Giardia intestinalis antigens expressed in Escherichia coli.

cDNA and genomic DNA of Giardia intestinalis have been cloned in pUC vectors and used to express Giardia antigens in Escherichia coli. Several expression libraries have been produced and positive clones identified by immuno-colony assays with antisera raised against whole parasites and partially purified antigen(s). Those clones which express G. intestinalis antigens have been used to raise antisera in mice and the antisera used in immunofluorescence assays. The proteins expressed by the clones have been shown to represent a 32 kDa protein of the flagellae and axonemes, a protein associated with the spiral part of the ventral disc, proteins covering the surface of the trophozoite or associated with the coat, and other proteins associated with axonemes of posterolateral flagellae, kinetosomes and funis, and the anterolateral axonemes. mRNA was purified from G. intestinalis and translated in a cell free lysate. A rabbit antiserum raised against trophozoites immunoprecipitated several translation products while an antiserum raised against a purified 32 kDa protein only immunoprecipitated this protein. G. intestinalis rRNA subunits also were examined in the course of mRNA purification. Two rRNA species were evident, the small rRNA and the post-transcriptionally processed large rRNA.

Similarities of Giardia antigens derived from human and animal sources.

A total of 37 Giardia stocks isolated from humans and 14 stocks derived from animal sources have been analysed for antigenic differences. Separation of the proteins of the stocks by polyacrylamide gel electrophoresis showed no major differences among the stocks. Immunoblotting of these antigens demonstrated some minor differences which were not correlated with geographic location, allozyme type, virulence or any other distinguishing characteristic of the stocks. Immunofluorescence tests using monoclonal antibodies revealed some differences between stocks but the monoclonal antibodies did not significantly inhibit growth in inhibition assays.

Acute effects of low levels of ambient ozone on peak expiratory flow rate in a cohort of Australian children.

BACKGROUND: We enrolled a cohort of primary schoolchildren with a history of wheeze (n = 148) in an 11-month longitudinal study to examine the relationship between ambient ozone concentrations and peak expiratory flow rate. METHODS: Enrolled children recorded peak expiratory flow rates (PEFR) twice daily. We obtained air pollution, meteorological and pollen data. In all, 125 children remained in the final analysis. RESULTS: We found a significant negative association between daily mean deviation in PEFR and same-day mean daytime ozone concentration (beta-coefficient = 0.88; P = 0.04) after adjusting for co-pollutants, time trend, meteorological variables, pollen count and ALTERNARIA: count. The association was stronger in a subgroup of children with bronchial hyperreactivity and a doctor diagnosis of asthma (beta-coefficient = -2.61; P = 0.001). There was no significant association between PEFR and same-day daily daytime maximum ozone concentration. We also demonstrated a dose-response relationship with mean daytime ozone concentration. CONCLUSIONS: Moderate levels of ambient ozone have an adverse health effect on children with a history of wheezing, and this effect is larger in children with bronchial hyperreactivity and a doctor diagnosis of asthma.

The epidemiology of tuberculosis in New South Wales 1975-1995: the effects of immigration in a low prevalence population.

SETTING: New South Wales (NSW) is Australia's most populous state and is home to one third of the country's rapidly growing immigrant population. OBJECTIVE: To examine the effects of immigration upon the epidemiology of tuberculosis (TB) in a low prevalence population. DESIGN: A retrospective review of state TB surveillance data in NSW from 1975-1995. RESULTS: The crude notification rate for all active TB declined from 12.2 per 100000 population in 1975 to 5.2/100000 in 1986, after which the notification rate increased steadily to 7.6/100000 in 1995. Between 1975 and 1995, the proportion of all TB notifications occurring in overseas-born residents increased from 30% (178/601) to 79% (345/435). During this period, the proportion of new extra-pulmonary TB notifications increased from 13% (72/549) to 42% (171/405). Notifications amongst women increased from 31% (188/601) to 47% (218/462) of the total, while the median age at notification fell from 55 to 41 years. The pattern of TB disease has not changed for Australian-born cases, who are mostly elderly men with pulmonary disease. Multidrug-resistant TB remains uncommon (<1%), and co-infection with the human immunodeficiency virus (HIV) and TB has not emerged as a major problem (2% of notifications), but is poorly documented. CONCLUSION: TB has re-emerged in NSW predominantly because of increased immigration from high prevalence countries. The epidemiology of TB has become dominated by overseas-born notifications, and now younger adults are primarily affected. Enhancing the effectiveness of the TB screening procedures for immigrants is a priority. Information should be provided to all immigrants and to long-term visitors from countries of high TB prevalence regarding TB infection and the TB services available in Australia.

