Acinetobacter Baumannii Strains Research Articles

Impact of nutritional factors on in vitro PK/PD modelling of polymyxin B against various strains of Acinetobacter baumannii

The main objective of this study was to assess the effect of rich artificial cation adjusted Mueller-Hinton broth (CAMHB), on the growth of three Acinetobacter baumannii strains, ATCC 19606 and two clinical A. baumannii strains, either susceptible or resistant to polymyxin B (PMB), and on the PMB bactericidal activity. A pharmacokinetic (PK) / pharmacodynamic (PD) modelling approach was then used to characterize the effect of PMB in various conditions.Time-kill experiments were performed using undiluted CAMHB or diluted at 50%, 25% and 10%, with or without Ca2+ and Mg2+ compensation (known to affect PMB activity), and with PMB concentrations ranging from 0.25 mg/L to 256 mg/L based on the strain's MIC. For each strain, time-kill replicates were modelled using NONMEM®.Unexpectedly, CAMHB dilution by up to 10-fold did not affect the growth rate of any of the three strains in the absence of PMB. Yet, PMB bactericidal activity increased with medium dilution resulting in particular in a reduction of the apparent bacterial regrowth of the various strains observed typically after few hours of experiment. The data of each strain were well characterised by a PK/PD model with two bacterial sub-populations with different susceptibility to PMB (a more susceptible (S+) and a less susceptible (S−)). Relatively large, unexplained strain-to-strain variability was observed regarding the impact of medium dilution as well as cation compensation. Complementary experiments are needed to characterise the mechanism underlying this medium dilution effect.

Bactericidal effect of bacteria isolated from the marine sponges Hymeniacidon perlevis and Halichondria panicea against carbapenem-resistant Acinetobacter baumannii.

In this study, we evaluated the antimicrobial activity of bacteria isolated from the marine sponges Hymeniacidon perlevis and Halichondria panicea against seven Acinetobacter baumannii strains, the majority of which were clinically relevant carbapenem-resistant A. baumannii strains. We observed the inhibitory activity of 18 (out of 114) sponge-isolated bacterial strains against all A. baumanii strains using medium-throughput solid agar overlay assays. These inhibitory strains belonged to the genera Lactococcus, Pseudomonas, and Vagococcus. In addition, this antimicrobial activity was validated through a liquid co-cultivation challenge using an inhibitory strain of each genus and a green fluorescent protein-tagged A. baumanii strain. Fluorescence measurements indicated that the growth of A. baumanii was inhibited by the sponge isolates. In addition, the inability of A. baumanii to grow after spreading the co-cultures on solid medium allowed us to characterize the activity of the sponge isolates as bactericidal. In conclusion, this study demonstrates that marine sponges are a reservoir of bacteria that deserves to be tapped for antibiotic discovery against A. baumanii.

Sprayable biogenic Ag-collagen nanocomposites with potent antibacterial and antibiofilm activity for Acinetobacter baumannii infected wound healing under hyperglycemic condition

Owing to their susceptibility to infection by drug-resistant bacteria, refractory wounds pose a formidable risk to the well-being of patients with diabetes and other immune-compromised conditions, and their management poses significant economic distress to the healthcare system, particularly in low and middle-income countries. Therefore, deployable interventions for rapid and effective management of such wounds are needed. In the present study, we report the processing of sprayable biogenic Ag-collagen nanocomposites (Ag-Col NCs) with cogent antibacterial and healing activity in Acinetobacter baumannii infected wounds under hyperglycemic conditions. Silver nanoparticles (Ag NPs) has been synthesized by using the plant extract of Urginea indica (U. indica), which was further used for the processing of Ag-Col NCs. Synthesized NCs were found to have notable broad spectrum antibacterial activity against clinically significant strains (Acinetobacter baumannii, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus) and appreciable biocompatibility towards RAW 264.7 and 3 T3 mouse fibroblast cell lines. The sprayable NC system was found to promote the wound healing activity in mouse model (Balb/c) not only in normal but also in hyperglycemic conditions. Our experimental findings suggest the potential of the Ag-Col NC spray in chronic wound management and an exploitable option in both clinical and personalized settings.

