Final answer:
The microbe causing concern due to resistance to isoniazid and rifampin is Mycobacterium tuberculosis, particularly its forms MDR-TB and XDR-TB, leading to challenges in treatment and the rise of 'superbugs.'
Step-by-step explanation:
The microbe of growing concern due to increasing resistance to 'first-line medications,' including isoniazid and rifampin, is Mycobacterium tuberculosis.
This strain, known as Multidrug-Resistant Mycobacterium tuberculosis (MDR-TB) and in more severe cases as extensively drug-resistant Mycobacterium tuberculosis (XDR-TB), is resistant to multiple antimicrobials, making it highly challenging to treat.
Drug resistance in microbes like MDR-TB can lead to so-called 'superbugs,' which are strains that carry one or more resistance mechanisms, rendering them resistant to multiple antibiotics.
This situation is exacerbated by the misuse or mismanagement of antibiotic therapies, which selects for resistant strains. MDR-TB in particular arises from the incorrect use of medications for tuberculosis treatment, consequently requiring careful attention to proper multidrug treatment protocols to prevent further resistance development.