Microbial contamination in an in vitro fertilization-embryo transfer system.

OBJECTIVE: To determine sources and transmission of microorganisms in IVF-ET and efficacy of in-place controlling systems.
DESIGN: Prospective study.
SETTING: In Vitro Fertilization-Embryo Transfer Unit at a university teaching hospital. PATIENTS: Twenty-eight couples undergoing 30 completed IVF-ET cycles.
INTERVENTIONS: Gamete and embryo processing in a penicillin and streptomycin-rich medium. MAIN OUTCOME MEASURES: Presence of microorganisms at various stages of IVF-ET. Fertilization, cleavage, and pregnancy rates.
RESULTS: In 50% of cycles no microorganisms were isolated and in the other 50% microbes were cultured from various loci. Cultures of four preprocessed semen samples were positive and corresponding postprocessed samples negative. Microbes were detected in 27% of needle washes after oocyte collection; in 40% and 32% of follicular fluids from left and right ovaries, respectively; and in two culture media from egg-sperm incubations at 20 hours after insemination. No microorganisms were grown from media from zygote incubations. Fertilization, cleavage, and pregnancy rates were independent of microbial presence.
CONCLUSION: Seminal fluid and transvaginally collected oocytes are potential sources of microbial contamination of the IVF-ET culture system. A penicillin- and streptomycin-rich culture medium is effective in removing contaminating microbes. End point measures are not affected by commensal contamination.