ARS | Publication request: Antimicrobial Susceptibility of Lactobacillus Species Isolated from Fuel-Ethanol Plants

Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract
Publication Acceptance Date: May 25, 2006
Publication Date: May 25, 2006
Citation: Bischoff, K.M., Skinner, K.A., Leathers, T.D. 2006. Antimicrobial susceptibility of lactobacillus species isolated from fuel-ethanol [abstract]. American Society for Microbiology. Poster No. O-038.

Technical Abstract: Bacterial contamination of commercial fermentation cultures is a common and costly problem to the fuel ethanol industry. Antimicrobials such as tetracycline (TET), penicillin G (PEN), and virginiamycin (VIR) are frequently used to control contamination but there are little data available on the susceptibility of bacterial contaminants to these agents. A survey of bacterial contaminants from a wet-mill ethanol plant with no history of using antibiotics and a dry-grind facility that periodically doses with virginiamycin found that the majority of contaminants were species of Lactobacillus. Forty-one isolates of Lactobacillus species from the wet-mill and thirteen isolates from the dry-grind facility were tested for antimicrobial susceptibility to TET, PEN, and VIR using broth dilution and agar dilution methods. In general, the Lactobacillus isolates from the dry-grind plant had higher MICs for all three agents than the isolates from the wet-mill facility: 69% (9/13) versus 22% (9/41) with an MIC of >/=16 ug/ml for TET; 31% (4/13) versus 2% (1/41) with an MIC of >/=4 ug/ml for PEN; and 54% (7/13) versus 2% (1/41) with an MIC of >/=1 ug/ml for VIR. All thirteen Lactobacillus isolates from the dry-grind plant but none from the wet-mill possessed vatE, a gene that codes for a streptogramin acetyltransferase associated with resistance to VIR. Despite decreased susceptibility, most isolates had MICs lower than the maximal application rate used for these antimicrobials.