Dual-targeting tigecycline nanoparticles for treating intracranial infections caused by multidrug-resistant Acinetobacter baumannii.

Multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) is a formidable pathogen responsible for severe intracranial infections post-craniotomy, exhibiting a mortality rate as high as 71%. Tigecycline (TGC), a broad-spectrum antibiotic, emerged as a potential therapeutic agent for MDR A. baumannii infections. Nonetheless, its clinical application was hindered by a short in vivo half-life and limited permeability through the blood-brain barrier (BBB). In this study, we prepared a novel core-shell nanoparticle encapsulating water-soluble tigecycline using a blend of mPEG-PLGA and PLGA materials. This nanoparticle, modified with a dual-targeting peptide Aß11 and Tween 80 (Aß11/T80@CSs), was specifically designed to enhance the delivery of tigecycline to the brain for treating A. baumannii-induced intracranial infections. Our findings demonstrated that Aß11/T80@CSs nanocarriers successfully traversed the BBB and effectively delivered TGC into the cerebrospinal fluid (CSF), leading to a significant therapeutic response in a model of MDR A. baumannii intracranial infection. This study offers initial evidence and a platform for the application of brain-targeted nanocarrier delivery systems, showcasing their potential in administering water-soluble anti-infection drugs for intracranial infection treatments, and suggesting promising avenues for clinical translation.

Synergistic Effects of a Probiotic Culture Extract and Antimicrobial Combinations against Multidrug-Resistant Acinetobacter baumannii.

Background and Objectives: Developing effective treatment outcomes for multidrug-resistant Acinetobacter baumannii (MRAB) infections, with colistin and tigecycline the current frontline therapies, is challenging, because of the risk of renal toxicity and low blood concentrations of active ingredients when administered intravenously. This study aimed to identify the effect of combination therapy using conventional antimicrobial agents that are used for treating drug-resistant bacteria and the additional synergistic effect of four probiotic culture extracts isolated from the human body and Lactobacillus preparations. Materials and Methods: The antimicrobial combination and synergistic effect of adding Lactobacillus extract against 33 strains of A. baumannii isolated from pus, urine, and other specimens submitted to the Department of Laboratory Medicine of a university hospital, located in Gyeonggi-do, Korea, was investigated over a 3-year period between January 2017 and December 2019. Results: Antimicrobial susceptibility tests on bacteria isolated in clinical practice demonstrated that 26 strains (79%) were MRAB, while multi-locus sequence typing indicated that ST191 was the predominant type (45%; n = 15). Checkerboard test results demonstrated that combination therapy using meropenem and colistin had the highest synergistic effect (fractional inhibitory concentration index = 0.5), while the time-kill assay test using Lactobacillus spp. culture extract exhibited an inhibitory effect within 1 h and complete inhibition of MRAB within 3 h. Lactobacillus paracasei exhibited the fastest antimicrobial reactivity and longest sustained antimicrobial activity. Conclusion: These findings provide useful foundational data for an appropriate combination of colistin with other antimicrobial agents for treating MRAB infection in clinical settings, and the use of various probiotic culture extracts to reduce the required dosage, and therefore toxicity of colistin.

Efficacy and Safety of High Loading Dose of Colistin in Multidrug-Resistant Acinetobacter baumannii: A Prospective Cohort Study.

OBJECTIVES: We aimed to assess the efficacy and safety of a high loading dose of colistin and no loading dose of colistin to treat multidrug-resistant (MDR) Acinetobacter baumannii infections. METHODS: We conducted a prospective cohort study of patients with MDR A baumannii infections at a university-affiliated hospital from December 2014 to January 2016. In the high loading dose group, the patients received a high loading dose of 300 mg colistin base activity (CBA) followed by a maintenance dose of 150 mg CBA twice daily, and patients in the no loading dose group received only the maintenance dose. The primary outcome was clinical response. The secondary outcomes were 28-day mortality and microbiological response. RESULTS: A total of 255 cases were identified. The high loading dose of colistin strategy provided no significant difference in good clinical response when compared to the no loading dose group (65.5% vs 70.4%; P = .442), without a significant difference in the development of renal dysfunction (52.3% vs 49.4%; P = .664). However, microbiological eradication was significantly higher among patients who received the high loading dose of colistin when compared to those who received the no loading dose (87.9% vs 70.4%; P = .0006). CONCLUSIONS: The high loading dose of colistin strategy was effective and safe for treating patients with MDR A baumannii.

