Influence of temperature on survival and conjugative transfer of multiple antibiotic-resistant plasmids in chicken manure and compost microcosms.

The aim of this study was to determine if mobile plasmids carrying antibiotic-resistant genes could survive and be transferred in chicken manure maintained under conditions similar to those found in commercial cage layer operations and during composting. Escherichia coli J5 harboring a self-transmissible plasmid (RP4) and E. coli C600 harboring a mobile plasmid (pIE723) were used as plasmid donors; E. coli CV601 was used as a plasmid recipient. At 23 degrees C both plasmids were transferred to E. coli CV601 in chicken manure and in compost microcosms that consisted of a mixture of chicken manure and peat. The transfer frequencies ranged from 8.1 x 10(-5) to 2.4 x 10(-3) per donor cell in manure and from 2.4 x 10(-5) to 5.5 x 10(-4) per donor cell in compost microcosms. After 45 d of incubation at 23 degrees C, RP4, but not pIE723, was recovered by an exogenous isolation method although their E. coli hosts were not cultured from the microcosms. However, when the temperatures of the compost microcosms were elevated to 50 degrees C or above, neither the plasmids nor their E. coli hosts could be detected. The results suggested that composting of chicken manure at high temperatures could help prevent the spread of antibiotic-resistant genes via plasmids in the environment.