Multidrug-resistant Acinetobacter Baumannii Research Articles

Resistance mechanisms for Gram-negative bacteria-specific lipopeptides, turnercyclamycins, differ from that of colistin.

Turnercyclamycin A and B lipopeptides exhibit Gram-negative bacteria-specific toxicity. This includes CDC urgent threat organisms such as multidrug-resistant Acinetobacter baumannii. Like the last-line agent colistin, turnercyclamycins interact with the lipopolysaccharide (LPS) pathway, but they remain active against clinical isolates that are colistin resistant. Here, we aimed to determine why turnercyclamycins A and B show little cross-resistance with colistin despite some potential mechanistic and structural similarities. The outer membrane was important in the actions of all three agents, since the deletion of lpxC that synthesizes LPS and the addition of exogenous LPS led to resistance to turnercyclamycins and colistin. Even so, it was much more difficult to generate resistance to turnercyclamycin A than turnercyclamycin B. In Escherichia coli, disruption of the mlaA gene, which is involved in outer membrane homeostasis, resulted in resistance to turnercyclamycin B. However, mlaA disruption blocked neither turnercyclamycin A nor colistin activity. This activity was recapitulated in A. baumannii, where transposon mutants were more resistant to turnercyclamycin B. Moreover, the common A. baumannii colistin resistance gene mcr-1 blocked colistin activity in E. coli but did not affect turnercyclamycins. These results demonstrate a unique resistance profile for turnercyclamycins A and B, in addition to suggesting differences in the mechanism of action. Further, turnercyclamycin A was effective in a mouse model of A. baumannii infection, indicating that this compound class may have potential promise in treating drug-resistant infections.IMPORTANCEBacterial resistance to antibiotics is a crisis. Acinetobacter baumannii is among the CDC urgent threat pathogens in part for this reason. Lipopeptides known as turnercyclamycins are produced by symbiotic bacteria that normally live in marine mollusks, where they may be involved in shaping their symbiotic niche. Turnercyclamycins killed Gram-negative pathogens including drug-resistant Acinetobacter, but how do the mechanisms of resistance compare to other lipopeptide drugs? Here, we define resistance from a truncation of MlaA, a protein involved in regulating bacterial membrane phospholipids. Intriguingly, this resistance mechanism only affected one turnercyclamycin variant, which differed only in two atoms in the lipid tail of the compounds. We could not obtain significant resistance to the second turnercyclamycin variant, which was also effective in an infection model. This study reveals an unexpected subtlety in resistance to lipopeptide antibiotics, which may be useful in the design and development of antibiotics to combat drug resistance.

Antimicrobial peptide 2K4L disrupts the membrane of multidrug-resistant Acinetobacter baumannii and protects mice against sepsis.

Antimicrobial peptides represent a promising therapeutic alternative for the treatment of antibiotic-resistant bacterial infections. 2K4L is a rationally-designed analog of a short peptide temporin-1CEc, a natural peptide isolated and purified from the skin secretions of the Chinese brown frog Rana chensinensis by substituting amino acid residues. 2K4L adopt an α-helical confirm in a membrane-mimetic environment and displayed an improved and broad-spectrum antibacterial activity against sensitive and multidrug-resistant Gram-negative and Gram-positive bacterial strains. Here, the action mechanism of 2K4L on multidrug resistant Acinetobacter baumannii (MRAB) and protection on MRAB-infected mice was investigated. The results demonstrated high bactericidal activity of 2K4L against both a multidrug resistant A. baumannii 0227 strain (MRAB 0227) and a sensitive A. baumannii strain (AB 22934), indicating a potential therapeutic advantage of this peptide. Strong positively-charged residues significantly promoted the electrostatic interaction on 2K4L with lipopolysaccharides (LPS) of the bacterial outer membrane. High hydrophobicity and an α-helical confirm endowed 2K4L remarkably increase the permeability of A. baumannii cytoplasmic membrane by depolarization of membrane potential and disruption of membrane integration, as well as leakage of fluorescein from the liposomes. Additionally, 2K4L at low concentrations inhibited biofilm formation and degraded mature 1-day-old MRAB 0227 biofilms by reducing the expression of biofilm-related genes. In an invasive A. baumannii infection model, 2K4L enhanced the survival of sepsis mice and decreased the production of the proinflammatory cytokines downregulating the phosphorylation level of signaling protein in MAPK and NF-κB signaling pathways, indicating that 2K4L represents a novel therapeutic antibiotic candidate against invasive multidrug-resistant bacterial strain infections.

