Detection and recognition of Micobacterium tuberculosis in PPD positive cattle by microbacterial culture and biochemical tests in Esfahan province

Despite the long-run anti bovine tuberculosis (BTb) scheme in Iran, BTb remains a major problem in the national cattle farming that causes substantial economical loss. In this search (2006-2009), isolation of Mycobacterium bovis, the causative agent of BTb,from tuberculin positive (reactor) cattle slaughtered in Isfahan has been addressed. Mesenteric and mediastinal lymph nodes along with pathological specimens(if present) from 143 cattle were cultured on Lownstein-Jenson (LJ) slopes. The 28 isolates representing mycobacterial growth characteristics eg. Acid fastness in microscopy, were subjected to a standard biochemical algorythm comprising preferential growth on pyruvate LJ medium, catalase, niacin, nitrate reductase, tiophen carboxylic hydrazide acid (TCH) and production of cord factor tests. Consequently, all the 28 isolates were identified as M. bovis. These isolates originated from 8 farms in different regions of Isfahan province with 15 of them coming from a single herd in Baharestan followed by two more farms with 4 isolates from each. The remaining 5 single isolates were collected from 5 herds in Dolatabad, Najafabad, Tiran, Golshar and Ghaleh Shour regions. Isolation of M. bovis as the single mycobacterial causative pathogen in the recator cattles of Isfahan is another confirmatory observation that no other member of Mycobacterium tuberculosis complex plays a role, if any, in epidemiology of BTb in Isfahan as is the case with rest of Iran. In three out of the 8 farms studied here, there were 4 or more M. bovis isolates collected from every herd an indication of BTb epidemics in these herds. Whether single strain or multiples strains of M. bovis have been involved in the disease outbreaks in these farms, furher molecular epidemiology work is required.