scholarly journals Dissecting Colistin Resistance Mechanisms in Extensively Drug-Resistant Acinetobacter baumannii Clinical Isolates

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Vincent Trebosc ◽  
Sarah Gartenmann ◽  
Marcus Tötzl ◽  
Valentina Lucchini ◽  
Birgit Schellhorn ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Nosocomial Infections ◽  
Drug Target ◽  
Resistance Mechanism ◽  
Clinical Isolates ◽  
Drug Resistant ◽  
Colistin Resistance ◽  
Content Type ◽  
Extensively Drug Resistant ◽  
Direct Targeting

ABSTRACT Nosocomial infections with Acinetobacter baumannii are a global problem in intensive care units with high mortality rates. Increasing resistance to first- and second-line antibiotics has forced the use of colistin as last-resort treatment, and increasing development of colistin resistance in A. baumannii has been reported. We evaluated the transcriptional regulator PmrA as potential drug target to restore colistin efficacy in A. baumannii. Deletion of pmrA restored colistin susceptibility in 10 of the 12 extensively drug-resistant A. baumannii clinical isolates studied, indicating the importance of PmrA in the drug resistance phenotype. However, two strains remained highly resistant, indicating that PmrA-mediated overexpression of the phosphoethanolamine (PetN) transferase PmrC is not the exclusive colistin resistance mechanism in A. baumannii. A detailed genetic characterization revealed a new colistin resistance mechanism mediated by genetic integration of the insertion element ISAbaI upstream of the PmrC homolog EptA (93% identity), leading to its overexpression. We found that eptA was ubiquitously present in clinical strains belonging to the international clone 2, and ISAbaI integration upstream of eptA was required to mediate the colistin-resistant phenotype. In addition, we found a duplicated ISAbaI-eptA cassette in one isolate, indicating that this colistin resistance determinant may be embedded in a mobile genetic element. Our data disprove PmrA as a drug target for adjuvant therapy but highlight the importance of PetN transferase-mediated colistin resistance in clinical strains. We suggest that direct targeting of the homologous PetN transferases PmrC/EptA may have the potential to overcome colistin resistance in A. baumannii. IMPORTANCE The discovery of antibiotics revolutionized modern medicine and enabled us to cure previously deadly bacterial infections. However, a progressive increase in antibiotic resistance rates is a major and global threat for our health care system. Colistin represents one of our last-resort antibiotics that is still active against most Gram-negative bacterial pathogens, but increasing resistance is reported worldwide, in particular due to the plasmid-encoded protein MCR-1 present in pathogens such as Escherichia coli and Klebsiella pneumoniae. Here, we showed that colistin resistance in A. baumannii, a top-priority pathogen causing deadly nosocomial infections, is mediated through different avenues that result in increased activity of homologous phosphoethanolamine (PetN) transferases. Considering that MCR-1 is also a PetN transferase, our findings indicate that PetN transferases might be the Achilles heel of superbugs and that direct targeting of them may have the potential to preserve the activity of polymyxin antibiotics.

scholarly journals Complete Genome Sequences of Four Extensively Drug-Resistant Acinetobacter baumannii Isolates from Thailand

2020 ◽  
Vol 9 (40) ◽  
Author(s):  
Peechanika Chopjitt ◽  
Thidathip Wongsurawat ◽  
Piroon Jenjaroenpun ◽  
Parichart Boueroy ◽  
Rujirat Hatrongjit ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Complete Genome ◽  
Sequence Type ◽  
Clinical Isolates ◽  
Drug Resistant ◽  
Genome Sequences ◽  
Content Type ◽  
Type Isolate ◽  
Resistant Genes ◽  
Extensively Drug Resistant

ABSTRACT Here, we report the complete genome sequences of four clinical isolates of extensively drug-resistant Acinetobacter baumannii (XDRAB), isolated in Thailand. These results revealed multiple antimicrobial-resistant genes, each involving two sequence type 16 (ST16) isolates, ST2, and a novel sequence type isolate, ST1479.