Medicinal plant Miconia albicans synergizes with ampicillin and ciprofloxacin against multi-drug resistant Acinetobacter baumannii and Staphylococcus aureus

BackgroundGiven the rising occurrence of antibiotic resistance due to the existence and ongoing development of resistant bacteria and phenotypes, the identification of new treatments and sources of antimicrobial agents is of utmost urgency. An important strategy for tackling bacterial resistance involves the utilization of drug combinations, and natural products derived from plants hold significant potential as a rich source of bioactive compounds that can act as effective adjuvants. This study, therefore, aimed to assess the antibacterial potential and the chemical composition of Miconia albicans, a Brazilian medicinal plant used to treat various diseases.MethodsEthanolic extracts from leaves and stems of M. albicans were obtained and subsequently partitioned to give the corresponding hexane, chloroform, ethyl acetate, and hydromethanolic phases. All extracts and phases had their chemical constitution investigated by HPLC–DAD-MS/MS and GC–MS and were assessed for their antibiofilm and antimicrobial efficacy against Staphylococcus aureus. Furthermore, their individual effects and synergistic potential in combination with antibiotics were examined against clinical strains of both S. aureus and Acinetobacter baumannii. In addition, 10 isolated compounds were obtained from the leaves phases and used for confirmation of the chemical profiles and for antibacterial assays.ResultsBased on the chemical profile analysis, 32 compounds were successfully or tentatively identified, including gallic and ellagic acid derivatives, flavonol glycosides, triterpenes and pheophorbides. Extracts and phases obtained from the medicinal plant M. albicans demonstrated synergistic effects when combined with the commercial antibiotics ampicillin and ciprofloxacin, against multi-drug resistant bacteria S. aureus and A. baumannii, restoring their antibacterial efficacy. Extracts and phases also exhibited antibiofilm property against S. aureus. Three key compounds commonly found in the samples, namely gallic acid, quercitrin, and corosolic acid, did not exhibit significant antibacterial activity when assessed individually or in combination with antibiotics against clinical bacterial strains.ConclusionsOur findings reveal that M. albicans exhibits remarkable adjuvant potential for enhancing the effectiveness of antimicrobial drugs against resistant bacteria.

Synergistic Peptide-Antibiotic Approach to Combat Multidrug-Resistant Acinetobacter baumannii

Background: Antibacterial peptides have a broad antibacterial spectrum and are not affected by classical resistance mechanisms; therefore, they can be used in combination with classic antibiotics to treat multidrug-resistant Acinetobacter baumannii infections, making them an alternative for the development of new therapeutic strategies. Objectives: This study aimed to assess the effectiveness of combining amphiphilic peptides, specifically C12-prp and mastoparan, with antibiotics in combating A. baumannii clinical isolates. Methods: We investigated combinations that inhibited the growth of A. baumannii clinical isolates, consisting of 24 extensively drug-resistant (XDR) and 11 pan-drug-resistant (PDR) strains collected between January 2004 and December 2014 at Chosun University Hospital using a multiple combination bactericidal test (MCBT). A time-kill study was used to confirm the bactericidal activity and synergism of the four combinations selected via MCBT. Results: Four combinations (C12-prp-colistin, C12-prp-rifampicin, mastoparan-colistin, and mastoparan-rifampicin) showed 100% (24/24) synergy with XDR A. baumannii strains. However, in the case of the PDR strains, only two combinations, C12-prp-colistin and mastoparan-colistin, showed a 9.1% (1/11) synergy. Moreover, the mastoparan-colistin and mastoparan-rifampicin combinations showed 100% (24/24) bactericidal activity against the XDR A. baumannii strains, whereas the C12-prp-colistin and C12-prp-rifampicin combinations showed 91.7% (22/24) bactericidal activity. None of the combinations showed bactericidal activity against PDR strains. Conclusions: Our study highlighted the substantial synergistic antibacterial efficacy of C12-prp and mastoparan peptides when combined with colistin or rifampicin. Furthermore, this approach could be a promising alternative for developing new treatment strategies for XDR A. baumannii infections.