Development of novel indole-quinoline hybrid molecules targeting bacterial proton motive force.

This study aimed to develop an editable structural scaffold for improving drug development, including pharmacokinetics and pharmacodynamics of antibiotics by using synthetic compounds derived from a (hetero)aryl-quinoline hybrid scaffold. In this study, 18 CF3-substituted (hetero)aryl-quinoline hybrid molecules were examined for their potential antibacterial activity against Staphylococcus aureus by determining minimal inhibitory concentrations. These 18 synthetic compounds represent modifications to key regions of the quinoline N-oxide scaffold, enabling us to conduct a structure-activity relationship analysis for antibacterial potency. Among the compounds, 3m exhibited potency against with both methicillin resistant S. aureus strains, as well as other Gram-positive bacteria, including Enterococcus faecalis and Bacillus subtilis. We demonstrated that 3m disrupted the bacterial proton motive force (PMF) through monitoring the PMF and conducting the molecular dynamics simulations. Furthermore, we show that this mechanism of action, disrupting PMF, is challenging for S. aureus to overcome. We also validated this PMF inhibition mechanism of 3m in an Acinetobacter baumannii strain with weaken lipopolysaccharides. Additionally, in Gram-negative bacteria, we demonstrated that 3m exhibited a synergistic effect with colistin that disrupts the outer membrane of Gram-negative bacteria. Our approach to developing editable synthetic novel antibacterials underscores the utility of CF3-substituted (hetero)aryl-quinoline scaffold for designing compounds targeting the bacterial proton motive force, and for further drug development, including pharmacokinetics and pharmacodynamics.

In vivo single-cell high-dimensional mass cytometry analysis to track the interactions between Klebsiella pneumoniae and myeloid cells.

In vivo single-cell approaches have transformed our understanding of the immune populations in tissues. Mass cytometry (CyTOF), that combines the resolution of mass spectrometry with the ability to conduct multiplexed measurements of cell molecules at the single cell resolution, has enabled to resolve the diversity of immune cell subsets, and their heterogeneous functionality. Here we assess the feasibility of taking CyTOF one step further to immuno profile cells while tracking their interactions with bacteria, a method we term Bac-CyTOF. We focus on the pathogen Klebsiella pneumoniae interrogating the pneumonia mouse model. Using Bac-CyTOF, we unveil the atlas of immune cells of mice infected with a K. pneumoniae hypervirulent strain. The atlas is characterized by a decrease in the populations of alveolar and monocyte-derived macrophages. Conversely, neutrophils, and inflammatory monocytes are characterized by an increase in the subpopulations expressing markers of less active cells such as the immune checkpoint PD-L1. These are the cells infected. We show that the type VI secretion system (T6SS) contributes to shape the lung immune landscape. The T6SS governs the interaction with monocytes/macrophages by shifting Klebsiella from alveolar macrophages to interstitial macrophages and limiting the infection of inflammatory monocytes. The lack of T6SS results in an increase of cells expressing markers of active cells, and a decrease in the subpopulations expressing PD-L1. By probing Klebsiella, and Acinetobacter baumannii strains with limited ability to survive in vivo, we uncover that a heightened recruitment of neutrophils, and relative high levels of alveolar macrophages and eosinophils and the recruitment of a characteristic subpopulation of neutrophils are features of mice clearing infections. We leverage Bac-CyTOF-generated knowledge platform to investigate the role of the DNA sensor STING in Klebsiella infections. sting-/- infected mice present features consistent with clearing the infection including the reduced levels of PD-L1. STING absence facilitates Klebsiella clearance.

