| The detect of foodborne pathogens from food proceccing surface plays an important role in food security control, in this study, a filter paper sampling technology was established after a series of experiments and optimizations. After this, we analysised the viable and VBNC cell counts of foodborne pathogens from surfaces which were undergo a series of environment stresses, thermal treatment, frozen storage, starvation stress and normal conditions. The details of this research were as follows:We analysised the viability of S. aureus, Salmonella and L. Monocytogenes within five kinds of transport medias stored at 4℃ and 25℃ over a 24-h period, and the ease with which the bacteria were released from the directly inoculated filter paper, finally the recovery of bacteria from surfaces by six kinds of wetting solutions were estimated. The results were as follows: Minimal bacterial growth occured when the samples were stored at 4℃, which is proper for samples storage; at room temperature, the survival of bacteria differs in transport medias, the counts of three kinds of bacteria can be stable simultaneous only in PBS, the release rates of bacterias from filter papers were high, the recovery of pathogens from surfaces is highest when the filter paper was premoistened with 0.85% saline solution supplemented with 0.1% Tween-80 and 0.1% peptone. The final optimized procedure was as follows: filter paper was premoistened with 0.85% saline solution supplemented with 0.1% Tween-80 and 0.1% Peptone, then was placed on the stainless steels surface. After vortexing in 10 ml of phosphate buffered saline solutions, the filter paper was used for quantitative analysis.The present method was also compared with the cotton swab sampling method to evaluate its recovery efficiency. The results showed that,the recovery of S. aureus, Salmonella and L. Monocytogenes was 5.84% ± 1.51%, 10.60% ± 4.84%, 1.76% ± 0.60% by filter paper sampling method from surfaces inoculated by 108 CFU/100cm2 bacterias, there was no obvious difference between the two methods(P>0.05). The detection limit of the filter paper based sampling method for S. aureus, Salmonella and L. monocytogenes was 2.78, 3.33 and 4.40 Log(CFU/100cm2), respectively. Furthermore, the filter paper based sampling method holds the advantages of simple, fast, effective, easy to operate, reproducible and can improve sampling effiency in a large amount of work. Taken together, the presently established filter paper based method have a potential in the foodborne pathogens detection from food processing surface.The counts of pathogens from contact surfaces in the normal condition detected by the filter paper sampling method showed varying degree of injure exists, it may caused by sampling and analysis procedure. As for strains in our experiment, S. Aureus has minimal injure, Salmonella followed, L. Monocytogenes is most sensitive one to this procedure, so analysis for L. Monocytogenes from surfaces by metheds based on sawb sampling may has low recovery, because of sampling loss; the recovery of thermal damaged pathogens from contact surfaces by the filter paper sampling methed didn’t reduce by the Sublethal injury satate of pathogens, so the filter paper sampling method procedure may not be significant harmful for thermal damaged pathogens from surfaces; pathogens from surfaces be subject to starvation stress or-18℃ frozen storage over a 24-h period can not bring high degree of reduce in bacteria viable counts, but produced a large amount of Sublethal injury; the three kinds of pathogens here be more toleranced to starvation stress than-18℃ frozen storage; both pathogens in the four experimental conditions’ s viable counts and culturable counts have significant difference, this means a large amout of VBNC cells. So the study of environment contact surfaces is essential. |
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