In vitro and in vivo antimicrobial potential of lithium complex against multi-drug resistant Acinetobacter baumannii.

Acinetobacter baumannii is a Gram-negative pathogen, accountable for lethal nosocomial infections, owing to high pathogenicity and multi-drug resistance (MDR). Hence, the World Health Organization has prioritized this bacterium against which new pharmacophores are required urgently. Therefore, this study evaluates the antimicrobial potential of lithium complex based on salicylic acid, and 1,10-phenanthroline {[Li(phen)2sal]} against MDR A. baumannii (MDRAB) through growth inhibition, growth curve assay, biofilm inhibition, and eradication alongside microscopy. The mechanism of action was proposed by flow cytometry and proteomic analysis. Moreover, in vivo efficacy was assessed using an A. baumannii-induced pneumonia model in mice. Results showed that lithium complex significantly inhibited the bacterial growth at 16-32 µg/mL. Growth kinetics revealed that it retarded the bacterial growth after 2-3 h of treatment. Lithium complex significantly inhibited and reduced >70% of biofilms at the MIC level which is a key problem of indwelling and prosthetic devices. Light and atomic force microscopy further indicated disarticulated biofilm and ruptured cellular membrane post-lithium complex treatment. Proteomic analysis revealed that the compound exerted oxidative stress on A. baumannii which may contribute to cell rupturing. Data are available via ProteomeXchange with identifier PXD044293. Flow cytometry confirmed its role in cytoplasmic membrane disintegration. The lithium complex ameliorated the pneumonia symptoms at non-toxic doses of 20 and 40 mg/kg in the pre-clinical A. baumannii-induced pneumonia model as evident by the significant reduction in bacterial burden and parenchymal inflammation. Taken together, these findings suggest that the lithium complex can be a potential drug candidate against MDRAB.IMPORTANCEMulti-drug resistance (MDR) by virtue of evolving resistance and virulence mechanisms among A. baumannii is a global concern which is responsible for lethal hospital-acquired infections. Therefore, it is crucial to develop new therapeutics against it. Metal complexes are compact structures with diverse mechanisms that the pathogens cannot evade easily which make them a strong drug candidate. In this study, we assessed the in vitro and in vivo efficacy of lithium complex {[Li(phen)2 sal]} against biofilm-forming MDR A. baumannii. The lithium complex displayed strong antimicrobial activity and reduced the pre-formed mature biofilm which is key barrier for antimicrobial action. Moreover, it employs oxidative stress as one of its mode of actions and causes cellular rupturing. Lithium complex was non-toxic and was significantly effective to overcome pneumonia in mice model. These results highlight the untapped potential of metal complexes that can be explored and utilized for combating notorious A. baumannii infections.

Early detection of a possible multidrug-resistant Acinetobacter baumannii outbreak in the local hospital setting by using random amplified polymorphism DNA-polymerase chain reaction (RAPD-PCR), oxacillinase gene profiles, and antibiograms.