A hypervirulent Acinetobacter baumannii strain has robust anti-phagocytosis ability

BackgroundAcinetobacter baumannii (A. baumannii) is associated with both hospital-acquired infections (HAP) and community-acquired pneumonia (CAP). In this study, we present a novel CAP-associated A. baumannii (CAP-AB) strain causing severe pneumonia in an afore healthy male patient without underlying conditions. Subsequently, we investigated the pathogenicity and immunogenicity of this CAP-AB strain using a mice pneumonia model.ResultsA 58-year-old male patient with no underlying conditions experienced worsening symptoms of a productive cough, sputum, and fever that developed acutely, in just 24 h. The diagnosis was severe community-acquired pneumonia (CAP) and type-1 respiratory failure. An A. baumannii strain was isolated from his sputum and blood cultures. To gain a deeper understanding of the rapid progression of its pathology, we utilized the CAP-associated A. baumannii strain YC128, a previously obtained hospital-acquired pneumonia A. baumannii (HAP-AB) strain YC156, and a highly virulent A. baumannii control strain LAC-4 to construct a mouse pneumonia model, and subsequently compared the mortality rate of the three groups. Following inoculation with 107 CFU of A. baumannii, the mortality rate for the YC128, LAC-4, and YC156 groups was 60% (6/10), 30% (3/10), and 0%, respectively. The bacterial burden within the pulmonary, liver, and spleen tissues of mice in the YC128 group was significantly higher than that of the YC156 group, and slightly higher than that of the LAC-4 group. Pathological analysis of lung tissue using HE-staining revealed that the inflammatory pathological changes in mice from the YC128 group were significantly more severe than those in the YC156 group. Additionally, CT scan images displayed more pronounced inflammation in the lungs of mice from the YC128 group compared to the YC156 group. Local levels of cytokines/chemokines such as IL-1β, IL-6, TNF-α, and CXCL1 were assessed via RT-qPCR in lung tissues. In comparison with the YC156 strain, the highly virulent YC128 strain induced the expression of proinflammatory cytokines more rapidly and severely. Furthermore, we examined the in vitro anti-phagocytosis ability of YC128 and YC156 strains against mice peritoneal macrophages, revealing that the highly virulent YC128 isolate displayed greater resistance to macrophage uptake in contrast to YC156. Results from Whole Genome Sequencing (WGS) indicated that YC128 harbored a complete type VI secretion system (T6SS) gene cluster, while YC156 lacked the majority of genes within the T6SS gene cluster. The other virulence-related genes exhibited minimal differences between YC128 and YC156. Drawing from previous studies, we postulated that the T6SS is linked to the hypervirulence and robust anti-phagocytic ability of YC128.ConclusionsThis article reports on the isolation of a novel hypervirulent CAP-AB strain, YC128, from a severe CAP patient. The results demonstrate that this CAP-AB strain, YC128, is capable of inducing fatal pneumonia and extrapulmonary dissemination in a mouse pneumonia model. Moreover, this highly virulent CAP-AB strain exhibits significantly stronger anti-phagocytic abilities compared to the HAP-AB YC156 strain. Genome sequencing comparisons reveal that the heightened hypervirulence and enhanced anti-phagocytosis abilities observed in YC128 may be attributed to the presence of the T6SS.

The Whole genome sequence for Acinetobacter baumannii strain in Iraqi Hospitals Outbreak

A study was conducted to identify specialized F plasmid genes and regulatory systems in Acinetobacter baumannii. These genes could be very important for the capacity of these species to coexist with the human host and show a wide range of diversity in genes that contribute to antibiotic resistance. Identification of 50A. baumannii isolates was carried out through morphology and culture on CHROM agar and genotypic identification was performed using blaOxa-51 gene. Out of 50, one AB isolate was chosen for whole genome sequencing (WGS) using Illumina MiSeq technology. The analysis identified specialized genes in these isolates that contribute to antibiotic stress and lipopolysaccharide barrier, including complex sets of partial and complete integrons and transposons. The recent findings, transferring of A. baumannii plasmid genes are inducing under the regulatory system to which the plasmid elements confer Adaptation such as F-plasmid genes transfer in A.baumannii induced by antibiotic stress under the control of transcriptional factor regulation system in order to antimicrobial drug resistance. The selected A. baumannii isolate, IS1- A.baumannii 32 contain five global regulator systems .Our study were provided detailed genomic picture in detected both innate and acquired plasmid-encoded AMR genes. Study aim is the role of genetic regulation to control the transcription, virulence factors and antibiotic resistance related mechanism in A.baumannii .

