The Mechanisms of Spreading Antimicrobial Resistant Genes in Bacteria


Antimicrobial resistance (AMR) is a pressing global concern, and understanding how bacteria spread resistant genes is crucial in our efforts to combat this threat. In this blog post, we will delve into the scientific mechanisms that facilitate the dissemination of antimicrobial-resistant genes in bacteria.

Horizontal Gene Transfer

Horizontal gene transfer (HGT) stands as a cornerstone in the spread of antimicrobial resistance among bacterial populations. Three primary mechanisms underpin HGT:

  1. Conjugation: Direct Gene Exchange

Conjugation involves the direct transfer of genetic material, including antimicrobial-resistant genes, from one bacterium to another through physical contact. F-plasmids, responsible for carrying resistance genes, play a pivotal role in this process (1).

  1. Transformation: Absorbing Resistance Traits

Transformation allows bacteria to take up free DNA fragments from their environment, including those carrying antimicrobial resistance genes. The competence system in bacteria facilitates the integration of this acquired genetic material into the bacterial genome (2).

  1. Transduction: Bacteriophages as Genetic Couriers

Bacteriophages are viruses that infect bacteria and can serve as carriers of antimicrobial-resistant genes. During infection, bacteriophages can transfer genetic material, including resistance genes, from one bacterium to another, contributing to the genetic diversity of bacterial populations (3).


Plasmids, small extrachromosomal DNA molecules, are mobile genetic elements that significantly contribute to the spread of antimicrobial resistance genes. Bacteria can readily share plasmids, accelerating the transmission of resistance traits within and between bacterial species (4).

Mobile Genetic Elements

Mobile genetic elements, such as transposons and integrons, act as genetic travellers within bacterial genomes. These “jumping genes” can move within the bacterial genome or even jump between different bacterial species, carrying antimicrobial resistance genes with them (5).

Biofilm Formation

Bacteria within biofilms, dense communities in a polysaccharide matrix, have an enhanced ability to exchange genetic material, including antimicrobial-resistant genes. Biofilms create an ideal environment for the transfer of resistance traits among bacteria (6) and are hard to get rid of.

Selective Pressure

The selective pressure exerted by the widespread use and misuse of antimicrobials drives the evolution of bacterial populations. Bacteria carrying resistance genes gain a survival advantage in the presence of antimicrobial agents, leading to the proliferation of resistant strains (7).

Environmental Reservoirs

Environmental reservoirs, including soil and water, serve as large habitats for bacteria. Antimicrobial-resistant bacteria and their genetic material persist in these environments, contributing to the contamination of food sources and water supplies (8).


Understanding the mechanisms behind the spread of antimicrobial-resistant genes in bacteria is essential for developing effective strategies to combat AMR. The scientific literature reveals a complex problem compromising of genetic exchanges, mobile elements, and environmental factors that contribute to the dissemination of resistance. The effort to combatting AMR requires a collaborative and multidisciplinary effort, guided by responsible antimicrobial use and innovative approaches to curb resistance.


  1. Waksma G., & Hultgren S. J. (2009). Structural biology of the chaperone–usher pathway of pilus biogenesis. Nature Reviews Microbiology: 7(11), 765-774.
  2. Johnsborg O., & Håvarstein L. S. (2009). Regulation of natural genetic transformation and acquisition of transforming DNA in Streptococcus pneumoniae. FEMS Microbiology Reviews: 33(3), 627-642.
  3. Ackermann H. W. (2011). Bacteriophage observations and evolution. Research in Microbiology: 162(5), 402-409.
  4. Carattoli A. (2009). Resistance plasmid families in Enterobacteriaceae. Antimicrobial Agents and Chemotherapy: 53(6), 2227-2238.
  5. Partridge S. R., Tsafnat G., Coiera E., & Iredell J. R. (2009). Gene cassettes and cassette arrays in mobile resistance integrons: FEMS Microbiology Reviews, 33(4), 757-784.
  6. Hall-Stoodley L., Costerton J. W., & Stoodley P. (2004). Bacterial biofilms: from the natural environment to infectious diseases. Nature Reviews Microbiology: 2(2), 95-108.
  7. Andersson D. I., & Hughes D. (2010). Antibiotic resistance and its cost: is it possible to reverse resistance? Nature Reviews Microbiology: 8(4), 260-271.
  8. Wellington E. M., Boxall A. B., Cross P., Feil E. J., Gaze W. H., Hawkey P. M., & Williams A. P. (2013). The role of the natural environment in the emergence of antibiotic resistance in gram-negative bacteria. The Lancet Infectious Diseases: 13(2), 155-165.


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About the Author

Picture of Written by Lucy Addison

Written by Lucy Addison

Lucy leads the commercial team at Hygenica, involved in research that analyses the links between infection control protocols, the transmission of Healthcare Associated Infections (HCAIs) and Antimicrobial Resistance (AMR). Lucy holds a first-class degree in Cellular and Molecular Biology from Newcastle University, where she specialised in Microbiology.