Cleaning agent fungal biofilm removal rate test

Medical YongCleaning agent fungal biofilm removal rate test

Fungal biofilm has become a hidden challenge in the prevention and control of medical equipment infections. Clinical data shows that Candida albicans biofilm can increase the risk of medical equipment related infections by 3.2 times, and the extracellular polysaccharide matrix (EPS) formed by it can reduce the penetration efficiency of fungicides by more than 60%. In 2024, a study in the Chinese Journal of Hospital Infection indicated that the detection rate of fungal biofilms in endoscopic lumens accounted for 27% of biofilm positive samples, with a high detection rate of 41% for Candida biofilms in ICU environments. Therefore, Doctor YongCleaning agent fungal biofilm removal rate testIt has become a core indicator for evaluating the clinical applicability of cleaning agents.

The International Organization for Standardization (ISO) established a dedicated testing system for ISO 18472:2019 "Evaluation of Fungal Biofilm Removal Efficiency in Medical Device Sterilization" in 2019, which requires the fungal biofilm removal rate of luminal instruments to reach a log value reduction of ≥ 4.0; GB/T 38502-2020 "Evaluation Method for Antifungal Properties of Medical Equipment Biofilms" in China further stipulates that standard biofilms should be prepared using 316L stainless steel carriers (surface roughness Ra 0.8-1.6 μ m), and the initial bacterial count should be controlled at 5-7 log CFU/cm ². The YY/T 0734.4-2025 "Medical cleaning agents Part 4: Determination of fungal biofilm removal" implemented in 2025 innovatively introduces the "temperature gradient culture method", which distinguishes the differences in fungal and bacterial biofilm characteristics through dual temperature culture at 28 ℃/37 ℃, significantly improving detection specificity.

The verification of fungal biofilm clearance requires a three-level detection system of 'culture counting morphology'.

As the gold standard for fungal culture, Sabouraud Dextrose Agar (SDA) requires the addition of Chlortetracycline (50 μ g/mL) to inhibit bacterial contamination. After 72 hours of cultivation at 28 ℃, the characteristic colony morphology of Candida albicans is observed - it appears as cream colored circular colonies with neat edges; Aspergillus forms green fuzzy colonies. The XTT reduction method is used to quantify metabolic activity by detecting the reduction product of 3- (4.5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide. The absorbance is measured at 490nm and shows a linear relationship with the number of viable bacteria (R ² ≥ 0.98). The detection limit can reach 5 × 10 ² CFU/cm ².

Laser scanning confocal microscope (LSCM) is a key equipment for morphological verification.

Stain the carrier with Calcofluor White (fluorescent whitening agent), and under 405nm excitation light, the fungal cell wall exhibits strong blue fluorescence. Calculate the biofilm thickness (normal ≤ 8 μ m) and coverage (required ≤ 5%) using ImageJ software. The typical biofilm of Candida albicans presents a 'yeast hyphae' mixed structure, and residual pseudohyphae network can be seen penetrating the EPS matrix when the bottom is not cleared.

The testing laboratory needs to be equipped with a fungal specific biosafety cabinet (Biosafety Level 2), a constant temperature oscillation incubator (28 ℃± 0.5 ℃, oscillation rate 120rpm), and a fluorescence microscope (equipped with DAPI and FITC dual filters). The control of key operating parameters directly affects the reliability of the results: when inoculating the carrier, 0.1mL of bacterial suspension (1 × 10 ⁶ CFU/mL) should be uniformly coated and vacuum dried for 15 minutes; The cleaning simulation requires the use of a rotating lumen cleaning device with a flow rate controlled at 2mL/min to simulate clinical endoscopic flushing conditions. The comparative study of Laboratory Medicine in 2025 shows that the fungal recovery rate of different brands of SDA culture media can differ by up to 18%. It is recommended to use each batch of culture media as a positive control (Candida albicans ATCC 10231 standard strain).

The validation of fungal biofilm clearance requires simultaneous evaluation of three core indicators: clearance rate (surgical instruments ≥ 99.99%, endoscopes ≥ 99.999%), residual viable bacteria (implant requirement ≤ 10 CFU/piece), and EPS degradation rate (high performance liquid chromatography method for measuring glucan content ≤ 2 μ g/cm ²). Methodological validation must meet the requirements of precision (RSD ≤ 15%), recovery rate (70% -130%), and detection limit (10 CFU/cm ²). The 2024 capability verification results of the China National Institute for Food and Drug Control show that only 58% of laboratories can pass both bacterial and fungal biofilm detection simultaneously, and the main source of error is the low elution efficiency caused by the heat resistance of fungal spores (average recovery rate of 62%).

The result judgment implements a graded qualification system: Class I (implants) must simultaneously meet the requirements of a clearance rate of ≥ 99.999% and no visible biofilm in LSCM; Class II (endoscopy) requires a clearance rate of ≥ 99.99% and XTT activity<10%; A clearance rate of ≥ 99.9% for Class III (conventional instruments) is considered qualified. Typical unqualified cases include: a certain brand of multi enzyme cleaning agent has a clearance rate of 99.98% for Candida albicans, but only 89.7% for Candida albicans (due to differences in chitin content in EPS); The removal rate of fungal biofilm by a certain low-temperature cleaning agent decreased by 2.3 log values at 20 ℃ compared to 37 ℃.

Fungal biofilm detection faces special technical challenges.

The preparation of simulated pollution carriers requires controlling the ratio of spores to mycelium. The microporous membrane filtration method (0.45 μ m pore size) is used to separate yeast and mycelium phases, ensuring that the mycelium ratio in the initial biofilm is ≥ 30%. The detection of luminal instruments requires the use of fluorescently labeled spores (CFDA-SE staining), and the distribution of biofilms in the lumen depth (≥ 1m) is observed through confocal endoscopy. The latest research shows that adding 1% bovine serum albumin can increase fungal biofilm resistance by 45%. It is recommended to prepare the contaminated solution formula according to the ratio of 'fungal suspension+20% artificial saliva'.

The clinical relevance verification of test results is the core challenge. Establish a correlation equation between in vitro clearance rate and animal infection model. Through subcutaneous implantation experiments in rats, it was found that an in vitro clearance rate of 99.99% corresponds to a 91% reduction in in in vivo infection rate. It is recommended that companies specify the 'strain specificity' of fungal biofilm removal in the product manual, and if it is targeted at Aspergillus, the action time should be extended to 1.5 times that of conventional methods. With the full implementation of GB 32630-2025 "General Requirements for Medical Cleaning Agents", the removal efficiency of fungal biofilm will become a key indicator for market access of cleaning agents, promoting the industry's transformation and upgrading from "broad-spectrum sterilization" to "precision anti biofilm".

Medical institutions should establish a fungal biofilm risk monitoring system: quarterly biofilm screening should be conducted on medical equipment used in high-risk departments such as ICU and oncology; When replacing the cleaning agent, it is necessary to simultaneously verify the effectiveness of fungal removal. Cleaning agent manufacturers should strengthen the research on enzyme formulation compounding. In vitro experiments have shown that the combination of chitinase and glucanase can increase the biofilm clearance rate of Candida albicans by 1.8 log values. Future detection technology will develop towards real-time monitoring, such as developing an online monitoring system for biofilm thickness based on fiber optic sensors to achieve dynamic optimization of the cleaning process.