Discovery of Novel 7-[(1R,5S)-1-Amino-5-fluoro-3-azabicyclo[3.3.0]octan-3-yl]-6-fluoro-1-[(1R,2S)-2-fluorocyclopropane]-8-(methoxy or methyl)quinolones.

A series of 8-methoxy or 8-methylquinolones bearing novel 3-aminooctahydrocyclopenta[c]pyrrole derivatives at the C-7 position was synthesized, and the pharmacological, physicochemical, and toxicological properties of the individual compounds were evaluated. Novel 8-methylquinolone 7, which includes a 3-amino-7-fluorooctahydrocyclopenta[c]pyrrole moiety at the C-7 position, showed potent antibacterial activity against both Gram-positive and negative pathogens. Compound 7 also demonstrated favorable pharmacokinetic and pharmacodynamic properties and an acceptably safe toxicological profile. Consequently, compound 7 was selected as a clinical candidate.

Using the Chinese herb Scutellaria barbata against extensively drug-resistant Acinetobacter baumannii infections: in vitro and in vivo studies.

BACKGROUND: No animal model studies have been conducted in which the efficacy of herbal compounds has been tested against multidrug-resistant Acinetobacter baumannii infections. Very few antibiotics are available for the treatment of pulmonary infections caused by extensively drug-resistant Acinetobacter baumannii (XDRAB). To find alternative treatments, traditional Chinese herbs were screened for their antimicrobial potential. METHODS: The present study screened 30 herbs that are traditionally used in Taiwan and that are commonly prescribed for heat clearing and detoxification. The herbs with antibacterial activities were analysed by disc diffusion assays, time-kill assays and a murine lung infection model. RESULTS: Of the 30 herbs tested, only Scutellaria barbata demonstrated 100% in vitro activity against XDRAB. Furthermore, we compared the antibacterial effect of the S. barbata extract with that of colistin, and the S. barbata extract showed better antibacterial effect. In the XDRAB pneumonia murine model, we compared the antimicrobial effects of the orally administered S. barbata extract (200 mg/kg, every 24 h), the intratracheally administered colistin (75,000 U/kg, every 12 h), and the control group. The bacterial load in the lungs of the treatment group that received the oral S. barbata extract showed a significant decrease in comparison to that in the lungs of the control group. In addition, histopathological examinations also revealed better resolution of perivascular, peribronchial, and alveolar inflammation in the oral S. barbata extract-treated group. CONCLUSIONS: Our in vitro and in vivo data from the animal model support the use of S. barbata as an alternate drug to treat XDRAB pulmonary infections. However, detailed animal studies and clinical trials are necessary to establish the clinical utility of S. barbata in treating XDRAB pulmonary infections.

Successful treatment of multidrug-resistant Acinetobacter baumannii meningitis with ampicillin sulbactam in primary hospital.

Introduction: Acinetobacter baumannii nosocomial infections, especially those due to multi-drug resistant strains, are increasingly detected. We want to find the effective treatment measures about multi-resistant Acinetobacter baumannii infections through this research.Methodology: The clinical features and the outcomes of twelve cases of nosocomial Acinetobacter baumannii meningitis treated with ampicillin sulbactam and intrathecal use of amikacin are reported in primary hospital. All the patients had fever, neck stiffness or meningeal signs, and a low consciousness level, and in their cerebrospinal fluid (CSF), pleocytosis, a low glucose level, and an elevated protein level were noted. For all CSF isolates were resistant to at least two antibiotics used in empirical therapy (third and fourth generation cephalosporins, carbapenems or piperacillin/tazobactam). Four cases sputum culture prompted the growth of Acinetobacter baumannii. Two CSF isolates were intermediate resistant to ampicillin sulbactam, only sensitive to amikacin. The two patients were treated with ampicillin sulbactam and intrathecal use of amikacin.Results: The dosages and the duration of treatment with ampicillin sulbactam were 2 g/1 g every 6 hours and 9-21days. Eleven patients were cured and one patient died of meningitis (8.3%). This patient died of severe respiratory Acinetobacter baumannii infection and severe sepsis. One patient had mild nausea and discomfort, given metoclopramide therapy. There were no serious side effects with the ampicillin sulbactam treatment.Conclusions: In conclusion, ampicillin sulbactam may be effective as therapy for meningitis caused by Acinetobacter baumannii resistant to imipenem and other ß-lactam drugs. Meanwhile, continuous lumbar external drainage and intermittent intrathecal use of amikacin were necessary methods.

