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Surface-Related Features and Virulence Among Acinetobacter baumannii Clinical Isolates Belonging to International Clones I and II.

ABSTRACT: Acinetobacter baumannii currently represents one of the most important nosocomial infection agent due to its multidrug-resistance and a propensity for the epidemic spread. The A. baumannii strains belonging to the international clonal lineages I (IC I) and II (IC II) are associated with the hospital outbreaks and a high virulence. However, the intra and inter lineage-specific features of strains belonging to these most worldwide spread A. baumannii clones are not thoroughly explored. In this study we have investigated a set of cell surface-related features of A. baumannii IC I (n = 20) and IC II (n = 16) lineage strains, representing 30 distinct pulsed-field gel electrophoresis types in the collection of clinical isolates obtained in Lithuanian tertiary care hospitals. We show that A. baumannii IC II strains are non-motile, do not form pellicle and display distinct capsular polysaccharide profile compared with the IC I strains. Moreover, in contrast to the overall highly hydrophobic IC I strains, IC II strains showed a greater variation in cell surface hydrophobicity. Within the IC II lineage, hydrophilic strains demonstrated reduced ability to form biofilm and adhere to the abiotic surfaces, also possessed twofold thicker cell wall and exhibited higher resistance to desiccation. Furthermore, these strains showed increased adherence to the lung epithelial cells and were more virulent in nematode and mouse infection model compared with the hydrophobic IC II strains. According to the polymerase chain reaction-based locus-typing, the reduction in hydrophobicity of IC II strains was not capsule or lipooligosaccharide locus type-dependent. Hence, this study shows that the most widespread A. baumannii clonal lineages I and II markedly differ in the series of cell surface-related phenotypes including the considerable phenotypic diversification of IC II strains at the intra-lineage level. These findings suggest that the genotypically related A. baumannii strains might evolve the features which could provide an advantage at the specific conditions outside or within the host.

SUBMITTER: Skerniskyte J

PROVIDER: S-EPMC6331429 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Surface-Related Features and Virulence Among Acinetobacter baumannii Clinical Isolates Belonging to International Clones I and II.

Skerniškytė Jūratė J Krasauskas Renatas R Péchoux Christine C Kulakauskas Saulius S Armalytė Julija J Sužiedėlienė Edita E

Frontiers in microbiology 20190108

Acinetobacter baumannii currently represents one of the most important nosocomial infection agent due to its multidrug-resistance and a propensity for the epidemic spread. The A. baumannii strains belonging to the international clonal lineages I (IC I) and II (IC II) are associated with the hospital outbreaks and a high virulence. However, the intra and inter lineage-specific features of strains belonging to these most worldwide spread A. baumannii clones are not thoroughly ...[more]

PMID: 30671029

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Project description:Carbapenem-resistant Acinetobacter baumannii (CRAB) are emerging worldwide. In South America, clinical isolates presenting such a phenotype usually do not belong to the globally distributed international clone 2 (IC2). The majority of these isolates are also resistant to multiple other antimicrobials and are often designated extremely drug-resistant (XDR). The aim of this study was to characterize the resistance mechanisms presented by 18 carbapenem-resistant A. baumannii isolates from five different Brazilian hospitals. Species identification was determined by rpoB sequencing, and antimicrobial susceptibility was determined by broth microdilution. Isolates were submitted to whole genome sequencing using Illumina platform and genetic similarity was determined by PFGE, MLST, and cgMLST. Genome analysis was used to identify intrinsic and acquired resistance determinants, including mutations in the AdeRSABC efflux system and in outer membrane proteins (OMPs). All isolates were identified as A. baumannii and grouped into 4 pulsotypes by PFGE, which belonged to clonal complexes (CC) 15 Pas /103 Ox (n = 4) and 79 Pas /113 Ox (n = 14), corresponding to IC4 and IC5, respectively. High MIC values to carbapenems, broad-spectrum cephalosporins, amikacin, and ciprofloxacin were observed in all isolates, while MICs of ampicillin/sulbactam, gentamicin, and tigecycline varied among the isolates. Minocycline was the most active antimicrobial agent tested. Moreover, 12 isolates (66.7%) were considered resistant to polymyxins. Besides intrinsic OXA-51 and ADC variants, all isolates harbored an acquired carbapenem-hydrolyzing class D β-lactamase (CHDL) encoding gene, either bla OXA- 23 or bla OXA- 72. A diversity of aminoglycoside modifying enzymes and resistance determinants to other antimicrobial classes were found, as well as mutations in gyrA and parC. Non-synonymous mutations have also been identified in the AdeRSABC efflux system and in most OMPs, but they were considered natural polymorphisms. Moreover, resistance to polymyxins among isolates belonging to IC5 were associated to non-synonymous mutations in pmrB, but no known polymyxin resistance mechanism was identified in isolates belonging to IC4. In conclusion, A. baumannii clinical isolates belonging to South America's major clones present a myriad of antimicrobial resistance determinants. Special attention should be paid to natural polymorphisms observed in each clonal lineage, especially regarding non-synonymous mutations in constitutive genes associated with distinct resistance phenotypes.

