Influence of selected antibiotics on the response of black fly (Simulium vittatum) larvae to insecticidal proteins produced by Bacillus thuringiensis subsp. israelensis.
A controlled current toxicity test (CCTT) was developed to evaluate the response of black fly (Simulium vittatum) larvae to insecticidal proteins following exposure to various antibiotics. The bacterium, Bacillus thuringiensis subsp. israelensis (Bti), produces proteins that are toxic to Nemotoceran Diptera, such as black flies and mosquitoes, when ingested. These insecticidal crystalline proteins (ICPs) are highly efficacious in controlling black flies; however, speculation has arisen regarding the potential for antibiotic contamination of waterways to mitigate the toxicity of these proteins. A series of experiments was conducted with the CCTT in which black fly larvae were exposed to enrofloxacin, tylosin, sulfamethoxazole, and trimethoprim followed by exposure to Bti ICPs. These antibiotics were selected based on their use in agricultural and documented anthropogenic contamination of rivers. Anthropogenic concentrations of a mixture of these four antibiotics did not affect the response of the larvae to Bti ICPs. Subsequent experiments were conducted with antibiotic concentrations 10,000 to 80,000 times higher than those found in contaminated rivers. Exposure of black fly larvae to high levels of enrofloxacin (0.5 mg/L) had no effect upon the susceptibility to Bti ICPs; however, exposure to high levels of tylosin (8 mg/L) resulted in a significant increase in the susceptibility of the larvae to Bti ICPs at 72 h of exposure, but not at 48 h. Exposure of black fly larvae to high concentrations of a mixture of sulfamethoxazole and trimethoprim resulted in a significant increase in the efficacy of the larvicide after 48 and 72 h of exposure. These results suggest that impairment of the efficacy of Bti ICPs to black fly larvae is not due to antibiotic contamination of the larval environment.
Iburg
Joseph P
JP
Department of Entomology, Riverbend Research Laboratory-North, The University of Georgia, 110 Riverbend Road, Athens, Georgia 30602, USA. jpiburg@gmail.com
Gray
Elmer W
EW
Wyatt
Roger D
RD
Noblet
Raymond
R
D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000633:toxicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004731:Endotoxins / Q000737:chemistry / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000633:toxicity*; D007306:Insecticides / Q000737:chemistry / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D012843:Simuliidae / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity
D000900:Anti-Bacterial Agents; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D014874:Water Pollutants, Chemical; C030956:insecticidal crystal protein, Bacillus Thuringiensis