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Biomedical subjects

S R Dobson

Publications and source records attributed to S R Dobson.

15 recordsLinked to original sources
PubMed2001

Past infection with hepatitis A virus among Vancouver street youth, injection drug users and men who have sex with men: implications for vaccination programs.

BACKGROUND: In Canada, inactivated hepatitis A vaccines are targeted selectively at those at increased risk for infection or its complications. In order to evaluate the need for routine hepatitis A vaccination programs in Vancouver for street youth, injection drug users (IDUs) and men who have sex with men (MSM), we determined the prevalence of antibodies against hepatitis A virus (HAV) and risk factors for HAV in these groups. METHODS: The frequency of past HAV infection was measured in a sample of Vancouver street youth, IDUs and MSM attending outreach and STD clinics and needle exchange facilities by testing their saliva for anti-HAV immunoglobulin G. A self-administered, structured questionnaire was used to gather sociodemographic data. Stepwise logistic regression was used to evaluate the association between presumed risk factors and groups and past HAV infection. RESULTS: Of 494 study participants, 235 self-reported injection drug use, 51 were self-identified as MSM and 111 met street youth criteria. Positive test results for anti-HAV were found in 6.3% of street youth (95% confidence interval [CI] 2.6%-12.6%), 42.6% (95% CI 36.2%-48.9%) of IDUs and 14.7% (95% CI 10.4%-19.1%) of individuals who denied injection drug use. Among men who denied injection drug use, the prevalence was 26.3% (10/38) for MSM and 12% (21/175) for heterosexuals. Logistic regression showed that past HAV infection was associated with increased age and birth in a country with high rates of hepatitis infection. Injection drug use among young adults (25-34 years old) was a significant risk factor for a positive anti-HAV test (p = 0.009). MSM were also at higher risk for past HAV infection, although this association was nominally significant (p = 0.07). INTERPRETATION: Low rates of past HAV infection among Vancouver street youth indicate a low rate of virus circulation in this population, which is vulnerable to hepatitis A outbreaks. An increased risk for HAV infection in IDUs and MSM supports the need to develop routine vaccination programs for these groups also.

Adolescent↗
PubMed1998

Routine prenatal screening for HIV in a low-prevalence setting.

BACKGROUND: The objectives of this study were to assess the effect of British Columbia's June 1994 guidelines for prenatal HIV screening on the rate of maternal-fetal HIV transmission and to estimate the cost-effectiveness of such screening. METHODS: The authors conducted a retrospective review of pregnancy and delivery statistics, HIV screening practices, laboratory testing volume, prenatal and labour management decisions of HIV-positive women, maternal-fetal transmission rates and associated costs. RESULTS: Over 1995 and 1996, 135,681 women were pregnant and 92,645 carried to term. The rate of HIV testing increased from 55% to 76% of pregnancies on chart review at one hospital between November 1995 and November 1996. On the basis of seroprevalence studies, an estimated 50.2 pregnancies and 34.3 (95% confidence interval 17.6 to 51.0) live births to HIV-positive women were expected. Of 42 identified mother-infant pairs with an estimated date of delivery during 1995 or 1996, 25 were known only through screening. Of these 25 cases, there were 10 terminations, 1 spontaneous abortion and 14 cases in which the woman elected to carry the pregnancy to term with antiretroviral therapy. There was one stillbirth. One instance of maternal-fetal HIV transmission occurred among the 13 live births. The net savings attributable to prevented infections among babies carried to term were $165,586, with a saving per prevented case of $75,266. INTERPRETATION: A routine offer of pregnancy screening for HIV in a low-prevalence setting reduces the rate of maternal-fetal HIV transmission and may rival other widely accepted health care expenditures in terms of cost-effectiveness.

British Columbia↗
PubMed1993

Population-based study of non-typable Haemophilus influenzae invasive disease in children and neonates.

The extent of non-capsulate, non-serotypable Haemophilus influenzae (NST) as a cause of serious invasive disease in children has not been fully defined. We describe the epidemiology of these childhood infections from cases identified during a continuing prospective survey of invasive H influenzae disease in the Oxford region, UK. 408 strains of H influenzae were isolated from cases of invasive disease. 383 (94%) were H influenzae type b (Hib), 24 (6%) were NST strains, and 1 was a type f strain. 3 of the NST strains were non-capsulate type b mutants (b-), but the remaining 21 strains were from the phylogenetically distinct and heterogeneous population of non-capsulate H influenzae (NC). 10 of the NC strains were isolated from neonates with sepsis; crude mortality rate was 40%, with an incidence of 4.6 cases per 100,000 livebirths. 11 NC strains were isolated from children after the neonatal period and under 10 years of age, 4 (36%) of which had severe, unrelated, predisposing conditions. The incidence of NC invasive diseases in these children was 0.5 per 100,000 per year. The attributable mortality for these infections was 10%. Infections due to these H influenzae strains are, after the implementation of Hib vaccines, likely to persist and represent a substantial proportion of the serious infections caused by this species.

Blotting, Southern↗
PubMed1992

Insertion sequence IS1016 and absence of Haemophilus capsulation genes in the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius.

