Keane Orla M
Animal & Bioscience Research Department, Teagasc, Grange, Dunsany, Co. Meath, Ireland.
Res Microbiol. 2016 Oct;167(8):678-684. doi: 10.1016/j.resmic.2016.06.011. Epub 2016 Jul 9.
Escherichia coli is a common cause of bovine mastitis, particularly around parturition and early lactation when the host is immunosuppressed. Isolates (n = 37) recovered from cases of clinical mastitis in Ireland were characterised with respect to genotypic diversity, phylogenetic group, virulence gene profile and antimicrobial susceptibility. The isolates were genotypically diverse, belonging to 19 different sequence types. However, the majority (86%) belonged to phylogenetic groups A or B1, groups commonly associated with commensal E. coli. The isolates encoded few virulence genes with iss (increased serum survival, 41%), lpfA (long polar fimbriae, 19%) and astA (enteroaggregative heat-stable toxin, 14%) among the most common virulence genes detected. The only virulence gene to differ in frequency between the phylogenetic groups was lpfA, found exclusively in B1. Resistance to at least one antimicrobial was detected in 16% of isolates. Three isolates were multidrug-resistant, with one resistant to seven antibiotics. There was no relationship between antimicrobial resistance and phylogenetic group. These results indicate that many cases of clinical E. coli mastitis in Ireland may be caused by opportunistic commensal organisms lacking specific virulence genes. However, the organisms represent a reservoir of antimicrobial resistance determinants with the potential to disseminate determinants to other organisms.
大肠杆菌是牛乳腺炎的常见病因，尤其是在宿主免疫抑制的围产期和泌乳早期。从爱尔兰临床乳腺炎病例中分离出37株菌株，对其进行了基因型多样性、系统发育群、毒力基因谱和抗菌药物敏感性分析。这些分离株基因型多样，属于19种不同的序列类型。然而，大多数（86%）属于系统发育群A或B1，这两个群通常与共生大肠杆菌有关。分离株编码的毒力基因较少，iss（血清存活率增加，41%）、lpfA（长极毛，19%）和astA（肠聚集性耐热毒素，14%）是检测到的最常见的毒力基因。在系统发育群之间，唯一频率不同的毒力基因是lpfA，仅在B1群中发现。16%的分离株检测到对至少一种抗菌药物耐药。3株分离株为多重耐药，其中1株对7种抗生素耐药。抗菌药物耐药性与系统发育群之间没有关系。这些结果表明，爱尔兰许多临床大肠杆菌乳腺炎病例可能由缺乏特定毒力基因的机会性共生生物引起。然而，这些生物是抗菌药物耐药性决定因素的储存库，有可能将这些决定因素传播给其他生物。
