S. P. Borriello, Pathogenesis of Clostridium difficile infection, J Antimicrob Chemother, vol.41, pp.13-19, 1998.

M. Warny, J. Pepin, A. Fang, G. Killgore, and A. Thompson, Toxin production by an emerging strain of Clostridium difficile associated with outbreaks of severe disease in North America and Europe, Lancet, vol.366, pp.1079-1084, 2005.

L. C. Mcdonald, G. E. Killgore, A. Thompson, R. C. Owens, and S. V. Kazakova, An epidemic, toxin gene-variant strain of Clostridium difficile, N Engl J Med, vol.353, pp.2433-2441, 2005.

R. A. Stabler, M. He, L. Dawson, M. Martin, and E. Valiente, Comparative genome and phenotypic analysis of Clostridium difficile 027 strains provides insight into the evolution of a hypervirulent bacterium, Genome Biol, vol.10, p.102, 2009.

V. G. Loo, L. Poirier, M. A. Miller, M. Oughton, and M. D. Libman, A predominantly clonal multi-institutional outbreak of Clostridium difficile-associated diarrhea with high morbidity and mortality, N Engl J Med, vol.353, pp.2442-2449, 2005.

C. A. Muto, M. Pokrywka, K. Shutt, A. B. Mendelsohn, and K. Nouri, A large outbreak of Clostridium difficile-associated disease with an unexpected proportion of deaths and colectomies at a teaching hospital following increased fluoroquinolone use, Infect Control Hosp Epidemiol, vol.26, pp.273-280, 2005.

E. J. Kuijper, B. Coignard, and P. Tull, Emergence of Clostridium difficile-associated disease in North America and Europe, Clin Microbiol Infect, vol.12, pp.2-18, 2006.

N. G. Rouphael, J. A. O'donnell, J. Bhatnagar, F. Lewis, and P. M. Polgreen, Clostridium difficile-associated diarrhea: an emerging threat to pregnant women, Am J Obstet Gynecol, vol.198, pp.635-631, 2008.

M. D. Zilberberg, G. S. Tillotson, and C. Mcdonald, Clostridium difficile infections among hospitalized children, Emerg Infect Dis, vol.16, pp.604-609, 1997.

S. S. Baker, H. Faden, W. Sayej, R. Patel, and R. D. Baker, Increasing Incidence of Community-Associated Atypical Clostridium difficile Disease in Children, Clin Pediatr (Phila), vol.49, pp.644-647, 2010.

T. V. Riley, Is Clostridium difficile a threat to Australia's biosecurity?, Med J Aust, vol.190, pp.661-662, 2009.

M. Merrigan, A. Venugopal, M. Mallozzi, B. Roxas, and V. K. Viswanathan, Human Hypervirulent Clostridium difficile Strains Exhibit Increased Sporulation as Well as Robust Toxin Production, J Bacteriol, vol.192, pp.4904-4911, 2010.

M. Sebaihia, B. W. Wren, P. Mullany, N. F. Fairweather, and N. Minton, The multidrug-resistant human pathogen Clostridium difficile has a highly mobile, mosaic genome, Nat Genet, vol.38, pp.779-786, 2006.

I. Just, J. Selzer, M. Wilm, V. Eichel-streiber, C. Mann et al., Glucosylation of Rho proteins by Clostridium difficile toxin B, Nature, vol.375, pp.500-503, 1995.

D. Lyras, J. R. O'connor, P. K. Howarth, S. P. Sambol, and G. P. Carter, , 2009.

, Toxin B is essential for virulence of Clostridium difficile, Nature, vol.458, pp.1176-1179

S. A. Kuehne, S. T. Cartman, J. T. Heap, M. L. Kelly, and A. Cockayne, The role of toxin A and toxin B in Clostridium difficile infection, Nature, vol.467, pp.711-713, 2010.

V. Braun, T. Hundsberger, P. Leukel, M. Sauerborn, and E. Cv, Definition of the single integration site of the pathogenicity locus in Clostridium difficile, Gene, vol.181, pp.29-38, 1996.

N. Mani and B. Dupuy, Regulation of toxin synthesis in Clostridium difficile by an alternative RNA polymerase sigma factor, Proc Natl Acad Sci U S A, vol.98, pp.5844-5849, 2001.

K. S. Tan, B. Y. Wee, and K. P. Song, Evidence for holin function of tcdE gene in the pathogenicity of Clostridium difficile, J Med Microbiol, vol.50, pp.613-619, 2001.

S. Matamouros, P. England, and B. Dupuy, Clostridium difficile toxin expression is inhibited by the novel regulator TcdC, Mol Microbiol, vol.64, pp.1274-1288, 2007.

B. Dupuy, R. Govind, A. Antunes, and S. Matamouros, Clostridium difficile toxin synthesis is negatively regulated by TcdC, J Med Microbiol, vol.57, pp.685-689, 2008.

