps. Further studies evaluating this combination against S. maltophilia are warranted.

scholarly journals In Vitro Activity of New Tetracycline Analogs Omadacycline and Eravacycline against Drug-Resistant Clinical Isolates of Mycobacterium abscessus

2019 ◽  
Vol 63 (6) ◽  
Author(s):  
Amit Kaushik ◽  
Nicole C. Ammerman ◽  
Olumide Martins ◽  
Nicole M. Parrish ◽  
Eric L. Nuermberger
Keyword(s):  
Salvage Therapy ◽  
Treatment Options ◽  
Oral Formulation ◽  
Mycobacterium Abscessus ◽  
Clinical Isolates ◽  
Drug Resistant ◽  
In Vitro Activity ◽  
Content Type ◽  
New Treatment

ABSTRACT Tigecycline is used in multidrug regimens for salvage therapy of Mycobacterium abscessus infections but is often poorly tolerated and has no oral formulation. Here, we report similar in vitro activity of two newly approved tetracycline analogs, omadacycline and eravacycline, against 28 drug-resistant clinical isolates of M. abscessus complex. Since omadacycline and eravacycline appear to be better tolerated than tigecycline and since omadacycline is also formulated for oral dosing, these tetracycline analogs may represent new treatment options for M. abscessus infections.

scholarly journals High Levels of Intrinsic Tetracycline Resistance inMycobacterium abscessusAre Conferred by a Tetracycline-Modifying Monooxygenase

2018 ◽  
Vol 62 (6) ◽  
Author(s):  
Paulami Rudra ◽  
Kelley Hurst-Hess ◽  
Pascal Lappierre ◽  
Pallavi Ghosh
Keyword(s):  
Bacterial Infections ◽  
Efflux Pump ◽  
Tetracycline Resistance ◽  
Resistance Mechanisms ◽  
Mycobacterium Abscessus ◽  
Repeat Sequence ◽  
Content Type ◽  
High Level

ABSTRACTTetracyclines have been one of the most successful classes of antibiotics. However, its extensive use has led to the emergence of widespread drug resistance, resulting in discontinuation of use against several bacterial infections. Prominent resistance mechanisms include drug efflux and the use of ribosome protection proteins. Infrequently, tetracyclines can be inactivated by the TetX class of enzymes, also referred to as tetracycline destructases. Low levels of tolerance to tetracycline inMycobacterium smegmatisandMycobacterium tuberculosishave been previously attributed to the WhiB7-dependent TetV/Tap efflux pump. However,Mycobacterium abscessusis ∼500-fold more resistant to tetracycline thanM. smegmatisandM. tuberculosis. In this report, we show that this high level of resistance to tetracycline and doxycycline inM. abscessusis conferred by a WhiB7-independent tetracycline-inactivating monooxygenase, MabTetX (MAB_1496c). The presence of sublethal doses of tetracycline and doxycycline results in a >200-fold induction of MabTetX, and an isogenic deletion strain is highly sensitive to both antibiotics. Further, purified MabTetX can rapidly monooxygenate both antibiotics. We also demonstrate that expression of MabTetX is repressed by MabTetRx, by binding to an inverted repeat sequence upstream of MabTetRx; the presence of either antibiotic relieves this repression. Moreover, anhydrotetracycline (ATc) can effectively inhibit MabTetX activityin vitroand decreases the MICs of both tetracycline and doxycyclinein vivo. Finally, we show that tigecycline, a glycylcycline tetracycline, not only is a poor substrate of MabTetX but also is incapable of inducing the expression of MabTetX. This is therefore the first demonstration of a tetracycline-inactivating enzyme in mycobacteria. It (i) elucidates the mechanism of tetracycline resistance inM. abscessus, (ii) demonstrates the use of an inhibitor that can potentially reclaim the use of tetracycline and doxycycline, and (iii) identifies two sequential bottlenecks—MabTetX and MabTetRx—for acquiring resistance to tigecycline, thereby reiterating its use againstM. abscessus.

scholarly journals The TetR Family Transcription Factor MAB_2299c Regulates the Expression of Two Distinct MmpS-MmpL Efflux Pumps Involved in Cross-Resistance to Clofazimine and Bedaquiline in Mycobacterium abscessus

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Ana Victoria Gutiérrez ◽  
Matthias Richard ◽  
Françoise Roquet-Banères ◽  
Albertus Viljoen ◽  
Laurent Kremer
Keyword(s):  
Efflux Pump ◽  
Respiratory Infections ◽  
Efflux Pumps ◽  
Mycobacterium Abscessus ◽  
Cross Resistance ◽  
Intrinsic Resistance ◽  
Mobility Shift ◽  
Pump System ◽  
Content Type

