Impaired biliary elimination of beta-glucuronidase-resistant "glucuronides" of valproic acid after intravenous administration in the rat. Evidence for oxidative metabolism of the resistant isomers.

A major metabolite of valproic acid (VPA) is its glucuronic acid conjugate (VPA-G). The disposition of VPA-G was compared with that of its intramolecularly rearranged, beta-glucuronidase-resistant isomers (collectively called VPA-G-R) after iv bolus administration to pentobarbitone-anesthetized rats. VPA-G was eliminated from blood more rapidly than VPA-G-R. After administration of dose A (predominantly VPA-G) and dose B (predominantly VPA-G-R) to rats with catheterized bladders and bile ducts, total conjugated VPA in blood declined from 110 micrograms of VPA/ml at 2 min to 1.1 micrograms/ml at 1 and 3 hr, respectively. A role for systemic hydrolysis of VPA-G was demonstrated by blood concentrations of free VPA which increased until 30 min. A minor role for systemic hydrolysis of VPA-G-R may be possible but cannot be proved from the current data. Urinary excretion (57 and 56% of doses A and B, respectively, in 3 hr) was greater than biliary excretion (32 and 10% of the doses, respectively, in 3 hr). The lower biliary elimination of VPA-G-R may be caused in part by impaired transport from blood to hepatocytes and/or hepatocytes to bile, but a role for phase I metabolism of the VPA moiety of VPA-G-R was demonstrated by recovery of 4.4% of dose B as 4-hydroxy-VPA. This latter mechanism was less (or not) applicable to VPA-G since only 0.4% of dose A was recovered as 4-hydroxy-VPA. Other VPA metabolites measured were quantitatively less important. These results were consistent in rats where either or both of the urinary and biliary elimination routes were surgically blocked.

"Radiochemically pure [1-14C]valproic acid"--a mixture of labeled structural isomers.

Ongoing studies of the disposition of valproic acid (VPA) and its glucuronide conjugate required the radiolabeled drug for greater sensitivity and tracing of oxidation metabolites. [1-14C]VPA hereinafter called LABEL (radiochemical purity greater than 98% as determined by paper and thin layer chromatography) was purchased from Amersham International, U.K. Quantitative analysis of VPA and VPA-glucuronide in bile and urine samples from rats given VPA and tracer LABEL by our standard gas chromatographic assay showed gross discrepancies with the results obtained by liquid scintillation counting of the same extracts. Examination of the purity of LABEL was therefore undertaken. Equilibration of LABEL between various organic-aqueous solvent pairs was identical to that of authentic VPA. However, gas chromatographic-mass spectrometric analysis of the trimethylsilyl derivative of LABEL revealed it to be a mixture of labeled 2-methylheptanoic acid (approximately 60%), 2-ethylhexanoic acid (approximately 30%), and 2-propylpentanoic acid (i.e., VPA, 5-10%). The origin of the isomers of VPA in LABEL was logically traced to the synthetic procedure--coupling of the Grignard reagent of (an isomeric mixture of 2-, 3-, and 4-) chloroheptane(s) with [14C]carbon dioxide. This result highlights the inadequacy of the quality control procedures used and reinforces the necessity for caution in accepting the quoted purity of radiolabeled drugs.

A waterborne outbreak of gastroenteritis with secondary person-to-person spread. Association with a viral agent.

In December, 1976, an outbreak of gastroenteritis occurred at a resort camp in Colorado. Data obtained by questionnaire from 760 persons indicated that 418 (55%) had had gastroenteritis at the camp or within a week of leaving it, with peak onset within a two-day period. Symptoms included vomiting (81%), diarrhoea (65%), and fever (49%); median duration of illness was twenty-four hours. The attack-rate increased with consumption of water or ice-containing beverages. The camp water supply was found to be inadequately chlorinated and contaminated by a leaking septic tank. Although routine laboratory tests did not reveal bacterial, viral, or parasitic pathogens, immune electron microscopy detected virus-like particles in two of five diarrhoeal stool filtrates. Oral administration of one of these bacteria-free filtrates to two volunteers induced a gastrointestinal illness similar to that observed in the camp visitors.

