Evidence of transmission of tuberculosis by DNA fingerprinting.

OBJECTIVE: To determine whether a subject who had died of tuberculous meningitis had been infected by a neighbour. DESIGN: Retrospective comparison of isolates of Mycobacterium tuberculosis from the two cases and from 10 controls by DNA fingerprinting. SETTING: Public Health Service Reference Laboratory for Mycobacteria and bacterial molecular genetics unit of the London School of Hygiene and Tropical Medicine. SUBJECTS: Deceased and neighbour; 10 controls from the same city, from whom isolates had been collected over three months before the subject's death. MAIN OUTCOME MEASURES: Identity and similarity values (SAB) between fingerprint patterns from different isolates obtained by hybridisation of restriction fragments produced by PvuII with a probe from the insertion element IS6110/986, present in multiple copies throughout the genome of M tuberculosis. RESULTS: Isolates from the two cases under investigation had identical fingerprints whereas those from the controls were all distinct. Two clusters of isolates with a similarity coefficient > 0.25 were identified: in one, four out of five patients were born in the midlands (the birth place of the fifth was not known) and in the other all three patients were born in the Indian subcontinent. CONCLUSIONS: The data are consistent with, but do not prove, transmission of tuberculosis from the neighbour to the deceased. Geographical separation of the pools of infection may have led to the evolution of distinct clusters of fingerprint patterns. DNA fingerprinting of M tuberculosis is a powerful new tool for study of the epidemiology and pathogenesis of tuberculosis.

Rubella antibody measured by radial haemolysis. Characteristics and performance of a simple screening method for use in diagnostic laboratories.

A simple method for preparing radial haemolysis gels for rubella antibody screening is described. In use it gave clear zones of haemolysis when a standard serum was tested at dilutions down to 5.6 i.u./ml rubella antibody. In five laboratories 8404 sera were screened by the method and the results were read by comparing zones of haemolysis with that of a standard serum diluted to contain 15 i.u/ml antibody. A zone greater than or equal to 15 i.u./ml, indicating immunity, was given by 7433 (88.4%) of the sera. No zone indicating susceptibility was seen with 748 (8.9%) sera. Small zones, less than 15 i.u./ml standard, were given by 189 (2.2%) sera, and in only 34 cases (0.4%) did non-specific haemolysis interfere with the test readings. Further testing of the radial haemolysis interfere with the test readings. Further testing of the radial haemolysis negative and low positive sera by the haemagglutination inhibition test gave rise to some discrepant results which are discussed.

An assessment of radial haemolysis in the detection of rubella antibody.

The results obtained by radial haemolysis in the detection of antibodies to rubella virus compared well with those obtained by haemagglutination inhibition. Radial haemolysis is unaffected by non-specific inhibitors. The sera do not therefore require pretreatment and the results are less equivocal. Radial haemolysis appears to be as sensitive as immunofluorescence and floatation centrifugation. It is possible to examine large numbers of sera with a considerable saving of time compared with the traditional haemagglutination technique. Rheumatoid factor may cause interference in radial haemolysis. Immune sera may be recorded as non-immune. This interference can be removed by 2-mercaptoethanol or reduced by heating sera at 60 degrees C for 20 minutes.

Ampicillin levels in human bile in the presence of biliary tract disease.

Ampicillin levels were measured in the serum and in the bile from both the gall bladder and the common bile duct in patients undergoing surgery for biliary tract diseases. In patients with radiologically non-functioning gall bladders ampicillin was either not present or its concentration was lower than normal. Therapeutic levels were present in the common bile duct of all patients except those with obstruction of the common bile duct. Hence ampicillin fails appreciably to penetrate the obstructed viscus in obstructive biliary tract disease, and it is unlikely to be effective in treating infection associated with this.