Acinetobacter Baumannii Strains Research Articles

The antibacterial capabilities of alginate encapsulated lemon essential oil nanocapsules against multi-drug-resistant Acinetobacter baumannii

Controlling microbial pollutants is a significant public health concern as they cause several chronic microbial infections and illnesses. In recent years, essential oils (EOs) have become intriguing alternatives for synthetic antimicrobials due to their biodegradability, natural source extraction, and strong antibacterial properties. The bactericidal properties of alginate containing lemon essential oil were examined in this investigation. Following the screening of the MDR strains, the morphological properties of the produced nanoparticles were examined using SEM, DLS, and FTIR. Additionally, the durability, effectiveness, and drug dispersion of encapsulation were assessed. Bacterial virulence factor gene amounts were measured using Q-real-time PCR. Concurrently, the cytotoxic effect of the nanomaterials was evaluated using MTT techniques. Nanoparticles of lemon essential oil encapsulated in alginate, measuring 500 ± 19.32 nm in size, with entrapment efficiency of 77.73 ± 1.78% and were stable for 60 days at 4 °C. Alginate encapsulated with lemon essential oil nanoparticles (ALN) exhibited potent antibacterial qualities, according to the biological investigation. Their ability to decrease the transcription of bacterial virulence genes at least statistically significantly (P ≤ 0.05) served as evidence for this. Between 1.56 and 100 µg/mL (P ≤ 0.01), ALN exhibited lower cytotoxicity against CCD841CoN than free lemon essential oil. The findings show that ALN nanoparticles have the potential to be a breakthrough in the fight against highly resistant illnesses. ALN nanoparticles’ potent antibacterial efficacy against MDR strains of Acinetobacter baumannii may inspire new directions in antibacterial research.

Relationship of biofilm formation with antibiotic resistance, virulence determinants and genetic diversity in clinically isolated Acinetobacter baumannii strains in Karachi, Pakistan.

Multi-drug resistant (MDR) Acinetobacter baumannii causes nosocomial infections due to a plethora of virulence determinants like biofilm formation which are pivotal to its survival and pathogenicity. Hence, investigation of these mechanisms in currently circulating strains is required for effective infection control and drug development. This study investigates the prevalence of antibiotic resistance and virulence factors and their relationship with biofilm formation in Acinetobacter baumannii strains in Karachi, Pakistan. Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC PCR) was used for observing genetic variations. The results revealed that 100% A. baumannii strains were MDR and 74.4% had multiple antibiotic resistance index (MARi) of 0.875-1. There were 27 biofilm forming strains with a moderate correlation between biofilm formation and MARi. A high prevalence of abaI (86.04%), bfmR (95.3%), bfmS (97.6%), csuE (90.69%), ompA (74.4%), and pgaA virulence genes (95.3%) and resistance genes adeF (53.4%), adeJ (74.4%), ampC (51.1%), tem-1 (51.1%), and vim (65.1%)) were observed in these strains. ERIC PCR revealed that 5 of 22 genetic types had strong biofilm form strains with similar virulence genes profiles. Conclusively, the study shows escalated resistance and virulence in clinical strains which warrants consistent epidemiological studies to prevent infections spread and future outbreaks.

Genomic insights into multidrug-resistant Acinetobacter baumannii strains isolated from Dhaka, Bangladesh

Genomic insights into multidrug-resistant Acinetobacter baumannii strains isolated from Dhaka, Bangladesh

Genomic analysis of early ST32 Acinetobacter baumannii strains recovered in US military treatment facilities reveals distinct lineages and links to the origins of the Tn6168 ampC transposon.