Detecting the source of a potential outbreak of multidrug resistant (MDR) Acinetobacter baumannii is necessary to be investigated. This study aimed to detect the possibility of A. baumannii outbreak in a hospital setting using a combination of random amplified polymorphism DNA-polymerase chain reaction (RAPD-PCR), antibiograms, and the presence of oxacillinase genes. The antibiogram of 31 clinical isolates and six environmental isolates of A. baumannii were determined by Vitek® 2 Compact. Oxacillinase genes (OXA-23, -24, -51, and -58) were detected by PCR, and RAPD-PCR was conducted using DAF-4 and ERIC-2 primers. The Similarity Index and dendrogram were generated using GelJ v2.3 software. The antibiograms showed that all MDR A. baumannii isolates has very limited susceptibility to cephalosporins, but mostly susceptible to tigecycline. All isolates were positive for bla OXA-51-like gene, thirty-two of 37 total isolates (86.5%) were positive for bla OXA-23-like gene, and none were positive for bla OXA-24-like and bla OXA-58-like genes. RAPD-PCR showed that the DAF-4 primer on average had more band visualization and lower Similarity Index's variation compared to the ERIC-2. The discriminatory power of DAF-4 was 0.906. There was a significant correlation between the DAF-4 dendrogram pattern with the antibiogram (r=0.494, p<0.001) and the presence of bla OXA-23-like gene (r=0.634, p<0.001) from all ICU A isolates. Six out of fourteen ICU A isolates belonged to the same cluster with >95% Similarity Index, while one clinical isolate having an identical dendrogram and antibiogram pattern with an environmental isolate within this cluster. There is a high probability of MDR A. baumannii outbreak within ICU A detected by multiple analysis of RAPD-PCR, antibiogram and the bla OXA-23-like gene profiles. This combinatorial approach is conceivable to mitigate possible outbreak situations of A. baumannii in the local hospital without sophisticated microbiology laboratory.

Role of Efflux Pump Gene adeIJK to Multidrug Resistance in Acinetobacter baumannii Clinical Isolates

Background: The emergence of multidrug-resistant Acinetobacter baumannii (MDRAB) as a nosocomial pathogen is one of the major public health problems. This study aimed to evaluate the role of an efflux pump gene adeJ for the multidrug resistance of A. baumannii clinical isolates. Methods: Two groups, MDRAB and susceptible A. baumannii (SAB), of baumannii clinical isolates were studied. The SAB group consisted of strains that did not meet the criteria of MDRAB and were susceptible to more categories of antibiotics than MDRAB. Antimicrobial susceptibility results obtained by the VITEKⅡ system were used in data analysis and bacterial group allocation. We performed real-time reverse transcription PCR to determine the relative expression of adeJ. We compared the relative expression of adeJ in comparison groups by considering two viewpoints: (1) MDRAB and SAB groups,and (2) susceptible and non-susceptible groups for each antibiotic used in this study.Results: The mean value of relative expression of adeJ of MDRAB and SAB groups was 1.4 and 0.92, respectively, and showed significant differences (P = 0.002). The mean values of relative expression of adeJ of susceptible and non-susceptible groups to the antibiotics cefepime, ceftazidime, ciprofloxacin, imipenem, meropenem, tigecycline, piperacillin/tazobactam, ticarcillin/clavulanic acid, trimethoprim/sulfamethoxazole, piperacillin, and gentamicin showed statistically significant differences (P &lt; 0.05). Conclusion: The overexpression of adeIJK might contribute to the multi-drug resistance in A. baumannii clinical isolates. Further, the overexpression of adeIJK might be one of the factors contributing to the resistance to numerous antibiotics.

Evaluation of Activity of Zinc Oxide Nanoparticles on Human Rotavirus and Multi-Drug Resistant Acinetobacter Baumannii.

