Baumannii Research Articles

Phytofabrication, characterization and investigation of biological properties of Punica granatum flower-derived silver nanoparticles

Due to the exceeding need to the fabrication metal nanoparticles (NPs) for different applications, exploring innovative eco-friendly approaches for the synthesis of these NPs has attracted significant attention. The objective of this study is to synthesize silver nanoparticles (AgNPs) using the aqueous extract of Punica granatum flowers. Furthermore, it aims to examine the different biological properties of these NPs, such as their antibacterial, antioxidant, anticoagulant, alpha-amylase inhibition, bacterial biofilm inhibition, and bacterial biofilm degradation activities. The AgNPs were characterized using several techniques, including UV–visible (UV–vis) spectroscopy, and Field emission scanning electron microscopy (FE-SEM). Dynamic light scattering (DLS) spectroscopy, X-ray diffraction (XRD) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The AgNPs were spherical in shape, and they had a Z-average diameter of 40.50 nm and a zeta potential of −19.5 mV. The AgNPs, at a concentration of 1000 µg.mL−1, represented in vitro antioxidant and α-amylase inhibition performance of 73.19 ± 1.02 % and 73.84 ± 1.75 %, respectively. Interestingly, the AgNPs exhibited antibacterial activity at phenotypic and molecular levels against Staphylococcus aureus and Acinetobacter baumannii with minimum inhibitory concentration (MIC) value of 32 and 16 µg.mL−1, respectively. AgNPs effectively downregulated the biofilm formation of icaA and icaD genes in S. aureus, with a stronger impact on icaA, though tetracycline exhibited superior inhibition overall at the concentration of MIC. In A. baumannii, AgNPs reduced the expression of the biofilm formation pgaA and bfmsS genes, but not bfmsR, while tetracycline suppressed all three genes at the concentration of MIC. By addressing these novel aspects, this study aims to advance the field of green nanotechnology and open new avenues for the application of biogenic AgNPs in various domains.

Phage-derived polysaccharide depolymerase potentiates ceftazidime efficacy against Acinetobacter baumannii pneumonia via low-serum-dependent mechanisms

The emergence of multidrug-resistant Acinetobacter baumannii (MDR-AB), which most commonly manifests as pneumonia, has posed significant clinical challenges and called for novel treatment strategies. Phage depolymerases, which degrade bacterial surface carbohydrates, have emerged as potential antimicrobial agents. However, their preclinical application is limited to systemic infections due to their dependency on serum-mediated bacterial killing. To extend the treatment paradigm of depolymerase to low-serum lung infections, we explored the feasibility of applying phage depolymerase to potentiate antibiotic efficacy in controlling MDR-AB pneumonia. Using a model depolymerase, Dpo71, we observed that it could effectively potentiate antibiotic efficacy against MDR-AB2 bacteria in low-serum conditions mimicking lung milieu but showed no adjuvant effect in serum-free conditions. Unprecedentedly, we reported this low-serum-dependent mechanism that polysaccharide-degrading enzyme Dpo71 exposed bacteria to serum-induced membrane permeabilization and oxidative phosphorylation pathway inhibition, leading to a weakened ATP-dependent efflux pump and strengthened ROS-induced membrane permeabilization. These joint effects facilitated antibiotic (ceftazidime, CFZ) binding, ultimately exerting bactericidal effects. Resultantly, the bacterial load in the lungs of the Dpo71-CFZ combination group was significantly reduced compared with the Dpo71-alone and CFZ-alone groups. Overall, this study unravels the low-serum-dependent mechanisms by which depolymerase potentiated antibiotic efficacy, highlighting its potential as a novel strategy to enhance antibiotic activity against severe pneumonia.

