The V. cholerae strain MCV09 characterized in the present investigation was isolated from a patient who died due to severe dehydration in the Medical College Hospital, Trivandrum, India. The strain was maintained as peptone agar stab cultures at room temperature and stocked in tryptic soy broth with 30% glycerol at −70 °C till further use. Initial biochemical screening was performed to identify the strain, followed by serological analysis (Polyclonal O1, monospecific Ogawa

and Inaba antisera supplied by the World Health Organization (WHO), Regional Office of South East Asia, New Delhi, India). The strains of V. cholerae, 569B (O1 classical Inaba) and VC20 (O1 El Tor Ogawa) were used as controls for agglutination. The V. cholerae O1 El Tor Ogawa strain,

Selleckchem Erastin TV107, served as a control for detection of int and drug resistance genes. The V. cholerae O139 strain, MO10, was used as a control for amplification of attP attachment sites. The O1 El Tor Ogawa strain, MCV08 (Trivandrum, India), and environmental Toxigenic O1 El Tor Ogawa strain, A880 (Alappuzha, India), were also used for amplification of attP sites. The rifampicin-resistant Escherichia Bleomycin coli strain (DH5α) was used as a recipient for the conjugation experiment. The test strain was examined for resistance to 15 major antibiotics using commercial discs (Himedia, Bombay, India) according to the interpretation criteria recommended by the WHO (1993). Escherichia coli ATCC 25922 was used for quality control for the antibiotic resistance assay. The MIC value for ciprofloxacin, nalidixic acid, tetracycline and trimethoprim was determined using the E-test (AB-BIODISK). The conjugation experiment was carried

out on Luria–Bertani (LB) agar plates as described previously (Waldor et al., 1996). For all PCR assays except detection of attP sites, cell lysates were used as template DNA. Histone demethylase For the amplification of attP sites, a single bacterial colony was picked from an LB agar plate and directly added to the PCR mixture. The lists of primers used and their sources are given in Table 1. The presence of int was detected using the method of Ahmed et al. (2005). The PCR cycle for the attP site consisted of an initial denaturation at 94 °C for 4 min, followed by 30 cycles of denaturation for 30 s at 94 °C, primer annealing for 30 s at 50 °C, extension for 45 s at 72 °C and a final extension at 72 °C for 10 min. The associated drug resistance genes viz dfrA1, strB and sul2 were examined by specific PCR (Falbo et al., 1999; Hochhut et al., 2001; Ramachandran et al., 2007). The amplification of the QRDR of gyrA, gyrB, parC and parE was performed as described by Baranwal et al. (2002). The amplified products were separated on a 1% agarose gel, stained with ethidium bromide and visualized using a Fluor-S-MultiImager (Bio-Rad).