Pathogenic potential of environmental Vibrio cholerae strains carrying genetic variants of the toxin-coregulated pilus pathogenicity island.
The major virulence factors of toxigenic Vibrio cholerae are cholera toxin (CT), which is encoded by a lysogenic bacteriophage (CTXPhi), and toxin-coregulated pilus (TCP), an essential colonization factor which is also the receptor for CTXPhi. The genes for the biosynthesis of TCP are part of a larger genetic element known as the TCP pathogenicity island. To assess their pathogenic potential, we analyzed environmental strains of V. cholerae carrying genetic variants of the TCP pathogenicity island for colonization of infant mice, susceptibility to CTXPhi, and diarrheagenicity in adult rabbits. Analysis of 14 environmental strains, including 3 strains carrying a new allele of the tcpA gene, 9 strains carrying a new allele of the toxT gene, and 2 strains carrying conventional tcpA and toxT genes, showed that all strains colonized infant mice with various efficiencies in competition with a control El Tor biotype strain of V. cholerae O1. Five of the 14 strains were susceptible to CTXPhi, and these transductants produced CT and caused diarrhea in adult rabbits. These results suggested that the new alleles of the tcpA and toxT genes found in environmental strains of V. cholerae encode biologically active gene products. Detection of functional homologs of the TCP island genes in environmental strains may have implications for understanding the origin and evolution of virulence genes of V. cholerae.
Faruque
Shah M
SM
Molecular Genetics Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1000, Bangladesh. faruque@icddrb.org
Kamruzzaman
M
M
Meraj
Ismail M
IM
Chowdhury
Nityananda
N
Nair
G Balakrish
GB
Sack
R Bradley
RB
Colwell
Rita R
RR
Sack
David A
DA
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001435:Bacteriophages / Q000502:physiology*; D002771:Cholera / Q000382:microbiology; D002772:Cholera Toxin / Q000235:genetics / Q000378:metabolism; D003967:Diarrhea / Q000382:microbiology; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism; D005618:Fresh Water / Q000382:microbiology; D014644:Genetic Variation; D008242:Lysogeny; D051379:Mice; D011817:Rabbits; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014734:Vibrio cholerae / Q000235:genetics / Q000472:pathogenicity* / Q000821:virology*; D037521:Virulence Factors
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