Rotaviruses are the cause of acute gastroenteritis and severe diarrheal diseases in children worldwide. Children under the age of five are more susceptible to rotavirus infections. Due to such as the lack of effective drugs and supportive therapy only, the development of new antiviral agents against rotaviruses. Multi-drug-resistant Acinetobacter baumannii is also one of the most challenging Gram-negative bacteria to control and treat due to its antibiotic resistance, particularly in intensive care units. This study aimed to investigate the activity of zinc oxide nanoparticles against human rotavirus and multi-drug resistant Acinetobacter baumannii. The standard 50% tissue culture infectious dose method and the real-time polymerase chain reaction assay were used to investigate the effects of zinc oxide nanoparticles on rotaviruses. The well diffusion and the minimum inhibitory concentration method were used to assess the antibacterial activity of zinc oxide nanoparticles against Acinetobacter baumannii. 300 μg/ml of zinc oxide nanoparticles demonstrated the highest anti-rotavirus effects, resulting in a 3.16 logarithmic decrease in virus infectious titer, and a four-unit increase in the cycle threshold value of the real-time polymerase chain reaction assay compared to the untreated control (P value <0.001 and P value = 0.005, respectively). The diameter of the inhibition zone of zinc oxide nanoparticles solution against Acinetobacter baumannii was 17 mm. The minimum inhibitory concentration results of the zinc oxide nanoparticles solution against Acinetobacter baumannii was 1.56 mg/ml. Our findings showed that zinc oxide nanoparticles could be considered a promising antimicrobial compound.

Insights into Biofilm-based Multidrug Resistance in Acinetobacter Baumannii Isolated from Patients Hospitalized in Benha University Intensive Care Unit

Insights into Biofilm-based Multidrug Resistance in Acinetobacter Baumannii Isolated from Patients Hospitalized in Benha University Intensive Care Unit

Phenotypic and Genotypic Characterization of Recently Isolated Multidrug-Resistant Acinetobacter baumannii Clinical and Aquatic Strains and Demonstration of Silver Nanoparticle Potency.

This study aims to demonstrate the effectiveness of silver nanoparticles (Ag NPs) on multidrug-resistant (MDR) Acinetobacter baumannii (AB) strains isolated from the clinical and aquatic environment. Three types of Ag NPs were investigated for their antimicrobial, antibiofilm, and antivirulence properties on a total number of 132 AB strains isolated in the same temporal sequence from intra-hospital infections (IHIs), wastewater (WW), and surface water (SW) samples between 2019 and 2022 from different Romanian locations and characterized at the phenotypic and genotypic levels. The comparative analysis of the antimicrobial resistance (AR) profiles according to the isolation source and the geographical location demonstrated a decrease in MDR level in AB recovered from WW samples in 2022 from north-eastern/central/southern regions (N-E/C-W/analyzed strains S): 87.5/60/32.5%. The AB strains were lecithinase, caseinase, amylase, and lipase producers, had variable biofilm formation ability, and belonged to six genotypes associated with the presence of different virulence genes (ompA, csuE, bap, and bfmS). The Ag NPs synthesized with the solvothermal method exhibited an inhibitory effect on microbial growth, the adherence capacity to the inert substratum, and on the production of soluble virulence factors. We report here the first description of a powerful antibacterial agent against MDR AB strains circulating between hospitals and anthropically polluted water in Romania.

Current viewpoint on the epidemiology of nonfermenting Gram-negative bacterial strains.

This article aims to review the epidemiology of nonfermenting Gram-negative bacilli (NFGNB) based on recent literature reports, particularly, of the less common, but with emerging clinical significance species. The reported frequency of multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa is increasing, with very significant variability, however, between different countries. Apart from the major NFGNB, that is, A. baumannii and P. aeruginosa, already recognized as of critical importance healthcare risks, several other NFGNB genera have been increasingly associated with diverse severe infections, such as Stenotrophomonas maltophilia, Burkholderia spp., Elizabethkingia spp., Chryseobacterium spp., Achromobacter spp., Alcaligenes spp., Sphingomonas spp., Shewanella spp. and Ralstonia spp., among others. The exploration of the epidemiology, as well as the pathogenic potential of the of the less frequent, but emerging and increasingly reported NFGNB, is crucial, not only for immunocompromised patients, but also for critically ill patients without overt immunosuppression. As we are heading fast towards a postantibiotic era, such information would contribute to the optimal antimicrobial management, that is, providing prompt, appropriate antimicrobial coverage when needed and, at the same time, avoiding overuse and/or inappropriate use of antimicrobial therapy. Also, it would help to better understand their transmission dynamics and to develop effective prevention strategies.

Molecular Typing of Multidrug-Resistant Acinetobacter baumannii Isolates from Clinical Specimens by ERIC-PCR and MLVA.