R. Murray, D. Boyd, P. N. Levett, M. R. Mulvey, and M. J. Alfa, Truncation in the tcdC region of the Clostridium difficile PathLoc of clinical isolates does not predict increased biological activity of Toxin B or Toxin A, BMC Infect Dis, vol.9, p.103, 2009.

N. Mani, D. Lyras, L. Barroso, P. Howarth, and T. Wilkins, Environmental response and autoregulation of Clostridium difficile TxeR, a sigma factor for toxin gene expression, J Bacteriol, vol.184, pp.5971-5978, 2002.

J. R. O'connor, D. Lyras, K. A. Farrow, V. Adams, and D. R. Powell, Construction and analysis of chromosomal Clostridium difficile mutants, Mol Microbiol, vol.61, pp.1335-1351, 2006.

D. A. Burns, J. T. Heap, and N. P. Minton, SleC is essential for germination of Clostridium difficile spores in nutrient-rich medium supplemented with the bile salt taurocholate, J Bacteriol, vol.192, pp.657-664, 2010.

S. T. Cartman and N. P. Minton, A mariner-based transposon system for in vivo random mutagenesis of Clostridium difficile, Appl Environ Microbiol, vol.76, pp.1103-1109, 2010.

J. T. Heap, S. A. Kuehne, M. Ehsaan, S. T. Cartman, and C. M. Cooksley, The ClosTron: Mutagenesis in Clostridium refined and streamlined, J Microbiol Methods, vol.80, pp.49-55, 2010.

S. R. Nallapareddy, K. V. Singh, and B. E. Murray, Construction of improved temperature-sensitive and mobilizable vectors and their use for constructing mutations in the adhesin-encoding acm gene of poorly transformable clinical Enterococcus faecium strains, Appl Environ Microbiol, vol.72, pp.334-345, 2006.

G. P. Carter, D. Lyras, D. L. Allen, K. E. Mackin, and P. M. Howarth, Binary toxin production in Clostridium difficile is regulated by CdtR, a LytTR family response regulator, J Bacteriol, vol.189, pp.7290-7301, 2007.

M. M. Awad and J. I. Rood, Isolation of a-toxin, q-toxin and k-toxin mutants of Clostridium perfringens by Tn916 mutagenesis, Microb Pathogen, vol.22, pp.275-284, 1997.

T. Hundsberger, V. Braun, M. Weidmann, P. Leukel, and M. Sauerborn, Transcription analysis of the genes tcdA-E of the pathogenicity locus of Clostridium difficile, European J Bioch, vol.244, pp.735-742, 1997.

N. Razaq, S. Sambol, K. Nagaro, W. Zukowski, and A. Cheknis, Infection of hamsters with historical and epidemic BI types of Clostridium difficile, J Infect Dis, vol.196, pp.1813-1819, 2007.

D. Goulding, H. Thompson, J. Emerson, N. F. Fairweather, and G. Dougan, Distinctive profiles of infection and pathology in hamsters infected with Clostridium difficile strains 630 and B1, Infect Immun, vol.77, pp.5478-5485, 2009.

M. He, M. Sebaihia, T. D. Lawley, R. A. Stabler, and L. F. Dawson, Evolutionary dynamics of Clostridium difficile over short and long time scales, Proc Natl Acad Sci U S A, vol.107, pp.7527-7532, 2010.

M. Rupnik, V. Avesani, M. Janc, V. Eichel-streiber, C. Delmee et al., A novel toxinotyping scheme and correlation of toxinotypes with serogroups of Clostridium difficile isolates, J Clin Microbiol, vol.36, pp.2240-2247, 1998.

M. Richards, J. Knox, B. Elliott, K. Mackin, and D. Lyras, Severe infection with Clostridium difficile PCR ribotype 027 acquired in Melbourne, Australia. Med J Australia, vol.194, pp.369-371, 2011.

S. R. Curry, J. W. Marsh, C. A. Muto, M. M. O'leary, and A. W. Pasculle, tcdC genotypes associated with severe TcdC truncation in an epidemic clone and other strains of Clostridium difficile, J Clin Microbiol, vol.45, pp.215-221, 2007.

D. M. Lyerly, L. A. Barroso, T. D. Wilkins, C. Depitre, and G. Corthier, Characterization of a toxin A-negative, toxin B-positive strain of Clostridium difficile, Infect Immun, vol.60, pp.4633-4639, 1992.

G. P. Carter, J. I. Rood, and D. Lyras, The role of toxin A and toxin B in Clostridium difficile-associated disease: Past and present perspectives, Gut Microbes, vol.1, pp.58-64, 2010.

J. R. O'connor, J. S. Gerding, and D. N. , Clostridium difficile infection caused by the epidemic BI/NAP1/027 strain, Gastroenterology, vol.136, pp.1913-1924, 2009.

J. T. Heap, O. J. Pennington, S. T. Cartman, G. P. Carter, and N. P. , The ClosTron: a universal gene knock-out system for the genus Clostridium, J Microbiol Meth, vol.70, pp.452-464, 2007.

