Antimicrobial Drugs Flashcards by soad auf

Why chemotherapy

To overcome diseases that the body defenses could not

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Difference between disinfectants and antimicrobial drugs

Both interfere or kill microbes growth
Only antimicrobial drugs act within the host without damaging the host

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The threat

Some staphylococcus strains or resistant to all antibiotics
TB is resistant to all antibiotics
Women’s death due to a bacteria resistant to all antibiotics

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Most antibiotics are from

Streptomyces bacteria that live in soil

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Why is it harder to develop antibiotics for eukaryotes

Due to the similarity between the cellular structure of both the host and the pathogen
Usually harms the host too

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Eukaryotic pathogen examples

Fungi,protozoa,helminth

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Narrow vs broad spectrum

Narrow>penicillin gram +ve
Broad>tetracycline both

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Antimicrobial drugs action 5

Inhibiting cell wall synthesis
Injury to plasma membrane
Inhibiting protein synthesis
Inhibiting nucleic acid synthesis
Inhibiting essential metabolites synthesis

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Cell wall synthesis inhibition

Penicillin> prevent cell wall synthesis by preventing peptidoglycan formation causing lysis
Affects growing cells only
No effect on host

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Injuring the plasma membrane
Ionophores

Change in permeability causing loss of metabolites and uncontrolled movement of cations
Antifungal by binding to sterols
Not bacteria as no sterols

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Inhibiting protein synthesis

Targets ribosomes 70S will damage host as mitochondria has 70s ribosomes
Chloramphenicol>50S inhibits peptide formation
Streptomycin>30S, incorrect mRNA reading
Tetracyclines>incorrect tRNA and mRNA attachment

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Inhibition of essential metabolite synthesis
Catabolism/anabolism

Sulfanilamide and PABA (para aminobenzoic acid substrate)
Competitive inhibitor/allosteric inhibitor

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Do ribosomes synthesize proteins?

No only assembles amino acids

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Microbiota
Microbiome

Microorganisms
Microorganisms ecosystem

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Symbiosis types

A relationship between 2 organisms were at least 1 benefits
*Commensalism only bacteria benefits host unaffected
*Mutualism, both host and bacteria benefited
*Parasitism, only bacteria benefited host damaged by endotoxins and exotoxins that cause disease

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Lovely bacteria and where to find them

Skin>guard/immunity/wound healing
Gut>enzymes to digest/nutrient extraction
Intestine>vitamins(B12)/ hormones/medecine digestion

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Pathogenicity vs virulent

Pathogenicity is the ability to cause disease
Violent is the degree of pathogenicity

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Pathogens in body
First steps

Portals of entry(nose/mouth/injury)
Adhesion by adhesins on glycocalyx,flagella,pilli

Penetration modes

Formation of capsules
Specific cell wall components
Enzymes
Antigenic variation
Biofilm formation

Capsules

Highly viscous prevents phagocytosis
Allows adhesion
Increases virulence
Human body can produce antibodies against capsules and phagocyte the bacteria

Examples of bacteria with capsules

Streptococcus pneumonia
Klebsiella pneumonia
Haemophilus influenzae

Cell wall components

M proteins that are heat and acid resistant
Streptococcus pyogenes
Resist phagocytosis
Increase virulence

Enzyme production

Coagulase enzyme that coagulates blood fibrinogen into fibrin
Isolates bacteria and protect from phagocytosis

Antigenic variation

Antigens usually receive antibodies from the host to inactivate them and perform phagocytosis
Some bacteria alter its surface antigens to become unaffected by antibodies
Influenza virus

Biofilm formation

Community of bacteria Thin, slimy layer Sharing of nutrients Shelter from environmental factors Adhesion

Why biofilm harmful

Bacteria become resistant to phagocytosis, by preventing phagocytes movement as they are very viscous. Shielding of antigens by EPS

What is EPS of biofilms

Extracellular polymeric substance

Biofilm vs capsule

Capsule is 1 cell's sugar coat Biofilm is numerous cells sugar coat

How do bacteria damage the host

Using the host nutrients Producing toxins

Siderophores / iron chelators

Bacteria require iron They get it from the host by producing siderophores proteins to take iron from iron transport proteins like haemoglobin by binding to iron more tightly

Toxin production

Poisonous Transported by blood/lymph Inhibit protein synthesis, destroy blood cells, disrupt nervous system, blood vessels destroy

Capacity of microorganism to produce toxins

Toxigenicity

Types of toxins virulence

Endotoxins>low virulence Exotoxins>high virulence

Exotoxins What are they

Into surrounding medium or after host cell lysis Proteins+enzymes for certain biochemical reactions Part of metabolic growth released during log phase

Why can exotoxins easily diffuse into the body

As they are soluble

How exotoxins work 3

By destroying parts of host cells Inhibiting protein Synthesis Inhibiting metabolic functions

Exotoxins are highly..... Lethal

Specific and most lethal 1 mg of botulinum exotoxin can kill 1 million guinea pigs

Diseases by bacteria that produce exotoxins are due to

Minute amount of exotoxins not the bacteria itself

Endotoxins are ....not...

Part of outer membrane of gram negative cell wall A metabolic product

Endotoxins are....while exo toxins are ..

Endotoxins are lipids(lipopolysaccharide LPS) lipid A Exotoxins are proteins+ enzymes

Why antibiotics targeting gram negative bacteria cause immediate worsening of the symptoms

As they lyse the bacteria causing the release of endotoxins that are then broken down by lipase enzyme in the liver

Endotoxins signs

All have the same signs but different degrees Fever,weakness,death

Comparison bet endotoxins and exotoxins Bacteria What are they When Stability Toxicity Fever producing

Exotoxin,,,,endotoxin Gram +ve and -ve,,,, only -ve Proteins,,,lipids(lipid A of LPS) Metabolic growth,,,cell lysis Unstable,,stable High,,low No,,yes

Which toxin is specific for particular cellular structures

Exotoxin