Types of Bacterial Resistance to   Antibacterial Agents By Spectrum - antibiotic inherently not effective vs. Gram negative   or positive bacteria.   (ex. H.influenzae vs. erythromycin). Inducible - requires exposure to an agent within that class to   increase tolerance to antibiotic.   (ex. erythromycin, tetracycline, etc.). Constitutive - genes that code for resistance are constantly turned on,   even in the absence of an antibiotic within that class. Plasmid mediated - genes coding for resistance are in a small piece of   bacterial DNA separate from the bacterial chromosome Chromosome mediated - genes coding for resistance are in the large chromosome   of the bacterium.