Insights into Antibiotic Resistance Through Metagenomic Approaches

Robert Schmieder; Robert Edwards


Future Microbiol. 2012;7(1):73-89. 

In This Article

Mechanisms of Antibiotic Resistance

Resistance to antibiotics can be caused by four general mechanisms (Figure 2):[5]

Figure 2.

Mechanisms of antibiotic resistance in bacteria. The classes of antibiotics affected by each of the mechanisms are listed in the boxes.

  • The inactivation or modification of the antibiotic;

  • An alteration in the target site of the antibiotic that reduces its binding capacity;

  • The modification of metabolic pathways to circumvent the antibiotic effect;

  • The reduced intracellular antibiotic accumulation by decreasing permeability and/or increasing active efflux of the antibiotic.

Bacteria can develop resistance to antibiotics by mutating existing genes (vertical evolution),[6,7] or by acquiring new genes from other strains or species (horizontal gene transfer).[8,9] The sharing of genes between bacteria by horizontal gene transfer occurs by many different mechanisms. Mobile genetic elements, including phages, plasmids and transposons mediate this transfer, and in some circumstances the presence of low levels of the antibiotic in the environment is the key signal that promotes gene transfer,[10] perhaps ensuring that the whole microbial community is protected from the antibiotic.[11]