Acinetobacter Baumannii Isolates Research Articles

Antibiofilm, Antidiabetic and Antioxidant Potentials of Vitis labrusca L. Skin Extracts

This study examined the antioxidant, antimicrobial, antibiofilm, and α-glucosidase inhibitory activities and the total phenolic and flavonoid contents of the different solvent (methanol, 50:50% methanol:water, and water) extracts from Vitis labrusca L. skin parts. The 50:50 methanol:water extract exhibited the highest antioxidant activity, exhibiting 153 µM TEAC and 0.0947 mg/mL SC50, as determined by the ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging assays, respectively. Additionally, the data demonstrated that the 50:50 methanol:water extract of the skin part of V. labrusca exhibited a higher total phenolic content, with 141 µg/mL GAE. The α-glucosidase enzyme activity of the 50:50% methanol:water extract (IC₅₀; 0.103 mg/mL) was observed to be higher than that of the other solvent extracts. The MIC values of the 50:50% methanol:water, water and methanol extracts of skin part of V. labrusca was determined as 12.5, 25 and 6.25 mg/mL, aganist to clinical antibiotic resistance Acinetobacter baumanii respectively. The results of this study indicate that the methanol, water and 50:50% methanol:water extracts were found to reduce the biofilm-forming capacity of the Acinetobacter baumannii isolate by approximately 1.7, 1.6 and 1.3-fold, respectively. The findings of our investigation suggest that skin parts of V. labrusca may serve as a promising candidate for the prevention and treatment of diseases associated with oxidative damage and bacterial infections. The results show that the components found in the waste skin extracts of these genotypes can be evaluated in terms of antioxidant, antidiabetic and antibacterial properties.

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

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

Investigation of EpsA, OmpA, and Bap Genes among MDR and XDR Acinetobacter baumannii Isolates in Khorramabad, Iran.

Acinetobacter baumannii is an opportunistic hospital pathogen with high antibiotic resistance, and the ability to produce biofilm. This study aimed to investigate epsA, ompA, and bap genes involved in biofilm formation in MDR and XDR clinical isolates of Acinetobacter baumannii in Khorramabad, Iran. In this study, 79 A. baumannii isolates were collected from various samples of the patients admitted to tertiary hospitals in Khorramabad city, Iran, between January and August 2019. After performing the semi-quantitative evaluation of biofilm production by microtiter plate assay, screening of isolates carrying epsA, ompA, and bap genes was done by PCR method. Finally, statistical analyses were conducted using SPSS 22. Among 79 A. baumannii isolates, 52% XDR, 40% MDR, and 16% non-XDRMDR isolates were found to be biofilm producers. All XDR and 94% MDR isolates had ompA and epsA genes, and bap genes were detected among > 80% of these isolates. Moreover, the presence of biofilm-related genes and biofilm production among non-XDRMDR isolates were less than among resistant isolates (p≤ 0.01). Based on the results, biofilm production and simultaneous presence of epsA, ompA, and bap genes among MDR, and XDR A. baumannii isolates have been found to be significantly more than non-XDR-MDR isolates.

Impact of EUCAST Rapid Antimicrobial Susceptibility Testing (RAST) on optimal antimicrobial therapy in gram-negative bloodstream infections

ObjectivesTo evaluate the possible impact of RAST on optimal antimicrobial therapy via de-escalation or escalation, and to determine the reduction in antibiotic susceptibility reporting time with RAST. MethodsIn this single-center, prospective descriptive study, RAST was performed on clinical blood cultures containing E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates. Very major error, major error, and categorical agreements with VITEK 2 were analyzed. ResultsOne hundred and three isolates were included in the study, out of which 29.1 % were carbapenem-resistant and 36.9 % were multidrug-resistant according to VITEK 2. Categorical agreement of the RAST method with standard antimicrobial susceptibility test (AST) was > 90 % at 6 h, except for piperacillin/tazobactam. Antibiotic revision could be carried out in 79.6 % of the patients either by de-escalation (61.2 %) or escalation (18.4 %) for optimal therapy based on the RAST 6 h result. RAST could provide carbapenem-sparing therapy in 24 % of patients. Reduction in antibiotic susceptibility reporting time was 41.5 h (38.8 to 63.2, median (IQR)). ConclusionsRAST can provide early antibiotic revision in a majority of patients with significantly reduced antibiotic susceptibility reporting time. Six hours is the shortest optimal time for antibiotic revision with RAST. In countries where empirical broad-spectrum antibiotics are prevalent due to high antibiotic resistance pressure, RAST should be proposed primarily in de-escalation and carbapenem-sparing strategies.

