Multidrug-resistant Acinetobacter Baumannii Research Articles

Synergistic Antibacterial Activity of Curcuma domestica Val. Extract with Tetracycline Against Multidrug-resistant Acinetobacter baumannii

Infections caused by multidrug-resistant (MDR) bacteria are on the rise globally. MDR is facilitated by overexpression of efflux pump and permeability changes of membrane. Acinetobacter baumannii is a pathogenic germ that causes a major problem in infection, also, there has been an increase in the incidence of resistance to various antibiotics. The present study highlights the synergistic of ethanolic extract of Curcuma domestica (EECD) rhizome with tetracycline against multidrug-resistant A. baumannii (MDR-Ab). Assessment of Minimum Inhibitory Concentration (MIC) was determined by microdilution using 96-well plates. The synergistic effect of EECD and tetracycline was determined by checkerboard method. The effect of EECD and tetracycline combination was investigated by bacteriolytic activity and inhibition of efflux pump by Ethidium Bromide (EtBr) accumulation assay. EECD presented the MIC value 250 µg/mL against MDR-Ab. Fractional Inhibitory Concentration Index (FICI) value of EECD and tetracycline combination was 0.4, which showed their synergistic effect. Additionally, the combination of EECD and tetracycline could inhibit the efflux pump in MDR-Ab. This combination can also compromise cell integrity by altering membrane permeability thus lysing the bacteria cells. According to these results, EECD and tetracycline combination has synergistic effects at some sites of action, and thus could be used as a breakthrough to overcome infection problems due to MDR-Ab.
 
 Keywords: Acinetobacter baumannii, antibacterial, Curcuma domestica, multidrug-resistant, tetracycline

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).

Deciphering the structure of a multi-drug resistant Acinetobacter baumannii short-chain dehydrogenase reductase.

The rapidly increasing threat of multi-drug-resistant Acinetobacter baumannii infections globally, encompassing a range of clinical manifestations from skin and soft tissue infections to life-threatening conditions like meningitis and pneumonia, underscores an urgent need for novel therapeutic strategies. These infections, prevalent in both hospital and community settings, present a formidable challenge to the healthcare system due to the bacterium's widespread nature and dwindling effective treatment options. Against this backdrop, the exploration of bacterial short-chain dehydrogenase reductases (SDRs) emerges as a promising avenue. These enzymes play pivotal roles in various critical bacterial processes, including fatty acid synthesis, homeostasis, metabolism, and contributing to drug resistance mechanisms. In this study, we present the first examination of the X-ray crystallographic structure of an uncharacterized SDR enzyme from A. baumannii. The tertiary structure of this SDR is distinguished by a central parallel β-sheet, consisting of seven strands, which is flanked by eight α-helices. This configuration exhibits structural parallels with other enzymes in the SDR family, underscoring a conserved architectural theme within this enzyme class. Despite the current ambiguity regarding the enzyme's natural substrate, the importance of many SDR enzymes as targets in anti-bacterial agent design is well-established. Therefore, the detailed structural insights provided in this study open new pathways for the in-silico design of therapeutic agents. By offering a structural blueprint, our findings may provide a platform for future research aimed at developing targeted treatments against this and other multi-drug-resistant infections.

Host range expansion of Acinetobacter phage vB_Ab4_Hep4 driven by a spontaneous tail tubular mutation.

Bacteriophages (phages) represent promising alternative treatments against multidrug-resistant Acinetobacter baumannii (MDRAB) infections. The application of phages as antibacterial agents is limited by their generally narrow host ranges, so changing or expanding the host ranges of phages is beneficial for phage therapy. Multiple studies have identified that phage tail fiber protein mediates the recognition and binding to the host as receptor binding protein in phage infection. However, the tail tubular-dependent host specificity of phages has not been studied well. In this study, we isolated and characterized a novel lytic phage, vB_Ab4_Hep4, specifically infecting MDRAB strains. Meanwhile, we identified a spontaneous mutant of the phage, vB_Ab4_Hep4-M, which revealed an expanded host range compared to the wild-type phage. A single mutation of G to C was detected in the gene encoding the phage tail tubular protein B and thus resulted in an aspartate to histidine change. We further demonstrated that the host range expansion of the phage mutant is driven by the spontaneous mutation of guanine to cytosine using expressed tail tubular protein B. Moreover, we established that the bacterial capsule is the receptor for phage Abp4 and Abp4-M by identifying mutant genes in phage-resistant strains. In conclusion, our study provided a detailed description of phage vB_Ab4_Hep4 and revealed the tail tubular-dependent host specificity in A. baumannii phages, which may provide new insights into extending the host ranges of phages by gene-modifying tail tubular proteins.

