Abstract
To evaluate the usefulness of two IS6110 based typing methods, an amplityping assay and restriction fragment length polymorphism (RFLP) analysis, for fingerprinting respiratory isolates of Mycobacterium tuberculosis. For amplityping, a pair of primers which amplify the intervening sequence between the repetitive insertion sequence IS6110 was used to generate a banding pattern which was confirmed by hybridisation. This assay was compared with conventional chromosomal DNA RFLP typing in the evaluation of 110 epidemiologically diverse isolates. Polymerase chain reaction (PCR) amplityping generated a single pattern in Hong Kong Chinese strains, but two and four diverse patterns in Filipino and Vietnamese strains, respectively, and could be completed within four days. When compared with chromosomal DNA RFLP typing, which took three weeks to complete, four different RFLP patterns could be seen among the Chinese strains, while seven patterns were found in the Filipino and Vietnamese strains. No change in amplityping or RFLP patterns was found in 36 sequential isolates from the same patients after anti-tuberculosis treatment for up to 12 months, despite the emergence of resistance in three of these strains. No specific amplityping or RFLP pattern could be related to different patterns of drug susceptibility. PCR amplityping could be used initially as a rapid typing method to distinguish strains originating from different localities. This could be important for investigation of outbreaks of tuberculosis--for example, in refugee camps.
Highlights
Despite improving nutrition, a good BCG vaccination programme and the availability of several effective antimicrobial agents against M tuberculosis, tuberculosis remains a significant cause of morbidity and mortality in Hong Kong
6000 cases in 1993, the incidence of tuber- Four restriction fragment length polymorphism (RFLP) patterns were observed in the culosis in Hong Kong, which is 100 cases per 80 Chinese strains and the number of copies
There was no correlation between is quite unexpected in Hong Kong because the RFLP pattern and antimicrobial susit has provided a comprehensive supervised ceptibility
Summary
As part ofa follow up study ofpatients admitted to a chest hospital for treatment of pulmonary tuberculosis,'[8 110] strains of M tuberculosis isolated over a three year period from 92 patients were selected for this study (table). Group 1A were Hong Kong residents who were born in diverse geographical regions outside Hong Kong from whom strains of M tuberculosis were isolated sequentially. These strains were sensitive to all first line anti-tuberculosis agents. Patients in group 1B were similar to those in group 1 A except that the isolates were resistant to one or more anti-tuberculosis agents. Group 2A were patients who resided in Hong Kong since birth and their isolates were sensitive to all first line anti-tuberculosis agents. Group 2B, natives of Hong Kong, had a diverse antimicrobial susceptibility pattern which included strains resistant to two to seven drugs, including isoniazid, streptomycin, rifampicin, ethambutol, ofloxacin, kanamycin, and pyrazinamide. Group 3 patients were Filipino housemaids working in Hong Kong, while
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