Microbial and host factors that influence adherence of Escherichia coli to kidney epithelium

Hypertonic saline enhances host response to bacterial challenge by augmenting receptor-independent neutrophil intracellular superoxide formation

OBJECTIVE

This study sought to determine whether hypertonic saline (HTS) infusion modulates the host response to bacterial challenge.

METHODS

Sepsis was induced in 30 Balb-C mice by intraperitoneal injection of Escherichia coli (5 x 107 organisms per animal). In 10 mice, resuscitation was performed at 0 and 24 hours with a 4 mL/kg bolus of HTS (7.5% NaCl), 10 animals received 4 mL/kg of normal saline (0.9% NaCl), and the remaining animals received 30 mL/kg of normal saline. Samples of blood, spleen, and lung were cultured at 8 and 36 hours. Polymorphonucleocytes were incubated in isotonic or hypertonic medium before culture with E. coli. Phagocytosis was assessed by flow cytometry, whereas intracellular bacterial killing was measured after inhibition of phagocytosis with cytochalasin B. Intracellular formation of free radicals was assessed by the molecular probe CM-H(2)DCFDA. Mitogen-activated protein (MAP) kinase p38 and ERK-1 phosphorylation, and nuclear factor kappa B (NFkappaB) activation were determined. Data are represented as means (SEM), and an analysis of variance test was performed to gauge statistical significance.

RESULTS

Significantly reduced bacterial culture was observed in the animals resuscitated with HTS when compared with their NS counterparts, in blood (51.8 +/- 4.3 vs. 82.0 +/- 3.3 and 78.4 +/- 4.8, P = 0.005), lung (40.0 +/- 4.1 vs. 93.2 +/- 2.1 and 80.9 +/- 4.7, P = 0.002), and spleen (56.4 +/- 3.8 vs. 85.4 +/- 4.2 and 90.1 +/- 5.9, P = 0.05). Intracellular killing of bacteria increased markedly (P = 0.026) and superoxide generation was enhanced upon exposure to HTS (775.78 +/- 23.6 vs. 696.57 +/- 42.2, P = 0.017) despite inhibition of MAP kinase and NFkappaB activation.

CONCLUSIONS

HTS significantly enhances intracellular killing of bacteria while attenuating receptor-mediated activation of proinflammatory cascades.

Prognosis in pyelonephritis: promise or progress?

Prognosis in pyelonephritis, or upper urinary tract infection, is provided. This infection is not responsible for progressive renal disease in young or elderly patients but accounts for frequent febrile episodes in women of all ages and men after the age of 50. Vigorous local immune response develops with the infection, which never succeeds in eradicating bacteria but does limit the infection and provides a diagnostic test: the antibody-coated bacteria test. Emphasis is placed on the need for a localization test for upper tract infection because studies based exclusively on clinical criteria are invalid. Appropriate therapy for mildly ill patients is given with recommendations of combination therapy for severely ill persons. Long-term follow-up is critical because most patients with recurrent infections can be given preventive therapy without subjecting them to needless urologic evaluation.