Comparison of in vitro synergy between polymyxin B or colistin in combination with 16 antimicrobial agents against multidrug-resistant Acinetobacter baumannii isolates

PurposesThis study determined the synergy of polymyxin B (POLB) and colistin (COL) with 16 other tested antimicrobial agents in the inhibition of multidrug-resistant Acinetobacter baumannii (MDR-AB). MethodsWe used chequerboard assays to determine synergy between the drugs against 50 clinical MDR-AB from a tertiary hospital in the Zhejiang province in 2019, classifying combinations as either antagonistic, independent, additive, or synergistic. The efficacy of hit combinations which showed highest synergistic rate were confirmed using time-kill assays. ResultsBoth POLB and COL displayed similar bactericidal effects when used in combination with these 16 tested drugs. Antagonism was only observed for a few strains (2%) exposed to a combination of POLB and cefoperazone/sulbactam (CSL). A higher percentage of synergistic combinations with POLB and COL were observed with rifabutin (RFB; 90%/96%), rifampicin (RIF; 60%/78%) and rifapentine (RFP; 56%/76%). Time-kill assays also confirmed the synergistic effect of POLB and rifamycin class combinations. 1/2 MIC rifamycin exposure can achieve bacterial clearance when combined with 1/2 MIC POLB or COL. ConclusionNearly no antagonism was observed when combining polymyxins with other drugs by both chequerboard and time-kill assays, suggesting that polymyxins may be effective in combination therapy. The combinations of POLB/COL with RFB, RIF, and RFP displayed neat synergy, with RFB showing the greatest effect.

Multi-drug Resistant Acinetobacter baumannii: Phenotypic and Genotypic Resistance Profiles and the Associated Risk Factors in Teaching Hospital in Jordan

BackgroundThis study aimed to determine the prevalence of Antimicrobial Resistance Genes (ARGs), with a focus on colistin resistance in clinical A. baumannii, as well as the risk factors associated with A. baumannii infection in Jordanian patients. MethodsIn total, 150 A. baumannii isolates were obtained from patients at a teaching hospital. The isolates were tested for antimicrobial susceptibility using disc diffusion and microdilution methods. PCR amplification was used to detect ARGs, and statistical analysis was conducted to evaluate the influence of identified risk factors on the ARGs acquisition. ResultsMore than 90% of A. baumannii isolates were resistant to monobactam, carbapenem, cephalosporins, Fluoroquinolones, penicillin, and β-lactam agents. Moreover, 20.6% of the isolates (n = 31) were colistin-resistant. Several ARGs were also detected in A. baumannii isolates. Univariate analysis indicated that risk factors and the carriage of ARGs were significantly associated P ≤ (0.05) with gender, invasive devices, immunodeficiency, systemic diseases, tumors, and covid-19. Logistic regression analysis indicated seven risk factors, and three protective factors were associated with the ARGs (armA, strA, and strB) P ≤ (0.05). In contrast, tetB and TEM were associated with 2 risk factors each P ≤ (0.05). ConclusionOur study indicates a high prevalence of MDR A. baumannii infections in ICU patients, as well as describing the case of colistin-resistant A. baumannii for the first time in Jordan. Additionally, the risk factors associated with ARGs-producing A. baumannii infections among ICU patients suggest a rapid emergence and spread of MDR A. baumannii without adequate surveillance and control measures.

Clinical Efficacy of Sitafloxacin-Colistin-Meropenem and Colistin-Meropenem in Patients with Carbapenem-Resistant and Multidrug-Resistant Acinetobacter baumannii Hospital-Acquired Pneumonia (HAP)/Ventilator-Associated Pneumonia (VAP) in One Super-Tertiary Hospital in Bangkok, Thailand: A Randomized Controlled Trial.