Environmental investigation of a legionellosis outbreak in western Sydney: the role of molecular profiling.

This investigation used DNA profiling in an attempt to identify the environmental source of a community outbreak of 11 cases of Legionnaires' disease. Nine of these cases were culture positive and a single strain (DNA profile) of Legionella pneumophila serogroup 1 was isolated from eight cases. Spot water samples were collected from 51 cooling towers implicated by case exposure histories; this same strain was isolated from four towers at three separate locations up to 6 km apart. None of these locations had been frequently implicated by case histories. Because we did not perform an analytic epidemiological investigation, we were unable to identify a single environmental source for the outbreak. It is also possible that this outbreak was multifocal. The use of molecular profiling should not overshadow the importance of epidemiological methods in these environmental investigations. More data is needed regarding the prevalence, distribution, and clinical significance (virulence) of environmental L. pneumophila strains. This would aid interpretation of molecular profiling used in investigations of community legionellosis outbreaks.

Communicable disease outbreaks in long day care centres in western Sydney: occurrence and risk factors.

We surveyed the directors of all 92 long day care centres in western Sydney to document the occurrence of communicable disease outbreaks during 1992 and to identify risk factors for the occurrence of these outbreaks. A total of 6092 children were enrolled at the centres, of whom 530 (8.7%) were less than 3 years old. Most centres (80.4%) reported at least one outbreak of communicable disease. Diarrhoea was the most commonly reported outbreak type (60 outbreaks), followed by conjunctivitis, head louse infestation and chicken pox (46, 44 and 24 outbreaks, respectively). Chicken pox outbreaks had the largest mean number of cases per outbreak (9.6) and the longest mean outbreak duration (4.4 weeks). Centres with a large total enrollment (50 or more children), those that were open for 12 or more hours each day and those which had commenced operating in 1990 or more recently were generally more likely to report outbreaks, particularly of diarrhoea. The vast majority of communicable disease outbreaks (92.1%) were handled by day-care staff without seeking outside assistance. Day-care centre directors may be unaware of the health services that could help them. We need to work more closely with long day care centres, and to focus preventative efforts on large centres, those open for long hours, and newly opened centres.

Seroprevalence of hepatitis A antibodies among residents of a centre for people with developmental disabilities.

BACKGROUND: In February 1993, 11 cases of hepatitis A virus (HAV) were identified in permanent residents of a centre for young people with developmental disabilities. AIMS: To define the extent of the outbreak in the centre, to determine the seroprevalence of hepatitis A antibodies (anti-HAV) in permanent residents, and to ascertain risk factors for serological evidence of HAV infection. METHODS: A cross-sectional serological survey of 270 permanent residents, aged eight to 40 years, in a centre for people with developmental disabilities, was conducted in western Sydney. Using a radioimmunoassay technique, sera were tested for anti-HAV (IgM and total antibody). We used logistic regression to determine risk factors for presence of anti-HAV. RESULTS: Blood samples were collected from 259 permanent residents (96%). Serological testing revealed anti-HAV in 128 residents tested (49%). Presence of anti-HAV was associated with living in specific residential units, and with residents' age and length of stay at the centre, but was not associated with reported behavioural factors. CONCLUSIONS: More than half of the residents of the centre were susceptible to HAV infection. Behavioural characteristics of the residents and their close contact with each other make HAV transmission difficult to control. HAV vaccine should be promoted in communities at risk, such as those with developmental disabilities.

Tetanus immunity in an older Australian population.

