European Society of Mycobacteriology - Instituto Nacional de Saúde ...

PP-13
IMPORTANCE OF MOLECULAR TYPING IN SUSPECTED
INTRA-FAMILIAL TRANSMISSION OF TUBERCULOSIS
Obrovac, Mihaela 1 , Katalinic-Jankovic, Vera 1 , Grce, Magdalena 2 , Zmak, Ljiljana 1
1 - Croatian National Institute of Public Health
2 - Rudjer Boskovic Institute
Tuberculosis (TB) is most commonly transmitted from a person suffering from infectious pulmonary TB to another person
by infected droplet nuclei. The chance that a person will be infected with TB depends on the intensity, frequency and duration
of the exposure to tubercle bacilli. Also, numerous studies emphasize the importance of host resistance and hereditary
susceptibility, indicating that the development of TB is a result of a complex interaction between the host and the pathogen
influenced by environmental factors. Assuming that there is prolonged duration and frequency of contact between family
members and among household contacts, it is estimated that the risk of TB transmission will be high. There are several
studies confirming intra-familial transmission using genotyping of isolated M. tuberculosis strains. However, the possibility of
unsuspected transmission should not be disregarded. We report here of two cases of suspected TB transmission in families
caused by M. tuberculosis strains that were found not to be identical according to genotyping profiles obtained by determining
variabile number of tandem repeats (VNTR) of mycobacterial repetitive interspersed units (MIRU). Genotyping was performed
using complete set of 24 VNTR loci. Epidemiological data were collected by contact tracing and interviewing patients.
Our results show that TB cases in family do not necessarily have to be caused by the same M. tuberculosis strain. Epidemiologic
investigations need to be combined with genotyping data for better understanding of transmission dynamics. Transmission of
TB cannot be confirmed by contact investigation only, even when intra-familial transmission is suspected.
European Society of Mycobacteriology | 30 th Annual Congress | July 2009 | Porto - Portugal
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