Search Results (35)

Colistin has re-emerged as a last-resort antibiotic for treating infections caused by multidrug-resistant (MDR) Gram-negative bacilli (GNB). However, increasing resistance threatens its efficacy. This study aimed to evaluate colistin resistance trends among clinical isolates of Gram-negative bacilli isolated over a five-year period at a large Emergency Hospital in North-Eastern Romania. A total of 23,143 GNB strains were isolated during the study period, including 14,531 Enterobacterales and 8294 non-fermenting Gram-negative bacilli. The percentage of colistin-resistant strains among those analyzed was 3.98%. Species-specific analysis focused on Klebsiella spp., Escherichia coli, Enterobacter spp., Citrobacter spp., Pseudomonas spp., and Acinetobacter spp. Klebsiella spp. exhibited the highest prevalence of colistin resistance, accounting for over 80% of all colistin-resistant strains, with annual resistance rates fluctuating between 12.97% and 21.64%. Colistin resistance among E. coli was low (0.18–1.25%). Citrobacter spp. showed no resistance in the last three years of the study, and Enterobacter spp. maintained relatively stable resistance (3–5%). Resistance in Pseudomonas spp. remained below 1%, while Acinetobacter spp. showed a resistance rate of 5.43%. Several distinct resistance phenotypes were identified among Klebsiella spp., Pseudomonas spp., and Acinetobacter spp. strains, reflecting both endemic and sporadic circulation patterns. The study highlights a persistent presence of colistin resistance, especially in Klebsiella spp., underlining the importance of ongoing surveillance. Despite low resistance in other species, the emergence of resistant strains underscores the need for robust antimicrobial stewardship and infection control policies. Full article

In recent years, one of the most important issues in public health is the rapid growth of antibiotic resistance among pathogens. Multidrug-resistant (MDR) strains (mainly Enterobacteriaceae and non-fermenting bacilli) cause severe infections, against which commonly used pharmaceuticals are ineffective. Therefore, there is an urgent need for new treatment options and drugs with innovative mechanisms of action. Natural compounds, especially alkaloids, are showing promising potential in this area. This review focuses on the ability of the isoquinoline alkaloid berberine (BRB) to overcome various resistance mechanisms against conventional antimicrobial agents. BRB has demonstrated significant activity in inhibiting efflux pumps of the RND (Resistance-Nodulation-Cell Division) family, such as MexAB-OprM (P. aeruginosa) and AdeABC (A. baumannii). Moreover, BRB was able to decrease quorum sensing activity in both Gram-positive and Gram-negative pathogens, resulting in reduced biofilm formation and lower bacterial virulence. Additionally, BRB has been identified as a potential inhibitor of FtsZ, a key protein responsible for bacterial cell division. Particularly noteworthy, though requiring further investigation, are reports suggesting that BRB might inhibit β-lactamase enzymes, including NDM, AmpC, and ESβL types. The pleiotropic antibacterial actions of BRB, distinct from the mechanisms of traditional antibiotics, offer hope for breaking bacterial resistance. However, more extensive studies, especially in vivo, are necessary to fully evaluate the clinical potential of BRB and determine its practical applicability in combating antibiotic-resistant infections. Full article

Background: Bloodstream infections (BSIs) caused by multidrug-resistant non-fermenting Gram-negative bacilli, particularly Pseudomonas aeruginosa and Acinetobacter baumannii, represent a growing public health concern, especially in tertiary care settings. This study aimed to describe the epidemiological and antimicrobial resistance trends of P. aeruginosa and A. baumannii isolated from blood cultures over an eight-year period (2017–2024) at a tertiary infectious disease hospital in Bucharest, Romania, especially in the context of the disruption caused by the SARS-CoV-2 pandemic. Methods: A retrospective study was conducted on 43,951 blood cultures processed at the National Institute of Infectious Diseases. Species identification and antibiotic susceptibility testing (AST) were performed using VITEK2, MALDI-TOF MS, and supplementary phenotypic methods. AST interpretation followed EUCAST guidelines. Results: Out of all of the positive blood cultures, 112 (3.63%) were P. aeruginosa and 158 (5.12%) A. baumannii. Multidrug-resistance (MDR) was identified in 46% of P. aeruginosa and 90.73% of A. baumannii isolates. Resistance trends varied, with P. aeruginosa showing a decrease in MDR rates post-COVID-19 pandemic and following antimicrobial stewardship implementation. In contrast, A. baumannii displayed persistently high resistance, with carbapenem and aminoglycoside resistance rates reaching 100% by 2024. Colistin resistance, though low overall, increased in the latter years. Conclusions: The findings highlight the dynamic nature of antimicrobial resistance among P. aeruginosa and A. baumannii. Effective infection control and antimicrobial stewardship programs are crucial in curbing the rise of MDR strains, particularly amid healthcare system disruptions such as the COVID-19 pandemic. Full article

