AUTHOR=Sarkar Anirban , Morita Daichi , Ghosh Amit , Chowdhury Goutam , Mukhopadhyay Asish K. , Okamoto Keinosuke , Ramamurthy Thandavarayan 

TITLE=Altered Integrative and Conjugative Elements (ICEs) in Recent Vibrio cholerae O1 Isolated From Cholera Cases, Kolkata, India

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02072

DOI=10.3389/fmicb.2019.02072

ISSN=1664-302X

ABSTRACT=<p>The self-transferring integrative and conjugative elements (ICEs) are large genomic segments carrying several bacterial adaptive functions including antimicrobial resistance (AMR). SXT/R391 family is one of the ICEs extensively studied in cholera-causing pathogen <italic>Vibrio cholerae</italic>. The genetic characteristics of ICE-SXT/R391 in <italic>V. cholerae</italic> are dynamic and region-specific. These ICEs in <italic>V. cholerae</italic> are strongly correlated with resistance to several antibiotics such as tetracycline, streptomycin and trimethoprim-sulfamethoxazole. We screened <italic>V. cholerae</italic> O1 strains isolated from cholera patients in Kolkata, India from 2008 to 2015 for antibiotic susceptibility and the presence of ICEs, and subsequently sequenced their conserved genes. Resistance to tetracycline, streptomycin and trimethoprim-sulfamethoxazole was detected in strains isolated during 2008–2010 and 2014–2015. The genes encoding resistance to tetracycline (<italic>tetA</italic>), trimethoprim-sulfamethoxazole (<italic>dfrA1</italic> and <italic>sul2</italic>), streptomycin (<italic>strAB</italic>), and chloramphenicol (<italic>floR</italic>) were detected in the ICEs of these strains. There was a decrease in overall drug resistance in <italic>V. cholerae</italic> associated with the ICEs in 2011. DNA sequence analysis also showed that AMR in these strains was conferred mainly by two types of ICEs, i.e., ICE<sup>TET</sup> (comprising <italic>tetA, strAB, sul2</italic>, and <italic>dfrA1</italic>) and ICE<sup>GEN</sup> (<italic>floR, strAB, sul2</italic>, and <italic>dfrA1</italic>). Based on the genetic structure, Kolkata strains of <italic>V. cholerae</italic> O1 had distinct genetic traits different from the ICEs reported in other cholera endemic regions. Transfer of AMR was confirmed by conjugation with sodium azide resistant <italic>Escherichia coli</italic> J53. In addition to the acquired resistance to streptomycin and trimethoprim-sulfamethoxazole, the conjugally transferred (CT) <italic>E. coli</italic> J53 with ICE showed higher resistance to chloramphenicol and tetracycline than the donor <italic>V. cholerae.</italic> Pulsed-field gel electrophoresis (PFGE) based clonal analysis revealed that the <italic>V. cholerae</italic> strains could be grouped based on their ICEs and AMR patterns. Our findings demonstrate the epidemiological importance of ICEs and their role in the emergence of multidrug resistance (MDR) in El Tor vibrios.</p>