Case report: Successful treatment of OXA-23 Acinetobacter baumannii neurosurgical infection and meningitis with sulbactam-durlobactam combination therapy.

Meningitis caused by Acinetobacter species is a rare complication of neurosurgical procedures, although it is associated with high morbidity and mortality. Carbapenem-resistant Acinetobacter is particularly difficult to treat, considering the limited selection and tolerability of effective antimicrobials. Sulbactam-durlobactam was approved by the FDA in 2023 for treatment of hospital-acquired and ventilator-associated pneumonia due to susceptible strains of Acinetobacter, including carbapenem-resistant Acinetobacter baumannii. Here, we present a case of carbapenem-resistant Acinetobacter baumannii neurosurgical infection and meningitis successfully treated with sulbactam-durlobactam combination therapy.

Polydopamine-based nano adjuvant as a promising vaccine carrier induces significant immune responses against Acinetobacter baumannii-associated pneumonia.

The objective of this study was to assess the effectiveness of polydopamine nanoparticles (PDANPs) as a delivery system for intranasal antigen administration to prevent Acinetobacter baumannii (A. baumannii)-associated pneumonia. In the in vitro phase, the conserved outer membrane protein 22 (Omp22)-encoding gene of A. baumannii was cloned, expressed, and purified, resulting in the production of recombinant Omp22 (rOmp22), which was verified using western blot. PDANPs were synthesized using dopamine monomers and loaded with rOmp22 through physical adsorption. The rOmp22-loaded PDANPs were characterized in terms of size, size distribution, zeta potential, field emission scanning electron microscopy (FESEM), loading capacity, Fourier transform infrared spectroscopy (FTIR), release profile, and cytotoxicity. In the in vivo phase, the adjuvant effect of rOmp22-loaded PDANPs was evaluated in terms of eliciting immune responses, including humoral and cytokine levels (IL-4, IL-17, and IFN-γ), as well as protection challenge. The rOmp22-loaded PDANPs were spherical with a size of 205 nm, a zeta potential of -14 mV, and a loading capacity of approximately 35.7 %. The released rOmp22 from nontoxic rOmp22-loaded PDANPs over 20 days was approximately 41.5 %, with preserved rOmp22 integrity. The IgG2a/IgG1 ratio and IFN-γ levels were significantly higher in immunized mice with rOmp22-loaded-PDANPs than in rOmp22-alum, naive Omp22, and control groups. Furthermore, rOmp22-loaded PDANPs induced effective protection against infection in the experimental challenge and showed more normal structures in the lung histopathology assay. The results of this study suggest the potential of PDANPs as a nano-adjuvant for inducing strong immune responses to combat A. baumannii.

Colistin resistance in carbapenem non-susceptible Acinetobacter baumanii in a tertiary care hospital in India: clinical characteristics, antibiotic susceptibility and molecular characterization.

INTRODUCTION: Acinetobacter baumanii (AB) is a bacterium of concern in the hospital setup due to its ability to thrive in unfavorable conditions and the rapid emergence of antibiotic resistance. Carbapenem resistance in this organism is disheartening, further clouded by the emergence of colistin resistance. AIM: The present prospective study aims to note the epidemiology, molecular profile, and clinical outcome of patients with colistin resistance AB infections in a multispecialty tertiary care setup in Odisha, Eastern India. METHODS: All AB strains received from March 2021 to February 2022, identified by Vitek2 (Biomerieux) and confirmed by oxa-51 genes, were included. Carbapenem and colistin resistance were identified as per CLSI guidelines. Known mutations for blaOXA-23-like, blaIMP, blaVIM, blaKP, lpxA, lpxC, pmrA, pmrB, and plasmid mediated mcr (mcr1-5) were screened by conventional PCR techniques. The clinical outcome was noted retrospectively from case sheets. Data was entered in MS Excel and tabulated using SPSS software. RESULTS: In the study period, 350 AB were obtained, of which 317(90.5%) were carbapenem resistant (CRAB). Among the CRAB isolates, 19 (5.9%) were colistin resistant (ABCoR). The most valuable antibiotics in the study were tigecycline (65.4% in ABCoI; 31.6% in ABCoR) and minocycline (44.3% in CI; 36.8% in CR). There was a significant difference in mortality among ABCoI and ABCoR infections. bla OXA was the predominant carbapenem resistance genotype, while pmrA was the predominant colistin resistant genotype. There were no plasmid mediated mcr genes detected in the present study.

