Sources of Contamination and Their Mitigation Strategies in IVEP Laboratory: A Review

Abstract

In vitro embryo production (IVEP) depends on maintaining gametes and early embryos within an artificial environment that is both biologically permissive and sanitary. Contamination in this setting is broader than visible microbial growth. It includes pathogens and opportunistic microorganisms introduced with ovaries, follicular fluid, semen, serum, co-culture cells, personnel or equipment; endotoxin and inflammatory products; volatile and non-volatile chemical contaminants; degradation products in media and oil; particulates; and cross-contamination during cryostorage. This critical narrative review evaluates the sources, pathways, consequences and mitigation of these hazards, with emphasis on livestock IVEP and bovine systems, while using evidence from human assisted-reproduction laboratories only where shared culture technologies make cautious comparison informative. The literature indicates that source materials of animal origin constitute the dominant biological entry routes. Washing and antimicrobial supplementation lower some risks but do not reliably eliminate organisms that adhere to spermatozoa or the zona pellucida, particularly mycoplasmas, nor do they neutralise endotoxin. Evidence for chemical and physical contamination is mechanistically strong but frequently relies on model systems, before-and-after laboratory studies or quality-control assays whose sensitivity varies. Mineral-oil peroxidation, volatile-organic-compound transfer, ammonium accumulation and unstable physicochemical conditions can impair developmental competence without producing an overt contamination event. Cryobanking presents a distinct low-frequency, high-consequence problem when open devices or contaminated liquid nitrogen permit contact between specimens. Effective control therefore requires a layered system: qualified source materials, spatial and temporal segregation, validated aseptic processing, risk-based antimicrobial use, sensitive lot testing, controlled air and cleaning practices, closed or securely sealed cryodevices, traceability, trend-based monitoring and predefined incident response. The central unresolved problem is the scarcity of prospective livestock studies linking quantified exposures to transferable embryo quality, pregnancy, offspring health and disease transmission. Contamination control should consequently be treated as an integrated quality-management function rather than a single sterility procedure.