Evaluation of the antimicrobial activity of Castanea sativa against imipenem-resistant non-fermentative bacteria

Aims: Carbapenems, particularly imipenem, are a class of antibiotics commonly used for treating infections caused by antibiotic-resistant gram-negative bacteria. However, the increasing prevalence of imipenem-resistant bacterial strains underscores the necessity of discovering alternative therapeutic options. The current study assessed the ethanol (EtOH) extract of Castanea sativa (C. sativa) Mill. flowers for its antimicrobial activity and potential as an adjuvant in antibiotic therapy against imipenem-resistant clinical strains of Acinetobacter baumannii (A. baumannii) and Pseudomonas aeruginosa (P. aeruginosa). Methods: A total of 40 non-duplicate clinical strains of P. aeruginosa (n=21) and A. baumannii (n=19), belonging to non-fermentative gram-negative bacteria, were included in the study. The antimicrobial activity of the extract and its potential to potentiate imipenem were evaluated using the disk diffusion method. Results: The inhibition zone diameters for the extract alone ranged from 7 mm to 10 mm for P. aeruginosa strains and from 11 mm to 14 mm for A. baumannii strains. When combined with imipenem, these diameters increased slightly, ranging from 8 mm to 11 mm and 11 mm to 15 mm for P. aeruginosa and A. baumannii strains, respectively. Conclusion: The findings suggest that the EtOH extract of C. sativa flowers possesses antimicrobial activity against imipenem-resistant P. aeruginosa and A. baumannii strains, albeit with a minimal imipenem-potentiating effect. Further studies are required to explore the full potential of this extract in combating resistant bacterial infections.