Chapter 10: Antimicrobial Compounds

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Microbiology and Immun (Sci)
MIMM 465
Albert Berghuis

Chapter 10 Antimicrobial Compounds Killing versus Inhibiting Growth y The first key concept is the key difference between bactericidal and bacteriostatic compounds o BactericidalKill bacteriaPeople with defective defenses require bactericidal o BacteriostaticStop or slow growth of bacteriaEffective if patients have intact immune system because body defenses only need a little help y It is now clear that the distinction between these compounds not only lies in the properties of the compound but in the properties of the bacteria y For instance you can have bacterial biofilms that progressively go into a less active state therefore a bactericidal antibiotic becomes either bacteriostatic or ineffective because of the growth state of the bacteria y This is the reason why bacteria in biofilms on catheters and plastic implants are difficult to eliminate y A second key component in antimicrobial therapy is the distribution of the drug in the body y Sometimes you can only use the antibiotics on the skin or inanimate objects because they are too toxic such as disinfectants and antiseptics y Antibiotics are used inside of the body but not always in equal distribution because each one has special pharmokinetics which is the term used to describe distribution of antimicrobials inside the body y For instance antimicrobials for UTIs will be primarily in the kidneys and urine and do not go to other parts of the body y Much of antibiotic development is on determining how the antibiotic is localized in the body y The third concept is the side effects y Even very specific compounds like penicillin can affect humans by allergies y Also aminoglycosides may destroy hearing y Therefore the state of the patient and the length of the treatment are very importantAntiseptics and Disinfectants y Most kill or inhibit growth majority are bactericidaly Some are also effective against other disease microbes such as viruses and protozoa y But they can also affect humans because they are too toxic therefore they are only applied to the skin or inanimate surfaces y Antiseptic o Applied to skin like when washing hands y Disinfectant o Applied on inanimate surfaceso Like phenol which cannot be applied to hands o Some fall into both categories like Cl and NH4 compounds o They tend to attack multiple targets such as bacterial proteins like Halides and H2O2 They can also cause DNA damage y Quaternary ammonium compounds QACs o Intercalate into phospholipid bilayer causing leaks of vital ions and small molecules disrupting Electron Transport Chain o Like Centrimide and benzalkonium Cl o However bacterial spores are generally resistant to antiseptics and disinfectants
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