Search Results (1,354)

Multi-drug resistance in Acinetobacter baumannii poses a significant human health threat. For multidrug-resistant pathogens, ‘last line of defense’ antibiotics like the polymyxins are implemented. Concerningly, polymyxin-resistance is evidenced in Acinetobacter baumannii and is mediated by the PmrAB two-component system. The response regulator PmrA upregulates pmrC, leading to lipooligosaccharide modifications that reduce polymyxin binding. Sequencing of A. baumannii resistant isolates has identified point mutations in the receiver domain of PmrA that correlate with increased resistance. To investigate functional impacts of these mutations, we characterized five PmrA mutations (D10N, M12I, I13M, G54E, and S119T) by assessing changes in PmrA DNA-binding affinity, dimerization, phosphorylation, and structure. Our findings suggest that these mutations impact the ability of PmrA to receive the activating phosphoryl group from the sensor kinase PmrB. The slow phosphoryl uptake is likely due to (1) disruption of the PmrB-PmrA interaction by interfering with the recognition site on PmrA, or (2) perturbation of PmrA’s active site via steric hindrance or displacement of residues and ions necessary for coordination within the aspartic acid pocket. Slowed phosphorylation of a response regulator can lead to enhanced gene transcription through several mechanisms. These insights advance our understanding of PmrA-mediated resistance in A. baumannii. Full article

Acinetobacter baumanni (A. baumannii) is a well-known pathogen associated with antimicrobial-resistant infections. It is a major cause of nosocomial infections and is frequently associated with polymicrobial and antibiotic-resistant infections. This study investigates the frequency of A. baumannii infections, its antimicrobial resistance profile and the main co-pathogens isolated in respiratory samples at the San Giovanni di Dio e Ruggi d’Aragona Hospital in 2015–2019 (pre-COVID-19 pandemic) and 2020–2023 (during/post-COVID-19 pandemic). Bacterial identification and antibiotic susceptibility testing were performed using the VITEK^® 2 system (2015–2019), while identification was carried out with MALDI-TOF MS starting from 2020. A total of 1679 strains were isolated between 2015 and 2019, and 1186 between 2020 and 2023, with significantly higher frequencies in males 61–80 and females 71–80. A. baumannii was isolated predominantly from respiratory specimens, derived predominantly in intensive care units (ICUs). The antimicrobial resistance rates of A. baumannii were above 90% for gentamicin, trimethoprim/sulfamethoxazole, imipenem and ciprofloxacin, while colistin resistance was less than 1% (0.95%) in pre-pandemic and alarmingly increased during/post pandemic period (6.1%). A. baumannii was most frequently associated with Klebsiella pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa in respiratory tract infections. A. baumannii represents a serious global health threat due to its extensive antimicrobial resistance, highlighting the need for continuous surveillance, detailed strain characterization, and development of new antimicrobial agents. Full article

This study developed a rapid and reliable SYBR-Green semiplex PCR assay for simulta-neous detection of major carbapenem resistance genes in Klebsiella pneumoniae and Acinetobacter baumannii. Two primer sets were used: one to detect blaKPC, blaNDM-1, and blaOXA-48 genes in K. pneumoniae and blaOXA-23 in A. baumannii, and another to amplify conserved 16S rRNA gene regions as internal controls. The intra- and inter-assay coeffi-cient of variation ranged from 0.03% to 3.8%. Standard curves exhibited excellent linearity across six logarithmic scales (10¹–10⁶ DNA copies/µL), with detection limits of 10–10² DNA copies/mL. Melting temperatures (Tm) were: 88.85 °C (KPIC), 90.65 °C (NDM-1), 89.45 °C (KPC), 84.23 °C (OXA-48), 87.81 °C (OXA-23), and 80.67 °C (ABIC). The SYBR-Green Semiplex PCR assay offers a rapid (65 min turnaround), cost-effective, and sensitive method for early detection of carbapenem-resistant pathogens, enabling timely targeted therapy and improved infection control by potentially reducing empirical antibiotic use before culture confirmation. Full article

