Pyocin typing and serotyping of 433 strains of Pseudomonas aeruginosa from children with
cystic fibrosis (CF) showed that
pyocin type 9 was predominant, particularly in association with polyagglutinating serotype. The common
pyocin groups, 1, 5 and 10, made up only 20% of these isolates in contrast to reported rates of up to 89% in other studies using non-CF strains. No strains of
pyocin type 3 were found. Polyagglutinating strains made up 72% of strains from patients colonized with P. aeruginosa for more than 12 mths.
Pyocin type 9 was associated with 93% of polyagglutinating strains. The parallel between
pyocin type 9 and polyagglutinating serotype suggests that these may both be characteristics acquired by P. aeruginosa colonizing patients with CF. Because of confounding between duration of colonization and exposure to
cross-infection, this study does not allow definition of the role of
cross-infection in determining the characteristics of these strains in most patients. In siblings, however, evidence supports a role for
cross-infection either between siblings or from a common source. In 6 pairs of siblings studied, each pair had at least 1
pyocin group in common concurrently, either at entry to the study or after an interval of several months. Identical and unusual
pyocin groups were recognized in samples obtained on the same day from pairs of siblings. More studies are needed to compare results of
pyocin typing with methods such as genome fingerprinting to characterize these strains and determine whether the observed distribution of
pyocin groups in CF isolates is related to
cross-infection or whether the combination of
pyocin type 9 with polyagglutinating serotype is a characteristic of CF strains.