Acinetobacter baumannii, a Gram-negative and oxidase-negative bacterium, is a major cause of nosocomial infections, leading to high mortality rates in hospitalized patients. The use of 2 prominent molecular typing methods (i.e., enterobacterial repetitive intergenic consensus-polymerase chain reaction [ERIC-PCR] and multiple-locus variable-number tandem repeat [VNTR] analysis [MLVA]) for genotyping A. baumannii isolates has proven to be an effective approach in assessing the clonal relation of these isolates and managing their outbreaks. A total of 100 A. baumannii isolates were collected from immunocompromised patients hospitalized in the intensive care unit (ICU) of a hospital in Zanjan City, Iran. Their antibiotic resistance ability (especially aminoglycoside resistance) was studied by disc diffusion tests. The genetic typing of A. baumannii was studied using ERIC-PCR and MLVA methods. All isolates were resistant to 3 or more antibiotics and regarded as multidrug-resistant (MDR). Additionally, 32% of the isolates were resistant to all antibiotics tested, and 91% were extensively drug-resistant (XDR). The increased rate of aminoglycoside-resistant A. baumannii in ICU patients, with an increased incidence of aminoglycoside-modifying enzymes of aac (6')-Ib, ant (3″)-I, and aph (2″)-Id. ERIC-PCR has likewise shown an increased level of diversity in A. baumannii isolates. According to the ERIC-PCR patterns, isolates were classified as 4 clusters, while according to the MLVA patterns, isolates were classified as 9 distinct clusters. ERIC-PCR and MLVA assays serve as useful genotyping methods to assess the genetic variety or clonal relatedness of A. baumannii isolates.

Quantitative and Qualitative Determination of Biofilm Formation Pattern in Multidrug Resistance Acinetobacter baumannii in Correlation with COVID-19 and Respiratory Infected Patients

Respiratory tract infection (RTI) is one of the triggering factors that cause severe and life-threatening health problems. Acinetobacter baumannii frequently causes nosocomial infections, especially in intensive care units (ICUs). Multidrug-resistant (MDR) A. baumannii encodes multiple virulence factors that contribute to chronic diseases, as well as antibiotic resistance; among them is the capacity to colonize and produce Biofilm on biotic and abiotic surfaces that is the primary source of worry in hospital environments. The study assessed the role of antibiotic resistance and biofilm formation patterns caused by MDR A. baumannii between isolates from COVID-19 and respiratory-infected patients in Baghdad Medical City hospitals and Teaching laboratories. This study included isolating and identifying A. baumannii from the sputum samples of respiratory tract-infected patients. (some of them infected with COVID-19) . Diagnosis of isolates was done by conventional cultural, microscopical and biochemical methods and confirmed by API 20E and VITEK2 system. Investigation of the susceptibility profile of the isolates against 18 types of antibiotics was tested, and the determination of A. baumannii biofilm formation was recorded by qualitative and quantitative methods. Results showed that 36 bacterial isolates were identified as A. baumannii. Most isolates were resistant to antibiotics, including all penicillins and cephalosporins (including inhibitor combinations), fluoroquinolones and aminoglycosides, followed by carbapenems antibiotics. In contrast, all isolates were susceptible to colistin (94.4%), followed by minocycline (36.1%), and the proportions of MDR, XDR, and PDR were 19.4%, 77.8 %, and 2.8 %, respectively. All isolates of A. baumannii showed biofilm formation (100%) by Quantitative method(MTP) and 91.6%. By the qualitative approach, we can conclude that there were no significant changes in biofilm values after 48 hours between groups with and without COVID-19 infection. However, there was a significant difference in adherence levels of bacteria between COVID-19 groups, with a higher proportion of solid adherence in the COVID-19 group compared to moderate adherence in the COVID-19-free group patients. Keywords: Acinetobacter baumannii, Antibiotic Susceptibility, Biofilm formation patterns, COVID-19 and respiratory infected patients.

