Provided is a method for culturing Mycobacteria in the presence of a class A lantibiotic, thereby inhibiting or reducing bacterial contamination in the culture, without significantly disadvantageously affecting or retarding mycobacterial growth. Further provided are the Mycobacteria culture produced thereby, methods for detecting Mycobacteria in a biological sample under conditions that reduce bacterial contamination, and for diagnosing a mycobacterial infection in a biological sample from a subject suspected of having such an infection, as well as, kits useful in practicing such methods.