Confirmation of invasive meningococcal disease by single point estimation of IgM antibody to outer membrane protein of Neisseria meningitidis.

OBJECTIVES: The sensitivity of laboratory confirmation of invasive meningococcal disease (IMD) by culture or PCR is affected by prior antibiotic treatment and decreasing use of early lumbar puncture. Serological diagnosis of IMD is not widely used because of reliance on paired serum samples. The application of single point estimations of IgM antibodies in the diagnosis of IMD was explored. DESIGN: Outer membrane proteins from a mix of commonly encountered meningococcal serotypes were partially purified and used as an antigen in an enzyme immunoassay for the detection of IgM antibody. The cut-off for the assay was derived using sera from blood bank donors and the accuracy then evaluated with sera from patients with culture-confirmed IMD, other bacterial infections and culture-proven nasopharyngeal colonisation with Neisseria meningitidis. RESULTS: The coefficient of variability of the assay was < 10% in negative, mid- and high-range positive sera and the specificity of the assay was at least 93%. In sera collected from 49 adult patients at various times after positive blood or CSF culture-confirmed IMD, the assay had a sensitivity of 100% in specimens collected between 5 and 18 days. At the time of isolation of meningococci from either blood or CSF, eight of 29 sera were IgM-positive, but beyond 70 days no positive results were detected. No differences were seen in the IgM responses in patients from whom different serogroups of N. meningitidis were recovered. CONCLUSIONS: Serological examination by single point IgM enzyme immunoassay (EIA) offers the possibility of an expanded laboratory confirmation of IMD in adults for samples taken between 5 and 18 days after onset.

A serological re-evaluation of acute non-A non-B hepatitis from the early 1970s.

BACKGROUND: The epidemiology and natural history of recently discovered viruses, which may be responsible for cases of seronegative infectious hepatitis, are currently being investigated. Retrospective studies of stored sera can provide a historical perspective of these infections. AIMS: To re-evaluate the serological, demographic and clinical characteristics of patients hospitalised in the early 1970s with acute hepatitis. METHODS: The stored sera of 57 patients hospitalised between 1971 and 1974 with acute hepatitis, designated at that time as non-A non-B (NANB) hepatitis, were re-tested using commercially available enzyme-linked immunosorbent assays (ELISAs) for the presence of anti-hepatitis A virus (HAV) IgM, hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (HCV) IgG, and anti-hepatitis E virus (HEV) IgG. Stored sera from a group of 57 patients concurrently hospitalised for other conditions were also tested. Detailed records of the original epidemiological interviews were examined to compare patient demographics, risk factors for infectious hepatitis and clinical data for the NANB hepatitis group and an original control group of 604 hospitalised patients. RESULTS: Serum from 15 of the 57 (26%) previously designated NANB hepatitis cases had elevated anti-HAV IgM and are likely to represent missed cases of hepatitis A. Thirteen (23%) of cases previously designated as NANB hepatitis had positive hepatitis C antibody tests. These patients were younger and significantly more likely to have used intravenous drugs than control patients. Three NANB hepatitis and two hospital control patients were anti-HEV IgG antibody positive. All of these individuals were born in, or had travelled to, developing countries. Serum from 27 (47%) of the NANB hepatitis patients were negative on all tests. These hepatitis non-A-E cases included children and elderly adults, but as a group were significantly more likely to have used intravenous drugs than hospitalised control patients. CONCLUSION: Both HCV and probable non-A-E virus(es) were important causes of acute NANB hepatitis during the early 1970s.

Unusual cluster of mild invasive serogroup C meningococcal infection in a university college.

The objective of this study was to describe the epidemiology and public health response to an apparent cluster of Neisseria meningitidis serogroup C infection in university students in a residential college. A conventional epidemiological approach was taken, supported by routine and novel diagnostic techniques. Over the two days of 21-22 August 1997, three cases of suspected meningococcal infection were notified from a residential college complex at a university campus in the Sydney metropolitan area. Neisseria meningitidis was grown from throat swabs of all three cases, and was isolated from the blood of one case only. All three isolates were typed as C:2a:P1.5,2. Seroconversion was demonstrated by a novel method in the three cases. Rifampicin was given to all identified contacts. Forty-seven days after the index case, a 19 year old female living in the same complex was diagnosed with bacterial meningitis, and identified contacts given rifampicin. When this isolate was found to be group C, it was decided to vaccinate residents of the college complex. Genotyping and serotyping (C:2a:P1.5) later revealed the fourth isolate to be distinct from isolates from Cases 1-3. In conclusion the authors note that Australia's increasing capacity to type meningococcal strains is essential to understanding the epidemiology of this disease. Furthermore, typing information is of critical importance when decisions are made regarding mass vaccination. As early antibiotic treatment may inhibit isolation of the organism, development of novel approaches to diagnosis and typing should be supported.