Non-pigmented strain of serratia marcescens: an unusual pathogen causing pulmonary infection in a patient with malignancy.

Serratia marcescens is a member of the family Enterobacteriaceae. It has emerged in recent years as an opportunistic pathogen of nosocomial infections. Some biotypes of Serratia marcescens produce the non-diffusible red pigment prodigiosin. Though both pigmented and non-pigmented biotypes may be pathogenic for humans, the non-pigmented biotypes are more virulent due to cytotoxin production and presence of plasmids mediating antibiotic resistance. However in India only one study done 31 years back has reported on infections caused by non-pigmented strains of Serratia marcescens. We present a case of a patient with squamous cell carcinoma of the left retromolar trigone, soft palate and buccal mucosa, who developed pulmonary infection with non-pigmented strain of Serratia marcescens. According to the available literature, this is the second report on infection with non-pigmented strain of Serratia marcescens from India. It is imperative to accurately detect the non-pigmented biotypes due to their tendency to cause serious and difficult to treat infections.