Antibiotic Basics for Clinicians: The ABCs of Choosing the by Alan R. Hauser MD PhD

By Alan R. Hauser MD PhD

Show description

Read or Download Antibiotic Basics for Clinicians: The ABCs of Choosing the Right Antibacterial Agent Second Edition PDF

Best pharmacology books

Additional resources for Antibiotic Basics for Clinicians: The ABCs of Choosing the Right Antibacterial Agent Second Edition

Example text

HI S T O RY By chance, Alexander Fleming took a 2-week vacation immediately after inoculation of his soon-to-be contaminated agar plates. Since he knew he would not be able to examine the plates for 2 weeks, he incubated them at room temperature instead of 37° C to slow the growth rate of the bacteria. His vacation changed the course of human events. Penicillium grows at room temperature but not 37°C—had Fleming not taken a vacation, he never would have observed the bactericidal effects of the mold.

They are called natural penicillins because they can be purified directly from cultures of Penicillium mold. The R side chain of penicillin G is shown in Figure 5-6 and consists of a hydrophobic benzene ring. Since nearly all bacteria have cell walls composed of peptidoglycan, it is not surprising that the natural penicillins are active against some species of gram-positive, gram-negative, and anaerobic bacteria, as well as some spirochetes. Despite this broad range of activity, most bacteria are either intrinsically resistant or have now acquired resistance to the natural penicillins.

Understanding the reasons for this can help one remember which species remain susceptible. In turn, the bacterial spectra of the natural penicillins can be used as a foundation for remembering the spectra of the other classes of penicillins. The six Ps explain resistance to the natural penicillins: (1) Penetration—natural penicillins, like most ␤-lactams, penetrate poorly into the intracellular compartment of human cells, so bacteria that for the most part reside in this compartment, such as Rickettsia and Legionella, are protected from them.

Download PDF sample

Rated 4.16 of 5 – based on 5 votes