A multiplex RPA coupled with CRISPR-Cas12a system for rapid and cost-effective identification of carbapenem-resistant Acinetobacter baumannii.

Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a severe nosocomial threat, prompting a need for efficient detection methods. Traditional approaches, such as bacterial culture and PCR, are time-consuming and cumbersome. The CRISPR-based gene editing system offered a potential approach for point-of-care testing of CRAB. We integrated recombinase polymerase amplification (RPA) and CRISPR-Cas12a system to swiftly diagnose CRAB-associated genes, OXA-51 and OXA-23. This multiplex RPA-CRISPR-Cas12a system eliminates bulky instruments, ensuring a simplified UV lamp-based outcome interpretation. Operating at 37°C to 40°C, the entire process achieves CRAB diagnosis within 90 minutes. Detection limits for OXA-51 and OXA-23 genes are 1.3 × 10-6 ng/μL, exhibiting exclusive CRAB detection without cross-reactivity to common pathogens. Notably, the platform shows 100% concordance with PCR when testing 30 clinical Acinetobacter baumannii strains. In conclusion, our multiplex RPA coupled with the CRISPR-Cas12a system provides a fast and sensitive CRAB detection method, overcoming limitations of traditional approaches and holding promise for efficient point-of-care testing.

In vitro activity of human defensins HNP-1 and hBD-3 against multidrug-resistant ESKAPE Gram-negatives of clinical origin and selected peptidoglycan recycling-defective mutants.

In the current scenario of critical need for new antimicrobials against multidrug-resistant bacteria, all options must be considered, including classic ideas such as the use of purified immune compounds. However, information regarding the activity of certain human defensins against ESKAPE Gram-negatives was incomplete. This is the first study comparatively assessing the in vitro activity of two membrane-permeabilizing/peptidoglycan construction-blocking defensins (HNP-1 and hBD-3) against relevant clinical collections of ESKAPE Gram-negatives, alone or in combination with permeabilizers, additional peptidoglycan-targeting attacks, or the blockade of its recycling. Our data suggest that hBD-3 has a notable bactericidal activity against multidrug-resistant Acinetobacter baumannii and Enterobacter cloacae strains that should be considered as potential adjuvant option. Our results suggest for the first time an increased resistance of Pseudomonas aeruginosa strains from chronic infection compared to acute origin ones, and provide new clues about the predominant mode of action of hBD-3 against Gram-negatives (permeabilization rather than peptidoglycan-targeting).

A multicentre evaluation of the NG-test DetecTool OXA-23 for the rapid detection of OXA-23 carbapenemase directly from blood cultures.

A multicentre study evaluating NG-Test DetecTool OXA-23 for the detection of OXA-23 carbapenemase directly from positive blood cultures (PBCs). The NG-Test DetecTool OXA-23 is an immunoassay that integrates a sample preparation device. We evaluated NG-Test DetecTool OXA-23 on 189 spiked and 126 clinical PBCs. The clinical samples' standard-of-care procedure consisted of bacterial identification from the first day of positivity by MALDI-TOF MS, conventional culture and antimicrobial susceptibility testing. The immunoassay results were verified molecularly. The strains used for the spiked samples consisted of well-characterized Acinetobacter baumannii and Proteus mirabilis strains. The NG-Test DetecTool OXA-23 was evaluated on 315 PBCs and revealed sensitivity of 100% (95% CI: 98.21%-100.00%) and specificity of 100% (95% CI: 96.73%-100.00%). It provided 204 true-positive results for OXA-23 in 196 bottles with carbapenem-resistant A. baumannii (CRAB) and 8 bottles with carbapenem-resistant P. mirabilis and also provided 111 true-negative results. There were no false-positive and no false-negative results. Among the 315 PBCs studied, 83 clinical blood cultures collected in the ICU of a Greek university hospital, which were tested prospectively, all yielded CRAB, and OXA-23 was correctly detected in all samples from the first day of positivity using the NG-Test DetecTool OXA-23. The NG-Test DetecTool OXA-23 has exhibited excellent sensitivity and specificity for OXA-23 detection in PBCs and can provide valuable information for appropriate selection of antibiotic therapy and early implementation of infection control measures.

