Transmission of drug-susceptible and drug-resistant Mycobacterium tuberculosis (M/XDR TB) among households contacts

MORCILLO N; B IMPERIALE; DI GIULIO B; M. ZUMÁRRAGA; A. CATALDI

Barcelona

Congreso; 34 Annual Congress of the European Society of Respiratory Medicine; 2013

European Society of Respiratory Medicine

Introduction - The increase of multidrug-resistant Mycobacterium tuberculosis strains and the advent of the extensively drug-resistant tuberculosis (M/XDR-TB) frequently associated to HIV condition, are calling the researches attention on the risk of acquiring M/XDR-TB due to a recent transmission from a community infectious source. -The aim of this study was to estimate the ability of drug-resistant M. tuberculosis -mainly M/XDR-TB- to be transmitted among households contacts, comparing this capability with that from drug-susceptible strains. -Patients? clinical and epidemiological data were collected as well as the drug-susceptibility and genetic patterns of the isolates including resistance-related mutations. Relative fitness (RF) was also calculated for each one of the isolates. MDR was detected BACTEC MGIT960? system and/or confirmed by molecular methods. The MGIT960? system along with the Epicenter? software was used to perform fitness experiments. The lag phase (t0), the exponential growth time, and the RFs compared to that of H73Rv reference strain, were calculated. A combination of bacterial plus clinical and epidemiological data was used to estimate the probable transmission sense. -A total of 217 isolates from 40 households from 169 patients and 694 contacts (average: 3.2/case, range: 2-12) were included in the study. M/XDR was found in 77 patients (29 households); 26 MDR-patients generated 34 secondary and 22 tertiary cases. An average RF drop of 16.7% was found for MDR strains. MDR strains were transmitted to 25% of the studied household contacts.