Dientamoeba fragilis, a common intestinal protozoan parasite in Canada, has been associated with diarrhoea and abdominal pain in some patients. Seroprevalence of this organism has not been reported previously. In the present study sera from three symptomatic patients, 12 age- and sex-matched controls, and 189 randomly selected healthy individuals (age 6 months to 19 years) were tested for antibodies against Dientamoeba fragilis by an indirect immunofluorescence (IIF) assay. All three symptomatic patients infected with Dientamoeba fragilis had positive IIF titres of 80, and all 12 matched controls had positive titres ranging 20 to 160 (geometric mean titre 48). Of the 189 healthy children, 172 (91%) were positive at a serum dilution of 1:10 or higher. The specificity of the IIF assay was reinforced by immunoblotting 20 representative serum samples against Dientamoeba fragilis. In all 17 IIF-positive serum samples, a 39 kDa protein band of Dientamoeba fragilis was identified, the same band recognized by a mouse monoclonal antibody raised in our laboratory. Findings over a five-year period indicate that Dientamoeba fra-gilis was the most common protozoan, followed closely by Giardia lamblia and more distantly by Cryptosporidium parvum. The high seropositivity of 91% for Dientamoeba fragilis compares reasonably well with serologic data obtained by IIF and reported previously for Giardia lamblia (85.6%) and Cryptosporidium parvum (86%).

An outbreak of erythromycin-resistant, exfoliative toxin-producing Staphylococcus aureus infection in a neonatal unit is described. The organism was coagulase positive but staphyloslide negative, and this unusual phenotype facilitated early recognition of the organism in the routine laboratory. In the initial outbreak there were 77 probable or confirmed cases, with a peak attack rate of 66%. Increased infection control measures were put in place and attempts were made to identify a staff carrier. No carriers were found and the major outbreak subsided. Sporadic cases occurred over the following 10 months, until May 1992, when a colonized staffperson was discovered. She was treated and no further cases occurred. The causative organism was subjected to typing by phage, enterobacterial repetitive intergenic consensus sequence polymerase chain reaction, and pulsed-field gel electrophoresis with two separate enzymes. The phage typing and genomic tests confirmed the presence of the same clone in the unit for 9 months. The organism possessed genes encoding exfoliative toxin A as determined by polymerase chain reaction.

A double-blind, placebo-controlled study was conducted to document possible side effects associated with oral consumption of synthetic verotoxin (VT, shiga-like toxin) Pk-trisaccharide receptor sequences attached to Chromosorb (Synsorb-Pk) by healthy adult volunteers. Synsorb-Pk reclaimed from volunteer stool samples was also analyzed to determine if its VT-binding activity was affected by exposure to the pH extremes and digestive processes of the human gastrointestinal tract. No participant reported any Synsorb-Pk-related adverse reactions, and no clinically important trends in laboratory data were evident. Synsorb-Pk recovered from stools retained its ability to absorb VT in polymyxin extracts of VT-producing Escherichia coli and also neutralized VT when mixed in vitro with VT-positive stools from children with hemorrhagic colitis or hemolytic-uremic syndrome (HUS). These results suggest a potential use for Synsorb-Pk in preventing HUS in patients infected with VT-producing E. coli.

Arcanobacterium haemolyticum has been described as a rare cause of systemic invasive disease and is occasionally isolated from throat swabs. We describe a 2-year study of the incidence and clinical features of A. haemolyticus infection in a pediatric and adolescent population. A total of 11,620 throat swabs were examined for A. haemolyticum with use of a locally developed selective medium. Controls (2,241) were healthy students who were recruited from a separate study. A. haemolyticum was isolated from 42 patients, with the maximum incidence in the 15 to 18-year-old age group; in this subset the incidence was 2.5%. There were no isolates of A. haemolyticum found in the healthy controls, and the difference in incidence between patients and controls in the 15 to 18-year-old age group was highly significant (P <.01). Approximately half of the patients infected with A. haemolyticum had a rash. In 5 patients, A. haemolyticum was associated with a positive monospot test. The organism was highly susceptible to erythromycin and less susceptible to penicillin. The evidence from this study suggests that A. haemolyticum may be a pathogen with maximum incidence in the 15 to 18-year-old age group.

To determine whether the risk factors for childhood haemolytic uraemic syndrome (HUS) are similar to risk factors previously reported for Escherichia coli O 157. H7 gastroenteritis, we conducted a case-control study at eight paediatric hospitals in the summer of 1990. Thirty-four consecutive children with HUS were prospectively enrolled; all had diarrhoea and 88 % had laboratory evidence of exposure to verotoxin-producing E. coli (VTEC). The 102 controls were otherwise healthy children with minor acute injuries. Parents of all subjects responded to a questionnaire about each child's exposure to various foods, methods of food preparation, sources of water, travel, and individuals with diarrhoea.Children with HUS were significantly more likely than controls to have had close contact with an individual with diarrhoea in the 2 weeks before the onset of illness (74 v. 29%, P < 0.00001; odds ratio 7.0, 95% CI 2.7 18.5). The onset of diarrhoea in the contacts occurred a median of 6 days (range, 1- > 14 days) before the onset of diarrhoea in the HUS patients. Exposure to undercooked ground meat was not significantly more common in the patients with HUS (15 v. 8%; P = 0.05). These data provide evidence consistent with person-to-person transmission of VTEC in a substantial proportion of episodes of childhood HUS.