Extensively drug-resistant Acinetobacter baumannii nosocomial pneumonia successfully treated with a novel antibiotic combination

2021 ◽  
Author(s):  
Noor Zaidan ◽  
J. Patrik Hornak ◽  
David Reynoso
Keyword(s):  
Septic Shock ◽  
Drug Development ◽  
Acinetobacter Baumannii ◽  
Nosocomial Infections ◽  
Drug Resistant ◽  
Access Protocol ◽  
The Poor ◽  
Extensively Drug Resistant ◽  
Poor Outcomes ◽  
Antibiotic Combination

Extremely drug resistant (XDR) Acinetobacter baumannii cause challenging nosocomial infections. We report the case of a patient with XDR A. baumannii pneumonia and septic shock successfully treated with cefiderocol and a novel antibiotic obtained via expanded access protocol. With focused research and drug development efforts, the poor outcomes associated with these infections may be mitigated.

scholarly journals A Prospective Study of Acinetobacter baumannii Complex Isolates and Colistin Susceptibility Monitoring by Mass Spectrometry of Microbial Membrane Glycolipids

2018 ◽  
Vol 57 (3) ◽  
Author(s):  
Lisa M. Leung ◽  
Christi L. McElheny ◽  
Francesca M. Gardner ◽  
Courtney E. Chandler ◽  
Sarah L. Bowler ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Acinetobacter Baumannii ◽  
Lipid A ◽  
Membrane Lipids ◽  
Clinical Isolates ◽  
Colistin Resistance ◽  
Hospital System ◽  
Content Type ◽  
Acinetobacter Baumannii Complex ◽  
Gram Negative Organisms

ABSTRACT Acinetobacter baumannii is a prevalent nosocomial pathogen with a high incidence of multidrug resistance. Treatment of infections due to this organism with colistin, a last-resort antibiotic of the polymyxin class, can result in the emergence of colistin-resistant strains. Colistin resistance primarily occurs via modifications of the terminal phosphate moieties of lipopolysaccharide-derived lipid A, which reduces overall membrane electronegativity. These modifications are readily identified by mass spectrometry (MS). In this study, we prospectively collected Acinetobacter baumannii complex clinical isolates from a hospital system in Pennsylvania over a 3-year period. All isolates were evaluated for colistin resistance using standard MIC testing by both agar dilution and broth microdilution, as well as genospecies identification and lipid A profiling using MS analyses. Overall, an excellent correlation between colistin susceptibility and resistance, determined by MIC testing, and the presence of a lipid A modification, determined by MS, was observed with a sensitivity of 92.9% and a specificity of 94.0%. Additionally, glycolipid profiling was able to differentiate A. baumannii complex organisms based on their membrane lipids. With the growth of MS use in clinical laboratories, a reliable MS-based glycolipid phenotyping method that identifies colistin resistance in A. baumannii complex clinical isolates, as well as other Gram-negative organisms, represents an alternative or complementary approach to existing diagnostics.

scholarly journals Correlation of Checkerboard Synergy Testing with Time-Kill Analysis and Clinical Outcomes of Extensively Drug-Resistant Acinetobacter baumannii Respiratory Infections

2016 ◽  
Vol 60 (11) ◽  
pp. 6892-6895 ◽  
Author(s):  
Derek N. Bremmer ◽  
Karri A. Bauer ◽  
Stephanie M. Pouch ◽  
Keelie Thomas ◽  
Debra Smith ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Clinical Outcomes ◽  
Clinical Utility ◽  
Respiratory Infections ◽  
Drug Resistant ◽  
Content Type ◽  
Extensively Drug Resistant ◽  
Time Kill ◽  
Synergy Testing

ABSTRACTWe tested 76 extensively drug-resistant (XDR)Acinetobacter baumanniiisolates by the checkerboard method using only wells containing serum-achievable concentrations (SACs) of drugs. Checkerboard results were correlated by time-kill assay and clinical outcomes. Minocycline-colistin was the best combinationin vitro, as it inhibited growth in one or more SAC wells in all isolates. Patients who received a combination that inhibited growth in one or more SAC wells demonstrated better microbiological clearance than those who did not (88% versus 30%;P= 0.025). The checkerboard platform may have clinical utility for XDRA. baumanniiinfections.