OBJECTIVE: To evaluate the effectiveness in older Australians of the current tetanus vaccination program. DESIGN: A cross-sectional survey of tetanus immunity (enzyme immunoassay of serum samples) in an older population in New South Wales. Self-reported history of tetanus vaccination was compared with serologically measured immunity. PARTICIPANTS: 430 randomly selected adults, 49 years of age and older, from the Blue Mountains Eye Study population. RESULTS: Fifty-two per cent (95% confidence interval [CI], 47%-57%) of adults 49 years of age and older had protective levels of tetanus antitoxin ( > 0.15 IU/mL). There was a significant decline in the prevalence of immunity with increasing age (chi 2 for linear trend, P = 0.036), and women were less likely to be immune regardless of their age (Mantel-Haenszel weighted odds ratio, 0.65; CI, 0.43-0.92). Thirty-five per cent (95% CI, 31%-40%) of all participants reported that they had been vaccinated in the preceding 10 years. Although self-reported tetanus vaccination history was associated with tetanus immunity, it was neither sensitive nor specific as a test for immunity. CONCLUSIONS: About half the adults 49 years of age and older in the Blue Mountains area of New South Wales do not have protective levels of tetanus antitoxin because of inadequate vaccination coverage in this age group. Vaccination history is not a reliable indicator of tetanus immunity and a system is needed for accurate recording of adult vaccination.

The epidemiology of incomplete childhood immunization: an analysis of reported immunization status in outer western Sydney.

We surveyed parents of children enrolled in kindergarten in 1992 in outer western Sydney and the Blue Mountains. Using parents' reports, we determined the prevalence of immunization uptake for children starting school, compared the prevalence of immunization uptake among Catholic, government and independent schools, and identified immunization providers. We also documented parental beliefs about immunization and their influence on immunization status, and identified risk factors for incomplete immunization. Nearly 89% of children were reported to be fully immunized. Immunization status did not vary significantly among the different types of school. General practitioners provided 84% of all immunizations and local councils 11%. Incomplete immunization was associated with more negative beliefs in immunization, with post-secondary education and with families who do not speak English at home. Reminder letters had little effect on immunization status.

Detection of Chlamydia trachomatis in urine using enzyme immunoassay and DNA amplification.

The suitability of urine specimens for the detection of Chlamydia trachomatis infections in men was assessed. Urethral swabs from 301 patients were cultured for C. trachomatis, and the results were compared with results obtained from Chlamydiazyme. The results of 298 specimens were also compared with results obtained from PCR analysis of first-void urine specimens. The sensitivity of confirmed Chlamydiazyme analysis was 93% and the specificity was greater than 99% compared with culture. The sensitivity of the PCR method was 100% compared with culture. Chlamydia trachomatis was detected by PCR in an additional three specimens from which C. trachomatis could not be cultured. Urine appears to be an appropriate specimen for the detection of C. trachomatis antigens and nucleic acids.

Invasive Haemophilus influenzae type b disease in elderly nursing home residents: two related cases.

We investigated two fatal cases of invasive Haemophilus influenzae type b (Hib) infection in a community nursing home in western Sydney, Australia. Two elderly women had lived in the same room, and the onset of their illness was 5 days apart. Hib isolates from blood cultures showed identical profiles by pulsed field gel electrophoresis. These findings suggest that Hib infection was transmitted within this nursing home. Serious Hib disease may be underrecognized in this setting. Continued surveillance and serotyping of invasive H. influenzae disease is essential for identifying groups at increasing risk that may benefit from immunization against Hib.

Legionellosis linked with a hotel car park--how many were infected?

An outbreak of legionellosis associated with a hotel in Sydney, Australia, and the subsequent epidemiological and environmental investigations are described. Four cases of Legionnaires' disease were notified to the Public Health Unit. A cross-sectional study of 184 people who attended a seminar at the hotel was carried out. Serological and questionnaire data were obtained for 152 (83%) of these. Twenty-eight (18%) respondents reported symptoms compatible with legionellosis. Thirty-three subjects (22%) had indirect fluorescent antibody (IFA) titres to Legionella pneumophila serogroup 1 (Lp-1) of 128 or higher. The only site which those with symptoms of legionellosis and IFA titre > or = 128 were more likely to have visited than controls was the hotel car park (adjusted odds ratio [OR] 14.7, 95% confidence interval [CI]: 1.8-123.1). Those with symptoms compatible with legionellosis, but whose IFA titres were < 128 were also more likely to have visited the hotel car park (adjusted OR 4.4, 95% CI: 1.5-12.9). Seroprevalence of Lp-1 antibodies was higher in those who attended the seminar than in a population sample of similar age. Findings suggested that the 4 cases represented a small fraction of all those infected, and highlighted difficulties in defining illness caused by Lp-1 and in interpreting serology.