The prevalence and antibiotic resistant profiles of shiga-toxin producing Escherichia
coli 0157 strains isolated from faeces samples of cattle, pigs and human stool samples
were determined. The strains were further characterised by molecular methods for the
presence of shiga-toxin virulence genes and antibiotic resistant genes. Seventy-six
Escherichia coli 0157 strains were isolated and the prevalence was higher among E.
coli isolated from faeces from pigs (44.2% to 50%) than those from cattle faeces (5.4%
to 20.0%) or human stool samples (7 .5%). On testing E. coli 0157 isolates for their
resistance to 9 antimicrobial agents, multiple antibiotic resistance (MAR) was observed
in all of the isolates arising from resistance to three or more antibiotics. Seventy
(92.1 %) of the E. coli 0157 isolated from humans, cattle and pigs were resistant to
tetracycline. 73 (96.1 %) were resistant to sulphamethoxazole, 63 (82.9%) were resistant
to erythromycin. 40 (52.6%) were resistant to streptomycin and 26 (34.2%) were
resistant to ampicillin. The highest frequency of resistance was observed among the
human isolates (n=3 ), where 3 (I 00%) of the isolates were resistant to tetracycline,
sulphamethoxazole, erythromycin and ampicillin. Furthermore, among the pig isolates
(n=60), 58 (96. 7%) were resistant to tetracycline, 57 (95%) were resistant to
sulphamethoxazole, 47 (78.3%) were resistant to erythromycin. 38 (63.3%) were
resistant to streptomycin and 22 (36. 7%) were resistant to ampicillin.
The MAR phenotypes S-Smx-T-E, Smx-T-Ap and Smx-T-E were the dorminant
phenotypes among the E. coli 0157 isolated from the faeces samples of communal pigs
in 30.4%, 21 .7% and 17.4% of these isolates, respectively. However, phenotypes
Smx-T -E and S-Smx-T-E-Ne were identified at I6.2% and 10.8%, respectively within
the isolates obtained from commercial pig faeces. The phenotype Smx-T-E was the
only MAR phenotype identified among the E. coli 0157 isolated from the faecal
samples of commercial cattle at Lichtenburg. Furthermore, MAR phenotypes Smx-T-E-C,
K-S-Smx-T-E, S-Smx-T-E and Smx-T-E-Ap were obtained at 25%, respectively for
the isolates obtained from communal cattle at Mogosane while Smx-T-E-Ap was the
dorminant (66.7%) phenotype among the isolates of human origin. The phenotype
Smx-T fom1ed the basis of all the MAR phenotypes obtained and this was similar to the
percentage antibiotic resistance data.
The distribution of the resistant determinants for tetracycline was determined by PCR
analysis in resistant isolates. A tetB gene was detected in E. coli 0157 of pig origin.
Based on the characterisation of 30 isolates for the presence of STEC virulence genes
by PCR, 18 (60%) possessed the hlyA gene, 7 (23.7%) possessed the eae gene and 5
( 16. 7%,) harboured both genes.
The average MAR indices for pig, cattle and human E. coli 0157 isolates were 0.4n2,
0.3419 and 0.4814, respectively. Among the cattle isolates, the group MAR index was
highest for the communal (Mogosane) population while the values for the commercial
populations at Lichtenburg and Rustenburg were 0.33 and 0.22, respectively. £. coli
0157 isolated from pigs revealed MAR index results that were 0.508 and 0.415 for the
commercial and communal populations respectively and 0.1851 for the E. coli control
strains.
Characterisation by cluster analysis to determine the commonness and resolve
differences between the E. coli 0157 isolated from the Various sources revealed a close
association between pig (Tlapeng and Mareetsane), cattle (Mogosane) and human
isolates. Interestingly, E. coli 0157 isolated from pigs occurred at the highest frequency
in all the clusters. which suggested their role in the dissemination of resistant
determinants. / MSc. (Agric.) North-West University, Mafikeng Campus, 2006
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11220 |
| Date | January 2006 |
| Creators | Ateba, Collins Njie |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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