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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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Systemic tissue colonization by and persistence of E. coli CFT073 and a commensal K-12 strain. (A) Bacterial loads at 24 h following an intravenous challenge with 106 CFU E. coli CFT073(pGEN-lux) (solid symbols) or E. coli K-12 strain MG1655(pGEN-lux) (open symbols). (B) Bacterial loads in cecal tissue at 3 and 7 days following an intravenous challenge with 106 CFU E. coli CFT073 ΔlacZ (solid symbols) or E. coli K-12 strain MG1655 ΔlacZ (open symbols). Symbols represent individual animals, and bars show the medians. The limit of detection was 100 CFU/g. Statistically significant P values (<0.05) are indicated.
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f4: Systemic tissue colonization by and persistence of E. coli CFT073 and a commensal K-12 strain. (A) Bacterial loads at 24 h following an intravenous challenge with 106 CFU E. coli CFT073(pGEN-lux) (solid symbols) or E. coli K-12 strain MG1655(pGEN-lux) (open symbols). (B) Bacterial loads in cecal tissue at 3 and 7 days following an intravenous challenge with 106 CFU E. coli CFT073 ΔlacZ (solid symbols) or E. coli K-12 strain MG1655 ΔlacZ (open symbols). Symbols represent individual animals, and bars show the medians. The limit of detection was 100 CFU/g. Statistically significant P values (<0.05) are indicated.

Mentions: To determine whether systemic dissemination by UPEC is a pathogen-specific process or simply represents the natural course of bacterial clearance from the bloodstream, nonpathogenic E. coli K-12 strain MG1655 was tested in the bacteremia model. At 24 hpi, the spleen and liver (Fig. 4A) contained significantly lower levels of MG1655(pGEN-lux) than CFT073(pGEN-lux) (P = 0.0024 and P = 0.0087, respectively). Mice infected with MG1655 also had lower levels of cecal colonization, although this difference was not significant at 24 hpi. To examine the persistence dynamics of these strains, cecal colonization was examined at up to 7 dpi. Because pGEN-lux is only stably maintained in CFT073 for 48 h in the absence of antibiotic selection (20), isogenic lacZ mutants of CFT073 and MG1655 were used to allow differentiation from the cecal microbiota. Thus, while it is important to note that this represents a method of bacterial quantification different from that shown previously (Fig. 2 and 4A) that does not depend on the presence of pGEN-lux, cecal colonization by CFT073(pGEN-lux) did not differ from that by CFT073 lacZ at 24 hpi (data not shown). While CFT073 colonization persisted in the cecum at 72 hpi at nearly 104 CFU/g, E. coli MG1655 was cleared by this time point from 9 of 10 mice (P < 0.0001) (Fig. 4B). By 7 dpi, CFT073 had been cleared from the ceca of 7 of 10 mice. These data indicate that nonpathogenic E. coli is not capable of persisting systemically during bacteremia in this model and suggest that UPEC dissemination and persistence represent pathogenic mechanisms.


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

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

Systemic tissue colonization by and persistence of E. coli CFT073 and a commensal K-12 strain. (A) Bacterial loads at 24 h following an intravenous challenge with 106 CFU E. coli CFT073(pGEN-lux) (solid symbols) or E. coli K-12 strain MG1655(pGEN-lux) (open symbols). (B) Bacterial loads in cecal tissue at 3 and 7 days following an intravenous challenge with 106 CFU E. coli CFT073 ΔlacZ (solid symbols) or E. coli K-12 strain MG1655 ΔlacZ (open symbols). Symbols represent individual animals, and bars show the medians. The limit of detection was 100 CFU/g. Statistically significant P values (<0.05) are indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Systemic tissue colonization by and persistence of E. coli CFT073 and a commensal K-12 strain. (A) Bacterial loads at 24 h following an intravenous challenge with 106 CFU E. coli CFT073(pGEN-lux) (solid symbols) or E. coli K-12 strain MG1655(pGEN-lux) (open symbols). (B) Bacterial loads in cecal tissue at 3 and 7 days following an intravenous challenge with 106 CFU E. coli CFT073 ΔlacZ (solid symbols) or E. coli K-12 strain MG1655 ΔlacZ (open symbols). Symbols represent individual animals, and bars show the medians. The limit of detection was 100 CFU/g. Statistically significant P values (<0.05) are indicated.
Mentions: To determine whether systemic dissemination by UPEC is a pathogen-specific process or simply represents the natural course of bacterial clearance from the bloodstream, nonpathogenic E. coli K-12 strain MG1655 was tested in the bacteremia model. At 24 hpi, the spleen and liver (Fig. 4A) contained significantly lower levels of MG1655(pGEN-lux) than CFT073(pGEN-lux) (P = 0.0024 and P = 0.0087, respectively). Mice infected with MG1655 also had lower levels of cecal colonization, although this difference was not significant at 24 hpi. To examine the persistence dynamics of these strains, cecal colonization was examined at up to 7 dpi. Because pGEN-lux is only stably maintained in CFT073 for 48 h in the absence of antibiotic selection (20), isogenic lacZ mutants of CFT073 and MG1655 were used to allow differentiation from the cecal microbiota. Thus, while it is important to note that this represents a method of bacterial quantification different from that shown previously (Fig. 2 and 4A) that does not depend on the presence of pGEN-lux, cecal colonization by CFT073(pGEN-lux) did not differ from that by CFT073 lacZ at 24 hpi (data not shown). While CFT073 colonization persisted in the cecum at 72 hpi at nearly 104 CFU/g, E. coli MG1655 was cleared by this time point from 9 of 10 mice (P < 0.0001) (Fig. 4B). By 7 dpi, CFT073 had been cleared from the ceca of 7 of 10 mice. These data indicate that nonpathogenic E. coli is not capable of persisting systemically during bacteremia in this model and suggest that UPEC dissemination and persistence represent pathogenic mechanisms.

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.

Show MeSH
Related in: MedlinePlus