No abstract

In order to test vaccines against enterotoxigenic Escherichia coli (ETEC)-10 CFU B7A or either dose of H10407. B7A had a shorter incubation period than H10407 (P ‫؍‬ 0.001) and caused milder illness; the mean diarrheal output after H10407 challenge was nearly twice that after B7A challenge (P ‫؍‬ 0.01). Females had more abdominal complaints, and males had a higher incidence of fever. Ciprofloxacin generally diminished or stopped symptoms and shedding by the second day of antibiotic treatment, but four subjects shed for one to four additional days. The immune responses to colonization factors CS6 and colonization factor antigen I (CFA/I) and to heat-labile toxin ( Enterotoxigenic Escherichia coli (ETEC)-induced diarrhea is recognized frequently in individuals who travel in developing countries around the world (4,7,8,26,29,47) and is a major medical problem for military personnel deployed in these countries (26,44,45). Since strict personal hygiene and avoidance of local water and fresh and undercooked foods are recommendations with which travelers have difficulty complying, other means to reduce the ETEC attack rate must be considered. The use of short-term chemoprophylaxis and self-treatment for diarrhea are effective for travelers who are unwilling to accept even a short period of illness because of the serious impact it would have on their overall mission. However, the routine use of antimicrobial prophylaxis for the general traveler is not recommended because of the potential for associated adverse drug reactions and the potential to worsen the problem of antibiotic resistance of enteric bacteria (8,25,29,43,47). These factors make development of vaccines against ETEC a priority.

0Introduction. Staphylococcal enterotoxin the vomiting reflex caused by oral SEB re-B (SEB), isolated from cultures of Staphylo-suited from a direct action of absorbed coccus aureus, produces symptoms of food enterotoxin on the vomiting center, inpoisoning in man and other primates 11-3). directly by the action of some secondary Purified SEB (>99V', prepared by the humoral mediating substance released into method of Schantz et al. (4) induces vomit-the circulation, or from a neural stimulus to ing and diarrhea in monkeys when given the vomiting center originating within the either orally or intravenously (iv) (1, 3).gastrointestinal tract. Although considerable effort has been exCross-circulated pairs of rhesus monkeys pended on attempts to clarify the patho-were chosen as an experimental model to genesis whereby oral administration of SEB investigate the mechanism for the emetic induces vomiting, the physiological mecha-response to o-11) administered SEB. During nisms still remain obscure, cross-circulation, Evans blue dye was emWhen crude staphylococcal enterotoxin ployed to evaluate the exchange and distribufiltrates were administered iv or intraperi-tion of blood between the pair. Blood pH, toneally (ip) to cats, Bayliss (5) concluded Pco2, Po., hematocrit, and plasma osmolality that emesis was induced through a periph-were determined at selected intervals eral action involving the vagal nerves. How-throughout the acute study. SEB hemagglutiever, oral administration and intraventricular nating antibody (HA) titers were followed application of the enterotoxin filtrate failed subsequently for a 6-wk period in all monto induce emesis. A subsequent study by keys (9). Clark et a/. (6) with a more purified enteroMethod. Healthy rhesus monkeys, Macaca toxin confirmed the findings of Bayliss (5). mulatto, of both sexes, weighing 3.0-4.5 kg, Sugiyama and coworkers (7, 8) demon-were used. Members of each pair demonstrated that denervation of abdominal vis-strated negative SEB hcn.agglutination titers cera by sympathectomy and abdominal (9) prior to study and were of approximately vagotomy suppressed vomiting in monkeys equal weight. The animals were tranquilized after oral or iv challenge with SEB. They with 20 mg of ketamine hydrochloride intrabelieved that a neural mechanism played a muscularly (im), premedicated with atropine role in SEB-induced vomiting. Although (0.04 mg/kg, im), and anesthetized with these investigators showed that injection of halothane (0.5-1.5 '() vaporized during oxyenterotoxin into the fourth ventricle did not gen inhalation. Unilateral femoral artery produce vomition, destruction of the area and vein cathetei. were placed in each postrema gave complete protection from monkey using Teflon vessel tips (Eatracorboth oral and iv toxin administration. Thus, poreal) to which medical silicon tubing was the question could be raised as to whether attached according to the method of Chapple et al. (10). Monkeys were heparinized imme-

To study biochemical changes in cerebrospinal fluid (CSF), we developed a reliable technique for repeated collection of CSF in anesthetized strain 13 guinea pigs. The animal's head was mounted in a stereotaxic instrument with ventral tilt at 30 degrees, and cisternal puncture was made with an L-shaped, 23-gauge needle through the shaved skin. Clear CSF was collected in a 1-ml syringe surrounded by crushed ice. Each collection procedure lasted for 3 min, and three consecutive collections produced about 0.2 ml of CSF. Sampling was repeated at 3-hr intervals. With intravenous saline infusion (10 ml/kg.hr), a total volume of 0.6-1.0 ml of CSF was collected over 6 to 12 hr. Animals maintained a mean blood pressure, heart rate, and minute volume, with few changes during CSF sampling for the entire collection.

Body surface areas (BSA) were determined for strain 13 guinea pigs with body weights ranging from 19 1 to 10 1 1 g. For this determination, the entire skin of each animal was removed immediately after death and flattened on a wax film with a homogeneous paper. The skin outlines on the papar were cut and weighed for determining BSA. The K value was calculated for each guinea pig as the ratio of BSA (cm2)/body weight (g)2/3. Significantly different K values of 1 1.3 1 f 0.1 1, 9.66 ? 0.09, 9.22 ? 0.05, and 9.17 ? 0.05 were determined for average body weights of 2 18 ? 24,527 k 33, 706 ? 60, and 943 -t 30 g, respectively. By plotting these K values on semilog paper and determining the best fit curve of the slope, it was possible to extrapolate exponentially the K values for different body weights. The relationship between age and body weight was also established for guinea pigs, and a series of K values were determined from birth to 35 weeks of life. We conclude that a different K value should be used for calculating BSA for various ages and body weights of strain 13 guinea pigs. o