Introduction: The increase in the rates of multidrug-resistant bacteria in healthcare environments has been recognized as a global public health problem. In view of the scarcity of data on the neonatal population, this study aimed to provide information on the genotypic and epidemiological characteristics of Gram-negative microorganisms isolated from colonization and infection sites in neonates admitted to a tertiary university center of high complexity. Methods: Enterobacterales and non-fermenting Gram-negative bacilli previously collected in a prospective cohort study were submitted to genotypic identification, detection of extended-spectrum β-lactamases (ESBL), carbapenemases and biofilm production, detection of specific virulence markers in Pseudomonas aeruginosa, and typing by pulsed-field gel electrophoresis. Results: The data found here revealed higher rates of infection by Klebsiella spp. and Serratia marcescens that caused bloodstream infection and pneumonia, respectively. In this study, high biofilm production was observed, with 95.0% of Enterobacterales and 100% of non-fermenting Gram-negative bacilli being producers. Most of the P. aeruginosa isolates carried pathogenicity factors such as alginate, hemolytic phospholipase C, exotoxin A, and rhamnolipids. The phenotypic analysis of ESBL revealed that 16 (5.3%) isolates produced these enzymes. Four of these isolates (66.7%) carried the CTX-M-9 gene, three (50%) carried the TEM gene, and one (16.7%) was positive for the SHV and CMY-2 genes. Univariate and multivariate Cox regression analyses were used to identify risk factors for colonization and infection by Gram-negative microorganisms. The results of multivariate analysis revealed that biofilm production by these microorganisms was associated with the persistence of colonization by the same pathogen in the newborn and increased by 75% the daily probability of the newborn developing infection. The production of ESBL also increased the daily probability of infection by 46.8 times. Conclusions: Enterobacterales showed average biofilm production, while the majority of non-fermenting Gram-negative bacilli were strong producers. The present data increase our knowledge of the molecular epidemiology of important Enterobacterales species, with emphasis on ESBL-producing Enterobacter cloacae and Klebsiella pneumoniae with emerging epidemiological potential in the neonatal intensive care unit of a tertiary university hospital. Furthermore, the results highlight the need for the monitoring and implementation of control measures and for restricting the use of broad-spectrum antibiotics. Full article

The etiology and resistance pattern of bacterial conjunctivitis varies depending on the patient’s care setting and age. A retrospective, observational study was conducted in a tertiary care teaching hospital. A total of 126 patients—76 adults and 50 children—diagnosed with conjunctival infection during inpatient or ambulatory care were analyzed. In the samples of adult patients, isolates were represented by Gram-positive cocci (57.7%; Staphylococcus spp., S. pneumoniae) followed by Enterobacterales (17.97%; P. mirabilis, E. coli, Klebsiella spp.), and non-fermenters (7.69%; Pseudomonas spp., A. baumannii). Multidrug-resistant (52.17%) and extensively drug-resistant (21.73%) pathogens (predominantly Gram-negative bacilli) were identified in conjunctival swabs of hospitalized adult patients. The main isolates (55.77%) identified in children’s conjunctival swabs belonged to S. aureus, H. influenzae, and S. pneumoniae, followed by Enterobacterales (19.22%; E. coli, P. mirabilis, M. morganii) and fungi (3.48%). Methicillin-resistant S. aureus (35.71%) and extended-spectrum beta-lactamase-producing K. pneumoniae (8.7%) were identified in the pediatric subgroup of patients. In critically ill adult patients assisted in the intensive care or burn functional units, bacterial conjunctivitis followed the pattern of infections and antimicrobial resistance specific to these categories of patients. In the case of hospitalized children, conjunctivitis was an integral part of the age-related pathology. Full article

