彰化地區犬隻之困難梭狀芽孢桿菌分離率調查

Isolation Rate of Clostridium difficile in Dogs in Changhua County

洪麗瓊(Li-Chiung Hung)

指導教授 ： 陳德勛

共同指導教授 ： 周崇熙

國立臺灣大學/獸醫專業學院/獸醫學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201901380

摘要

困難梭狀芽孢桿菌（Clostridium difficile）是一種革蘭氏染色陽性且會形成芽孢的厭氧性桿菌，會引發人類之自限性腹瀉，嚴重感染則可能導致偽膜性大腸炎（pseudomembranous colitis）、毒性巨結腸症（toxic megacolon）等，並可能造成病人的敗血症甚至死亡。雖然困難梭狀芽孢桿菌感染症（C. difficile infection；CDI）傳統上被認為是因醫療干預而導致院內感染的疾病，但近年來各國社區型困難梭狀芽孢桿菌感染症（community-acquired C. difficile infection；CA-CDI）比率有上升的趨勢，且根據研究其中有數種核醣型也同時在牛、豬、馬及犬等動物中被分離出來，以至於被認為困難梭狀芽孢桿菌有人畜共通傳染的可能。由於犬隻是與人類生活最親密的伴侶動物之一，因此，本研究針對彰化縣的家犬與流浪犬隻進行困難梭狀芽孢桿菌採樣並計算其分離率，進一步調查毒力基因型別的分布狀態並使用E試驗法進行藥物感受性試驗，最後以統計學方法分析各因子間的交互關係。2014年1月至5月間共採集435頭犬隻的糞便樣本，經檢測得知困難梭狀芽孢桿菌總分離率為7.13%（31/435），其中家犬的分離率為14.14%（28/198）與流浪犬的分離率1.27%（3/237）具有極顯著相關（p＜0.0001）。困難梭狀芽孢桿菌總毒力基因（tcdA+/tcdB+/cdt-）的分離率為58.06%（18/31），其中17株來自家犬，另1株來自流浪犬；且家犬來源的C. difficile產毒株分離率8.59%（17/198）亦極顯著高於流浪犬的0.42%（1/237）（p＜0.0001）。而糞便型態與困難梭狀芽孢桿菌分離率及毒力之關係、流浪犬隻年齡與困難梭狀芽孢桿菌分離率之關係、不同犬隻族群困難梭狀芽孢桿菌分離株與對抗生素不具感受性之關係，以及困難梭狀芽孢桿菌產毒分離株與對抗生素不具感受性之關係，均不具統計學上之關聯性。在藥物感受性試驗中，所有分離株對於metronidazole及vancomycin這2種抗生素，皆具有感受性；然有25.81%（8/31）的分離株對moxifloxacin不具感受性，該8株皆是由家犬來源的糞便樣本檢出，且其中7株為產毒株，顯示家犬可隨糞便排出具有抗藥性且具毒力的困難梭狀芽孢桿菌芽孢汙染環境。一旦確立了犬隻與人類的人畜共通傳染風險，根據本研究的結果顯示，家犬排出的產毒株困難梭狀芽孢桿菌芽孢可能會對公眾健康構成風險並且可能導致人類CA-CDI疫情的發生。

關鍵字

困難梭狀芽孢桿菌 ； 犬 ； 分離率 ； 毒力基因 ； 藥物感受性

並列摘要

Clostridium difficile is an anaerobic, spore-forming Gram-positive bacillus that is able to cause self-limited diarrhea in humans. Serious infection may cause pseudomembranous colitis and toxic megacolon, and may lead to sepsis or even death in patients. Although Clostridium difficile infection (CDI) has traditionally been considered as a hospital-associated disease due to medical intervention, the ratio of community-acquired C. difficile infection (CA-CDI) is escalating in recent years. Several ribotypes of C. difficile isolated from animals such as cattle, pigs, horses, and dogs were also collected from human patients; therefore, C. difficile was considered to have a zoonotic potential to human being. Since dogs are the most intimate companion animals with human, this study surveyed the isolation rate of C. difficile from pet dogs and stray dogs in Changhua area, and further carried out the detection of toxin genes, antimicrobial susceptibility tests by E-test, and measured the correlation between various factors. A total of 435 stool samples were collected from January to May 2014, and the total isolation rate of C. difficile was 7.13%（31/435）. The isolation rate of C. difficile in pet dogs and stray dogs were 14.14% (28/198) and 1.27% (3/237), and displaied a statistically significant correlation (p＜0.0001). The total prevalence rate of toxin gene was 58.06% (18/31); the prevalence rate of toxin gene in pet dogs and stray dogs were 60.71% (17/28) and 33.33% (1/3), and displaied a statistically significant correlation (p＜0.0001). Furthermore, there were no significant relationship correlation between fecal forms and isolation rate, fecal forms and toxin genes, ages and isolation rate, canine populations and antimicrobial resistance, toxin genes and antimicrobial resistance. The results of antimicrobial susceptibility tests showed that all isolates were susceptible to metronidazole and vancomycin. In addition, there were 25.81% (8/31) isolates were not sensitive to moxifloxacin. The 8 isolates were detected from stool samples of pet dogs, and 7 of them were toxigenic strains, indicating that pet dogs have more opportunity to possess toxigenic and drug-resistant C. difficile with spores in stools and contaminate the environment. If the zoonosis risk between dogs and human were established, the findings in this study indicate the pet dogs posing a
risk for the public health and the possibility to cause CA-CDI in human.

並列關鍵字

Clostridium difficile ； dogs ； isolation rate ； toxin gene ； antimicrobial susceptibility

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