Antibiotic Resistance Mechanisms
A short overview
Intrinsic Resistance
Antibiotic Resistance is not just a man-made problem. On the contrary it is very well known, that bacteria from natural habitats contain different defensive mechanisms to survive despite antibiotic presence. Reports from the pre-antibiotic era (before the discovery of Penicillin by Fleming in 1928) are especially interesting regarding this so-called intrinisc resistance. That way, scientists did find some microbes being resistant to modern antibiotics despite living 5000 years ago!
However, to understand this phenomenon it has to be taken into account that most antibiotic producers (even those who are relevant for todays medicine) are inhabitants of soils. Hence, it seems quite consistant that non-producers had to develop a strategy against antimicrobials in order to survive next to antibiotic producing microorganisms. We’re calling this process of mutual adapations “Co-Evolution”.
By the way, make sure you give “Alice’s Adventures in Wonderland” a read! The included “Red Queen Theory” is exactly describing the phenomen of interactions between two parallel evolving organisms. This is also comparable to the simultanious evolution and adjustments of prey and predator.
Antibiotic Resistance Mechanisms
There are tons of different antibiotics, but there are even more resistance mechanisms. According to CARD (Comprehensive Antibiotic Resistance Database) 2553 different genes related to antibiotic resistance (not counting similar genes in different bacteria) have been identified so far! Consequently, those genes provide all sort of defensive mechanisms against antibiotics. Above all, the top 4 defensive strategies are: altering the antibiotic target (1), altering the antibiotic (2), degrade the antibiotic (3) and efflux the toxic substance (4). Nobody can adapt better to a changing environment than microorganisms!
Global Spread
Antibiotic resistant microbes can be spread around the globe by several biological and physical forces. This contains big meterological events (e.g. sahara-dust), animal migration, human traveling, global wind- and water-streams and so on… According to brand-new results (micro)plastic particles also are a potential driver for the spread of resistant bacteria!
Regarding humans, the biggest threat is the well-known misuse of antibiotics. May it be false indication, not taking the medicine properly, the use as a precaution in agriculture, or water pollution. As a result, humans are increasing the natural problem of antibiotic resistance — especially in terms of speeding up the process of the evolution of new resistance mechanisms.
Bacterial Conjugation or… how Bacteria have Sex
Let’s talk about sex baby! Bacterial conjugation is giving bacteria the possibility to transfer any genetic information from one to another — even between species! This of course is an important factor in the spread of antibiotic resistance because the selective advantage of antibiotic resistance genes (ARGs) is huge and only microbes containing ARGs will survive in an environment containing antimicrobial compounds.
However, conjugation is not the only way to spread such genetic material. Bacterial reproduction follows the rules of cell-division which always leads to two identical cells that contain the exact same genetic information — including possible antibiotic resistance genes.
On that point — some food for thought: one cell gets resistant to any antibiotic you can think of (through mutations), divides into two cells every 30 minutes (like E. coli — a inhabitant of our gut — does) and lives in a perfect (microbial-)world with no death or nutrient limitation. Within just one day, there would be ~3^14 resistant cells that could conjugate with any other microbe! As a number 4 782 969… savor this slowly!
However, it is not over yet as there is third way of how antibiotic resistance genes can be spread. It is called transduction and involves bacteriophages (viruses that infect bacteria). Basically all that happens is that the virus is taking genetic material from one cell, and injects it into another one during the process of infection.
Bacterial Conjugation or… how Bacteria have Sex
Let’s talk about sex baby! Bacterial conjugation is giving bacteria the possibility to transfer any genetic information from one to another — even between species! This of course is an important factor in the spread of antibiotic resistance because the selective advantage of antibiotic resistance genes (ARGs) is huge and only microbes containing ARGs will survive in an environment containing antimicrobial compounds.
However, conjugation is not the only way to spread such genetic material. Bacterial reproduction follows the rules of cell-division which always leads to two identical cells that contain the exact same genetic information — including possible antibiotic resistance genes.
On that point — some food for thought: one cell gets resistant to any antibiotic you can think of (through mutations), divides into two cells every 30 minutes (like E. coli — a inhabitant of our gut — does) and lives in a perfect (microbial-)world with no death or nutrient limitation. Within just one day, there would be ~3^14 resistant cells that could conjugate with any other microbe! As a number 4 782 969… savor this slowly!
However, it is not over yet as there is third way of how antibiotic resistance genes can be spread. It is called transduction and involves bacteriophages (viruses that infect bacteria). Basically all that happens is that the virus is taking genetic material from one cell, and injects it into another one during the process of infection.
