Contribution of Capsule to Virulence and Antibiotic Sensitivity of Klebsiella ozaenae Identified by Phenotypic and Molecular Methods

Abstract

The respiratory colonizer K. ozaenae can cause a broad spectrum of infections, and it always misdiagnoses by phenotypic procedures. The role of capsule has not been proved in K. ozaenae yet. One hundred (100) clinical specimens were taken from patients suffering different infections. After phenotypic identification by cultural, microscopic, and biochemical tests, the suspected K. ozaenae isolates subjected to molecular identification using 16S rRNA gene. The non-capsulated K. ozaenae isolate was prepared from higher muco-viscous capsulated K. ozaenae isolate. Mice were injected intraperitoneally by capsulated and non-capsulated K. ozaenae, then bacterial burden in the spleen, liver, and blood was compared and histopathological lesions were detected in liver. Susceptibility of K. ozaenae with and without capsule to different antibiotics concentrations was tested at 600nm wavelength. Phenotypically, 3 (3%) isolates of K. ozaenae were identified, while results of 16S rRNA gene were concordant in 2/3 (2%) isolates and discordant in 1/3 (1%) isolate. Significant differences were showed between the increased log number of capsulated K. ozaenae isolate and decreased log number of non-capsulated K. ozaenae isolate that recovered from mice spleen, liver, and blood. Severe pathological lesions were observed in mice liver infected by capsulated K. ozaenae compared with non-capsulated K. ozaenae isolate. No-significant differences were found between the growth of capsulated and non-capsulated K. ozaenae isolate treated with the same antibiotic concentration. 16S rRNA are useful molecular tool to avoid misidentification of K. ozaenae. Removal of capsule decreases virulence of K. ozaenae, but not affect its sensitivity to antibiotics.