Cryptic Plasmids in Hospital Isolates of Providencia Stuarti

Abstract

The distribution of cryptic plasmids among 123 isolates of P. stuartii from a hospital ward during a prospective epidemiological study is reported. Two closely related stable plasmids (34 Kb [kilobase] and 36 Kb) were identified by restriction endonuclease digest analysis of plasmid DNA. One or other of these cryptic plasmids was carried by 40 isolates, the remainder were plasmid-free. A higher proportion of 1 cryptic plasmid (CPT-A) was found in environmental isolates than in isolates from patients. The serotype of all isolates of P. stuartii was O63 and they were epidemiologically related. Two of the 8 patients colonized by P. stuartii carried all 3 possible variants: plasmid-free (PFI) strains or strains containing cryptic plasmid A (CPT-A) or cryptic plasmid B (CPT-B). The epidemiological significance of these results is discussed.