Roles of putative type II secretion and type IV pilus systems in the virulence of uropathogenic Escherichia coli.
BACKGROUND
Type II secretion systems (T2SS) and the evolutionarily related type IV pili (T4P) are important virulence determinants in many Gram-negative bacterial pathogens. However, the roles of T2SS and T4P in the virulence of extraintestinal pathogenic Escherichia coli have not been determined.


RESULTS
To investigate the functions of putative T2SS and T4P gene clusters present in the model uropathogenic E. coli (UPEC) strains UTI89 and CFT073, we deleted the secretin gene present in each cluster. The secretin forms a channel in the outer membrane that is essential for the function of T2S and T4P systems. We compared the secretin deletion mutants with their wild type counterparts using tissue culture assays and the CBA/J mouse model of ascending urinary tract infection. No deficiencies were observed with any of the mutants in adherence, invasion or replication in human bladder or kidney cell lines, but UTI89 DeltahofQ and UTI89 DeltagspD exhibited approximately 2-fold defects in fluxing out of bladder epithelial cells. In the mouse infection model, each of the knockout mutants was able to establish successful infections in the bladder and kidneys by day one post-infection. However, UTI89 DeltahofQ and a CFT073 DeltahofQ DeltayheF double mutant both exhibited defects in colonizing the kidneys by day seven post-infection.


CONCLUSIONS
Based on our results, we propose that the putative T4P and T2S systems are virulence determinants of UPEC important for persistence in the urinary tract, particularly in renal tissues.
Kulkarni
Ritwij
R
Center for Infectious Diseases, Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America.
Dhakal
Bijaya K
BK
Slechta
E Susan
ES
Kurtz
Zachary
Z
Mulvey
Matthew A
MA
Thanassi
David G
DG
D000818:Animals; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D010641:Phenotype; D012633:Secretin / Q000502:physiology*; D001743:Urinary Bladder / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D014552:Urinary Tract Infections / Q000382:microbiology*; D014774:Virulence
D015850:Interleukin-6; D012633:Secretin