Trends of <i>Mycobacterium bovis</i> Isolation and First-Line Anti-tuberculosis Drug Susceptibility Profile: A Fifteen-Year Laboratory-Based Surveillance

<div><p>Background</p><p><i>Mycobacterium tuberculosis</i> causes the majority of tuberculosis (TB) cases in humans; however, in developing countries, human TB caused by <i>M</i>. <i>bovis</i> may be frequent but undetected. Human TB caused by M. <i>bovis</i> is considered a zoonosis; transmission is mainly through consumption of unpasteurized dairy products, and it is less frequently attributed to animal-to-human or human-to-human contact. We describe the trends of <i>M</i>. <i>bovis</i> isolation from human samples and first-line drug susceptibility during a 15-year period in a referral laboratory located in a tertiary care hospital in Mexico City.</p><p>Methodology/Principal Findings</p><p>Data on mycobacterial isolates from human clinical samples were retrieved from the laboratory’s database for the 2000–2014 period. Susceptibility to first-line drugs: rifampin, isoniazid, streptomycin (STR) and ethambutol was determined. We identified 1,165 isolates, 73.7% were <i>M</i>. <i>tuberculosis</i> and 26.2%, <i>M</i>. <i>bovis</i>. Among pulmonary samples, 16.6% were <i>M</i>. <i>bovis</i>. The proportion of <i>M</i>. <i>bovis</i> isolates significantly increased from 7.8% in 2000 to 28.4% in 2014 (<i>X</i>^<i>2</i>_trend, p<0.001). Primary STR resistance was higher among <i>M</i>. <i>bovis</i> compared with <i>M</i>. <i>tuberculosis</i> isolates (10.9% vs.3.4%, p<0.001). Secondary multidrug resistance (MDR) rates were 38.5% and 34.4% for <i>M</i>. <i>bovis</i> and <i>M</i>. <i>tuberculosis</i>, respectively (p = 0.637). A rising trend of primary STR monoresistance was observed for both species (3.4% in 2000–2004 vs. 7.6% in 2010–2014; p = 0.02).</p><p>Conclusions/Significance</p><p>There is a high prevalence and a rising trend of <i>M</i>. <i>bovis</i> isolates in our region. The proportion of pulmonary <i>M</i>. <i>bovis</i> isolates is higher than in previous reports. Additionally, we report high rates of primary anti-tuberculosis resistance and secondary MDR in both <i>M</i>. <i>tuberculosis</i> and <i>M</i>. <i>bovis</i>. This is one of the largest reports on drug susceptibility of <i>M</i>. <i>bovis</i> from human samples and shows a significant proportion of first-line anti-tuberculosis drug resistance.</p>