Antimicrobial Resistance Mechanisms and Virulence of Colistin- and Carbapenem-Resistant Acinetobacter baumannii Isolated from a Teaching Hospital in Taiwan

Acinetobacter baumannii, a Gram-negative bacterium, is an important nosocomial pathogen. Colistin-resistant A. baumannii is becoming a new concern, since colistin is one of the last-line antibiotics for infections by carbapenem-resistant A. baumannii. From 452 carbapenem-resistant isolates collected in a teaching hospital in Taipei, Taiwan, we identified seven that were resistant to colistin. Carbapenem resistance in these isolates is attributed to the presence of carbapenemase gene blaOXA-23 in their genomes. Colistin resistance is presumably conferred by mutations in the sensor kinase domain of PmrB found in these isolates, which are known to result in modification of colistin target lipid A via the PmrB–PmrA–PmrC signal transduction pathway. Overexpression of pmrC, eptA, and naxD was observed in all seven isolates. Colistin resistance mediated by pmrB mutations has never been reported in Taiwan. One of the seven isolates contained three mutations in lpxD and exhibited an altered lipopolysaccharide profile, which may contribute to its colistin resistance. No significant difference in growth rates was observed between the isolates and the reference strain, suggesting no fitness cost of colistin resistance. Biofilm formation abilities of the isolates were lower than that of the reference. Interestingly, one of the isolates was heteroresistant to colistin. Four of the isolates were significantly more virulent to wax moth larvae than the reference.

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

BMC Microbiology ◽

10.1186/s12866-021-02250-x ◽

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.

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

10.21203/rs.3.rs-38056/v1 ◽

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.

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Colistin resistance in Acinetobacter baumannii is driven by multiple genomic traits: Evaluating the role of ISAba1-driven eptA overexpression among Indian isolates

10.1101/2021.01.07.425695 ◽

2021 ◽

Author(s):

Saranya Vijayakumar ◽

Jobin John Jacob ◽

Karthick Vasudevan ◽

Baby Abirami Shankar ◽

Maria Lincy Francis ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Lipid A ◽

Resistance Mechanisms ◽

Clinical Isolates ◽

Colistin Resistance ◽

Two Component System ◽

Synonymous Mutations ◽

Insertional Inactivation ◽

Indian Isolates

Colistin resistance in Acinetobacter baumannii is mediated by multiple mechanisms. Recently, mutations within pmrAB two component system and overexpression of eptA due to upstream insertion of ISAba1 play a major role. To characterize colistin resistance mechanisms among the clinical isolates of A. baumannii in India. A total of 224 clinical isolates of A. baumannii collected from 2016 to 2019 were included in this study. Mutations within lipid A biosynthesis and pmrAB genes were characterized by Whole Genome Shotgun sequencing. Twenty eight complete genomes were further characterized for insertional inactivation of lpx genes and the association of ISAba1-eptA using hybrid assembly approach. Non-synonymous mutations like M12I in pmrA, A138T and A444V in pmrB and E117K in lpxD were identified. Four of the five colistin resistant A. baumannii isolates had insertion of ISAba1 upstream eptA. No mcr genes were identified. Overall, the present study highlights the diversity of colistin resistance mechanisms in A. baumannii. ISAba1-driven eptA overexpression could be responsible for colistin resistance among Indian isolates of colistin resistant A. baumannii.

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Synergy between Colistin and the Signal Peptidase Inhibitor MD3 Is Dependent on the Mechanism of Colistin Resistance in Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00510-16 ◽

2016 ◽

Vol 60 (7) ◽

pp. 4375-4379 ◽

Cited By ~ 3

Author(s):

Marta Martínez-Guitián ◽

Juan C. Vázquez-Ucha ◽

Joshua Odingo ◽

Tanya Parish ◽

Margarita Poza ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Lipid A ◽

Growth Curves ◽

Resistance Mechanisms ◽

Signal Peptidase ◽

Colistin Resistance ◽

Content Type ◽

Peptidase Inhibitor ◽

Resistant Strains ◽

Isogenic Mutants

ABSTRACTSynergy between colistin and the signal peptidase inhibitor MD3 was tested against isogenic mutants and clinical pairs ofAcinetobacter baumanniiisolates. Checkerboard assays and growth curves showed synergy against both colistin-susceptible strains (fractional inhibitory concentration index [FICindex] = 0.13 to 0.24) and colistin-resistant strains with mutations inpmrBand phosphoethanolamine modification of lipid A (FICindex= 0.14 to 0.25) but not against colistin-resistant Δlpxstrains with loss of lipopolysaccharide (FICindex= 0.75 to 1). A colistin/MD3 combination would need to be targeted to strains with specific colistin resistance mechanisms.