Phenotypic and molecular characterization of carbapenem-resistant Acinetobacter baumannii isolates from ventilator associated pneumonia patients

Phenotypic and molecular characterization of carbapenem-resistant Acinetobacter baumannii isolates from ventilator associated pneumonia patients

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

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

Isolation and Diagnosis of Acinetobacter baumannii Isolates from Patients with Meningitis in Child Protection Hospital in Baghdad

Environmental contamination has been estimated to account for up to 20% of all hospital-acquired illnesses. Acinetobacter baumannii has recently become the predominant pathogen, posing a significant risk to human health. In present study, two hundred fifteen CSF samples were collected from children between the ages of new born to 14 years who were visiting child protection hospital in Baghdad. For the period from first of Oct 2023 to the end of Jan 2024, and the samples were sent for diagnosis. Isolates were identified after culturing them on MacConkey agar, blood agar, and mannitol salt agar. A number of biochemical tests were performed to detect Acinetobacter baumannii bacteria. The results indicated a negative oxidase reaction, a positive catalase reaction, a negative indole reaction, a negative methyl red reaction, a negative Voges-Proskauer reaction, and a positive citrate reaction, which were performed for the samples and for final diagnosis the Vitek-2 Compact system was used. After cultivation and diagnosis, 7 isolates of Acinetobacter baumannii were obtained out of 40 samples that showed positive culture results with bacterial growth.

The activity of silver nanoparticles produced by Aerococcus spp. against some Acinetobacter baumannii isolates

Nanoparticles are among the fine materials that have an important role in many medical and health sciences such as medicine, biology, physics, chemistry and others. The purpose of this study was to create silver nanoparticles from Aerococcus spp. then used it against isolates of Acinetobacter baumannii. The method included growing Aerococcus spp in a culture medium. Silver nanoparticles were created when the color of medium changed to brown. Some structural properties of these materials were measured using TEM, FTIR, UV-Vis and XRD to characterize the AgNPs. The results showed the ability of Aerococcus spp to produce silver nanoparticles after adding alkaline silver nitrate solution to the culture medium and then the color change occurred. The biochemical tests showed the ability of bacteria; silver nanoparticles (NPs AgNO3) to absorb ultraviolet radiation at 200 nm. X-ray diffraction test showed that these nanoparticles formed radial peaks of 200, 202 and 311 at a wavelength of 25.94 nm depending on the crystalline state of the particles. The Scanning electron microscope test also showed these nanoparticles forming spherical nanoparticles at size of 32.78 nm. The Ag NPS antibacterial activity shows the ability of these nanoparticles at concentration 250μg/ml against inhibition of the growth of some A. baumannii isolates with an inhibition diameter of 30.32. Finally, the antibiofilm forming test showed the ability of Aerococcus spp. (NPs AgNO3) to reduce biofilm forming of A. baumannii at 100%.

Evaluation of the antibacterial activity of AgNPs from Lactobacillus plantarum against Acinetobacter baumannii

In this study, we isolated Acinetobacter baumannii in wounds and burn infections and assessed the impact of silver nanoparticles (AgNPs) produced from an external extract of Lactobacillus plantarum secretion on the bacterial growth. Characterization of AgNPs was done using TEM, XRD and FTIR spectroscopy. Inhibition diameters of five concentrations of AgNPs were prepared from Lactobacillus plantarum extracts against A. baumannii. A diameter of 20mm was observed for the highest concentration of 500mg\ml while 16 mm was observed for a concentration of 250mg\ml and 8 mm for the lowest concentration of 50mg\ml. The highest concentration of 500mg\ml showed the most significant inhibition. All concentrations of AgNPs were effective in inhibiting the growth of A. baumannii.