Carbapenem-resistant A. baumannii (CRAB) hospital-acquired pneumonia (HAP)/ventilator-associated pneumonia (VAP) is now a therapeutic problem worldwide. An open-label, randomized, superiority, single-blind trial was conducted in Rajavithi Hospital, a super-tertiary care facility in Bangkok, Thailand. CRAB HAP/VAP patients were randomly assigned to receive either sitafloxacin-colistin-meropenem or colistin-meropenem. Outcomes in the two groups were then assessed with respect to mortality, clinical response, and adverse effects. Between April 2021 and April 2022, 77 patients were treated with combinations of either sitafloxacin plus colistin plus meropenem (n = 40) or colistin plus meropenem (n = 37). There were no significant differences between the two groups with respect to all-cause mortality rates at 7 days and 14 days (respectively, 7.5% vs. 2.7%; p = 0.616, and 10% vs. 10%; p = 1). Patients who received sitafloxacin-colistin-meropenem showed improved clinical response compared with patients who received colistin-meropenem in terms of both intention-to-treat (87.5% vs. 62.2%; p = 0.016) and per-protocol analysis (87.2% vs. 67.7%; p = 0.049). There were no significant differences between the two groups with respect to adverse effects. Adding sitafloxacin as a third agent to meropenem plus colistin could improve clinical outcomes in CRAB HAP/VAP with little or no impact on adverse effects. In short, sitafloxacin-meropenem-colistin could be another therapeutic option for combatting CRAB HAP/VAP.

Risk factors for bacteremia and mortality due to multidrug-resistant Acinetobacter baumannii: a retrospective study.

This research aimed to determine the relationships between the risk factors for nosocomial multidrug-resistant Acinetobacter baumannii (MDRAB) bacteremia and associated mortality. We analyzed 144 patients treated for A. baumannii bacteremia, including 120 patients with MDRAB bacteremia, from March 2015 to March 2020, in this retrospective study. The overall bacteremia-related mortality rate was 48.6%. The mortality rates were 25.0% and 53.3% for non-MDRAB and MDRAB bacteremia, respectively. Risk factors for the development of MDRAB bacteremia were prior use of cephalosporins [odds ratio (OR): 8.62; P<.001], carbapenems (OR: 15.04; P<.001), or quinolones (OR: 5.02; P=.040); indwelling urinary catheters (OR: 21.38; P<.001); and respiratory tract as the source of bacteremia (OR: 75.33; P<.001). Patients with elective surgeries were inclined to develop non-MDRAB bacteremia (OR: 0.45; P=.029). High scores in the Acute Physiology and Chronic Health Evaluation II (OR: 1.321; P<.001) and Sequential Organ Failure Assessment (OR: 1.326; P<.001) were risk factors for mortality from MDRAB infection. In summary, higher mortality rates occur in patients with MDRAB bacteremia, and risk factors include prior use of cephalosporins, carbapenems, or quinolones. Urinary catheters and the respiratory tract as sources of the infection increase the risk of MDRAB bacteremia.

Central Venous Catheters versus Peripherally Inserted Central Catheters: A Comparison of Indwelling Time Resulting in Colonization by Multidrug-Resistant Pathogens.

The use of peripherally inserted central catheters (PICCs) as an alternative to central venous catheters (CVCs) has steadily risen over the last two decades. However, there is an ongoing debate regarding research evidence that supports any clear advantages or disadvantages of them compared to traditional central venous lines. The present study was conducted to compare the indwelling time of CVC and PICC placements leading to microbial colonization by multidrug-resistant microorganisms (MDROs) in critically ill patients. A single-center retrospective descriptive study was performed that reviewed the medical records of critically ill patients with colonized CVCs and PICCs who were hospitalized during a 24-month period (May 2019-May 2021). To evaluate the association between indwelling time of catheter placement and colonization rates, events were categorized into three groups, each representing a one-week time interval of catheter indwelling time: group 1: ≤7 days, group 2: 8-14 days, and group 3: >14 days. A total of 207 hospitalized patients with colonized PICCs or CVCs were included in the study. Of these, 144 (69.5%) had a CVC placement and 63 (30.5%) had a PICC placement. The overall colonization rate (per 1.000 catheter/days) was 14.73 in the CVC and 5.67 in the PICC cohort (p = 0.003). In the group of PICCs, 12/63 (19%) of the pathogens were MDROs and 51/63 (81%) were non-MDROs, while in the group of CVCs, 86/144 (59.7%) were MDROs and 58/144 (40.3%) were non-MDROs (p < 0.001). The colonization rate in the CVC cohort, was 6.98 for group 1, 21.57 for group 2, and 21.6 for group 3 (p = 0.019). The colonization rate of MDROs was 3.27 for group 1, 14.47 for group 2, and 12.96 for group 3 (p = 0.025). Regarding the PICC cohort, the colonization rate was 1.49 for group 1, 3.19 for group 2, and 8.99 for group 3 (p = 0.047). No significant difference existed between the three groups in terms of MDRO pathogens, with the colonization rate being 0 for group 1, 0.8 for group 2, and 1.69 for group 3 (p = 0.78). Within the CVC cohort, the most common isolated microorganism was MDR Acinetobacter baumannii (n = 44; 30.6%), followed by MDR Klebsiella pneumoniae (n = 27; 18.7%). In the PICC cohort, the predominant isolated microorganism was Candida non-albicans (n = 15; 23.8%), followed by Candida albicans, coagulase-negative staphylococci, and MDR Klebsiella pneumoniae in equal numbers (n = 6; 9.5%). Our findings show that while the indwelling time of PICC placement was longer compared to CVCs, its colonization rate was considerably lower. Furthermore, high colonization rates by microorganisms, especially MDROs, arose later during catheterization in PICCs compared to CVCs, suggesting that in terms of vascular infections, PICCs may be a safer alternative to conventional CVCs for long-term intravenous access.