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Evaluation of Clonality and Carbapenem Resistance Mechanisms among Acinetobacter baumannii-Acinetobacter calcoaceticus Complex and Enterobacteriaceae Isolates Collected in European and Mediterranean Countries and Detection of Two Novel β-Lactamases, GES-22 and VIM-35

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03930-14 ◽

2014 ◽

Vol 58 (12) ◽

pp. 7358-7366 ◽

Cited By ~ 35

Author(s):

Mariana Castanheira ◽

Sarah E. Costello ◽

Leah N. Woosley ◽

Lalitagauri M. Deshpande ◽

Todd A. Davies ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Carbapenem Resistance ◽

Acinetobacter Calcoaceticus ◽

Resistance Mechanisms ◽

The Novel ◽

Intrinsic Resistance ◽

Content Type ◽

Carbapenem Resistant ◽

Mediterranean Countries ◽

Class 1

ABSTRACTWe evaluated doripenem-resistantAcinetobacter baumannii-Acinetobacter calcoaceticuscomplex (ACB;n= 411) andEnterobacteriaceae(n= 92) isolates collected from patients from 14 European and Mediterranean countries during 2009 to 2011 for the presence of carbapenemase-encoding genes and clonality. Following susceptibility testing, carbapenem-resistant (doripenem MIC, >2 μg/ml) isolates were screened for carbapenemases. New β-lactamase genes were expressed in a common background and susceptibility was tested. Class 1 integrons were sequenced. Clonality was evaluated by pulsed-field gel electrophoresis and multilocus sequence typing (Pasteur scheme). Relative expression of β-lactam intrinsic resistance mechanisms was determined for carbapenemase-negativeEnterobacteriaceae. ACB andEnterobacteriaceaedisplayed 58.9 and 0.9% doripenem resistance, respectively.blaOXA-23,blaOXA-58, andblaOXA-24/OXA-40were detected among 277, 77, and 29 ACB, respectively (in 8, 6, and 5 countries). Ten Turkish isolates carriedblaGES-11orblaGES-22. GES-22 (G243A and M169L mutations in GES-1) had an extended-spectrum β-lactamase profile. A total of 33 clusters of ≥2 ACB isolates were observed, and 227 isolates belonged to sequence type 2/international clone II. Other international clones were limited to Turkey and Israel. Doripenem-resistantEnterobacteriaceaeincreased significantly (0.7 to 1.6%), and 15blaKPC-2- and 22blaKPC-3-carrying isolates, mostly belonging to clonal complexes 11 and 258, were observed.Enterobacteriaceaeisolates producing OXA-48 (n= 16; in Turkey and Italy), VIM-1 (n= 10; in Greece, Poland, and Spain), VIM-26 (n= 1; in Greece), and IMP-19, VIM-4, and the novel VIM-35 (n= 1 each from Poland) were detected. VIM-35 had one substitution compared to VIM-1 (A235T) and a similar susceptibility profile. One or more resistance mechanisms were identified in 4/6 carbapenemase-negativeEnterobacteriaceae. This broad evaluation confirms results from country-specific surveys and shows a highly diverse population of carbapenemase-producing ACB andEnterobacteriaceaein Europe and Mediterranean countries.

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Molecular characterization and antibiotic resistance of Acinetobacter baumannii in cerebrospinal fluid and blood

PLoS ONE ◽

10.1371/journal.pone.0247418 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0247418

Author(s):

Xiaohong Shi ◽

Hong Wang ◽

Xin Wang ◽

Huaiqi Jing ◽

Ran Duan ◽

...