Multidrug-resistant (MDR) bloodstream infections (BSIs) constitute a major challenge in intensive care units, with the COVID-19 pandemic compromising infection control and potentially increasing MDR incidence. Comparative data between COVID and non-COVID ICU populations remain limited. The MARTINI study is a retrospective observational analysis held in a tertiary hospital during the COVID-19 pandemic (2020–2022) encompassing adult patients with MDR BSIs admitted to COVID and non-COVID ICUs. Demographics, comorbidities, severity scores, microbiology, resistance patterns, and outcomes were accessed and compared. A binary logistic regression model and multivariate regression was performed to identify independent predictors of ICU mortality. Among the study’s 156 patients (106 COVID-ICU, 50 non-COVID-ICU), COVID-ICU patients were significantly older with higher comorbidity and severity scores. Gram-negative pathogens predominated in both cohorts, mainly Acinetobacter baumannii and Klebsiella pneumoniae, with comparable resistance mechanisms. Timing of bacteremia onset and initiation of appropriate therapy did not differ between groups. However, ICU mortality was markedly higher in COVID-ICU patients (74.5% vs. 38%, p < 0.001). Age, SOFA score, the presence of systemic inflammation (SIRS) and COVID-19 infection were identified as independent predictors of mortality. Although pathogen distribution and resistance were similar across groups, COVID-ICU patients experienced significantly poorer outcomes. Strengthened infection control and timely and targeted antimicrobial therapy are essential to diminish MDR bacteremia risk in critically ill populations. Full article

Background: Antibiotic resistance is a significant health problem in healthcare settings, especially intensive care units (ICUs), where patients are critically ill. This study aims to identify the bacterial profile and antibiotic resistance patterns of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter, and Escherichia coli (ESKAPEE) in blood specimens collected from adult patients admitted to the ICUs of public hospitals in Abu Dhabi, United Arab Emirates. The World Health Organization lists these pathogens as priority pathogens that greatly threaten humans. Methods: This cross-sectional study used routinely collected data through the AMR surveillance system between 2018 and 2022. Results: A total of 838 culture-positive blood specimens were reported during the study period, and 965 ESKAPEE pathogens were isolated. The most frequently isolated bacteria were Klebsiella pneumoniae (31%), Escherichia coli (22%), and Staphylococcus aureus (20%). Acinetobacter baumannii exhibited high resistance to Amikacin (81%), Meropenem (72%), and Imipenem (87%). Escherichia coli demonstrated resistance to Imipenem (42%) and Cefotaxime (54%). Klebsiella pneumoniae showed resistance to Imipenem (37%) and Cefotaxime (39%). Staphylococcus aureus showed resistance to Penicillin G (80%), Oxacillin (4%), and Ciprofloxacin (54%). Conclusions: The study showed a high prevalence of resistance in the most frequently isolated ESKAPEE pathogens in adult ICU patients. This brings into focus the need for appropriate infection control measures and strong antibiotic stewardship programs. The findings of the study support the ongoing efforts to deploy a better diagnostic tool for rapid pathogen identification, which is key in the targeted management of patients with bloodstream infection, especially in ICUs. Full article