Purpose: Acute appendicitis (AA), classified as non-complicated acute appendicitis (NCAA) and complicated acute appendicitis (CAA), is the most common cause of abdominal pain in children requiring surgical treatment. If the first-line treatment for NCAA is to be debated between conservative management and surgery, authors find a consensus in choosing surgery as the first step for CAA in children. In the case of patients with CAA undergoing surgery, a broad-spectrum antibiotic therapy should be administered to reduce the risk of post-operative complications (POC). The rise in antibiotic resistance requires a review of recent data regarding bacterial species involved in AA. The primary aim of our study was to investigate the clinical effectiveness of different antibiotic protocols in patients undergoing surgery for CAA. The secondary aim was to verify the antibiotic’s in vitro effectiveness based on cultural examinations. Methods: A retrospective and prospective study was conducted on all patients operated on at our pediatric surgery department for CAA from January 2017 to January 2023. The following data were collected: age at surgery, sex, surgical technique, duration of the procedure, antibiotic therapy, duration of the hospital stay, cultural examination of peritoneal effusion, and POC. Results: We divided the patients enrolled (n = 182) into three groups of antibiotic protocols; only one group resulted in a statistically significant lower rate of POC. Different pathogens were isolated (Enterobacteriaceae, non-fermentative Gram-negative bacilli, anaerobes, Gram-positive cocci), and the in vitro rate of antimicrobial sensitivity varied from 40% to 94% in the three groups of patients. Conclusions: Based on cultural examinations, our study showed a high rate of inadequacy regarding the therapy with amoxicillin + clavulanic acid despite a low rate of complications. Radical surgery seems to be the best way to reduce complications in children with CAA. Full article

Bloodstream infections (BSIs) are life-threatening infections for which a timely initiation of appropriate antimicrobial therapy is critical. Antibiotic susceptibility testing (AST) directly performed on positive blood culture broths can help initiate targeted antibiotic therapy sooner than the standard AST performed on colonies isolated on solid media after overnight incubation. Faster antimicrobial susceptibility testing (AST) results can improve clinical outcomes, and reduce broad-spectrum antimicrobial consumption and healthcare-associated costs in sepsis. In this study, we evaluated the accuracy of a direct AST inoculation method on the BD Phoenix M50 system using serum separator tubes to harvest bacteria from positive pediatric blood culture bottles. Direct AST was performed on 132 monomicrobial pediatric blood culture bottles that were positive for Enterobacterales (65; 49.2%), Staphylococcus aureus (46; 34.8%), and non-fermenting Gram-negative bacilli (21; 16%). Overall, the categorical and essential agreements between the direct method and standard method were 99.6% and 99.8%, respectively. Very major, major, and minor error rates were 0.1%, 0.09%, and 0.20% respectively. Direct AST performed on pediatric blood culture bottles using BD Phoenix M50 can quickly provide accurate susceptibility information to guide antimicrobial therapy in patients with BSI. Full article

Timely pathogen identification in bloodstream infections is crucial for patient care. A comparison is made between positive blood culture (BC) pellets from serum separator tubes using a direct identification (DI) method and colonies on agar plates from a short-term incubation (STI) method with a matrix-assisted laser desorption/ionization Biotyper for the evaluation of 354 monomicrobial BCs. Both the DI and STI methods exhibited similar identification rates for different types of bacteria, except for Gram-positive and anaerobic bacteria. The DI method’s results aligned closely with the STI method’s results for Enterobacterales, glucose-non-fermenting Gram-negative bacilli (GNB), and carbapenem-resistant Enterobacterales. The DI method exhibited high concordance with the conventional method for GNB identification, achieving 88.2 and 87.5% accuracy at the genus and species levels, respectively. Compared with the STI method, the DI method showed a less successful performance for Gram-positive bacterial identification (50.5 vs. 71.3%; p < 0.01). The DI method was useful for anaerobic bacterial identification of slow-growing microorganisms without any need for colony growth, unlike in the STI method (46.7 vs. 13.3%; p = 0.04). However, both methods could not identify yeast in positive BCs. Overall, the DI method provided reliable results for GNB identification, offering many advantages over the STI method by significantly reducing the turnaround time and enabling quicker pathogen identification in positive BCs. Full article