Brazilian purpuric fever (BPF) strains of Haemophilus influenzae biogroup aegyptius form a clone of organisms distinct from more innocuous, conjunctivitis-associated isolates. There has been controversy over whether the virulence of BPF strains might derive from the presence of a polysaccharide capsule analogous to that found in conventional invasive H. influenzae, a controversy fuelled by the observation (G. M. Carlone, L. Gorelkin, L. L. Gheesling, A. L. Erwin, S. K. Hoiseth, M. H. O. Mulks, S. P. Connor, R. S. Weyant, J. Myrick, L. Rubin, R. S. Mumford III, E. H. White, R. J. Arko, B. Swaminathan, L. M. Graves, L. W. Mayer, M. K. Robinson, S. P. Caudill, and the Brazilian Purpuric Fever Study Group, J. Clin, Microbiol. 27:609-614, 1989) that a capsulation DNA probe from H. influenzae type b hybridized uniquely to BPF strains. In this work, the basis for this hybridization has been established as the possession by BPF strains, but not by non-BPF strains, of the Haemophilus insertion element IS1016. Although IS1016 is associated with the capsulation locus in some Haemophilus spp., a Southern hybridization study suggests that in BPF strains there are no capsulation genes.

Base Sequence↗
PubMed1992

Reduced use of surface cultures for suspected neonatal sepsis and surveillance.

Data on infection in a neonatal unit were collected prospectively for seven years. After the first four years, the number of surface cultures obtained from neonates with suspected sepsis and for surveillance was reduced. Rates of systemic infection (sepsis and meningitis) were not significantly different in the four years before and the three years after this change. Reduction in surface culture information made no observable difference to detection of colonisation in neonates with early onset sepsis (within first 48 hours of life) nor to antibiotic choice in late onset sepsis. Decisions concerning the length of antibiotic course in suspected infection were not adversely affected. Reduction in the number of surface cultures led to considerable saving of time, effort, and cost while appearing safe in terms of clinical practice and outcome.

Anti-Bacterial Agents↗
PubMed1992

Immunogenicity and safety of PRP-T conjugate vaccine given according to the British accelerated immunisation schedule.

The immunogenicity and safety of a new Haemophilus influenzae type b conjugate vaccine, PRP-T, was studied in 107 infants from the Oxford district. The vaccine was given concurrently with diphtheria, pertussis, tetanus, and polio vaccines at 2, 3, and 4 months of age. Symptoms after immunisation were recorded by a parent. Sera were obtained before the first immunisation and at 5 months of age and the antibodies were measured by both radioimmunoassay and enzyme linked immunosorbent assay (ELISA). No serious adverse reactions were observed and there was no increase in the incidence of expected minor side effects. By radioimmunoassay, the geometric mean titre of serum anticapsular antibody increased from 0.09 micrograms/ml before immunisation to 5.01 micrograms/ml after three immunisations. Ninety eight per cent of children had antibody concentrations consistent with protection (greater than or equal to 0.15 micrograms/ml). IgG antibody concentrations measured by ELISA correlated well with total antibody concentrations measured by radioimmunoassay (r = 0.864). These results provide encouragement that routine immunisation against H influenzae type b at 2, 3, and 4 months of age, could prevent most cases of disease in children in the UK.

Age Factors↗
PubMed1990

Neonatal pneumonia.

All babies admitted to the neonatal unit during a period of 41 months were prospectively studied to find out the incidence, aetiology, and outcome of neonatal pneumonia, and the value of routine cultures of endotracheal tubes. Pneumonia of early onset (before age 48 hours) occurred in 35 babies (incidence 1.79/1000 live births). In 20 (57%) it was caused by group B streptococci. Blood cultures showed the presence of organisms in 16 of the 35 (46%). There were 41 episodes of pneumonia of late onset in 39 babies. Thirty six of the 39 were preterm, and 34 were artificially ventilated (10% of all ventilated babies). Endotracheal tube colonisation had occurred in 94% of these, most commonly by Gram negative organisms and Staphylococcus epidermidis. In only one of seven cases with simultaneous bacteraemia was the same organism grown from cultures of the blood. After controlling for gestational age and duration of artificial ventilation there was no difference in the incidence or timing of endotracheal tube colonisation between babies who did and did not have pneumonia of late onset. Ten babies with pneumonia of early onset (29%) died; all were preterm infants. Only one death (2%) was associated with an episode of pneumonia of late onset. Routine surveillance cultures were not helpful in predicting and managing pneumonia of late onset.

Anti-Bacterial Agents↗
PubMed1990

Enterococcal sepsis in neonates: features by age at onset and occurrence of focal infection.

