Pathogenic bacteria live by the motto espoused by German philosopher Fredrich Nietzsche (1844-1900): “what does not kill me makes me stronger.”
“Antimicrobial resistance is the ability of a microbe to grow in an inhibitory concentration of an antibiotic, whereas tolerance is a reduced rate of antimicrobial killing,” state American pharmacologists Elizabeth Hirsch & Andrew Berti.
Antibiotic-tolerant bacteria stop growing when antibiotics are around. Going dormant helps them weather the assault. “They’re just putting their heads down,” says Israeli biophysicist Nathalie Balaban.
Tolerant bacteria can’t overcome or counteract antibiotics like resistant organisms do. But getting doused in a toxin incentivizes bacteria to develop resistance.
“Pathways implicated in tolerance development are diverse and include inorganic phosphate metabolism, nucleotide signaling, transfer RNA charging, and toxin-antitoxin systems. Such mutations are heritable and typically alter either the threshold at which a given stressor can induce tolerance or the ease by which tolerant microbes can emerge from the tolerant state and resume growth,” elaborate Hirsch & Berti.
“Although bacterial populations exposed to multiple antibiotics can develop tolerance to multiple drugs, one drug in a combination may be able counter resistance to a partner drug and provide effective therapy. However, if tolerance has already emerged to one drug, the combination may end up promoting the transmission of resistance to a partner drug,” explains Balaban.
Proteins comprise the workforce of all cells. Proteins inside cells do their best to mitigate the damage from environmental pollution – in this instance, antibiotics. These innovative macromolecules work the problem until they figure a way to dispose of the poison and thereby develop resistance.
Meanwhile, proteins on cell membranes monitor the environment for plasmids: communiques from other bacteria which might tell how to develop resistance. Bacteria regularly share helpful homemaking tips, even when the domicile is inside someone else’s cell.
References:
Elizabeth Hirsch & Andrew Berti, “Tolerance to antibiotics affects response,” Science (10 January 2020).
Jiafeng Liu et al, “Effect of tolerance on the evolution of antibiotic resistance under drug combination,” Science (10 January 2020).
Tina Hesman Saey, “How bacteria nearly killed by antibiotics can recover – and gain resistance,” Science News (28 May 2019).
Tina Hesman Saey, “Microbes slowed by one drug can rapidly develop resistance to another,” Science News (28 May 2019).
Ishi Nobu, “Germs,” (14 November 2019).
Ishi Nobu, “Antibiotics,” (25 December 2019).
Ishi Nobu, The Science of Existence, BookBaby (2019).
Ishi Nobu, The Web of Life, BookBaby (2019).