Emergence of extensively drug-resistant hypervirulent Acinetobacter baumannii isolated from patients with bacteremia: bacterial phenotype and virulence analysis

ObjectivesIndividuals infected with extensively drug-resistant (XDR) Acinetobacter baumannii are difficult to cure and have a high mortality rate. In this study, we compared the genomic and phenotypic differences between XDR and non-multidrug-resistant (MDR) A. baumannii and further characterized hypervirulent XDR A. baumannii. MethodsA total of 1,403 Acinetobacter isolates were collected from patients with bacteremia between 1997 and 2015. Antimicrobial susceptibility test was performed to categorize isolates into non-MDR, MDR, and XDR groups. The presence of selected virulence-associated genes was determined by PCR. Bacterial phenotypes, including iron acquisition, biofilm formation, capsule production, and virulence to larvae and mice, were determined. ResultsMultilocus sequence types revealed the high prevalence of ST2 (81.6%) and ST129 (18.4%) among 49 XDR isolates and sequence types of 18 non-MDR isolates were more diverse. Virulence-associated phenotypic assays showed that XDR isolates had higher iron acquisition ability and capsule production and higher virulence to Galleria mellonella larvae. However, their biofilm formation ability was lower compared to that of non-MDR isolates. XDR isolates contained more virulence genes, tonB, hemO, abaI, and ptk, while non-MDR isolates contained more pld and ompA. Twenty-one XDR isolates caused <20% larvae survival rate after 7 days post-infection were defined as hypervirulent XDR isolates. Among them, isolates 1677 (ST129) and 929-1 (ST2) also caused the death of all infected mice within two days. ConclusionSome subpopulations of highly drug-resistant ST2 also exhibit high virulence. Therefore, it is of utmost importance to continue monitoring the spread of hypervirulent XDR A. baumannii isolates.

Implementation of Silver Nanoparticles Green Synthesized with Leaf Extract of Coccinia grandis as Antimicrobial Agents Against Head and Neck Infection MDR Pathogens.

Head and neck infections (HNI) associated with multidrug resistance (MDR) offer several health issues on a global scale due to inaccurate diagnosis. This study aimed to identify the bacteria and Candidal isolates and implement the silver nanoparticles green synthesized with leaf extract of Coccinia grandis (Cg-AgNPs) as a therapeutic approach against HNI pathogens. The Cg-AgNPs were characterized by the UV-visible spectrophotometer, FT-IR analysis, Zeta particle size, Zeta potential, and field emission scanning electron microscope (FESEM) analysis to validate the synthesis of nanoparticles. Additionally, the antimicrobial activity of Cg-AgNPs was presented by the zone of inhibition (ZOI), minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC), and antibiofilm assay. Moreover, the cell wall rupture assay was visualized on SEM for the morphological study of antimicrobial activities, and the in-vivo toxicity was performed in a swiss mice model to evaluate the impact of Cg-AgNPs on various biological parameters. Different bacterial strains (Staphylococcus aureus, Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa) and Candida sp. (Candida albicans, Candida tropicalis, Candida orthopsilosis, and Candida glabrata) were identified. The MIC, MBC, and antibiofilm potential of Cg-AgNPs were found to be highest against A. baumannii: 1.25 μg/ml, 5 μg/ml, and 85.01±5.19% respectively. However, C. albicans and C. orthopsilosis revealed 23 mm and 21 mm of ZOI. Subsequently, the micromorphology of the cell wall rupture assay confirmed the efficacy of Cg-AgNPs, and no significant alterations were seen in biochemical and hematological parameters on the swiss mice model in both acute and subacute toxicity studies. The green synthesized Cg-AgNPs have multifunctional activities like antibacterial, anticandidal, and antibiofilm activity with no toxicity and can be introduced against the HNI pathogens.

Antibacterial Potential of Tetrahydrocarbazoles (THCZ): A Review

: Antibiotic resistance has become a major public threat across the globe associated with human health. Some bacterial and fungal infections produce resistance, such as methicillinresistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE) and multidrug-resistant (MDR) species Acinetobacter baumannii etc. Tetrahydrocarbazoles (THCz) are a sub-class of indole alkaloids profoundly present in natural products and biologically active compounds and have displayed potential biological activities in literature. THCz exhibit potential antibacterial activities through major bacterial pathways like cell wall synthesis inhibition and DNA gyrase enzyme inhibition with DNA sliding clamp inhibitors and MreB inhibitors. These THCZ also showed significant in vitro antibacterial activities against bacterial-resistant species, such as MRSA, VRE and Acinetobacter baumannii (MDR) in literature. MTDL (Multi Target Direct ligand) approach has been significantly used for the design of THC motif-based antibacterial agents. In this review article, we collected literature on THCz as a potential antibacterial agent from 2014 to date. The review study of THC core-based derivatives found excellent in vitro antibacterial profiles and revealed that they can play a significant role in drug discovery and the development of new antibiotics against various infectious diseases.