Ventilator-associated pneumonia (VAP) is one of the most common hospital-acquired infections. Several studies have explored the potential role of the lung microbiome as a biomarker for identifying and predicting the prognosis of VAP. However, research on the respiratory microbiome in individuals with VAP caused by carbapenem-resistant Acinetobacter baumannii (CRAB) remains limited. Therefore, we aimed to analyze the respiratory microbiome of patients with CRAB VAP. Respiratory specimens were collected from patients who developed CRAB VAP. Microbiome diversity and composition were analyzed using 16S rRNA gene pyrosequencing. Patients were categorized into two groups based on mortality outcomes: intensive care unit (ICU) mortality or 28-day mortality after ICU discharge. Twenty patients with CRAB VAP were enrolled, including nine in the mortality group. No significant differences were observed in α-diversity indices between the study groups. However, multivariable Firth’s logistic regression revealed a significant association between a relative abundance of the Enterococcus genus ≥ 1% and mortality outcomes (odds ratio: 0.06; 95% confidence interval: 0.00–0.771; p = 0.029). This study characterized the respiratory microbiome of patients with CRAB VAP and highlighted the potential role of microbiome analysis in predicting disease prognosis. Further studies with larger sample sizes are warranted to validate these findings. Full article

The global spread of carbapenem-resistant Acinetobacter baumannii (CRAB) poses a severe public health threat, driving growing interest in phage-based precision antibacterial strategies. This systematic review synthesizes recent advances in the field of A. baumannii phage. Modern taxonomy, based on whole-genome phylogeny, has reclassified the majority of A. baumannii phages into the class Caudoviricetes, revealing distinct evolutionary clades that correlate with host tropism and biological properties, superseding the traditional morphological families (Myoviridae, Siphoviridae, Podoviridae). To overcome limitations of natural phage therapy, such as narrow host range, cocktail therapies (ex vivo resistance mutation rates < 5%) and phage-antibiotic synergism (enabling antibiotic efficacy at 1/4 minimum inhibitory concentration) have significantly enhanced antibacterial efficacy. Preclinical models demonstrate that phage therapy efficiently clears pathogens in pneumonia models and promotes the healing of burn wounds and diabetic ulcers via immunomodulatory mechanisms. Technical optimizations include nebulized inhalation delivery achieving 42% alveolar deposition, and thermosensitive hydrogels enabling sustained release over 72 h. Genetic engineering approaches, such as host range expansion through tail fiber recombination and CRISPR/Cas-mediated elimination of lysogeny, show promise. However, the genetic stability of engineered phages requires further validation. Current challenges remain, including limited host spectrum, the absence of clinical translation standards, and lagging regulatory frameworks. Future efforts must integrate metagenomic mining and synthetic biology strategies to establish a precision medicine framework encompassing resistance monitoring and personalized phage formulation, offering innovative solutions against CRAB infections. Full article

Background: Acinetobacter baumannii (A. baumannii), a critical nosocomial pathogen, poses a significant threat in intensive care units (ICUs) due to its multidrug-resistant (MDR) strains. This study systematically reviews and performs a meta-analysis on the prevalence and antibiotic resistance profiles of MDR A baumannii (MDR-A. baumannii) in ICU patients in Saudi Arabia. Methods: A comprehensive search in PubMed, Saudi Digital Library, Scopus, and Web of Science, focusing on studies from January 2014 to September 2025, was performed. The present study followed the reporting guidelines of Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA-2020). Data on study characteristics, sample sizes, patient demographics, prevalence of MDR-AB, and antibiotic resistance profiles were extracted and analyzed. Quality assessment was conducted using the Joanna Briggs Institute. Results: The prevalence of MDR-AB in ICU patients varied significantly across studies, with retrospective studies reporting rates from 3.37% to 69% and prospective studies ranging from 3.9% to 72.73%. Colistin remained highly effective, showing 100% susceptibility in some studies. Meanwhile, resistance to carbapenems like imipenem and meropenem often exceeds 50%. Additional antibiotics with notable resistance included gentamicin, tigecycline, ampicillin/sulbactam, trimethoprim-sulfamethoxazole, ceftazidime, piperacillin/tazobactam, and third-generation cephalosporins. Mechanisms of resistance frequently involved OXA-type carbapenemases, particularly OXA-23. While OXA-23 was the most frequently detected carbapenemase, recent genomic data have also revealed the presence of metallo-β-lactamases, such as IMP-type genes, in ICU isolates. Conclusions: MDR-A. baumannii poses a substantial challenge in Saudi Arabian ICUs, with high prevalence and significant resistance to commonly used antibiotics. The results highlight the critical need for continuous monitoring, cautious antibiotic stewardship, and strict infection control methods to manage and lessen the effects of MDR-AB in ICUs. Full article

