Bacteria collected in mosquito breeding ponds were evaluated for resistance to streptomycin, chloramphenicol, penicillin and trimethoprim. Mycelial growth of Lagenidium giganteum isolates from Australia, United States and Colombia were evaluated in PYG media containing one antibiotic or a mixture of these compounds. Media containing chloramphenicol reduced mycelial growth of most of the isolates. The antibiotic mixtures and penicillin-streptomycin penicillin-trimethoprim did not significantly affect mycelial growth of the isolates; however, the later substantially reduced bacterial contamination.