ANTIMICROBIAL DRUGS Flashcards by Scelene Macalintal

Chemicals used to treat microbial infections

ANTIMICROBIAL DRUGS

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resistance that develops through mutation or acquisition of new genes

acquired resistance

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an antimicrobial drug used to treat a disease caused by bacteria

antibacterial drug

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a compound naturally produced by certain molds and bacteria that inhibits the growth or kills other microorganism

antibiotic

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a chemical that inhibits the growth of or kills microorganisms. This terms encompasses antibiotics and chemically synthesized drugs

antimicrobial drug (or antimicrobial)

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a drug that interferes with the replication of viruses. all antiviral drugs are chemically synthesized; none are antibiotics

antiviral drug

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an antimicrobial drug that kills bacteria

bactericidal drug

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an antimicrobial drug that inhibits the growth of the bacteria

bacteriostatic drug

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an antimicrobial that is effective against a wide range of microorganisms often including both Gram-positive and gram-negative bacteria

Broad-spectrum antimicrobial

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a chemical used to treat a disease

chemotherapeutic agent

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resistance due to an inherent characteristics of the microorganism

intrinsic resistance

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an antimicrobial that is effective against a limited range of microorganism

Narrow-spectrum antimicrobial

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A plasmid that encodes resistance to one or more antimicrobial drugs

R plasmid

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a measure expressing the relative toxicity of a chemotherapeutic drug. It is the lowest dose toxic to the patient divided by the dose used for therapy

Therapeutic index

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Cause greater harm to microorganisms than to host

Selective Toxicity

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inhibit growth of microorganisms

Bacteriostatic

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Kill microorganisms

Bactericidal

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Antimicrobial Action

Bacteriostatic; Bactericidal

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kill only limited range

Narrow-spectrum antimicrobial

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kill wide range of microorganisms

Broad-spectrum antimicrobial

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action of one drug enhances the activity of another or vice versa

Synergistic

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activity of one drug interferes with the action of another

Antagonistic

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some people develop hypersensitivities to antimicrobials

Allergic Reactions

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some antimicrobials toxic at high concentrations or cause adverse effects

Toxic Effects

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b-lactam drugs include

penicillins and cephalosporins

very active against non-β-lactamase producing gram+ bacteria.

AMPICILLIN AND AMOXICILLIN

* Used for treatment of meningitis, pneumonia, and septicemia. * Same mech and p’col as that of penicillins.

CEPHALOSPORINS

(for UTI) in case of antibacterial resistance

Cefadroxil

Resistant to inactivation by β-lactamases and used in severe infections (others ineffective)

Cefuroxime

wide range of activity against gram- including Pseudomonas aeruginosa), but is less active than cefurozime against gram+ bact (S aureus).

Ceftazidime

• Not well absorbed orally. • Inhibits peptidoglycan formation. • Active against most gram+ organisms. • I.V. treatment for septicemia or endocarditis caused by MRSA. • Used for pseudomembranous colitis (superinfection of the bowel by Clostridium difficile – produces a toxin that damages the colon mucosa)

VANCOMYCIN

bind to 30S subunit causing it to distort and malfunction; blocks initiation of translation

Aminoglycosides

bind to 30S subunit blocking attachment of tRNA

Tetracyclines

bind 50S subunit and prevents protein synthesis from continuing

Macrolides

used for acute, life-threatening gram- infections. Has synergism with pen and van and combo

Gentamicin

used for bacteria that are gent-resistant

Amikacin

less toxic than gentamicin.

Netilmicin

too toxic for parenteral use. Used for topically for skin infections and orally for sterilizing bowel before surgery.

Neomycin

active against Mycobacterium tuberculosis. But because of its ototoxicity, rifampicin replaces

Streptomycin

resistance develops quickly alone; so, with TB, combine with isoniazid, ethambutol, and pyrazinamide for the 1st 2 mos of treatment, followed by another 4 mos with rifampicin and isoniazid

Rifampicin

* Very safe drugs. | * Usually given orally.