Unravelling Virulence Activities of Hospital Isolated Acinetobacter baumannii: Exploring The Prospective Application of Aspirin as an Antivirulence Agent

Acinetobacter baumannii infections pose a global public health threat due to the increasing resistance to various antimicrobial agents. This study reports the virulence characteristics of A. baumannii strains isolated from patients at Hospital Canselor Tuanku Muhriz UKM (HCTM) and explores the potential of aspirin as an antivirulence agent. Fourteen A. baumannii isolates from various infection sites exhibited resistance to at least two antibiotics. Among them, 43% (n=6) displayed high motility, correlating with the site of isolation. Additionally, 58% (n=7) formed strong biofilms, 36% (n=5) secreted proteases and 36% (n=5) resisted oxidative stress. Notably, isolates Ab_H4 and Ab_H10 displayed the highest virulence, warranting further investigation. Molecular analysis using polymerase chain reaction (PCR) showed that both Ab_H4 and Ab_H10 possessed the bap and katG genes. Although both strains were capable of secreting proteases, only Ab_H4 possessed the cpaA gene, suggesting the involvement of other genes in protease secretion in Ab_H10. Despite high motility, no pilT gene was detected in any isolates. Treatment with sub-inhibitory concentrations of aspirin (3.25 mg/ml) restored susceptibility to previously resistant antibiotics, disrupted biofilm formation and reduced proteases and catalases secretion. However, no significant impact on bacterial motility was observed. Interestingly, sub-inhibitory concentrations of aspirin induced biofilm formation in the environmental strain control (Ab_UKMCC), which was significantly reduced upon exposure to the MIC. These findings highlight the high virulence capabilities of several strains isolated from HCTM and show the potential of aspirin as an antivirulence agent, offering valuable insights for combating A. baumannii infections.

Comparison of antimicrobial activities and resistance mechanisms of eravacycline and tigecycline against clinical Acinetobacter baumannii isolates in China.

Tigecycline (TGC) is currently used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections, while eravacycline (ERV), a new-generation tetracycline, holds promise as a novel therapeutic option for these infections. However, differences in resistance mechanism between ERV and TGC against A. baumannii remain unclear. This study sought to compare the characteristics and mechanisms of ERV and TGC resistance among clinical A. baumannii isolates. A total of 492 isolates, including 253 CRAB and 239 carbapenem-sensitive A. baumannii (CSAB) isolates, were collected from hospitalized patients in China. The MICs of ERV and TGC against A. baumannii were determined by broth microdilution. Genetic mutations and expressions of adeB, adeG, adeJ, adeS, adeL, and adeN in resistant strains were examined by PCR and qPCR, respectively. The in vitro recombination experiments were used to verify the resistance mechanism of ERV and TGC in A. baumannii. The MIC90 of ERV in CRAB and CSAB isolates were lower than those of TGC. A total of 24 strains resistant to ERV and/or TGC were categorized into three groups: only ERV-resistant (n = 2), both ERV- and TGC-resistant (n = 7), and only TGC-resistant (n = 15). ST208 (75%, n = 18) was a major clone that has disseminated in all three groups. The ISAba1 insertion in adeS was identified in 66.7% (6/9) of strains in the only ERV-resistant and both ERV- and TGC-resistant groups, while the ISAba1 insertion in adeN was found in 53.3% (8/15) of strains in the only TGC-resistant group. The adeABC and adeRS expressions were significantly increased in the only ERV-resistant and both ERV- and TGC-resistant groups, while the adeABC and adeIJK expressions were significantly increased and adeN was significantly decreased in the only TGC-resistant group. Expression of adeS with the ISAba1 insertion in ERV- and TGC-sensitive strains significantly increased the ERV and TGC MICs and upregulated adeABC and adeRS expressions. Complementation of the wildtype adeN in TGC-resistant strains with the ISAba1 insertion in adeN restored TGC sensitivity and significantly downregulated adeIJK expression. In conclusion, our data illustrates that ERV is more effective against A. baumannii clinical isolates than TGC. ERV resistance is correlated with the ISAba1 insertion in adeS, while TGC resistance is associated with the ISAba1 insertion in adeN or adeS in A. baumannii.

Genome analysis of tigecycline-resistant Acinetobacter baumannii reveals nosocomial lineage shifts and novel resistance mechanisms.