Risk factors for transmission of carbapenem-resistant Acinetobacter baumannii in outbreak situations: results of a case-control study.

BACKGROUND: An increase in patients with multidrug-resistant organisms and associated outbreaks during the COVID-19 pandemic have been reported in various settings, including low-endemic settings. Here, we report three distinct carbapenem-resistant Acinetobacter baumannii (CRAB) outbreaks in five intensive care units of a university hospital in Berlin, Germany during the COVID-19 pandemic. METHODS: A case-control study was conducted with the objective of identifying risk factors for CRAB acquisition in outbreak situations. Data utilized for the case-control study came from the investigation of three separate CRAB outbreaks during the COVID-19 pandemic (August 2020- March 2021). Cases were defined as outbreak patients with hospital-acquired CRAB. Controls did not have any CRAB positive microbiological findings and were hospitalized at the same ward and for a similar duration as the respective case. Control patients were matched retrospectively in a 2:1 ratio. Parameters routinely collected in the context of outbreak management and data obtained retrospectively specifically for the case-control study were included in the analysis. To analyze risk factors for CRAB acquisition, univariable and multivariable analyses to calculate odds ratios (OR) and 95% confidence intervals (CI) were performed using a conditional logistic regression model. RESULTS: The outbreaks contained 26 cases with hospital-acquired CRAB in five different intensive care units. Two exposures were identified to be independent risk factors for nosocomial CRAB acquisition by the multivariable regression analysis: Sharing a patient room with a CRAB patient before availability of the microbiological result was associated with a more than tenfold increase in the risk of nosocomial CRAB acquisition (OR: 10.7, CI: 2.3-50.9), while undergoing bronchoscopy increased the risk more than six times (OR: 6.9, CI: 1.3-38.1). CONCLUSIONS: The risk factors identified, sharing a patient room with a CRAB patient and undergoing bronchoscopy, could point to an underperformance of basic infection control measure, particularly hand hygiene compliance and handling of medical devices. Both findings reinforce the need for continued promotion of infection control measures. Given that the outbreaks occurred in the first year of the COVID-19 pandemic, our study serves as a reminder that a heightened focus on airborne precautions should not lead to a neglect of other transmission-based precautions.

Catheter-Associated Vancomycin-Resistant Enterococcus faecium Ventriculitis and Multidrug-Resistant Acinetobacter baumannii Pneumonia With Subsequent Acinetobacter Ventriculitis: A Case Report.

Ventriculitis is associated with cerebrospinal fluid (CSF) shunts, and rare microorganisms associated with infection include vancomycin-resistant Enterococcus (VRE) faecium and Acinetobacter baumannii. Both organisms are known to cause nosocomial infections, and the emergence of multidrug-resistant (MDR) strains presents a treatment challenge. There is a lack of consensus on antimicrobial agent selection for ventriculitis involving VRE faecium or MDR A. baumannii, which are life-threatening conditions. We present a case of a 59-year-old male presenting with CSF catheter-associated VRE faecium ventriculitis and MDR A. baumannii pneumonia who subsequently developed a nosocomial MDR A. baumannii ventriculitis. Both instances of ventriculitis were successfully treated with combination antibiotic therapy. VRE faecium ventriculitis was successfully treated with linezolid and intrathecal daptomycin. While daptomycin is not approved for Enterococcal infections, the synergistic effect of daptomycin in combination with linezolid proved effective. Although the MDR A. baumannii pneumonia was not cured with cefiderocol monotherapy, the MDR A. baumannii ventriculitis was successfully treated with combination therapy including cefiderocol, ampicillin/sulbactam, and intrathecal colistin. This highlights life-saving combination antibiotic therapies for ventriculitis caused by multiple rare and drug-resistant microorganisms.

Risk factors and outcome associated with coinfection with carbapenem-resistant Klebsiella pneumoniae and carbapenem-resistant Pseudomonas aeruginosa or Acinetobacter baumanii: a descriptive analysis.

