title: Brugia malayi: effects of antibacterial agents on larval viability and development in vitro.
abstract: Recent studies have suggested that intracellular Wolbachia bacteria are necessary for reproduction and survival of adult filarial worms. We now report results of in vitro studies of effects of antibacterial antibiotics (tetracycline, rifampicin, chloramphenicol, azithromycin, and doxycycline) on Brugia malayi infective larvae (L3) motility and molting. All of the antibiotics tested except chloramphenicol decreased L3 motility by 50% or more at 10 days, with minimal effective concentrations (MECs) of 20-100 microg/ml. Tetracyclines, rifampicin, and chloramphenicol inhibited L3 to L4 molting by 12 days in a concentration- and time-dependent manner, with MECs in the range of 1-20 microg/ml. These studies show that antibiotics active against Rickettsiaceae inhibit B. malayi L3 molting at low concentrations in vitro; higher concentrations kill the larvae. While it is possible that antibiotics directly affect filarial L3, we believe it is more likely that the effects seen are indirect effects related to bacterial killing.
authors.affiliation: Infectious Diseases Division, Internal Medicine Department, Barnes-Jewish Hospital and Washington University, School of Medicine, St. Louis, MO 63110, USA. rrao@im.wustl.edu
authors.forename: Ramakrishna U
authors.initials: RU
authors.lastname: Rao
authors.forename: Hanaa
authors.initials: H
authors.lastname: Moussa
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Weil
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology; D017178:Brugia malayi / Q000187:drug effects* / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D002701:Chloramphenicol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D018978:Molting / Q000187:drug effects; D009068:Movement / Q000187:drug effects; D012293:Rifampin / Q000494:pharmacology; D013752:Tetracycline / Q000494:pharmacology; D013997:Time Factors; D020577:Wolbachia / Q000187:drug effects / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D002701:Chloramphenicol; D017963:Azithromycin; D013752:Tetracycline; D004318:Doxycycline; D012293:Rifampin