To study the population structure and genomic characteristics, including antimicrobial resistance genes, plasmid types and surface polysaccharide type, of the globally distributed Acinetobacter baumannii belonging to ST32 (Institut Pasteur scheme). Antibiotic resistance phenotype for 19 antibiotics was determined using Vitek 2. Whole-genome sequencing was performed using the Illumina MiSeq platform. Genomes were assembled using Newbler. Phylogenetic analysis was done by determining the core-genome alignments using Panaroo v1.3, analysed in IQ-Tree2 v2.2.0.3 to construct Maximum Likelihood trees using the RaxML software. Resistance genes and IS were identified using the Abricate programme, and ISFinder databases. One hundred and thirty-three (n = 133) ST32 A. baumannii isolates were analysed in this study. These genomes originated mainly from US military treatment facilities (n = 113), but also included additional publicly available genomes in GenBank (n = 20) recovered from a broad geographic distribution extending to Asia and South America. Phylogenetic analysis of all 133 genomes revealed at least four clades, with over 80 genomes forming a tightly clustered branch, suggesting they are likely to represent outbreak strains. Analysis of the ampC region showed that ST32 strains played a significant role in the formation of the widely distributed ampC transposon, Tn6168, and supplying DNA segments containing an ISAba1-ampC from ST32s via homologous recombination. ST32 strains played a significant role in the evolution of antibiotic resistance in several widely distributed sequence types including ST1 (global clone 1) and ST3.

Prevalence of Mobile Colistin Resistance (<i>mcr</i>) Genes in <i>Acinetobacter baumannii</i>: Isolates of Clinical Infection from an Iranian University Hospital

Background: The emergence of colistin resistance is a global issue that threatens the effectiveness of colistin treatment against multidrug-resistant Gram-negative bacteria. Objectives: The present study reports on the prevalence of colistin resistance and mcr-encoding genes in Acinetobacter baumannii strains isolated from patients referred to Shahid Rahimi Hospital, Khorramabad, Iran, from January to August 2019. Methods: A total of 47 non-duplicate A. baumannii isolates were obtained from clinical specimens of patients. Colistin susceptibility of the isolates was assessed using the broth microdilution method, and the presence of mcr-encoding genes was determined through the use of PCR. Results: Out of the total 47 isolates belonging to A. baumannii, 14 isolates (29.8%) were resistant to colistin. The minimum inhibitory concentration (MIC) of colistin ranged from 2 to 256 μg/mL, and the MIC50 and MIC90 values for colistin were 0.25 μg/mL and 16 μg/mL, respectively. The presence of mcr-1 and mcr-2 was detected in 6 (12.7%) and 2 (4%) isolates, respectively. However, no isolates harbored the mcr-3 gene. Except for one isolate, none of the mcr-positive isolates exhibited phenotypic resistance to colistin. Conclusions: The higher phenotypic prevalence of colistin resistance compared to genotypic characterization, along with the discrepancy with the presence of mcr genes, suggests the need to monitor and consider all molecular mechanisms of colistin resistance as a last-resort treatment option.

Isolation, characterization, and potential application of Acinetobacter baumannii phages against extensively drug-resistant strains.

One of the significant issues in treating bacterial infections is the increasing prevalence of extensively drug-resistant (XDR) strains of Acinetobacter baumannii. In the face of limited or no viable treatment options for extensively drug-resistant (XDR) bacteria, there is a renewed interest in utilizing bacteriophages as a treatment option. Three Acinetobacter phages (vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln) were identified from hospital sewage and analyzed for their morphology, host ranges, and their genome sequences were determined and annotated. These phages and vB_AbaS_SA1 were combined to form a phage cocktail. The antibacterial effects of this cocktail and its combinations with selected antimicrobial agents were evaluated against the XDR A. baumannii strains. The phages exhibited siphovirus morphology. Out of a total of 30 XDR A. baumannii isolates, 33% were sensitive to vB_AbaS_Ftm, 30% to vB_AbaS_Gln, and 16.66% to vB_AbaS_Eva. When these phages were combined with antibiotics, they demonstrated a synergistic effect. The genome sizes of vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln were 48487, 50174, and 50043 base pairs (bp), respectively, and showed high similarity. Phage cocktail, when combined with antibiotics, showed synergistic effects on extensively drug-resistant (XDR) strains of A. baumannii. However, the need for further study to fully understand the mechanisms of action and potential limitations of using these phages is highlighted.