Keyword(s):

Cerebrospinal Fluid ◽

Infection Control ◽

Acinetobacter Baumannii ◽

Detection Rate ◽

Genetic Relatedness ◽

Treatment Options ◽

Carbapenem Resistance ◽

Control Measures ◽

Carbapenem Resistant ◽

Carbapenemase Gene

The increasing prevalence of carbapenem-resistant Acinetobacter baumannii (CRAB) caused nosocomial infections generate significant comorbidity and can cause death among patients. Current treatment options are limited. These infections pose great difficulties for infection control and clinical treatment. To identify the antimicrobial resistance, carbapenemases and genetic relatedness of Acinetobacter baumannii isolates from cerebrospinal fluid (CSF) and blood, a total of 50 nonrepetitive CSF isolates and 44 blood isolates were collected. The resistance phenotypes were determined, and polymerase chain reaction (PCR) was performed to examine the mechanisms of carbapenem resistance. Finally, multilocus sequence typing (MLST) was conducted to determine the genetic relatedness of these isolates. It was observed that 88 of the 94 collected isolates were resistant to imipenem or meropenem. Among them, the blaOXA-23 gene was the most prevalent carbapenemase gene, with an observed detection rate of 91.5% (86/94), followed by the blaOXA-24 gene with a 2.1% detection rate (2/94). Among all carbapenem-resistant Acinetobacter baumannii (CRAB) observations, isolates with the blaOXA-23 gene were resistant to both imipenem and meropenem. Interestingly, isolates positive for the blaOXA-24 gene but negative for the blaOXA-23 gene showed an imipenem-sensitive but meropenem-resistant phenotype. The MLST analysis identified 21 different sequence types (STs), with ST195, ST540 and ST208 most frequently detected (25.5%, 12.8% and 11.7%, respectively). 80 of the 94 isolates (85.1%) were clustered into CC92 which showed a carbapenem resistance phenotype (except AB13). Five novel STs were detected, and most of them belong to CRAB. In conclusion, these findings provide additional observations and epidemiological data of CSF and blood A. baumannii strains, which may improve future infection-control measures and aid in potential clinical treatments in hospitals and other clinical settings.

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Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii Isolates from Northern Africa and the Middle East

Antibiotics ◽

10.3390/antibiotics10030291 ◽

2021 ◽

Vol 10 (3) ◽

pp. 291

Author(s):

Paul G. Higgins ◽

Ralf Matthias Hagen ◽

Bernd Kreikemeyer ◽

Philipp Warnke ◽

Andreas Podbielski ◽

...

Keyword(s):

Middle East ◽

Acinetobacter Baumannii ◽

Resistance Genes ◽

Core Genome ◽

Carbapenem Resistance ◽

Resistance Mechanisms ◽

Northern Africa ◽

Carbapenem Resistant ◽

Next Generation Sequencing Ngs ◽

Injured Patients

At the Bundeswehr Hospitals of Hamburg and Westerstede, patients repatriated from subtropical war and crisis zones of Northern Africa and the Middle East were medically treated, including microbiological assessment. Within a six-year interval, 16 Acinetobacter spp. strains, including 14 Acinetobacter baumannii (Ab) isolates with resistance against carbapenems and origins in Afghanistan (n = 4), Iraq (n = 2), Libya (n = 2), and Syria (n = 8) were collected. While clonal relationships of Libyan and Syrian strains had been assessed by superficial next generation sequencing (NGS) and “DiversiLab” repetitive elements sequence-based (rep-)PCR so far, this study provides core genome-based sequence typing and thus more detailed epidemiological information. In detail, sequencing allowed a definitive species identification and comparison with international outbreak-associated Ab strains by core genome multi locus sequence typing (cgMLST) and the identification of MLST lineages, as well as the identification of known resistance genes. The sequence analysis allowed for the confirmation of outbreak-associated clonal clusters among the Syrian and Afghan Ab isolates, indicating likely transmission events. The identified acquired carbapenem resistance genes comprised blaOXA-23, blaOXA-58, blaNDM-1, and blaGES-11, next to other intrinsic and acquired, partly mobile resistance-associated genes. Eleven out of 14 Ab isolates clustered with the previously described international clonal lineages IC1 (4 Afghan strains), IC2 (6 Syrian strains), and IC7 (1 Syrian strain). Identified Pasteur sequence types of the 14 Ab strains comprised ST2 (Syrian), ST25 (Libyan), ST32 (Iraqi), ST81 (Afghan), ST85 (Libyan), and ST1112 (Syrian), respectively. In conclusion, the study revealed a broad spectrum of resistance genes in Ab isolated from war-injured patients from Northern Africa and the Middle East, thereby broadening the scarcely available data on locally abundant clonal lineages and resistance mechanisms.

