Effects of penicillin V on the faecal microbiota in patients with pharyngotonsillitis—an observational study

Abstract

Background The intestinal microbiota functions as a reservoir of antibiotic resistance. Objectives To evaluate penicillin V (phenoxymethylpenicillin) effects on the faecal microbiota with focus on beta-lactam resistance. Methods We included 31 primary care patients with group A streptococcal pharyngotonsillitis treated with penicillin V for 5 (800 mg × 4) or 10 days (1000 mg × 3). Twenty-nine patients contributed with three faecal swab samples each. The faecal specimens were collected at the start of penicillin V treatment, after the last dose and at follow-up 7–9 days after completed treatment. Samples were inoculated semiquantitatively on selective screening agar plates to study beta-lactam resistance, species shifts among Enterobacterales and enterococci, and colonization with Candida spp. and Clostridioides difficile. Representative colonies were identified using MALDI-TOF. Results were analysed by non-parametric statistical methods. Results An increase in the proportion of patients colonized with ampicillin-resistant Enterobacterales, from 52% to 86% (P = 0.007), and Enterobacterales with decreased susceptibility to third-generation cephalosporins, from 32% to 52% (P = 0.034), was observed between the first and second samples. This increase was no longer significant at follow-up. New colonization with ampicillin-resistant Enterobacterales species and non-Enterobacterales Gram-negative species was observed, and persisted at follow-up. Conclusions Following treatment with penicillin V, we observed decreased susceptibility to ampicillin and third-generation cephalosporins, and prolonged colonization with non-Escherichia coli Gram-negative species. These findings challenge the perception that penicillin V has limited ecological effect on the intestinal microbiota, and emphasizes the importance of avoiding even narrow-spectrum antimicrobials when possible.

Systemic antibiotics in the surgical treatment of peri‐implantitis: A randomized placebo‐controlled trial

“…Anaerobic resistance to penicillin V has historically been considered low, but avoidance of even narrow‐spectrum antimicrobials is emphasized due to the ecological disturbance on the intestinal microbiome, characterized by the colonization of ampicillin‐resistant Gram‐negative species (Rystedt et al, 2023). The effects of amoxicillin on the saliva and gut microbiome were evaluated in a two‐centre RCT study.…”