Blood Agar Validation for Susceptibility Testing of Isoniazid, Rifampicin, Ethambutol, and Streptomycin to Mycobacterium tuberculosis Isolates

Abstract

In recent studies, it was shown that blood agar can be used at least as effectively as Löwenstein-Jensen medium for growing Mycobacterium tuberculosis. It was also shown that susceptibility testing can be performed on blood agar. Additional validation of blood agar was performed on regional M. tuberculosis isolates from Turkey to determine critical concentrations of isoniazid (INH), rifampicin (RIF), ethambutol (ETM), and streptomycin (STR). In the current study, 40 M. tuberculosis clinical isolates were tested. H37Rv, which is susceptible to all antituberculosis agents, ATCC 35822 (INH-resistant), ATCC 35838 (RIF-resistant), ATCC 35837 (ETM-resistant), and ATCC 35820 (STR-resistant) quality control strains were used as control strains. Proportion method on 7H11 agar was considered as gold standard in the study. MIC values of the control strains and clinical isolates were detected on blood and 7H11 agar. Categorical agreements were 100% for each antibiotic, and essential agreements were 100%, 97.5%, 82.5%, and 95% for INH, RIF, ETM, and STR, respectively. According to the data, 0.2 µg/mL for INH, 1 µg/mL for RIF, 4 µg/mL for ETM, and 2 µg/mL for STR were appropriate breakpoint values for susceptibility testing on blood agar. Blood agar may be recommended for use in both developed and developing countries for the susceptibility testing of M. tuberculosis isolates to primary antituberculosis drugs.

Screening of the antimycobacterial activity of novel lipophilic agents by the modified broth based method

“…Although antitubercular DSTs are carried out mainly using the standard proportional method on L–J medium and Middlebrook 7H10 agar, they have many disadvantages. In addition to the inactivation of heat-labile drugs [8], [10], reduction of drug activity can occur because of (a) binding of the drug to the agar (agar-based mediums), or proteins and phosphate of egg (egg-based mediums) [10], [11], [19], [20]; (b) prolonged incubation time, which potentially reduces the potency of certain antimicrobials; and (c) less contact of organisms with appropriate concentrations of antimycobacterial substances on solid media [8], [9]. Although, the two lipophilic compounds (derivative of dihydropyridines) tested in this study have relative heat stability, the above-mentioned disadvantages of L–J medium (all or in part) might explain their inactivation in the standard method.…”

Simple and low‐cost antibiotic susceptibility testing for Mycobacterium tuberculosis using screen‐printed electrodes

“…In the literature, Coban et al reported the susceptibility of the bacteria to Isoniazid, rifampicin, ethambutol, and streptomycin antibiotics using Blood Agar Validation for TB. 11 Hall et al presented an AST of resistant TB using microtiter assay. 12 These methods are quite safe, however; the main limitations are low sensitivity, complex sample preparations, lack of automation, and growth dependence.…”

“…In the literature, Coban et al. reported the susceptibility of the bacteria to Isoniazid, rifampicin, ethambutol, and streptomycin antibiotics using Blood Agar Validation for TB 11 . Hall et al.…”

A fully integrated rapid on-chip antibiotic susceptibility test – A case study for Mycobacterium smegmatis

“…Antimicrobial susceptibility tests (ASTs) are mainly examined by traditional methods like disk diffusion, dilution (agar and broth) and E-test. In the literature, Coban et al reported the susceptibility of the bacteria to Isoniazid, rifampicin, ethambutol, and streptomycin antibiotics using Blood Agar Validation for MTB [11]. Hall et al, presented an antimicrobial susceptibility test of resistant MTB using microtiter assay [12].…”