Comparison of the E test and a proportion dilution method for susceptibility testing of Mycobacterium avium complex

WR99210, a dihydrofolate reductase inhibitor, has promising in vitro activity against Mycobacterium avium complex (MAC). The in vitro activities of WR99210 alone and in combination with a fixed concentration of dapsone (0.5 microgram/ml) were evaluated against 35 clinical MAC isolates by a broth dilution method. The MIC at which 50% of isolates were inhibited (MIC50) and MIC90 of WR99210 alone were 2 and 8 micrograms/ml, respectively. The MIC50 and MIC90 of WR99210 in combination with dapsone were 0.25 and 4 micrograms/ml, respectively. Overall, 75% of the MAC isolates displayed enhanced susceptibility to the combination.

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Controversies in the Management of Mycobacterium Avium Complex Infection in AIDS Patients

Annals of Pharmacotherapy ◽

10.1177/106002809302700722 ◽

1993 ◽

Vol 27 (7-8) ◽

pp. 928-937 ◽

Cited By ~ 10

Author(s):

Charles A. Peloquin

Keyword(s):

Mouse Models ◽

Mycobacterium Avium ◽

Mycobacterium Avium Complex ◽

Susceptibility Testing ◽

Traditional Approach ◽

Clinical Manifestations ◽

Future Research ◽

General Description ◽

Aids Patients

OBJECTIVE: To update readers on the clinical management of infections secondary to Mycobacterium avium complex (MAC) in patients with AIDS. A general description of the organism, culture and susceptibility testing, and clinical manifestations of the disease is provided. Several aspects of the treatment of the disease, including an historical perspective, current approaches, and future research opportunities, are described. DATA SOURCES: Current medical literature, including abstracts presented at international meetings, is reviewed. References were identified through MEDLINE, Current Contents, and published meeting abstracts. STUDY SELECTION: Data regarding the epidemiology, clinical manifestations, culture and susceptibility testing, and treatment of MAC are cited. Specific attention is given to the management of patients with MAC infection. DATA EXTRACTION: Information contributing to the discussion of the topics selected by the author is reviewed. Data supporting and disputing specific conclusions are presented. DATA SYNTHESIS: Disseminated MAC infection is diagnosed antemortem in approximately 30 percent of patients with AIDS; postmortem rates of isolation exceed 50 percent. The incidence of MAC may increase as attempts at isolating the organism become more aggressive. The traditional approach to the isolation, susceptibility testing, and treatment of MAC has been derived from the management of Mycobacterium tuberculosis, with disappointing results. Newer radiometric in vitro methods of susceptibility testing appear to show more promise. Current mouse models of MAC are not true AIDS models; new CD4-deficient mouse models are being developed. Clinical mycobacteriologic and pharmacokinetic laboratory support have been underused, with treatment generally proceeding empirically. New agents that may contribute to the management of disseminated MAC infection include the macrolide derivatives clarithromycin and azithromycin. Research also continues with new rifamycins (including rifabutin) and fluoroquinolones (ciprofloxacin, sparfloxacin). Preliminary results suggest a central role for macrolides in the treatment of disseminated MAC; effective companion drugs are needed to prevent the rapid emergence of macrolide-resistant MAC. CONCLUSIONS: Treatment results for disseminated MAC infection remain poor. Therapy may be improved by selecting drugs on the basis of susceptibility data for each isolate, rather than by using empiric regimens based on susceptibility trends. Significant antimycobacterial drug malabsorption has been documented, and may contribute to poor outcomes. More-potent agents are needed to improve the clinical outcome in AIDS patients with MAC.

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Evaluation of a New Method for Rapid Drug Susceptibility Testing of Mycobacterium avium Complex Isolates by Using the Mycobacteria Growth Indicator Tube

Journal of Clinical Microbiology ◽

10.1128/jcm.36.1.64-67.1998 ◽

1998 ◽

Vol 36 (1) ◽

pp. 64-67 ◽

Cited By ~ 10

Author(s):

Claudio Piersimoni ◽

Domenico Nista ◽

Stefano Bornigia ◽

Giuseppina De Sio

Keyword(s):

Mycobacterium Avium ◽

Mycobacterium Avium Complex ◽

Susceptibility Testing ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

New Method ◽

Indicator Tube ◽

Broth Macrodilution ◽

Bactec System ◽

Growth Indicator

The reliability of the Mycobacteria Growth Indicator Tube (MGIT [BBL]) for rapid drug susceptibility testing of Mycobacterium avium complex (MAC) isolates was evaluated. MICs of amikacin, clarithromycin, clofazimine, ethambutol, and rifabutin were determined by the MGIT system for 16 MAC strains. The results were compared with those obtained by the BACTEC broth macrodilution method. The turnaround times were 6 to 8 days (median, 7 days) for the MGIT and 5 to 7 days (median, 6 days) for the BACTEC system. Agreements with BACTEC system-determined MICs, within ±1 log2 dilution, were 100, 100, 88, 63, and 44% for amikacin, clofazimine, rifabutin, clarithromycin, and ethambutol, respectively. Within ±2 log2 dilutions, agreement with BACTEC system-determined MICs increased to 100% for all the tested drugs. In addition, if MGIT-determined MICs were evaluated according to the thresholds adopted for the interpretation of BACTEC system-determined ones, ethambutol was the only drug for which susceptible strains were frequently misclassified as resistant. It is concluded that the MGIT system is a promising, nonradiometric alternative to the BACTEC method for rapid susceptibility testing of MAC isolates; however, additional studies are required to confirm our results and to determine the optimal criteria for the interpretation of ethambutol MICs.

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