Acinetobacter baumannii: insights towards a comprehensive approach for the prevention of outbreaks in health-care facilities

Novel Leech Antimicrobial Peptides, Hirunipins: Real-Time 3D Monitoring of Antimicrobial and Antibiofilm Mechanisms Using Optical Diffraction Tomography

Antimicrobial peptides (AMPs) are promising agents for treating antibiotic-resistant bacterial infections. Although discovering novel AMPs is crucial for combating multidrug-resistant bacteria and biofilm-related infections, their clinical potential relies on precise, real-time evaluation of efficacy, toxicity, and mechanisms. Optical diffraction tomography (ODT), a label-free imaging technology, enables real-time visualization of bacterial morphological changes, membrane damage, and biofilm formation over time. Here, a computational analysis of the leech transcriptome using an advanced AI-based peptide screening strategy with ODT to identify potential AMPs is employed. Among the 19 potential AMPs identified, hirunipin 2 demonstrates potent antibacterial activity, low mammalian cytotoxicity, and minimal hemolytic effects. It demonstrates efficacy comparable to melittin, resistance to physiological salts and human serum, and a low likelihood of inducing bacterial resistance. Microscopy and 3D-ODT confirm its disruption of bacterial membranes and intracellular aggregation, leading to cell death. Notably, hirunipin 2 effectively inhibits biofilm formation, eradicates preformed biofilms, and synergizes with antibiotics against multidrug-resistant Acinetobacter baumannii (MDRAB) by enhancing membrane permeability. Additionally, hirunipin 2 significantly suppresses pro-inflammatory cytokine expression in LPS-stimulated macrophages, highlighting its anti-inflammatory properties. These findings highlight hirunipin 2 as a strong candidate for developing novel antibacterial, anti-inflammatory, and antibiofilm therapies, particularly against multidrug-resistant bacterial infections.

Challenges Facing Two Outbreaks of Carbapenem-Resistant Acinetobacter baumannii: From Cefiderocol Susceptibility Testing to the Emergence of Cefiderocol-Resistant Mutants

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with poor outcomes depending on patient's conditions, clinical severity and type of infection, and treatment is challenging given the limited therapeutic options available. The aim of this study was to describe the clinical and microbiological characteristics of two outbreaks caused by CRAB in an intensive care unit (ICU). In addition, the mechanisms of resistance detected in these strains and the treatment chosen according to the available therapeutic options were analyzed. Overall, 28 patients were included. Ten patients (35.71%) had ventilator-associated pneumonia (VAP), ten (35.71%) had a bloodstream infection (BSI), and eight (28.57%) were only colonized. Recurrent infection occurred in 25% (5/20) of infected patients. Two different strains of A. baumannii were isolated from the index patient of the first outbreak. The first strain belonged to the ST85 and carried the blaNDM-1 carbapenemase gene, while the second belonged to the ST2 and carried blaOXA-23, and blaOXA-66 carbapenemase genes. The phylogenetic analysis revealed that the ST2 strain was the cause of the major outbreak, and mutations in the AmpC gene were related to progressive increasing minimum inhibitory concentration (MIC) and finally, cefiderocol-resistance in one strain. The CRAB isolates from the second outbreak were also identified as ST2. Cefiderocol-resistant strains tests identified by the disc diffusion method were involved in 24% (6/25) of nosocomial infections. Using broth microdilution (BMD) ComASP® only, 33.3% (2/6) of these strains were cefiderocol-resistant. All-cause ICU mortality was 21.4%. Conclusions: Cefiderocol is the first approved siderophore cephalosporin for the treatment of CRAB infections. Cefiderocol-resistant strains were related with blaNDM-1 carbapenemase and mutations in the AmpC gene. Cefiderocol-resistant strains or that cannot be properly interpreted by disk diffusion, should be retested using BMD for definitive categorization.

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.

Genomic Surveillance Uncovers a 10-Year Persistence of an OXA-24/40 Acinetobacter baumannii Clone in a Tertiary Hospital in Northern Spain

Infections caused by carbapenem-resistant Acinetobacter baumannii are a global threat causing a high number of fatal infections. This microorganism can also easily acquire antibiotic resistance determinants, making the treatment of infections a big challenge, and has the ability to persist in the hospital environment under a wide range of conditions. The objective of this work was to study the molecular epidemiology and genetic characteristics of two blaOXA24/40Acinetobacter baumannii outbreaks (2009 and 2020-21) at a tertiary hospital in Northern Spain. Thirty-six isolates were investigated and genotypically screened by Whole Genome Sequencing to analyse the resistome and virulome. Isolates were resistant to carbapenems, aminoglycosides and fluoroquinolones. Multi-Locus Sequence Typing analysis identified that Outbreak 1 was mainly produced by isolates belonging to ST3Pas/ST106Oxf (IC3) containing blaOXA24/40, blaOXA71 and blaADC119. Outbreak 2 isolates were exclusively ST2Pas/ST801Oxf (IC2) blaOXA24/40, blaOXA66 and blaADC30, the same genotype seen in two isolates from 2009. Virulome analysis showed that IC2 isolates contained genes for capsular polysaccharide KL32 and lipooligosacharide OCL5. A 8.9 Kb plasmid encoding the blaOXA24/40 gene was common in all isolates. The persistance over time of a virulent IC2 clone highlights the need of active surveillance to control its spread.

