Characterisation of Biofilm-Forming Pseudomonas aeruginosa Isolates from Burn Wound Infections and Their In Vitro Susceptibility to Novel Antimicrobials in Sokoto State, North West Nigeria

Biofilm-forming Pseudomonas aeruginosa is a leading pathogen in burn wound infections and exhibits markedly increased tolerance to conventional antimicrobials, complicating treatment and contributing to septic mortality in burns units. This study characterised biofilm-forming P. aeruginosa from burn wound infections at Usmanu Danfodiyo University Teaching Hospital Sokoto, North West Nigeria, and evaluated their susceptibility to novel antimicrobial combinations. Clinical wound isolates from 80 burn patients were screened for biofilm formation using the crystal violet microtitre plate assay and categorised as strong, moderate, or weak biofilm producers. Virulence genes including lasI, rhlI, and algD were detected by PCR. Antibiotic susceptibility of planktonic and biofilm cells was assessed for standard antibiotics and novel combinations including colistin-rifampicin and ceftazidime-avibactam. Sixty-seven P. aeruginosa isolates were recovered from 80 patients, with 71.6% being strong biofilm producers. Multidrug resistance was present in 64.2% of isolates. Standard MICs were 4-to-64-fold lower for planktonic compared to biofilm cells. Colistin-rifampicin synergy showed biofilm eradication in 82.4% of tested isolates. Ceftazidime-avibactam was active against 91.3% of MDR isolates in planktonic form but had reduced activity in biofilm. lasI and algD were significantly associated with strong biofilm phenotype. The study recommends combination antimicrobial strategies targeting biofilm-embedded organisms, investment in novel antimicrobial agents, and enhanced burns unit infection surveillance in North West Nigeria. Keywords: Pseudomonas aeruginosa, biofilm, burn wound, antimicrobial resistance, colistin-rifampicin