Aug 2026· The Pediatric Infectious Disease Journal· 0 citations· 43 references
Medicine
TL;DR
Nonfermenting Gram-negative bacilli other than Pseudomonas and Acinetobacter species were frequently associated with healthcare exposure and complex resistance profiles, and their management is challenged by a lack of evidence and standardized susceptibility criteria.
Abstract
Background
Nonfermenting Gram-negative bacilli other than Pseudomonas and Acinetobacter species are increasingly recognized as opportunistic pathogens in pediatric populations, yet their epidemiology and antimicrobial resistance remain poorly defined.
Methods
We conducted a multicenter retrospective analysis across 56 hospital centers in 25 European countries, including pediatric blood culture isolates collected between January 2020 and December 2024. Species distribution and antimicrobial susceptibility profiles according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) current guidelines were analyzed.
Results
A total of 382 isolates were included, spanning 19 genera and 40 species. Stenotrophomonas maltophilia was the most frequently identified species (46.9%; n = 179), followed by Roseomonas mucosa (10%; n = 38) and Sphingomonas paucimobilis (7.6%; n = 29). Susceptibility profiles were heterogeneous, with notable resistance across several species. For S. maltophilia, resistance to trimethoprim/sulfamethoxazole exceeded 10% (EUCAST), while full in vitro susceptibility to aztreonam/avibactam was observed. Preserved activity of carbapenems but high resistance to ceftazidime (EUCAST/CLSI), piperacillin/tazobactam (EUCAST/CLSI) and ciprofloxacin (CLSI) was observed for S. paucimobilis. Achromobacter several species showed concerning resistance patterns to carbapenems, piperacillin/tazobactam and trimethoprim/sulfamethoxazole (CLSI).
Conclusions
Nonfermenting Gram-negative bacilli other than Pseudomonas and Acinetobacter species were frequently associated with healthcare exposure and complex resistance profiles. Their management is challenged by a lack of evidence and standardized susceptibility criteria. To optimize management, enhanced surveillance, improved diagnostic standardization and further clinical studies on emerging therapies are needed.
OBJECTIVES
The aim of this study was to characterize the distribution of anaerobic bacteria isolated from clinical specimens across major specimen types and to determine the antimicrobial susceptibility patterns of the most frequently isolated species.
METHODS
Clinical specimens collected in 2022 from three university hospitals in Warsaw were analyzed. Anaerobes were identified using MALDI-TOF MS, and antimicrobial susceptibility testing was performed according to EUCAST guidelines. A total of 1,425 isolates were included and classified as Gram-negative anaerobic bacilli (GNAB), Gram-positive anaerobic cocci (GPAC), Gram-positive anaerobic bacilli (GPAB), and spore-forming bacilli.
RESULTS
Skin and soft tissue specimens yielded the largest number of isolates (n = 720), predominantly Finegoldia magna, Bacteroides fragilis, Anaerococcus vaginalis, and Prevotella bivia. Among intra-abdominal specimens (n = 366), the Bacteroides species constituted the majority of GNAB. Among head and neck specimens (n = 261), Prevotella spp. and Parvimonas micra were most common. Isolates recovered from blood cultures (n = 59) were dominated by Cutibacterium acnes, followed by Bacteroides spp. and Clostridium spp. Metronidazole and meropenem showed the highest overall activity (>95% susceptibility). β-lactam-β-lactamase inhibitor combinations remained broadly effective, with susceptibility rates exceeding 90% for most anaerobic species, although lower susceptibility was observed among certain Bacteroides species, particularly B. thetaiotaomicron (69.1%). Clindamycin susceptibility was 50% or lower among Bacteroides species and variable among Prevotella spp. and GPAC.
