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Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd.
Mini Dissertation (MSc (Production Animal Studies))--University of Pretoria, 2025.
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University of Pretoria
2025
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| _version_ | 1867613661364748289 |
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| access_status_str | Open Access |
| author2 | Petzer, Inge-Marie |
| author_browse | Petzer, Inge-Marie |
| author_facet | Petzer, Inge-Marie |
| collection | Thesis |
| dc_rights_str_mv | © 2023 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 | Mini Dissertation (MSc (Production Animal Studies))--University of Pretoria, 2025. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/100505 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:39:41.715Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| 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:2263/100505 Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. Petzer, Inge-Marie grantvanlelyveld@gmail.com Karzis, Joanne Van Lelyveld, Grant Kevin UCTD Sustainable Development Goals (SDGs) Streptococcus uberis Molecular characterisation Slurry Bovine mastitis Mini Dissertation (MSc (Production Animal Studies))--University of Pretoria, 2025. Streptococcus uberis is a significant emerging mastitis pathogen with environmental and hostadaptive properties. Mastitis caused by Strep. uberis is increasing in South Africa, particularly in pasture-based herds irrigating with slurry. This field study aimed to identify strain types using MALDI-TOF and MLST and evaluate the Strep's behavioural patterns (host-adaptive versus environmental). uberis isolates over an extended period from a South African dairy herd with a high prevalence of Strep. uberis intramammary infection. The study involved 70 (63 retrospective and seven recent) samples, isolated from 53 cows, which were used for MLST sequencing of the seven housekeeping genes (gki, recP, ddl, tdk, arc, tpi, and yqiL). The study disclosed a herd prevalence of 7.44% Strep. uberis intramammary infection (IMI), responsible for 21.26% of clinical mastitis cases in this herd. Of the Strep. uberis positive clinical cases, 25% had repeat occurrences during the same lactation period. The consecutive repeat Strep. uberis cases were 34 (2x), 13 (3x), and 7 (4x). The study identified 41 novel Strep. uberis strain types from 64/70 isolates, attributable to novel alleles (29) or novel sequences of existing alleles of previously identified alleles. The study revealed that one existing Strep. uberis strain type (ST) 1613 (6/70) was to be identified and belonged to the clonal complex (CC) ST-86. All the other strain types of the isolates investigated in this study were novel. They were within the common CC (ST-5, ST-86, and ST-143) or not allocated (owing to the lack of data generated from whole genome sequencing). The longitudinal study 2021 (three-monthly milk samples) n=64/70 and 2024 (specific milk samples) n=7/70 from cows identified as high-interest cows, possibly showing as chronic cases on repeat collections (culture, MALDI-TOF, and Kirby Bauer). The finding was not entirely down to suspected hostadaptive strains of Strep. uberis but relatively novel strains creating new infections. The heterogeneity of the Strep. uberis isolates in this study agreed with other research identifying the environment as the primary source of strains. This study can aid farmers and veterinarians in managing Strep. uberis mastitis is more effective in the field by better classifying what is meant by repeat, non-cure, and new infections amid farming practices favouring higher pathogen loads (environment) and challenges for the cows. Contrary to what was expected, the study identified new infections with diverse Strep caused most suspected chronic intramammary infection (IMI). Uberis strains are dominated by novel environmental strains (high heterogeneity of ST and CC from all 70 isolates). Production Animal Studies MSc (Production Animal Studies) Unrestricted Faculty of Veterinary Science SDG-03: Good health and well-being 2025-02-04T07:42:16Z 2025-02-04T07:42:16Z 2025-04 2025 Mini Dissertation * A2025 http://hdl.handle.net/2263/100505 https://doi.org/10.25403/UPresearchdata.28341920 en © 2023 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 | UCTD Sustainable Development Goals (SDGs) Streptococcus uberis Molecular characterisation Slurry Bovine mastitis Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title | Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title_full | Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title_fullStr | Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title_full_unstemmed | Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title_short | Molecular characterization of Streptococcus uberis strains, isolated in a longitudinal study from milk of a commercial South African dairy herd. |
| title_sort | molecular characterization of streptococcus uberis strains isolated in a longitudinal study from milk of a commercial south african dairy herd |
| topic | UCTD Sustainable Development Goals (SDGs) Streptococcus uberis Molecular characterisation Slurry Bovine mastitis |
| url | http://hdl.handle.net/2263/100505 https://doi.org/10.25403/UPresearchdata.28341920 |