Characterization of two bacteriophages specific to Acinetobacter baumannii and their effects on catheters biofilm.

Multidrug-resistant strains of Acinetobacter baumannii cause major nosocomial infections. Bacteriophages that are specific to the bacterial species and destroy bacteria can be effectively used for treatment. In this study, we characterized lytic bacteriophages specific to A. baumannii strains. We isolated lytic bacteriophages from environmental water samples and then investigated their morphology, host range, growth characteristics, stability, genome analysis, and biofilm destruction on the catheter surface. Our results showed that the efficacy of the phages varied between 32% and 78%, tested on 78 isolates of A. baumannii; 80 phages were isolated, and two lytic bacteriophages, vB_AbaP_HB01 (henceforth called C2 phage) and vB_AbaM_HB02 (henceforth called K3 phage), were selected for characterization. Electron microscopy scans revealed that the C2 and K3 phages were members of the Podoviridae and Myoviridae families, respectively. Whole-genome sequencing revealed that the sequence of the C2 phage is available in the NCBI database (accession number: OP917929.1), and it was found sequence identity with Acinetobacter phage AB1 18%, the K3 phage DNA sequence is closely related to Acinetobacter phage vB_AbaM_phiAbaA1 (94% similarity). The cocktail of C2 and K3 phages demonstrated a promising decrease in the bacterial cell counts of the biofilm after 4 h. Under a scanning electron microscope, the cocktail treatment destructed the biofilm on the catheter. We propose that the phage cocktail could be a strong alternative to antibiotics to control the A. baumannii biofilm in catheter infections.

Isolation and Identification of Effective Probiotics on Drug-Resistant Acinetobacter baumannii Strains and Their Biofilms.

This study aimed to identify, assess, and isolate strong lactobacilli demonstrating broad antibacterial and anti-biofilm activity against drug-resistant strains of Acinetobacter baumannii. Additionally, the mechanism of inhibition of these organisms was to be determined. Over a 6-month period (from December 2021 to June 2022), 53 clinical A. baumannii strains were collected from clinical samples. Twenty probiotic strains were isolated from local dairy products. Antibacterial activity of Lactobacillus strains' cell-free supernatant (CFS) was identified using the agar well diffusion method and the microbroth dilution test. Anti-biofilm effect was performed by the microtiter plate assay. The MTT assay was also used to look into the probiotics' cytotoxic effects on the L929 fibroblast cell line. During the 6-month period, 53 clinical A. baumannii strains were obtained and identified. Out of 20 lactobacillus strains, the CFS of a lactobacillus strain (named L9) showed an inhibitory effect against all A. baumannii strains. Using the broth microdilution method, it was shown that the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of CFS extracts of L9 strains against A. baumannii strains were both ¼ mg/mL. The result of the anti-biofilm showed that the selected probiotic could inhibit biofilm formation. The most common organic acid produced by all Lactobacillus strains, according to the HPLC method, was lactic acid, which was followed by acetic acid. The L929 fibroblast cell line was used in the cytotoxicity assay, which revealed that 100% of the cells in the L929 fibroblast cell line survived treatment with successive doses of CFSs for a full day. The probiotic strain isolated from local yogurt in this study showed potential anti-biofilm and antimicrobial properties against all drug-resistant Acinetobacter isolates. Given the increasing interest in probiotic microorganisms based on their high health benefits, further studies are recommended on the mechanisms of action between probiotics and A. baumannii strains to find new solutions for biological control and treatment of these infections without the use of antibiotics.

Discovery of a Monoclonal Antibody That Targets Cell-Surface Pseudaminic Acid of Acinetobacter baumannii with Direct Bactericidal Effect.

The therapeutic effects of antibodies include neutralization of pathogens, activation of the host complement system, and facilitation of phagocytosis of pathogens. However, antibody alone has never been shown to exhibit bactericidal activity. In this study, we developed a monoclonal antibody that targets the bacterial cell surface component Pseudaminic acid (Pse). This monoclonal antibody, Pse-MAB1, exhibited direct bactericidal activity on Acinetobacter baumannii strains, even in the absence of the host complements or other immune factors, and was able to confer a protective effect against A. baumannii infections in mice. This study provides new insight into the potential of developing monoclonal antibody-based antimicrobial therapy of multidrug resistant bacterial infections, especially those which occurred among immunocompromised patients.