An outbreak of multi-drug-resistant Acinetobacter baumannii on a burns ICU and its control with multi-faceted containment measures

BackgroundPatients in burn centres are at high risk of acquiring multidrug-resistant pathogens due to reduced skin barrier and long hospital stay. MethodsWe report the investigation and control of an outbreak due to multidrug-resistant Acinetobacter baumannii in a burn centre. The 27 patients hospitalized in the centre during the outbreak were regularly screened and a total of 132 environmental samples were performed to identify a potential source. Fourier-transform infrared (FT-IR) spectroscopy and multilocus sequence typing (MLST) were applied to characterise the outbreak strain. ResultsBetween August and November 2022, the outbreak affected eight patients with eleven infections and three potentially related fatal outcomes. An interdisciplinary and multiprofessional outbreak team implemented a bundle strategy with repetitive admission stops, isolation precaution measures, patient screenings, enhanced cleaning and disinfection, and staff education. FT-IR spectroscopy suggested that the outbreak started from an index patient, who was repatriated one month before from a country with high prevalence of MDR A. baumannii. Environmental sampling did not identify a common source. Acquisition of the outbreak strain was associated with larger burn lesions ≥ 2a (per percent increase odds ratio (OR) 1.05 (0.99-1.12), P=0.09), and inversely associated with a higher nurse-to-patient ratio (per 0.1 increase OR 0.34, 95%CI 0.10-1.12, P=0.06). ConclusionsBurn patients with a large area of affected body surface, are at high risk for colonization and infection due to MDRO, particularly during periods of high workload. A multifaceted containment strategy can successfully control outbreaks due to MDR A. baumannii in a burn centre.

Plasmid content of carbapenem resistant Acinetobacter baumannii isolates belonging to five International Clones collected from hospitals of Alexandria, Egypt.

Multidrug resistant Acinetobacter baumannii is one of the most important nosocomial pathogens worldwide. During the last decades it has become a major threat for healthcare settings due to the high antibiotic resistance rates among these isolates. Many resistance determinants are coded by conjugative or mobilizable plasmids, facilitating their dissemination. The majority of plasmids harbored by Acinetobacter species are less than 20 Kb, however, high molecular weight elements are the most clinically relevant since they usually contain antibiotic resistance genes. The aim of this work was to describe, classify and determine the genetic content of plasmids harbored by carbapem resistant A. baumannii isolates belonging to predominant clonal lineages circulating in hospitals from Alexandria, Egypt. The isolates were subjected to S1-Pulsed Field Gel Electrophoresis experiments to identify high molecular weight plasmids. To further analyze the plasmid content and the genetic localization of the antibiotic resistance genes, isolates were sequenced by Illumina Miseq and MinION Mk1C and a hybrid assembly was performed using Unicycler v0.5.0. Plasmids were detected with MOBsuite 3.0.3 and Copla.py v.1.0 and mapped using the online software Proksee.ca. Replicase genes were further analyzed through a BLAST against the Acinetobacter Plasmid Typing database. Eleven plasmids ranging in size from 4.9 to 205.6 Kb were characterized and mapped. All isolates contained plasmids, and, in many cases, more than two elements were identified. Antimicrobial resistance genes such as bla OXA-23, bla GES-like, aph(3')-VI and qacEΔ1 were found in likely conjugative large plasmids; while virulence determinants such as septicolysin or TonB-dependent receptors were identified in plasmids of small size. Some of these resistance determinants were, in turn, located within transposons and class 1 integrons. Among the identified plasmids, the majority encoded proteins belonging to the Rep_3 family, but replicases of the RepPriCT_1 (Aci6) family were also identified. Plasmids are of high interest as antibiotic resistance control tools, since they may be used as genetic markers for antibiotic resistance and virulence, and also as targets for the development of compounds that can inhibit transfer processes.

