Effect of subtherapeutic concentrations of tylosin on the inhibitory stringency of a mixed anaerobe continuous-flow culture of chicken microflora against Escherichia coli O157:H7 |
| |
Authors: | Poole T L Genovese K J Knape K D Callaway T R Bischoff K M Nisbet D J |
| |
Institution: | United States Department of Agriculture, Agricultural Research Service, College Station Texas, USA. poole@ffsru.tamu.edu |
| |
Abstract: | AIMS: The aim of this study was twofold: first to determine the effect of subtherapeutic concentrations of tylosin, a macrolide antibiotic used for growth promotion, on a mixed anaerobic continuous-flow fermentation culture of chicken gastrointestinal microorganisms (CCF) and secondly, to determine if these concentrations would allow persistence of Escherichia coli O157:H7 in CCF. METHODS AND RESULTS: CCF was treated with tylosin at 10.0, 20.0 and 40.0 microg ml(-1). Tylosin treatment resulted in a significant (P < 0.0001) decrease in total volatile fatty acids (VFAs) from a mean concentration of 101 +/- 10.8 micromol ml(-1) in control cultures to 32.0 +/- 6.3 and 40.2 +/- 9.6 micromol ml(-1) in 10 and 40 microg ml(-1) treated cultures, respectively. Untreated CCF challenged with E. coli O157:H7 cleared the challenge microorganism in 7 days at a rate of 0.96 log10 CFU ml(-1) day(-1). In contrast, E. coli O157:H7 persisted in all tylosin treated cultures. CONCLUSIONS: In the presence of tylosin, E. coli O157:H7 was able to persist in the CCF culture. The significant decrease in the production of VFAs may have been a contributing factor. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of low-level, growth-promoting antimicrobials may compromise the ability of normal microflora that serve as a natural host defence against infection. |
| |
Keywords: | anaerobes bacteroides competitive exclusion E coli O157:H7 enterococcus tylosin veillonella |
本文献已被 PubMed 等数据库收录! |
|