Antimicrobials resistance

Various bacteria inhabit the body of man and animals, can be found in the environment, and are considered as reservoirs of multidrug resistance.

The term antimicrobial can refer to antibacterial, antiviral and antifungal agents each one of which has a specific action against specific groups of microorganisms, and in many instances the term is used synonymously with antibiotic. An antimicrobial can be defined as any substance of natural, semisynthetic, or synthetic origin that kills or inhibits the growth of a microorganism, whilst an antibiotic is a substance produced by a microorganism that at low concentrations inhibits or kills other .microorganisms 1,3


Antimicrobial resistance (AMR) is a worldwide agricultural and clinical problem, indicating the success and speed of bacterial adaptation to lethal selection in different environments. In spite of the fact that antibiotics have been in clinical use for a little over six decades, they have existed on Earth for about three billion years, and bacteria have developed protection mechanisms towards antibiotics and other toxic chemicals. Various bacteria inhabit the body of man and animals, can be found in the environment, and are considered as reservoirs of multidrug resistance. Those bacteria are not restricted to an isolated environment but are easily dispersed to other environments, for example: 

from humans and animals to water and soil and vice versa (as shown in the figure). That is why the spread of AMR is regarded as a major challenge to human and animal health that needs to be controlled 2. Antimicrobial resistance has been widely recognized as a growing problem and many organizations and networks monitor antimicrobial resistance trends locally and internationally


Resistance genes can arise amongst bacteria by two routes: spontaneous mutation and horizontal gene transfer (HGT) . To acquire these resistance genes, bacteria need a range of mechanisms that depend on different gene transfer systems such as bacterial conjugative plasmids and transposable elements (mobilizable plasmid and transposons) and integrons. Bacterial plasmids can collect arrays of antimicrobial resistance genes, by transposition (transposable elements) and sitespecific recombination mechanisms (integron gene cassettes) leading to transferable multidrug .resistance 1,4


Possible routes for the transfer of antibiotic resistance bacteria or genes between livestock animals and humans (adapted from Wellington et al., 2014).


References 1. GIGUERE et al., 2013. Antimicrobial Therapy in Veterinary Medicine. 5 ed. Somerset: Wiley WELLINGTON et al., 2013. The role of the natural environment in the emergence of .2 antibiotic resistance in Gram-negative bacteria. The Lancet Infectious Diseases, 13, .155-165 PHOENIX et al.,. 2014. Novel Antimicrobial Agents and Strategies, John Wiley & Sons .3 4. BENNETT, P. M. 2008. Plasmid encoded antibiotic resistance: acquisition and transfer of antibiotic resistance genes in bacteria. British Journal of Pharmacology, 153 Suppl 1, S347-57.