Refers to the paradoxical decreased antimicrobial activity at antibiotic concentrations above some optimal level1
That is, there is more bacteria surviving when exposed to concentrations far higher than MBC compared to those exposed to concentrations at or just above the MBC
Although first described with penicillin and Gram-positive cocci2, the phenomenon has since been observed across many bacteria and many antibiotics
References
^Anggia Prasetyoputri, Angie M. Jarrad, Matthew A. Cooper, Mark A.T. Blaskovich. The Eagle Effect and Antibiotic-Induced Persistence: Two Sides of the Same Coin?. Trends in Microbiology. 2019;27(4):339-354. doi:10.1016/j.tim.2018.10.007.
^Harry Eagle, A. D. Musselman. The rate of bactericidal action of penicillin in vitro as a function of its concentration, and its paradoxically reduced activity at high concentrations against certain organisms. The Journal of Experimental Medicine. 1948;88(1):99-131. doi:10.1084/jem.88.1.99.
