Fig. 1.

Molecular mechanisms of action for antibiotics compared to vaccines. a Antibiotics either kill bacteria (bactericidal) or stop them from growing (bacteriostatic) by four main mechanisms: preventing DNA/RNA synthesis; preventing folate synthesis, which prevents nucleic acid synthesis; destroying the cell wall/membrane; and targeting ribosomes to prevent protein synthesis. Antibiotic resistance mechanisms neutralize the mechanism of action for the antibiotic. Resistance mechanisms can be acquired through horizontal transfer from plasmids and other genetic elements donated by bacteria that are co-localized with the pathogen. Alternatively, resistance can occur through vertical transmission via chromosomal mutations. These resistance mechanisms include the expression of enzymes such as the β-lactamases which inactivate the antibiotics (β-lactams); the expression or overexpression of efflux pumps which remove the antibiotic from the bacteria; the modification of the target so that it is no longer susceptible to the antibiotic; and using bypass mechanisms to circumvent antibiotic toxicity, including modification of the cell surface to prevent antibiotic entry or direct modification of antibiotics to prevent target engagement (Kohanski et al. 2010; Levy and Marshall 2004). b In contrast to antibiotics, vaccines exert their action via immune pathways, eliciting antigen specific polyclonal antibodies that can either neutralize bacterial virulence factors such as toxins or adhesins, or engage effector arms to kill the bacteria through mechanisms including the complement cascade or opsonophagocytic uptake into phagocytes (Forthal 2014). ROS, reactive oxygen species. Copyright [Kathrin U. Jansen, William C. Gruber, Raphael Simon, James Wassil, and Annaliesa S. Anderson] 2021