Erythromycin

Erythromycin is used in human medications to treat gram-positive infections in people who are allergic to penicillin. It has a broader range than penicillin but it has very limited effect against gram-negative bacteria.

In fish disease literature, erythromycin is often cited as one of the drugs that bacteria infecting fish develop resistance to.

Action

Erythromycin binds with ribosome, interfering with protein synthesis in bacteria, and hence cell growth.

In a study conducted at several Belgium universities, it was determined that erythromycin inhibits nitrification. The danger of using this drug is fish ammonia poisoning.

Effective Against

Erythromycin is effective against most gram-positive bacteria and to a very limited extent, gram-negative bacteria.

Erythromycin is used in the aquaculture industry to treat bacterial kidney disease (BKD), a systemic disease of salmonids, responsible for high mortality rates. There has been some speculation that kidney disease in tropical ornamental fish may be the result of the same type of bacteria infecting salmonids.

The wasting or "skinny" disease found in guppies, a condition often affecting females after birth, may be the result of internal bacteria and not as previously speculated, fish tuberculosis. There is anecdotal evidence that erythromycin may be effective against this disease.

Treatment Regime

Erythromycin is most effective when introduced into water that is neutral or slightly alkaline. Acid breaks down the drug.

It is more effective administered orally. It is mixed in with food at the rate of 2.0 gm/lb of food and given for 10 days.

It can also be bioencapsulated in brine shrimp, either nauplii or adult brine shrimp. This is the most effective treatment, since the guppies will ingest the drug at relatively high concentrations.

It can also be combined with gelatin and used as a coating food. The mixture is 2.0 gm/lb of food, given for 10 days.

It can be incorporated in fish food pastes.

Where to Get

Erythromycin is found in fish medications, including Mardel Maracyn and Aquarium Pharmaceuticals E.M. Tablets. Erythromycin is also available at the pharmacy, but in many countries, like Canada, they are only available via a doctor's prescription. The drug is available as a fish medication on the Internet.