Vibrio cholerae RND Family Efflux Systems Are Required for Antimicrobial Resistance, Optimal Virulence Factor Production, and Colonization of the Infant Mouse Small Intestine

• Published in: Infection and Immunity 2008-08, Vol.76 (8), p.3595-3605
• Main Authors: Bina, Xiaowen R, Provenzano, Daniele, Nguyen, Nathalie, Bina, James E
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Anti-Bacterial Agents - pharmacology; Bacterial Infections; Bacterial Proteins - biosynthesis; Bacteriology; Biological and medical sciences; Cholera - microbiology; Cholera Toxin - metabolism; Drug Resistance, Multiple, Bacterial; Fimbriae, Bacterial - metabolism; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene Expression Profiling; Gene Order; Genetic Complementation Test; Intestine, Small - microbiology; Membrane Transport Proteins - genetics; Membrane Transport Proteins - physiology; Mice; Microbiology; Miscellaneous; Sequence Homology, Amino Acid; Transcription Factors - biosynthesis; Vibrio cholerae; Vibrio cholerae O1 - drug effects; Vibrio cholerae O1 - metabolism; Vibrio cholerae O1 - pathogenicity; Vibrio cholerae O1 - physiology; Virulence Factors - metabolism
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.01620-07

Vibrio cholerae is a gram-negative human intestinal pathogen that causes the diarrheal disease cholera. Humans acquire cholera by ingesting V. cholerae-contaminated food or water. Upon ingestion, V. cholerae encounters several barriers to colonization, including bile acid toxicity and antimicrobial products of the innate immune system. In many gram-negative bacteria, resistance to the antimicrobial effects of these products is mediated by RND (resistance-nodulation-division) family efflux systems. In this study we tested the hypothesis that the V. cholerae RND efflux systems are required for antimicrobial resistance and virulence. The six V. cholerae genes encoding RND efflux pumps were deleted from the genome of the O1 El Tor strain N16961, resulting in the generation of 14 independent RND deletion mutants, including one RND-null strain. Determination of the antimicrobial susceptibilities of the mutants revealed that the RND efflux systems were responsible for resistance to multiple antimicrobial compounds, including bile acids, antimicrobial peptides, and antibiotics. VexB (VC0164) was found to be the RND efflux pump primarily responsible for the resistance of V. cholerae to multiple antimicrobial compounds in vitro. In contrast, VexD (VC1757) and VexK (VC1673) encoded efflux pumps with detergent-specific substrate specificities that were redundant with VexB. A strain lacking VexB, VexD, and VexK was attenuated in the infant mouse model, and its virulence factor production was unaffected. In contrast, a V. cholerae RND-null strain produced significantly less cholera toxin and fewer toxin-coregulated pili than the wild type and was unable to colonize the infant mouse. The decreased virulence factor production in the RND-null strain was linked to reduced transcription of tcpP and toxT. Our findings show that the V. cholerae RND efflux systems are required for antimicrobial resistance, optimal virulence factor production, and colonization of the infant mouse.