比較不同增菌培養基檢測傳統市場食品與環境的沙門氏菌帶菌狀況

Comparison of Different Enrichment Media for Detection of Salmonella in Food and Environment of Traditional Markets

馮品瑄(Pin-Xuan Feng) ； 吳昕庭(Hsin-Ting Wu) ； 歐柏廷(Po-Ting Ou) ； 蔡文城(Wen-cherng Tsai)

《檢驗及品保雜誌》 10卷2期 (2021/04) Pp. 75-82

https://doi.org/10.6573/JTQA.202104_10(2).04

摘要

從食品或臨床檢體中檢測沙門氏菌，除了直接接種分離培養基外，亦需使用增菌培養基以提升沙門氏菌檢出的效能。常用於分離沙門氏菌的增菌培養基包括食品檢驗常用的Rapport-Vassiliadis（RV）肉湯（broth）與tetrathionate（TT）broth以及臨床糞便檢體常用的selenite brilliant green sulfa broth（SBG）broth與SBG TransCultSwab，為了瞭解這些增菌培養基於檢測食品中沙門氏菌的效能，本研究利用從三個傳統市場購買的100件生鮮食品，包括雞肉、豬絞肉、生蠔與生魚和25件即時食品以及25件以棉拭採集的市場環境檢體進行評估。操作食品檢驗時，將25 g檢體先以225 mLTSB滋養培養基稀釋10倍後進行第一次增菌培養，而環境檢體則直接培養，兩類檢體於隔日再分別移種於上述三種增菌培養基進行第二次增菌。將RV broth，TT broth與SBG broth三種增菌培養基培養24±2小時。另外，以SBG TransCultSwab所提供的棉拭塗抹各類食品檢體的表面，將SBG TransCultSwab培養16～24小時後，再將棉拭移種Salmonella checker，隨後培養24～48小時。上述增菌方法在培養後再分別移種至選擇性xylose lysine desoxycholate（XLD）agar平板培養基，培養隔日，再將疑似的沙門氏菌菌落以四區劃線法移種TSA進行純化，再分別利用mat rix-assisted laser desorption ionization time-of-flight mass spectrometry系統與傳統生化試驗方法進行鑑定。結果顯示生鮮原料食品與即時食品中沙門氏菌氏檢出率分別為59％（59／100）與0％（0／25），而環境檢體為44％（11／25）。生鮮食品原料檢驗中，RV broth、TT Broth、SBG broth、SBG TransCultSwab的沙門氏菌檢出率分別為59％（59／100）、19％（19／100）、14％（14／100）與33％（33／100）。吾等發現：（i）傳統市場生鮮原料食品檢體與環境檢體具有高的（59％與44％）沙門氏菌帶菌率：（ii）傳統市場即食食品並無沙門氏菌的汙染：（iii）用於沙門氏菌檢驗的增菌培養基以衛福部公告方法所建議的RV broth最具檢出效能，TT broth檢出的沙門氏菌都能由RV broth檢出：（iv）SBG TransCultSwab-Salmonella checker組合方法對雞肉（屠體）的沙門氏菌檢出率與RV broth相當，分別為76％（19／25）與80％（20／25），指出此組合適用於禽、畜類屠體之高通量沙門氏菌檢測。以及（v）臨床糞便檢體常用的沙門氏菌的增菌培養基如SBG broth或SBG Trans CultSwab並不適用於屠體以外之食品的增菌。

關鍵字

沙門氏菌 ； 增菌培養基 ； Rapport-Vassiliadis (RV) broth

並列摘要

Enrichment media are required for detection of Salmonella from food or clinical samples. Commonly used enrichment media for food samples include Rapport-Vassiliadis (RV) broth and tetrathionate (TT) broth, and those for clinical specimens include selenite brilliant green sulfa broth (SBG) and SBG TransCultSwab. To determine whether enrichment media for clinical specimens can be used for food samples to detect Salmonella, we examined 25 environment specimens collected with swabs from various places in markets, 25 ready-to-eat foods, and 100 fresh raw foods including ground pork, chicken, oyster, and fish, purchased from three traditional markets. Each swab of environmental specimen was placed in 5 mL of 0.1% peptone water, and 25 g of each food specimen was placed in 225 mL of trypticase soy broth (TSB). Each of these cultures was incubated overnight and then transferred into RV broth, TT broth, and SBG broth. After 24±2 hours of incubation, each enriched sample was subcultured on a selective medium xylose lysine deoxycholate agar (XLD) plate for isolation of Salmonella spp. Meanwhile, a swab from SBG TransCultSwab was used to smear the surface of each food specimen and then inserted into SBG TransCultSwab. After 16 to 24 hours of incubation, each swab was transferred to a Salmonella checker and incubated for 24-48 hours. Each of the inoculated Salmonella checker that turned black was subcultured on an XLD agar plate. Colonies suspected to be of Salmonella spp. were separately streaked on TSA plates for purification, and purified organisms were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and traditional biochemical tests. Results showed that 59% (59/100) of food samples and 44% (11/25) of environment samples were positive for Salmonella and that Salmonella detection rates for fresh raw food samples enriched with RV Broth, TT Broth, SBG broth, and SBG TransCultSwab were 59% (59/100), 19% (19/100), 14% (14/100), and 33% (33/100), respectively. We also found the following: (i) Fresh raw foods sold in traditional markets have a high (59%) salmonella contamination rate. (ii) Ready-toeat foods from traditional markets are free of Salmonella contamination. (iii) The most effective enrichment medium for Salmonella detection from foods is RV broth, which is the method recommended by the Ministry of Health and Welfare, and both TT broth and RV broth can be used to detect Salmonella. (iv) The rate of Salmonella detection from chicken carcasses by the combination of SBG TransCultSwab and Salmonella checker is 76% (19/25), very similar to that by RV broth (80%, 20/25), suggesting that this combination is suitable for Salmonella detection from poultry and livestock carcasses. (v) The enrichment media, such as SBG broth or SBG TransCultSwab, for Salmonella detection commonly used for clinical stool specimens are not suitable for food specimens other than those of carcasses.

並列關鍵字

Salmonella ； enrichment medium ； Rapport-Vassiliadis (RV) broth