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 Uropathogenic Escherichia coli (UPEC) often causes recurrent urinary tract infections, where biofilms and persister cells can promote recalcitrance. This study evaluated whether secretion-system marker genes associate with antimicrobial susceptibility, biofilm formation, and biofilm-associated persistence in clinical urinary isolates. A total of 71 isolates were screened by PCR for fimH and markers of secretion systems: type I (hlyA), type II (gspD), type V (ag43), and type VI (hcp). Minimum inhibitory concentrations (MICs) were measured by Etest, biofilm biomass by crystal violet assay, and persister survival in strong biofilm producers after antibiotic challenge. fimH was detected in 91.5% isolates; gspD and ag43 were common (71.8% and 80.3%), while hlyA and hcp occurred in 32.4% and 46.5%. Marker co-occurrence was frequent, with 19.7% carrying all four secretion markers, and 8.5% with no secretion markers detected. A total of 81.7% isolates formed biofilm, including 18.3% strong producers. Individual marker prevalence did not differ across biofilm categories. Carriage of hlyA and hcp was associated with lower MIC distributions for selected antibiotics (including fosfomycin, ciprofloxacin, and ampicillin-sulbactam), whereas gspD and ag43 showed no consistent MIC associations. The biofilm category was linked to non-susceptibility to ampicillin-sulbactam, but not the other agents tested. Strong biofilm producers showed biphasic killing consistent with persister formation, and hcp carriage tended to align with higher ciprofloxacin survival. These findings map secretion-system markers in clinical UPEC and suggest that a type VI secretion system may track with biofilm-associated persistence. IMPORTANCE Recurrent urinary tract infections (rUTI) often relapse after antibiotic treatment because bacteria can generate persister cells—temporary survivors that tolerate antibiotics without being genetically resistant. Clinicians, therefore, lack markers that flag isolates likely to persist. In 71 clinical urinary Escherichia coli isolates, this study surveyed genes encoding several secretion systems, molecular machines that help bacteria interact with each other and with host tissues. These markers were widespread and frequently co-occurred, but they did not track with stronger biofilm formation. However, a type VI secretion system marker (hcp) was associated with higher survival during ciprofloxacin exposure in strong-biofilm isolates, linking virulence-associated machinery with biofilm-associated persistence. Genetic signatures that reflect persistence, rather than routine resistance, could help prioritize follow-up testing and support development of strategies that target hard-to-eradicate rUTI infections. Recurrent urinary tract infections (rUTI) often relapse after antibiotic treatment because bacteria can generate persister cells—temporary survivors that tolerate antibiotics without being genetically resistant. Clinicians, therefore, lack markers that flag isolates likely to persist. In 71 clinical urinary Escherichia coli isolates, this study surveyed genes encoding several secretion systems, molecular machines that help bacteria interact with each other and with host tissues. These markers were widespread and frequently co-occurred, but they did not track with stronger biofilm formation. However, a type VI secretion system marker (hcp) was associated with higher survival during ciprofloxacin exposure in strong-biofilm isolates, linking virulence-associated machinery with biofilm-associated persistence. Genetic signatures that reflect persistence, rather than routine resistance, could help prioritize follow-up testing and support development of strategies that target hard-to-eradicate rUTI infections.
Paulina Soból, Weronika Kęsek, Maja Kirzyc et al.· Microbiology spectrum· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
