infectious diseases
Factors Facilitating Microbial Invasion
Antimicrobial Resistance
Genetic variability among microbes is inevitable. Use of antimicrobial drugs eventually selects for survival of strains that are capable of resisting them. Emergence of antimicrobial resistance may be due to spontaneous mutation of chromosomal genes. In many cases, resistant bacterial strains have acquired mobile genetic elements from other microorganisms, usually of the same species but sometimes from different ones. These elements are encoded on plasmids or transposons and enable the microorganisms to synthesize enzymes that Modify or inactivate the antimicrobial agent Change the antimicrobial agent's ability to accumulate in the bacterial cell Resist inhibition by the antimicrobial agent (eg, alteration in the target sites of antibiotics is a common mechanism of resistance) Minimizing inappropriate use of antibiotics in humans and in animal and crop farming is important for public health. For further discussion, see Antibiotic Resistance . 