ABSTRACT Mycobacterium abscessus is a human pathogen responsible for severe respiratory infections, particularly in patients with underlying lung disorders. Notorious for being highly resistant to most antimicrobials, new therapeutic approaches are needed to successfully treat M. abscessus-infected patients. Clofazimine (CFZ) and bedaquiline (BDQ) are two antibiotics used for the treatment of multidrug-resistant tuberculosis and are considered alternatives for the treatment of M. abscessus pulmonary disease. To get insights into their mechanisms of resistance in M. abscessus, we previously characterized the TetR transcriptional regulator MAB_2299c, which controls expression of the MAB_2300-MAB_2301 genes, encoding an MmpS-MmpL efflux pump. Here, in silico studies identified a second mmpS-mmpL (MAB_1135c-MAB_1134c) target of MAB_2299c. A palindromic DNA sequence upstream of MAB_1135c, sharing strong homology with the one located upstream of MAB_2300, was found to form a complex with the MAB_2299c regulator in electrophoretic mobility shift assays. Deletion of MAB_1135c-1134c in a wild-type strain led to increased susceptibility to both CFZ and BDQ. In addition, deletion of these genes in a CFZ/BDQ-susceptible mutant lacking MAB_2299c as well as MAB_2300-MAB_2301 further exacerbated the sensitivity of this strain to both drugs in vitro and inside macrophages. Overall, these results indicate that MAB_1135c-1134c encodes a new MmpS-MmpL efflux pump system involved in the intrinsic resistance to CFZ and BDQ. They also support the view that MAB_2299c controls the expression of two separate MmpS-MmpL efflux pumps, substantiating the importance of MAB_2299c as a marker of resistance to be considered when assessing drug susceptibility in clinical isolates.

scholarly journals In Vitro Activity of Bedaquiline and Delamanid against Nontuberculous Mycobacteria, Including Macrolide-Resistant Clinical Isolates

2019 ◽  
Vol 63 (8) ◽  
Author(s):  
Dae Hun Kim ◽  
Byung Woo Jhun ◽  
Seong Mi Moon ◽  
Su-Young Kim ◽  
Kyeongman Jeon ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Nontuberculous Mycobacteria ◽  
Mycobacterium Abscessus ◽  
Vitro Activity ◽  
Clinical Isolates ◽  
In Vitro Activity ◽  
Mycobacterium Kansasii ◽  
Antimicrobial Drugs ◽  
Content Type

ABSTRACT We evaluated the in vitro activities of the antimicrobial drugs bedaquiline and delamanid against the major pathogenic nontuberculous mycobacteria (NTM). Delamanid showed high MIC values for all NTM except Mycobacterium kansasii. However, bedaquiline showed low MIC values for the major pathogenic NTM, including Mycobacterium avium complex, Mycobacterium abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. kansasii. Bedaquiline also had low MIC values with macrolide-resistant NTM strains and warrants further investigation as a potential antibiotic for NTM treatment.

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.

scholarly journals In Vitro Selection oframRandsoxRMutants Overexpressing Efflux Systems by Fluoroquinolones as Well as Cefoxitin in Klebsiella pneumoniae

2011 ◽  
Vol 55 (6) ◽  
pp. 2795-2802 ◽  
Author(s):  
Suzanne Bialek-Davenet ◽  
Estelle Marcon ◽  
Véronique Leflon-Guibout ◽  
Jean-Philippe Lavigne ◽  
Frédéric Bert ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
In Vitro Selection ◽  
Efflux Pump ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Efflux System ◽  
Content Type ◽  
New Antibiotics ◽  
Regulator Genes

ABSTRACTThe relationship between efflux system overexpression and cross-resistance to cefoxitin, quinolones, and chloramphenicol has recently been reported inKlebsiella pneumoniae. In 3 previously published clinical isolates and 17in vitromutants selected with cefoxitin or fluoroquinolones, mutations in the potential regulator genes of the AcrAB efflux pump (acrR,ramR,ramA,marR,marA,soxR,soxS, androb) were searched, and their impacts on efflux-related antibiotic cross-resistance were assessed. All mutants but 1, and 2 clinical isolates, overexpressedacrB. No mutation was detected in the regulator genes studied among the clinical isolates and 8 of the mutants. For the 9 remaining mutants, a mutation was found in theramRgene in 8 of them and in thesoxRgene in the last one, resulting in overexpression oframAandsoxS, respectively. Transformation of theramRmutants and thesoxRmutant with the wild-typeramRandsoxRgenes, respectively, abolished overexpression ofacrBandramAin theramRmutants and ofsoxSin thesoxRmutant, as well as antibiotic cross-resistance. Resistance due to efflux system overexpression was demonstrated for 4 new antibiotics: cefuroxime, cefotaxime, ceftazidime, and ertapenem. This study shows that theramRandsoxRgenes control the expression of efflux systems inK. pneumoniaeand suggests the existence of efflux pumps other than AcrAB and of other loci involved in the regulation of AcrAB expression.

Sign in / Sign up

Export Citation Format

Share Document