To investigate the characteristics and clonal dynamics of tigecycline-resistant Acinetobacter baumannii (TRAB) isolates from a Chinese hospital from 2016 to 2021. A total of 64 TRAB isolates were screened and WGS was performed. Phylogenetic analysis and non-polymorphic mutation analysis were used to analyse their clonal dynamics and tigecycline resistance-related mutations. RT-PCR was used to analyse the expression of the resistance-nodulation cell-division (RND) efflux pump genes adeB and adeJ. Gene cloning was used to explore the effect of tet(39) variants on tigecycline resistance. Most TRAB isolates were found to be MDR, with 95% (61/64) of the isolates showing resistance to carbapenems. These TRAB isolates were classified into three primary genetic clusters based on core-genome SNPs. The KL2 cluster persisted throughout the study period, whereas the KL7 cluster emerged in 2019 and became the dominant clone. The KL7 cluster carried more antimicrobial resistance genes than the other two clusters. The predominant tigecycline resistance mechanism of the KL2 cluster and KL7 cluster was IS insertion in adeN (82.1%, 23/28) and genetic alterations in adeS (76.2%, 16/21), respectively. Eleven novel AdeS mutations were identified associated with elevated AdeB expression and tigecycline resistance. Moreover, we characterized a plasmid-borne tet(39) variant with an Ala-36-Thr substitution that synergizes with the RND efflux pump to confer high-level tigecycline resistance. This work provides important insights into the diverse mechanisms associated with tigecycline resistance in A. baumannii, highlighting a pressing need for further monitoring of ST2-KL7 A. baumannii in clinical settings.

Polymyxin B adjuvants against polymyxin B- and carbapenem-resistant Gram-negative bacteria.

Aim: Polymyxin B (PMB) is one of the few therapeutic options for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the emergence of PMB-resistant CR-GNB strains has prompted the exploration of antibiotic adjuvants as potential therapeutic avenues. Thus, this study evaluates the potential of 3,5-dinitrobenzoic acid derivatives (DNH01, DNH11, DNH13 and DNH20) and isoniazid-N-acylhydrazones (INZ1-7, INZ9 and INZ11) as adjuvants to enhance PMB efficacy against CR-GNB.Materials & methods: MIC, MBC and drug combination assays were conducted using multidrug-resistant clinical isolates of Enterobacterales and Acinetobacter baumannii. In addition, the effects of PMB and PMB+DNH derivatives were assessed through flow cytometry and scanning electron microscopy (SEM).Results: DNH01, DNH11 and DNH20, unlike the INH-acylhydrazones, significantly restored PMB activity (MIC≤2μg/ml) in 80% of the tested isolates. Flow cytometry and SEM assays confirmed that DNH derivatives rescued the activity of PMB, yielding results comparable to those expected for PMB alone but at 256-fold lower concentrations.Conclusion: These findings suggest DNH derivatives hold substantial promise as PMB adjuvants to combat PMB-resistant CR-GNB infections.

Characterization of the carbapenem-resistant Acinetobacter baumannii clinical reference isolate BAL062 (CC2:KL58:OCL1): resistance properties and capsular polysaccharide structure.

The carbapenem-resistant Acinetobacter baumannii isolate BAL062 is a clinical reference isolate used in several recent experimental studies. It is from a ventilator-associated pneumonia (VAP) patient in an intensive care unit at the Hospital for Tropical Diseases (HTD), Ho Chi Minh City, Vietnam in 2009. Here, BAL062 was found to belong to the B sub-lineage of global clone 2 (GC2) isolates in the previously reported outbreak (2008 and 2012) of carbapenem-resistant VAP A. baumannii at the HTD. While related sub-lineage B outbreak isolates were extensively antibiotic-resistant and carry GC2-associated genomic resistance islands, AbGRI1, AbGRI2, and AbGRI3, BAL062 has lost AbGRI3 and three aminoglycoside resistance genes, armA, aacA4, and aphA1, leading to amikacin, tobramycin and kanamycin susceptibility. The location of Tn2008VAR found in the chromosome of this sub-lineage was also corrected. Like many of the outbreak isolates, BAL062 carries the KL58 gene cluster at the capsular polysaccharide (CPS) synthesis locus and an annotation key is provided. As information about K type is important for the development of novel CPS-targeting therapies, the BAL062 K58-type CPS structure was established using NMR spectroscopy. It is most closely related to K2 and K93, sharing similar configurations and linkages between K units, and contains the rare higher monosaccharide, 5,7-diacetamido-3,5,7,9-tetradeoxy-d-glycero-l-manno-non-2-ulosonic acid (5,7-di-N-acetyl-8-epipseudaminic acid; 8ePse5Ac7Ac), the 8-epimer of Pse5Ac7Ac (5,7-di-N-acetylpseudaminic acid). Inspection of publicly available A. baumannii genomes revealed a wide distribution of the KL58 locus in geographically diverse isolates belonging to several sequence types that were recovered over two decades from clinical, animal, and environmental sources.IMPORTANCEMany published experimental studies aimed at developing a clearer understanding of the pathogenicity of carbapenem-resistant Acinetobacter baumannii strains currently causing treatment failure due to extensive antibiotic resistance are undertaken using historic, laboratory-adapted isolates. However, it is ideal if not imperative that recent clinical isolates are used in such studies. The clinical reference isolate characterized here belongs to the dominant A. baumannii GC2 clone causing extensively resistant infections and has been used in various recent studies. The correlation of resistance profiles and resistance gene data is key to identifying genes available for gene knockout and complementation analyses, and we have mapped the antibiotic resistance genes to find candidates. Novel therapies, such as bacteriophage or monoclonal antibody therapies, currently under investigation as alternatives or adjuncts to antibiotic treatment to combat difficult-to-treat CRAb infections often exhibit specificity for specific structural epitopes of the capsular polysaccharide (CPS), the outer-most polysaccharide layer. Here, we have solved the structure of the CPS type found in BAL062 and other extensively resistant isolates. As consistent gene naming and annotation are important for locus identification and interpretation of experimental studies, we also have correlated automatic annotations to the standard gene names.

