Capsular Types, Virulence Factors and DNA Types of <i>Klebsiella oxytoca </i> Strains Isolated from Blood and Bile

Abstract

Klebsiella oxytoca is an opportunistic pathogen and is isolated at the second highest frequency among genus Klebsiella from hospitalized patients. According to previous reports, the major virulence factors of K. pneumoniae include capsules and several kinds of pill, whereas the virulence factors of K. oxytoca have not been well investigated. We noticed an increased frequency of K. oxytoca isolates from patients who had undergone a biliary tract operation in a general hospital from May through November, 2009. We then performed a PCR analysis of the virulence factors and an epidemiological analysis with capsular typing (serotyping) and pulsed field gel electrophoresis (PFGE) for K. oxytoca of 11 blood isolates and 10 bile isolates. As a result, serotypes of K9, K15, K26, K31, K43, K47, K55, K70, and K79 were identified in these strains, and K1 and K2 which are frequent serotypes in K. pneumoniae strains were not observed. Two blood isolates of the K55 serotype showed almost the same PFGE pattern, suggesting that these isolates were very closely related and caused cross-infection in a hospital ward. Strains of the K43 serotype were three blood isolates and 1 bile isolate, all of which showed different PFGE patterns. There were no common isolates among the blood and bile isolates. A PCR search revealed that fimH and mrkD genes which are relevant to type 1 and type 2 pili, respectively, were present in all strains, whereas kfuBC, an iron uptake gene, and cf29a were detected in only a few strains. Neither of the mucoid phenotype-related genes magA and rmpA was present in any strains. These results strongly suggest that type 1 and/or type 3 pili would have important roles in the pathogenesis of blood infection and bile infection caused by K. oxytoca.