Isolation, characterization, and potential application of Acinetobacter baumannii phages against extensively drug-resistant strains.

One of the significant issues in treating bacterial infections is the increasing prevalence of extensively drug-resistant (XDR) strains of Acinetobacter baumannii. In the face of limited or no viable treatment options for extensively drug-resistant (XDR) bacteria, there is a renewed interest in utilizing bacteriophages as a treatment option. Three Acinetobacter phages (vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln) were identified from hospital sewage and analyzed for their morphology, host ranges, and their genome sequences were determined and annotated. These phages and vB_AbaS_SA1 were combined to form a phage cocktail. The antibacterial effects of this cocktail and its combinations with selected antimicrobial agents were evaluated against the XDR A. baumannii strains. The phages exhibited siphovirus morphology. Out of a total of 30 XDR A. baumannii isolates, 33% were sensitive to vB_AbaS_Ftm, 30% to vB_AbaS_Gln, and 16.66% to vB_AbaS_Eva. When these phages were combined with antibiotics, they demonstrated a synergistic effect. The genome sizes of vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln were 48487, 50174, and 50043 base pairs (bp), respectively, and showed high similarity. Phage cocktail, when combined with antibiotics, showed synergistic effects on extensively drug-resistant (XDR) strains of A. baumannii. However, the need for further study to fully understand the mechanisms of action and potential limitations of using these phages is highlighted.

Efficacy of fosfomycin-containing regimens in treating severe infections caused by KPC-producing Klebsiella pneumoniae and carbapenem-resistant Acinetobacter baumannii in critically ill patients

IntroductionFosfomycin (FOS) is gaining increasing importance as part of combination therapy for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) and KPC-producing Klebsiella pneumoniae (KPC-Kp) thanks to its in-vitro synergism with several antibiotics, high tissue distribution and good tolerability.We analyzed the effect on 30-day survival of FOS-containing regimens compared to NO-FOS in critically ill patients admitted to intensive care unit with CRAB or KPC-Kp infections. Secondary objectives were to evaluate clinical cure and microbiologic eradication of FOS versus NO-FOS group. Materials/methodsMonocentric retrospective observational study including SARS-Cov2-negative critically ill patients with KPC-Kp or CRAB infection treated with combination antibiotic therapy with or without FOS for ≥48h (FOS vs NO-FOS groups). Primary outcome was 30-d mortality, secondary outcomes clinical cure and microbiological eradication. ResultsOf the 78 patients analyzed, 26 (33.3%) were men, median (IQR) age and Charlson Comorbidity Index (CCI) were 67 years (53-74) and 4 (2-5), respectively. Septic shock was present in 18 patients (23.1%), 37 (47.4%) were CRAB, 41 (52.6%) KPC-Kp. Compared to NO-FOS, patients receiving FOS had higher clinical cure (89.2%vs65.9%, p=0.017), early (<72h) improvement (78.4%vs52.2%, p=0.018), microbiological eradication (87.5%vs62.2%, p=0.027) and lower 7-, 14- and 30-d mortality (0%vs4.6%, p=0.027, 2.7%vs22%, p=0.016, 13.5%vs34.2%, p=0.039, respectively). This effect was particularly evident for infections sustained by KPC-Kp. At multivariate analysis, receiving FOS was independently associated with survival (HR 0.29, IC95% 0.09-0.93, p=0.038), confirmed after IPTW (HR 0.501 IC95% 0.25-0.98 p=0.042). ConclusionsFOS-containing regimens exhibit higher clinical cure, higher microbiological eradication and reduced mortality than NO FOS-containing regimens in critically ill patients with CRAB and KPC-Kp infections.