Molecular study of blaVIM and blaIMP genes in Acinetobacter baumannii strains isolated from burn patients in Duhok City, Iraq.

Acinetobacter baumannii (A. baumannii) is an opportunistic pathogenic bacterium mainly associated with hospital acquired infections and in immunocompromised individuals who stay in hospitals for a long time. In recent years, it has become increasingly resistant to many different types of antibiotics. The production of the metallo-beta-lactamase (MBL) enzyme is one of the primary causes of this resistance. This study aimed to detect the presence of MBL genes that belong to the verona integrin metallo-β-lactamase (bla-VIM) and imipenemase (bla-IMP) groups in the isolates of Acinetobacter baumannii from burn patients. One hundred and seventeen (117) isolates of A. baumannii were obtained from patient specimens using traditional methods followed by using the VITEK 2 (BioMérieux, Les Pennes-Mirabeau, France) identification system. Metallo β-lactamases were detected in the imipenem-resistant strains by using imipenem disks on Muller-Hinton agar. The polymerase chain reaction (PCR) technique was utilized to examine 117 isolates for the detection of MBLs encoding genes such as bla-VIM, and bla-IMP. Imipenem resistance was detected in 78.6% of the patients. The PCR assays of the isolates identified bla-VIM-1, bla-VIM-2, bla-IMP-1 and bla-IMP-2 genes at the rates of 17%, 40.1%, 29.9% and 4.2%, respectively. The findings suggest that the majority of A. baumannii isolates harbour one or more of the detected genes, signifying that the production of MBLs plays a pivotal role in resistance mechanisms.

Engineering of a decellularized bovine skin coated with antibiotics-loaded electrospun fibers with synergistic antibacterial activity for the treatment of infectious wounds.

An ideal antibacterial wound dressing with strong antibacterial behavior versus highly drug-resistant bacteria and great wound-healing capacity is still being developed. There is a clinical requirement to progress the current clinical cares that fail to fully restore the skin structure due to post-wound infections. Here, we aim to introduce a novel two-layer wound dressing using decellularized bovine skin (DBS) tissue and antibacterial nanofibers to design a bioactive scaffold with bio-mimicking the native extracellular matrix of both dermis and epidermis. For this purpose, polyvinyl alcohol (PVA)/chitosan (CS) solution was loaded with antibiotics (colistin and meropenem) and electrospun on the surface of the DBS scaffold to fabricate a two-layer antibacterial wound dressing (DBS-PVA/CS/Abs). In detail, the characterization of the fabricated scaffold was conducted using biomechanical, biological, and antibacterial assays. Based on the results, the fabricated scaffold revealed a homogenous three-dimensional microstructure with a connected pore network, a high porosity and swelling ratio, and favorable mechanical properties. In addition, according to the cell culture result, our fabricated two-layer scaffold surface had a good interaction with fibroblast cells and provided an excellent substrate for cell proliferation and attachment. The antibacterial assay revealed a strong antibacterial activity of DBS-PVA/CS/Abs against both standard strain and multidrug-resistant clinical isolates of Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Our bilayer antibacterial wound dressing is strongly suggested as an admirable wound dressing for the management of infectious skin injuries and now promises to advance with preclinical and clinical research.

Lipid nanoparticles based on natural matrices with activity against multidrug resistant bacterial species.

Lately, the bacterial multidrug resistance has been a reason to public health concerning around world. The development of new pharmacology therapies against infections caused by multidrug-resistant bacteria is urgent. In this work, we developed 10 NLC formulations composed of essential oils (EO), vegetable butter and surfactant. The formulations were evaluated for long-term and thermal cycling stability studies in terms of (particle size, polydispersion index and Zeta potential). In vitro antimicrobial assays were performed using disk diffusion test and by the determination of the minimum inhibitory concentration (MIC) performed with fresh and a year-old NLC. The most promising system and its excipients were structurally characterized through experimental methodologies (FTIR-ATR, DSC and FE-SEM). Finally, this same formulation was studied through nanotoxicity assays on the chicken embryo model, analyzing different parameters, as viability and weight changes of embryos and annexes. All the developed formulations presented long-term physicochemical and thermal stability. The formulation based on cinnamon EO presented in vitro activity against strains of Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa isolated from humans and in vivo biocompatibility. Considering these promising results, such system is able to be further tested on in vivo efficacy assays.