Independent component analysis reveals 49 independently modulated gene sets within the global transcriptional regulatory architecture of multidrug-resistant Acinetobacter baumannii.

Acinetobacter baumannii causes severe infections in humans, resists multiple antibiotics, and survives in stressful environmental conditions due to modulations of its complex transcriptional regulatory network (TRN). Unfortunately, our global understanding of the TRN in this emerging opportunistic pathogen is limited. Here, we apply independent component analysis, an unsupervised machine learning method, to a compendium of 139 RNA-seq data sets of three multidrug-resistant A. baumannii international clonal complex I strains (AB5075, AYE, and AB0057). This analysis allows us to define 49 independently modulated gene sets, which we call iModulons. Analysis of the identified A. baumannii iModulons reveals validating parallels to previously defined biological operons/regulons and provides a framework for defining unknown regulons. By utilizing the iModulons, we uncover potential mechanisms for a RpoS-independent general stress response, define global stress-virulence trade-offs, and identify conditions that may induce plasmid-borne multidrug resistance. The iModulons provide a model of the TRN that emphasizes the importance of transcriptional regulation of virulence phenotypes in A. baumannii. Furthermore, they suggest the possibility of future interventions to guide gene expression toward diminished pathogenic potential.IMPORTANCEThe rise in hospital outbreaks of multidrug-resistant Acinetobacter baumannii infections underscores the urgent need for alternatives to traditional broad-spectrum antibiotic therapies. The success of A. baumannii as a significant nosocomial pathogen is largely attributed to its ability to resist antibiotics and survive environmental stressors. However, there is limited literature available on the global, complex regulatory circuitry that shapes these phenotypes. Computational tools that can assist in the elucidation of A. baumannii's transcriptional regulatory network architecture can provide much-needed context for a comprehensive understanding of pathogenesis and virulence, as well as for the development of targeted therapies that modulate these pathways.

Polymyxin B-targeted liposomal photosensitizer cures MDR A. baumannii burn infections and accelerates wound healing via M1/M2 macrophage polarization

Multidrug-resistant (MDR) Acinetobacter baumannii infections pose a significant challenge in burn wound management, necessitating the development of innovative therapeutic strategies. In this work, we introduced a novel polymyxin B (PMB)-targeted liposomal photosensitizer, HMME@Lipo-PMB, for precise and potent antimicrobial photodynamic therapy (aPDT) against burn infections induced by MDR A. baumanni. HMME@Lipo-PMB-mediated aPDT exhibited enhanced antibacterial efficacy by specifically targeting and disrupting bacterial cell membranes, and generating increased intracellular ROS. Remarkably, even at low concentrations, this targeted approach significantly reduced bacterial viability in vitro and completely eradicated burn infections induced by MDR A. baumannii in vivo. Additionally, HMME@Lipo-PMB-mediated aPDT facilitated burn infection wound healing by modulating M1/M2 macrophage polarization. It also effectively promoted acute inflammation in the early stage, while attenuated chronic inflammation in the later stage of wound healing. This dynamic modulation promoted the formation of granulation tissue, angiogenesis, and collagen regeneration. These findings demonstrate the tremendous potential of HMME@Lipo-PMB-mediated aPDT as a promising alternative for the treatment of burn infections caused by MDR A. baumannii.

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.

Characterization of a novel bacteriophage endolysin (LysAB1245) with extended lytic activity against distinct capsular types associated with Acinetobacter baumannii resistance.

