Division of Bacteriology, National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme XM, Beliaghata, Kolkata 700 010, India.
Int J Antimicrob Agents. 2010 Oct;36(4):348-51. doi: 10.1016/j.ijantimicag.2010.06.037. Epub 2010 Aug 3.
Shigellosis is a major cause of diarrhoea-related morbidity and mortality, especially in children in developing countries such as India. Recently, it was estimated that 91 million individuals worldwide contract shigellosis each year. The emergence and dissemination of multidrug-resistant strains of Shigella is now an emerging global health problem. During the past two decades, much attention was given to re-evaluation of treatment recommendations. In the present study, we investigated a clinical strain of Shigella flexneri 3a with multiple drug resistance. This strain was resistant to ampicillin, chloramphenicol, co-trimoxazole (trimethoprim/sulfamethoxazole), nalidixic acid, streptomycin, sulfamethoxazole, tetracycline and trimethoprim. However, it was susceptible to 46.7% of drugs tested, i.e. azithromycin, ceftriaxone, ciprofloxacin, gentamicin, kanamycin, norfloxacin and ofloxacin. A 6.3-kb plasmid was cured from this strain using acridine orange. Following curing, it was observed that 87% of drug resistance loci of S. flexneri 3a are chromosomal and 13% are plasmid-encoded. This 6.3-kb plasmid was involved in streptomycin and sulfamethoxazole resistance in S. flexneri 3a strain, which was confirmed by the disk diffusion method. Clonality was confirmed by pulse-field gel electrophoresis (PFGE). This study contributes to our knowledge on acquired drug resistance in one of the most common Shigella spp., S. flexneri 3a, which will enable better understanding of effective clinical management of shigellosis.
志贺菌病是发展中国家（如印度）腹泻相关发病率和死亡率的主要原因，尤其是在儿童中。最近估计，全世界每年有 9100 万人感染志贺菌病。志贺菌多重耐药株的出现和传播现在是一个新出现的全球卫生问题。在过去的二十年中，人们非常关注重新评估治疗建议。在本研究中，我们调查了一株具有多重耐药性的福氏志贺菌 3a 临床分离株。该菌株对氨苄西林、氯霉素、复方磺胺甲噁唑（甲氧苄啶/磺胺甲噁唑）、萘啶酸、链霉素、磺胺甲噁唑、四环素和甲氧苄啶耐药。然而，它对 46.7%的测试药物敏感，即阿奇霉素、头孢曲松、环丙沙星、庆大霉素、卡那霉素、诺氟沙星和氧氟沙星。用吖啶橙从该菌株中消除了 6.3kb 的质粒。消除后，观察到福氏志贺菌 3a 的 87%耐药基因位于染色体上，13%位于质粒上。该 6.3kb 的质粒参与了福氏志贺菌 3a 菌株对链霉素和磺胺甲噁唑的耐药性，这通过圆盘扩散法得到了证实。脉冲场凝胶电泳（PFGE）证实了克隆性。这项研究有助于我们了解最常见的志贺菌之一，福氏志贺菌 3a 的获得性耐药性，这将使我们更好地了解志贺菌病的有效临床管理。