Antibacterial activity of exogenous glutathione and its synergism on antibiotics sensitize carbapenem-associated multidrug resistant clinical isolates of Acinetobacter baumannii.

A major clinical impact of A. baumannii is hospital-acquired infections including ventilator-associated pneumonia. The treatment of this pathogen is often difficult due to its innate and acquired resistance to almost all commercially available antibiotics. Infections with carbapenem-associated multidrug resistant A. baumannii is the most problematic. Glutathione is a tripeptide thiol-antioxidant and antibacterial activity of exogenous glutathione was reported in some bacteria. However, clinical relevance and molecular details of the antibacterial activity of glutathione are currently unclear. Seventy clinical isolates of A. baumannii including 63 carbapenem-associated multidrug resistant isolates and a type strain A. baumannii ATCC 19606 were used to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Fractional inhibitory concentration (FIC) and time-killing activity with meropenem and/or glutathione were also determined in the carbapenem-associated multidrug resistant isolates. In addition, the roles of exogenous glutathione in multidrug efflux pumps and ß-lactamase production were examined. Levels of MIC and MBC were ranged from 10 to 15mM of exogenous glutathione. All tested carbapenem-associated multidrug resistant isolates were sensitized by all tested antibiotics in combination with subinhibitory concentrations of glutathione. FIC levels of glutathione with carbapenem (meropenem) were all<0.5 and the carbapenem-associated multidrug resistant isolates were killed by subinhibitory concentrations of both glutathione and meropenem at>2log10 within 12h, suggesting glutathione synergistically interacts with meropenem. The roles of multidrug efflux pumps and ß-lactamase production were excluded for the glutathione-mediated antibiotic susceptibility. Overall results demonstrate that the antibacterial activity of glutathione is clinically relevant and its synergism on antibiotics sensitizes clinical isolates of A. baumannii regardless of their resistance or susceptibility to antibiotics. This finding suggests that exogenous glutathione alone and/or in combination with existing antibiotics may be applicable to treat infections with carbapenem-associated multidrug resistant A. baumannii.

Azithromycin inhibits MUC5AC induction via multidrug-resistant Acinetobacter baumannii in human airway epithelial cells.

Acinetobacter baumannii is one of the main pathogens that cause ventilator-associated pneumonia (VAP). Hypersecretion of mucin in the airway is associated with the onset of VAP. Furthermore, macrolides are known to accelerate the resolution of VAP. However, this mechanism has not been elucidated. We examined whether macrolides inhibit MUC5AC production that is induced by multidrug-resistant A. baumannii (MDRAB). MUC5AC production in bronchial cells after MDRAB stimulation was analyzed by enzyme-linked immunosorbent assay and quantitative reverse transcription-polymerase chain reaction. For the inhibition study, cells were treated with azithromycin (AZM) or clarithromycin (CAM) simultaneously along with MDRAB stimulation. Western blotting was performed was performed to determine potential rules for signal modules. MDRAB induced MUC5AC production and gene expression. The EGFR-ERK/JNK-NF-κB pathway was involved in MDRAB-induced MUC5AC production. AZM but not CAM inhibited MUC5AC production. AZM suppressed the phosphorylation of ERK/JNK and the nuclear translocation of NF-κB. Our results suggest that the efficacy of macrolides against VAP may be due to the inhibition of mucin production.