Capsular polysaccharides are considered as major virulence factors associated with the ability of multidrug-resistant (MDR) Acinetobacter baumannii to cause severe infections. In this study, LysAB1245, a novel bacteriophage-encoded endolysin consisting of a lysozyme-like domain from phage T1245 was successfully expressed, purified, and evaluated for its antibacterial activity against distinct capsular types associated with A. baumannii resistance. The results revealed a broad spectrum activity of LysAB1245 against all clinical MDR A. baumannii isolates belonging to capsular type (KL) 2, 3, 6, 10, 47, 49, and 52 and A. baumannii ATCC 19606. At 2 h following the treatment with 1.7 unit/reaction of LysAB1245, more than 3 log reduction in the numbers of bacterial survival was observed. In addition, LysAB1245 displayed rapid bactericidal activity within 30 min (nearly 3 log CFU/mL of bacterial reduction). Thermostability assay indicated that LysAB1245 was stable over a broad range of temperature from 4 to 70°C, while pH sensitivity assay demonstrated a wide range of pH from 4.5 to 10.5. Furthermore, both minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of LysAB1245 against all MDR A. baumannii isolates and A. baumannii ATCC 19606 were 4.21 μg/mL (0.1 unit/reaction). Conclusively, these results suggest that LysAB1245 possesses potential application for the treatment of nosocomial MDR A. baumannii infections.

Pneumonija prouzrokovana Acinetobacter baumanii tokom mehaničke ventilacije usled infekcije kovidom 19 - epidemiološke i kliničke karakteristike i terapija

Less than 3% of people who get infected with COVID-19 need hospital treatment. However, up to one-third of the hospitalized patients with COVID-19 require invasive mechanical ventilation. Ventilator-associated pneumonia (VAP), caused by the multidrug-resistant Acinetobacter baumannii (A. baumannii), is an emerging infection in the intensive care units and can have fatal consequences for those patients who already have critical COVID-19. Countries of the Balkan peninsula have an exceptionally high prevalence of invasive carbapenem-resistant Acinetobacter spp in the hospital setting. Diagnosing this type of pneumonia is a challenging process. Furthermore, treatment complexities arise because of multidrug resistance. Novel therapeutic agents, such as sulbactam/durlobactam and zosurabalpin could be the new therapeutic opportunity for A. baumannii-induced VAP. Antimicrobial resistance of A. baumannii is not entirely understood, although several mechanisms have been identified. To adequately manage VAP it is important to isolate causative agents, have awareness of the resistance pattern, carefully dispense antibiotics, and identify risk factors. In this review, we discuss epidemiological characteristics, pathophysiological mechanisms, clinical presentation and diagnosis, as well as the current and novel treatments of A. baumannii-induced VAP.

The Effect of Citric and Ascorbic Acids as Anti-Biofilm and Anti-Capsular Agents on Multidrug-Resistant Acinetobacter baumannii

Objective: Acinetobacter baumannii (A. baumannii) is an opportunistic bacterium with multiple virulence factors, including capsule and biofilm, and is known for its high drug resistance. Anti-virulence natural substances have been suggested as novel alternatives to conventional antibiotics. We aimed to evaluate the effect of citric and ascorbic acids as anti-biofilm and anti-capsular agents against multidrug-resistant (MDR) A. baumannii clinical isolates. Materials and Methods: Twenty-eight A. baumannii MDR isolates were collected from different clinical sources. The minimum inhibitory concentration (MIC) of each agent was estimated. Biofilm formation and capsule were investigated phenotypically in the absence and presence of both agents at ½ and ¼ MICs. The presence of 14 adhesive and nonadhesive virulence genes was investigated. Results: Phenotypically, all the isolates were biofilm producers and were capsulated. The MIC of citric acid ranged from 1.25 to 2.5 mg/mL, while that of ascorbic acid was 3 mg/mL for all isolates. Both agents showed significant reduction in biofilm and capsular thinning. Ascorbic acid showed a dose-dependent effect in both biofilm reduction and capsule thinning unlike citric acid. Four genes, papG23, sfa1, fyuA, and cvaC, were absent among all isolates, while iutA was present in 100% of isolates. Other genes showed different distributions among the isolates. These virulence genes were not correlated to the anti-biofilm effect of both agents. Ascorbic acid was observed to have a better effect than citric acid. This can provide a clue for a better treatment regimen including ascorbic acid against MDR A. baumannii infections.

Transcriptomic analysis reveals zinc-mediated virulence and pathogenicity in multidrug-resistant Acinetobacter baumannii.

