In vivo effects of intravascularly applied Escherichia coli hemolysin: dissociation between induction of granulocytopenia and lethality in monkeys

An active fraction extracted from Lactobacillus acidophilus La5 cell-free spent medium (LAla-5AF) was incorporated in a dairy matrix and tested to assess its antivirulent effect against enterohemorrhagic Escherichia coli (EHEC). Mice in experimental groups were fed for 4 days with yogurt supplemented with LAla-5AF. On the fifth day, mice were challenged with a single dose (107 CFU per mouse) of E. coli O157:H7. The clinical manifestations of the infection were significantly less severe in mice fed the yogurt supplemented with LAla-5AF. EHEC attachment and colonization was attenuated by LAla-5AF. Tumor necrosis factor alpha production was down-regulated, which might indicate a protective effect in the kidney during EHEC infection. To investigate the mechanisms associated with the in vivo effects observed, LAla-5AF was tested by reverse transcription real-time PCR to confirm its effects on the expression of several virulence genes of EHEC O157. The results showed that these fractions were able to down-regulate several virulence genes of EHEC, including stxB2, qseA, luxS, tir, ler, eaeA, and hlyB.

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Regulation of Escherichia coli Hemolysin E Expression by H-NS and Salmonella SlyA

Journal of Bacteriology ◽

10.1128/jb.186.6.1620-1628.2004 ◽

2004 ◽

Vol 186 (6) ◽

pp. 1620-1628 ◽

Cited By ~ 54

Author(s):

Neil R. Wyborn ◽

Melanie R. Stapleton ◽

Valia A. Norte ◽

Ruth E. Roberts ◽

Jamie Grafton ◽

...

Keyword(s):

Escherichia Coli ◽

Transcription Factors ◽

Glucose Starvation ◽

Negative Effects ◽

Environmental Signals ◽

High Affinity ◽

Regulatory Effects ◽

Escherichia Coli Hemolysin ◽

Order Complexes

ABSTRACT The Escherichia coli hlyE gene (also known as clyA or sheA) codes for a novel pore-forming toxin. Previous work has shown that the global transcription factors FNR and CRP positively regulate hlyE expression by binding at the same site. Here in vivo transcription studies reveal that FNR occupies the hlyE promoter more frequently than CRP, providing a mechanism for the moderate upregulation of hlyE expression in response to two distinct environmental signals (oxygen and glucose starvation). It has been reported that H-NS interacts with two large regions of the hlyE promoter (PhlyE), one upstream of the −35 element and one downstream of the −10 element. Here we identify two high-affinity H-NS sites, H-NS I, located at the 3′ end of the extended upstream footprint, and H-NS II, located at the 5′ end of the extended downstream footprint. It is suggested that these high-affinity sites initiate the progressive formation of higher order complexes, allowing a range of H-NS-mediated regulatory effects at PhlyE. Finally, the identification of a SlyA binding site that overlaps the H-NS I site in PhlyE suggests a mechanism to explain how SlyA overproduction enhances hlyE expression by antagonizing the negative effects of H-NS.

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In vivo effects of Escherichia coli endotoxemia on diaphragmatic microcirculation in rats

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.6.2219 ◽

1992 ◽

Vol 72 (6) ◽

pp. 2219-2224 ◽

Cited By ~ 47

Author(s):

J. Boczkowski ◽

E. Vicaut ◽

M. Aubier

Keyword(s):

Escherichia Coli ◽

Blood Pressure ◽

Capillary Perfusion ◽

Vascular Volume ◽

Relative Localization ◽

Catheter Group ◽

In Vivo Effects ◽

Intravenous Inoculation ◽

Observation Period

We investigated the effects of Escherichia coli endotoxin administration on diaphragmatic microcirculation in rats by in vivo videomicroscopy. Rats were allocated into three groups: 1) intravenous inoculation of 10 mg/kg of E. col endotoxin (group E, n = 25), 2) intravenous inoculation of sterile 0.9% NaCl (group C, n = 20), and 3) induction of a controlled hemorrhage by reducing the vascular volume via an arterial catheter (group H, n = 15). Mean blood pressure (BP) and arteriolar diameters were measured at 15-min intervals and capillary perfusion pattern at 30-min intervals for 1 h. BP decreased similarly in groups E and H, whereas it was maintained in group C. Arterioles were classified as second (A2, n = 46), third (A3, n = 22), and fourth (A4, n = 21) order, according to their relative localization in the network. Basal diameters were the same in the three groups: 38.16, 17.33, and 6.80 microns in group C; 38.17, 17.41, and 7.04 microns in group E; and 37.82, 19.19, and 6.99 microns in group H for A2, A3, and A4, respectively. During the observation period, a significant and similar vasoconstriction of A2 arterioles was observed in groups E and H but not in group C. By contrast, in the three groups, no significant changes in diameter were found for the A3 and A4 arterioles. Capillary perfusion was markedly impaired in group E: at 60 min the percentage of non-perfused capillaries was 40.92 +/- 6.65% in group E compared with 21.17 +/- 5.45% in group C (P less than 0.05) and 18.18 +/- 8.11% in group H (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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