Capsular polysaccharide structure of Acinetobacter baumannii K58 from clinical isolate MRSN31468

Capsular polysaccharides (CPS) of Acinetobacter baumannii is a virulence factor with diverse structures. CPS are produced by the CPS biosynthesis gene cluster in their K locus (KL). However, CPS variations may occur due to insertion of additional genes from external sources, e.g., prophages. Recently, the CPS structure from a clinical isolate, BAL062 which includes KL58 locus, was found to have a pseudaminic acid isomer (8ePse5NAc7NAc) as a result of prophage inserted epaA/epaB genes. Here, we report a CPS structure produced by A. baumannii strain MRSN31468 which also belongs to a KL58 type. The K58 CPS structure was determined by 1D and 2D NMR analysis of the oligosaccharides derived from the CPS by a phage depolymerase, and supported by the sugar composition analysis. The K58 CPS structure has the following tetra saccharide repeating unit: [Display omitted] The K58 CPS differs from the CPS from BAL062 only by replacing 8-epimerized β-8ePse5NAc7NAc with β-Pse5NAc7NAc.

Diagnostic advances in sepsis: A comparative analysis of syndromic approaches and molecular biology techniques in clinical bacteremia

Sepsis remains a leading cause of morbidity and mortality. This retrospective study, conducted at Avicenne Military Hospital in Marrakech over ten years, analyzed 3721 blood cultures, identifying 420 cases of bacteremia (11.3% positivity rate). The predominant isolates included Staphylococcus aureus, coagulase-negative staphylococci, Escherichia coli, Klebsiella spp., and Acinetobacter baumannii, with significant resistance patterns observed. Notably, 50% of S. aureus were methicillin-resistant (MRSA), while extended-spectrum beta-lactamase (ESBL) production was found in 30% of E. coli and Klebsiella pneumoniae isolates. The FilmArray multiplex PCR system was utilized to enhance rapid pathogen identification, reducing turnaround time from 72 hours to under 2 hours, and demonstrated high concordance with conventional cultures. The molecular diagnostics identified various resistant strains, including carbapenemase-producing organisms in K. pneumoniae and multidrug-resistant A. baumannii, underscoring the critical need for effective antimicrobial stewardship. Overall, this study emphasizes the evolving epidemiology of bacteremia, the rising antimicrobial resistance, and the utility of rapid molecular diagnostics in guiding timely and appropriate treatment, ultimately aiming to improve patient outcomes in sepsis management.

Microalgae-Assisted Treatment of Wastewater Originating from Varied Sources, Particularly in the Context of Heavy Metals and Antibiotic-Resistant Bacteria

The increasing prevalence of heavy metals and antibiotic-resistant bacteria in wastewater (WW) raises serious environmental and public health concerns. This study investigates the efficiency of the microalgal strain Chlorella vulgaris EV-465 in treating wastewater and evaluates the antibiotic resistance profile of bacterial strains obtained from WW samples. Chlorella vulgaris EV-465 was used to treat four types of wastewater—domestic, municipal, hospital, and industrial wastewater—through 21 days of incubation. The findings demonstrated pH stabilization and significant decreases in nutrients (total nitrogen—TN, total phosphorus—TP), biological oxygen demand (BOD), chemical oxygen demand (COD), heavy metal (HM) concentrations, and bacterial count. Copper (Cu) showed the highest reduction, decreasing by 80% in industrial wastewater within 14 days, while lead (Pb) proved more resistant to removal, with only a 50% decrease by day 21. Additionally, the algae decreased bacterial counts, lowering colony-forming units (Log CFU/mL) from 9.04 to 4.65 in municipal wastewater over the 21-day period. Antibiotic susceptibility tests for isolated bacterial strains revealed high levels of resistance, with seven out of nine bacterial strains exhibiting multidrug resistance. Notably, Enterococcus faecium (PBI08), Acinetobacter baumannii (YBH19), and Pseudomonas aeruginosa (NBH16) displayed resistance to all nine antibiotics tested. Among the tested antibiotics, Ciprofloxacin showed the highest efficacy, with 66% susceptibility of tested bacterial strains. Cluster and phylogenetic analyses showed that the majority of the isolated bacterial strains belonged to the genera Pseudomonas and Escherichia, highlighting their genetic diversity and varied resistance mechanisms.

Cryo-EM characterization of the anydromuropeptide permease AmpG central to bacterial fitness and β-lactam antibiotic resistance.