Phenotypic and genotypic determination of resistance to common disinfectants among strains of Acinetobacter baumannii producing and non-producing biofilm isolated from Iran

BackgroundNosocomial infections are a global problem in hospitals all around the world. It is considered a major health problem, especially in developing countries. The increase in the patient’s stay in hospitals has increased the mortality rate, and consequently, the costs drastically increase. The main purpose of using disinfectants in the hospital environment is to reduce the risk of nosocomial infections. Ethylene diamine tetra acetic acid (EDTA) causes lysis and increases susceptibility to antimicrobial agents in the planktonic form of bacteria. This substance affects the permeability of the outer membrane of bacteria. It also prevents the formation of biofilms by bacteria.Materials and methodsIn the current study, 120 isolates of Acinetobacter baumannii (A. baumannii) were confirmed by phenotypic and genotypic methods. Antibiogram was performed and then the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of isolates against 5% sodium hypochlorite, ethanol %70, sayasept-HP 2%, chlorhexidine 2%, dettol 4/8% were evaluated. In addition, the disinfectant effect was re-evaluated with the mixture of EDTA solution. All isolates were examined for biofilm presence by crystal violet staining method in triplicates and repeated three times for each strain. Also for all isolates detection of efflux pump genes (Qac-E, qacE-Δ1, SUG-E) by PCR technique was done.ResultsAntibiogram results of A. baumannii showed that 6.7% were Multi-drug-resistant (MDR), and 89.2% were Extensively drug-resistant (XDR) isolates. The highest effect of disinfectants was related to 5% sodium hypochlorite, and the least effect was 70% ethanol. EDTA increases the efficacy of selected disinfectants significantly. The highest prevalence of the efflux pump genes was related to SUG-E (95%) and Qac-E (91.7%), and, the qacE-Δ1 gene with 12.5%. The biofilm production rate was 91.3% among all isolates.ConclusionThe best and safest way to disinfect hospital floors and surfaces is to choose the right disinfectants, and learn how to use them properly. In this study, a mixture of disinfectants and EDTA had a significant effect on bactericidal activity. it was found that improper use of disinfectants, especially the use of sub-inhibitory dilutions, increases the resistance of bacteria to disinfectants.

Real-world performance of susceptibility testing for cefiderocol: insights from a prospective multicentre study on Gram-negative bacteria.