International Clones of High Risk of Acinetobacter Baumannii-Definitions, History, Properties and Perspectives

Acinetobacter baumannii is a Gram-negative coccobacillus with exceptional survival skills in an unfavorable environment and the ability to rapidly acquire antibiotic resistance, making it one of the most successful hospital pathogens worldwide, representing a serious threat to public health. The global dissemination of A. baumannii is driven by several lineages named 'international clones of high risk' (ICs), two of which were first revealed in the 1970s. Epidemiological surveillance is a crucial tool for controlling the spread of this pathogen, which currently increasingly involves whole genome sequencing. However, the assignment of a particular A. baumannii isolate to some IC based on its genomic sequence is not always straightforward and requires some computational skills from researchers, while the definitions found in the literature are sometimes controversial. In this review, we will focus on A. baumannii typing tools suitable for IC determination, provide data to easily determine IC assignment based on MLST sequence type (ST) and intrinsic blaOXA-51-like gene variants, discuss the history and current spread data of nine known ICs, IC1-IC9, and investigate the representation of ICs in public databases. MLST and cgMLST profiles, as well as OXA-51-like presence data are provided for all isolates available in GenBank. The possible emergence of a novel A. baumannii international clone, IC10, will be discussed.

A Natural Virucidal and Microbicidal Spray Based on Polyphenol-Iron Sols

Numerous disinfection methods have been developed to reduce the transmission of infectious diseases that threaten human health. However, it still remains elusively challenging to develop eco-friendly and cost-effective methods that deactivate a wide range of pathogens, from viruses to bacteria and fungi, without doing any harm to humans or the environment. Herein we report a natural spraying protocol, based on a water-dispersible supramolecular sol of nature-derived tannic acid (TA) and Fe3+, which is easy-to-use and low-cost. Our formulation effectively deactivates viruses (influenza A viruses, SARS-CoV-2, and human rhinovirus) as well as suppressing the growth and spread of pathogenic bacteria (Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Acinetobacter baumannii) and fungi (Pleurotus ostreatus and Trichophyton rubrum). Its versatile applicability in a real-life setting is also demonstrated against microorganisms present on the surfaces of common household items (e.g., air filter membranes, disposable face masks, kitchen sinks, mobile phones, refrigerators, and toilet seats).

Copper-coated hospital surfaces: reduction of total bacterial loads and resistant Acinetobacter spp

Healthcare-associated infections (HAIs) represent a global challenge and an even more staggering concern when related to microorganisms capable of resisting and surviving for long periods in the environment, such as Acinetobacter spp. Strategies that allow a reduction of pathogens from hospital environments represent an additional barrier in infection control protocols, minimizing transmission to hospitalized patients. Considering the antimicrobial properties of copper, here, the bacterial load and the presence of Acinetobacter spp. were monitored on high handling surfaces covered by 99.9% copper films on intensive and non-intensive care unit bedrooms in a tertiary care hospital. Firstly, copper-coated films were able to inhibit the adhesion and biofilm formation of A. baumannii strains in in vitro assays. On the other hand, Acinetobacter spp. were isolated from both copper-coated and uncoated surfaces in the hospital, although the majority was detected on surfaces without copper. All carbapenem-resistant A. baumannii isolates identified harbored the blaoxa-23 gene, while the A. nosocomialis isolates were susceptible to most antimicrobials tested. All isolates were susceptible to polymyxin B. Regarding the total aerobic bacteria, surfaces with copper-coated films presented lower total loads than those detected for controls. Copper coating films may be a workable strategy to mitigate HAIs, given their potential in reducing bacterial loads in nosocomial environments, including threatening pathogens like A. baumannii.

Antimicrobial activity of natural products against MDR bacteria: A scientometric visualization analysis

Objective: A growing number of studies have demonstrated the antimicrobial activity of natural products against multidrug-resistant bacteria. This study aimed to apply scientometric method to explore the current status and future trends in this field.

Methods: All relevant original articles and reviews for the period 1997–2021 were retrieved from the Web of Science Core Collection database. VOSviewer, a scientometric software, and an online bibliometric analysis platform were used to conduct visualization study.

Results: A total of 1,267 papers were included, including 1,005 original articles and 262 reviews. The United States and India made the largest contribution in this field. The University of Dschang from Cameroon produced the most publications. Coutinho HDM, Kuete V, and Gibbons S were key researchers, as they published a great many articles and were co-cited in numerous publications. Frontiers in Microbiology and Antimicrobial Agents and Chemotherapy were the most influential journals with the highest number of publications and co-citations, respectively. “Medicinal plants”, “methicillin-resistant Staphylococcus aureus”, “biofilm”, “minimum inhibitory concentration”, and “efflux pumps” were the most frequently used keywords, so these terms are presumed to be the current hot topics. All the included keywords could be roughly divided into four major themes, of which the theme of “natural product development approach” had attracted much attention in recent years. Furthermore, “Pseudomonas aeruginosa”, “nanoparticles”, “green synthesis”, “antimicrobial peptides”, “antibiofilm”, “biosynthetic gene clusters”, and “molecular dynamics simulation” had the latest average appearance year, indicating that these topics may become the research hot spots in the coming years.

Conclusion: This study performed a scientometric analysis of the antibacterial activity of natural products against multidrug-resistant bacteria from a holistic perspective. It is hoped to provide novel and useful data for scientific research, and help researchers to explore this field more intuitively and effectively.