Antimicrobial pharmacodynamics is the relationship between the concentration of an

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

and its ability to inhibit vital processes of endo- or ectoparasites and

microbial A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

organisms.C.H. Nightingale, T. Murakawa, P.G. Ambrose (2002) Antimicrobial Pharmacodynamics in Theory and Clinical Practice Informa Health Care This branch of

pharmacodynamics Pharmacodynamics (PD) is the study of the biochemistry, biochemical and physiology, physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or comb ...

relates the concentration of an anti-infective agent to its effect, specifically to its antimicrobial effect. __TOC__

Concentration-dependent effects

The

minimum inhibitory concentration In microbiology, the minimum inhibitory concentration (MIC) is the lowest concentration of a chemical, usually a drug, which prevents visible ''in vitro'' cell growth, growth of bacteria or Fungus, fungi. MIC testing is performed in both diagnosti ...

(MIC) and

minimum bactericidal concentration The minimum bactericidal concentration (MBC) is the lowest concentration of an antibacterial agent required to kill a particular bacterium. It can be determined from broth dilution minimum inhibitory concentration (MIC) tests by subculturing to ag ...

are used to measure ''

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

'' activity of

antimicrobial An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...

agents. They are good indicators of antimicrobial potency, but don't give any information relating to time-dependent antimicrobial killing (the so-called post antibiotic effect).

Post-antibiotic effect

The post-antibiotic effect (PAE) is defined as persistent suppression of

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

l growth after a brief exposure (1 or 2 hours) of bacteria to an

even in the absence of host defense mechanisms. Factors that affect the duration of the post-antibiotic effect include duration of antibiotic exposure, bacterial species, culture medium and class of antibiotic. It has been suggested that an alteration of DNA function is possibly responsible for the post-antibiotic effect following the observation that most inhibitors of protein and nucleic acid synthesis (

aminoglycosides Aminoglycoside is a medicinal chemistry, medicinal and bacteriology, bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside ...

fluoroquinolones Quinolone antibiotics constitute a large group of broad-spectrum antibiotic, broad-spectrum bacteriocidals that share a bicyclic molecule, bicyclic core structure related to the substance 4-Quinolone, 4-quinolone. They are used in human and ve ...

tetracyclines Tetracyclines are a group of broad-spectrum antibiotic compounds that have a common basic structure and are either isolated directly from several species of ''Streptomyces'' bacteria or produced semi-synthetically from those isolated compounds. ...

clindamycin Clindamycin is a lincosamide antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (mi ...

, certain newer

macrolides Macrolides are a class of mostly natural products with a large macrocycle, macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. Macrolides belong to the polyketide class of natural prod ...

/ ketolides, and

rifampicin Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), ''Mycobacterium avium'' complex, leprosy, and Legionnaires' disease. It is almost always used tog ...

and

rifabutin Rifabutin (Rfb) is an antibiotic used to treat tuberculosis and prevent and treat ''Mycobacterium avium'' complex. It is typically only used in those who cannot tolerate rifampin such as people with HIV/AIDS on antiretrovirals. For active tuberc ...

) induce long-term PAE against susceptible bacteria. Theoretically, the ability of an antibiotic to induce a PAE is an attractive property since antibiotic concentrations could fall below the MIC for the bacterium yet retain their effectiveness in their ability to suppress the growth. Therefore, an antibiotic with PAE would require less frequent administration and it could improve patient adherence with regard to pharmacotherapy. Proposed mechanisms include (1) slow recovery after reversible nonlethal damage to cell structures; (2) persistence of the drug at a binding site or within the

periplasmic space The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in Gram-negative (more accurately "diderm") bacteria. Using cryo-electron microsco ...

; and (3) the need to synthesize new enzymes before growth can resume. Most antimicrobials possess significant in vitro PAEs (≥ 1.5 hours) against susceptible gram-positive

cocci Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archaea ...

. Antimicrobials with significant PAEs against susceptible gram-negative bacilli are limited to carbapenems and agents that inhibit protein or DNA synthesis.Katzung basic and clinical pharmacology 13th edition 2015

References

{{Pharmacology Antibiotics Pharmacodynamics