Application of bacteriophage typing to klebsiella pneumoniae

Abstract

Klebsiella pneumoniae is a major cause of nosocomial infections, and an increasing proportion of K. pneumoniae isolates are resistant to commonly used antibiotics. Thus, outbreaks must be monitored and effective infection control policies implemented in order to prevent dissemination. I used a bacteriophage typing system to supplement serotyping in differentiating capsular cross-reactivity between isolates and to type serologically non-typable clinical isolates of K. pneumoniae. As well, I set out to examine whether the bacteriophage endoglycosidase determines capsular specificity. Using sewage as starting material, I isolated 91 bacteriophages to the 77 capsular serotypes of Klebsiella. I evaluated the ability of these bacteriophages to differentiate 17 serologically cross-reacting K. pneumoniae isolates from human, animal, and environmental sources. Bacteriophage typing of these isolates readily resolved the ambiguity encountered in serotyping of these isolates. I also used 13 multiply cross-infecting bacteriophages to type 30 serologically untypable hospital isolates of K. pneumoniae. Bacteriophage typing results indicate that most of the isolates were unrelated, with only a few isolates being clonal in origin. This suggests that in at least some cases, a breakdown in infection control had occurred. Overall, bacteriophage typing proved to be an effective, inexpensive, and clinically practical adjunct to serotyping in distinguishing serologically cross-reactive and serologically nontypable isolates of K. pneumoniae. Finally, I evaluated whether the bacteriophage endoglycosidase is involved in determining capsular specificity. I measured endoglycosidase activity in the presence of partially purified capsular polysaccharide of K. pneumoniae serotypes upon which the bacteriophage could or could not replicate. Bacteriophages were able to generate reducing sugars in capsular polysaccharine from the isolating host and from hosts in which replication could not occur. This was observed with both specific and multiply cross-infective bacteriophages, suggesting that the bacteriophage endoglycosidase does not determine capsular specificity.