Contamination spread within biosafety cabinets during wiping and its transfer to gloves: Quantitative assessment of cleaning risks

Introduction Cell processing facilities commonly employ manual wiping to decontaminate biosafety cabinet (BSC) surfaces during changeovers between manufacturing lots. Although wiping is intended to remove contaminants, it may also inadvertently redistribute them across surfaces or transfer them to operators’ gloves. Quantitative data on the impact of wiping techniques, repetition, and surface materials on the dispersion and transfer of biological contaminants within BSCs remain limited. This study systematically evaluated the spread of contamination during wiping operations in BSCs, focusing on three representative indicators: DNA, protein, and viable bacteria. Methods The redistribution of contaminants on stainless steel (SUS304) and polyethylene terephthalate surfaces was evaluated using DNA, protein, and Bacillus subtilis endospores as model indicators. Two wiping protocols were evaluated: multi-pass wiping (reusing the same sheet) and replacement wiping (using a new sheet after the source area), each performed either once or four times with ethanol-moistened nonwoven sheets under standardized mechanical conditions based on EN 16615:2015. Residual DNA and protein were quantified fluorometrically (n = 6 per condition), whereas bacterial surface contamination was measured by contact culture (n = 12 per condition). Bacterial transfer to gloves was evaluated across increasing numbers of wiping sheets (n = 16 per sheet-number condition). Results DNA and protein residues predominantly persisted in the source area under all conditions, with minimal transfer to adjacent areas. However, measurable residues persisted in the source area even after four wiping cycles. By contrast, viable bacteria were readily redistributed to the affected area during multi-pass wiping, whereas bacterial detection in the affected area was less frequent during replacement wiping. Bacterial transfer to gloves decreased monotonically with an increasing number of wiping sheets (Cramér's V = 0.82; Cochran–Armitage trend test, p = 1.7 × 10 −14 ). Conclusions Wiping operations within BSCs serve both as decontamination steps and potential vehicles for contamination redistribution. These findings provide quantitative evidence for implementing replacement wiping strategies, increasing the frequency of sheet changes, and incorporating nonmicrobial residue indicators into changeover validation for cell processing facilities.