Bacteria invest significant resources into the continuous creation and tailoring of their essential protective peptidoglycan (PG) cell wall. Several soluble PG biosynthesis products in the periplasm are transported to the cytosol for recycling, leading to enhanced bacterial fitness. GlcNAc-1,6-anhydroMurNAc and peptide variants are transported by the essential major facilitator superfamily importer AmpG in Gram-negative pathogens including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Accumulation of GlcNAc-1,6-anhydroMurNAc-pentapeptides also results from β-lactam antibiotic induced cell wall damage. In some species, these products upregulate the β-lactamase AmpC, which hydrolyzes β-lactams to allow for bacterial survival and drug-resistant infections. Here, we have used cryo-electron microscopy and chemical synthesis of substrates in an integrated structural, biochemical, and cellular analysis of AmpG. We show how AmpG accommodates the large GlcNAc-1,6-anhydroMurNAc peptides, including a unique hydrophobic vestibule to the substrate binding cavity, and characterize residues involved in binding that inform the mechanism of proton-mediated transport.

Dietary zinc deficiency promotes Acinetobacter baumannii lung infection via IL-13 in mice.

Dietary zinc deficiency is a major risk factor for pneumonia. Acinetobacter baumannii is a leading cause of ventilator-associated pneumonia and a critical public health threat due to increasing rates of multidrug resistance. Patient populations at increased risk for A. baumannii pneumonia are also at increased risk of zinc deficiency. Here we established a mouse model of dietary zinc deficiency and acute A. baumannii pneumonia to test the hypothesis that host zinc deficiency contributes to A. baumannii pathogenesis. We showed that zinc-deficient mice have significantly increased A. baumannii burdens in the lungs, dissemination to the spleen and higher mortality. During infection, zinc-deficient mice produce more pro-inflammatory cytokines, including IL-13. Administration of IL-13 promotes A. baumannii dissemination in zinc-sufficient mice, while antibody neutralization of IL-13 protects zinc-deficient mice from A. baumannii dissemination and mortality during infection. These data highlight the therapeutic potential of anti-IL-13 antibody treatments, which are well tolerated in humans, for the treatment of pneumonia.

Transcriptome and interactome-based analyses to unravel crucial proteins and pathways involved in Acinetobacter baumannii pathogenesis.

The present study employed an integrated transcriptome and interactome-based analyses to identify key proteins and pathways associated with Acinetobacter baumannii infection towards the development of novel therapeutics against this pathogen. Transcriptome analysis of A.baumannii strains (ATCC 17978 and AbH12O-A2) identified 253 and 619 differentially expressed genes (DEGs), respectively. These genes were involved in essential molecular functions, including DNA binding, metal ion binding, and oxidoreductase activity. The centrality and module analyses of these identified DEGs had shortlisted 27 and 41 hub proteins, which were central to the ATCC 17978 and AbH12O-A2 networks, and essential for bacterial survival. Significantly, three proteins (SecA, glutathione synthase, and aromatic-amino-acid transaminase) from the ATCC 17978 strain and seven proteins (ATP synthase subunit alpha, translation initiation factor IF-2, SecY, elongation factors G, Tu, and Ts, and tRNA guanine-N1-methyltransferase) from the AbH12O-A2 strain showed interactions with human proteins, identified through host-pathogen interaction (HPI) analysis of hub proteins (referred as hub-HPI proteins). These proteins were observed to participate in vital pathways, including glutathione metabolism, secondary metabolite biosynthesis and quorum sensing. Targeting these hub-HPI proteins through novel therapeutic strategies holds the potential to disrupt the critical bacterial pathways, thereby controlling A. baumannii infections. Furthermore, their localization analysis indicated that nine proteins were cytoplasmic and one was membrane protein. Among them, six were druggable and four were novel proteins. Overall, this comprehensive study provides valuable insights into the crucial proteins and pathways involved during A. baumannii infection, and offers potential therapeutic targets for designing novel antimicrobial agents to tackle the pathogen.

The antimicrobial and antibiofilm effects of gentamicin, imipenem, and fucoidan combinations against dual-species biofilms of Staphylococcus aureus and Acinetobacter baumannii isolated from diabetic foot ulcers.

Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia due to impaired insulin production or utilization, leading to severe health complications. Diabetic foot ulcers (DFUs) represent a major complication, often exacerbated by polymicrobial infections involving Staphylococcus aureus and Acinetobacter baumannii. These pathogens, notorious for their resistance to antibiotics, complicate treatment efforts, especially due to biofilm formation, which enhances bacterial survival and resistance. This study explores the synergistic effects of combining gentamicin, imipenem, and fucoidan, a sulfated polysaccharide with antimicrobial properties, against both planktonic and biofilm forms of S. aureus and A. baumannii. Isolates of S. aureus and A. baumannii were collected from DFUs and genetically confirmed. Methicillin resistance in S. aureus was identified through disk diffusion and PCR. Biofilm formation, including dual-species biofilms, was analyzed using the microtiter plate method. The antimicrobial efficacy of gentamicin, imipenem, and fucoidan was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC). Synergistic interactions were evaluated using the fractional inhibitory concentration index (FICi) and fractional bactericidal concentration index (FBCi). The expression of biofilm-associated genes (icaA in S. aureus and bap in A. baumannii) was analyzed, and the cytotoxicity of fucoidan was assessed. The study revealed that 77.4% of S. aureus and all A. baumannii isolates showed multidrug resistance. Among 837 tested conditions for dual-species biofilm formation, 72 resulted in strong biofilm formation and 67 in moderate biofilm formation. The geometric mean MIC values for gentamicin were 12.2µg/mL for S. aureus, 22.62µg/mL for A. baumannii, and 5.87µg/mL for their co-culture; for imipenem, they were 19.84, 9.18, and 3.70µg/mL, respectively, and for fucoidan, 48.50, 31.20, and 19.65µg/mL, respectively. The MBC values for gentamicin were 119.42, 128, and 11.75µg/mL; for imipenem, they were 48.50, 14.92, and 8µg/mL; and for fucoidan, they were 88.37, 62.62, and 42.48µg/mL. The MBIC values were 55.71, 119.42, and 18.66µg/mL for gentamicin; 68.59, 48.50, and 25.39µg/mL for imipenem; and 153.89, 101.49, and 53.53µg/mL for fucoidan. The MBEC values were 315.17, 362.03, and 59.25µg/mL for gentamicin; 207.93, 157.58, and 74.65µg/mL for imipenem; and 353.55, 189.46, and 99.19µg/mL for fucoidan. When cultured in planktonic form, the geometric mean FICi and FBCi values indicated additive effects, while co-culture showed FICi values of ≤ 0.5, suggesting a synergistic interaction. Treatment with gentamicin and fucoidan led to significant downregulation of the icaA and bap genes in both single-species and dual-species biofilms of S. aureus and A. baumannii. The reductions in gene expression were more pronounced in dual-species biofilms compared to single-species biofilms. Additionally, treatment with imipenem and fucoidan also resulted in significant downregulation of these genes in both biofilm types. Cytotoxicity assessments indicated that higher concentrations of fucoidan were toxic, yet no harmful effects were noted at the optimal synergistic concentrations used with antibiotics. In our investigation, we found that combining gentamicin, imipenem, and fucoidan had a synergistic effect on dual-species biofilms of S. aureus and A. baumannii, suggesting potential benefits for treating such infections effectively. This underscores the importance of understanding microbial interactions, antibiotic susceptibility, and biofilm formation in DFUs.

Laboratory detection of carbapenemases among Gram-negative organisms.

SUMMARYThe carbapenems remain some of the most effective options available for treating patients with serious infections due to Gram-negative bacteria. Carbapenemases are enzymes that hydrolyze carbapenems and are the primary method driving carbapenem resistance globally. Detection of carbapenemases is required for patient management, the rapid implementation of infection prevention and control (IP&C) protocols, and for epidemiologic purposes. Therefore, clinical and public health microbiology laboratories must be able to detect and report carbapenemases among predominant Gram-negative organisms from both cultured isolates and direct from clinical specimens for treatment and surveillance purposes. There is not a "one size fits all" laboratory approach for the detection of bacteria with carbapenemases, and institutions need to determine what fits best with the goals of their antimicrobial stewardship and IP&C programs. Luckily, there are several options and approaches available for clinical laboratories to choose methods that best suits their individual needs. A laboratory approach to detect carbapenemases among bacterial isolates consists of two steps, namely a screening process (e.g., not susceptible to ertapenem, meropenem, and/or imipenem), followed by a confirmation test (i.e., phenotypic, genotypic or proteomic methods) for the presence of a carbapenemase. Direct from specimen testing for the most common carbapenemases generally involves detection via rapid, molecular approaches. The aim of this article is to provide brief overviews on Gram-negative bacteria carbapenem-resistant definitions, types of carbapenemases, global epidemiology, and then describe in detail the laboratory methods for the detection of carbapenemases among Gram-negative bacteria. We will specifically focus on the Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex.