Project description:Acinetobacter baumannii is a successful nosocomial pathogen due to its genomic plasticity. Homologous recombination allows genetic exchange and allelic variation among different clonal lineages and is one of the mechanisms associated with horizontal gene transfer (HGT) of resistance determinants. The main mechanism of colistin resistance in A. baumannii is mediated through mutations in the pmrCAB operon. Here, we describe two A. baumannii clinical isolates belonging to International Clone 7 (IC7) that have undergone recombination in the pmrCAB operon and evaluate the contribution of mobile genetic elements (MGE) to this phenomenon. Isolates 67569 and 72554 were colistin susceptible and resistant, respectively, and were submitted for short- and long-read genome sequencing using Illumina MiSeq and MinION platforms. Hybrid assemblies were built with Unicycler, and the assembled genomes were compared to reference genomes using NUCmer, Cortex, and SplitsTree. Genomes were annotated using Prokka, and MGEs were identified with ISfinder and repeat match. Both isolates presented a 21.5-kb recombining region encompassing pmrCAB. In isolate 67659, this region originated from IC5, while in isolate 72554 multiple recombination events might have happened, with the 5-kb recombining region encompassing pmrCAB associated with an isolate representing IC4. We could not identify MGEs involved in the mobilization of pmrCAB in these isolates. In summary, A. baumannii belonging to IC7 can present additional sequence divergence due to homologous recombination across clonal lineages. Such variation does not seem to be driven by antibiotic pressure but could contribute to HGT mediating colistin resistance. IMPORTANCE Colistin resistance rates among Acinetobacter baumannii clinical isolates have increased over the last 20 years. Despite reports of the spread of plasmid-mediated colistin resistance among Enterobacterales, the presence of mcr-type genes in Acinetobacter spp. remains rare, and reduced colistin susceptibility is mainly associated with the acquisition of nonsynonymous mutations in pmrCAB. We have recently demonstrated that distinct pmrCAB sequences are associated with different A. baumannii International Clones (IC). In this study, we identified the presence of homologous recombination as an additional cause of genetic variation in this operon, which, to the best of our knowledge, was not mediated by mobile genetic elements. Even though this phenomenon was observed in both colistin-susceptible and -resistant isolates, it has the potential to contribute to the spread of resistance-conferring alleles, leading to reduced susceptibility to this last-resort antimicrobial agent.

Project description:BACKGROUND: Acinetobacter baumannii is a significant hospital pathogen, particularly due to the dissemination of highly multidrug resistant isolates. Genome data have revealed that A. baumannii is highly genetically diverse, which correlates with major variations seen at the phenotypic level. Thus far, comparative genomic studies have been aimed at identifying resistance determinants in A. baumannii. In this study, we extend and expand on these analyses to gain greater insight into the virulence factors across eight A. baumannii strains which are clonally, temporally and geographically distinct, and includes an isolate considered non-pathogenic and a community-acquired A. baumannii. RESULTS: We have identified a large number of genes in the A. baumannii genomes that are known to play a role in virulence in other pathogens, such as the recently studied proline-alanine-alanine-arginine (PAAR)-repeat domains of the type VI secretion systems. Not surprising, many virulence candidates appear to be part of the A. baumannii core genome of virulent isolates but were often found to be insertionally disrupted in the avirulent A. baumannii strain SDF. Our study also reveals that many known or putative virulence determinants are restricted to specific clonal lineages, which suggests that these virulence determinants may be crucial for the success of these widespread common clones. It has previously been suggested that the high level of intrinsic and adaptive resistance has enabled the widespread presence of A. baumannii in the hospital environment. This appears to have facilitated the expansion of its repertoire of virulence traits, as in general, the nosocomial strains in this study possess more virulence genes compared to the community-acquired isolate. CONCLUSIONS: Major genetic variation in known or putative virulence factors was seen across the eight strains included in this study, suggesting that virulence mechanisms are complex and multifaceted in A. baumannii. Overall, these analyses increase our understanding of A. baumannii pathogenicity and will assist in future studies determining the significance of virulence factors within clonal lineages and/or across the species.

Project description:BackgroundAcinetobacter baumannii is responsible for large epidemics in hospitals, where it can persist for long time on abiotic surfaces. This study investigated some virulence-related traits of epidemic A. baumannii strains assigned to distinct MLST genotypes, including those corresponding to the international clones I-III as well as emerging genotypes responsible for recent epidemics.MethodsGenotyping of bacteria was performed by PFGE analysis and MLST according to the Pasteur's scheme. Biofilm formation on polystyrene plates was assessed by crystal violet staining; resistance to desiccation was evaluated on glass cover-slips when kept at room-temperature and 31% relative humidity; adherence to and invasion of A549 human alveolar epithelial cells were determined by the analysis of viable bacteria associated with or internalized by A549 human alveolar epithelial cells; Galleria mellonella killing assays were used to analyze the virulence of A. baumannii in vivo.ResultsThe ability to form biofilm was significantly higher for A. baumannnii strains assigned to ST2 (international clone II), ST25 and ST78 compared to other STs. All A. baumannii strains survived on dry surfaces for over 16 days, and strains assigned to ST1 (international clone I) and ST78 survived for up to 89 and 96 days, respectively. Adherence to A549 pneumocytes was higher for strains assigned to ST2, ST25 and ST78 than other genotypes; a positive correlation exists between adherence and biofilm formation. Strains assigned to ST78 also showed significantly higher ability to invade A549 cells. No significant differences in the killing of G. mellonella worms were found among strains.ConclusionsElevated resistance to desiccation, high biofilm-forming capacity on abiotic surfaces and adherence to A549 cells might have favoured the spread and persistence in the hospital environment of A. baumannii strains assigned to the international clones I and II and to the emerging genotypes ST25 and ST78.

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Surface-Related Features and Virulence Among Acinetobacter baumannii Clinical Isolates Belonging to International Clones I and II.

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Surface-Related Features and Virulence Among <i>Acinetobacter baumannii</i> Clinical Isolates Belonging to International Clones I and II.

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