Characterization and therapeutic potential of MRABP9, a novel lytic bacteriophage infecting multidrug-resistant Acinetobacter baumannii clinical strains.

Acinetobacter baumannii is one of the most important pathogens of healthcare-associated infections. The rising prevalence of multidrug-resistant A. baumannii (MRAB) strains and biofilm formation impact the outcome of conventional treatment. Phage-related therapy is a promising strategy to tame troublesome multidrug-resistant bacteria. Here, we isolated and evaluated a highly efficient lytic phage called MRABP9 from hospital sewage. The phage was a novel species within the genus Friunavirus and exhibited lytic activity against 2 other identified MRAB strains. Genomic analysis revealed it was a safe virulent phage and a pectate lyase domain was identified within its tail spike protein. MRABP9 showed potent bactericidal and anti-biofilm activity against MRAB, significantly delaying the time point of bacterial regrowth in vitro. Phage administration could rescue the mice from acute lethal MRAB infection. Considering its features, MRABP9 has the potential as an efficient candidate for prophylactic and therapeutic use against acute infections caused by MRAB strains.

Molecular epidemiology of multidrug-resistant Acinetobacter baumannii isolates from a hospital in Nepal.

OBJECTIVES: The emergence of multidrug-resistant (MDR) Acinetobacter baumannii has become a serious worldwide medical problem. This study was designed to clarify the genetic and epidemiological properties of MDR A. baumannii clinical isolates. METHODS: A total of 66 MDR A. baumannii isolates were obtained from 66 inpatients between May 2019 and February 2020 in a university hospital in Nepal. Whole genomes of these isolates were sequenced using next-generation sequencing. Phylogenetic trees were constructed from single nucleotide polymorphism concatemers. Multilocus sequence typing (MLST) and clonal complex (CC) analysis were conducted, and drug-resistance genes were identified. RESULTS: Of the 66 isolates, 26 harboured a gene encoding NDM-type metallo-ß-lactamase, and 55 harboured a gene encoding the 16S rRNA methyltransferase, ArmA. All isolates had point mutations in the quinolone-resistance-determining regions of gyrA and parC. Phylogenetic analysis showed that 55 isolates harboured armA, 26 harboured blaNDM-1, and14 harboured blaPER-7. Multilocus sequence typing and CC analysis revealed that 34 isolates belonged to CC2 (ST2), 10 to CC1 (nine ST1 and one ST623), and eight to CC149 (ST149). Compared to our previous study on MDR A. baumannii in Nepal in 2012, the isolation rate of CC2 increased, whereas that of CC149 decreased between 2012 and 2020. CONCLUSIONS: This study indicates that MDR A. baumannii producing carbapenemase and 16S rRNA methyltransferase, with high resistance to carbapenems and/or aminoglycosides, are spreading in medical settings in Nepal. The genetic backgrounds of MDR A. baumannii isolates have shifted to international clone 2 over several years.

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

PURPOSES: This 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). METHODS: We 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. RESULTS: Both 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. CONCLUSION: Nearly 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.

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.

Efficacy of Cefiderocol, a Novel Siderophore Cephalosporin, against Multidrug Resistant Acinetobacter baumannii Clinical Isolates in Japan.

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important pathogen that causes nosocomial infections and is resistant to almost all antibiotics, including carbapenems. Cefiderocol is a novel siderophore cephalosporin active against a broad spectrum of gram-negative bacteria. However, the susceptibility of MDRAB to cefiderocol has not yet been reported in Japan. In this study, we measured the minimum inhibitory concentrations (MICs) of antibiotics including cefiderocol against MDRAB clinical isolates collected during a nosocomial outbreak between 2009 and 2010 at the Teikyo University Hospital in Japan. We found that all 10 MDRAB clinical isolates tested were susceptible to cefiderocol, with an MIC range of 0.12 to 1 µg/mL. All the isolates also exhibited resistance to ampicillin-sulbactam and an intermediate resistance to colistin, whereas nine of them were susceptible to tigecycline. DNA sequencing revealed that all strains harbored an OXA-51-like carbapenemase, a major cause of carbapenem resistance in A. baumannii in Japan. In conclusion, this study showed that the cefiderocol susceptibility of MDRAB clinical isolates in Japan was equivalent to that to colistin or tigecycline, and thus cefiderocol is a potential treatment option for MDRAB infections.

