Migrations do not modify Mycobacterium tuberculosis resistance rates : a 20-year retrospective study

Tuberculosis (TB) caused by resistant strains is becoming a public health concern also in high-income countries. In Pavia province, Northern Italy, the prevalence of foreign-born has increased in recent years. Nevertheless, it is unclear if this has modified epidemiology and resistance patterns of Mycobacterium tuberculosis. We retrospectively collected data on all the Mycobacterium tuberculosis strains isolated by culture in the microbiology reference laboratory of the province of Pavia from 01/01/1998 to 31/12/2017. Overall, 919 patients were identified, 320 were foreign-born (34.8%). The proportion of cases due to foreign-born patients increased during the study period as did resistance to isoniazid (INH) (p = 0.01), while resistance to rifampicin (RIF) did not (p = 0.8). INH and RIF resistance were comparable among Italian and foreign-born patients (7.9% vs 9.7% for INH and 4% vs 5% for RIF, respectively). Twenty-height (3.05%) patients harboured MDR strains. Prevalence of MDR strains was not different between Italians and foreign-born patients (2.8% vs 3.4%, p = 0.6). During the study period the proportion of TB cases due to foreign-born patients and INH resistance increased. This increase was equal among Italian and foreign-born patients. Migrants in our area are not a driver of resistance to anti-mycobacterial drugs.