Genetic Characterization of Cryptosporidium spp. in Diarrhoeic Children from Four Provinces in South Africa

The diversity of Cryptosporidium at species, subtype family and subtype level in diarrhoeic children was investigated in four provinces in South Africa. A total of 442 stool samples from children <5 years of age were collected under a large rotavirus surveillance programme and analysed by Ziehl–Neelsen acid‐fast staining. Fifty‐four (12.2%) were positive for Cryptosporidium, of which 25 were genotyped by polymerase chain reaction (PCR)–restriction fragment length polymorphism (RFLP) and DNA sequence analyses of the 18S rRNA gene. The majority of genotyped specimens were identified as C. hominis (76%), and a high genetic diversity was found with five different C. hominis subtype families (Ia, Ib, Id, Ie and If). Cryptosporidium parvum was found in 20% of the isolates, and three subtype families were identified (IIc, IIe and IIb), with subtype family IIc being the most common. One specimen was identified as C. meleagridis of the subtype family IIId. These results are in accordance with findings from other developing countries and report for the first time the presence in South Africa of C. meleagridis, various subtypes of C. parvum and the subtype family Ie of C. hominis. The results suggest that C. hominis and anthroponotic C. parvum subtypes are the major cause of cryptosporidiosis in South Africa. Further molecular studies are needed to better understand the epidemiology and public health importance of Cryptosporidium in humans in South Africa.     

广州市罗非鱼源无乳链球菌 分离鉴定与致病性研究

从广州增城中新镇发病罗非鱼体内分离到4 株致病菌株,经细菌形态学观察、生化试验鉴定、特异基因cfb 扩增及序列分析,初步鉴定为罗非鱼无乳链球菌。4 株无乳链球菌均对头孢哌酮、庆大霉素、先锋霉素吁、先锋霉素遇、阿奇霉素、克林霉素、头孢孟多等敏感。选用其中的ZX1 分离株分别对罗非鱼、小鼠、乳鼠进行人工感染,结果显示,用活菌数为109个/mL 的菌液腹腔注射罗非鱼,可使受感染鱼100%死亡;用活菌数为108个/mL 的菌液腹腔注射小鼠和皮下注射乳鼠,在72 h内的死亡率为分别为66.7%和100%;表明分离株ZX1 对罗非鱼和小鼠具有较强的致病性。经多重PCR 检测分离株分子血清分型,结果显示分离株均为玉a 型。     

单核增生李斯特菌ERIC-PCR分子分型方法的建立

以单核增生李斯特菌10403s基因组为模板,运用L16(54)正交试验,对影响ERIC-PCR的多个因素,包括Mg2+、dNTP、引物、模板和rTaq酶浓度等进行优化,并应用于不同来源的单核增生李斯菌株的ERIC-PCR,其扩增图谱表现出明显的多态性。结果表明:建立的ERIC-PCR反应体系和程序适合于单核增生李斯特菌进行分子分型。     

Molecular characterization of Cryptosporidium parvum detected in Japanese black and Holstein calves in Iwate Prefecture and Tanegashima Island,Kagoshima Prefecture,Japan

Cryptosporidium oocysts were found in 43 out of 77 calves from two farms in Iwate Prefecture and nine farms on Tanegashima Island, Kagoshima Prefecture, Japan. The DNA fragments of 18S ribosomal RNA (18S rRNA) gene were amplified by a nested PCR from 43 oocyst-positive as well as one oocyst-negative samples. All of them were precisely identified as C. parvum by analyzing the nucleotide sequences of the 18S rRNA gene. C. parvum oocyst-positive calves ranged in age from 6 to 13 days old and significantly have watery diarrhea (P<0.05). Sequences of the gene encoding the 60-kDa glycoprotein (GP60) in 43 Cryptosporidium oocyst-positive samples were identical to that of the zoonotic IIaA15G2R1 subtype. We therefore suggest that calves could be potential sources of C. parvum infections in humans.     

单核细胞增生症李斯特菌的分子亚分型法及其应用

细菌亚分型方法的建立不仅能检测人群李斯特菌病的暴发流行 ,还能追踪食物链中单核细胞增生症李斯特菌 (L M)的污染情况。亚分型法对更好的了解 LM的群体遗传学、流行病学及生态学有重要意义。过去的 5年内 ,在建立对 LM敏感、快速、自动化、简便易用的分子亚分型方面起得了重大的进展。文章对 L M不同的亚分型方法及其应用作了概述     

Molecular and Statistical Analysis of Campylobacter spp. and Antimicrobial‐Resistant Campylobacter Carriage in Wildlife and Livestock from Ontario Farms

The objectives of this study were to (i) compare the carriage of Campylobacter and antimicrobial‐resistant Campylobacter among livestock and mammalian wildlife on Ontario farms, and (ii) investigate the potential sharing of Campylobacter subtypes between livestock and wildlife. Using data collected from a cross‐sectional study of 25 farms in 2010, we assessed associations, using mixed logistic regression models, between Campylobacter and antimicrobial‐resistant Campylobacter carriage and the following explanatory variables: animal species (beef, dairy, swine, raccoon, other), farm type (swine, beef, dairy), type of sample (livestock or wildlife) and Campylobacter species (jejuni, coli, other). Models included a random effect to account for clustering by farm where samples were collected. Samples were subtyped using a Campylobacter‐specific 40 gene comparative fingerprinting assay. A total of 92 livestock and 107 wildlife faecal samples were collected, and 72% and 27% tested positive for Campylobacter, respectively. Pooled faecal samples from livestock were significantly more likely to test positive for Campylobacter than wildlife samples. Relative to dairy cattle, pig samples were at significantly increased odds of testing positive for Campylobacter. The odds of isolating Campylobacter jejuni from beef cattle samples were significantly greater compared to dairy cattle and raccoon samples. Fifty unique subtypes of Campylobacter were identified, and only one subtype was found in both wildlife and livestock samples. Livestock Campylobacter isolates were significantly more likely to exhibit antimicrobial resistance (AMR) compared to wildlife Campylobacter isolates. Campylobacter jejuni was more likely to exhibit AMR when compared to C. coli. However, C. jejuni isolates were only resistant to tetracycline, and C.  coli isolates exhibited multidrug resistance patterns. Based on differences in prevalence of Campylobacter spp. and resistant Campylobacter between livestock and wildlife samples, and the lack of similarity in molecular subtypes and AMR patterns, we concluded that the sharing of Campylobacter species between livestock and mammalian wildlife was uncommon.