SUMMARYThe virulence of Campylobacter jejuni and C. coli isolated from various water sources was compared with that of clinical strains by in vitro assays of adhesion, invasion and cytotoxicity to HeLa cells. Variation in degree of attachment was observed, but this did not appear to be related to strain source, However, water strains were less invasive and less cytotoxic to HeLa cells than clinical strains as shown by immunofluorescence and electron microscopy.These differences were particularly evident between clinical and water isolates of the same serotype and biotype implicated in an outbreak of campylobacter enteritis in a school. The enhanced virulence of the clinical isolates, possibly induced by passage, was confirmed by colonization tests on infant mice.

SummaryWe have studied, over a wide range of dilutions using techniques of clot weight, thrombelastography and scanning electron microscopy, the physical properties of a blood clot formed in vitro when fresh blood was diluted with gelatinbased colloid solutions compared with crystalloid controls. The colloid solutions tested (3.5% polygeline (Haemaccel) and 4% succinylated gelatin (Gelofusine)) produced clots that had reduced median weight (P:0.001 and P:0.018, respectively) and reduced mean shear modulus (P:0.001) compared with crystalloid controls. Scanning electron microscopy showed that the fibrin formed a less extensive mesh in the presence of the gelatin-based colloids compared with crystalloid. Reduction in clot quality with gelatin-based colloids has not been noted previously and further work is needed to ascertain if this occurs in vivo as these solutions are used frequently in patients who require full haemostatic competence. (Br. J. Anaesth. 1998; 80: 204-207) Keywords: blood, coagulation; blood, colloids; fluids, i.v.; blood, haemostasis; blood, replacement; measurement techniques, thrombelastography Plasma substitutes containing degraded and modified gelatin are being used increasingly in prehospital, resuscitation, perioperative and intensive care situations. Often they are the fluid of choice in patients with uncontrolled haemorrhage both before blood transfusion and in conjunction with transfusion of packed cells. Unlike the dextran and starch solutions, so far they have been considered as having no significant effect on clotting mechanisms following studies based principally on clotting times. [1][2][3][4] While measuring whole blood coagulation times after in vitro dilution with colloids we noted a striking difference in clot quality compared with that seen with dilution using crystalloid. Our preliminary findings have been reported previously.5 In this article we describe more detailed investigations using clot weights, haematological analysis, thrombelastography and scanning electron microscopy, and include a description of the dose-response effect of varying degrees of dilution using regression analysis. Materials and methodsWherever fresh whole blood was used, care was taken to avoid prolonged venous stasis, venepuncture from the same site or delays in pipetting, and experiments were conducted under strict temperature control.CLOT WEIGHTS A total of 35 fresh whole blood samples were diluted to 15%, 30%, 45%, 60% and 75% with 0.9% sodium chloride and Ringer's solution (controls) or the test substances, 4% succinylated gelatin (Gelofusine, B. Braun (Medical) Ltd) and 3.5% polygeline solution (Haemaccel, Hoescht UK Ltd). After dividing each sample into test and control, the total volume of each sample after dilution was 5 ml. Clot weights were measured using the method described by Macfarlane.6 Because the clots would not adhere to a glass rod the test was modified by separating the clot from plasma on gauze in a funnel. Clots were weighed on an electronic balance and then examined physica...

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