Background: Nearly 30% of patients infected with carbapenem-resistant Klebsiella pneumoniae (CRKP) were previously shown to be coinfected with carbapenem-resistant Pseudomonas aeruginosa (CRPA) or Acinetobacter baumannii (CRAB). Infections caused by multiple carbapenem-resistant pathogens present significant challenge to infection control and therapeutic management. The study objective was to identify risk factors for acquisition of multiple carbapenem-resistant pathogens and associated outcomes. Methods: A descriptive analysis of adults infected with either CRKP alone or coinfected with CRPA or CRAB was performed. Patient groups were compared on demographics, clinical characteristics, treatment, and outcome. Results: 86 patients with CRKP monoinfection and 60 patients with coinfections were evaluated. Respiratory tract was the predominant infection site for coinfected patients involving mostly CRPA whereas urinary tract was the primary site for CRKP-only group. More coinfected patients were severely debilitated, had prior carbapenem exposure (37% vs 13%, p<0.001) and history of pneumonia in the past year (67% vs 41%, p<0.01). More coinfected patients required direct ICU admission (45% vs 27%, p=0.02) and had prolonged length of stay (median 15 vs 10 days, p<0.01) than the CRKP-only group but mortality rates (18% vs 16%) were similar. Conclusions: CRKP coinfection with another carbapenem-resistant pathogen adds significant morbidity and healthcare burden overall. Empiric therapy with reliable activity against both CRKP and carbapenem-resistant Pseudomonas aeruginosa may be prudent for at risk patients with pneumonia.

Prediction of Antigenic Vaccine Peptide Candidates From BfmRS Associated With Biofilm Formation in Acinetobacter baumannii.

INTRODUCTION:  A. baumannii is categorized as a priority pathogen due to its propensity for multi-drug resistance, exhibiting resistance against the last resort of antibiotics. It is also considered a potent nosocomial pathogen, so targeting the microbe using novel strategies would be the need of the hour. In this context, the in-silico computational approach would serve the best to design the possible epitope peptides, which may be further considered for the experimental trials for their immunological response.  Objective: To predict the immune-dominant epitope peptide candidates against the bfmR and bfmS proteins mediating the two-component system adaptation in the formation of biofilm in A. baumannii. MATERIALS AND METHODS: 11 different FASTA sequences of bfmR and bfmS from A. baumannii strains retrieved based on the blast-p similarity search tool were subjected to linear epitope B-cell epitope predictions under the IEDB B-cell epitope prediction server. Further analysis on antigenicity, allergenicity, and toxigenicity was achieved using the AntigenPro, Vaxijen, and AlgPred tools, with the physical and chemical properties evaluated using the Expasy Protparam server. Selection of the immunodominant peptides for T-cells was done through the databases under IEDB. The final assessment of protein-TLR2 interactions was done by MHC cluster servers. RESULTS: Four peptide sequences (E1-E4) were predicted for B-cell dominance, with E1, E2, and E4 as probable antigens. All were soluble and non-toxigenic. E1 and E3 were considered non-allergens. GRAVY values were negative for all the peptides, indicating the protein to be hydrophilic in nature. Analysis of the T-cell epitopes was promising, with 100% conservancy for class-I HLA alleles, high interaction scores for similarity with TLR2, and more hydrogen bonds for E2, followed by other epitope peptides. CONCLUSION: The promising four epitopes, as predicted for bfmR and bfmS in the present study, suggest their potent role as possible candidates for the design of vaccines targeting the TCS of A. baumannii, recommending further in vitro and in vivo experimental validation.

Acinetobacter baumannii Early-Onset Sepsis After Home Delivery Into Toilet Water.

Early-onset sepsis (EOS) is an important cause of morbidity and mortality in newborns, usually caused by pathogens acquired intrapartum. We present the case of a term neonate born by home delivery in the toilet, after an unsupervised pregnancy. He developed a culture-proven early-onset sepsis caused by Acinetobacter baumannii. This was the first case of neonatal sepsis by this pathogen in our unit. The microorganism was susceptible to all antibiotics tested. The neonate was treated empirically with ampicillin and cefotaxime and completed 21 days of directed therapy with meropenem, as meningitis could not be excluded. During the clinical course, the newborn developed severe and persistent thrombocytopenia and neutropenia. In this report, we discuss the etiology behind this clinical presentation. We intend to raise awareness for the consideration of Acinetobacter baumannii as a potential pathogen in EOS, particularly in the presence of adverse birth circumstances.

Analysis of Pathogens of Urinary Tract Infections Associated with Indwelling Double-J Stents and Their Susceptibility to Globularia alypum.