Isolation of Yersinia enterocolitica from well water and growth in distilled water.

Yersinia enterocolitica was recovered from well water during a large water-borne outbreak of gastrointestinal illness. Isolates were predominantly Nilehn biotype 1, of which 57% were serologically nontypable. Isolation and enumeration of these Y. enterocolitica strains were made on M-Endo broth. Laboratory studies were conducted on selected isolates to establish the growth of Y. enterocolitica in distilled water and the competitive growth of this organism in various enteric media. Growth was obtained in sterile distilled water without added nutrients at 4, 25, and 37 degrees C. M-Endo medium gave equal or better recovery of Y. enterocolitica in competitive growth studies than did other commonly used enteric media using the membrane filter technique and incubating at 35 degrees C. All well water isolates were confirmed biochemically at 25 and 35 degrees C and serotyped, and antibiotic susceptibility tests were performed.

A communitywide outbreak of giardiasis with evidence of transmission by a municipal water supply.

Three hundred fifty residents of Rome, New York, had laboratory-confirmed cases of giardiasis between 1 November 1974 and 7 June 1975. A random household survey showed an overall attack rate for giardiasis (defined as a diarrheal illness of 5 days or more) of 10.6%. A significant association was discovered between having giardiasis and using city water and between having illness and drinking 1 or more glasses of water a day. The presence of human settlements in the Rome watershed area suggested that the water supply could have been contaminated by untreated human waste. The infectivity of municipal water was confirmed by producing giardiasis in specific pathogen-free dogs fed sediment samples of raw water obtained from an inlet of a city reservoir. A microscopic examination of the water sediments uncovered a Giardia lamblia cyst in one sample. This was the first time that a G. lamblia cyst has been found in municipal water in an epidemic and the first time that such water has been shown to infect laboratory animals.

Waterborne gastrointestinal illness at a ski resort. --Isolation of Yersinia enterocolitica from drinking water--.

Approximately 41 percent of the visitors and employees who were at a ski resort in Montana between December 23, 1974, and January 17, 1975, became ill with diarrhea and other gastrointestinal symptoms. The association between illness and water consumption proved to be significant, and the previously noncontaminated water supply was found to contain coliforms. No pathogens except Yersinia enterocolitica were isolated, and it was isolated from two wells serving the area. The role of Y. enterocolitica in this outbreak is not clear, but it was the only organism isolated that is known to be pathogenic.

Shigellosis at sea: an outbreak aboard a passenger cruise ship.

Between June 23 and June 30, 1973, 90% of 650 passengers and at least 35% of 299 crew members experienced a diarrheal illness during a 7-day Caribbean cruise aboard a passenger cruise liner. Symptoms were consistent with shigellosis, and Shigella flexneri 6, Boyd 88 biotype, was isolated from rectal swabs taken from 8 to 35 ill passengers and 33 of 294 crew members. Epidemiologic evidence incriminated the ship's water, including ice, as the probable vehicle of transmission, and elevated coliform counts were found in potable water samples obtained aboard the vessel at the peak of the outbreak. Potential sources of contamination of the vessel's potable water supply were investigated, and improvements in the loading and chlorination of potable water were recommended.

Gastrointestinal illness on passenger cruise ships.

Medical logs of 2,445 cruises taken by 38 vessels over a 20-month period beginning Jan 1, 1972, were reviewed. On 92% of the cruises, the recorded incidence of gastrointestinal illness was 1% or less; on 2% of cruises, it was 5% or greater. The actual incidence of gastrointestinal illness determined by a questionnaire survey of passengers sailing on nine cruises was found to be at least four times as high as that recorded in the medical logs. Although the cause of the illnesses was not known, there was evidence that transmission took place aboard ship. A survey of food-handling practices and water systems aboard selected ships demonstrated a significant potential for transmission of foodborne and waterborne disease.