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.

“Unmasking the Uncommon”: A case series of multi-drug resistant Elizabethkingia meningoseptica causing late-onset sepsis and meningitis in preterm neonates

Elizabethkingia meningoseptica is an uncommon nosocomial pathogen that causes meningitis, pneumonia, and sepsis in neonates and in immunocompromised individuals. It exhibits resistance to many commonly employed first-line antibiotics used to treat gram-negative pathogens. Herein, we present three cases of late-onset sepsis with multi-drug resistant (MDR) Elizabethkingia meningoseptica in high-risk neonates. Case 1 was a one-day-old preterm low-birth-weight infant who presented with respiratory distress syndrome and septic shock. The patient was intubated and administered empirical broad-spectrum antibiotics and antifungal agents. Blood culture grew Candida krusei, hence Amphotericin B was initiated. Repeat blood culture on day 27 showed gram-negative bacilli, identified as Elizabethkingia meningoseptica by MALDI-TOF . Antibiotic susceptibility testing (AST) revealed resistance to Piperacillin/Tazobactam, but sensitivity to Vancomycin, Levofloxacin, and Minocycline. IV Vancomycin was administered, which resulted in clinical improvement and negative blood culture results. Case 2 was an eleven-day-old preterm, low-birth-weight baby who presented with fever. Initial investigations revealed normal complete blood counts (CBC) parameters and elevated CRP levels. Blood and CSF cultures isolated Elizabethkingia meningoseptica with a similar AST pattern. Intravenous Ciprofloxacin was initiated with clinical improvement and negative follow-up blood cultures. Case 3 was a one-day-old preterm baby, appropriate-to-gestational age, presenting with respiratory distress syndrome. The infant was intubated and started on inotropic support and intravenous antibiotics. Blood cultures on day 4 showed Elizabethkingia meningoseptica and Vancomycin was started. Follow-up cultures on days 6 and 14 grew Acinetobacter baumannii. A combination of Levofloxacin and Colistin was added, and blood cultures were negative after seven days, with clinical improvement. Elizabethkingia meningoseptica is a significant cause of hospital-acquired infections, especially in Neonatal Intensive Care Unit (NICU), leading to outbreaks. Clinicians must have a high degree of suspicion of E. meningoseptica for gram-negative bacilli causing sepsis and meningitis in high-risk patients. Recent technological advances have enabled accurate speciation to guide therapy and reduce morbidity and mortality rates.

New emerging materials with potential antibacterial activities.

The increasing prevalence of multidrug-resistant pathogens is a critical public health issue, necessitating the development of alternative antibacterial agents. Examples of these pathogens are methicillin-resistant Staphylococcus aureus (MRSA) and the emergence of "pan-resistant" Gram-negative strains, such as Pseudomonas aeruginosa and Acinetobacter baumannii, which occurred more recently. This review examines various emerging materials with significant antibacterial activities. Among these are nanomaterials such as quantum dots, carbon quantum dots, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and layered double hydroxides, all of which demonstrate excellent antibacterial properties. Interestingly, including antibacterial agents within the structure of these materials can help avoid bacterial resistance and improve the long-term efficacy of the materials. Additionally, the antibacterial potential of liquid solvents, including ionic liquids and both deep eutectic solvents and natural deep eutectic solvents, is explored. The review discusses the synthesis methods, advantages, and antibacterial efficacy of these new materials. By providing a comprehensive overview of these innovative materials, this review aims to contribute to the ongoing search for effective solutions to combat antibiotic resistance. Key studies demonstrating antibacterial effects against pathogens like Escherichia coli, Staphylococcus aureus, and multidrug-resistant strains are summarized. MOFs have exhibited antibacterial properties through controlled ion release and surface interactions. COFs have enhanced the efficacy of encapsulated antibiotics and displayed intrinsic antibacterial activity. Other nanomaterials, such as quantum dots, have generated reactive oxygen species, leading to microbial inactivation. This review aims to provide insights into these new classes of antibacterial materials and highlight them for addressing the global crisis of antibiotic resistance. KEY POINTS: • Nanomaterials show strong antibacterial effects against drug-resistant bacteria • Emerging solvents like ionic liquids offer novel solutions for bacterial resistance • MOFs and COFs enhance antibiotic efficacy, showing promise in combating resistance.