Ureteral double-J stents are frequently used to prevent urinary obstruction. They can develop bacterial colonization and encrustation, which leads to persistent infections that seldom respond to antibiotic treatment. Thus, the goal of this study was to evaluate the local spectrum of bacterial pathogens and their susceptibility to natural compounds. A total of 59 double-J ureteral stents from 59 consecutive patients were examined. The samples were inoculated on agar culture mediums. Extracts of Globularia alypum L. were evaluated for their antibacterial activity with the diffusion and broth dilution methods; for antibiofilm activity, the crystal violet assay was used. The identification and the quantification of the different constituents of extracts were determined by reverse-phase high-performance liquid chromatography (RP-HPLC). Bacterial growth was found in three patients (5.1%). Enterococcus faecalis (1.7%), Acinetobacter baumanii (1.7%), and Pseudomonas putida (1.7%) strains were more commonly detected. They were resistant to several common antibiotics. All extracts presented several components, mainly nepetin-7-glucoside and trans-ferulic-acid, and they had antibacterial activity (MIC = 6.25 mg/mL and MBC = 6.25 mg/mL), and antibiofilm (59.70% at 25 mg/mL) properties, especially against Acinetobacter baumanii. The results achieved confirm the important role of this plant as a source of therapeutic activities.

Assesment of polyphenolic compounds against biofilms produced by clinical Acinetobacter baumannii strains using in silico and in vitro models.

Several types of microbial infections are caused by Acinetobacter baumanii that has developed resistance to antimicrobial agents. We therefore investigated the role of plant polyphenols against A. baumannii using in silico and in vitro models. The clinical strains of A. baumannii were investigated for determination of resistance pattern and resistance mechanisms including efflux pump, extended spectrum beta lactamase, phenotype detection of AmpC production, and Metallo-ß-lactamase. The polyphenolic compounds were docked against transcription regulator BfmR (PDB ID 6BR7) and antimicrobial, antibiofilm, and anti-quorum sensing activities were performed. The antibiogram studies showed that all isolated strains were resistant. Strain A77 was positive in Metallo-ß-lactamase production. Similarly, none of strains were producers of AmpC, however, A77, A76, A75 had active efflux pumps. Molecular docking studies confirmed a strong binding affinity of Rutin and Catechin towards transcription regulator 6BR7. A significant antimicrobial activity was recorded in case of quercetin and syringic acid (MIC 3.1 µg/mL) followed by vanillic acid and caffeic acid (MIC 12.5 µg/mL). All tested compounds presented a strong antibiofilm activity against A. baumanii strain A77 (65 to 90%). It was concluded that all tested polyphenols samples posess antimicrobial and antibiofilm activities, and hence they may be utilized to treat multidrug resistance A. baumannii infections.

Antimicrobial activity of photosensitizers: arrangement in bacterial membrane matters.

Porphyrins are well-known photosensitizers (PSs) for antibacterial photodynamic therapy (aPDT), which is still an underestimated antibiotic-free method to kill bacteria, viruses, and fungi. In the present work, we developed a comprehensive tool for predicting the structure and assessment of the photodynamic efficacy of PS molecules for their application in aPDT. We checked it on a series of water-soluble phosphorus(V) porphyrin molecules with OH or ethoxy axial ligands and phenyl/pyridyl peripheral substituents. First, we used biophysical approaches to show the effect of PSs on membrane structure and their photodynamic activity in the lipid environment. Second, we developed a force field for studying phosphorus(V) porphyrins and performed all-atom molecular dynamics simulations of their interactions with bacterial lipid membranes. Finally, we obtained the structure-activity relationship for the antimicrobial activity of PSs and tested our predictions on two models of Gram-negative bacteria, Escherichia coli and Acinetobacter baumannii. Our approach allowed us to propose a new PS molecule, whose MIC50 values after an extremely low light dose of 5 J/cm2 (5.0 ± 0.4 µg/mL for E. coli and 4.9 ± 0.8 µg/mL for A. baumannii) exceeded those for common antibiotics, making it a prospective antimicrobial agent.

Apolipoprotein E mimetic peptide COG1410 combats pandrug-resistant Acinetobacter baumannii.