Severely burned patients are at high risk of local and systemic infections due to skin barrier loss. Their clinical management is complex and requires coordinated intensive care and infection prevention strategies. Diagnosing infective endocarditis (IE) in this population is particularly difficult due to overlapping symptoms and limited diagnostic specificity. Common pathogens include Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. We conducted a retrospective cohort study on 543 patients with burns affecting >18% of total body surface area (TBSA), admitted to our Burn Intensive Care Unit (BICU) from 2019 to 2024. The incidence of infective endocarditis was 1.47%, involving aortic (75%), mitral (12.5%), and tricuspid (12.5%) valves. Pathogens identified included S. aureus, Klebsiella pneumoniae, A. baumannii, and P. aeruginosa. This incidence is significantly higher than that in the general population. Mortality reached 50%, with an overall 3-month mortality of 75%. The literature on IE in burn patients is scarce, and the role of antibiotic prophylaxis remains controversial. Infective endocarditis in burn patients, although rare, represents a severe complication with high mortality. Early diagnosis and coordinated multidisciplinary care are essential to improve patient outcomes. Full article

Introduction: Carbapenem-resistant Gram-negative bacteria (CR-GNB) are rapidly spreading pathogens that increase morbidity and mortality in hospital settings and significantly restrict available treatment options worldwide. The lack of molecular epidemiological data and the limited use of next-generation sequencing (NGS) in South Lebanon have hindered comprehensive surveillance efforts. This study represents the first molecular characterization of CR-GNB in this region. Methods: A total of 477 clinical Gram-negative bacterial isolates were collected from intensive care unit (ICU) patients admitted to various hospitals in South Lebanon in 2023. Of these, 131 CR-GNB were subjected to whole-genome sequencing using the Illumina MiSeq platform. K-mer-based species identification, multilocus sequence typing (MLST), antimicrobial resistance (AMR) gene profiling, and plasmid analysis were performed using multiple bioinformatic tools. Phylogenetic analysis was conducted using SaffronTree. Results: K-mer-based identification revealed that the predominant species among CR-GNB isolates were Pseudomonas spp. and Escherichia coli (26.7% each), followed by Klebsiella pneumoniae (19.8%), Acinetobacter baumannii (17.6%), Proteus mirabilis (4.6%), Enterobacter cloacae (2.3%), Achromobacter spp. (1.5%), and Citrobacter freundii (0.8%). Based on antimicrobial susceptibility testing, isolates were classified as follows: 0.8% as pan drug-resistant (PDR), 40.5% as extensively drug-resistant (XDR), and 52.7% as multidrug-resistant (MDR) and 6.1% as antimicrobial-resistant (AMR). All isolates harbored AMR genes, with the following distribution: 2% bla_VIM, 5% bla_NDM-1, 27% bla_NDM-5, 65% bla_OXA-type, and 1% bla_DIM-1. Plasmid-associated AMR genes were detected in 58% of isolates; among these, 96% carried Inc-family plasmids, 57% Col plasmids, and 11% replication-associated elements (rep). Phylogenetic analysis demonstrated that certain isolates exhibited both hospital-specific and shared genetic profiles, indicating widespread dissemination across multiple healthcare facilities, as well as evidence of local emergence and ongoing transmission. Conclusions: The high prevalence of CR-GNB harboring resistance genes and plasmids underscores the urgent need for NGS-based genomic surveillance in South Lebanon. Implementing such strategies is essential for tracking resistance genes, identifying clonal outbreaks, and guiding effective infection control interventions to mitigate the spread of CR-GNB. Full article