Cefiderocol is a novel siderophore-conjugated cephalosporin developed for the treatment of multidrug-resistant Gram-negative bacterial (GNB) infections. However, the current gold standard for cefiderocol susceptibility testing, broth microdilution (BMD) using iron-depleted cation-adjusted Mueller-Hinton broth, presents challenges for many microbiology laboratories. In this study, we evaluate the real-world performance of disc diffusion (DD) and a commercial BMD method (ComASP®) to test cefiderocol susceptibility in a series of isolates collected prospectively from severely ill patients in a multicentre study. The susceptibilities of 1472 isolates (632 Enterobacterales, 532 Pseudomonas aeruginosa, 84 Acinetobacter spp. and 224 Stenotrophomonas maltophilia) collected in 60 Spanish hospitals were analysed following the EUCAST 2023 and 2024 criteria. We assessed the performance of DD (cefiderocol 30 μg disc, Liofilchem) and a commercial BMD method (ComASP® Cefiderocol, Liofilchem). A total of 1408 and 1450 isolates were susceptible by DD and ComASP® BMD, respectively. Overall, the agreement between both methods was 96.9%. Forty-four isolates were resistant by DD but susceptible by ComASP® BMD, and two were susceptible by DD but resistant by ComASP® BMD (Acinetobacter baumannii isolates). Adoption of the updated 2024 EUCAST DD breakpoints and areas of technical uncertainty (ATUs) led to a decrease in susceptibility among Enterobacterales (95.3% versus 92.6%). DD is a straightforward, rapid and accessible method for routine determination of cefiderocol susceptibility in real-world practice. ComASP® BMD shows a high agreement with DD in susceptible isolates and may help to resolve DD interpretability concerns in isolates with susceptibility results within the ATU, but caution is warranted when testing resistant isolates.

Examining the Frequency of Selected Genes Involved in Biofilm Formation in Clinical Isolates of Acinetobacter Baumannii

Introduction: Acinetobacter baumannii, a non-fermenting Gram-negative coccobacillus, exhibits high resistance to antimicrobial compounds. Biofilm formation is a crucial feature in many Acinetobacter species, contributing to their antibiotic resistance. The present study aimed to investigate the prevalence of ompA, csuA, bap and pgaB genes in clinical isolates of Acinetobacter baumannii with biofilm formation ability. Methods: In this cross-sectional study, 49 isolates of Acinetobacter baumannii were collected from patients hospitalized in the health centers of Borujerd City. Acinetobacter baumannii isolates were confirmed by biochemical tests. In these isolates, the biofilm production ability was investigated by microtitreplate method. Then, using PCR method and specific primers, ompA, csuA, bap and pgaB genes were identified.The collected data were analyzed descriptively and analytically using SPSS version 16 software. Data analysis was done with Chi-square test, Fisher's exact test, and P<0.05 was considered as the basis of significance. Results: The presence of ompA, csuA, bap, and pgaB genes was detected in 87%, 92%, 98%, and 100% of the isolates, respectively. Additionally, the microtitreplate method revealed that biofilm formation was strong in 3 isolates (6%), moderate in 17 isolates (35%), and weak in 29 isolates (59%). Conclusion: The prevalence of genes associated with biofilm formation in Acinetobacter baumannii isolates was high. This suggests that the studied isolates possess a significant ability to form biofilm structures.

Comparison of Beta-Lactamase Profiles and Epidemiology of Multi-Drug Resistant Acinetobacter baumannii Isolates in Southwest Turkey: 2011 vs. 2019 Study

Background: The most significant problem encountered with hospital infections caused by multi-drug resistant Acinetobacter baumannii isolates is the difficulty in treatment. Defining resistance mechanisms is important for the development of treatment strategies. Objectives: The aim of this study was to investigate the beta-lactamase genes and clonal relationship in multi-drug resistant A. baumannii isolates in Mugla, Turkey, as no data are currently available for this province. Methods: Total 96 multi-drug resistant A. baumannii isolates obtained from hospitalized patients, between 2011 - 2012 period (n = 61) and in year 2019 (n = 35) were investigated and compared for antibiotic susceptibilities, beta-lactamase enzyme encoding genes by polymerase chain reaction (PCR) method. Repetitive extragenic palindromic (REP) PCR was made for dendrogram analysis to illustrate hierarchical relationship between isolates. Results: Overall, 74.0% of the isolates were obtained from patients in intensive care units. All multi-drug resistant isolates were found resistant to ciprofloxacin, piperacillin, piperacillin-tazobactam, meropenem, and imipenem by the disk diffusion method. The minimum inhibitory concentration values indicated that all isolates were resistant to imipenem, while colistin resistance was determined as 21.9%. The ISAba-I insertion element was present in all isolates. BlaOXA-23-like was present in 96.9%, and blaOXA-24-like was detected in three (3.1%) isolates. blaNDM positivity was shown in 5.2% of isolates. The indistinguishable or closely related isolates ratio was detected as 29.5% for the 2011 - 2012 period and 80% for 2019. Conclusions: Our findings showed that antibiotic resistance rates were high in A. baumannii, particularly isolated from intensive care unit patients in Mugla province. The prevalence of beta-lactamase and metallo-beta-lactamase genes has been increasing year by year, with the blaOXA-23-like gene region being the most prevalent. Additionally, the co-existence of these genes among strains is also on the rise. These findings from two different periods may provide useful reference data for future studies.