The emergence of pandrug-resistant bacteria breaks through the last line of defense and raises fear among people of incurable infections. In the post-antibiotic era, the pharmaceutical field turns to seek non-conventional anti-infective agents. Antimicrobial peptides are considered a prospective solution to the crisis of antimicrobial resistance. In this study, we evaluated the antimicrobial efficiency of an ApoE mimetic peptide, COG1410, which has been confirmed to exhibit strong neural protective activity and immunomodulatory function. COG1410 showed potent antimicrobial activity against pandrug-resistant Acinetobacter baumannii, even eliminating large inocula (108 CFU/ml) within 30 min. LC99.9 in PBS and 50% pooled human plasma was 2 µg/ml (1.4 µM) and 8 µg/ml (5.6 µM), respectively. Moreover, COG1410 exhibited biofilm inhibition and eradication activity, excellent stability in human plasma, and a low propensity to induce resistance. Although COG1410 easily entered bacterial cytoplasm and bound to DNA nonspecifically, the major mechanism of COG1410 killing was to disrupt the integrity of cell membrane and lead to leakage of cytoplasmic contents, without causing obvious pores on the cell surface or cell lysis. Additionally, transcriptome analysis showed that treatment with COG1410-enriched genes involved a series of oxidation-reduction processes. DCFH-DA probe detected an increased ROS level in the presence of COG1410, indicating ROS was another hit of this AMP. Furthermore, the action of COG1410 did not depend on the electronic interaction with the LPS layer, in contrast to polymyxin B. The strong synergistic interaction between COG1410 and polymyxin B dramatically reduced the working concentration of COG1410, expanding the safety window of the application. C. elegans infection model showed that combined therapy of COG1410 and polymyxin B was capable of significantly rescuing the infected nematodes. Taken together, our study demonstrates that COG1410 is a promising drug candidate in the battle against pandrug-resistant A. baumannii.

Extensively Drug-Resistant Acinetobacter baumannii Nosocomial Pneumonia Successfully Treated with a Novel Antibiotic Combination.

Extremely drug-resistant (XDR) Acinetobacter baumannii causes challenging nosocomial infections. We report the case of a patient with XDR A. baumannii pneumonia and septic shock successfully treated with cefiderocol and a novel antibiotic obtained via expanded access protocol. With focused research and drug development efforts, the poor outcomes associated with these infections may be mitigated.

Microbial etiologies of ventilator-associated pneumonia (VAP) in intensive care unit of Beni-Suef University's Hospital.

BACKGROUND: Ventilator-associated pneumonia (VAP) is a major health problem for people intubated in intensive care units (ICUs), leading to increased mortality rates, hospital stay, and treatment costs. In the present study, the core pathogens causing VAP in Beni-Suef University's Hospital, Egypt, was investigated over a study period of 2 years (2017-2019). RESULTS: Of a total of 213 patients subjected to mechanical ventilation, 60 have developed VAP during their stay in the ICU. The mortality rate reached 41.7% among VAP patients. Sixty bacteria were isolated from an endotracheal aspirate of hospitalized patients. The different isolates were cultured followed by running biochemical tests, sensitivity assays, and automated VITEK®2 System analysis. Unexpectedly, all the isolates were Gram-negative bacteria. Klebsiella pneumoniae were the main pathogen encountered (27/60 isolates) followed by Acientobacter baumannnii (7/60) and other microorganisms belonging to the genera Moraxella, Escherichia, and Pseudomonas (11/60). Antibiotic sensitivity testing was performed via the VITEK®2 System using up to 16 different antibiotics representing 8 different antibiotic classes and subclasses (aminoglycosides, carbapenems, fluoroquinolones, penicillin/ß-lactamase inhibitor, extended-spectrum cephalosporins, aminopenicillins, aminopenicillins/ß-lactamase inhibitor, folic acid synthesis inhibitor). Majority of the isolates (28/60) showed a remarkable extensive drug resistance (XDR) pattern, while 15 isolates were multi-drug resistant (MDR) and only 6 were pan-drug resistant (PDR) with regard to antibiotics under evaluation. CONCLUSION: The association of VAP with multi-drug-resistant bacteria is alarming, and rapid management is crucial. Identification of core pathogens is essential for identifying the most appropriate technique for infection control.

Bloodstream infection with Acinetobacter baumanii in a Plasmodium falciparum positive infant: a case report.

