A European survey on anaerobes from paediatric blood cultures: a comparative analysis with adults

Infections caused by anaerobes are common in children. However, limited data are available on bloodstream infections caused by these bacteria in Europe. A multicentre retrospective observational study was conducted over a 4-year period (2020-2023) across 44 European hospitals to analyze all anaerobes isolated from blood cultures. The study examined the epidemiology and antimicrobial resistance profiles of anaerobes identified in paediatric patients, comparing the findings with those observed in adults. Among the 14,527 total anaerobic isolates, 186 (1.3%) were detected from paediatric patients. These were predominantly Gram-positive (70%) and Gram-negative (22%) bacilli. The most prevalent species in paediatric patients were Cutibacterium acnes (24.7%), Schaalia odontolytica (9.7%), Actinomyces oris (8.1%), and Bacteroides fragilis (7.5%). Relative feature importance based on the mean SHAP (SHapley Additive exPlanations) values distinguished paediatric patients and adults based on their antibiotic resistance patterns with high accuracy. Compared to those from adult patients, Gram-positive bacilli detected in paediatric samples displayed higher resistance rates for meropenem (15% vs. 9%), metronidazole (52% vs. 24%), and vancomycin (27% vs. 6%), and lower resistance to benzylpenicillin (11% vs. 17%), amoxicillin/clavulanate (9% vs. 17%), and clindamycin (30% vs. 36%). Gram-negative bacilli in paediatric samples displayed lower resistance to benzylpenicillin (18% vs. 29%), piperacillin/tazobactam (26% vs. 33%), and clindamycin (20% vs. 27%), and they were highly susceptible to imipenem, meropenem, and metronidazole as those detected in adult patients. Bacteroides species detected in paediatric and adult patients displayed high resistance to piperacillin/tazobactam (33% vs. 39%) and clindamycin (38% vs. 29%), while they were highly susceptible to metronidazole. Compared to those from adult samples, Cutibacterium acnes in paediatric patients displayed lower resistance to benzylpenicillin (none vs. 15%) and clindamycin (17% vs. 29%). The comparison of species and susceptibility profiles of anaerobes detected in paediatric and adult patients highlighted the importance of reporting antimicrobial susceptibility surveillance data by age group.