Phenotypic and genotypic changes in Vibrio cholerae O139 Bengal

Abstract

To find reasons for the recent decline of Vibrio cholerae O139 Bengal cholera in Bangladesh, phenotypic and genotypic changes in O139 isolates obtained from patients with cholera from 1993 to 1996 were studied. The isolates were tested for the presence of ctx and tcpA genes, hemagglutinin/protease (HA/P), capsule, D-mannosesensitive hemagglutinin (MSHA), L-fucose-sensitive hemagglutinin (FSHA), tube test (tube) and CAMP test (CAMP) hemolytic activities, resistance to 2,4-diamino-6,7-diisopropyl pteridine (O/129) and trimethoprimsulfamethoxazole (TMP-SMX), and genotype by pulsed-field gel electrophoresis (PFGE). All isolates possessed ctx and tcpA genes, HA/P, and a capsule. Most isolates were negative for FSHA, but although the majority of the isolates were positive for MSHA, no discernible trend in the activity was found during the study period. All early isolates were CAMP hemolysin positive and resistant to the vibriostatic compound O/129 and TMP-SMX, the two properties that could be used for the presumptive diagnosis of O139 cholera. However, subsequently, isolates that were CAMP hemolysin negative and susceptible to TMP-SMX and O/129 were increasingly encountered, with all the 1996 isolates being so, which suggested that these properties can no longer be used for the presumptive diagnosis of O139 cholera. V. cholerae O139 isolates that were CAMP hemolysin positive and resistant to O/129 and TMP-SMX produced a disease of greater severity than that caused by the CAMP hemolysin-negative and susceptible isolates on the basis of the lengths of stay of the hospitalized patients. The study period witnessed the evolution of four different genotypes by PFGE. All of these data suggested that the V. cholerae O139 isolates have undergone changes in some properties. However, how these changes influenced their prevalence relative to that of V. cholerae O1 in human infection is not clear. Studies of the environmental factors will provide the key for an understanding of the relative abundance of these vibrios.

Molecular Characterization of a New Ribotype of Vibrio cholerae O139 Bengal Associated with an Outbreak of Cholera in Bangladesh

“…Interplay of a variety of factors in the aquatic environment and genetic and phenotypic changes in V. cholerae, as well as the immune status of the human host, may contribute to the existence and dominance of different clones of toxigenic V. cholerae. We have previously reported different phenotypic and genetic changes in V. cholerae O139 in Bangladesh and the prevalence of different clones (1,8). Although in the present study we did not detect any change in the major pathogenic genes carried by the strains belonging to the new ribotype, we did not rule out the possibility of simultaneous genetic changes occurring in the rRNA operons and other unidentified genes that might influence the prevalence of the O139 strains by interacting with environmental factors.…”

Isolation, characterization, and antibiotic resistance of Vibrio spp. in sea turtles from Northwestern Mexico

“…PCR assays were performed in a 25 μL volume consisting of 1X GoTaq green master mix (Promega), primers targeting the tl gene, the pR72H plasmid and the tdh and trh genes, the toxRS and orf8 pandemic marker genes for Vibrio parahaemolyticus as previously described (Velazquez-Roman et al, 2012 ; Hernández-Díaz et al, 2015 ). Vibrio cholerae O1 and O139 were further confirmed for the presence of VC, rfbO1, O139 , genes, and the ctxA, ctxB, zot , and ace toxigenic genes (Albert et al, 1997 ; Sarkar et al, 2002 ; Di Pinto et al, 2005 ; Goel et al, 2007 ) and 0.5 μg of purified genomic DNA template, with the remaining volume consisting of molecular biology grade water. PCR was routinely conducted in a Thermal Cycler C1000 (Bio-Rad Laboratories, Hercules, California).…”

Antibiotic resistance and genetic diversity of Shigella sonnei isolated from patients with diarrhoea between 1999 and 2003 in Bangladesh

“…PFGE. Intact, agarose-embedded chromosomal DNA from clinical isolates of Shigella sonnei was prepared and PFGE was performed using a contour-clamped homogeneous electric field (CHEF-DRII) apparatus (Bio-Rad), according to procedures described previously (Albert et al, 1997;Okada et al, 1991;Talukder et al, 1999Talukder et al, , 2003a and by Brian et al (1993), but with different pulse times, 1-10 s for 10 h, 3-28 s for 10 h, 3-35 s for 5 h and 5-70 s for 15 h. Genomic DNA was digested with XbaI (Gibco-BRL). The restriction fragments were separated by using a CHEF-DRII system apparatus in 1 % pulsed-field certified agarose in 0?56 TBE buffer.…”