Low penicillin susceptibility in Streptococcus mitis/oralis from bloodstream infections in pediatric populations

Streptococcus mitis/oralis can cause invasive diseases, including bloodstream infections. However, existing research primarily focuses on specific populations, and limited studies have been conducted on the prevalence of bloodstream infection caused by S. mitis/oralis across the entire pediatric population. Therefore, clinical data of S. mitis/oralis isolated from blood samples at Children's Hospital, Zhejiang University School of Medicine, during the period 2019-2023 were collected retrospectively to provide a comprehensive understanding of the clinical characteristics and drug resistance patterns associated with bloodstream infections caused by S. mitis/oralis in pediatric populations. There were 57 (43.5%) instances of contamination across various departments, indicating a relatively dispersed pattern. Bloodstream infections caused by S. mitis/oralis are notably prevalent among pediatric patients with hematological diseases and tumors. The susceptibility rates of the 74 S. mitis/oralis isolates to different antibiotics were as follows: penicillin (23%), ceftriaxone (74.3%), levofloxacin (86.5%), chloramphenicol (89.2%), erythromycin (27%), clindamycin (67.6%), linezolid (100%), and vancomycin (100%). Notably, 21.6% of the isolates exhibited multi-drug resistance (MDR). The predominant mode of MDR in S. mitis/oralis infections was identified as resistance to beta-lactams, erythromycin, and clindamycin. The observed low susceptibility rate to penicillin, coupled with the emergence of MDR strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis. IMPORTANCEExisting research primarily focuses on specific populations, such as those with hematopathy or tumors, who experience Streptococcus mitis/oralis bacteremia. Limited studies have been conducted on the prevalence of bloodstream infections caused by S. mitis/oralis across the entire pediatric population. It was found that the contamination rate of S. mitis/oralis isolated from blood cultures was notably high in our study. Therefore, this study evaluated the clinical characteristics and drug resistance patterns of bloodstream infections caused by S. mitis/oralis across the entire pediatric populations, explicitly excluding cases of blood culture contamination. The observed low susceptibility rate to penicillin, coupled with the emergence of multi-drug-resistant strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis.