کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2467854 | 1555412 | 2010 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Comparison of the effects of different nutrient media on production of heat-stable enterotoxin-b by Escherichia coli Comparison of the effects of different nutrient media on production of heat-stable enterotoxin-b by Escherichia coli](/preview/png/2467854.png)
Trypticase soy broth (TSB) has been commonly used to culture Escherichia coli strains for detection or harvest of heat-stable enterotoxin-b (STb); however, in our experience, the yields have been low. In this study, we compared STb yields resulting from growth in brain heart infusion broth (BHI) supplemented with 2% casamino acids (BHI-CA) with that from TSB. Since strains may concurrently express heat-labile enterotoxin (LT) and lincomycin has been reported to cause increased expression of LT, we also compared its effects on STb production. STb+ clones had significantly higher production of STb when grown in BHI-CA compared to TSB, based on enzyme-linked immunosorbent assay (ELISA) conducted on cell-free supernatants. The superiority of BHI-CA to TSB was further tested on 17 porcine enterotoxigenic E. coli (ETEC) isolates, all positive for the STb gene (estB) by PCR. Cell-free supernatants of 100% of the ETEC isolates were detectably positive for STb by ELISA when grown in BHI-CA, in contrast to only 10 strains positive (59%) when TSB supernatants were analyzed. For all the samples, the amounts of STb expressed in BHI-CA based on ELISA were significantly higher than those from TSB (p ≤ 0.03). Incorporation of lincomycin at a concentration optimal for LT production into these media caused a significant decrease in STb levels, and use of both lincomycin and polymyxin B at these concentrations abolished detectable STb production altogether. We conclude that BHI-CA is a better medium for supporting STb production than is TSB. Culture in BHI-CA followed by testing by STb-ELISA is a useful combination for detecting STb production.
Journal: Veterinary Microbiology - Volume 144, Issues 1–2, 29 July 2010, Pages 160–165