Antimicrobial Effect of Drinkable Lugol Solution

The death rates due to infection in patients receiving long-term antibiotic treatment and hospitalized patients are quite alarming. Treatment of multidrug-resistant strains of Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, which cause widespread nosocomial infection, has become a global problem. Alternative treatment methods are needed for these species, which use all their resistance mechanisms day by day. Recently, it has been seen that iodine (lugol) solution has been used in the treatment of many infections. Significant results are observed, especially for nosocomial and wound infections. The literature on the antimicrobial effect of Lugol solution is very limited. In order to scientifically support such treatments, we aimed to investigate the antimicrobial effect of lugol on resistant bacteria in a laboratory environment. In our laboratory, we have previously isolated Acinetobacter baumannii, Shigella sonneii, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus strains with known antibiotic resistance. For these isolates, the agar dilution method prepared with different concentrations of lugol and the Broth Microdilution Method were used. As a result of our study, it was observed that drinkable Lugol solution affects multidrug-resistant microorganisms at very low concentrations. Thus, Lugol's success in infection treatments will be scientifically supported.

Molecular Detection of Carbapenemases in Acinetobacter baumannii Strains of Portugal and Association With Sequence Types, Capsular Types, and Virulence

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important nosocomial pathogen. The capsular type (K-type) is considered a major virulence factor, contributing to the evasion of host defenses. The global spread and dissemination dynamics between K-types, sequence types (ST), antibiotic resistance genes, and virulence factors remain largely unknown in Portugal. A collection of 96 CRAB clinical samples collected between 2005 and 2019 in the northern region of Portugal were tested for antimicrobial susceptibility profile and screened by polymerase chain reaction for resistance genetic determinants. A subset of 26 representative isolates was subjected to whole-genome sequencing to assess K types, ST types, and genomic relatedness. The pathogenicity of distinct K-types was also tested using Galleria mellonella model. For the 96 CRAB isolates analyzed, high antimicrobial resistance (>90%) was observed to the carbapenems, fluoroquinolones, and miscellaneous agents. Greater antimicrobial susceptibility (∼30%-57%) was observed for aminoglycosides, particularly tobramycin, and amikacin. Genotypically, 75 strains (78.5%) carried blaOXA-23-like, 18 strains (18.8%) carried blaIMP-like, and 11 strains (14.9%) carried blaOXA-40-like carbapenem resistance genes, respectively. Associations between OXA and ST/capsular locus (KL) types were observed over the years (eg, OXA-40-like/ST46Past/KL120 and OXA-23-like/ST2Past/KL2). ST2Past of clonal complex II was present in most strains, a dominant drug-resistant lineage in the United States and Europe. KL7 was also the most prevalent KL-type (38.5%), followed by KL2 (34.6%), KL120 (23.1%), and KL9 (3.8%). Virulence assessment for different K-types in a Galleria mellonella model revealed a significantly increased virulence for KL120 when compared with KL7, KL9, and KL2. There are specific CRAB serotypes circulating in Portugal, accounting by the low diversity of acquired carbapenemase genes (OXA-23-like and OXA-40-like), ST types (ST2 and ST46) and KL types (KL2, KL7, KL9, and KL120) identified. The high prevalent of ST2, especially when associated with KL2 and blaOXA-23-like, suggest that antibiotic resistance has been driven by clonal expansion of clonal complex II. Such findings provide useful information on the diversity of multidrug-resistant bacterium that might be relevant for antibacterial interventions.

Frequency of pili-based biofilm encoding csu gene among the multi-drug-resistant strains of Acinetobacter baumannii

Frequency of pili-based biofilm encoding csu gene among the multi-drug-resistant strains of Acinetobacter baumannii

Incidence of colistin heteroresistance among carbapenem-resistant Acinetobacter baumannii clinical isolates in a tertiary care hospital in Pakistan.

The emergence of colistin-resistant and heteroresistant strains of carbapenem-resistant Acinetobacter baumannii (CRAB) complicates treatment and exacerbates the global health crisis of drug-resistant bacteria. This study aims to investigate the incidence and clinical implications of colistin heteroresistance in carbapenem-resistant Acinetobacter baumannii isolates from a tertiary hospital in Pakistan. A total of 130 CRAB isolates were collected from December 2022 to December 2023. Colistin susceptibility was assessed using broth microdilution, and heteroresistance was detected through population analysis profiling. Heteroresistance (HR) was identified in 31.5% (41/130) of the isolates, while 7.7% were colistin-resistant, despite initial susceptibility indicated by broth microdilution. Clinical data revealed that HR was associated with significant 14-day clinical failure but not with 30-day all-cause mortality. Heteroresistant strains showed extensive multidrug resistance, posing a serious threat to effective treatment. The study highlights the critical need for accurate detection of colistin HR to prevent treatment failure and improve patient outcomes. The prevalence of colistin HR underscores the necessity for revised diagnostic and treatment strategies in Pakistan, emphasizing the importance of recognizing and addressing this emerging threat in healthcare settings.