An Ancient Drug for a Modern Era: Minocycline for the Treatment of Multi-Drug-Resistant Acinetobacter baumannii.

INTRODUCTION: Infections caused by Acinetobacter baumannii are a major cause of health concerns in the hospital setting. Moreover, the presence of extreme drug resistance in A. baumannii has made the scenario more challenging due to limited treatment options thereby encouraging the researchers to explore the existing antimicrobial agents to combat the infections caused by them. This study focuses on the susceptibility of multi-drug-resistant A. baumannii (MDR-AB) strains to minocycline and also to colistin. METHODOLOGY: A cross-sectional study was conducted from June 2022 to June 2023. One hundred isolates of​​​​​​ A. baumannii â€‹â€‹â€‹obtained from various clinical samples were sent to Central Laboratory, Department of Microbiology, Sree Balaji Medical College and Hospital, Chrompet, Chennai, India. The antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, 2022. For the standard antibiotics, the disc diffusion method was performed. For minocycline and colistin, the minimum inhibitory concentration (MIC) was determined using an epsilometer strip (E-strip) test. RESULTS: In this study, 100 isolates of A. baumannii were obtained, and 83% of the isolates were multi-drug-resistant. Among the MDR-AB, 50 (60%) were susceptible to minocycline and 40 (48%) were susceptible to colistin. Out of the 40 colistin-susceptible A. baumannii strains, 29 (73%) were susceptible to minocycline with a statistically significant P-value of <0.05. Among the 43 colistin-resistant A. baumannii strains, 21 (53%) were susceptible to minocycline with a statistically significant P-value of <0.05. CONCLUSIONS: When taking into account the expense of treating carbapenemase-producing Gram-negative bacteria, colistin and minocycline can be used as an alternative drug as they have fewer side effects and are more affordable. Minocycline can be used as an alternative to colistin because it is feasible to convert from an injectable to an oral formulation.

The Prevalence of Multidrug-Resistant Acinetobacter baumannii and Its Vaccination Status among Healthcare Providers.

There is growing concern among healthcare providers worldwide regarding the prevalence of multidrug-resistant Acinetobacter baumannii (A. baumannii). Some of the worst hospital-acquired infections, often in intensive care units (ICUs), are caused by this bacterial pathogen. In recent years, the rise in multidrug-resistant A. baumannii has been linked to the overuse of antimicrobial drugs and the lack of adequate infection control measures. Infections caused by this bacterial pathogen are the result of prolonged hospitalization and ICU stays, and they are associated with increased morbidity and mortality. This review outlines the epidemiology, risk factors, and antimicrobial resistance associated with A. baumannii in various countries, with a special focus on the Kingdom of Saudi Arabia. In response to the growing concern regarding this drug-resistant bacteria, fundamental information about its pathology has been incorporated into the development of vaccines. Although these vaccines have been successful in animal models, their effectiveness in humans remains unproven. The review will discuss the development of A. baumannii vaccines, potential related obstacles, and efforts to find an effective strategy against this pathogen.

Epidemiological characteristics of multidrug-resistant Acinetobacter baumannii ST369 in Anhui, China.

IMPORTANCE: Acinetobacter baumannii is a major health threat due to its antibiotic resistance and ability to cause nosocomial infections. Epidemiological studies indicated that the majority of globally prevalent ST369 clones originated from China, indicating a significant impact on public health in the country. In this study, we conducted whole-genome sequencing, comparative genomics, and Galleria mellonella infection model on eight A. baumannii ST369 isolates collected from a provincial hospital in China to comprehensively understand the organism. We identified two mutations (G540A and G667D) on the wzc gene that can affect bacterial virulence and viscosity. We confirmed their impact on resistance and virulence. We also investigated the potential involvement of AB46_0125 and AB152_03903 proteins in virulence. This finding provides a theoretical reference for further research on A. baumannii ST369 clinical isolates with similar mutations.

