Klebsiella pneumoniae is a member of the pathogenic group which causes a variety of human disease and outbreak problem in Hospitals. These organisms challenged the treatment by multidrug resistance. Furthermore, to develop new strategies and prevent bacterial pathogen outbreak must be studying virulence mechanisms, virulence factors and role of these factors in pathogenicity. Fifty K. pneumoniae isolates were recovered from different collected clinical specimens from Ain Sham Specialized (Ksp) and Al-Damardash Hospitals (KD) Cairo, Egypt, also from Sabha medical center Hospital (Ksa) Sabha, Libya. Isolates were identified by phenotypic and physiological methods by using API 20 E system. In general, the K. pneumoniae (KD & Ksp) isolates displayed higher adherence rate to Vero cells and cytotoxicity too. These results were exhibited significantly (P>0.05). Twenty percent were at higher adherence range (>8%) and 16% of cytotoxicity at very high level (50%) by none significantly (P0.05) was between adherence and invasion results for K. pneumoniae (KD & Ksp) and (Ksa) strains. Finally, we showed that both wild type strains were able to resistant serum killing by a resistance rate of 64% and 80%, while intermediate was resistance by 36% and 12%, respectively.
Key words: K. pneumoniae, Invasion, Adherence, Cytotoxicity, Serum resistant, Capsule