P. Mullany, M. Wilks, and S. Tabaqchali, Transfer of Tn916 and Tn916DE into Clostridium difficile: demonstration of a hot-spot for these elemnets in the C. difficile genome, FEMS Microbiol Lett, vol.79, pp.191-194, 1991.

N. Minton, G. Carter, M. Herbert, T. O'keeffe, and D. Purdy, The development of Clostridium difficile genetic systems, Anaerobe, vol.10, pp.75-84, 2004.

A. Goorhuis, S. B. Debast, L. A. Van-leengoed, C. Harmanus, and D. W. Notermans, Clostridium difficile PCR ribotype 078: an emerging strain in humans and in pigs?, J Clin Microbiol, vol.46, 1157.

L. F. Dawson, E. Valiente, and B. W. Wren, Clostridium difficile-a continually evolving and problematic pathogen, Infect Genet Evol, vol.9, pp.1410-1417, 2009.

R. A. Stabler, L. F. Dawson, L. T. Phua, and B. W. Wren, Comparative analysis of BI/NAP1/027 hypervirulent strains reveals novel toxin B-encoding gene (tcdB) sequences, J Med Microbiol, vol.57, pp.771-775, 2008.

J. M. Lanis, S. Barua, and J. D. Ballard, Variations in TcdB activity and the hypervirulence of emerging strains of Clostridium difficile, PLoS Pathog, vol.6, p.1001061, 2010.

C. Schwan, B. Stecher, T. Tzivelekidis, M. Van-ham, and M. Rohde, Clostridium difficile toxin CDT induces formation of microtubule-based protrusions and increases adherence of bacteria, PLoS Pathog, vol.5, p.1000626, 2009.

T. Akerlund, I. Persson, M. Unemo, T. Noren, and B. Svenungsson, Increased sporulation rate of epidemic Clostridium difficile Type 027/NAP1, J Clin Microbiol, vol.46, pp.1530-1533, 2008.

T. D. Lawley, C. S. Walker, A. W. Goulding, D. Stabler, and R. A. , Antibiotic treatment of Clostridium difficile carrier mice triggers a supershedder state, spore-mediated transmission, and severe disease in immunocompromised hosts, Infect Immun, vol.77, pp.3661-3669, 2009.

S. Johnson, Recurrent Clostridium difficile infection: a review of risk factors, treatments, and outcomes, J Infect, vol.58, pp.403-410, 2009.

J. A. Lindsay, Genomic variation and evolution of Staphylococcus aureus, Int J Med Microbiol, vol.300, pp.98-103, 2010.

M. J. Bonten, R. Willems, and R. A. Weinstein, Vancomycin-resistant enterococci: why are they here, and where do they come from?, Lancet Infect Dis, vol.1, pp.314-325, 2001.

C. J. Smith, S. M. Markowitz, and F. L. Macrina, Transferable tetracycline resistance in Clostridium difficile, Antimicrob Agents and Chemother, vol.19, pp.997-1003, 1981.

J. Sambrook and D. W. Russell, Molecular Cloning: A Laboratory Manual, 2001.

M. M. Awad, A. E. Bryant, D. L. Stevens, and J. I. Rood, Virulence studies on chromosomal a-toxin and q-toxin mutants constructed by allelic exchange provide genetic evidence for the essential role of a-toxin in Clostridium perfringensmediated gas gangrene, Mol Microbiol, vol.15, pp.191-202, 1995.

R. Govind, G. Vediyappan, R. D. Rolfe, and J. A. Fralick, Evidence that Clostridium difficile TcdC is a membrane-associated protein, J Bacteriol, vol.188, pp.3716-3720, 2006.

M. D. Abramoff, P. J. Magelhaes, and S. J. Ram, Image Processing with ImageJ. Biophotonics Internatl, vol.11, pp.36-42, 2004.

J. W. Marsh, M. M. O'leary, K. A. Shutt, A. W. Pasculle, and S. Johnson, Multilocus variable-number tandem-repeat analysis for investigation of Clostridium difficile transmission in Hospitals, J Clin Microbiol, vol.44, pp.2558-2566, 2006.

H. W. Boyer and D. Roulland-dussoix, A complementation analysis of the restriction and modification of DNA in Escherichia coli, J Mol Biol, vol.41, pp.459-472, 1969.

J. Wust, N. M. Sullivan, U. Hardegger, and T. D. Wilkins, Investigation of an outbreak of antibiotic-associated colitis by various typing methods, J Clin Microbiol, vol.16, pp.1096-1101, 1982.

P. Mullany, M. Wilks, I. Lamb, C. Clayton, and B. Wren, Genetic analysis of a tetracycline resistance element from Clostridium difficile and its conjugal transfer to and from Bacillus subtilis, J Gen Microbiol, vol.136, pp.1343-1349, 1990.