Microbiological identification and resistance profile of microorganisms in pressure injuries after the use of polyhexamethylene biguanide: a series of fourteen cases.

Introduction: Colonization of a pressure injury with microorganisms can negatively affect wound healing. Thus, it is necessary to evaluate which products best facilitate wound healing.
Objective: This case series evaluated the effectiveness of the antimicrobial polyhexamethylene biguanide (PHMB) on microorganisms in pressure injuries.
Materials and Methods: Fourteen patients (14 wounds) were treated with PHMB in the hospital setting after collection of a wound swab sample for microbiological analysis and determination of the risk profile using the disk diffusion method.
Results: Thirteen lesions (92.9%) were positive for 1 or more bacterial strains, the most prevalent of which were Staphylococcus aureus and Pseudomonas aeruginosa. Two strains of methicillin-resistant S aureus (MRSA) were also identified. Klebsiella pneumoniae demonstrated 100% resistance to the tested antibiotics, with Acinetobacter demonstrating 90% resistance, P aeruginosa 88.9%, Citrobacter freundii 87.5%, S aureus 66.7%, and MRSA 57.1%. Only Serratia marcescens demonstrated no resistance to any antibiotic tested. Polyhexamethylene biguanide was effective only against strains of S marcescens, which were not present in the second wound swab sample collected (after the application of PHMB); other microorganisms were present in the second wound swab sample collected.
Conclusions: Polyhexamethylene biguanide has an immediate antimicrobial effect on S marcescens. However, it had no qualitative effect on the other microorganisms. Studies with larger populations and randomized clinical trial methodologies are necessary to elucidate additional findings concerning the effectiveness of PHMB in managing microorganisms in pressure injuries.