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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
Author(s) -
Poole T.L.,
Genovese K.J.,
Knape K.D.,
Callaway T.R.,
Bischoff K.M.,
Nisbet D.J.
Publication year - 2003
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1046/j.1365-2672.2003.01802.x
Subject(s) - tylosin , escherichia coli , microbiology and biotechnology , fermentation , biology , microorganism , bacteria , enterobacteriaceae , antibiotics , antimicrobial , food science , biochemistry , genetics , gene
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 μg 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 μmol ml −1 in control cultures to 32·0 ± 6·3 and 40·2 ± 9·6 μmol ml −1 in 10 and 40 μg 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 log 10 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.