Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 4, 2000
Publication Date: N/A
Interpretive Summary: Antimicrobial compounds are 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 and animal 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 microorganisms found in the feces and stored manure of domestic animals. As part of our project studying the bacterial populations of swine feces and manure storage pits, we investigated potential antibiotic resistance in anaerobic bacteria present in these environments. We now report on the isolation of a previously unidentified Lactobacillus species resistant to the antibiotics tylosin and erythromycin. This strain contains a plasmid capable of replicating in various bacterial species, conferring erythromycin/tylosin resistance on these species. These results indicate that these organisms may serve as reservoirs of antibiotic resistance genes. This information may be useful in developing management strategies that promote animal health and efficient production.
Technical Abstract: Anaerobic bacteria resistant to the macrolide antibiotics tylosin and erythromycin were isolated from the feces of swine. One of the strains, 121B, was initially identified by 16S rDNA sequence analysis as an unknown Lactobacillus sp. The strain was found to contain at least two plasmids, one of which was capable of replicating and providing erythromycin and tylosin resistance to Bacillus subtilis, Streptococcus gordonii, and Escherichia coli. DNA sequence analyses of the 4,232-bp plasmid p121BS, identified one open reading frame encoding a methylase gene highly similar (>98% amino acid identity, >99% DNA sequence identity) to the ermT gene from the Lactobacillus reuteri plasmid pGT633. This is only the second ermT gene to be reported. p121BS also contains two additional open reading frames with significant amino acid similarities to replication proteins from Lactobacillus and other Gram-positive bacteria.