Glycyrrhetinic acid protects against Multidrug-resistant Acinetobacter baumannii-induced lung epithelial cells injury by regulating inflammation and oxidative stress.

Glycyrrhetinic acid (GA) is a bio-effective component of Licorice. The GA is a monomer and the ingredient is an Oleanane-type pentacyclic triterpenes that has been used as a remedy for years. Due to the abuse of antibiotics, people pay attention to the emergence of Multidrug-resistant Acinetobacter baumannii (MDR-AB). As a conditional pathogen, MDR-AB causes severe infection, endangering human lives. Our previous studies found GA played an important role in Yinhua Pinggan, a Chinese medicine. However, whether GA could protect lung epithelium from MDR-AB-induced cell injury was elusive. Herein, we investigated the effects of GA on MDR-AB-infected A549 cells. The results showed GA had slightly antibacterial activity to MDR-AB in the GA (high concentration) but no impact on drug resistance genes. Notwithstanding, GA could reverse MDR-AB-induced cell apoptosis, hampered adhesion and invasion of MDR-AB to cells, and inhibit pro-inflammatory cytokines expression of IL-1ß, IL-6, and TNF. Besides, MDR-AB-induced reactive oxygen species, pro-oxidative protein malonaldehyde, and myeloperoxidase of cells were decreased by GA, while antioxidative proteins were recovered, showing antioxidative capacity of GA might play a critical role. The expressions of toll-like receptor (TLRs) - 1, 2, 4, 5, 6, and 9 were increased by MDR-AB infection, while GA reversed the tendency. Interestingly, GA inhibited MDR-AB induced myeloiddifferentiationfactor88 expression (MYD88), one downstream con-factors of TLRs, but no affection on Interferon regulatory Factor 3 (IRF3), the other one, indicating GA inhibited MDR-AB induced cell injury by impact TLR/MYD88 pathway to attenuate inflammation. Altogether, our results demonstrated that GA protects against MDR-AB-induced cell injury through its antioxidative and anti-inflammatory properties, which deserve further study in the future.

Carboxymuconolactone decarboxylase is a prospective molecular target for multi-drug resistant Acinetobacter baumannii-computational modeling, molecular docking and dynamic simulation studies.

Multidrug-resistant Acinetobacter baumannii (MDRAb), a priority-I pathogen declared by the World Health Organization, became a potential healthcare concern worldwide with a high mortality rate. Thus, the identification of putative molecular targets and potential lead molecules is an important concern in healthcare. The present study aimed to screen a prospective molecular target and effectual binders for the drug discovery of MDRAb by computational virtual screening approach. Based on the functional role, γ-carboxymuconolactone decarboxylase (CMD) was prioritized as the target and its three-dimensional (3D) structure was computationally modeled. Based on the availability of the 3D structure, twenty-five herbal molecules were selected by database search, and their drug-likeliness, pharmacokinetic, and toxicity features were predicted. The effectual binding of the selected molecules towards CMD was predicted by molecular docking. The stability of the best-docked complexes was predicted by molecular dynamics (MD) simulation for 100 ns and binding energy calculations were carried out by molecular mechanics generalized Born and surface area solvation (MM/GBSA) method. Out of twenty-five molecules screened, hirsutine (an indole alkaloid of Uncaria rhynchophylla) and thymoquinone (a phytochemical of Nigella sativa) were qualified for drug likeliness, pharmacokinetic, and toxicity features and demonstrated significant effectual binding to CMD when compared with the binding of co-crystallized inhibitor and CMD (control). The docked complexes of hirsutine and thymoquinone, and CMD were stabilized by the binding energies of -8. 30 and -8. 46 kcal/mol respectively. These molecules were qualified in terms of ideal drug likeliness, ADME, and toxicity properties. MD simulation studies showed that the ligand-protein complexes were stable throughout the simulation. The binding free energies of the complexes by MMGBSA were estimated to be -42.08157745 kcal/mol and -36.58618242 kcal/mol for hirsutine and thymoquinone respectively when compared with the calculated binding free energy of the control (-28.75032666 kcal/mol). This study concluded that hirsutine and thymoquinone can act as potential lead molecules against CMD and the present hypothesis can be scaled up to develop potential inhibitors against MDRAb.