Comparative genomic and phenotypic analysis of low- and high-virulent Acinetobacter baumannii strains: Insights into antimicrobial resistance and virulence potential

Multi-drug resistant Acinetobacter baumannii poses a significant threat to public health. This study investigated the genomic features and phenotypic characteristics of two clinical A. baumannii strains, KBN10P01317 (low-virulent) and KBN10P01599 (high-virulent), which share the same sequence type and antimicrobial susceptibility profile. The phenotypic characteristics of A. baumannii strains were assessed by antimicrobial susceptibility testing and virulence trait examination in vitro and in vivo. Whole-genome sequencing was conducted for comparative genomic analysis, and the expression of virulence-associated genes was analyzed using quantitative polymerase chain reaction. Our comparative genomic analysis revealed that KBN10P01599 harbored a larger genome with a greater number of antimicrobial resistance genes, including two copies of the critical resistance gene blaOXA-23, which might contribute to its higher minimum inhibitory concentration for carbapenems (64 μg/ml) compared to KBN10P01317 (32 μg/ml). Although both A. baumannii strains possessed the same repertoire of virulence-associated genes, KBN10P01599 exhibited significantly enhanced expression of quorum sensing (abaI/R) and biofilm formation genes (csuCDE, bap, and pgaA), correlating with its virulence traits, including increased surface motility, biofilm formation, and adherence to host cells. The differences in the expression of virulence-associated genes between the two strains were partly attributed to the transposition of insertion sequence elements. These findings provide valuable insights into the genetic basis of the virulence potential and antimicrobial resistance in A. baumannii, highlighting the evolutionary changes that may occur within strains of the same clone.

Unveiling the interaction, cytotoxicity and antibacterial potential of pyridine derivatives: an experimental and theoretical approach with bovine serum albumin.

The binding interactions between bovine serum albumin (BSA) and three pyridine derivatives, i.e., 2-(5-bromopyridin-3-yl) acetic acid (L1), 3-bromo-5-nitropyridine (L2) and 2-chloro-4-nitropyridine (L3), have been carried out using UV-Vis and fluorescence spectroscopic methods. Fluorescence intensity quenching is observed by adding L2 and L3 to the BSA solution. The quenched fluorescence emission is due to the static nature. An isothermal titration calorimetry (ITC) experiment shows the binding ability of L1 with BSA. The binding constants are found to be 7.23 ± 0.32 × 105 M-1 for L1. The thermodynamic parameters were calculated from ITC measurements (i.e., ∆H = -2.78 ± 0.08 kcal/mol, ∆G = -5.65 ± 0.25 kcal/mol, and -T∆S = -2.87 ± 0.11 kcal/mol), which indicated that the protein-ligand complex formation between L1 and BSA is mainly due to the hydrogen bonds and van der Waals interactions. Cyclic voltammetry (CV) and structure activity and relationship (SAR) studies have been carried out to establish the relationship between ligands and proteins. Additionally, we conducted an antibacterial assay with gram-positive Staphylococcus aureus, Enterococcus faecalis, and negative bacterial strains Acinetobacter baumannii and Escherichia coli against L1, L2, and L3, aiming to address the challenges posed by the co-existence of multidrug-resistant bacteria. Finally, drosophila is used to test the cytotoxicity of ligands L1, L2, and L3's in vitro.

