Antibiotic resistance can come in one of two forms: innate or acquired. Innate resistance is a form of antibiotic resistance that has always been present in a bacterial species – this could include Gram-negative bacteria being resistant to beta-lactam antibiotics (as they do not synthesise (much) peptidoglycan). Acquired resistance occurs when horizontal gene transfer is used to take up a gene conveying resistance to an antibiotic. This is frequently exploited in laboratories, where antibiotic resistance is used as a selectable marker to confirm successful transformation.
Innate resistance can be dealt with in healthcare settings, ensuring the correct antibiotic is used for the species being treated (Gram-negative / Gram-positive, …). Acquired resistance is much more dangerous, and could have occurred through poor prescribing in the past (or poor adherence by the patient). Alternative antibiotics may need to be used, or a higher dose for a longer time. However, there will be a point at which the antibiotics will run out. Bacteriophage therapy could be used, however this is not widely used and could require travelling to different countries with less stringent safety regulations.