Week 7 Identification and treatment of microorganisms

Question 1

How can bacteria be identified

Answer 1

• clinical samples grown on agar plates
• using bacteria specific characteristics (gram stains, aerobic/anerobic) - use dichotomous keys

Question 2

How are viruses identified

Answer 2

Diagnosed by blood test because viruses live inside of cells, and if the infection has been there for a while antibodies would be present, and you may also be able to identify the viral particles in the blood

Question 3

How are funguses identified

Answer 3

• Fungal infections are superficial and usually lie on the skin so samples can be taken and grown or looked under a microscope.
• Light microscopy of stained or unstained preps

Question 4

How are protozoa identified

Answer 4

• easily seenby light microscopy using certain stains e.g. Trichrome

Question 5

def cidal activity

Answer 5

antimicrobial that kills the organism

Question 6

def static activity

Answer 6

antimicrobial that inhibits the growth of an organism

Question 7

what are the types of antimicrobial range of activity

Answer 7

• Broad spectrum antibiotics are effective against a wide variety of organisms
• Narrow spectrum antibiotics are only effective against a limited number of organisms
  (narrow spectrum is preferred to not damage the rest of the host cells)

Question 8

What is the concept of selective toxicity

Answer 8

Selective toxicity refers to the ability of a substance to selectively target and inhibit or kill specific organisms or cells while causing minimal harm to others.

This is achieved by the drug targeting specific differences which is only found in the specific microorganism which is being targeted.

Question 9

What are the 4 main target sites for antibacterial drugs

Answer 9

1. Cell wall synthesis
2. Protein synthesis
3. Nucleic acid synthesis
4. Cell membrane function

Question 10

How is cell wall synthesis targeted by antibacterial drugs

Answer 10

In bacteria drugs target peptidoglycan as it is a major component of bacteria and not present in humans. It’s more effective in gram positive than gram negative as gram positive has a greater amount of peptidoglycan
e.g. penicillin weakens the cell wall leading to lysis

Question 11

How is protein synthesis targeted by antibacterial drugs

Answer 11

Protein synthesis is essential for bacterial growth and replication. Antibacterial drugs that target protein synthesis interfere with the bacterial ribosome, the cellular machinery responsible for translating mRNA into proteins.

e.g. Prokaryote Ribosomes - they interfere with binding of mRNA to ribosome or translation

Question 12

How is nucleic acid synthesis targeted by antibacterial drugs

Answer 12

Nucleic acid synthesis is necessary for bacterial DNA replication and RNA transcription. Antibacterial drugs that target nucleic acid synthesis interfere with DNA replication or RNA transcription processes.
Example
- Fluoroquinolones: Fluoroquinolones inhibit bacterial DNA gyrase and topoisomerase IV enzymes, which are involved in DNA replication and supercoiling, leading to DNA strand breaks and inhibition of DNA synthesis.

Question 13

How is cell membrane function targeted by antibacterial drugs

Answer 13

Bacterial cell membranes maintain the integrity of the cell and regulate the passage of molecules in and out of the cell. Antibacterial drugs that target cell membrane integrity disrupt the structure or function of the bacterial cell membrane.

polymixins e.g. Colisitn

• Bind to LPS and interact with phospholipids in the outer and inner membranes hence is only effective against gram negative bacteria

Question 14

What are the drug target sites for fungus

Answer 14

• cell membrane
• b-glucan synthesis

Question 15

What are the drug target sites for viruses

Answer 15

• stages of life cycle e.g. release of new virions

Question 16

How does drug resistance occur

Answer 16

• innate/intrinsic - inherent characteristics of microorganisms that make them naturally less susceptible to certain antimicrobial agents

Acquired - developed after exposure or spontaneous mutation or horizontal gene transfer

Question 17

What are the mechanisms of resistance (4)

Answer 17

• altered target
• alteration in access to the target site (altered uptake)
• Drug inactivation
• Horizontal gene transfer

Question 18

Explain altered target as a mechanisms of resistance

Answer 18

The drug has target molecules such as enzymes or receptor, and the active sites of the enzyme or receptor may of been modified into different shapes where the drug no longer fits and inhibits

Question 19

Explain alteration in access to the target site (altered uptake) as a mechanisms of resistance

Answer 19

Decreased permeability - the cell wall is modified and the drug cannot pass into the cell
gram negative contains porins which are pores in the outer membrane which can close making it harder for antibiotics to reach the membrane or cell

-Active transport which removes the antibiotic such as efflucx pumps that actively pump antimicrobial agents out of the cell

Question 20

Explain drug inactivation as a mechanisms of resistance

Answer 20

Microorganism may contain an antibiotic degrading enzyme which destroys or inactivates the drug.

e.g. beta-lactamases inactivates beta lactams

Question 21

Explain horizontal gene transfer as a mechanisms of resistance

Answer 21

Microorganisms can acquire resistance genes from other microorganisms through processes such as conjugation, transformation or transduction

These resistance genes may encode efflux pumps, enzymes or altered target proteins that confer resistance to antimicrobial agents.