Computational prediction of a phage cocktail active against multidrug-resistant bacteria

Background Antibiotic misuse and overuse have contributed to the emergence of multi-drug resistant (MDR) bacteria, posing a serious public health problem across the globe. Phage cocktails, which combine multiple phages, provide an efficient method to combat multidrug-resistant bacterial infections. This study integrated a computational pipeline to design a phage cocktail against the bacterial strains Acinetobacter baumannii AB0057, Klebsiella pneumoniae subsp. pneumoniae HS11286, and Pseudomonas aeruginosa UCBPP-PA14. Methods The whole genome sequences of selected multidrug-resistant bacteria were accessed. Prophage sequences were identified from them which could be expressed to produce viable lytic phages against MDR bacterial strains, thereby reducing the severity of infection. Prophages were annotated for open reading frames (ORFs), putative promoters, virulence factors, transcriptional terminators, ribosomal RNAs, and transfer RNAs. A dot plot was also generated to investigate similar phages and phylogenetic analysis was performed. Results A total of 11 prophages were predicted from the bacterial genomes. About 472 open reading frames were predicted along with 3 transfer RNAs. Additionally, the presence of 754 putative promoters and 281 transcription terminator sequences was also detected. Comparative genomic and phylogenetic analyses provided insight into the diversity, relatedness, and lytic potential of the phages. The final designed phage cocktail consisted of five selected prophages including Acinetobacter baumannii prophages (2759376-2809756) and (3311844-3364667), and Klebsiella pneumoniae prophages (1288317-1338719), (1778306-1808606), and (2280703-2325555). Conclusion The phage cocktail designed in this study might be useful against MDR Acinetobacter baumannii and Klebsiella pneumoniae infections, especially where conventional antibiotics fail. Sequence similarity analysis suggested that the phage cocktail may also be effective against other carbapenemase-producing K. pneumoniae strains.

Synergistic effects of bacteriophage cocktail and antibiotics combinations against extensively drug-resistant Acinetobacter baumannii

BackgroundThe extensively drug-resistant (XDR) strains of Acinetobacter baumannii have become a major cause of nosocomial infections, increasing morbidity and mortality worldwide. Many different treatments, including phage therapy, are attractive ways to overcome the challenges of antibiotic resistance.MethodsThis study investigates the biofilm formation ability of 30 XDR A. baumannii isolates and the efficacy of a cocktail of four tempetate bacteriophages (SA1, Eve, Ftm, and Gln) and different antibiotics (ampicillin/sulbactam, meropenem, and colistin) in inhibiting and degrading the biofilms of these strains.ResultsThe majority (83.3%) of the strains exhibited strong biofilm formation. The bacteriophage cocktail showed varying degrees of effectiveness against A. baumannii biofilms, with higher concentrations generally leading to more significant inhibition and degradation rates. The antibiotics-bacteriophage cocktail combinations also enhanced the inhibition and degradation of biofilms.ConclusionThe findings suggested that the bacteriophage cocktail is an effective tool in combating A. baumannii biofilms, with its efficacy depending on the concentration. Combining antibiotics with the bacteriophage cocktail improved the inhibition and removal of biofilms, indicating a promising strategy for managing A. baumannii infections. These results contribute to our understanding of biofilm dynamics and the potential of bacteriophage cocktails as a novel therapeutic approach to combat antibiotic-resistant bacteria.

Bactericidal and Synergistic Effects of Lippia origanoides Essential Oil and Its Main Constituents against Multidrug-Resistant Strains of Acinetobacter baumannii.

Bacterial resistance in Acinetobacter baumannii is a significant public health challenge, as these bacteria can evade multiple antibiotics, leading to difficult-to-treat infections with high mortality rates. As part of the search for alternatives, essential oils from medicinal plants have shown promising antibacterial potential due to their diverse chemical constituents. This study evaluated the antibacterial, antibiofilm, and synergistic activities of the essential oil of Lippia origanoides (EOLo) and its main constituents against multidrug-resistant clinical isolates of A. baumannii. Additionally, the antibacterial and antibiofilm potential of a nanoemulsion containing carvacrol (NE-CAR) was assessed. EOLo was extracted through hydrodistillation, and its components were identified via gas chromatography coupled with mass spectrometry. The A. baumannii isolates (n = 9) were identified and tested for antimicrobial susceptibility using standard disk diffusion methods. Antibacterial activity was determined by broth microdilution, while antibiofilm activity was measured using colorimetric methods with crystal violet and scanning electron microscopy. Synergism tests with antibiotics (meropenem, ciprofloxacin, gentamicin, and ampicillin+sulbactam) were performed using the checkerboard method. The primary constituents of EOLo included carvacrol (48.44%), p-cymene (14.58%), and thymol (10.16%). EOLo, carvacrol, and thymol demonstrated significant antibacterial activity, with carvacrol showing the strongest effect. They were also effective in reducing biofilm formation, as was NE-CAR. The combinations with antibiotics revealed significant synergistic effects, lowering the minimum inhibitory concentration of the tested antibiotics. Therefore, this study confirms the notable antibacterial activity of the essential oil of L. origanoides and its constituents, especially carvacrol, suggesting its potential as a therapeutic alternative for A. baumannii infections.