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Molecular Epidemiology and Clone Transmission of Carbapenem-Resistant Acinetobacter baumannii in ICU Rooms

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.633817 ◽

2021 ◽

Vol 11 ◽

Author(s):

Xiufeng Zhang ◽

Fangping Li ◽

Furqan Awan ◽

Hongye Jiang ◽

Zhenling Zeng ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Insertion Sequence ◽

Core Genome ◽

Carbapenem Resistance ◽

Multidrug Resistant ◽

Chi Square ◽

The Core ◽

Carbapenem Resistant ◽

Significant Difference ◽

Chi Square Test

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major cause of nosocomial infections and hospital outbreaks worldwide, remaining a critical clinical concern. Here we characterized and investigated the phylogenetic relationships of 105 CRAB isolates from an intensive care unit from one hospital in China collected over six years. All strains carried blaOXA-23, blaOXA-66 genes for carbapenem resistance, also had high resistance gene, virulence factor, and insertion sequence burdens. Whole-genome sequencing revealed all strains belonged to ST2, the global clone CC2. The phylogenetic analysis based on the core genome showed all isolates were dominated by a single lineage of three clusters and eight different clones. Two clones were popular during the collection time. Using chi-square test to identify the epidemiologically meaningful groupings, we found the significant difference in community structure only existed in strains from separation time. The haplotype and median-joining network analysis revealed genetic differences appeared among clusters and changes occurred overtime in the dominating cluster. Our results highlighted substantial multidrug-resistant CRAB burden in the hospital ICU environment demonstrating potential clone outbreak in the hospital.

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

10.21203/rs.3.rs-38056/v2 ◽

2021 ◽

Author(s):

Shixing Liu ◽

Renchi Fang ◽

Ying Zhang ◽

Lijiang Chen ◽

Na Huang ◽

...

Keyword(s):

Sequence Analysis ◽

Membrane Protein ◽

Outer Membrane ◽

Lipid A ◽

Efflux Pump ◽

Medical Center ◽

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. Genetic clusters of based on hsp60 sequence analysis were performed. 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). hsp60 sequence analysis suggested 10 of 19 the strains belong to colistin hetero-resistant clusters 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.

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In vitro activity of sulbactam/durlobactam against global isolates of carbapenem-resistant Acinetobacter baumannii

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkaa208 ◽

2020 ◽

Vol 75 (9) ◽

pp. 2616-2621 ◽

Cited By ~ 2

Author(s):

Harald Seifert ◽

Carina Müller ◽

Danuta Stefanik ◽

Paul G Higgins ◽

Alita Miller ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Carbapenem Resistance ◽

Resistance Mechanisms ◽

The Novel ◽

In Vitro Activity ◽

Carbapenem Resistant ◽

Excellent Activity ◽

Acinetobacter Spp ◽

Lactamase Inhibitor

Abstract Objectives To evaluate the activity of the novel broad-spectrum serine β-lactamase inhibitor durlobactam (ETX2514) combined with sulbactam against global isolates of carbapenem-resistant Acinetobacter baumannii with defined carbapenem resistance mechanisms compared with reference antimicrobials with known activity against Acinetobacter spp. Methods The susceptibility of 246 carbapenem-resistant non-duplicate A. baumannii isolates to sulbactam/durlobactam, amikacin, colistin, imipenem/sulbactam/durlobactam, imipenem, meropenem, minocycline and sulbactam was tested using broth microdilution. Isolates were obtained from various body sites from patients in 37 countries and from six world regions between 2012 and 2016. Identification of carbapenem resistance mechanisms and assignment to A. baumannii clonal lineages was based on WGS. Results Sulbactam/durlobactam showed excellent activity comparable to colistin but superior to amikacin, minocycline and sulbactam. The sulbactam/durlobactam MIC50/90 values were 1/4 and 2/4 mg/L and the colistin MIC50/90 values were 0.5 and 1 mg/L, respectively. Comparatively, amikacin, minocycline and sulbactam MIC50/90 values were 256/≥512, 2/16 and 16/64 mg/L, respectively. Conclusions Sulbactam/durlobactam had excellent in vitro potency against A. baumannii isolates, including those that were resistant to imipenem/meropenem, amikacin, minocycline and colistin, compared with other compounds. Sulbactam/durlobactam has the potential to become a useful addition to the limited armamentarium of drugs that can be used to treat this problem pathogen.

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