台灣零售雞肉分離之Salmonella enterica serovar Schwarzengrund 之污染率調查研究、抗生素耐性、分子分型分析及細胞侵入性之探討

Abstract

沙門氏菌能引起人類、家禽、家畜及野生動物之間的相互感染，也為引起人類細菌性胃腸炎主要病因之一，尤其是雞肉、豬肉和蛋品被認為是沙門氏菌傳染人類的主要來源。Salmonella Schwarzengrund 是一會感染人類與家禽之沙門氏菌血清型。本研究調查了於2000年至2006年間分離自台灣地區傳統市場販售雞肉之 Salmonella Schwarzengrund 之分布情形，並將228株 Salmonella Schwarzengrund 分離株，進行抗藥性圖譜及菌株親緣性分析，同時與任意挑選自2004年至2006年間分離之30株人類來源分離株進行比較，以期提供治療及流行病學之參考。 結果顯示，其中30.5%的雞肉檢體遭 Salmonella Schwarzengrund 汙染，而所有分離自雞肉檢體之沙門氏菌中，Salmonella Schwarzengrund 占了39.3％。同時，雞肉來源及人類來源的菌株皆為多重抗藥性菌株，其抗微生物藥劑圖譜相似，對常見的抗微生物製劑如 ampicillin、gentamicin、 kanamycin、streptomycin、 tetracycline、 nalidixic acid、 trimethoprim-sulfamethoxazole 及chloramphenicol 均具有高抗藥性，僅對第三代頭孢素較為敏感。抗藥性圖譜之研究指出人類用藥與畜牧用藥有不當使用的可能性，且雞肉來源及人類來源的菌株之間亦有傳播的可能。 本研究以脈衝式膠體電泳(PFGE) 進行次分類，當所有分離株之DNA利用XbaI酵素作用後，主要之型別為X1、 X3及 X2，而以AvrII酵素作用後，主要之型別為A2、 A14及 A1。當結合XbaI與AvrⅡ這二種酵素作用的型別分析，主要型別則為X3A2、X1A2 及 X2A1。而由脈衝式膠體電泳的結果可知：利用一種以上之限制酵素可改善分型鑑別力。此外，因屬於主要型別之菌株是在不同年度，自台灣不同地區分離而得，故這些型別也許是代表台灣地區菌株之主要次分型。而且，這些次分型之菌株可能是在台灣地區傳統販售雞肉市場中重複散佈。 另一方面，Salmonella Schwarzengrund 對於動物及人類為具侵入性之沙門氏菌血清型。本研究之目的在於探討不同分子分型與侵入的關係及雞肉來源及人類來源菌株的侵入性比較。結果顯示，不同分子分型分離株其侵入並無顯著不同，且同一型別之菌株期侵入能力亦不盡相同，此外，結果亦顯示，人類來源菌株的侵入性較高。

Salmonella spp. are transmitted among human, poultry, domestic animal and wild animal, and are the major pathogens to cause dietary gastroenteritis in human through in contact with chicken, pork and egg-products. Salmonella Schwarzengrund is one of the infective Salmonella serotypes for humans and food animals, such as poultry and swine. In this study, the prevalence of Salmonella Schwarzengrund contamination in chicken meat samples purchased from different traditional marketplaces in Taiwan between 2000 and 2006 was investigated. In addition, 228 Salmonella Schwarzengrund strains isolated from these chicken meat samples and 30 human isolates obtained between 2004 and 2006 were compared for their antimicrobial susceptibility and phylogenic relationship. Such data will help to identify new targets for therapy and hence aid epidemiology. Results showed that the prevalence of Salmonella Schwarzengrund contamination in raw chicken meat samples was 30.5%. Of all the Salmonella isolates from chicken meat, S. Schwarzengrund accounted for 39.3%. All these chicken meat isolates were multidrug resistant and demonstrated high resistance to ampicillin, gentamicin, kanamycin, streptomycin, tetracycline, nalidixic acid, trimethoprim-sulfamethoxazole, and chloramphenicol. The antibiogram study may indicate the abuse of some antibiotics for both humans and chickens. Also, transmission of Salmonella Schwarzengrund strains between humans and food of animal origin is possible. Pulsed field gel electrophoresis (PFGE) was used for molecular typing in this study. The major PFGE patterns for XbaI and AvrII digested DNAs were type X1, X3, X2 and type A2, A14, A1, respectively. When these XbaI and AvrII digestion patterns were combined for strain typing, the major subtypes were X3A2, X1A2 and X2A1. The PFGE results indicate that for typing of Salmonella Schwarzengrund, using more than one restriction enzyme would improve the discrimination power of PFGE significantly. Since most of the chicken meat isolates in these major patterns were originally isolated from samples obtained from various areas in Taiwan over different years, these PFGE patterns may represent the major subtypes for Taiwan strains. Also, it is possible that strains in these major subtypes are those recirculating in traditional chicken meat retail marketplaces. Salmonella Schwarzengrund was one of the highly invasive serotypes to food animals and humans. In this study, we attempt to elucidate the relationship between their molecular subtypes and their invasiveness. Meanwhile, the invasiveness for Salmonella Schwarzengrund isolated from chicken meat and humans were also compared. Results showed that Salmonella Schwarzengrund strains of the major subtypes were not necessary among the highly invasive strains, and strains within the same subtype showed differences in invasiveness capability. In addition, human isolates of Salmonella Schwarzengrund showed higher invasion rates than chicken meat isolates.