GATR-3, a Peptide That Eradicates Preformed Biofilms of Multidrug-Resistant Acinetobacter baumannii.

Acinetobacter baumannii is a gram-negative bacterium that causes hospital-acquired and opportunistic infections, resulting in pneumonia, sepsis, and severe wound infections that can be difficult to treat due to antimicrobial resistance and the formation of biofilms. There is an urgent need to develop novel antimicrobials to tackle the rapid increase in antimicrobial resistance, and antimicrobial peptides (AMPs) represent an additional class of potential agents with direct antimicrobial and/or host-defense activating activities. In this study, we present GATR-3, a synthetic, designed AMP that was modified from a cryptic peptide discovered in American alligator, as our lead peptide to target multidrug-resistant (MDR) A. baumannii. Antimicrobial susceptibility testing and antibiofilm assays were performed to assess GATR-3 against a panel of 8 MDR A. baumannii strains, including AB5075 and some clinical strains. The GATR-3 mechanism of action was determined to be via loss of membrane integrity as measured by DiSC3(5) and ethidium bromide assays. GATR-3 exhibited potent antimicrobial activity against all tested multidrug-resistant A. baumannii strains with rapid killing. Biofilms are difficult to treat and eradicate. Excitingly, GATR-3 inhibited biofilm formation and, more importantly, eradicated preformed biofilms of MDR A. baumannii AB5075, as evidenced by MBEC assays and scanning electron micrographs. GATR3 did not induce resistance in MDR A. baumannii, unlike colistin. Additionally, the toxicity of GATR-3 was evaluated using human red blood cells, HepG2 cells, and waxworms using hemolysis and MTT assays. GATR-3 demonstrated little to no cytotoxicity against HepG2 and red blood cells, even at 100 µg/mL. GATR-3 injection showed little toxicity in the waxworm model, resulting in a 90% survival rate. The therapeutic index of GATR-3 was estimated (based on the HC50/MIC against human RBCs) to be 1250. Overall, GATR-3 is a promising candidate to advance to preclinical testing to potentially treat MDR A. baumannii infections.

The Impact of Multidrug-Resistant Acinetobacter baumannii Infection in Critically Ill Patients with or without COVID-19 Infection.

This is a single-center, retrospective, cohort study aimed to evaluate the clinical outcomes of multi-drug resistance in Acinetobacter baumannii infections (MDR-AB) in intensive care unit (ICU) patients with or without a COVID-19 infection and risk factors for blood stream infection. A total of 170 patients with MDR-AB were enrolled in the study. Of these, 118 (70%) patients were admitted to the ICU due to a COVID-19 infection. Comparing the COVID-19 and non-COVID-19 groups, the use of mechanical ventilation (98.31% vs. 76.92%, p = 0.000), the presence of septic shock (96.61% vs. 82.69%, p = 0.002), and the use of steroid (99.15% vs. 71.15%, p = 0.000) and tocilizumab therapies (33.05% vs. 0%, p = 0.000) were more prevalent and statistically more significant in patients with COVID-19 infections. The average length of the ICU stay (21.2 vs. 28.33, p = 0.0042) was significantly lower in patients with COVID-19 infections. Survival rate was 21.19% for the COVID-19 group and 28.85% for non-COVID-19 group with a p-value = 0.0361. COVID-19 status was associated with significantly higher hazards of death (HR 1.79, CI 95% 1.02-3.15, p = 0.043). Higher SOFAB (15.07 vs. 12.07, p = 0.0032) and the placement of an intravascular device (97.06% vs. 89.71%, p = 0.046) were significantly associated with the development of a bloodstream infection. Our study has shown that critically ill patients with an MDR-AB infection, who were admitted due to a COVID-19 infection, had a higher hazard for death compared to non-COVID-19 infected patients.