Background/Objectives: Gram-negative bacteria with acquired carbapenem resistance have become increasingly common in serious infections. This study aimed to evaluate the in vitro activity of cefiderocol against multidrug-resistant Gram-negative clinical isolates collected from a tertiary care hospital in Romania. Methods: A retrospective study (November 2024–February 2025) involving 89 consecutive Multi-Drug Resistant (MDR) Gram-negative isolates, 66 Enterobacterales and 23 non-fermenters (P. aeruginosa, S. maltophilia, A. baumannii), was conducted. Results: Overall, 52.8% of Enterobacterales and P. aeruginosa isolates were susceptible to cefiderocol, with higher susceptibility among Enterobacterales alone (63.6%). Using disk diffusion, 66.3% of all isolates were classified as susceptible to the antibiotic. K. pneumoniae isolates co-harboring NDM and OXA-48 were susceptible in 65.3% of cases, while NDM-only producers were resistant. All P. aeruginosa isolates tested were susceptible to the antibiotic. Susceptibility rates in A. baumannii were lower (68.8%), with variability between testing methods. Conclusions: The presence of NDM-producing isolates with complete resistance to cefiderocol in our study highlights the risk that resistance may spread rapidly once the drug becomes widely used. Cefiderocol may be an effective option for treating MDR bacterial infections, but strict microbiological monitoring remains essential. Full article

Background and Objectives: Changes in the incidence of healthcare-associated infections (HAIs) during the coronavirus disease 2019 (COVID-19) pandemic and during periods with fewer or more COVID-19 cases have been inconclusively studied. Compared with 2015, in 2019, the abundances of the microorganisms Klebsiella pneumoniae and Enterococcus faecium increased in intensive care units (ICUs) in Taiwan. The trend in the incidence of HAIs in ICUs in Taiwan during the emergence of new infectious diseases is worth studying. Materials and Methods: We surveyed the incidence densities of different types of HAIs, device-associated HAIs, pathogens, and antimicrobial resistance in a dataset from the Taiwan Healthcare-associated Infection and Antimicrobial Resistance Surveillance System from 2015 to 2022. The change in incidence density trends was evaluated via Poisson regression, and the change in proportion trends was checked via the Mantel–Haenszel chi-square test. Results: The incidence of HAIs decreased from 5.7 to 5.17 episodes per 1000 person-days from the pre-COVID-19 period to the post-COVID-19 period. The incidences of healthcare-acquired pneumonia (HAP), device-associated HAIs decreased. However, the incidences of bloodstream infections (BSIs) increased. The percentages of patients with Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii infections significantly decreased. The percentage of patients with methicillin-resistant Staphylococcus aureus (MRSA) infection decreased, but that of patients with carbapenem-resistant K. pneumoniae (CRKP), carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa, and vancomycin-resistant Enterococcus faecium infections increased. The antimicrobial consumption related to CRKP increased and MRSA decreased. Conclusions: Overall, HAIs, HAP, and VAP decreased in incidence after the COVID-19 pandemic. These results revealed decreases in MRSA infection incidence under infection control protocols with more antimicrobial use. However, the proportion of CRKP among HAIs increased with broad-spectrum antimicrobial agent use. Based on the recent incidence of HAIs in ICUs, the quality of infection control in medical units can be enhanced to decrease HAI incidence. Full article

