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Chapter 20-Antimicrobial Agents
_______________:The use of drugs to treat a disease (not necessarily infectious) Antimicrobial drugs: Interfere with the growth of microbes within a host Antibiotic: Substance produced by a microbe that, in small amounts, ____________ another microbe Selective toxicity: A drug that kills harmful microbes without damaging the host
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DISCOVERY and PURIFICATION of PENICILLIN
1928 – ___________ discovered penicillin, produced by Penicillium. 1940 – Howard Florey and Ernst Chain performed first clinical trials of penicillin. Naturally occurring antimicrobials Metabolic products of bacteria and fungi _________: Streptomyces sp., Bacillus sp. _________: Penicillium sp., Cephalosporium sp. Figure 20.1
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The Action of Antimicrobial Drugs
Broad-spectrum Affect wide range of G+ and G- bacteria Disadvantage is disruption of ___________ Ex. Tetracycline Narrow-spectrum Affect small, __________ range of bacteria Gram positive only or gram negative only Ex. Penicillin G affects G+ but not G- bacteria
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TYPES OF ANTIMICROBIAL ACTION
Drugs may kill or inhibit bacterial growth 1._________________________ the growth of microorganisms Bacteriostatic drugs rely on host immunity to eliminate pathogen 2._________________________ microorganisms Bacteriocidal drugs are useful in situations when host defenses cannot be relied upon to control pathogen
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Adverse Effects of Antimicrobial Drugs
____________ REACTIONS Allergies to penicillin Allergies often life threatening TOXIC EFFECTS Ex.: Aplastic anemia Body cannot make RBC or WBC SUPPRESSION of _______________ Antibiotic associated colitis Toxic organisms given opportunity to establish themselves ANTIMICROBIAL ________________ Microorganisms have innate or adaptive resistance to antibiotics
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Major Action Modes of Anti_______________ Drugs
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ANTI_____________ ANTIBIOTICS
MODE of ACTION: Interference with essential processes of Mycobacterium tuberculosis 1. _________ (NIH) – inhibits synthesis of _______ acid 2. Ethambutol – inhibits incorporation of mycolic acid into the cell wall MODE of ACTION: Blocks _______________ 1. Rifampin
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Anti-___________ Drugs
amantadine and rimantadine Mode of action: block the ______________ of influenza virus after it enters cell Reduces severity and duration of disease Zidovudine ____ and _____________ Mode of action: blocks nucleic acid synthesis
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ANTI_______________ DRUGS
Mode of action: Inhibition of ergosterol synthesis Amphotericin B Produced by Streptomyces species Treatment of ____________ fungal diseases Toxic to kidneys ___________________ Treatment of athlete’s foot and vaginal yeast infections Ketoconazole Less toxic than miconazole Topical application for cutaneous mycoses Figure 20.15
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Anti-____________ Drugs
Chloroquine Inhibits DNA synthesis Plasmodium species - __________ Metronidazole Damages DNA ___________ sp., Trichomonas sp.
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Anti-________________ Drugs
Niclosamide Prevents ATP generation _______________ Praziquantel Alters _________ permeability Flatworms Mebendazole Interferes with ________________________ Effective against tapeworms and roundworms Used in livestock industry
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KIRBY BAUER ANTIMICROBIAL SUSCEPTIBILITY TESTING:
Figure 20.17
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FOUR MAIN MECHANISMS of ANTIBIOTIC __________________________
Resistance genes are often on plasmids or transposons that can be transferred between bacteria.
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Antibiotic ______________
Misuse of antibiotics selects for resistance Misuse includes: Using ___________________ antibiotics Using antibiotics for the common cold and other _________________ conditions Use of antibiotics in ________________ Failure to complete the prescribed regimen Using someone else's leftover prescription
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Antimicrobial Resistance
Staphylococcus aureus Common cause of __________________ infections Becoming increasingly resistant In past 50 years most strains acquired resistance to penicillin Due to acquisition of ____________ genes Until recently most infections could be treated with methicillin (penicillinase resistant penicillin) Many strains have become resistant MRSA methicillin resistant MRSA strains are becoming resistant to vancomycin
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