Characterisation of carbapenemase-producing Gram-negative bacilli among clinical isolates in a tertiary care centre in Kerala, South India

Background: Infections caused by carbapenem-resistant Gram-negative bacteria are a cause for concern due to the limited choice of antibiotics available for their treatment. Aims, Settings and Design: This study screened multidrug-resistant (MDR) Gram-negative bacilli isolated from clinical samples over a period of one year, for carbapenem resistance and characterised them using phenotypic methods such as combined disc diffusion test (CDDT), modified Hodge test (MHT), E-test for metallo-beta-lactamase (MBL) and molecular method, PCR. Materials and Methods: Two hundred and ten MDR Gram-negative bacilli were screened for carbapenem resistance using Imipenem and Meropenem disc diffusion. These were further checked for carbapenemase production by CDDT, MHT and E-test for MBL. Those positive by E-test were subjected to PCR. Uniplex PCR for New Delhi metallo-beta-lactamase-1 was used for Escherichia coli and Klebsiella pneumoniae , and multiplex PCR for Imipenemase and Verona imipenemase was used for Pseudomonas aeruginosa and Acinetobacter baumannii isolates. Results: Twenty-three (11%) isolates were found to be carbapenem-resistant and included E. coli (six) K. pneumoniae (three), P. aeruginosa (five) and A. baumannii (nine). Seventeen (74%) isolates were positive by phenotypic methods and were subjected to PCR. Out of eight Enterobacteriaceae isolates subjected to PCR, all were positive for bla NDM gene. All were negative for bla KPC gene. All five A. baumannii isolates subjected to PCR were found to contain bla VIM gene. Two out of four P. aeruginosa isolates were positive for bla IMP , one was positive for bla VIM gene. One P. aeruginosa isolate was positive for both bla IMP and bla VIM gene. Conclusions: In view of the increasing resistance of Gram-negative bacilli to carbapenems, rational use of antibiotics needs to be emphasised.

Efficacy of aspergillomarasmine A/meropenem combinations with and without avibactam against bacterial strains producing multiple β-lactamases.

The effectiveness of β-lactam antibiotics is increasingly threatened by resistant bacteria that harbor hydrolytic β-lactamase enzymes. Depending on the class of β-lactamase present, β-lactam hydrolysis can occur through one of two general molecular mechanisms. Metallo-β-lactamases (MBLs) require active site Zn2+ ions, whereas serine-β-lactamases (SBLs) deploy a catalytic serine residue. The result in both cases is drug inactivation via the opening of the β-lactam warhead of the antibiotic. MBLs confer resistance to most β-lactams and are non-susceptible to SBL inhibitors, including recently approved diazabicyclooctanes, such as avibactam; consequently, these enzymes represent a growing threat to public health. Aspergillomarasmine A (AMA), a fungal natural product, can rescue the activity of the β-lactam antibiotic meropenem against MBL-expressing bacterial strains. However, the effectiveness of this β-lactam/β-lactamase inhibitor combination against bacteria producing multiple β-lactamases remains unknown. We systematically investigated the efficacy of AMA/meropenem combination therapy with and without avibactam against 10 Escherichia coli and 10 Klebsiella pneumoniae laboratory strains tandemly expressing single MBL and SBL enzymes. Cell-based assays demonstrated that laboratory strains producing NDM-1 and KPC-2 carbapenemases were resistant to the AMA/meropenem combination but became drug-susceptible upon adding avibactam. We also probed these combinations against 30 clinical isolates expressing multiple β-lactamases. E. coli, Enterobacter cloacae, and K. pneumoniae clinical isolates were more susceptible to AMA, avibactam, and meropenem than Pseudomonas aeruginosa and Acinetobacter baumannii isolates. Overall, the results demonstrate that a triple combination of AMA/avibactam/meropenem has potential for empirical treatment of infections caused by multiple β-lactamase-producing bacteria, especially Enterobacterales.