| Autor: |
Atalla, Heba, Gyles, Carlton, Jacob, Christian L., Moisan, Helene, Malouin, François, Mallard, Bonnie |
| Zdroj: |
Foodborne Pathogens & Disease; December 2008, Vol. 5 Issue: 6 p785-799, 15p |
| Abstrakt: |
AbstractStaphylococcus aureusis a common cause of bovine mastitis and foodborne and other diseases in humans. This study tested the hypothesis that small colony variants (SCVs) of S. aureusare implicated in chronic bovine mastitis. Six S. aureusisolates from foremilk samples from 11 chronically infected cows were investigated. Five isolates had typical morphology and were hemolytic and coagulase positive; one was a heterogeneous population of typical and SCV phenotype (tiny nonhemolytic colonies). In the presence of gentamicin, three of the previously typical S. aureusdeveloped SCVs that were confirmed as S. aureusby biochemical and genetic analyses; these SCVs reverted to the typical form on antibiotic-free medium. The SCV isolate (Heba3231) from the heterogeneous population had a slow growth rate and prolonged lag phase and did not revert during 10 h of incubation. Transcriptional analysis showed that SCV Heba3231 had reduced expression of agr, hla, and coaand increased expression of indicators of fermentation pathways compared to the parent strain. Invasion of and persistence in a primary culture of bovine aortic endothelial cells (BAEC) showed that SCV Heba3231 had minimal deleterious effects, whereas the parent strain or the Newbould 305 strain caused severe damage. Recovery of the parent strain from BAEC yielded a mixture of the parent and SCV phenotypes. This study reports for the first time the isolation of S. aureusSCV from persistent bovine mastitis and suggests that SCV may be an important contributor to the prolonged survival of S. aureusin some cases of mastitis. |
| Databáze: |
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