Devitalization of salmonellae in fish meals with propionic acid

Animal protein feeds are regarded as a potential source of salmonellae for the animal and human population. Decontamination is carried out by various methods. At the present time, propionic acid is recommended for this purpose but different levels of concentration have been given by various authors. In our experiments broth cultures of the following serotypes were used for artifical contamination: Salmonella typhimurium, S. taksony and S. senftenberg. The infected fish meal always contained 200,000 salmonellae in 1 g. The addition of 3% propionic acid resulted in an immediate devitalization of salmonellae. The addition of 2% propionic acid caused devitalization within 49 days. Salmonella senftenberg was found to be the most resistant of the three serotypes tested. The active substance must be perfectly homogenized. The addition of 0.3% propionic acid has proved effective in broth.     

Salmonellae and Campylobacters in Household and Stray Dogs in Northern Taiwan

Rectal swabs were collected from 437 household and 491 stray dogs in northern Taiwan from May 2003 to June 2005 to investigate the prevalence and antimicrobial susceptibilities of salmonellae and campylobacters. The results revealed that 2.1% of household dogs and 6.3% of stray dogs were positive for salmonellae, with Salmonella Duesseldorf being the most dominant serotype in both. Additionally, 2.7% of the household dogs and 23.8% of the stray dogs were positive for campylobacters. Campylobacter jejuni was the most prevalent species (86.8%), followed by C. upsaliensis (9.3%) and C. coli (3.9%). Both salmonella and campylobacter isolation rates from the stray dogs were significantly higher than those from the household dogs (p < 0.01). The susceptibility of 33 C. jejuni isolates to eight antimicrobials was studied by the E-test. A high rate of resistance was observed to azithromycin (93.9%), clindamycin (87.9%), erythromycin (81.8%), tetracycline (78.8%), chloramphenicol (69.7%), nalidixic acid (51.5%), gentamicin (33.3%), and ciprofloxacin (18.2%). The susceptibility of 40 Salmonella isolates to 15 antimicrobials was also studied by the disc-diffusion method. All the Salmonella isolates were susceptible to ciprofloxacin and ceftriaxone. Resistance was observed most frequently to tetracycline (77.5%), chloramphenicol (52.5%), and ampicillin (50%).     

Comparative studies on enrichment and selective media for isolation of Salmonellae from faecal specimens.

Enrichment media (tetrathionate, selenite and Rapp ap ort broths) and selective media (desoxycholate citrate agar and brilliant green agar) were tested in different combinations to ascertain their capacity for isolation of salmonella bacteria. The material consisted of 299 samples of cattle faeces from two herds infected with salmonella (Table 1), and of 111 artificially contaminated samples of pig faeces (Table 3). The tetrathionate and selenite broths were equally useful for the material as a whole, whereas the results varied between different species of salmonella which is of great practical interest. The number of salmonella isolations was much lower when enrichment with Rappaport broth was used. The rate of salmonella isolations can often be increased by parallel enrichments with two different media. Of the selective agar media tested, brilliant green agar was superior to desoxycholate citrate agar.     

动物性饲料中沙门氏菌快速检验的研究——协同凝集试验及HRP-SPA酶染色法的应用

本研究确定了适用于动物性饲料中沙门氏菌检验的增菌程序、协同凝集试验(COAG)及HRP—SPA染色法(酶染法)的最适实验条件。以这种条件进行增菌,并以COAG及酶染法进行检查,具有快度、敏感、特异性强的优点。应用COAG、酶染法及沙门氏菌常规分离鉴定法,对236份动物性饲料标本进行了检测。结果两种快速法与常规法有较好的符合率,酶染法在检出阳性标本上优于常规法.且可在16～18h内报告结果,比常规法的时间明显缩短。因此认为,COAG和酶染法适用于动物性饲料中沙门氏菌的快速检测。动物性饲料的沙门氏菌污染,依饲料的种类不同而异,其中鱼粉为31.5％、血粉25％骨粉10.3％,平均为17.4％,而且存在着多种血清型的沙门氏菌,其中以鼠伤寒沙门氏菌占优势。因此认为动物性饲料中的沙门氏菌污染在人畜沙门氏菌的流行病学上具有重要的作用。