scholarly journals Carbapenemases: Transforming Acinetobacter baumannii into a Yet More Dangerous Menace

Biomolecules ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 720 ◽  
Author(s):  
Maria Soledad Ramirez ◽  
Robert A. Bonomo ◽  
Marcelo E. Tolmasky
Keyword(s):  
Acinetobacter Baumannii ◽  
Nosocomial Infections ◽  
Acquired Resistance ◽  
Clinical Manifestations ◽  
High Capacity ◽  
Bloodstream Infections ◽  
Multidrug Resistant ◽  
Drug Resistant ◽  
Wound Infections ◽  
Extensively Drug Resistant

Acinetobacter baumannii is a common cause of serious nosocomial infections. Although community-acquired infections are observed, the vast majority occur in people with preexisting comorbidities. A. baumannii emerged as a problematic pathogen in the 1980s when an increase in virulence, difficulty in treatment due to drug resistance, and opportunities for infection turned it into one of the most important threats to human health. Some of the clinical manifestations of A. baumannii nosocomial infection are pneumonia; bloodstream infections; lower respiratory tract, urinary tract, and wound infections; burn infections; skin and soft tissue infections (including necrotizing fasciitis); meningitis; osteomyelitis; and endocarditis. A. baumannii has an extraordinary genetic plasticity that results in a high capacity to acquire antimicrobial resistance traits. In particular, acquisition of resistance to carbapenems, which are among the antimicrobials of last resort for treatment of multidrug infections, is increasing among A. baumannii strains compounding the problem of nosocomial infections caused by this pathogen. It is not uncommon to find multidrug-resistant (MDR, resistance to at least three classes of antimicrobials), extensively drug-resistant (XDR, MDR plus resistance to carbapenems), and pan-drug-resistant (PDR, XDR plus resistance to polymyxins) nosocomial isolates that are hard to treat with the currently available drugs. In this article we review the acquired resistance to carbapenems by A. baumannii. We describe the enzymes within the OXA, NDM, VIM, IMP, and KPC groups of carbapenemases and the coding genes found in A. baumannii clinical isolates.

scholarly journals Evaluation of Pyrosequencing for Detecting Extensively Drug-Resistant Mycobacterium tuberculosis among Clinical Isolates from Four High-Burden Countries

2014 ◽  
Vol 59 (1) ◽  
pp. 414-420 ◽  
Author(s):  
Kanchan Ajbani ◽  
Shou-Yean Grace Lin ◽  
Camilla Rodrigues ◽  
Duylinh Nguyen ◽  
Francine Arroyo ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Mycobacterium Tuberculosis ◽  
The Philippines ◽  
Drug Susceptibility Testing ◽  
Clinical Isolates ◽  
Drug Resistant ◽  
Second Line ◽  
Additional Advantage ◽  
Content Type ◽  
Extensively Drug Resistant

ABSTRACTReliable molecular diagnostics, which detect specific mutations associated with drug resistance, are promising technologies for the rapid identification and monitoring of drug resistance inMycobacterium tuberculosisisolates. Pyrosequencing (PSQ) has the ability to detect mutations associated with first- and second-line anti-tuberculosis (TB) drugs, with the additional advantage of being rapidly adaptable for the identification of new mutations. The aim of this project was to evaluate the performance of PSQ in predicting phenotypic drug resistance in multidrug- and extensively drug-resistant tuberculosis (M/XDR-TB) clinical isolates from India, South Africa, Moldova, and the Philippines. A total of 187 archived isolates were run through a PSQ assay in order to identifyM. tuberculosis(via the IS6110marker), and to detect mutations associated with M/XDR-TB within small stretches of nucleotides in selected loci. The molecular targets includedkatG, theinhApromoter and theahpC-oxyRintergenic region for isoniazid (INH) resistance; therpoBcore region for rifampin (RIF) resistance;gyrAfor fluoroquinolone (FQ) resistance; andrrsfor amikacin (AMK), capreomycin (CAP), and kanamycin (KAN) resistance. PSQ data were compared to phenotypic mycobacterial growth indicator tube (MGIT) 960 drug susceptibility testing results for performance analysis. The PSQ assay illustrated good sensitivity for the detection of resistance to INH (94%), RIF (96%), FQ (93%), AMK (84%), CAP (88%), and KAN (68%). The specificities of the assay were 96% for INH, 100% for RIF, FQ, AMK, and KAN, and 97% for CAP. PSQ is a highly efficient diagnostic tool that reveals specific nucleotide changes associated with resistance to the first- and second-line anti-TB drug medications. This methodology has the potential to be linked to mutation-specific clinical interpretation algorithms for rapid treatment decisions.

