1Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India.
2Collaborative Research Center of Okayama University for Infectious Diseases in India, Kolkata 700010, India.
J Med Microbiol. 2018 Sep;67(9):1326-1333. doi: 10.1099/jmm.0.000783. Epub 2018 Jun 21.
Two natural epidemic biotypes of Vibrio cholerae O1, classical and El Tor, exhibit different patterns of sensitivity against the antimicrobial peptide polymyxin B. This difference in sensitivity has been one of the major markers in biotype classification system for several decades. A recent report regarding the emergence of polymyxin B-sensitive El Tor V. cholerae O1 in Kolkata has motivated us to track the spread of the strains containing this important trait, along with Haitian-like genetic content, in different parts of India.
We have collected 260 clinical V. cholerae O1 strains from 12 states in India and screened them for polymyxin B susceptibility. Genetic characterization was also performed to study the tcpA, ctxB and rtxA genotypes by allele-specific polymerase chain reaction (PCR) and nucleotide sequencing.
Interestingly, 88.85 % of the isolates were found to be sensitive to polymyxin B. All of the states, with the exception of Assam, had polymyxin B-sensitive V. cholerae strains and complete replacement with this strain was found in eight of the states. However, from 2016 onwards, all the strains tested showed sensitivity to polymyxin B. Allele-specific PCR and sequencing confirmed that all strains possessed Haitian-like genetic traits.
Polymyxin B-sensitive strains have begun to spread throughout India and may lead to the revision of the biotype classification. The dissemination of these new variant strains needs to be carefully monitored in different endemic populations through active holistic surveillance to understand their clinical and epidemiological consequences.
霍乱弧菌 O1 的两个天然流行生物型，古典生物型和埃尔托生物型，对抗菌肽多黏菌素 B 的敏感性表现出不同的模式。这种敏感性差异是几十年来生物型分类系统的主要标志之一。最近有报道称，在加尔各答出现了对多黏菌素 B 敏感的埃尔托生物型霍乱弧菌 O1，这促使我们追踪含有这种重要特征（以及海地样遗传物质）的菌株在印度不同地区的传播情况。
我们从印度 12 个邦收集了 260 株临床分离的霍乱弧菌 O1 菌株，并对其多黏菌素 B 敏感性进行了筛选。还进行了遗传特征分析，通过等位基因特异性聚合酶链反应（PCR）和核苷酸测序研究了 tcpA、ctxB 和 rtxA 基因型。
有趣的是，88.85%的分离株对多黏菌素 B 敏感。除了阿萨姆邦之外，所有的邦都有对多黏菌素 B 敏感的霍乱弧菌菌株，并且在 8 个邦中发现了这种菌株的完全替代。然而，从 2016 年开始，所有测试的菌株都对多黏菌素 B 敏感。等位基因特异性 PCR 和测序证实，所有菌株都具有海地样遗传特征。
多黏菌素 B 敏感菌株已开始在印度各地传播，可能导致生物型分类的修订。需要通过主动全面监测不同流行人群中的这些新变体菌株，了解其临床和流行病学后果，以仔细监测它们的传播情况。
