In-vitro activity of polyhexamethylene biguanide (PHMB) against fungal isolates associated with infective keratitis

Sir, Fungal keratitis is an infection that is difficult both to diagnose and to treat. Candida albicans , other yeasts and the septate moulds, Fusarium spp. and Aspergillus spp., are common causes of this disease. Treatment options are limited and include topical formulations of natamycin (5%), amphotericin B (0.15%) and fluconazole (1%). However, the efficacies of these agents are compromised by poor ocular penetration, poor tolerability and/or poor in-vitro activity. Polyhexamethylene biguanide (PHMB), which is currently used as an environmental biocide and contact lens disinfectant, has been shown to have excellent in-vitro activity against a broad range of fungal pathogens and to be effective and well tolerated at concentrations of 200 mg/L (0.02%) when used as treatment of patients with keratitis caused by Acanthamoeba spp. The present study was undertaken to evaluate the in-vitro activity of PHMB against fungal isolates associated with infective keratitis. The organisms used in the study included 25 isolates of C. albicans which were isolated from patients at the University of Illinois Hospital, Chicago, IL, USA (n 5 10), Columbia Wesley Medical Center, Wichita, KS, USA (n 5 10) and St Vincent’s Mercy Medical Center, Toledo, OH, USA (n 5 5), a single isolate of Aspergillus niger which was recovered from a patient at the University of Illinois Hospital, and the following four strains which were provided by the American Type Culture Collection, Rockville, MD, USA: C. albicans 24433; Candida parap silosis 22019; Candida krusei 6258 and Fusarium solani 44366. PHMB 20% was obtained from Zeneca Biocides, Wilmington, DE, USA.