Carbapenemase-Encoding Genes in MDR Acinetobacter baumannii Isolated from ICUs and Surgical Wards in Minya, Egypt

Carbapenemase-Encoding Genes in MDR Acinetobacter baumannii Isolated from ICUs and Surgical Wards in Minya, Egypt

Harnessing the Native Type I-F CRISPR-Cas System of Acinetobacter baumannii for Genome Editing and Gene Repression

The rapid emergence of infections caused by MDR Acinetobacter baumannii poses a serious threat to global public health. Therefore, it has become important to obtain a deeper understanding of the mechanisms of multidrug resistance and pathogenesis of A. baumannii. However, there are still relatively few genetic engineering tools for A. baumannii. Although A. baumannii possesses Type I-F CRISPR-Cas systems, they have not yet been used for genetic modifications. Here, we developed a single plasmid-mediated native Type I-F CRISPR-Cas system for gene editing and gene regulation in A. baumannii. The protospacer adjacent motif (PAM) sequence was identified as 5'-NCC-3' by analysis of the CRISPR array. Through introduction of the RecAb homologous recombination system, we significantly increased the knockout efficiency of the oxyR gene from 12.5% to 75.0% in A. baumannii. To investigate transcriptional inhibition by the Type I-F CRISPR system, we deleted the gene encoding its Cas2-3 nuclease and repurposed the native Type I-F Cascade effector to regulate transcription of alcohol dehydrogenase gene adh4. The level of adh4 transcription was inhibited by up to 900-fold compared to the control. The Cascade transcriptional module was also successfully applied in a clinical Klebsiella pneumoniae isolate. This study proposed a tool for future exploration of the genetic characteristics of A. baumannii or other clinical strains.

Genome characterization of the novel lytic phage vB_AbaAut_ChT04 and the antimicrobial activity of its lysin peptide against Acinetobacter baumannii isolates from different time periods.

Acinetobacter baumannii is an important opportunistic pathogen, usually associated with immunocompromised individuals with a prolonged period of stay in a hospital. Currently, the incidence of multi-drug resistant A. baumannii (MDR-AB) and extensively drug-resistant A. baumannii (XDR-AB) is increasing rapidly in Thailand, mirroring the trend worldwide. Novel therapeutic approaches for the treatment of A. baumannii infection using bacteriophages are being evaluated, and the use of phage-derived peptides is being tested as alternative approach to fighting infection. In this study, we isolated and determined the biological features of a lytic A. baumannii phage called vB_AbaAut_ChT04 (vChT04). The vChT04 phage was classified as a member of the family Autographiviridae of the class Caudoviricetes. It showed a short latent period (10 min) and a large burst size (280 PFU cell-1), and it was able to infect 52 out of 150 clinical MDR-AB strains tested (34.67%). Most of the phage-sensitive strains were A. baumannii strains that had been isolated during the same year that the phage was isolated. The phage showed activity across a broad pH (pH 5.0-8.0) and temperature (4-37°C) range. Whole-genome analysis revealed that the vChT04 genome comprises 41,158 bp with a 39.3% GC content and contains 48 open reading frames (ORFs), 28 of which were assigned putative functions based on homology to previously identified phage genes. Comparative genomic analysis demonstrated that vChT04 had the highest similarity to phage vB_AbaP_WU2001, which was isolated in the southern part of Thailand. An endolysin gene found in the vChT04 genome was used to synthesize an antimicrobial peptide (designated as PLysChT04) and its antimicrobial activity was evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. The MIC and MBC values of peptide PLysChT04 against MDR-AB and XDR-AB were 312.5-625 µg/mL, and it was able to inhibit both phage-susceptible and phage-resistant isolates collected over different time periods. PLysChT04 showed good efficacy in killing drug-resistant A. baumannii and other bacterial strains, and it is a promising candidate for development as an alternative therapeutic agent targeting A. baumannii infections.

Computationally Designed AMPs with Antibacterial and Antibiofilm Activity against MDR Acinetobacter baumannii.