The aim of this review is to synthesise the key aspects of the epidemiology, current microbiological diagnostic challenges, antibiotic resistance rates, optimal antimicrobial management, and most effective prevention strategies for Stenotrophomonas maltophilia (SM) in the intensive care unit (ICU) population. In recent years, resistance surveillance data indicate that SM accounts for less than 3% of all healthcare-associated infection strains, a percentage that doubles in the case of ventilator-associated pneumonia (VAP). Interestingly, SM ranks as the third most isolated non-glucose fermenter Gram-negative bacilli (NFGNB). Although this NFGNB genus has usually been considered a bystander and colonising strain, recently published data warn about its potential role as a causative pathogen of severe infections, particularly pneumonia and bloodstream infections (BSI), not only for the classical immunocompromised susceptible host patients but also for critically ill ones even without overt immunosuppression. Indeed, it has been associated with crude 28-day mortality as high as 54.8%, despite initial response following targeted therapy. Additionally, alongside its intrinsic resistance to a wide range of common antimicrobials, various worldwide and local surveillance studies raise concerns about an increase in ICU settings regarding resistance to first-line drugs such as cotrimoxazole or tigecycline. This scenario alerts ICU physicians to the need to reconsider the best stewardship approach when SM is isolated in obtained samples from critically ill patients. Despite the coverage of this multidrug-resistant bacterium (MDRB) provided by some traditional and a non-negligible number of current pipeline antimicrobials, an ecological and cost-effective strategy is needed in the present era. Full article

The emergency department (ED) represents an important setting for addressing inappropriate antimicrobial prescribing practices because of the time constraints and the duration of microbiological diagnosis. The purpose of this study is to evaluate the etiology and antimicrobial resistance (AMR) pattern of the community-acquired pathogens, as well as the epidemiological characteristics of patients admitted through the ED, in order to guide appropriate antibiotic therapy. Methods: A retrospective observational study was performed on 657 patients, from whom clinical samples (urine, purulent secretions, blood cultures, etc.) were collected for microbiological diagnosis in the first 3 days after presentation in the ED. The identification of pathogens and the antimicrobial susceptibility testing with minimum inhibitory concentration determination were carried out according to the laboratory protocols. Results: From the 767 biological samples analyzed, 903 microbial isolates were identified. E. coli was most frequently isolated (24.25%), followed by Klebsiella spp., S. aureus (SA), and non-fermentative Gram-negative bacilli. E. coli strains maintained their natural susceptibility to most antibiotics tested. In the case of Pseudomonas spp. and Acinetobacter spp., increased rates of AMR were identified. Also, 32.3% of SA strains were community-acquired MRSA. Conclusions: The introduction of rapid microbiological diagnostic methods in emergency medicine is imperative in order to timely identify AMR strains and improve therapeutic protocols. Full article

Aminoglycoside antimicrobials remain valuable therapeutic options, but their effectiveness has been threatened by the production of bacterial 16S ribosomal RNA methyltransferases (16S-RMTases). In this study, we evaluated the genomic epidemiology of 16S-RMTase genes among Gram-negative bacteria circulating in the American continent. A total of 4877 16S-RMTase sequences were identified mainly in Enterobacterales and nonfermenting Gram-negative bacilli isolated from humans, animals, foods, and the environment during 1931–2023. Most of the sequences identified were found in the United States, Brazil, Canada, and Mexico, and the prevalence of 16S-RMTase genes have increased in the last five years (2018–2022). The three species most frequently carrying 16S-RMTase genes were Acinetobacter baummannii, Klebsiella pneumoniae, and Escherichia coli. The armA gene was the most prevalent, but other 16S-RMTase genes (e.g., rmtB, rmtE, and rmtF) could be emerging backstage. More than 90% of 16S-RMTase sequences in the Americas were found in North American countries, and although the 16S-RMTase genes were less prevalent in Central and South American countries, these findings may be underestimations due to limited genomic data. Therefore, whole-genome sequence-based studies focusing on aminoglycoside resistance using a One Health approach in low- and middle-income countries should be encouraged. Full article

Carbapenem-resistant Gram-negative bacilli (CR-GNB) are a major public health concern. We aimed to evaluate the prevalence of CR-GNB and the frequency of carbapenemase-encoding genes in a tertiary referral center from El Bajio, Mexico. A cross-sectional study was conducted between January and October 2022; Gram-negative bacilli (GNB) were screened for in vitro resistance to at least one carbapenem. CR-GNB were further analyzed for carbapenemase-production through phenotypical methods and by real-time PCR for the following genes: bla_KPC, bla_GES, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48. In total, 37 out of 508 GNB were carbapenem-resistant (7.3%, 95% CI 5.2–9.9). Non-fermenters had higher rates of carbapenem resistance than Enterobacterales (32.5% vs. 2.6%; OR 18.3, 95% CI 8.5–39, p < 0.0001), and Enterobacter cloacae showed higher carbapenem resistance than other Enterobacterales (27% vs. 1.4%; OR 25.9, 95% CI 6.9–95, p < 0.0001). Only 15 (40.5%) CR-GNB had a carbapenemase-encoding gene; Enterobacterales were more likely to have a carbapenemase-encoding gene than non-fermenters (63.6% vs. 30.8%, p = 0.08); bla_NDM-1 and bla_NDM-5 were the main genes found in Enterobacterales; and bla_IMP-75 was the most common for Pseudomonas aeruginosa. The mcr-2 gene was harbored in one polymyxin-resistant E. cloacae. In our setting, NDM was the most common carbapenemase; however, less than half of the CR-GNB showed a carbapenemase-encoding gene. Full article