scholarly journals Investigation of Novel pmrB and eptA Mutations in Isogenic Acinetobacter baumannii Isolates Associated with Colistin Resistance and Increased Virulence In Vivo

2019 ◽  
Vol 63 (3) ◽  
Author(s):  
Stefanie Gerson ◽  
Jonathan W. Betts ◽  
Kai Lucaßen ◽  
Carolina Silva Nodari ◽  
Julia Wille ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Lipid A ◽  
Galleria Mellonella ◽  
Resistance Mechanism ◽  
Resistant Isolate ◽  
Infection Model ◽  
Colistin Resistance ◽  
Strain Specificity ◽  
Content Type

ABSTRACT Colistin resistance in Acinetobacter baumannii is of great concern and is a threat to human health. In this study, we investigate the mechanisms of colistin resistance in four isogenic pairs of A. baumannii isolates displaying an increase in colistin MICs. A mutation in pmrB was detected in each colistin-resistant isolate, three of which were novel (A28V, I232T, and ΔL9-G12). Increased expression of pmrC was shown by semi-quantitative reverse transcription-PCR (qRT-PCR) for three colistin-resistant isolates, and the addition of phosphoethanolamine (PEtN) to lipid A by PmrC was revealed by mass spectrometry. Interestingly, PEtN addition was also observed in some colistin-susceptible isolates, indicating that this resistance mechanism might be strain specific and that other factors could contribute to colistin resistance. Furthermore, the introduction of pmrAB carrying the short amino acid deletion ΔL9-G12 into a pmrAB knockout strain resulted in increased pmrC expression and lipid A modification, but colistin MICs remained unchanged, further supporting the strain specificity of this colistin resistance mechanism. Of note, a mutation in the pmrC homologue eptA and a point mutation in ISAba1 upstream of eptA were associated with colistin resistance and increased eptA expression, which is a hitherto undescribed resistance mechanism. Moreover, no cost of fitness was observed for colistin-resistant isolates, while the virulence of these isolates was increased in a Galleria mellonella infection model. Although the mutations in pmrB were associated with colistin resistance, PEtN addition appears not to be the sole factor leading to colistin resistance, indicating that the mechanism of colistin resistance is far more complex than previously suspected and is potentially strain specific.

scholarly journals Whole-Genome-Sequence-Based Characterization of Extensively Drug-Resistant Acinetobacter baumannii Hospital Outbreak

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Ghiwa Makke ◽  
Ibrahim Bitar ◽  
Tamara Salloum ◽  
Balig Panossian ◽  
Sahar Alousi ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Tertiary Hospital ◽  
Outbreak Detection ◽  
Whole Genome ◽  
Transmission Network ◽  
Drug Resistant ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Extensively Drug Resistant ◽  
Long Read

