This study describes the molecular characteristics of STEC isolated from the pastoralist community of Nyabushozi in Southwestern Uganda. Faecal samples or rectal swabs of children with diarrhoea obtained in phases 1 and 2 were investigated for the presence of STEC by PCR detection of stx genes. During phase 1, cattle reared on range which were associated with households of sick children were investigated in parallel to the children for STEC excretion. STEC was isolated from E. coli in 7 of 80 (8.8%) children and in 15 of 216 (6.9%) bovines in phase 1. Similarly, STEC was isolated from 11 of 142 (7.7%) E. coli carrying children and 3 of 45 (6.7%) water samples in phase 2. Molecular characterization further ascertained the genetic relatedness of STEC. PFGE pro les of up to 10 colonies obtained from an individual source (child, bovine or water) and in total 185 STEC colonies were analysed. Nine pro les from 43 colonies (phase 1) and 15 pro les from 38 colonies (phase 2) obtained from children were not or were distally related, indicating the genetic diversity of clinical STEC. The intra-host analysis of STEC pro les revealed that strains from 11 of the 13 children exhibited multiple clonal subgroups. The 101 colonies from 15 bovines clustered in 18 di erent pro les. Clonal subgroups were observed in multiple STEC colonies from 11 of 12 bovines. Closely related pro les indicated that STEC isolated from two children (Hh2 and Hh4) was acquired from bovines or their environment. While none of the clinical or bovine STEC were related to 5 genetically diverse water strains. A single isolate of STEC representing each PFGE pro le in association with stx gene content was serotyped for the O antigen. Twenty four bovine STEC were typed into 10 O serogroups including O8, O76, O111 and O113, which were also identi ed among the clinical STEC. The 25 clinical STEC belonged to 15 serogroups of which O29, O149 and O176 are being reported for the rst time as clinical STEC. STEC xxi Abstract O166 was isolated from a child and water during the same sampling, indicating the potential health hazard of drinking STEC-contaminated water. The production of Shiga toxin (Stx) investigated using Duopath Verotoxin detection kits showed that a majority of STEC from di erent sources produced Stx1 or Stx2 or both Stx. Using PCR or PCR-RFLP assays, stx2 and eae gene types were analysed. Variant stx2 vhc was most prevalent and closely associated with stx2d2 in clinical and bovine STEC. The frequency of eae-positive STEC among clinical and bovine STEC was 15 of 25 (60%) and 14 of 24, (58.3%), respectively. eae- 2/ was predominant among the bovine STEC, eae- / in clinical STEC, while eae- 1 was associated with STEC from di erent sources including water. Previously undescribed eae-positive serogroups O28ac, O113, O142 and O158 were identi ed. Studies of the genetic background showed that both clinical and bovine STEC obtained in phase 1 predominantly belonged to phylogenetic group A and B1, while phase 2 clinical and water STEC belonged to group D and A, respectively. Seropathotype classi cation of clinical STEC, separated most strains (20 of 24 strains) into seropathotype D. These STEC belonged to phylogenetic groups A, B1 and D. Thus, the characterised genetic attributes of STEC from Nyabushozi suggests that the pathogens have the potential to cause a wide spectrum of childhood illnesses ranging from mild to bloody diarrhoea and haemolytic uraemic syndrome. xxii
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/3063 |
| Date | January 2009 |
| Creators | Majalija, Samuel |
| Contributors | Elisha, B Gay |
| Publisher | University of Cape Town, Faculty of Health Sciences, Institute of Infectious Disease and Molecular Medicine |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Doctoral Thesis, Doctoral, PhD |
| Format | application/pdf |
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