Topic 10 Antimicrobial Resistance

An antimicrobial is a drug that kills bacteria or inhibits their growth.

Antimicrobials are used in two kinds of therapies:

1. Initial therapies

   These kinds of therapies are given for community and hospital-acquired infection for reasons concerning a lack of lab results.

   Such therapies involve broad-spectrum antibiotics and sometimes, a cocktail of antimicrobials to cover a wider range of pathogens.

   Which antimicrobial(s) get used depends on the patient’s symptoms.

2. Definite therapies

   These kinds of therapies begin after lab tests are available.

   Narrow-spectrum antimicrobials should be used in-lieu of broad spectrum ones to not only reduce the toxicity and cost of using anti-microbials, but to also protect against antimicrobial resistance in the community.

Figure 10.1: Difference Between Bacteriocidal and Bacteriostatic Antimicrobials

Bacteriocidal antimicrobials kill microbes while bacteriostatic antimicrobials inhibit the growth of microbes. This is evidenced by both drugs’ effects on the population of antimicrobials in the above figure.

Figure 10.2: Modes of Actions of Different Antibiotics

Most antibiotics will generally target one of several actions in a bacterium:

1. Cell wall or membrane synthesis
2. Nucleic acid synthesis
3. Protein synthesis

Nevertheless, one might choose to take multiple combinations of antibiotics for the following reasons:

1. When two or more antibiotics exhibit an enhanced effect (i.e., a synergistic effect) on a particular pathogen.
2. When seriously ill patients require some form of initial therapy prior to having a lab test performed on them.
3. To treat polymicrobial infections (i.e., infections that are caused by more than one kind of microbe).
4. To prevent antimicrobial resistance from happening within a community.

Figure 10.3: Antibiotics Used in Animal and Human Health

Like shown above, a large number of antibiotic classes overlap in human and veterinary medicine.