Fitness of Drug Resistant Mycobacterium tuberculosis and the Impact on the Transmission among Household Contacts

MORCILLO, NORA; IMPERIALE, BELÉN; DI GIULIO, BEATRIZ; ZUMÁRRAGA, MARTÍN JOSÉ; CATALDI, ANGEL

Tuberculosis (Edinb)

CHURCHILL LIVINGSTONE

Lugar: ESCOCIA; Año: 2014

1472-9792

The aim of this study is to explore the relationship between mutations related to drug-resistant Mycobacterium tuberculosis and the fitness of the isolates as a transmission measure. Patients? clinical and epidemiological data, drug-susceptibility, and genetic patterns of the isolates were collected. Multidrug-resistance (MDR) was analyzed by molecular methods. The BACTEC MGIT 960? system with the Epicenter? software was used to perform fitness experiments. The lag phase (t0), the exponential growth time, and the relative fitness (RF) compared to that of H73Rv reference strain, were calculated. From 88 patients 107 isolates of 27 households were included in the study and 378 contacts were also investigated for tuberculosis. MDR was found in 32 patients (17 households); 26 MDR-patients generated 34 secondary and 22 tertiary cases. An average RF drop of 16.7% was found for MDR strains. Mutations in rpoB codons 531 and 526 were respectively found in 22 and 6 cases.  Mutations in katG and inhA genes were found in 18 and 7 cases respectively, in 3 cases mutations remained unidentified. MDR strains were transmitted to 25% of the studied household contacts.