Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India.
University of Virginia, School of Medicine, Charlottesville, VA, USA.
J Med Microbiol. 2014 Jul;63(Pt 7):903-910. doi: 10.1099/jmm.0.070912-0. Epub 2014 May 1.
Phenotypic and genetic characteristics of Shigella spp. isolated from diarrhoeal and asymptomatic children aged up to 5 years were analysed in this study. In total, 91 and 17 isolates were identified from diarrhoeal (case) and asymptomatic (control) children, respectively. All the isolates were tested for antimicrobial resistance, the presence of integrons, plasmid-mediated quinolone resistance (PMQR), virulence-associated genes and Shigella pathogenicity island (SH-PAI). The majority of the Shigella spp. from cases (68.1%) and controls (82.3%) were found to be resistant to fluoroquinolones. Integron carriage was detected more in cases (76.9%) than in controls (35.5%). Atypical class 1 integron was detected exclusively in Shigella flexneri from cases but not from the controls. PMQR genes such as aac(6')-Ib-cr and qnrS1 were detected in 82.4 and 14.3% of the isolates from cases and in 53 and 17.6% in controls, respectively. Shigella isolates from cases as well as from controls were positive for the invasive plasmid antigen H-encoding gene ipaH. The other virulence genes such as virF, sat, setA, setB, sen and ial were detected in Shigella isolates in 80.2, 49.4, 27.4, 27.4, 80.2 and 79.1% of cases and in 64.7, 52.9, 17.6, 17.6, 64.7 and 64.7% of controls, respectively. The entire SH-PAI was detected in S. flexneri serotype 2a from cases and controls. In an isolate from a control child, the SH-PAI was truncated. Integrons, PMQR and virulence-encoding genes were detected more frequently in cases than in controls. In diarrhoea endemic areas, asymptomatic carriers may play a crucial role in the transmission of multidrug-resistant Shigella spp. with all the putative virulence genes.
本研究分析了从 5 岁以下腹泻和无症状儿童中分离的志贺氏菌属的表型和遗传特征。共从腹泻（病例）和无症状（对照）儿童中鉴定出 91 和 17 株分离株。所有分离株均进行了抗菌药物耐药性、整合子、质粒介导喹诺酮耐药（PMQR）、毒力相关基因和志贺氏菌致病性岛（SH-PAI）检测。大多数来自病例的志贺氏菌属（68.1%）和对照（82.3%）对氟喹诺酮类药物耐药。病例中整合子携带率（76.9%）高于对照（35.5%）。仅在病例中的福氏志贺菌中检测到非典型 1 类整合子，但在对照中未检测到。在病例组中，aac(6')-Ib-cr 和 qnrS1 等 PMQR 基因的检出率为 82.4%和 14.3%，而在对照组中分别为 53%和 17.6%。病例和对照的志贺氏菌分离株均为侵袭性质粒抗原 H 编码基因 ipaH 阳性。其他毒力基因，如 virF、sat、setA、setB、sen 和 ial，在病例组的志贺氏菌分离株中检出率为 80.2%、49.4%、27.4%、27.4%、80.2%和 79.1%，在对照组中为 64.7%、52.9%、17.6%、17.6%、64.7%和 64.7%。病例和对照的所有 SH-PAI 均在福氏志贺菌 2a 血清型中检测到。在对照儿童的一个分离株中，SH-PAI 发生了截断。病例中整合子、PMQR 和毒力编码基因的检出率高于对照。在腹泻流行地区，无症状携带者可能在传播具有所有潜在毒力基因的多药耐药志贺氏菌属方面发挥关键作用。
