Clonal spread of blaOXA-72-carrying Acinetobacter baumannii sequence type 512 in Taiwan

Complete genetic characterization of carbapenem-resistant Acinetobacter johnsonii, co-producing NDM-1, OXA-58, and PER-1 in a patient source

The emergence of carbapenemase-producing Acinetobacter spp. has been widely reported and become a global threat. However, carbapenem-resistant A. johnsonii strains are relatively rare and without comprehensive genetic structure analysis, especially for isolates collected from human specimen. Here, one A. johnsonii AYTCM strain, co-producing NDM-1, OXA-58, and PER-1 enzymes, was isolated from sputum in China in 2018. Antimicrobial susceptibility testing showed that it was resistant to meropenem, imipenem, ceftazidime, ciprofloxacin, and cefoperazone/sulbactam. Whole-genome sequencing and bioinformatic analysis revealed that it possessed 11 plasmids. bla OXA-58 and bla PER-1 genes were located in the pAYTCM-1 plasmid. Especially, a complex class 1 integron consisted of a 5' conserved segment (5' CS) and 3' CS, which was found to carry sul1, arr-3, qnrVC6, and bla PER-1 cassettes. Moreover, the bla NDM-1 gene was located in 41,087 conjugative plasmids and was quite stable even after 70 passages under antibiotics-free conditions. In addition, six prophage regions were identified. Tracking of closely related plasmids in the public database showed that pAYTCM-1 was similar to pXBB1-9, pOXA23_010062, pOXA58_010030, and pAcsw19-2 plasmids, which were collected from the strains of sewage in China. Concerning the pAYTCM-3 plasmids, results showed that strains were collected from different sources and their hosts were isolated from various countries, such as China, USA, Japan, Brazil, and Mexico, suggesting that a wide spread occurred all over the world. In conclusion, early surveillance is warranted to avoid the extensive spread of this high-risk clone in the healthcare setting.

GR13-type plasmids in Acinetobacter potentiate the accumulation and horizontal transfer of diverse accessory genes

Carbapenem and other antibiotic resistance genes (ARGs) can be found in plasmids in Acinetobacter, but many plasmid types in this genus have not been well-characterized. Here we describe the distribution, diversity and evolutionary capacity of rep group 13 (GR13) plasmids that are found in Acinetobacter species from diverse environments. Our investigation was prompted by the discovery of two GR13 plasmids in A. baumannii isolated in an intensive care unit (ICU). The plasmids harbour distinct accessory genes: pDETAB5 contains bla_NDM-1 and genes that confer resistance to four further antibiotic classes, while pDETAB13 carries putative alcohol tolerance determinants. Both plasmids contain multiple dif modules, which are flanked by pdif sites recognized by XerC/XerD tyrosine recombinases. The ARG-containing dif modules in pDETAB5 are almost identical to those found in pDETAB2, a GR34 plasmid from an unrelated A. baumannii isolated in the same ICU a month prior. Examination of a further 41 complete, publicly available plasmid sequences revealed that the GR13 pangenome consists of just four core but 1186 accessory genes, 123 in the shell and 1063 in the cloud, reflecting substantial capacity for diversification. The GR13 core genome includes genes for replication and partitioning, and for a putative tyrosine recombinase. Accessory segments encode proteins with diverse putative functions, including for metabolism, antibiotic/heavy metal/alcohol tolerance, restriction-modification, an anti-phage system and multiple toxin–antitoxin systems. The movement of dif modules and actions of insertion sequences play an important role in generating diversity in GR13 plasmids. Discrete GR13 plasmid lineages are internationally disseminated and found in multiple Acinetobacter species, which suggests they are important platforms for the accumulation, horizontal transmission and persistence of accessory genes in this genus.

Characterization of a small plasmid carrying the carbapenem resistance gene bla OXA-72 from community-acquired Acinetobacter baumannii sequence type 880 in China

Background

Acinetobacter baumannii has emerged as an important pathogen associated with hospital- and community-acquired infections. Community-acquired A. baumannii pneumonia is characterized by a fulminant course and high mortality rates. In this study, we report the identification of a community-acquired carbapenem-resistant A. baumannii strain carrying the bla _OXA-72 gene.

Methods

This A. baumannii isolate was recovered from a male patient diagnosed with community-acquired pneumonia, septic shock, and respiratory failure. Antimicrobial susceptibility testing were performed and the minimum inhibitory concentrations were determined by the broth microdilution method. Whole-genome sequencing was performed using both long-read MinION and short-read Illumina platforms to fully characterize the bla _OXA-72-carrying plasmid of the A. baumannii A52. The in silico multilocus sequence typing and genomic epidemiological analysis of the closely related isolates were further elucidated by our recently updated BacWGSTdb server.

Results

The isolate was resistant to meropenem and remained susceptible to several other antimicrobial agents. Whole-genome sequencing and bioinformatics analysis indicated that this A. baumannii isolate belonged to the rare sporadic clone sequence type 880 and the bla _OXA-72 gene was located on the 8,493-bp plasmid pA52-OXA-72. This plasmid exhibited only partial similarity to different OXA-72-encoding plasmids (size range: 8,771-12,056 bp) in various Acinetobacter spp. recovered from patients and other reservoirs in different countries.

Conclusion

This study described the first case of fulminant carbapenem-resistant community-acquired A. baumannii pneumonia caused by a rare sporadic clone in China. Adequate surveillance is warranted to monitor the emergence of A. baumannii as a community pathogen.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii in Greece: an extended review (2000–2015)

Carbapenem-resistant Acinetobacter baumannii (CRAB) is endemic in Greece. CRAB initially emerged in 2000 and since then, carbapenemases still have a crucial role in CRAB appearance, except for a few cases resulting from efflux pump or outer-membrane protein mechanisms. OXA-type carbapenemases present the highest prevalence worldwide and bla OXA-23-like and bla OXA-58-like are the most important genes found; VIM-yielding CRAB have also been detected, while a single CRAB isolate producing NDM has quite recently emerged in Greece. The predominant OXA-23 producers are associated with multilocus sequence typing Pasteur scheme sequence type 2 clonal strains of the international clone II. The emergence of colistin-resistant CRAB has complicated the treatment of such infections and the interpretation of susceptibility data. Infection control measures and adjusted antimicrobial treatment strategies could confine CRAB spread. The aim of this review is to go through the molecular epidemiology of CRAB, in an endemic area and highlight its potential future evolution.

Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized.