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Dissemination and systemic colonization of uropathogenic Escherichia coli in a murine model of bacteremia.

Smith SN, Hagan EC, Lane MC, Mobley HL - MBio (2010)

Bottom Line: UPEC was recovered from the spleen, liver, kidneys, lungs, heart, brain, and intestines as early as 20 min postinoculation, peaking at 24 h postinoculation.A nonpathogenic E. coli K-12 strain, however, disseminated at significantly lower levels (P < 0.01) and was cleared from the liver and cecum by 24 h postinoculation.Isogenic mutants lacking type 1 fimbriae, P fimbriae, capsule, TonB, the heme receptors Hma and ChuA, or particularly the sialic acid catabolism enzyme NanA were significantly outcompeted by wild-type CFT073 during bacteremia (P < 0.05), while flagellin and hemolysin mutants were not.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

ABSTRACT
Infection with uropathogenic Escherichia coli (UPEC), the causative agent of most uncomplicated urinary tract infections, proceeds in an ascending manner and, if left untreated, may result in bacteremia and urosepsis. To examine the fate of UPEC after its entry into the bloodstream, we developed a murine model of sublethal bacteremia. CBA/J mice were inoculated intravenously with 1 × 10(6) CFU of pyelonephritis strain E. coli CFT073 carrying a bioluminescent reporter. Biophotonic imaging, used to monitor the infection over 48 h, demonstrated that the bacteria disseminated systemically and appeared to localize at discrete sites. UPEC was recovered from the spleen, liver, kidneys, lungs, heart, brain, and intestines as early as 20 min postinoculation, peaking at 24 h postinoculation. A nonpathogenic E. coli K-12 strain, however, disseminated at significantly lower levels (P < 0.01) and was cleared from the liver and cecum by 24 h postinoculation. Isogenic mutants lacking type 1 fimbriae, P fimbriae, capsule, TonB, the heme receptors Hma and ChuA, or particularly the sialic acid catabolism enzyme NanA were significantly outcompeted by wild-type CFT073 during bacteremia (P < 0.05), while flagellin and hemolysin mutants were not.

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Real-time imaging of UPEC dissemination during bacteremia. (A) Splenic bacterial loads at 3 hpi following intravenous inoculation of CBA/J mice with the indicated doses of E. coli CFT073(pGEN-lux). Filled circles represent numbers of CFU/g from individual animals, and bars show the medians. The limit of detection was 100 CFU/g. (B) Biophotonic imaging of the ventral (top) and dorsal (bottom) sides of a live mouse at 0.3 (left), 4 (left center), 24 (right center), and 48 (right) h following intravenous inoculation with 106 CFU. (C) Biophotonic imaging of an excised spleen (bottom left) at 0.3 h and the ileum (top left), colon (top right), and cecum (bottom right) at 48 h following inoculation as described for panel B. (D) Quantification of luminescence imaged from the thoracic ventral (left) and dorsal (right) sides of mice inoculated as described for panel B. Mean luminescence is shown, and error bars represent the standard error of the mean (n = 10).
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f1: Real-time imaging of UPEC dissemination during bacteremia. (A) Splenic bacterial loads at 3 hpi following intravenous inoculation of CBA/J mice with the indicated doses of E. coli CFT073(pGEN-lux). Filled circles represent numbers of CFU/g from individual animals, and bars show the medians. The limit of detection was 100 CFU/g. (B) Biophotonic imaging of the ventral (top) and dorsal (bottom) sides of a live mouse at 0.3 (left), 4 (left center), 24 (right center), and 48 (right) h following intravenous inoculation with 106 CFU. (C) Biophotonic imaging of an excised spleen (bottom left) at 0.3 h and the ileum (top left), colon (top right), and cecum (bottom right) at 48 h following inoculation as described for panel B. (D) Quantification of luminescence imaged from the thoracic ventral (left) and dorsal (right) sides of mice inoculated as described for panel B. Mean luminescence is shown, and error bars represent the standard error of the mean (n = 10).

Mentions: To examine the pathogenesis of UPEC in the bloodstream, we developed a murine model of E. coli bacteremia. Prototypical pyelonephritis strain E. coli CFT073 is a urosepsis strain isolated from both the blood and urine of a patient with acute pyelonephritis (22). Female CBA/J mice were inoculated intravenously via tail vein injection with CFT073 carrying a stable luminescent reporter, pGEN-lux (20), at various doses. At 3 h postinoculation (hpi), the bacterial load in the spleen was assessed as an indicator of bacteremia. Bacteria could be recovered from the spleens of animals inoculated with a dose as low as 103 CFU/mouse (Fig. 1A). Spleens excised 20 min postinoculation from infected animals were luminescent (Fig. 1C), indicating that the bacteremia was due to CFT073(pGEN-lux). The median infectious dose (ID50) was determined to be 105 CFU/mouse and yielded a median bacterial load of approximately 103 CFU/g spleen. For comparison, the ID50 for transurethral inoculation of this urinary isolate is 106 CFU/mouse (23). To ensure infection of a larger proportion of the population, 10 times the ID50 (106 CFU/mouse) was used for all subsequent experiments.


Dissemination and systemic colonization of uropathogenic Escherichia coli in a murine model of bacteremia.

Smith SN, Hagan EC, Lane MC, Mobley HL - MBio (2010)

Real-time imaging of UPEC dissemination during bacteremia. (A) Splenic bacterial loads at 3 hpi following intravenous inoculation of CBA/J mice with the indicated doses of E. coli CFT073(pGEN-lux). Filled circles represent numbers of CFU/g from individual animals, and bars show the medians. The limit of detection was 100 CFU/g. (B) Biophotonic imaging of the ventral (top) and dorsal (bottom) sides of a live mouse at 0.3 (left), 4 (left center), 24 (right center), and 48 (right) h following intravenous inoculation with 106 CFU. (C) Biophotonic imaging of an excised spleen (bottom left) at 0.3 h and the ileum (top left), colon (top right), and cecum (bottom right) at 48 h following inoculation as described for panel B. (D) Quantification of luminescence imaged from the thoracic ventral (left) and dorsal (right) sides of mice inoculated as described for panel B. Mean luminescence is shown, and error bars represent the standard error of the mean (n = 10).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2993011&req=5

f1: Real-time imaging of UPEC dissemination during bacteremia. (A) Splenic bacterial loads at 3 hpi following intravenous inoculation of CBA/J mice with the indicated doses of E. coli CFT073(pGEN-lux). Filled circles represent numbers of CFU/g from individual animals, and bars show the medians. The limit of detection was 100 CFU/g. (B) Biophotonic imaging of the ventral (top) and dorsal (bottom) sides of a live mouse at 0.3 (left), 4 (left center), 24 (right center), and 48 (right) h following intravenous inoculation with 106 CFU. (C) Biophotonic imaging of an excised spleen (bottom left) at 0.3 h and the ileum (top left), colon (top right), and cecum (bottom right) at 48 h following inoculation as described for panel B. (D) Quantification of luminescence imaged from the thoracic ventral (left) and dorsal (right) sides of mice inoculated as described for panel B. Mean luminescence is shown, and error bars represent the standard error of the mean (n = 10).
Mentions: To examine the pathogenesis of UPEC in the bloodstream, we developed a murine model of E. coli bacteremia. Prototypical pyelonephritis strain E. coli CFT073 is a urosepsis strain isolated from both the blood and urine of a patient with acute pyelonephritis (22). Female CBA/J mice were inoculated intravenously via tail vein injection with CFT073 carrying a stable luminescent reporter, pGEN-lux (20), at various doses. At 3 h postinoculation (hpi), the bacterial load in the spleen was assessed as an indicator of bacteremia. Bacteria could be recovered from the spleens of animals inoculated with a dose as low as 103 CFU/mouse (Fig. 1A). Spleens excised 20 min postinoculation from infected animals were luminescent (Fig. 1C), indicating that the bacteremia was due to CFT073(pGEN-lux). The median infectious dose (ID50) was determined to be 105 CFU/mouse and yielded a median bacterial load of approximately 103 CFU/g spleen. For comparison, the ID50 for transurethral inoculation of this urinary isolate is 106 CFU/mouse (23). To ensure infection of a larger proportion of the population, 10 times the ID50 (106 CFU/mouse) was used for all subsequent experiments.

Bottom Line: UPEC was recovered from the spleen, liver, kidneys, lungs, heart, brain, and intestines as early as 20 min postinoculation, peaking at 24 h postinoculation.A nonpathogenic E. coli K-12 strain, however, disseminated at significantly lower levels (P < 0.01) and was cleared from the liver and cecum by 24 h postinoculation.Isogenic mutants lacking type 1 fimbriae, P fimbriae, capsule, TonB, the heme receptors Hma and ChuA, or particularly the sialic acid catabolism enzyme NanA were significantly outcompeted by wild-type CFT073 during bacteremia (P < 0.05), while flagellin and hemolysin mutants were not.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

ABSTRACT
Infection with uropathogenic Escherichia coli (UPEC), the causative agent of most uncomplicated urinary tract infections, proceeds in an ascending manner and, if left untreated, may result in bacteremia and urosepsis. To examine the fate of UPEC after its entry into the bloodstream, we developed a murine model of sublethal bacteremia. CBA/J mice were inoculated intravenously with 1 × 10(6) CFU of pyelonephritis strain E. coli CFT073 carrying a bioluminescent reporter. Biophotonic imaging, used to monitor the infection over 48 h, demonstrated that the bacteria disseminated systemically and appeared to localize at discrete sites. UPEC was recovered from the spleen, liver, kidneys, lungs, heart, brain, and intestines as early as 20 min postinoculation, peaking at 24 h postinoculation. A nonpathogenic E. coli K-12 strain, however, disseminated at significantly lower levels (P < 0.01) and was cleared from the liver and cecum by 24 h postinoculation. Isogenic mutants lacking type 1 fimbriae, P fimbriae, capsule, TonB, the heme receptors Hma and ChuA, or particularly the sialic acid catabolism enzyme NanA were significantly outcompeted by wild-type CFT073 during bacteremia (P < 0.05), while flagellin and hemolysin mutants were not.

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Related in: MedlinePlus