The OXA-10 class D β-lactamase has been reported to contribute to carbapenem resistance in non-fermenting Gram-negative bacilli; however, its contribution to carbapenem resistance in Enterobacterales is unknown. In this work, minimum inhibitory concentrations (MICs), whole genome sequencing (WGS), cloning experiments, kinetic assays, molecular modelling studies, and biochemical assays for carbapenemase detection were performed to determine the impact of OXA-10 production on carbapenem resistance in two XDR clinical isolates of Escherichia coli with the carbapenem resistance phenotype (ertapenem resistance). WGS identified the two clinical isolates as belonging to ST57 in close genomic proximity to each other. Additionally, the presence of the bla_OXA-10 gene was identified in both isolates, as well as relevant mutations in the genes coding for the OmpC and OmpF porins. Cloning of bla_OXA-10 in an E. coli HB4 (OmpC and OmpF-deficient) demonstrated the important contribution of OXA-10 to increased carbapenem MICs when associated with porin deficiency. Kinetic analysis showed that OXA-10 has low carbapenem-hydrolysing activity, but molecular models revealed interactions of this β-lactamase with the carbapenems. OXA-10 was not detected with biochemical tests used in clinical laboratories. In conclusion, the β-lactamase OXA-10 limits the activity of carbapenems in Enterobacterales when combined with low permeability and should be monitored in the future. Full article

Cefiderocol (FDC) is a siderophore cephalosporin now recognized as a new weapon in the treatment of difficult-to-treat-resistant (DTR) Gram-negative pathogens, including carbapenemase-producing enterobacterales and non-fermentative Gram-negative bacilli (GNB). This article reports our experience with an FDC-based regimen in the treatment of 16 extremely severe patients (invasive mechanical ventilation, 15/16; extracorporeal membrane oxygenation, 9/16; and renal replacement therapy, 8/16) infected with DTR GNB. Our case series provides detailed insight into the pharmacokinetic profile and the microbiological data in real-life conditions. In the narrative review, we discuss the interest of FDC in the treatment of non-fermentative GNB in critically ill patients. We reviewed the microbiological spectrum, resistance mechanisms, pharmacokinetics/pharmacodynamics, efficacy and safety profiles, and real-world evidence for FDC. On the basis of our experience and the available literature, we discuss the optimal FDC-based regimen, FDC dosage, and duration of therapy in critically ill patients with DTR non-fermentative GNB infections. Full article

Nosocomial infections caused by non-fermenting Gram-negative bacteria are a real challenge for clinicians, especially concerning the accuracy of empirical treatment. This study aimed to describe the clinical characteristic, empirical antibiotic therapy, accuracy of these prescriptions for appropriate coverage and risk factor for clinical failure of bloodstream infections due to non-fermenting Gram-negative bacilli. This retrospective, observational cohort study was conducted between January 2016 and June 2022. Data were collected from the hospital’s electronic record. The statistic tests corresponding to each objective were applied. A multivariate logistic regression was performed. Among the total 120 patients included in the study, the median age was 63.7 years, and 79.2% were men. Considering the appropriate empirical treatment rate by species, inappropriate treatment for S. maltophilia was 72.4% (p = 0.088), for A. baumanii 67.6% and 45.6% for P. aeruginosa. Clinical success was achieved in 53.3%, and overall, 28-day mortality was 45.8%. ICU admission, sepsis or shock septic, age, previous antibiotic treatment and contact with healthcare facilities were independently associated with clinical failure. In conclusion, bloodstream infection produced by multidrug-resistant non-fermenting Gram-negative bacteria is a significant therapeutic management challenge for clinicians. The accuracy of empirical treatment is low due to the fact that it is not recommended to cover these microorganisms empirically, especially S. maltophilia and A. baumanii. Full article