Acinetobacter baumannii is a gram-negative bacterium well known for its multidrug resistance and connection to nosocomial infections under ESKAPE pathogens. This opportunistic pathogen is ubiquitously associated with nosocomial infections, posing significant threats within healthcare environments. Its critical clinical symptoms, namely, meningitis, urinary tract infections, bloodstream infections, ventilator-associated pneumonia, and pneumonia, catalyze the imperative demand for innovative therapeutic interventions. The proposed research focuses on delineating the role of Zinc, a crucial metallo-binding protein and micronutrient integral to bacterial metabolism and virulence, to enhance understanding of the pathogenicity of A. baumannii. RNA sequencing and subsequent DESeq2 analytical methods were used to identify differential gene expressions influenced by zinc exposure. Exploiting the STRING database for functional enrichment analysis has demonstrated the complex molecular mechanisms underlying the enhancement of pathogenicity prompted by Zinc. Moreover, hub genes like gltB, ribD, AIL77834.1, sdhB, nuoI, acsA_1, acoC, accA, accD were predicted using the cytohubba tool in Cytoscape. This investigation underscores the pivotal role of Zinc in the virulence of A. baumannii elucidates the underlying molecular pathways responsible for its pathogenicity. The research further accentuates the need for innovative therapeutic strategies to combat A. baumannii infections, particularly those induced by multidrug-resistant strains.

Inhibitory effect of selenium nanoparticles on the biofilm formation of multidrug-resistant Acinetobacter baumannii

Background/Aim: Treatment of infections caused by biofilm-producing multidrug-resistant (MDR) pathogens represents a huge global problem due to primary antimicrobial multi-resistance enhanced by reduced penetration of antibiotics in the biofilm-embedded bacteria. The aim of this study was to determine the capacity of biofilm production among MDR Acine-tobacter baumannii (A. baumannii) isolates obtained from different clinical specimens and to evaluate the inhibitory effect of selenium nanoparticles (SeNPs) coated with cationic polymer cetyltrimethylammonium bromide (CTAB) on the biofilm formation. Methods: Antimicrobial effect of antibiotics (meropenem, imipenem, gentamicin, amikacin, ciprofloxacin, levofloxacin and trimethoprim-sulfa-methoxazole) was determined by disk-diffusion assay, while sensitivity to colistin was determined with E test. All 60 isolates were tested on biofilm production in microtiter plates with crystal violet dye. Minimal biofilm inhib-itory concentration (MBIC) of SeNPs was tested in order to prevent biofilm formation in microtiter plates. Results: All tested clinical isolates were classified as MDR (n = 60) and extensively drug-resistant (XDR, n = 60). Out of the total 60 isolates, 55 isolates (92 %) showed the ability for biofilm formation, with the majority of them classified as strong (42 %) and moderate (42 %) biofilm producers. MBIC values of SeNPs for 55 biofilm-producing isolates ranged from 0.07 to 1.25 mg/mL. Strong biofilm producers had statistically higher MBIC (0.15 mg/mL) in correlation to other biofilm-producing isolates (0.07 mg/ mL). There was no correlation between invasiveness of isolates with biofilm production and MBIC values. Conclusion: Presented results are very promising and interesting especially in nanotechnology and medical fields, while SeNPs with the addition of cationic surfactant inhibit biofilm formation of MDR A. baumannii clinical isolates.

Can risk factors and risk scores help predict colonization and infection in multidrug-resistant gram-negative bacteria?

Abstract Antimicrobial resistance (AMR) is positioning as one of the most relevant threats to global public health and threatens the effective treatment of an ever-growing number of bacterial infections in various healthcare settings, particularly in acute care and surgical units, as well as in the community. Among multidrug-resistant (MDR) gram-negative bacteria (MDRGNB), Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii require special attention, since they account for most of the mortality associated with bacterial infections and are often MDR. It is clear that there is an important global variation in antibiotic resistance profiles among MDRGNB species. Extended-spectrum β-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales, DTR-P. aeruginosa, and MDR-A. baumannii are the focus of this review. Here, we summarize a series of relevant studies on risk factors associated with colonization and infection with these MDRGNB. Likewise, we offer a comparative overview of those studies providing scoring systems to predict the risk of infection with these MDR pathogens, and their pros and cons. Despite the variable accuracy of published risk factors for predicting colonization or infection with MDRGNB, these scores are valuable tools that may help anticipate colonization and infection among those colonized. More importantly, they may help reduce unnecessary use of broad-spectrum antimicrobials and guiding the selection of an optimal treatment.