Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2005
Publication Date: 8/1/2005
Citation: Wang, Y., Wang, G., Shoemaker, N.B., Whitehead, T.R., Salyers, A.A. 2005. Distribution of the ermG gene among bacterial isolates from porcine intestinal contents. Applied and Environmental Microbiology. 71(8):4930-4934. Interpretive Summary: Antimicrobial compounds have been commonly used as feed additives for domestic animals to reduce infection and promote growth. Recent reports have suggested such feeding practices may result in increased microbial resistance to antibiotics, which can have an impact on human health. While many investigations have centered on antibiotic resistance in coliforms and other aerobic bacteria, less attention has been directed towards investigating antibiotic resistance in the anaerobic microflora found in the feces and stored manure of domestic animals which may serve as reservoirs of antibiotic resistance genes. As part of our project on determining the bacterial populations of swine feces and manure storage pits, we are investigating potential antibiotic resistance in anaerobic bacteria present in these ecosystems. We report here the first finding of the erythromycin resistance ermG gene in gram-positive bacteria isolated from swine feces and from under barn manure pits used to store swine wastes. Our results show that the ermG gene is more widespread than previously thought, and that horizontal gene transfer of this gene between bacteria is occurring in multiple sites. This information will be of use to other researchers and environmental agencies.
Technical Abstract: The ermG gene was first found in the soil bacterium, Bacillus sphaericus. More recently, it was found in human intestinal Bacteroides species. We report here the first finding of ermG genes in gram-positive bacteria isolated from porcine feces and from under barn manure pits used to store porcine wastes. The porcine ermG sequences were identical to the sequence of the B. sphaericus ermG gene except that six of the seven ermG-containing strains contained an insertion sequence element inserted in the C-terminal end of the gene. The porcine ermG genes were found in three different gram-positive genera, an indication that the gene may be being spread by horizontal gene transfer. A segment of a Bacteroides conjugative transposon that carries an ermG gene cross-hybridized with DNA from six of the seven porcine isolates, but the restriction pattern in the porcine strains was different from that of the Bacteroides CTn.