Pathogenic bacteria have multiple vilUlence factors that act in conceit to cause damagingrneffects in the host body. In this work few of the vil1llence factors interactions betweenrnpathogenic bacteria and human epithelial cells have been studied. Therefore, tissuernadherence and invasion as well as haemagglutinating abilities of 50 strains ofrnStreptococcus pl/eumol/iae, 25 Shigella spp. and 25 Salmol/ella spp. isolated fi'om patientsrnwere studied.rnThe tissue adherence ability of these bacterial isolates was detected using cultured humanrnepithelial cells (HEp-2 cells). In addition to the tissue adherence assay agglutinationrnability of the bacteria against six elythrocyte types was tested to find out if the samernfactors are involved in haemagglutination and adhesion to HEp-2 cells. The results ofrnthese tests showed that haemagglutination and tissue adherence abilities of the pathogenicrnbacteria are different. All Salmol/ella and Shigella isolates except one had adherencernability to HEp-2 cells. Unlike their adherence ability to HEp-2 cells, thernhaemagglutination result showed that only 13 strains of the Salmol/ella spp. and 17 strainsrnof the Shighella spp. are haemagglutinating. Similarly, 43 (86%) of Streptococcusrnpllelllllolliae were able to adhere to HEp-2 cells and among these only 9 strains showedrnnon-haemagglutinating ability. In the s. pl/eulllol/iae isolates, there were 6 strains that dornnot adhere to HEp-2 cells, and one was found to be neither haemagglutinating norrnadhering to HEp-2 cells.rnThe tissue invasion ability of the pathogenic bacteria was detelmined with a factor of2-In'rnintracellular growth incubation time and addition of exogenous gentamicin. ThernmvasVeness ability of each strain was detennined as percentage of bacteria recoveredrnfrom initial inoculum quantity of bacteria added to HEp-2 cell monolayer. From therninvasiveness results all the Shigella and Salmol/ella isolates were able to invade therncultured epithelial cells with invasion results ranging between 1.26 and 32.93 %. In therncase of Streptococcus pllelllllOl/iae isolates, only 12 out of the 50 strains were able torninvade the cultured HEp-2 cells with invasion percentages ranging between 0.04 andrn2.11 %. The remaining 38 strains could not invade the HEp-2 cells