Effectiveness of Disinfectants on Dormant Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (Mpt) is a gram positive, acid-fast organism that triggers Johne‘s disease, which is a severe gastroenteritis found in ruminants, such as dairy cattle. The accidental ingestion of Mpt from contaminated surfaces is one of the most common means by which ruminants become infected. Mpt has a greater resistance to disinfectants than many other bacteria, so it is important to determine the concentrations at which Mpt cells are eradicated. The purpose of this investigation was to compare the susceptibility of actively growing and dormant Mpt cells in different disinfectants at varying concentrations. The Mpt cells were treated with selected disinfectants, such as benzalkonium chloride and chlorhexidine, at ten-fold concentrations. Viability was measured at regular intervals with flow cytometry. The viability of actively growing Mpt diminished to less than ten percent initially when treated with benzalkonium chloride at the manufacturer‘s recommended concentration. When treated with a ten-fold dilution, the viability of active Mpt was only slightly diminished initially, but over thirty minutes diminished to about twenty percent. The viability of dormant Mpt diminished to less than ten percent initially when treated with benzalkonium chloride at the manufacturer‘s recommended concentration as well. When treated with a ten-fold dilution, the viability of dormant Mpt diminished slightly initially, but within ten minutes diminished to less than ten percent. Treatment of both active and dormant Mpt cells with one hundred and one thousand fold dilutions did not lead to diminished viability. The results of testing with other disinfectants are pending