Comparative genomics and characterization of a multidrug-resistant Acinetobacter baumannii VRL-M19 isolated from a crowded setting in India

A crowded vegetable market serves as a mass gathering, posing a potential risk for infection transmission. In this study, we isolated a multidrug-resistant Acinetobacter baumannii strain, VRL-M19, from the air of such a market and conducted comparative genomics and phenotypic characterization. Antimicrobial susceptibility testing, genome sequencing using Illumina HiSeq X10, and pan-genome analysis with 788 clinical isolates identified core, accessory, and unique drug-resistant determinants. Mutational analysis of drug-resistance genes, virulence factor annotation, in vitro pathogenicity assessment, subsystem analysis, Multilocus sequence typing, and whole genome phylogenetic analysis were performed. VRL-M19 exhibited multidrug resistance with 69 determinants, and analysis across 788 clinical isolates and 350 Indian isolates revealed more accessory genes (52 out of 69) in the Indian isolates. Multiple mutations were observed in drug target modification genes, and the strain was identified as a moderate biofilm-former with 55 virulence factors. Whole genome phylogenetics indicated a close relationship between VRL-M19 and clinical A. baumannii strains. In conclusion, our comprehensive study suggests that VRL-M19 is a multidrug-resistant, potential pathogen with biofilm-forming capabilities, closely associated with clinical A. baumannii strains.

Phenotypic and Molecular Characterization of Hypervirulent and Multidrug-Resistant Acinetobacter baumannii Isolated from ICU Respiratory Infections.

The emergence of hypervirulent strains of Acinetobacter baumannii poses a significant threat in intensive care units (ICU). This study aimed to molecularly characterize hypervirulent A. baumannii strains isolated from ICU patients with respiratory infections. Six strains were isolated from ICU patients over one month. Isolates were identified by phenotypic characterization biochemical properties and 16s RNA sequencing. Antibiotic susceptibility testing was conducted followed by resistance genes detection by PCR. MLST, and PFGE were employed to analyse clonal relationships among strains. Plasmid replicon typing and plasmid transmission frequencies were determined. The isolated strains exhibited diverse clinical manifestations, including acute respiratory distress syndrome (ARDS). Antibiotic susceptibility testing revealed multidrug-resistance phenotype. Molecular analysis revealed a complex genetic landscape of antibiotic resistance genes, including ESBLs and carbapenemases, as well as virulence genes such as ompA, csuE, and exoS. The multiple sequence types indicating genetic diversity among the strains as ST1512, ST622, and ST149 (each type two isolates). Plasmid characterization revealed the presence of diverse replicon types associated with multidrug resistance. This study provides comprehensive insights into the phenotypic, molecular, and epidemiological characteristics of hypervirulent A. baumannii outbark in ICU.

Acinetobacter baumannii Strains Isolated from Various Clinical Samples of Patients Admitted to the Intensive Care Unit and Four-Year Resistance Profiles