MACROLIDES

macrolides example drugs

Erythromycin and clarithromycin

in high doses, may cause nausea and vomiting

Erythromycin

very long t1/2 (~40-60 hr) and a single dose is as effective in treating chlamydial non-specific urethritis as tretracycline admin over 7 days,

Azithromycin

• Broad-spectrum. • Penetrate microorganisms well. • Sensitive organisms accumulate it through partly passive diffusion and partly through active transport. • Resistant organisms develop an efflux pump and do not accumulate the drug. • Genes for tet-resistance transmitted by plasmids. • Closely assoc with those for other drugs to which the organisms will also be resistant (e.g., sulphonamides, aminoglycosides, chloramphenicol). • Tets bind to Ca in growing bones and teeth → can discolor teeth. So, should be avoided in children < 8 yrs old

TETRACYCLINES

• Broad-spectrum. • Serious side-effects: bone marrow aplasia, suppression of RBCs, WBCs, encephalopathy, optic neuritis. • So, periodic blood counts required, especially in high doses. • Large Vd, including CNS. • Inhibits the actions of other drugs and may increase the actions of phenytoin, sulphonylureas, and warfarin. • Neonates cannot met the drug rapidly → accumulation →‘grey baby’ syndrome (pallor, abdominal distension, vomiting, and collapse

CHLORAMPHENICOL

inhibit enzymes that maintain the supercoiling of closed | circular DNA

Fluoroquinolones

block prokaryotic DNA-dependent RNA polymerase from initiating transcription

Rifamycins

well-absorbed orally. Used to treat UTIs.

Sulfadiazine

SULPHONAMIDES- Adverse effects

allergic rxns, skin rashes, fever

used for UTIs and Resp TIs

Trimethoprin

used mostly for pneumonia, | neocarditis, and toxoplasmosis

Co-trimoxazole (trimethoprin + sulfamethoxazole)

• Inhibit DNA gyrase. • Nalidixic acid – used only for UTIs. • Ciprofloxin (6-fluoro substituent) that greatly enhances its effectiveness against both gram- and gram+ bacteria. • Well-absorbed both orally and I.V. • Eliminated largely unchanged by the kidneys. • Side-effects (headache, vomiting, nausea) are rare; but convulsions may occur

QUINOLONES (GABA ANTAGONISTS)

against anaerobic bacteria and protozoan infections

Metronidazole

longer duration of action

Tinidazole

Diffuses into the organism where the nitro group is reduced → chemically reactive intermediates are formed that inhibit DNA synthesis and/or damage DNA

5-NITROIMIDAZOLES

binds to membrane of G- bacteria and alters permeability • This leads to leakage of cellular contents and cell death • These drugs also bind to eukaryotic cells to some extent, which limits their use to topical applications

Polymyxin B

nterferes with replication of influenza A by inhibiting the transmembrane M2 protein that is essential for uncoating the virus Has a narrow spectrum; so, flu vaccine is usually preferable

Amantadine

– inhibits both influenza A and B neuraminadase. Decr duration of symptoms if given within 48 hr of the onset of symptoms. Prophylactic in healthy adults.

Zanamivir

Human Ig contains specific Abs against superficial Ags of viruses → can interfere with their entry into host cells. Protection against hepA, measles, and rubellla (German measles)

Immunoglobulins

used to treat genital herpes

Acyclovir

used for treatment of cytomegaloviral infections of the eye

Cidofovir

used to treat Hepatitis B

Lamivudine

• HSV and VZV contain a thymidine kinase (TK) that → acyclovir to a monophosphate ---→ phosphorylated by host cell enzymes to acycloguanosine triphosphate, which inhibits viral DNA pol and viral DNA synthesis. • Selectively toxic (TK of uninfected host cells activates only a little of the drug). • Viral enzymes have a much higher affinity than the host enzymes for the drug. • Effective against HSV, but does not eradicate them. • Need high doses to treat shingles.

ACYCLOVIR

• Quite toxic (neutropenia) –so, given only for severe CMV infections in immunosuppressed patients. • CMV is resistant to acyclovir because it does not code for TK

GANCICLOVIR

Currently implies a drug used to treat HIV

ANTIRETROVIRALS

nucleotide reverse transcriptase inhibitor

Tenofovir

- nucleoside analog – inhibits RT of HIV and is only used orally for AIDS

Zidovudine

- inhibitors of the enzyme neuominidase Used to treat influenza

Zanamivir (Relenza) and Oseltamivir phosphate (Tamiflu)

protease inhibitors. Inhibit the synthesis of essential viral proteins (e.g., RT) by viral-specific proteases.

Indinavir

• Cells infected by a virus often produce interferon, which inhibits further spread of the infection

Interferons

drug for treatment of viral hepatitis infections

Alpha-interferon