Barbieri Nicolle Lima, de Oliveira Aline Luísa, Tejkowski Thiago Moreira, Pavanelo Daniel Brisotto, Rocha Débora Assumpção, Matter Letícia Beatriz, Callegari-Jacques Sidia Maria, de Brito Benito Guimarães, Horn Fabiana
Departamento de Biofísica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
PLoS One. 2013 Aug 19;8(8):e72322. doi: 10.1371/journal.pone.0072322. eCollection 2013.
We characterized 144 Escherichia coli isolates from severe cellulitis lesions in broiler chickens from South Brazil. Analysis of susceptibility to 15 antimicrobials revealed frequencies of resistance of less than 30% for most antimicrobials except tetracycline (70%) and sulphonamides (60%). The genotyping of 34 virulence-associated genes revealed that all the isolates harbored virulence factors related to adhesion, iron acquisition and serum resistance, which are characteristic of the avian pathogenic E. coli (APEC) pathotype. ColV plasmid-associated genes (cvi/cva, iroN, iss, iucD, sitD, traT, tsh) were especially frequent among the isolates (from 66.6% to 89.6%). According to the Clermont method of ECOR phylogenetic typing, isolates belonged to group D (47.2%), to group A (27.8%), to group B2 (17.4%) and to group B1 (7.6%); the group B2 isolates contained the highest number of virulence-associated genes. Clonal relationship analysis using the ARDRA method revealed a similarity level of 57% or higher among isolates, but no endemic clone. The virulence of the isolates was confirmed in vivo in one-day-old chicks. Most isolates (72.9%) killed all infected chicks within 7 days, and 65 isolates (38.1%) killed most of them within 24 hours. In order to analyze differences in virulence among the APEC isolates, we created a pathogenicity score by combining the times of death with the clinical symptoms noted. By looking for significant associations between the presence of virulence-associated genes and the pathogenicity score, we found that the presence of genes for invasins ibeA and gimB and for group II capsule KpsMTII increased virulence, while the presence of pic decreased virulence. The fact that ibeA, gimB and KpsMTII are characteristic of neonatal meningitis E. coli (NMEC) suggests that genes of NMEC in APEC increase virulence of strains.
我们对从巴西南部肉鸡严重蜂窝织炎病灶中分离出的144株大肠杆菌进行了特征分析。对15种抗菌药物的敏感性分析显示，除四环素（70%）和磺胺类药物（60%）外，大多数抗菌药物的耐药频率低于30%。对34个毒力相关基因的基因分型显示，所有分离株都携带与黏附、铁摄取和血清抗性相关的毒力因子，这些是禽致病性大肠杆菌（APEC）致病型的特征。ColV质粒相关基因（cvi/cva、iroN、iss、iucD、sitD、traT、tsh）在分离株中尤为常见（从66.6%到89.6%）。根据ECOR系统发育分型的克莱蒙方法，分离株属于D组（47.2%）、A组（27.8%）、B2组（17.4%）和B1组（7.6%）；B2组分离株包含的毒力相关基因数量最多。使用ARDRA方法进行的克隆关系分析显示，分离株之间的相似性水平为57%或更高，但没有地方流行克隆。分离株的毒力在一日龄雏鸡体内得到证实。大多数分离株（72.9%）在7天内杀死了所有感染的雏鸡，65株（38.1%）在24小时内杀死了大多数雏鸡。为了分析APEC分离株之间毒力的差异，我们通过结合死亡时间和观察到的临床症状创建了一个致病性评分。通过寻找毒力相关基因的存在与致病性评分之间的显著关联，我们发现侵袭素ibeA和gimB以及II型荚膜KpsMTII的基因的存在增加了毒力，而pic的存在则降低了毒力。ibeA、gimB和KpsMTII是新生儿脑膜炎大肠杆菌（NMEC）的特征这一事实表明，APEC中NMEC的基因增加了菌株的毒力。