BACKGROUND: The increasing incidence of multi-antibiotic-resistant bacterial infections, coupled with the risk of co-infections in malaria-endemic regions, complicates accurate diagnosis and prolongs hospitalization, thereby increasing the total cost of illness. Further, there are challenges in making the correct choice of antibiotic treatment and duration, precipitated by a lack of access to microbial culture facilities in many hospitals in Ghana. The aim of this case report is to highlight the need for blood cultures or alternative rapid tests to be performed routinely in malaria patients, to diagnose co-infections with bacteria, especially when symptoms persist after antimalarial treatment. CASE PRESENTATION: A 6-month old black female child presented to the Agogo Presbyterian Hospital with fever, diarrhea, and a 3-day history of cough. A rapid diagnostic test for malaria and Malaria microscopy was positive for P. falciparum with a parasitemia of 224 parasites/µl. The patient was treated with Intravenous Artesunate, parental antibiotics (cefuroxime and gentamicin) and oral dispersible zinc tablets in addition to intravenous fluids. Blood culture yielded Acinetobacter baumanii, which was resistant to all of the third-generation antibiotics included in the susceptibility test conducted, but sensitive to ciprofloxacin and gentamicin. After augmenting treatment with intravenous ciprofloxacin, all symptoms resolved. CONCLUSION: Even though this study cannot confirm whether the bacterial infection was nosocomial or otherwise, the case highlights the necessity to test malaria patients for possible co-infections, especially when fever persists after parasites have been cleared from the bloodstream. Bacterial blood cultures and antimicrobial susceptibility testing should be routinely performed to guide treatment options for febril illnesses in Ghana in order to reduce inappropriate use of broad-spectrum antibiotics and limit the development of antimicrobial resistance.

The novel outer membrane protein from OprD/Occ family is associated with hypervirulence of carbapenem resistant Acinetobacter baumannii ST2/KL22.

Acinetobacter baumannii has become a major healthcare threat that causes nosocomial infections, especially in critically ill patients. The spread of carbapenem-resistant A. baumannii (CRAB) strains has long been a clinical concern. It is important to study the epidemiology and virulence characteristics of different CRAB isolates in order to tailor infection prevention and antibiotic prescribing. In this study, a total of 71 CRAB isolates were collected in the hospital, and clinical characteristics of infections were analyzed. The genomic characteristics and phylogenetic relationships were elucidated based on genome sequencing and analysis. The isolates were assigned to three sequence types (STs, Pasteur) and nine capsular polysaccharide (KL) types, among which ST2/KL22 was the most prevalent CRAB in the hospital. Even though all the ST2/KL22 isolates contained the same reported virulence genes, one specific clade of ST2/KL22 showed more pathogenic in mouse infection model. Complete genomic analysis revealed differences at the oprD locus between the low- and high-virulent isolates. More specifically, a premature stop codon in the low-virulence strains resulted in truncated OprD expression. By evaluating pathogenicity in C57BL/6 J mice, knock-out of oprD in high-virulent isolate resulted in virulence attenuation, and complementing the avirulent strain with full-length oprD from high-virulent isolate enhanced virulence of the former. The oprD gene may be associated with the enhanced virulence of the specific ST2/KL22 clone, which provides a potential molecular marker for screening the hypervirulent A. baumannii strains.

Extensive drug resistant (XDR) Acinetobacter baumannii parappendicular-related infection in a hydrocephalus patient with ventriculoperitoneal shunt: a case report.

Ventricular infection due to XDR-Acinetobacter baumanii (A. baumanii) is the most severe complication after neurosurgery which associated with high morbidity and mortality. Managing A. baumanii ventriculitis/shunt infection and multiple brain abscesses is challenging since its nature that tends to be pandrug resistant to all antibiotics used. Thus, we present the first such case with problems in administration based on the available data.

Contribution of NDM and OXA-type carbapenemases to carbapenem resistance in clinical Acinetobacter baumannii from Nigeria.

