@rashida Mycobacteria Avium Complex (MAC) describes a related group of Mycobacteria Avium infections. Until perhaps 10 years ago, it was referred to as MAI (Mycobacteria Avium Intrcellulare) as that was the first on identified. As knowledge progresses there are many more. There are also Mycobacterium Abscessus (sometimes abbreviated MABC) M Gordonae, M bovine and others.
All of these fall into the class of Non-tubercular Mycobacteria(NTM) and are related to whar is known as TB (M tuberculosis)
Of the hundreds of Mycobacteria so far identified, only about a dozen or so are of concern in human infections.