lecture 12 -antimicrobial drugs

7/25/2019 Lecture 12 -Antimicrobial Drugs

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Antimicrobial Drugs

11 May 2013



Antimicrobial Drugs

• Chemotherapy The use of drugs to treat adisease

• Antimicrobial drugs Interfere with thegrowth of microbes within a host

• Antibiotic ubstance produced by amicrobe that! in small amounts! inhibits

another microbe• electi"e to#icity A drug that $ills harmful

microbes without damaging the host



• 1%2& ' (lemingdisco"eredpenicillin!produced byPenicillium)

• 1%*0 ' +oward(lorey and ,rnstChain performed-rst clinical trialsof penicillin)

• All three were

awarded the.obel /rie inMedicine in 1%*

(igure 20)1



Table 20.1

Many Antibiotics come from Bacterial or Fungal Sources



Table 20)2



The Action of AntimicrobialDrugs

• Disrupt Cell all synthesis or throughdamage

•Disrupt /roteins synthesis• Disrupt .ucleic Acid synthesis orfunction

• Disrupts essential metabolicenymesusually by competiti"einhibition)



Drugs

Figure 20.2



Drugs

Figure 20.4



/enicillins

Figure 20.6


http://slidepdf.com/reader/full/lecture-12-antimicrobial-drugs 10/31Figure 20.8

/enicillinase ,nyme Allows4acteria to be 5esistant to

/enicillin



• Cephlosporinsused /enicillin structure tosynthesie antibiotics more e6ecti"e on 7ram.egati"e bacteria

• /olypeptide antibiotics

4acitracin

• Topical application

• Against grampositi"es

8ancomycin

• 7lycopeptide

• Important 9last line9 against antibiotic resistant S. aureus

:ther Inhibitors of Cell allynthesis



• Antimycobacterium antibiotics ;T4! <eprosy= Isoniaid ;I.+=

• Inhibits mycolic acid synthesis

,thambutol

• Inhibits incorporation of mycolic acid

:ther Inhibitors of Cell allynthesis



• Tetracyclines

4road spectrum

• Interferes with t5.A attachment

• ,rythromycin

7rampositi"es• 4inds 0! pre"ents translocation

Inhibitors of /rotein ynthesis

• /olymy#in 4

Topical

Combined with bacitracin and neomycin

in o"erthecounter preparation

In>ury to the /lasma

Membrane



• 5ifamycin Inhibits 5.A synthesis

Antituberculosis

• ?uinolones and @uorouinolones Cipro@o#acin

Inhibits D.A gyrase

Brinary tract infections

Inhibitors of .ucleic Acidynthesis



ulfonamides ;ulfa drugs=

• Inhibit folic acid synthesis

• 4road spectrum

Competiti"e Inhibitors

Figure !."



Figure 20.1#



n unga rugsInhibition of ,rgosterol

ynthesis

• ,chinocandins Inhibit synthesis of βglucan

Inhibition of Cell allynthesis

• ,rgosterol important part of fungalcell wall) Bniue to fungi! therefore agood drug target



• (lucytocine Cytosine analog interferes with 5.A

synthesis

Antifungal DrugsInhibition of .ucleic Acids

• Tolnaftate Bsed for athletes foot action un$nown

Antifungal DrugsInhibition of Microtubules

;Mitosis=



.ucleoside and .ucleotide

Analogs

Figure 20.16a



.ucleoside and .ucleotide

Analogs

Figure 20.16b$

c



• /rotease inhibitors Indina"ir• +I8

• Inhibit attachment

Eanami"ir• In@uena

Anti"iral DrugsF ,nymeInhibitors

• Chlorouine

Inhibits D.A synthesis

• Malaria

Antiprotooan Drugs



• A "ariety of mutations can lead to antibioticresistance)

• Mechanisms of antibiotic resistance

1) ,nymatic destruction of drug

2) /re"ention of penetration of drug

3) Alteration of drugs target site

*) 5apid e>ection of the drug

• 5esistance genes are often on plasmids or

transposons that can be transferred betweenbacteria)

Antibiotic 5esistance



• Misuse of antibiotics selects forresistance mutants) Misuse includesF

Bsing outdated! wea$ened antibiotics

Bsing antibiotics for the common cold andother inappropriate conditions

Bse of antibiotics in animal feed

(ailure to complete the prescribed regimen

Bsing someone elses lefto"er prescription

Antibiotic 5esistance



Dis$Di6usion Test

(igure 20)1G



Chemical Methods ofMicrobial Control

Figure 7.6

Evaluating a disinfectant Disk-diffusion method



• MIC Minimal inhibitory concentration• M4C Minimal bactericidal concentration



, Test

(igure 20)1&



• ynergism occurs when the e6ect of two drugstogether is greater than the e6ect of either alone)

• Antagonism occurs when the e6ect of two drugstogether is less than the e6ect of either alone)

Drugs



Drugs

Figure 20.22

Th ( t f



• Antimicrobial peptides 4road spectrum antibiotics from plants and

animals

• ualamine ;shar$s=

• /rotegrin ;pigs=

• Magainin ;frogs=

• Antisense agents

Complementary D.A or peptide nucleicacids that binds to a pathogens "irulencegene;s= and pre"ents transcription

The (uture ofChemotherapeutic Agents

lecture 12 -antimicrobial drugs

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