Further Studies in the Pyocine typing of Pseudomonas Pyocyanea

Further experience of the typing of strains of Pseudomonas pyocyanea (Ps. aeruginosa) by their production of pyocines has confirmed the value of pyocine typing for epidemiological studies.

The introduction of five new indicator strains has made it possible to distinguish eight subtypes of the commonly occurring pyocine type 1. The subtyping of the type-1 strains shows the same dependence on use of the correct temperature and duration of incubation of the producer strain as does the main typing procedure.

In studies of the reliability of the typing and subtyping methods for epidemiological purposes it was noted that not all strains of Ps. pyocyanea isolated from the same site in the same patient were of the same pyocine type or subtype. When several colonies of Ps. pyocyanea from individual diagnostic plates were typed it was found that more than one pyocine type or subtype was more frequently present in the same lesion in patients in hospital than in patients being treated at home. This finding suggests that the occurrence of more than one pyocine type or subtype of Ps. pyocyanea in a patient is generally due to his having been separately infected with strains of more than one type, rather than to instability of pyocine production in a single infecting strain.