Characterization of Adhesion and Invasion Virulence Factors in Streptococcus Pneumoniae, Shigella, and Salmonella Species Isolated from Ethiopian Patients

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Addis Ababa University


Pathogenic bacteria have multiple vilUlence factors that act in conceit to cause damaging effects in the host body. In this work few of the vil1llence factors interactions between pathogenic bacteria and human epithelial cells have been studied. Therefore, tissue adherence and invasion as well as haemagglutinating abilities of 50 strains of Streptococcus pl/eumol/iae, 25 Shigella spp. and 25 Salmol/ella spp. isolated fi'om patients were studied. The tissue adherence ability of these bacterial isolates was detected using cultured human epithelial cells (HEp-2 cells). In addition to the tissue adherence assay agglutination ability of the bacteria against six elythrocyte types was tested to find out if the same factors are involved in haemagglutination and adhesion to HEp-2 cells. The results of these tests showed that haemagglutination and tissue adherence abilities of the pathogenic bacteria are different. All Salmol/ella and Shigella isolates except one had adherence ability to HEp-2 cells. Unlike their adherence ability to HEp-2 cells, the haemagglutination result showed that only 13 strains of the Salmol/ella spp. and 17 strains of the Shighella spp. are haemagglutinating. Similarly, 43 (86%) of Streptococcus pllelllllolliae were able to adhere to HEp-2 cells and among these only 9 strains showed non-haemagglutinating ability. In the s. pl/eulllol/iae isolates, there were 6 strains that do not adhere to HEp-2 cells, and one was found to be neither haemagglutinating nor adhering to HEp-2 cells. The tissue invasion ability of the pathogenic bacteria was detelmined with a factor of2-In' intracellular growth incubation time and addition of exogenous gentamicin. The mvas\Veness ability of each strain was detennined as percentage of bacteria recovered from initial inoculum quantity of bacteria added to HEp-2 cell monolayer. From the invasiveness results all the Shigella and Salmol/ella isolates were able to invade the cultured epithelial cells with invasion results ranging between 1.26 and 32.93 %. In the case of Streptococcus pllelllllOl/iae isolates, only 12 out of the 50 strains were able to invade the cultured HEp-2 cells with invasion percentages ranging between 0.04 and 2.11 %. The remaining 38 strains could not invade the HEp-2 cells