Intragenomic conflicts with plasmids and chromosomal mobile genetic elements drive the evolution of natural transformation within species.

Natural transformation is the only mechanism of genetic exchange controlled by the recipient bacteria. We quantified its rates in 786 clinical strains of the human pathogens Legionella pneumophila (Lp) and 496 clinical and environmental strains of Acinetobacter baumannii (Ab). The analysis of transformation rates in the light of phylogeny revealed they evolve by a mixture of frequent small changes and a few large quick jumps across 6 orders of magnitude. In standard conditions close to half of the strains of Lp and a more than a third in Ab are below the detection limit and thus presumably non-transformable. Ab environmental strains tend to have higher transformation rates than the clinical ones. Transitions to non-transformability were frequent and usually recent, suggesting that they are deleterious and subsequently purged by natural selection. Accordingly, we find that transformation decreases genetic linkage in both species, which might accelerate adaptation. Intragenomic conflicts with chromosomal mobile genetic elements (MGEs) and plasmids could explain these transitions and a GWAS confirmed systematic negative associations between transformation and MGEs: plasmids and other conjugative elements in Lp, prophages in Ab, and transposable elements in both. In accordance with the hypothesis of modulation of transformation rates by genetic conflicts, transformable strains have fewer MGEs in both species and some MGEs inactivate genes implicated in the transformation with heterologous DNA (in Ab). Innate defense systems against MGEs are associated with lower transformation rates, especially restriction-modification systems. In contrast, CRISPR-Cas systems are associated with higher transformation rates suggesting that adaptive defense systems may facilitate cell protection from MGEs while preserving genetic exchanges by natural transformation. Ab and Lp have different lifestyles, gene repertoires, and population structure. Nevertheless, they exhibit similar trends in terms of variation of transformation rates and its determinants, suggesting that genetic conflicts could drive the evolution of natural transformation in many bacteria.

Alterations in the Antimicrobial Resistance Profile of Acinetobacter baumannii Strains Isolated from Intensive Care Unit Patients: Five-Year Follow-up in Cappadocia

Background: This study aims to determine alterations in the antibiotic resistance status of Acinetobacter baumannii strains isolated from lower respiratory tract samples of patients in intensive care units over the years. Methods: In this comprehensive study, A. baumannii strains isolated from aspirate and sputum samples of patients hospitalized in intensive care units of a second-stage state hospital between January 2018 and December 2022 were meticulously and retrospectively investigated and analyzed for antimicrobial resistance. Results: The rate of aspirate and sputum samples in the study was 18.1% (754/4151); The positivity rate of cultures was 51.7% (390/754); The rate of those associated with A. baumannii was found to be 65.6% (256/390).. 90.2% of the isolates were isolated from the general intensive care unit (231/256). The rates of A. baumannii isolated from aspirate and sputum samples were 67.4% (213/316) and 58.1% (43/74), respectively. The carbapenem resistance rate in A. baumannii isolates grown in aspirate samples was 96.5%, fluoroquinolone resistance was 91.7%; The carbapenem resistance rate in sputum samples was 96.1% and fluoroquinolone resistance was 90.9%. The most effective antibiotics against A. baumannii strains isolated from both aspirate and sputum samples were colistin 100% (n=256), TMP/SXT 55.8% (143/256), tigecycline 50.3% (129/256), respectively. Conclusion: Our study reveals a concerning trend-a high frequency of multidrug-resistant A. baumannii isolates are being identified in the Central Anatolia region of our country. This high prevalence, which is a cause for immediate concern, underscores the urgent and immediate need for robust infection control measures to curb the spread of A. baumannii in hospitals.

