Chitosan enhances antimicrobial efficiency of ceftazidime against Burkholderia pseudomallei in an ex vivo skin model and cellular infections

Burkholderia pseudomallei, the causative agent of melioidosis, is a highly fatal tropical pathogen transmitted via skin inoculation, inhalation or ingestion. Its ability to persist intracellularly limits antibiotic efficacy and promotes relapses and chronic infection. This study investigated a combined chitosan with ceftazidime (CS/CAZ) to reduce skin inoculation and enhance intracellular eradication of B. pseudomallei using an ex vivo porcine skin model and human lung epithelial A549 cells. Biocompatible CS/CAZ concentration (1.25 mg mL-1 CS/1.00 µg mL-1 CAZ and 2.50 mg mL-1 CS/2.00 µg mL-1 CAZ) were compared with individual agents. The ex vivo porcine skin model demonstrated the complete eradication of B. pseudomallei by CS/CAZ at low inoculum levels (10 - 102 CFU) and significantly reduced bacterial adhesion at higher inocula (103-105 CFU), indicating a potential for topical antimicrobial application. In A549 cells, CS/CAZ markedly decreased B. pseudomallei adhesion and reduced intracellular bacterial loads by up to 3-6 logs units compared with individual treatments. Confocal laser scanning microscopy confirmed effective intracellular eradication of B. pseudomallei in A549 cells. Our findings demonstrate that the CS/CAZ offers synergistic antimicrobial activity, preventing skin colonization and enhancing intracellular clearance of B. pseudomallei, supporting its potential as a topical and adjunctive therapeutic strategy.