Neural network-based predictions of antimicrobial resistance phenotypes in multidrug-resistant Acinetobacter baumannii from whole genome sequencing and gene expression.

Whole genome sequencing (WGS) potentially represents a rapid approach for antimicrobial resistance genotype-to-phenotype prediction. However, the challenge still exists to predict fully minimum inhibitory concentrations (MICs) and antimicrobial susceptibility phenotypes based on WGS data. This study aimed to establish an artificial intelligence-based computational approach in predicting antimicrobial susceptibilities of multidrug-resistant Acinetobacter baumannii from WGS and gene expression data. Antimicrobial susceptibility testing (AST) was performed using the broth microdilution method for 10 antimicrobial agents. In silico multilocus sequence typing (MLST), antimicrobial resistance genes, and phylogeny based on cgSNP and cgMLST strategies were analyzed. High-throughput qPCR was performed to measure the expression level of antimicrobial resistance (AMR) genes. Most isolates exhibited a high level of resistance to most of the tested antimicrobial agents, with the majority belonging to the IC2/CC92 lineage. Phylogenetic analysis revealed undetected transmission events or local outbreaks. The percentage agreements between AMR phenotype and genotype ranged from 70.08% to 89.96%, with the coefficient of agreement (κ) extending from 0.025 and 0.881. The prediction of AST employed by deep neural network models achieved an accuracy of up to 98.64% on the testing data set. Additionally, several linear regression models demonstrated high prediction accuracy, reaching up to 86.15% within an error range of one gradient, indicating a linear relationship between certain gene expressions and the corresponding antimicrobial MICs. In conclusion, neural network-based predictions could be used as a tool for the surveillance of antimicrobial resistance in multidrug-resistant A. baumannii.

Threshold Modeling for Antibiotic Stewardship in Oman.

Antimicrobial stewardship supports rational antibiotic use. However, balancing access to antibiotic treatment while controlling resistance is challenging. This research used a threshold logistic modelling approach to identify targets for antibiotic usage associated with carbapenem-resistant Acinetobacter baumannii (CRAb), carbapenem-resistant Klebsiella pneumonia (CRKP), and extended-spectrum β-lactamases- producing Escherichia coli (ESBL-producing E. coli) incidence in hospitals. This study utilises an ecological population-level design. Monthly pathogen cases and antibiotic use were retrospectively determined for inpatients between January 2015 and December 2023. The hospital pharmacy and microbiology information systems were used to obtain this data. Thresholds were identified by applying nonlinear modelling and logistic regression. Incidence rates of 0.199, 0.175, and 0.146 cases/100 occupied bed-days (OBD) for CRAb, CRKP, and ESBL-producing E. coli, respectively, were determined as the cutoff values for high (critical) incidence rates. Thresholds for aminoglycosides (0.59 defined daily dose (DDD)/100 OBD), carbapenems (6.31 DDD/100 OBD), piperacillin-tazobactam (3.71 DDD/100 OBD), third-generation cephalosporins (3.71 DDD/100 OBD), and fluoroquinolones (1.91 DDD/100 OBD), were identified. Exceeding these thresholds would accelerate the gram-negative pathogens' incidence rate above the critical incidence levels. Employing the threshold logistic approach enabled near real-time performance monitoring feedback, risk scores and alert signals for when the incidence of the selected pathogens are entering critical levels. Threshold logistic models can help inform and implement effective antimicrobial stewardship interventions to manage resistance within hospital settings.