Multidrug resistance and biofilm formation among bacterial isolates from chronic wounds in animals: evaluation of anti-biofilm activity

Abstract

Chronic wound infections in animals represent a growing clinical challenge due to the emergence of multidrug-resistant (MDR) bacteria and their ability to form biofilms, which significantly reduce treatment efficacy and promote persistent infection. This study aimed to characterize the bacterial profile, antimicrobial resistance patterns, biofilm-forming capacity, and anti-biofilm activity of agents against bacterial isolates recovered from chronic wound specimens. A total of 96 wound samples were analyzed, of which 84 (87.5%) yielded positive bacterial growth. The predominant bacterial isolates were Staphylococcus aureus (33.3%), followed by Pseudomonas aeruginosa (27.4%), Escherichia coli (19.0%), and Klebsiella spp. (11.9%). Antimicrobial susceptibility testing revealed high resistance to β-lactam antibiotics, with ampicillin showing the highest resistance rate (78.6%), whereas imipenem exhibited the lowest resistance (14.3%). Overall, 63.5% of isolates were classified as multidrug-resistant. Biofilm analysis demonstrated that 38.1% of isolates were strong biofilm producers, with strong biofilm-forming strains exhibiting higher minimum inhibitory concentration (MIC) values compared with weak and non-biofilm producers. Evaluation of anti-biofilm agents showed that silver nanoparticles, chitosan nanoparticles, and DNase enzyme reduced biofilm biomass by 72%, 65%, and 58%, respectively. These findings highlight the critical role of biofilm-mediated resistance in chronic wound infections and emphasize the need for integrated antimicrobial and anti-biofilm strategies for effective management of MDR bacterial infections.