Drug susceptibility testing of Mycobacterium tuberculosis strains by using two different methods

Abstract number: R2318

Aktas A.E., Igan H., Ayyildiz A.

Objective: The emergence of multi-drug-resistant tuberculosis points out how important timely identification of Mycobacterium tuberculosis complex strains and their susceptibility testing may be to achieving effective management of the disease and prevention of its spreading. Currently, a number of susceptibility testing methods have been used in many laboratories. In the present study we aimed to compare the agar proportion method with the E-test method for susceptibility testing of Mycobacterium tuberculosis strains isolated from the patients in our hospital.

Methods: A total of 45 isolates were tested for isoniazid, rifampin, streptomycin and ethambutol susceptibility using an indirect-proportion method and E-test method. The isolated strains were identified by morphological, cultural and biochemical characteristics (microscopy, time of growth, type of colonies, catalase, niacin-test). H37RV strain was incuded in the test as reference strain. The E-test method was performed on 7H11 agar with OADC, and the standard proportion method was performed on Lowenstein-Jensen agar. E-test method gave correct results from the eighth day, with stability of the zone of inhibition until the 21st day.

Results: We found a good correlation between the two methods. The correlations between the Etest and agar proportion methods were 98, 100, 100, and 100% for isoniazid, rifampin, ethambutol, and streptomycin, respectively. The results are summarised in Table 1.

Table 1. Comparison of susceptible and resistant M. tuberculosis strains by the E-test and agar proportion methods

Conclusion: Our results showed that there were no statistically significant differences in susceptibility testing results between E-test and the proportion method. The results thus suggest that E-test method can be routinely used instead of the proportion method because the average times required for obtaining the final result with E-test method are less than the proportion method.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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