Prevalence of Mycobacterium tuberculosis drug resistance in a Spanish teaching hospital during a six-year period

Abstract number: P594

Agudo S., Domingo D., Moreno M.J., Martínez M.C., López-Brea M.

Objective: An increase in Mycobacterium tuberculosis drug resistance has been registered in the last few years in industrialised parts of the world. Rapid detection of M. tuberculosis strains resistant to antituberculosis drugs is probably the most important factor to minimise the spread of contagion. The aim of this study is to evaluate the drug resistance of culture positive cases of pulmonary and extra-pulmonary tuberculosis during a six year period in a Spanish teaching hospital.

Methods: 343 strains of Mycobacterium tuberculosis were obtained from samples, received at the Microbiology Department (Hospital Universitario de la Princesa, Madrid) from January 2003 to December 2008.

Samples were collected by standard procedures. They were examined by auramine stain and inoculated on Lowenstein Jensen (LJ) media and BACTEC MGIT 960 system.

All of the strains were identified as belonging to M. tuberculosis Complex by combining DNA-probe hybridisation (AccuProbe M. tuberculosis; Gen-Probe, San Diego, Calif). In vitro drug susceptibility tests against the first line drugs (Isoniazid, Streptomycin, Rifampicin, Ethambutol and Pyrazinamide) were performed by BACTEC MGIT 960 SIRE and PZA (Becton Dickinson).

Results: A total of 77.56% strains were susceptible to the five first line essential drugs. Drug resistance rates of 7.28% was detected against isoniazid, 10.20% against Streptomycin, 2.33% against Rifampicin, 0.96% against Ethambutol and 2.88% to Pyrazinamide. Multidrug resistance (MDR: Resistance to both isoniazid and Rifampicin) was seen in 8 (2.43%) of the isolates. 3 (0.87%) isolates were found to be resistant to all drugs tested. 3 out of 8 MDR M. tuberculosis isolates were from patients who had immigrated to Spain and only one patient was infected by the human immunodeficiency virus. The resistance to both Isoniazid and Rifampicin decreased from 3.77% in the period of 2003–2004 to 2.35% 2007–2008.

Conclusion: Ethambutol and Streptomycin were the most and the less active drugs, respectively. According to our work, resistance to Isoniazid and Rifampicin is low in our area, specially in the last years. All reasonable efforts to prevent the spread of MDR tuberculosis must be made and maintained. It requires an efficiently working anti-tuberculosis programme to prevent resistance.