Removal of external bacteria from C. elegans

Dear All

I am looking for a method for removing bacteria that may have adhered
externally to C. Elegans, but will not remove ingested bacteria that may
have established an infection in the worm.

I have tried washing worms with antibiotics for differing lengths of time,
but the worms appear to ingest this and the internal bacteria are also
destroyed. I also tried washing them in chlorinated tap water, and
separately, a rinse in ph 4. The last was maybe the most effective, but
still doesn't remove all external bacteria. I plan to test the efficacy of
external removal of bacteria using confocal microcopy. If anyone has any
established methods for external removal of bacteria I would be very
interested to hear from them. Any further ideas will be much appreciated.

Best, Sarah