Objective:Acinetobacter baumannii infections are rarely diagnosed in many hospitals in Nigeria due to a lack of capacity for the identification of the organism in spite of the clinical significance of this opportunistic nosocomial organism. We assembled a panel of presumptive isolates of A. baumannii from tertiary hospitals in Nigeria and analysed mechanisms of resistance phenotypically and by whole genome sequencing.Materials and methods: Twenty-one clinical isolates of A. baumannii identified using standard microbiological tests were tested for susceptibility to a panel of antibiotics by the agar dilution method, and production of ESBLs using phenotypic tests. Whole genome sequencing and comparative genomic analysis were used to determine the antimicrobial resistance genes, strain types, phylogenetic relationships and genetic context of resistance genes.Results: The MIC50 and MIC90 of most antibiotics were very high with no difference between MIC50 and MIC90 values apart for amikacin, meropenem and colistin where MIC50 and MIC90 ranged between 1-4 µg/ml and 64->64 µg/ml, respectively. Multiple resistance genes were detected in most of the isolates including blaNDM-1, various blaOXA-51 family alleles and blaOXA-23. Interestingly, blaNDM-1 carriage did not always result in phenotypic carbapenem resistance. Whole genome alignments typing showed strains belonged to three major clades. Strains within these clades had different resistance genes and resistance patterns.Conclusions: This report shows a high level of resistance to important antibiotics and carbapenem resistance in A. baumannii in Nigeria. We hope this work will serve as a reference for future study in the sub-Saharan region of Africa.

Conformational transition of Acinetobacter baumannii KdsC enzyme and the role of magnesium in binding: An insight from comparative molecular dynamics simulation and its implications in novel antibiotics design.

The 3-deoxy-d-manno-octulosonate 8-phosphate phosphatase (KdsC) catalyzes the hydrolysis of 3-deoxy-d-manno-octulosonate 8-phosphate (KDO 8-P) to 3-deoxy-d-manno-octulosonate (KDO) and inorganic phosphate in KDO biosynthesis pathway of Gram-negative bacteria lipopolysaccharide (LPS) hydrophobic lipid-A core. The essentiality of KDO for bacterial cell viability presents the possibility of its targeting to develop broad-spectrum antibacterial agents. In this study, a receptor based virtually screening method was put forward to identify novel lead inhibitory molecules for KdsC enzyme. Dynamics evaluation in solution revealed three complexes: Asinex-1197, Asinex-1705, and Asinex-1710 from Asinex antibacterial library as highly stable, involving conformational transition from open to close upon lead molecules binding and eloquent role of active pocket magnesium towards inhibitors binding and movements. Interconversion of local secondary structure elements in sequence region of Asp192-Asp208 covering motif ß-turn, ß-hairpin, and ß-sheets is seen recurrently that could be in all likelihood of the pressure excreted on this region during closing conformation event or magnesium driven inhibitor adjustments. The binding free energy estimation predicted gas phase energy for all the three complexes dominating with major contribution from van der Waals energy (in case of Asinex-1705 and Asinex-1710) and balanced contributions of both electrostatic and van der Waals (in case of Asinex-1197). Key residues-scanning shortlisted Leu45, Asp185, Gy188, Arg231, and Lys255 as vital in the interaction network of magnesium and inhibitors at the binding site. Their crucial roles in net binding energy were reaffirmed via in silico site directed alanine scanning method. The filtered hits might be useful to further scaffolds addition and structural optimization to yield high affinity binders of KdsC enzyme, whose inhibition, in turn, will disrupt the outer membrane synthesis.

In silico and in vitro studies of a number PILs as new antibacterials against MDR clinical isolate Acinetobacter baumannii.

QSAR analysis of a set of previously synthesized phosphonium ionic liquids (PILs) tested against Gram-negative multidrug-resistant clinical isolate Acinetobacter baumannii was done using the Online Chemical Modeling Environment (OCHEM). To overcome the problem of overfitting due to descriptor selection, fivefold cross-validation with variable selection in each step of the model development was applied. The predictive ability of the classification models was tested by cross-validation, giving balanced accuracies (BA) of 76%-82%. The validation of the models using an external test set proved that the models can be used to predict the activity of newly designed compounds with a reasonable accuracy within the applicability domain (BA = 83%-89%). The models were applied to screen a virtual chemical library with expected activity of compounds against MDR Acinetobacter baumannii. The eighteen most promising compounds were identified, synthesized, and tested. Biological testing of compounds was performed using the disk diffusion method in Mueller-Hinton agar. All tested molecules demonstrated high anti-A. baumannii activity and different toxicity levels. The developed classification SAR models are freely available online at http://ochem.eu/article/113921 and could be used by scientists for design of new more effective antibiotics.