Culture-independent prediction of isoniazid resistance in Mycobacterium tuberculosis by katG gene analysis directly from sputum samples.
BACKGROUND
The molecular prediction of isoniazid (INH) resistance in Mycobacterium tuberculosis is hampered by the need for specialized equipment, expertise, high costs, a limited range of detectable mutations, or several of these factors. The rationale for the study was to find a practical alternative and to demonstrate generally valid problems.


RESULTS
DNA extracted from decontaminated sputum pellets was used to amplify a 0.26 kb target sequence within the katG gene. Mutations of codon 315, frequently found in isoniazid-resistant isolates, could be discriminated in a simple agarose minigel format following an AciI digest of the nested polymerase chain reaction (PCR) product. Within a panel of 22 sputum samples, INH resistance could be predicted in 5 of 10 samples containing isoniazid-resistant M. tuberculosis. The protocol is robust, requires little expertise and no specialized equipment, and provides the test results within 2 days.


CONCLUSIONS
The results show the feasibility to rapidly and easily detect mutations highly predictive of isoniazid resistance. Nevertheless, this, like any other molecular resistance prediction test, is affected by often neglected factors, including mutation prevalences, the phenomenon of heteroresistance, and a possible bias toward one's own method.
Rinder
H
H
Department of Infectious Diseases and Tropical Medicine, Klinikum Innenstadt, University of Munich, Munich, Germany.
Feldmann
K
K
Tortoli
E
E
Grosset
J
J
Casal
M
M
Richter
E
E
Rifai
M
M
Jarlier
V
V
Vaquero
M
M
Rüsch-Gerdes
S
S
Cambau
E
E
Gutierrez
J
J
Löscher
T
T
D000995:Antitubercular Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001426:Bacterial Proteins; D004352:Drug Resistance, Microbial / Q000235:genetics*; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology* / Q000627:therapeutic use; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics*; D010544:Peroxidases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D013183:Sputum / Q000382:microbiology*; D014376:Tuberculosis / Q000188:drug therapy / Q000382:microbiology*
D000995:Antitubercular Agents; D001426:Bacterial Proteins; D010544:Peroxidases; C076136:catalase HPI; D007538:Isoniazid