潮鯛生魚片生產廠中沙門氏菌汙染模式調查

Abstract

人類沙門氏菌症所造成的醫療和經濟損失一直是全世界重要之公共衛生議題。遭沙門氏菌汙染的食品為傳播沙門氏菌給人類之重要媒介，其中不乏加工即食魚產品。食品加工過程被認為是造成即食產品污染的重要來源之一。因此本研究以台灣南部兩家潮鯛生魚片生產廠進行為期兩年的調查，目的為瞭解生魚片生產廠之汙染模式及可能的汙染來源。樣本採集自魚塭蓄養池、運輸設備、生產加工廠和終產品，其中，生產加工廠於開工前即進行環境設備採樣，開工後每兩個小時採樣一次直至加工作業完成，共計2646個樣本，總分離率為2.3%（61/2646）。生產過程分為五個階段，包括凍昏處理、放血去鱗、去內臟、清洗消毒及包裝。A廠五個階段分離率為0%到4.3%，僅於凍昏處理區、放血區和去內臟區分離到沙門氏菌，終產品並無分離到；B廠在五個階段及終產品中均分離到沙門氏菌，分離率為3.2%到9.2%，開工前環境設備中即分離到沙門氏菌（4.7 %），開工後分離率更提高至10.1%，表示加工過程導致沙門氏菌分離率上升。其中，沙門氏菌累積汙染的現象更說明加工廠之環境及設備為汙染重要來源之一。利用PFGE和REP-PCR兩種分子分型鑑定，結果皆指出沙門氏菌交叉汙染的問題在加工作業時發生，且有持續汙染的現象。但加工廠中臭氧清洗消毒作業對於降低和控制沙門氏菌汙染問題是具有正面效果。本研究亦指出S. Newport、S. Bareilly和S. Weltevreden不僅為潮鯛生魚片加工廠中常見的血清型，亦為台灣人類沙門氏菌症病例中常分離到之血清型，顯示沙門氏菌在潮鯛生魚片生產廠之汙染對消費者具潛在之公共衛生危害。

Human Salmonellosis has been a crucial public health problem worldwide. Ready-to-eat（RTE）products contaminated by Salmonella have been recognized as a critical vehicle transmitting Salmonella to humans. Food processing might be one of the important contamination sources in RTE Food. In this 2-year study, we attempted to illustrate the contamination pattern and any possible contamination sources in RTE fish processing plants. We collected 2,646 samples from two tilapia sashimi processing plants in southern Taiwan. Sampling was taken from the fish farm, transportation facilities, processing plant and final products. Before reaching the processing plant, the first sampling was taken and continued 2 more sampling time points until the processing was over resulting in an overall isolation rate of 2.3%（61/2646）. Processing works in the processing plants were divided into five sections including freezing, scaling and bleeding, visceral removal, cleaning and disinfection, and packaging. Salmonella was only isolated from the freezing, bleeding, and visceral removal sections in plant A and isolation rates in five sections ranged from 0% to 4.3%. No Salmonella was isolated from the final products in plant A. In plant B, Salmonella was isolated from all sections as well as final products and the rates ranged from 3.2% to 9.2%. Before processing, the isolation rate was 4.7% but afterwards it was 10.1% revealing that Salmonella contamination increased as processing was conducted. The phenomenon of accumulated contamination indicates that the environment and the facilities acted as vital sources of contamination during processing. Results of molecular subtyping（including PFGE and REP-PCR）suggest that not only cross-contamination but also persistant-contamination of Salmonella was occurring within the processing plant. Certain improvements such as periodic disinfection may be beneficial for reducing and controlling the microbial contamination. In this study, S. Newport, S. Bareilly and S. Weltevreden were common serotypes isolated from processing plants and they are also prevalent serotypes in Taiwan human salmonellosis cases suggesting that contaminated sashimi processing facilities possessed potential public health risk to the consumers.