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PHA 3112 Study Guide - Final Guide: Gram Staining, Drug Resistance, Meningitis

Course Code
PHA 3112
Frank Feiner
Study Guide

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Infectious disease
Chapter 83: Antimicrobial therapy
Basic Principles
Infectious disease drugs widely used: 30% all hospitalized pts
Modern antimicrobial agents discovered 1930-40s
Able to fight more infections
M&M decrease
In spite of continued progress/ newer drugs needed:
o Some organisms impervious
o Evolving microbial resistance
o Drug toxicity
Classification of organism
o Aerobic/ anaerobic: euies/ doest eed O2 to suie & go
o Shape
o Gram stain
Drug Classification
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Kill small range of microbes, or large range of microbes
Narrow spectrum: active against only a few species of microorganisms
Broad Spectrum:
Drug Classification: Mechanism of Action
Selective Toxicity: Drug injures target organism, not host (us)
o Inhibit bacterial cell wall synthesis/activate enzyme that disrupt cell wall (Ex. penicillins,
o Increase cell membrane permeability (Ex. amphotericin B) (bacterium w/o cell wall will
o Lethal inhibition of bacterial protein synthesis (Ex.gentamicin)
o Nonlethal inhibition of protein synthesis (eg tetracyclines).
o inhibit bacterial synthesis of DNA and RNA or disrupt DNA function (eg rifampin,
metronidazole, ciprofloxacin)
o Antimetabolites disrupt specific biochemical reactions (Ex. sulfonamides)
o suppress viral replication (eg acyclovir, zidovudine)
Antibacterial drugs are either bactericidal or bacteriostatic.
o Bactericidal: directly lethal to bacteria (directly kill)
o Bacteriostatic: slow bacterial growth but do not cause cell death
Bacteria eliminated via immune system +phagocytic cells).
Acquired Resistance to Antimicrobial drugs ***
Susceptibility of organism gradually decrease total loos of sensitivity
Renders currently effective drugs useless
Microbe- not pt- becomes drugs resistant: need new agents !
Microbial Mechanisms of Drug Resistance:
o Decrease uptake to/ increase export from site of action of drug in bacterium (drug can
o loge get to hee it supposed to get, o it doest last log
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o Inactivation of drug via drug-metabolizing enzymes
o Alteration of target of drugs action
o Produce antagonists: interfere w/ drug
All Result From Changes in Bacterial DNA
o Each offspring might be different
Antibiotics Promote Resistance ***
Atiiotis ot utagei: dot hage ateial DNA
Allow overgrowth of microbe mutants that (by sheer chance) have acquired resistance
Antibiotics promote drug-resistant organisms
Use antibiotics conservable
o Kill off all drug-sensitive species
Remove competition for available nutrients
o And promote overgrowth of resistant normal flora- that can transmit R factors ( and
resistance !) to pathogenic bacteria
Broad-spectrum antibiotics facilitate more resistance
The more antibiotics are used; the faster drug-resistant organisms emerge: avoid use when no
treatable infection
Superinfection: new 2nd infection during Rx for a primary infection
Hospital-Acquired/ Nosocomial Infections
Hospital: increase antibiotic use
Resident organisms very drug resistant
Among most difficult to Rx
1/20 pts infected Q yr many deaths
Delaying the Emergence of Resistance in Hospitals
o U.S Centres for Disease Control (CDC) campaign:
Adhere to prescribing guidelines
Decrease demand for antibiotics  idiiduals ho dot eed the
Increase adherence to prescribe antibiotics
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