CONCLUSIONS
Anaerobic bacteria isolated from clinical specimens demonstrated considerable species diversity and characteristic specimen-specific distribution patterns. Bacteroides and Prevotella species, predominated in intra-abdominal specimens, whereas F. magna and other GPAC were most commonly recovered from skin and soft tissue infections. Species belonging to Actinomyces and related genera were frequently identified in specimens from head and neck infections. Although susceptibility rates exceeded 95% for carbapenems and metronidazole, species-dependent resistance-particularly to clindamycin and piperacillin-tazobactam-highlights the need for ongoing surveillance and precise species-level identification to support optimal empirical therapy.
M. Kierzkowska, D. Lachowicz, Dominika Seliga-Gąsior et al.· Anaerobe· 0 citations
ABSTRACT Enterobacter spp., after Klebsiella pneumoniae, is among the most common hospital-acquired enterobacteria associated with antimicrobial resistance (AMR) worldwide, yet it remains underexplored. We determined the taxonomic and epidemiological distribution of 131 representative carbapenemase-producing Enterobacter spp. recovered from infections across Argentina between 2016 and 2022. The sample included one isolate per patient from 17 jurisdictions and 68 hospitals. Outbreak-related and surveillance isolates were excluded. Sequencing was performed using Illumina, and bioinformatic analyses were used to determine species (average nucleotide identity [ANI] ≥94%) and subspecies (ANI ≥98%) using BactInspector/fastANI. Sequence types (STs) were assigned by multilocus sequence typing (MLST) via PubMLST, and resistance genes were identified using AMRfinderPlus/Resfinder. Samples were obtained from (n; %) urine (43; 33%), blood (41; 31%), and other sites (47; 36%). Seven species were identified, with Enterobacter hormaechei (EH) predominating ( 120; 92%) and comprising five subspecies. E. hormaechei subsp. steigerwaltii was the most abundant (60; 45%), followed by E. hormaechei subsp. xiangfangensis (29; 22%). Enterobacter cloacae subsp. cloacae was underrepresented (3; 2.3%). KPC-2 was the predominant carbapenemase, followed by NDM-1 and OXA-163. A total of 58 STs were identified, 38 represented by a single isolate. EH included 50 STs, with the most abundant being ST88 (12; 9%), ST78 (12; 9%), and ST66 (8; 6%). No clear associations were observed between species/subspecies, clones, and carbapenemase types. Overall, the population structure of carbapenemase-producing Enterobacter spp. in Argentina is complex and diverse, characterized by multiple species, subspecies, clonal diversity, and varied carbapenemase types and combinations. Notably, 50% of the isolates belonged to E. hormaechei subsp. steigerwaltii, suggesting a major role of this subspecies in the dissemination of AMR. IMPORTANCE Carbapenemase-producing Enterobacter spp. rank as the most common Enterobacterales associated with carbapenemase production. Despite their clinical relevance, the taxonomy and population structure of this group remain poorly characterized. This study provides a comprehensive genomic overview of clinical carbapenemase-producing Enterobacter spp. circulating in Argentina, revealing a highly diverse population composed of species, subspecies, and clonal types, harboring mainly KPC-2, followed by NDM-1 and combinations. We identified international clones within E. hormaechei, such as ST88 and ST78, which may play important roles in the dissemination of antimicrobial resistance. Notably, 50% of the isolates belonged to E. hormaechei subsp. steigerwaltii, suggesting a major role of this subspecies in the dissemination of antimicrobial resistance (AMR). By improving our understanding of this complex bacterial group, this work supports the strengthening of antimicrobial resistance surveillance networks and the development of targeted strategies for infection control and antibiotic stewardship in healthcare settings. Carbapenemase-producing Enterobacter spp. rank as the most common Enterobacterales associated with carbapenemase production. Despite their clinical relevance, the taxonomy and population structure of this group remain poorly characterized. This study provides a comprehensive genomic overview of clinical carbapenemase-producing Enterobacter spp. circulating in Argentina, revealing a highly diverse population composed of species, subspecies, and clonal types, harboring mainly KPC-2, followed by NDM-1 and combinations. We identified international clones within E. hormaechei, such as ST88 and ST78, which may play important roles in the dissemination of antimicrobial resistance. Notably, 50% of the isolates belonged to E. hormaechei subsp. steigerwaltii, suggesting a major role of this subspecies in the dissemination of antimicrobial resistance (AMR). By improving our understanding of this complex bacterial group, this work supports the strengthening of antimicrobial resistance surveillance networks and the development of targeted strategies for infection control and antibiotic stewardship in healthcare settings.
