This week in lecture we discussed antibiotic resistance of microorganisms. Mechanisms for antibiotic resistance include innate or acquired resistance, enzymatic destruction or modification of the drug, altered "targets" of drug recognition and binding, and decreased uptake of the drug . Innate resistance occurs when the resistance results from the normal genetic, structural or physiologic state of the organism. One example being that gram-negative bacteria are innately resistant to vancomycin because vancomycin is too large to penetrate the outer membrane. Acquired resistance can occur because of a spontaneous mutation in the genetic makeup caused by excessive antibiotic treatment and exposure or changes in genetic makeup caused by genetic recombination from one organism to another. Alterations in cellular physiology and structure can also be a mechanism of acquired resistance.
Beta-lactamase is a classic example of enzymatic destruction of a drug. Beta-lactamase destroys the beta-lactam ring of penicillin drugs so the drugs can’t bind to PBPs and interfere with cell wall synthesis. H. influenzae and K. pneumoniae are resistance to ampicillin while S. aureus and N. gonorrhoeae are resistant to penicillin.
S. pneumoniae is resistant to penicillin and cephalosporin because it can change its PBPs so that they don’t bind well to beta-lactam drugs. This is an example of altered targets. The bacteria alters or changes the structure that the drug recognizes so the drug no longer works properly. S. aureus is resistant to erythromycin in this way also because it alters ribosomal targets so the drug can’t attach and interfere with protein synthesis.
Bacteria can also decrease the uptake of the drug by altering porin channels or by activation of the "efflux" pump the remove the drug from inside the cell. Pseudomonas is resistance to imipenem and aminoglycosides because alterations of porin channels decreases the amount of drug uptake.
Click here for a link to a new article about scientists who have discovered a drug resistant strain of Neisseria gonorrhoeae. The new strain has genetically mutated to be resistant against cephalosporins which are the only antibiotics still effective in treatment.
I had read about the new strain of Neisseria gonorrhoeae last week I believe. That is a very interesting article and appreciate you posting a link to it! This kind of news is fairly frightening to me. I would not want to see the day in which more and more strains of bacteria are resistant to all treatment. Being in a clinical laboratory exposes us to far bacteria more than "normal" people It is just another reminder of how one should always practice the safest methods in the clinical laboratory.
ReplyDeleteI really found the lectures on AST to be interesting. I enjoyed learning about the interactions between drugs and bacteria. It's interesting to see how the bacteria is resistant or sensitive to the antimicrobial agent being used. It's actually kind of a scary thought to see how many bacteria are becoming resistant.
ReplyDeleteNikki McGalliard
Interesting and scary article. Problems with drug resistance just keep growing!
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