wzi gene sequencing, a rapid method to determine the capsular type of Klebsiella strains

ABSTRACT

Pathogens of the genus Klebsiella have been classified into distinct capsular (K) types for nearly one century. K-typing of Klebsiella still has important applications in epidemiology and clinical microbiology, but the serological method has strong practical limitations. Our objective was to evaluate sequencing of wzi, a gene conserved in all capsular types coding for an outer membrane protein involved in capsule attachment to the cell surface, as a simple and rapid method to predict the K-type. Sequencing of a 447-nucleotides region of wzi distinguished K-type reference strains with only nine exceptions. A reference wzi sequence database was created by inclusion of multiple strains representing K-types associated with high virulence and multidrug resistance. A collection of 119 prospective clinical isolates of K. pneumoniae was then analyzed in parallel by wzi sequencing and classical K-typing. Whereas K-typing achieved 81% typeability and 94.4% discrimination, these figures were 98.1%, and 98.3% for wzi sequencing. Prediction of K-type once knowing the wzi allele was 94%. wzi sequencing is as a rapid and simple method to determine the K-type of most K. pneumoniae clinical isolates.