title: Characterization of Vibrio cholerae O1 El Tor biotype variant clinical isolates from Bangladesh and Haiti, including a molecular genetic analysis of virulence genes.
abstract: Vibrio cholerae serogroup O1, the causative agent of the diarrheal disease cholera, is divided into two biotypes: classical and El Tor. Both biotypes produce the major virulence factors toxin-coregulated pilus (TCP) and cholera toxin (CT). Although possessing genotypic and phenotypic differences, El Tor biotype strains displaying classical biotype traits have been reported and subsequently were dubbed El Tor variants. Of particular interest are reports of El Tor variants that produce various levels of CT, including levels typical of classical biotype strains. Here, we report the characterization of 10 clinical isolates from the International Centre for Diarrhoeal Disease Research, Bangladesh, and a representative strain from the 2010 Haiti cholera outbreak. We observed that all 11 strains produced increased CT (2- to 10-fold) compared to that of wild-type El Tor strains under in vitro inducing conditions, but they possessed various TcpA and ToxT expression profiles. Particularly, El Tor variant MQ1795, which produced the highest level of CT and very high levels of TcpA and ToxT, demonstrated hypervirulence compared to the virulence of El Tor wild-type strains in the infant mouse cholera model. Additional genotypic and phenotypic tests were conducted to characterize the variants, including an assessment of biotype-distinguishing characteristics. Notably, the sequencing of ctxB in some El Tor variants revealed two copies of classical ctxB, one per chromosome, contrary to previous reports that located ctxAB only on the large chromosome of El Tor biotype strains.
authors: Department of Microbiology and Immunology, Dartmouth Medical School, Vail Building HB7550, Hanover, NH 03755, USA.
authors: Mike S
authors: MS
authors: Son
authors: Christina J
authors: CJ
authors: Megli
authors: Gabriela
authors: G
authors: Kovacikova
authors: Firdausi
authors: F
authors: Qadri
authors: Ronald K
authors: RK
authors: Taylor
mesh_terms: D000293:Adolescent; D000328:Adult; D000369:Aged, 80 and over; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001459:Bangladesh; D002648:Child; D002675:Child, Preschool; D002771:Cholera / Q000382:microbiology* / Q000473:pathology; D002772:Cholera Toxin / Q000096:biosynthesis / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics; D014644:Genetic Variation; D006205:Haiti; D006801:Humans; D008297:Male; D014157:Transcription Factors / Q000235:genetics; D041241:Vibrio cholerae O1 / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity*; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics*; D055815:Young Adult
chemical_list: D001426:Bacterial Proteins; C085807:TcpA protein, Vibrio cholerae; D014157:Transcription Factors; D037521:Virulence Factors; D036781:Fimbriae Proteins; C075626:tcpN protein, Vibrio cholerae; D002772:Cholera Toxin