ABSTRACT Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important opportunistic pathogen linked to a variety of nosocomial infections and hospital outbreaks worldwide. This study aimed at investigating and characterizing a CRAB outbreak at a large tertiary hospital in Lebanon. A total of 41 isolates were collected and analyzed using pulsed-field gel electrophoresis (PFGE). Whole-genome sequencing (WGS) was performed on all the isolates, and long-read PacBio sequencing was used to generate reference genomes. The multilocus sequence types (MLST), repertoire of resistance genes, and virulence factors were determined from the sequencing data. The plasmid content was analyzed both in silico and using the A. baumannii PCR-based replicon typing (AB-PBRT) method. Genome analysis initially revealed two clones, one carrying blaOXA-23 on Tn2006 (ST-1305, ST-195, and ST-218) and another carrying blaOXA-72 on pMAL-1 (ST-502 and ST-2059, a new ST), with the latter having two subclones, as revealed using the Bayesian transmission network. All isolates were extensively drug resistant (XDR). WGS analysis revealed the transmission pathways and demonstrated the diversity of CRAB isolates and mobile genetic elements in this health care setting. Outbreak detection using WGS and immediate implementation of infection control measures contribute to restraining the spread and decreasing mortality. IMPORTANCE Carbapenem-resistant Acinetobacter baumannii (CRAB) has been implicated in hospital outbreaks worldwide. Here, we present a whole-genome-based investigation of an extensively drug-resistant CRAB outbreak rapidly spreading and causing high incidences of mortality at numerous wards of a large tertiary hospital in Lebanon. This is the first study of its kind in the region. Two circulating clones were identified using a combination of molecular typing approaches, short- and long-read sequencing and Bayesian transmission network analysis. One clone carried blaOXA-23 on Tn2006 (ST-1305, ST-195, and ST-218), and another carried blaOXA-72 on a pMAL-1 plasmid (ST-502 and ST-2059, a new ST). A pMAL-2 plasmid was circulating between the two clones. The approaches implemented in this study and the obtained findings facilitate the tracking of outbreak scenarios in Lebanon and the region at large.

scholarly journals Determining the Development of Persisters in Extensively Drug-Resistant Acinetobacter baumannii upon Exposure to Polymyxin B-Based Antibiotic Combinations Using Flow Cytometry

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Fiona Hui-Sian Wong ◽  
Yiying Cai ◽  
Hui Leck ◽  
Tze-Peng Lim ◽  
Jocelyn Qi-Min Teo ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Acinetobacter Baumannii ◽  
Polymyxin B ◽  
Live Cells ◽  
Drug Resistant ◽  
Bacterial Cells ◽  
Persister Cells ◽  
Content Type ◽  
Initial Inoculum ◽  
Extensively Drug Resistant

ABSTRACT Polymyxin B-based combinations are increasingly prescribed as a last-line option against extensively drug-resistant (XDR) Acinetobacter baumannii. It is unknown if such combinations can result in the development of nondividing persister cells in XDR A. baumannii. We investigated persister development upon exposure of XDR A. baumannii to polymyxin B-based antibiotic combinations using flow cytometry. Time-kill studies (TKSs) were conducted in three nonclonal XDR A. baumannii strains with 5 log10 CFU/ml bacteria against polymyxin B alone and polymyxin B-based two-drug combinations over 24 h. At different time points, samples were obtained and enumerated by viable plating and flow cytometry. Propidium iodide and carboxyfluorescein succinimidyl ester dyes were used to differentiate between live and dead cells and between dividing and nondividing cells, respectively, at the single-cell level, and nondividing live cells were resuscitated and characterized phenotypically. Our results from viable plating showed that polymyxin B plus meropenem and polymyxin B plus rifampin were each bactericidal (>99.9% kill compared to the initial inoculum) against 2/3 XDR A. baumannii strains at 24 h. By flow cytometry, however, none of the combinations were bactericidal against XDR A. baumannii at 24 h. Further analysis using cellular dyes in flow cytometry revealed that upon exposure to polymyxin B-based combinations, XDR A. baumannii entered a viable but nondividing persister state. These bacterial cells reinitiated division upon the removal of antibiotic pressure and did not have a growth deficit compared to the parent strain. We conclude that persister cells develop in XDR A. baumannii upon exposure to polymyxin B-based combinations and that nonplating methods appear to complement viable-plating methods in describing the killing activity of polymyxin B-based combinations against XDR A. baumannii.

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