Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce
Dissertation (MSc)--University of Pretoria, 2013.
Saved in:
| Other Authors: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
University of Pretoria
2014
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613696086245376 |
|---|---|
| access_status_str | Open Access |
| author2 | Buys, E.M. (Elna Maria) |
| author_browse | Buys, E.M. (Elna Maria) |
| author_facet | Buys, E.M. (Elna Maria) |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/41113 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:40:14.906Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/41113 Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce Buys, E.M. (Elna Maria) none Aijuka, Matthew Emmanuel Okello Bacteriological quality Irrigation water sources Contamination on irrigated lettuce UCTD Dissertation (MSc)--University of Pretoria, 2013. A deteriorating trend has been noted in the bacteriological quality of surface irrigation water sources in South Africa. In a bid to compare the bacteriological quality of two irrigation water sources as well as whether irrigation water was a source of bacterial pathogens on irrigated lettuce, this study was designed and divided into two phases. Phase one involved determination of physico-chemical parameters and bacterial indicators in the Loskop canal, the Skeerpoort river and lettuce irrigated with water from the Skeerpoort river over 10 months. Co-currently the study further determined the diversity of the most prevalent bacterial microflora in the 3 sample sources over the same time period. Aerobic colony counts (ACC), Aerobic spore formers (ASF), Anaerobic spore formers (AnSF), Faecal coliforms (FC), Intestinal enterococci (IE) and Staphylococcus aureus (S. aureus) as well as prevalence of Escherichia coli (E. coli), Salmonella spp and Listeria monocytogenes (L. monocytogenes) were determined. Additionally the most prevalent aerobic bacterial species isolated from the three sources were determined. Higher mean rainfall was noted in areas surrounding the Skeerpoort river (74.7mm) than the Loskop canal (0.1mm). Mean temperature was 15.4˚C and 18.2˚C while mean pH was 7.4 and 8.4 in the Loskop canal and the Skeerpoort river respectively. Low mean bacterial counts of less than 3.4 log10cfu/ml, were noted for ACC, ASF, AnSF, S. aureus and IE at both irrigation sites. Higher mean ACC of 5.9 log10cfu/g and S. aureus counts of 3.0 log10cfu/g were noted on lettuce. Although low mean counts of FC (1.3 log10cfu/100ml) were noted for all three sources, high incidence of E. coli was observed during bacterial composition studies on nonselective media. This suggested underestimation of faecal contamination possibly indicating that identification of specific pathogens provided a better measure of assessing bacterial contamination than bacterial indicators. E. coli, Bacillus spp and Enterobacter spp were the most prevalent bacteria in the Loskop canal, the Skeerpoort river and on lettuce. Prevalence of E. coli, Bacillus spp and Enterobacter spp in the Loskop canal was 23%, 33% and 26% respectively. Similarly prevalence in the Skeerpoort river was 36%, 26%, 16% respectively. On lettuce prevalence of the same bacteria was 36%, 30% and 6% respectively. E. coli O157:H7 was isolated at both irrigation sites while Salmonella enterica (gp 1) ST paratyphi A was isolated from the Skeerpoort river. High prevalence of similar bacterial species within the Loskop canal and the Skeerpoort river suggested similar sources of contamination in the two water sources inspite of different geographical location and surrounding land use practices. Additionally, similar bacterial species in irrigation water from the Skeerpoort river and on irrigated lettuce suggested water as a source of contamination on produce. Additionally it suggests ability of bacterial pathogens to withstand environmental conditions under field conditions which may pose a risk to food safety and public health among individuals consuming irrigated fresh produce. Phase 2 aimed at determining the prevalence of antibiotic resistant and virulent E. coli collected from the Loskop canal, the Skeerpoort river and lettuce irrigated with water from the Skeerpoort river. Forty one (41) E. coli isolates: (19) Loskop canal; (12) the Skeerpoort river; (10) lettuce were tested with 11 antibiotics at single concentrations and screened for Shigatoxin 1 (stx 1), Shigatoxin 2 (stx 2) and intimin (eae) genes. Antibiotic resistance was also used as a means of clustering E. coli isolated from the 3 sources. In the Loskop canal 84% and 83% of strains in the Skeerpoort river were resistant to at least one antibiotic. There was a significant difference (p≤0.05) in resistance to antibiotics between isolates from the Loskop canal and the Skeerpoort river. Additionally the combined effect of isolate source (irrigation water site) and antibiotics for isolates from the Skeerpoort river was significant (p≤0.05). From lettuce, 90% of isolates were resistant to at least one antibiotic and resistance significantly differed (p≤0.05) from isolates in the Skeerpoort river. The highest resistance to single antibiotics in all three samples was to cephalothin and ampicillin. Higher resistance was noted to multiple (more than 2) antibiotics in the Skeerpoort river (33%) than Loskop canal (5%). Most isolates from the same source showed close relatedness. Close relatedness was noted between isolates from the Loksop canal (10.5%) and the Skeerpoort river (16%). From irrigated lettuce 40% of isolates showed close relatedness to isolates in irrigation water from the Skeerpoort river. In the Loskop canal 15% and 41% of isolates in the Skeerpoort river possessed virulence genes. From lettuce, 20% of isolates possessed virulence genes. In the Loskop canal as well as from lettuce all isolates with virulence genes were antibiotic resistant while 80% of isolates with virulence genes in the Skeerpoort river were antibiotic resistant. In the Loskop canal 10% and 25% of isolates in the Skeerpoort river were positive for stx1/stx2 and eae, genes synonymous with Enterohaemorrhagic E. coli (EHEC). Results from this study show that E. coli from the two irrigation water sources as well as on irrigated lettuce were resistant to antibiotics and potentially pathogenic. This may increase risk of contaminating irrigated fresh produce which may compromise food safety and public health of consumers. gm2014 Food Science unrestricted 2014-08-08T10:06:00Z 2014-08-08T10:06:00Z 2014-04-15 2013 Dissertation Aijuka, MEO 2013, Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/41113> E14/4/333/gm http://hdl.handle.net/2263/41113 en © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Bacteriological quality Irrigation water sources Contamination on irrigated lettuce UCTD Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title | Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title_full | Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title_fullStr | Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title_full_unstemmed | Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title_short | Bacteriological quality of South African irrigation water and its role as a source of contamination on irrigated lettuce |
| title_sort | bacteriological quality of south african irrigation water and its role as a source of contamination on irrigated lettuce |
| topic | Bacteriological quality Irrigation water sources Contamination on irrigated lettuce UCTD |
| url | http://hdl.handle.net/2263/41113 |