Oxitec larvae are reared in the presence of tetracycline. Pupae are washed several times in fresh water as part of the sorting process. They are then reared in fresh water, with no tetracycline. When larvae become pupae and metamorphose into adults, they expel their gut bacteria, meaning any tetracycline-resistant bacteria in the larval gut are highly unlikely to be continued into the adults. In addition, the cuticle (skin of insects) is a very inhospitable environment for bacteria; it is smooth and dry, unlike human skin which harbors many different bacteria species. Therefore, the chances of any bacteria surviving on the cuticle of the mosquitoes is extremely low.
The adult mosquitoes emerge from the pupal case onto the surface of clean water and are not exposed to any tetracycline thereafter.
At Oxitec, we take our stewardship of antibiotic use very seriously. That’s why we minimize use, monitor it, and have subjected it to detailed review.