Amaç: Yoğun bakım üniteleri Acinetobacter baumannii'nin neden olduğu enfeksiyonlardan en sık etkilenen alanlardır. Hızlı bir şekilde antimikrobiyal direnç geliştirme eğilimi nedeniyle ciddi terapötik sorunlara yol açmaktadır. Bu çalışmanın amacı yoğun bakım ünitelerinden izole edilen Acinetobacter baumannii suşlarının dört yıllık süreçteki antibiyotik duyarlılıklarını belirlemektir. Materyal ve Metod: Ocak 2018–Aralık 2021 yılları arasında yoğun bakım ünitelerinden tıbbi mikrobiyoloji laboratuvarına gönderilen çeşitli örneklerden izole edilen Acinetobacter baumannii suşları çalışmaya dahil edilmiştir. Bakteri tanımlanması ve antibiyotik duyarlılık testleri standart mikrobiyolojik yöntemler ve otomatize sistemler kullanılarak yapılmıştır. Antibiyotik direncinde 2018 ile 2021 yılı verileri Ki-Kare ve Fisher Exact test ile karşılaştırılmış ve p<0.05 anlamlı olarak kabul edilmiştir. Bulgular: Toplam 1900 Acinetobacter baumannii suşu çalışmaya dahil edilmiştir. Bu suşlar en sık trakeal aspirat kültür örneklerinden (1011; %53) izole edilmiştir. Yoğun bakım arasında da en sık Anesteziyoloji ve Reanimasyon yoğun bakım ünitesinden (697; %37) izole edildiği saptanmıştır. 2018 yılı ile 2021 yılı karşılaştırıldığında Acinetobacter baumannii’de antibiyotiklere karşı direnç oranının arttığı görülmüştür. İstatistiksel olarak en anlamlı direnç artışı amikasin, trimetoprim/ sulfametoksazol ve levofloksasinde saptanmıştır (p<0.001). Sonuç: Çalışmamızda Acinetobacter baumannii suşlarında antibiyotiklere direncin yüksek olduğu görülmektedir. Antibiyotik duyarlılık sonuçlarının düzenli olarak takip edilmesi ve raporlanması, hekimlerin antibiyotik kullanım politikalarını belirlemelerine ve enfeksiyon kontrol önlemleri almalarına olanak tanıyacaktır.

Carbapenemase genes distribution in clonal lineages of Acinetobacter baumannii: a comprehensive study on plasmids and chromosomes.

The global spread of plasmids carrying carbapenemase genes within carbapenem resistant Acinetobacter baumannii (CRAB) strains poses a worldwide public health issue. In this study, we conducted a comprehensive genetic analysis of plasmids and chromosomes harboring the major carbapenemase genes (bla NDM, bla KPC, bla VIM, bla IMP, bla GES, bla OXA-58-like, bla OXA-24/40-like, bla OXA-143-like, and bla OXA-23-like) in CRAB strains using bioinformatic tools. We retrieved plasmids and chromosomes carrying the major carbapenemase genes from GenBank. The size, replicon type, and conjugal apparatus of the plasmids were also determined. Furthermore, allele types, co-existence of other antimicrobial resistance genes alongside carbapenemases in plasmids or chromosomes, co-occurrence of carbapenemase genes, gene repetition, and sequence types (ST) of whole genomes were characterized. The database contained 113 plasmids and 38 chromosomes harboring carbapenemase genes. This investigation revealed that bla NDM and bla OXA-58-like were the predominant allele types in both the plasmids and chromosomes. Nine (7.96%) plasmids with bla NDM-1 were potentially conjugative. The most common replicon types of the plasmids were R3-T1, R3-T8, R3-T2, R3-T23, and RP-T1. The analysis revealed that bla NDM-1 and bla OXA-58-like genes possessed the highest variety of co-existence with other antibiotic resistance genes. The co-occurrence of dual carbapenemases was identified in 12 plasmids and 19 chromosomes. Carbapenemase gene repetitions were identified in 10 plasmids and one chromosome. Circular alignment revealed that the plasmids carrying the co-occurrence of bla NDM-1 and bla OXA-58 were more homogeneous. However, there was heterogeneity in certain regions of these plasmids. According to the minimum spanning tree (MST) results, the majority of the plasmids belonged to the genomes of ST2Pas, ST1Pas, ST422Pas, ST622Pas, and ST85Pas. A. baumannii appears to have a strong ability for genome plasticity to incorporate carbapenemase genes on its plasmids and chromosomes to develop resistance against carbapenems. Mobilizable plasmids harboring carbapenemases significantly contribute to the dissemination of these genes. The genetic structure of the plasmids revealed a strong associations of class I integrons, ISAba-like structures, Tn4401 elements, and aac (6')-Ib with carbapenemases. Furthermore, gene repetition may also be associated with carbapenem heteroresistance.