Istituto Zooprofilattico Sperimentale del Mezzogiorno, Via Salute, 2, 80055, Portici, Italy.
BMC Vet Res. 2012 Oct 25;8:201. doi: 10.1186/1746-6148-8-201.
Salmonellosis in water buffalo (Bubalus bubalis) calves is a widespread disease characterized by severe gastrointestinal lesions, profuse diarrhea and severe dehydration, occasionally exhibiting a systemic course. Several Salmonella serovars seem to be able to infect water buffalo, but Salmonella isolates collected from this animal species have been poorly characterized. In the present study, the prevalence of Salmonella spp. in water buffalo calves affected by lethal gastroenteritis was assessed, and a polyphasic characterization of isolated strains of S. Typhimurium was performed.
The microbiological analysis of the intestinal contents obtained from 248 water buffalo calves affected by lethal gastroenteritis exhibited a significant prevalence of Salmonella spp. (25%), characterized by different serovars, most frequently Typhimurium (21%), Muenster (11%), and Give (11%). The 13 S. Typhimurium isolates were all associated with enterocolitis characterized by severe damage of the intestine, and only sporadically isolated with another possible causative agent responsible for gastroenteritis, such as Cryptosporidium spp., Rotavirus or Clostridium perfringens. Other Salmonella isolates were mostly isolated from minor intestinal lesions, and often (78% of cases) isolated with other microorganisms, mainly toxinogenic Escherichia coli (35%), Cryptosporidium spp. (20%) and Rotavirus (10%). The S. Typhimurium strains were characterized by phage typing and further genotyped by polymerase chain reaction (PCR) detection of 24 virulence genes. The isolates exhibited nine different phage types and 10 different genetic profiles. Three monophasic S. Typhimurium (B:4,12:i:-) isolates were also found and characterized, displaying three different phage types and three different virulotypes. The molecular characterization was extended to the 7 S. Muenster and 7 S. Give isolates collected, indicating the existence of different virulotypes also within these serovars. Three representative strains of S. Typhimurium were tested in vivo in a mouse model of mixed infection. The most pathogenic strain was characterized by a high number of virulence factors and the presence of the locus agfA, coding for a thin aggregative fimbria.
These results provide evidence that Salmonella is frequently associated with gastroenteritis in water buffalo calves, particularly S. Typhimurium. Moreover, the variety in the number and distribution of different virulence markers among the collected S. Typhimurium strains suggests that within this serovar there are different pathotypes potentially responsible for different clinical syndromes.
水牛奶牛（Bubalus bubalis）犊牛的沙门氏菌病是一种广泛存在的疾病，其特征为严重的胃肠道病变、大量腹泻和严重脱水，偶尔表现为全身病程。似乎有几种沙门氏菌血清型能够感染水牛，但从该动物物种分离出的沙门氏菌分离株的特征描述较差。在本研究中，评估了致死性胃肠炎水牛犊沙门氏菌病的流行情况，并对分离的鼠伤寒沙门氏菌进行了多相特征描述。
对 248 头死于致死性胃肠炎的水牛奶牛的肠道内容物进行微生物分析，显示沙门氏菌病（25%）的流行率很高，具有不同的血清型，最常见的是鼠伤寒沙门氏菌（21%）、明斯特沙门氏菌（11%）和盖伊沙门氏菌（11%）。13 株鼠伤寒沙门氏菌均与肠炎相关，表现为肠道严重损伤，且仅偶尔与另一种可能的致胃肠炎病原体（如隐孢子虫、轮状病毒或产气荚膜梭菌）分离。其他沙门氏菌分离株主要分离自较小的肠道病变，且通常（78%的病例）与其他微生物分离，主要是产毒素大肠杆菌（35%）、隐孢子虫（20%）和轮状病毒（10%）。鼠伤寒沙门氏菌菌株通过噬菌体型和聚合酶链反应（PCR）检测 24 种毒力基因进一步进行基因型鉴定。分离株表现出 9 种不同的噬菌体型和 10 种不同的遗传谱。还发现并鉴定了 3 株单相鼠伤寒沙门氏菌（B：4，12：i：-），它们表现出 3 种不同的噬菌体型和 3 种不同的毒力型。分子特征扩展到收集的 7 株明斯特沙门氏菌和 7 株盖伊沙门氏菌，表明这些血清型中也存在不同的毒力型。在混合感染的小鼠模型中，对 3 株鼠伤寒沙门氏菌代表株进行了体内试验。最具致病性的菌株具有大量毒力因子，且存在编码薄聚集菌毛的 agfA 基因座。
这些结果表明，沙门氏菌与水牛奶牛犊的胃肠炎密切相关，特别是鼠伤寒沙门氏菌。此外，在分离的鼠伤寒沙门氏菌菌株中，不同毒力标记的数量和分布存在差异，这表明在该血清型中存在不同的致病型，可能导致不同的临床综合征。