J. D. de Mendieta, María Alejandra Menocal, María Belén Sanz et al.· Microbiology spectrum· 0 citations
The sustained increase in antimicrobial resistance among Gram-negative bacilli (GNB) compromises the effectiveness of empirical treatment regimens. This study aims to describe the evolution of the frequency and antimicrobial resistance profiles of the most commonly isolated GNB in urine cultures in our area. A cross-sectional, descriptive, and retrospective study was conducted, analyzing urine cultures from patients with suspected UTIs between 2021 and 2025. Microorganism identification was performed using MALDI Biotyper or MicroScan systems, and antimicrobial susceptibility testing was carried out using MicroScan, interpreted according to EUCAST guidelines. A total of 81,791 urine cultures were analyzed. In E. coli, a significant increase in resistance was observed for amoxicillin-clavulanate, ciprofloxacin, piperacillin-tazobactam, and fosfomycin (from 3.48% in 2021 to 25.31% in 2025). Klebsiella pneumoniae showed a marked increase in resistance to fosfomycin (from 27.25% to 79.73%) and imipenem. Pseudomonas aeruginosa, predominantly hospital-acquired, exhibited a significant increase in resistance to piperacillin-tazobactam, imipenem, and antipseudomonal cephalosporins. The evolution of antimicrobial resistance in uropathogenic GNB in our region is complex and dynamic. The spread of carbapenemases highlights the need for rigorous local epidemiological surveillance and optimization of antimicrobial stewardship programs to guide empirical therapy and infection control measures.
Leticia Castellano-Sánchez, Antonio Rosales-Castillo, Lucía Requena-Fernández et al.· Acta Pathologica, Microbiolo...· 0 citations
Background: Infections with uncommon non-fermentative Gram-negative bacilli (NFGNB) are on the rise worldwide. However, studies from developing countries mainly focus on reporting common NFGNB like Pseudomonas aeruginosa and Acinetobacter spp. Few studies report the isolation frequency and antibiotic susceptibility pattern of uncommon NFGNB from clinical samples.
Objective: To determine the species distribution and antimicrobial susceptibility patterns of uncommon NFGNB from various clinical samples.
Methods: This is a retrospective study of uncommon NFGNB isolated from 1st January 2013 to 31st December 2023 in the Microbiology laboratory at Liaquat National Hospital and Medical College, Karachi. Identification of uncommon NFGNB was performed through conventional methods, API 20NE, and VITEK 2 Compact. For Antibiotic susceptibility testing, Kirby-Bauer disk diffusion, E strip, and VITEK 2 Compact were used. Data analysis was performed using the computer package SPSS version 20.
Results: A total of 1056 Uncommon NFGNB were isolated during the study period. The predominant species included Chryseobacterium spp 57.8% (n=611), Achromobacter xylosoxidans 12.5% (n=134), Shewanella putrifacieans 7.3% (n=78), Ralstonia Picketii 3.5% (n=37), and Brevundimonas spp 3.4% (n=36). The highest number was isolated from respiratory and blood samples of hospitalized male patients (92.8%, n=980) and from blood samples of hospitalized female patients (51.3%, n=542). The year-wise trend demonstrates a consistent isolation of NFGNB. The continued isolation of NFGNB with intrinsic resistance to Colistin underscores its rational use in hospitalized patients.
Conclusion: Uncommon NFGNB are emerging pathogens and are frequently resistant to multiple antibiotics. Strict antibiotic stewardship and infection prevention measures should be implemented to preserve last-resort antibiotics.
S. Anwar, Uzma Saad, Sana Muslim et al.· Journal of Liaquat National...· 0 citations
OBJECTIVES
This study investigated the in vitro activity of cefiderocol and comparator antibiotics against Gram-negative bacterial isolates with highly resistant phenotypes collected in the SENTRY Antimicrobial Surveillance Program.
