Temporal evolution of Acinetobacter baumannii ST107 clone: conversion of blaOXA-143 into blaOXA-231 coupled with mobilization of ISAba1 upstream occAB1

Spread of multidrug-resistant Acinetobacter baumannii isolates belonging to IC1 and IC5 major clones in Rondônia state

In Brazil, carbapenem-resistant A. baumannii (CRAB) is a critical pathogen showing high carbapenem resistance rates. Currently, there is little epidemiological data on A. baumannii isolated in the Northern Brazilian region. Herein, this study aimed to characterize the resistance mechanisms of CRAB isolates recovered from hospitalized patients in the state of Rondônia in 2019. Most of CRAB were considered as extensively drug-resistant, and some of them showed high MICs for minocycline. Only polymyxins showed a satisfactory activity. All isolates carried bla_OXA-23 and were included in 14 distinct clusters, with the predominance of clonal group A (29%). The IC1 was the most frequent clonal group, followed by IC5 and IC4. Here, we firstly reported the epidemiological scenario of CRAB in the state of Rondônia, located in the Brazilian Amazon region. The high frequency of CRAB presenting XDR phenotype is of great concern, due to limited therapeutical options, especially in the actual pandemic scenario, in which we observed an overcrowding of ICU beds. Such results are essential to better characterize the epidemiology of CRAB in the entire Brazilian territory.

Prevalence and Characterization of Carbapenem-Hydrolyzing Class D β-Lactamase-Producing Acinetobacter Isolates From Ghana

Multidrug resistance, especially carbapenem resistance in Acinetobacter bacteria is a global healthcare concern. However, available data on the phenotypic and genotypic characteristics of Acinetobacter isolates from West Africa, including Ghana is scanty. Our aim was to investigate the antibiotic resistance profile and genotypic characteristics of Acinetobacter isolates from Ghana and to characterize carbapenemase producers using whole-genome sequencing (WGS). A total of 36 Acinetobacter isolates collected at three hospitals in Ghana between 2016 and 2017 were analyzed. MICs were determined by commercial antibiotic plates. Acinetobacter baumannii MLST was determined using the Pasteur scheme. WGS of OXA-carbapenemase producers was performed using short- and long-read sequencing strategies. The resistance rate was highest for trimethoprim/sulfamethoxazole (n = 22; 61%). Six (16.7%) and eight (22.2%) isolates were resistant to ceftazidime and colistin, respectively. Two (5.6%) isolates were resistant and one (2.8%) isolate had intermediate sensitivity to three carbapenems. Fifteen STs were identified in 24 A. baumannii isolates including six new STs (ST1467 ∼ ST1472). ST78 was the predominant (n = 6) followed by ST1469 (n = 3). Four carbapenemase-producing A. baumannii isolates also were identified. Isogenic ST103 isolates Ab-B004d-c and Ab-D10a-a harbored bla_OXA–23 within Tn2007 on identical plasmids, pAb-B004d-c_3, and pAb-D10a-a_3. ST1472 isolate Ab-C102 and ST107 isolate Ab-C63 carried bla_OXA–58 and bla_OXA–420, a rare bla_OXA–58 variant, respectively, within novel genetic contexts. Our results show that A. baumannii isolates of diverse and unique genotypes, including OXA-carbapenemase producers, are circulating in Ghana highlighting the need for a wider surveillance of antimicrobial resistance.

The Outer Membrane Proteins OmpA, CarO, and OprD of Acinetobacter baumannii Confer a Two-Pronged Defense in Facilitating Its Success as a Potent Human Pathogen

Of all the ESKAPE pathogens, carbapenem-resistant and multidrug-resistant Acinetobacter baumannii is the leading cause of hospital-acquired and ventilator-associated pneumonia. A. baumannii infections are notoriously hard to eradicate due to its propensity to rapidly acquire multitude of resistance determinants and the virulence factor cornucopia elucidated by the bacterium that help it fend off a wide range of adverse conditions imposed upon by host and environment. One such weapon in the arsenal of A. baumannii is the outer membrane protein (OMP) compendium. OMPs in A. baumannii play distinctive roles in facilitating the bacterial acclimatization to antibiotic- and host-induced stresses, albeit following entirely different mechanisms. OMPs are major immunogenic proteins in bacteria conferring bacteria host-fitness advantages including immune evasion, stress tolerance, and resistance to antibiotics and antibacterials. In this review, we summarize the current knowledge of major A. baumannii OMPs and discuss their versatile role in antibiotic resistance and virulence. Specifically, we explore how OmpA, CarO, and OprD-like porins mediate antibiotic and amino acid shuttle and host virulence.

Diversity of metallo-β-lactamase-encoding genes found in distinct species of Acinetobacter isolated from the Brazilian Amazon Region

BACKGROUND

The multidrug resistance (MDR) phenotype is frequently observed in Acinetobacter baumannii, the most clinically relevant pathogenic species of its genus; recently, other species belonging to the A. calcoaceticus-A. baumannii complex have emerged as important MDR nosocomial pathogens.

