ESTIMATION OF LOD OF DETECTION OF PROTEUS SPP. IN SURFACE SAMPLES

Microbiological contamination of surfaces in food production facilities and food-handling areas represents a major challenge in preventing cross-contamination and selecting biocidal products. Consequently, examining the microbiology purity of surfaces that come into contact with food requires a serious methodological approach.

This paper presents the method of determination of Proteus spp. from surface samples (5x5 cm²). The three levels of artificial soiled aluminium foil were prepared using bacterial suspensions of Proteus hauseri ATCC 13315. After the surface swabbing method for determination of Proteus spp. was applied. The swab was homogenized with Eugon LT 100 broth and 1 mL was transferred to enrichment broth. After incubation of the enrichment broth, streaking on the Brilliant green agar and SS agar was performed. The characteristic colonies were confirmed by biochemical reactions.

The number of positive findings of Proteus hauseri on the applied level of contamination was used for calculation by the PODLOD_ver12.xls ECEL program by Wirlich and Wilrich. This program estimates the probability of detection (POD) function and the limit of detection (LOD) of qualitative microbiological methods.

The results of the detection of Protues hauseri in surface samples showed a LOD_{50% ⁼}48.957 [24.596; 97.446] CFU in 1 ml of swab rinse, and LOD_95%=211.589 [106.303; 421.155] CFU in 1 mL of swab rinse.

These results open a discussion about the performance of the applied method. Also, they provide ideas for further research related to the type of surface, the type of used swab sticks and the type of microorganisms tested.