Sisay, Tesfaye (Professor)Alefew, Bewekete2021-09-152023-11-182021-09-152023-11-182021-03-03http://etd.aau.edu.et/handle/12345678/27893Diarrheagenic E. coli strains (DEC) are associated with many disease outbreaks and sporadic cases mostly in children and calves. Traditionally serotyping of the pathogen is based upon the conventional serotyping using their surface O and H antigens. However, this method has its own drawbacks and as a result cost- effective, rapid and more sensitive detection method is required. Thus, the objective of this study was to identify the serotypes of diarrheagenic E. coli isolated from diarrheic calves and children from different parts of Ethiopia using three multiplex PCR assays. In the present study a total of 280 DEC isolates from diarrheic children (n=116) and calves (n=164) were distinguished based on their O-antigen gene clusters particularly, wzx (O-antigen filppase) and wzy (O- antigen polymerase). Results revealed that 12 (10.34 %) isolates from diarrheic children and 18 (10.97%) isolates from calves were found to be positive for one of the targeted O-serogroup specific primers used. A total of 12 O-serogroups were identified among the 21 O-serogroups targeted based on their importance in clinical cases. Of the identifiable serotype in diarrheic children O15, 8(6.89%), was the most frequently detected serotype. While in diarrheic calves the most frequently detected serotype was O55, 5(3.04%). Moreover, O55 and O128 serotypes were identified in both diarrheic calves and children. Furthermore, O15 was more distributed across three sampling sites, such as in Jimma 3(2.59%), Addis Ababa sub cities 3(2.59%) and Hawassa 2(1.72%) from diarrheic children. In diarrheic calves O55 was identified from Fiche 3(1.82%), Bahirdar 1(0.60%) and South Wollo 1(0.60%). Out of 12 O-serogroup samples detected from diarrheic Children 25% belonged to Enteropathogenic E.coli (EPEC) and while 8.33% were Enterohemorhagic E.coli (EHEC) and Shiga toxin producing E.coli. The 18 O-serotypes detected from diarrheic calves were classified to STEC, EPEC, and EHEC strains at 27.77%, 16.66%, and 16.7% respectively. The common serogroups O15, O118, O128, and O55 were identified in children and in calves O55, O123, O128, O145 and O26 were detected. From these, O128 and O55 are potentially involved in zoonotic transmission. The finding clearly indicates the potential of multiplex PCR to serotype diarrheagenic E. coli isolates. Thus, further use of Multiplex PCR for serotyping of diarrheagenic isolates in Ethiopia and elsewhere is highly recommended.enMultiplex PcrDiarrheagenic EColiEthiopiaWzx and Wzy GeneSerotypingThesis