Fifty-six neonates with enterococcal septicemia in a single hospital from 1977 through 1986 were studied. The incidence was low and constant until 1983, when an increase, attributable to infections in infants older than 7 days of age (late-onset), was noted. These infants were more premature (mean gestational age 29.5 vs 36.9 weeks) and had lower birth weights (mean 1250 vs 2700 g) than those with early-onset enterococcal sepsis, and in most the infections were characterized by a nosocomial origin. Infants with early-onset infection had a mild illness with respiratory distress typical of other etiologic agents or diarrhea without focal infection. By contrast, late-onset enterococcal sepsis was heralded by severe apnea, bradycardia, circulatory collapse, and increased ventilatory requirements. Focal infections, including scalp abscess or catheter-related infection (23% each), meningitis or pneumonia (15% each), were common. Rapid clinical improvement and clearance of bacteremia resulted from therapy with an aminoglycoside and either ampicillin or vancomycin, but only if abscesses were drained and intravascular catheters were removed. Mortality rates for early-onset, late-onset, and necrotizing enterocolitis-associated infection were 6, 8, and 17%, respectively. Enterococcus is a frequent cause of late-onset septicemia in premature neonates, and empiric therapy should include appropriate antimicrobial agents.

Birth Weight↗
PubMed1989

Conservative management of an echovirus 11 outbreak in a neonatal unit.

Two babies in a neonatal unit presented on the same day with meningitis due to echovirus 11, which was thought to have been introduced by staff. At this time echovirus 11 was also isolated from the stools of eight other babies; five of them did not have signs of infection. No intervention was made except to emphasise the importance of handwashing. There was evidence of secondary spread to two babies who were both clinically well. The attack rate was twelve (29%) of forty-one babies exposed. Seven of the twelve infected babies were born before 30 weeks' gestation and would have had little or no maternal antibody, yet only two of the seven babies had signs of infection. Despite lack of special measures, all babies recovered. Most cases of horizontally acquired neonatal echovirus infection are mild: extreme measures in the management of outbreaks are unnecessary.

Anti-Bacterial Agents↗
PubMed1988

Recognition of Treponema pallidum antigens by IgM and IgG antibodies in congenitally infected newborns and their mothers.

Immunoblotting techniques were used to examine the proteins of Treponema pallidum recognized by IgM and IgG antibodies in sera from infants with congenital syphilis and their mothers. Infected infants' serum IgM reactivity to treponemal antigens differed from that of control infants born to normal, serofast, and biologic false-positive mothers. Each of the infected infants' sera exhibited IgM reactions to the 47- and 37-kilodalton (kDa) proteins of T. pallidum. Although rheumatoid factor was detected in the sera of half of the infected infants, removing this factor did not alter the pattern of IgM blots. IgG reactions in infants were almost exclusively of the IgG1 and IgG3 subclasses and mirrored those of the mother, except for IgG1 and IgG3 reactions to the 83-kDa treponemal protein, which were unique to infants' sera. Our results suggest that the findings of IgM antibody directed against the 47- or 37-kDa antigens of T. pallidum may help to diagnose congenital syphilis at birth.

Antigens, Viral↗
PubMed1988

Characterization of the components in circulating immune complexes from infants with congenital syphilis.

Immunoglobulin class-specific Clq-solid-phase assays were used to detect circulating immune complexes in the sera of infants with congenital syphilis. Elevated levels of IgM complexes were present in the sera of all infants with overt disease and in two of 14 asymptomatic infants considered to be "at risk." The sera of infants born to normal, serofast, and biologic false-positive mothers did not contain immune complexes. Immunoblotting techniques revealed that complexes isolated from the sera of the infected infants contained endogenous host antigens, as well as a limited number of treponemal polypeptides. Consistent with earlier findings examining purified immune complexes from adults with secondary syphilis and from infected animals, an 83-kilodalton Treponema pallidum antigen was present in all of the isolated complexes from infants with congenital syphilis. Our findings emphasize the fact that current serological and clinical measures of infection are inadequate and that certain "at risk" infants should be treated despite normal cerebrospinal findings and the absence of clinical manifestations.

Antigen-Antibody Complex↗
PubMed1987

Extensive Actinomyces naeslundii infection in a child.

A case of extensive Actinomyces naeslundii infection in a globally retarded patient is reported. To our knowledge, this uncommon Actinomyces species has not previously been described as a cause of widespread disease. Mental retardation and thoracic scoliosis were identified as features predisposing to infection.

Actinomycosis↗
PubMedDate not supplied

Mechanical instability as a cause of gait disturbance in high-grade spondylolisthesis: a pre- and postoperative three-dimensional gait analysis.

Mechanical instability of the spinopelvic junction is a suspected cause of abnormal gait in high-grade spondylolisthesis. Computerized three-dimensional gait analysis was performed on a 10-year-old with grade III spondylolisthesis at L-5. Preoperatively, the gait pattern was characterized by posterior pelvic tilt, decreased hip flexion, increased knee flexion, and decreased stride length and walking speed. All temporal and kinematic parameters of gait normalized after laminectomy and instrumented, in situ arthrodesis (L-4-S-1). The absence of any neurologic abnormalities on preoperative imaging, intraoperative somatosensory-evoked potentials (SSEP) monitoring, and nerve-root exploration, together with the observed improvement after stabilization of the spinopelvic junction, suggests a mechanical basis for the gait changes in high-grade spondylolisthesis.

Child↗