Editing Antimicrobial resistance (section)

=== Natural occurrence ===
[[File:Antibiotic Resistance Spread.jpg|thumb|A CDC infographic on how antibiotic resistance (a major type of antimicrobial resistance) happens and spreads]]
AMR is a naturally occurring process.<ref name="CDC About Antimicrobial Resistance"/> Antimicrobial resistance can evolve naturally due to continued exposure to antimicrobials. [[Natural selection]] means that organisms that are able to adapt to their environment, survive, and continue to produce offspring.<ref name="NS">{{cite web|url=https://evolution.berkeley.edu/evolibrary/article/evo_25|title=Natural selection|website=evolution.berkeley.edu|access-date=2020-03-10|archive-date=30 October 2019|archive-url=https://web.archive.org/web/20191030201404/https://evolution.berkeley.edu/evolibrary/article/evo_25|url-status=live}}</ref> As a result, the types of microorganisms that are able to survive over time with continued attack by certain antimicrobial agents will naturally become more prevalent in the environment, and those without this resistance will become obsolete.<ref name="Holmes_2016" />

Some contemporary antimicrobial resistances have also evolved naturally before the use of antimicrobials of human clinical uses. For instance, [[methicillin]]-resistance evolved as a pathogen of [[hedgehog]]s, possibly as a [[Coevolution|co-evolutionary]] adaptation of the pathogen to hedgehogs that are infected by a [[dermatophyte]] that naturally produces antibiotics.<ref name="MR">{{cite journal | vauthors = Larsen J, Raisen CL, Ba X, Sadgrove NJ, Padilla-González GF, Simmonds MS, Loncaric I, Kerschner H, Apfalter P, Hartl R, Deplano A, Vandendriessche S, Černá Bolfíková B, Hulva P, Arendrup MC, Hare RK, Barnadas C, Stegger M, Sieber RN, Skov RL, Petersen A, Angen Ø, Rasmussen SL, Espinosa-Gongora C, Aarestrup FM, Lindholm LJ, Nykäsenoja SM, Laurent F, Becker K, Walther B, Kehrenberg C, Cuny C, Layer F, Werner G, Witte W, Stamm I, Moroni P, Jørgensen HJ, de Lencastre H, Cercenado E, García-Garrote F, Börjesson S, Hæggman S, Perreten V, Teale CJ, Waller AS, Pichon B, Curran MD, Ellington MJ, Welch JJ, Peacock SJ, Seilly DJ, Morgan FJ, Parkhill J, Hadjirin NF, Lindsay JA, Holden MT, Edwards GF, Foster G, Paterson GK, Didelot X, Holmes MA, Harrison EM, Larsen AR | title = Emergence of methicillin resistance predates the clinical use of antibiotics | journal = Nature | volume = 602 | issue = 7895 | pages = 135–141 | date = February 2022 | pmid = 34987223 | pmc = 8810379 | doi = 10.1038/s41586-021-04265-w | bibcode = 2022Natur.602..135L}}</ref> Also, many [[Soil microbiology|soil fungi and bacteria]] are natural competitors and the original antibiotic [[penicillin]] discovered by [[Alexander Fleming]] rapidly lost clinical effectiveness in treating humans and, furthermore, none of the other natural penicillins (F, K, N, X, O, U1 or U6) are currently in clinical use.{{citation needed|date=April 2023}}

Antimicrobial resistance can be acquired from other microbes through swapping genes in a process termed [[horizontal gene transfer]]. This means that once a gene for resistance to an antibiotic appears in a microbial community, it can then spread to other microbes in the community, potentially moving from a non-disease causing microbe to a disease-causing microbe. This process is heavily driven by the [[natural selection]] processes that happen during antibiotic use or misuse.<ref>{{cite journal | vauthors = Crits-Christoph A, Hallowell HA, Koutouvalis K, Suez J | title = Good microbes, bad genes? The dissemination of antimicrobial resistance in the human microbiome | journal = Gut Microbes | volume = 14 | issue = 1 | pages = 2055944 | date = 2022-12-31 | pmid = 35332832 | pmc = 8959533 | doi = 10.1080/19490976.2022.2055944 }}</ref>

Over time, most of the strains of bacteria and infections present will be the type resistant to the antimicrobial agent being used to treat them, making this agent now ineffective to defeat most microbes. With the increased use of antimicrobial agents, there is a speeding up of this natural process.<ref name="Ferri_2017">{{cite journal | vauthors = Ferri M, Ranucci E, Romagnoli P, Giaccone V | title = Antimicrobial resistance: A global emerging threat to public health systems | journal = Critical Reviews in Food Science and Nutrition | volume = 57 | issue = 13 | pages = 2857–2876 | date = September 2017 | pmid = 26464037 | doi = 10.1080/10408398.2015.1077192 | s2cid = 24549694 }}</ref>