Two-component systems (TCSs) in bacteria are often involved in the global regulation of various physiological activities and behaviours. This study investigated the GacSA TCS and DJ41_1407 transcriptional sensor adjacent to GacA in Acinetobacter baumannii ATCC 19606. The relationship between GacS, GacA, and DJ41_1407 and their functions and signal transduction mechanisms are described. A. baumannii ATCC 19606 mutants, ∆gacS, ∆gacA, and ∆DJ41_1407, were generated using markerless mutation and cultured in LB medium, then collected for RNA sequencing. It was found that GacS, GacA, and DJ41_1407 regulate a series of genes involved in carbon metabolism. Quantitative reverse transcription PCR (qRT-PCR) results showed that DJ41_1407 and GacA may regulate the expression of adh4, ipdC, iacH, and paa. Phos-tag™ results revealed that GacS plays a more significant role in GacA phosphorylation. GacA regulated colony size and growth conditions in rich medium. Compared to the wild-type strain, the ∆gacA and ∆gacSA mutants exhibited smaller colony sizes, and mutation of the gacS, gacA, and DJ41_1407 genes also reduced bacterial virulence as determined by the Galleria mellonella infection assay. GacA also plays a crucial role in modulating antibiotic resistance, and the ∆gacA∆DJ41_1407 mutant demonstrated greater susceptibility to antibiotics. These results highlight the multiple functions regulated by the GacSA global TCS in A. baumannii ATCC 19606. Full article

Acinetobacter baumannii is a critical public health threat, particularly with the rise in multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains that limit treatment options. Phage therapy, which uses bacteriophages to target bacteria, offers a promising alternative. We isolated an XDR strain (Ab125) from a burn wound infection and screened 34 phages, identifying vB_AbaM_3098 as the only effective candidate. However, resistance rapidly emerged, producing a derivative strain (Ab139). Interestingly, Ab139, though resistant to vB_AbaM_3098, became susceptible to six previously inactive phages. While various potential determinants were identified through comparative genomics and proteomics, the mechanism causing phage resistance to vB_AbaM_3098 and simultaneous susceptibility to other phages remains to be elucidated. Among the six new candidates, vB_AbaM_3014 was the most promising. While each phage alone allowed bacterial regrowth, combining vB_AbaM_3098 and vB_AbaM_3014 completely suppressed Ab125 growth. In a Galleria mellonella infection model, this cocktail achieved 90% survival after five days compared to 0% in untreated controls. Notably, the cocktail combined one phage with modest activity and another inactive phage against the parental strain; together, they produced strong bactericidal effects. These findings highlight both the complexity of phage cocktail design and their promise as adjunct therapies against drug-resistant A. baumannii. Full article

Background/Objectives: Antimicrobial resistance (AMR) remains a major global threat, with the COVID-19 pandemic influencing its dynamics, although its overall impact remains uncertain. This study analyzed seven-year AMR trends, including the pandemic period, in a tertiary care hospital in Greece that served as a COVID-19 referral center. Methods: Multiresistant bacteria isolated from all biological specimens of hospitalized patients between January 2018 and December 2024 were recorded and classified as multidrug- (MDR), extensively drug- (XDR), or pandrug-resistant (PDR). Overall AMR was defined as the sum of these categories. Annual incidences of overall AMR, its categories, and predominant Gram-negative (A. baumannii, K. pneumoniae, P. aeruginosa) and Gram-positive [methicillin-resistant S. aureus (MRSA), vancomycin-resistant Enterococcus (VRE)] pathogens were analyzed for the entire hospital and by sector (medical, intensive care unit [ICU], surgical). Bloodstream infection (BSI) AMR was also evaluated. Trend analysis was performed using Joinpoint regression. Results: Overall AMR exhibited a transient peak around 2021 across the hospital, except in the surgical sector. A significant rise in average annual percentage change (AAPC) occurred only in the medical sector (p < 0.001). PDR incidence increased hospital-wide (p < 0.001). K. pneumoniae, P. aeruginosa, MRSA, and VRE rose significantly in the medical sector, whereas ICU incidences remained largely stable despite the 2021 peak. A. baumannii showed no significant change. BSI-related AMR increased in the medical sector (p < 0.001) but not in the ICU (p = 0.2). Conclusions: Although overall AMR did not rise uniformly, PDR organisms increased hospital-wide. These findings support updating empiric therapy guidelines, reinforcing infection prevention measures, and translating surveillance data into targeted stewardship actions to enhance patient care. Full article