OBJECTIVES

The present study aimed to verify the occurrence of metallo-β-lactamase genes among distinct Acinetobacter species in a hospital located in the Brazilian Amazon Region.

METHODS

Antimicrobial susceptibility profiles were determined by broth microdilution. The genetic relationships among these isolates were assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Pyrosequencing reads of plasmids carrying the bla_NDM-1 gene were generated using the Ion Torrent™ platform sequencing.

FINDINGS

A total of six isolates carried bla_NDM-1: A. baumannii (n = 2), A. nosocomialis (n = 3), and A. pittii (n = 1); three carried bla_IMP-1: A. baumannii, A. nosocomialis, and A. bereziniae. Resistance to colistin was observed for an NDM-1-producing A. nosocomialis isolate. Diverse PFGE patterns and sequence types were found among A. nosocomialis and A. baumannii isolates. The bla_NDM-1 sequence was inserted in a Tn125 transposon, while the bla_IMP-1 was found as a gene cassette of the class 1 integron In86.

MAIN CONCLUSIONS

To the best of our knowledge, this is the first report describing the dissemination of bla_NDM-1 among distinct Acinetobacter species recovered from the same hospital in South America.

Phenotypic and Genotypic Characterization of Clinical Isolates Belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) Complex Isolated From Animals Treated at a Veterinary Hospital in Switzerland

Objectives: We investigated a collection of strains belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex obtained from a veterinary clinic with regard to their genetic relatedness, presence of antibiotic resistance genes and antimicrobial susceptibility profiles.

Methods: Fifty-eight ACB-complex strains from animals treated at a veterinary clinic between 2006 and 2017, and seven strains collected from the hospital environment during 2012 were analyzed. Assignment to sequence types (ST) and international complexes (IC) was done by multilocus sequence typing (MLST) according to the Pasteur scheme. Genes encoding carbapenemases, aminoglycoside-modifying enzymes, macrolide-, quinolone- and co-trimoxazole resistance genes, the ISAba1 element, virulence associated intI1 genes and plasmid associated toxin-antitoxin markers were identified by microarray. Genes encoding bla_OXA−51-like carbapenemases were amplified by PCR and sequenced. Susceptibility profiles were determined by disc diffusion or by broth microdilution.

Results: Among 50 A. baumannii isolates from animals, two predominant clones were observed linked to CC1 (n = 27/54% of the isolates) and CC25 (n = 14/28%), respectively. Strains of IC I harbored bla_OXA−69, aac(3′)-la, aadA1, sul1, intI1, and splA/T genes. Isolates belonging to CC25 possessed bla_OXA−64. Six (12%) isolates belonging to CC2 and carrying bla_OXA−66 were also noted. One isolate belonged to CC10 (bla_OXA−68), one to CC149 (bla_OXA−104), the remaining isolate was assigned to ST1220 and possessed bla_OXA−116. Of six environmental A. baumannii, four (66.7%) belonged to CC25 (bla_OXA−64), one (16.7%) to CC2 (bla_OXA−66) and one to CC3 (bla_OXA−71). Nine isolates (eight from animals and one environmental strain) were non-baumannii strains and did not harbor bla_OXA−51-like genes. None of the isolates carried bla_OXA−23, bla_OXA−48, or bla_OXA−58, and none were resistant to carbapenems.

Conclusions: Clonal lineages of the veterinary A. baumannii isolates in our collection are identical to those globally emerging in humans but do not harbor bla_OXA−23. A. baumannii CC25 may be specific for this particular veterinary clinic environment.

Emergence and Persistence of High-Risk Clones Among MDR and XDR A. baumannii at a Brazilian Teaching Hospital

Dissemination of carbapenem-resistant Acinetobacter baumannii is currently one of the priority themes discussed around the world, including in Brazil, where this pathogen is considered endemic. A total of 107 carbapenem-resistant A. baumannii (CRAB) isolates were collected from patients with bacteraemia attended at a teaching hospital in Brazil from 2008 to 2014. From these samples, 104 (97.2%) carried bla_{OXA−23−like}, all of them associated with ISAba1 The bla_OXA−231 (1.9%) and bla_OXA−72 (0.9%) genes were also detected in low frequencies. All isolates were susceptible to minocycline, and 38.3% of isolates presented intermediate susceptibility to tigecycline (MIC = 4 μg/ml). Molecular typing assessed by multi-locus sequence typing demonstrated that the strains were mainly associated with clonal complexes CC79 (47.4%), followed by CC1 (16.9%), and CC317 (18.6%), belonging to different pulsotypes and in different prevalences over the years. Changes in the clones' prevalence reinforce the need of identifying and controlling CRAB in hospital settings to preserve the already scarce therapeutic options available.