The discovery of new antimicrobials is necessary to combat multidrug-resistant (MDR) bacteria, especially those that infect wounds and form prodigious biofilms, such as Acinetobacter baumannii. Antimicrobial peptides (AMPs) are a promising class of new therapeutics against drug-resistant bacteria, including gram-negatives. Here, we utilized a computational AMP design strategy combining database filtering technology plus positional analysis to design a series of novel peptides, named HRZN, designed to be active against A. baumannii. All of the HRZN peptides we synthesized exhibited antimicrobial activity against three MDR A. baumannii strains with HRZN-15 being the most active (MIC 4 µg/mL). This peptide also inhibited and eradicated biofilm of A. baumannii strain AB5075 at 8 and 16 µg/mL, which is highly effective. HRZN-15 permeabilized and depolarized the membrane of AB5075 rapidly, as demonstrated by the killing kinetics. HRZN 13 and 14 peptides had little to no hemolysis activity against human red blood cells, whereas HRZN-15, -16, and -17 peptides demonstrated more significant hemolytic activity. HRZN-15 also demonstrated toxicity to waxworms. Further modification of HRZN-15 could result in a new peptide with an improved toxicity profile. Overall, we successfully designed a set of new AMPs that demonstrated activity against MDR A. baumannii using a computational approach.

Emerging multidrug resistant Acinetobacter baumannii among patients in intensive care unit: an implication for extended global threat

Emerging multidrug resistant Acinetobacter baumannii among patients in intensive care unit: an implication for extended global threat

Analysis of tigecycline in the cerebrospinal fluidand serum of patients with Acinetobacter baumannii central nervous system infection.

Aim: This study aimed to establish a method to determine tigecycline (TGC) in the cerebrospinal fluid (CSF) and serum of 12 patients with multidrug-resistant Acinetobacter baumannii (MDRAB) central nervous system infection (CNSI) and evaluate the correlation of TGC in CSF and serum samples. Materials & methods: TGC in CSF and serum was detected by high-performanceliquid chromatography with tandem mass spectrometry. Results: In all12 patients, the CSF-to-serum ratio of TGC at asteady-state trough concentration ranged from 21.46to 44.46%, and the mean value was 31.61±8.13%. The correlation of TGC in CSF and serum was 0.5065. Conclusion: CNSI might have no potential to increase the penetration ability of TGC into theCSF. The correlation between the concentrations of TGC in CSF and serum at steady state was demonstrated to be positive.

Enhanced immunoprotection against Acinetobacter baumannii infection: Synergistic effects of Bap and BauA in a murine model

BackgroundThe rise of multi-drug resistant Acinetobacter baumannii poses a grave threat to hospital settings, resulting in increased mortality rates and garnering global attention. The formation of biofilms facilitated by biofilm-associated protein (Bap) and the iron absorption capabilities mediated by Baumannii acinetobactin utilization A (BauA) contribute to the persistence and survival of multidrug-resistant strains. In this study, we aimed to investigate the potential of disrupting the function of BauA and Bap simultaneously as a strategy for controlling A. baumannii. MethodsRecombinant Bap and BauA were expressed, purified, and subcutaneously administered individually and in combination to BALB/c mice. Subsequently, mice were intraperitoneally challenged with A. baumannii, and the bacterial load and tissue damage in the spleen, lung, and liver were assessed. Serum samples were evaluated to determine antibody titers in surviving mice. ResultsSpecific IgG antibodies were significantly increased. A combination of the antigens resulted in enhanced titer of specific IgGs in comparison to either BauA or Bap alone. The antibodies remained stable over a seven-month period. The combination of Bap and BauA exhibited superior immunoprotection against A. baumannii infection compared to individual administration, resulting in a further reduction in bacterial load in the liver, spleen, and lungs. The histopathological analysis demonstrated successful protection of the tissues against A. baumannii-induced damage upon administration of the two immunogens. ConclusionsThe combination of Bap and BauA has the potential to target a broader range of A. baumannii strains, including those expressing either Bap or BauA, thereby increasing its efficacy against a diverse array of strains.