METHODS
Between 2020 and 2024, consecutive Gram-negative bacterial isolates were collected from hospitalized patients in the USA and Europe, Turkey and Israel. Minimum inhibitory concentrations (MICs) were determined by broth microdilution method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Susceptibility was interpreted, as applicable, by CLSI M100 (2026), European Committee on Antimicrobial Susceptibility Testing (EUCAST) (2026), and US Food and Drug Administration (FDA 2026) criteria.
RESULTS
Cefiderocol was the only antibiotic that inhibited >90% of carbapenem-non-susceptible isolates by CLSI breakpoints (95.5% of 1229 Enterobacterales, 98.8% of 2807 Pseudomonas aeruginosa, 93.7% of 2254 Acinetobacter baumannii-calcoaceticus species complex, and 99.3% of 2341 Stenotrophomonas maltophilia), and susceptibilities to cefiderocol were >90% across various infection sites. Against multidrug-resistant (MDR) Enterobacterales (N=10 606) and P. aeruginosa (N=1817), cefiderocol susceptibility rates were 99.1% and 98.1%, respectively. Susceptibilities to comparator antibiotics ranged between 73.2% (ceftolozane-tazobactam) and 99.8% (aztreonam-avibactam) for MDR Enterobacterales, and between 18.3% (meropenem) and 77.5% (imipenem-relebactam) for MDR P. aeruginosa. 97.4% of 459 DTR P. aeruginosa were susceptible to cefiderocol. Additionally, cefiderocol displayed low MIC50/90 values against Burkholderia cepacia species complex and Achromobacter spp. (0.06/0.5 mg/L and 0.03/0.25 mg/L, respectively).
CONCLUSIONS
Cefiderocol showed potent in vitro activity against contemporary isolates of Gram-negative bacteria displaying challenging resistance phenotypes.
B. DeJonge, C. Longshaw, Frank H Kung et al.· Journal of Global Antimicrob...· 0 citations
Background Carbapenem-resistant Acinetobacter baumannii is a critical-priority pathogen in pediatric hospitals, but the relative roles of clonal transmission and environmental reservoirs remain unclear. Methods We analyzed 42 non-duplicate A. baumannii isolates collected between 2020 and 2023 from clinical specimens (n = 28), medical waste (n = 8), and hospital-setting samples (n = 6) at Wuhan Children’s Hospital. Antimicrobial susceptibility testing, PCR-based resistance gene detection, pulsed-field gel electrophoresis, and crystal-violet biofilm assays were performed. Results Clinical isolates showed high multidrug resistance (75.0%, 21/28), with 75.0% resistant to piperacillin–tazobactam, ceftazidime, imipenem, meropenem, and ciprofloxacin. All isolates remained susceptible to tigecycline. OXA-23 was detected in all carbapenem-resistant clinical isolates, and aac(6′)-Ib-cr was present in all fluoroquinolone-resistant isolates. One dominant clinical clone, T11, accounted for 57.1% of clinical isolates and included one OXA-23/NDM co-producing isolate. PFGE revealed no clonal overlap between clinical and non-clinical isolates; all medical-waste and hospital-setting isolates were fully susceptible. Biofilm formation was detected in 97.6% of isolates; among clinical isolates, biofilm intensity was inversely associated with multidrug resistance, with susceptible isolates forming stronger biofilm (Fisher’s exact p < 0.001). Conclusion Pediatric multidrug-resistant A. baumannii infections in this hospital were most consistent with patient-to-patient dissemination of a dominant resistant clone rather than with contamination from the hospital-setting or medical-waste reservoirs sampled here, although the small environmental sample cannot definitively exclude such reservoirs. Phenotype–genotype–PFGE surveillance provides actionable guidance for infection control in resource-limited pediatric settings.
Wanjun Luo, Xuyang Gong, Si-Jing Liu et al.· Frontiers in Medicine· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
