Comparative genomics and molecular epidemiology of colistin-resistant Acinetobacter baumannii

This study aimed to investigate the prevalence and resistance mechanisms of colistin-resistant Acinetobacter baumannii (ColRAB) isolates in Serbia, assess their genetic relatedness to other circulating A. baumannii isolates in the neighbouring European countries, and analyse the global genomic epidemiology of ColRAB isolates. A total of 784 isolates of A. baumannii were recovered from hospitalised patients in Serbia between 2018 and 2021. The antimicrobial susceptibility testing was performed using disk diffusion and broth microdilution. All ColRAB isolates were subjected to DNA isolation and whole-genome sequencing (WGS). Overall, 3.94 % (n = 30) isolates were confirmed as ColRAB. Results of mutational and transcriptional analysis of genes associated with colistin resistance indicate the central role of the two-component regulating system, PmrAB, and increased expression of the pmrC gene in ColRAB. Most of the isolates (n = 29, 96.6 %) belonged to international clone II, with the most common sequence type being ST^Pas2 (n = 23, 76.6 %). Based on the WGS analysis, ColRAB isolates belonging to the same ST isolated in various countries were grouped into the same clusters, indicating the global dissemination of several high-risk clonal lineages. Phylogenomic analysis of ColRAB isolates, together with all previously published A. baumannii genomes from South-Eastern European countries, showed that colistin resistance arose independently in several clonal lineages. Comparative genomic analysis revealed multiple genes with various roles (transcriptional regulation, transmembrane transport, outer membrane assembly, etc.), which might be associated with colistin resistance in A. baumannii. The obtained findings serve as the basis for further studies, contributing to a better understanding of colistin resistance mechanisms in A. baumannii.

Detection of carbapenemase genes in Klebsiella pneumoniae isolates

Introduction. Klebsiella pneumoniae is one of the leading causes of serious hospital-acquired infections worldwide among Enterobacteriaceae species. It is the most common producer of carbapenemases in many parts of the world. Objective. The aim of the study was to determine which enzymes were responsible for resistance to carbapenems in Klebsiella pneumoniae strains isolated at the Centre of Microbiology of Public Health Institute of Vojvodina. Methods. A total of 29 Klebsiella pneumoniae non-duplicated strains resistant to at least one carbapenem isolated from clinical samples of hospitalized patients between November 1st 2013 and April 30th 2014 were studied. The species identification and susceptibility were done using VITEK 2 (bioM?rieux, Marcy-l??toile, France) system. Phenotypic conformation of carbapenemase production was done by double-disc synergy test. PCR technique was performed for detection of genes encoding production of carbapenemases (blsKPC, blaVIM, bla NDM, blaOXA-48). Results. Isolates of Klebsiella pneumoniae resistant to at least one carbapenem showed positive on double- disc synergy test between meropenem and dipicolinic acid. All strains positive in phenotypic test contained blaNDM gene. In isolates resistant only to ertapenem, neither production of carbapenemases nor presence of genes encoding these enzymes were detected. Among these isolates, nine produced extended-spectrum ?-lactamase. Conclusion. The presence of NDM metallo-?-lactamase was determined in all Klebsiella pneumoniae isolates resistant to at least one carbapenem.

A Comprehensive Overview of Antibacterial Agents for Combating Multidrug-Resistant Bacteria: The Current Landscape, Development, Future Opportunities, and Challenges

Background/Objectives: Antimicrobial resistance poses a major public health challenge. The World Health Organization has identified 15 priority pathogens that require prompt development of new antibiotics. This review systematically evaluates the antibacterial resistance of the most significant bacterial pathogens, currently available treatment options, as well as complementary approaches for the management of infections caused by the most challenging multidrug-resistant (MDR) bacteria. For carbapenem-resistant Gram-negative bacteria, treatment options include combinations of beta-lactam antibiotics and beta-lactamase inhibitors, a novel siderophore cephalosporin, known as cefiderocol, as well as older antibiotics like polymixins and tigecycline. Treatment options for Gram-positive bacteria are vancomycin, daptomycin, linezolid, etc. Although the development of new antibiotics has stagnated, various agents with antibacterial properties are currently in clinical and preclinical trials. Non-antibiotic strategies encompass antibiotic potentiators, bacteriophage therapy, antivirulence therapeutics, antimicrobial peptides, antibacterial nanomaterials, host-directed therapy, vaccines, antibodies, plant-based products, repurposed drugs, as well as their combinations, including those used alongside antibiotics. Significant challenges exist in developing new antimicrobials, particularly related to scientific and technical issues, along with policy and economic factors. Currently, most of the alternative options are not part of routine treatment protocols. Conclusions and Future Directions: There is an urgent need to expedite the development of new strategies for treating infections caused by MDR bacteria. This requires a multidisciplinary approach that involves collaboration across research, healthcare, and regulatory bodies. Suggested approaches are crucial for addressing this challenge and should be backed by rational antibiotic use, enhanced infection control practices, and improved surveillance systems for emerging pathogens.

The emergence of multidrug-resistant bacteria causing healthcare-associated infections in COVID-19 patients - a retrospective multi-centre study

INTRODUCTION

We evaluated the prevalence, aetiologies and antibiotic resistance patterns of bacterial infections in hospitalized patients with laboratory-confirmed SARS-CoV-2. We also investigated comorbidities, risk factors, and the mortality rate in COVID-19 patients with bacterial infections.

METHODS

This retrospective observational study evaluated medical records of 7249 randomly selected patients with COVID-19 admitted to three clinical centres between January 1 2021 and February 16, 2022. A total of 6478 COVID-19 patients met the eligibility criteria for analysis.

RESULTS

The mean age of the patients with SARS-CoV-2 and bacterial infections was 68.6 ± 15.5 years (range: 24 to 94 years). The majority of patients (68.7%) were older than 65 years. The prevalence of bacterial infections among hospitalized COVID-19 patients was 12.9%, most of them being hospital-acquired (11.5%). Bloodstream (37.7%) and respiratory tract infections (25.6%) were the most common bacterial infections. Klebsiella pneumoniae and Acinetobacter baumannii caused 25.2% and 23.6% of all bacterial infections, respectively. Carbapenem-resistance in Enterobacterales, A. baumannii, and Pseudomonas aeruginosa were 72.6%, 93.7%, and 69.1%. Age >60 years and infections caused by ≥3 pathogens were significantly more prevalent among deceased patients compared to survivors (p<0.05). Furthermore, 95% of patients who were intubated developed ventilator-associated pneumonia. The overall in-hospital mortality rate of patients with SARS-CoV-2 and bacterial infections was 51.6%, while 91.7% of patients who required invasive mechanical ventilation died.

CONCLUSIONS

Our results reveal a striking association between healthcare-associated bacterial infections as an important complication of COVID-19 and fatal outcomes.