Genotypic Characterisation of Carbapenemases in Clinical Isolates of Acinetobacter baumannii in a Tertiary Care Teaching Hospital of Kerala

Background: The multidrug-resistant and carbapenem-resistant Acinetobacter baumannii strains are an increasing global concern. The primary cause of carbapenem resistance in A. baumannii is production of various beta-lactamases with versatile hydrolytic capacities. The present study investigates the prevalence of different carbapenemases among clinical isolates of carbapenem-resistant A. baumannii from a tertiary care teaching hospital in Kerala, India. Methods: Non-duplicate isolates from sputum, endotracheal aspirate, pus, urine, and blood samples were included in the study. Isolate identification and antibiotic susceptibility testing of the isolates were done using vitek 2 system. A conventional polymerase chain reaction was used to detect the carbapenemase-encoding genes in the isolates. Results: A total of the 126 isolates studied, among these 105 (83.3%) isolates were from intensive care unit patients and 21(16.6%) were from non-ICU inpatients. Most of the isolates were obtained from respiratory specimens-78(61.9%) followed by pus-33(26.2%), urine-12(9.5%) and blood- 3(2.4%). The prevalence of carbapenemase genes were as follows:blaOXA-51(n=126, 100%) blaOXA-23 (n=98, 77.7%), blaOXA-58 (n=7, 5.6%), blaNDM (n=66, 52.4%), blaIMP (n=26, 20.6%), and blaVIM (n=20, 15.9%). Among the total isolates 78 (61.9%) isolates harbored metallo-beta-lactamase genes, 47(37.3%) isolates harboured a single carbapenemase gene, while 69(54.8%) isolates harbored two or more genes. Conclusion: This study reveals a higher prevalence of metallo-beta lactamases and the co-occurrence of multiple carbapenemase genes in Carbapenem resistant A. baumannii isolates.

Could the Adoptive Transfer of Memory Lymphocytes be an Alternative Treatment for Acinetobacter baumannii Infections?

We evaluated the efficacy of the adoptive transfer of memory B, CD4+, and CD8+ T lymphocytes compared with sulbactam and tigecycline in an experimental murine pneumonia model by two multidrug-resistant Acinetobacter baumannii strains, colistin-susceptible AbCS01 and colistin-resistant AbCR17. Pharmacodynamically optimized antimicrobial dosages were administered for 72 h, and intravenous administration of 2 × 106 of each of the memory cells in a single dose 30 min post-infection. Bacterial lung and blood counts and mortality rates were analyzed. Results showed that a single dose of memory B or CD4+ T cells was as effective as sulbactam in terms of bacterial clearance from the lungs and blood compared with the untreated mice or the tigecycline-treated mice inoculated with the AbCS01 strain. In the pneumonia model by AbCR17, a single dose of memory B or CD4+ T cells also reduced the bacterial load in the lungs compared with both antibiotic groups and was more efficacious than tigecycline in terms of blood clearance. Regarding survival, the adoptive transfer of memory B or CD4+ T cells was as effective as three days of sulbactam treatment for both strains. These data suggest that adoptive memory cell transfer could be a new effective treatment of multidrug-resistant A. baumannii infections.

Effect of arsenic green synthesis nanoparticles on multi-drug resistant Acinetobacter baumannii

Multidrug-resistant strains of Acinetobacter baumannii are pathogenic agents of hospital infections, especially in the intensive care unit (ICU). The purpose of this study is to investigate the antibacterial effects and biosynthesis of arsenic nanoparticles (ARn) using pink rose petals on multi-drug resistant strains of A. baumannii. In this study, plant bioactive molecules present in rose petals are responsible for the synthesis of ARn. The characteristics of ARn were determined through FTIR, EDX, DLS, SEM, UV-Vis, and XRD techniques. In addition, the antibacterial activity of biosynthesized ARn was investigated against multi-drug resistant A. baumannii. The results of SEM revealed that the ARn were spherical with an average diameter of 75.71 nm. The results of XRD confirmed the crystal structure of arsenic oxide phase. The results of antibacterial effects exhibited that the lowest MIC of ARn was 800 μg/ml on the standard strain of A. baumannii and 800 μg/ml against clinical strains of multi-drug-resistant A. baumannii. The results of this study provided an new green synthesis method for ARn, which have a high potential on multi-drug-resistant A. baumannii. This study has the potential to pave the way for further research and developments in this field.