16. INFECTIOUS DISEASES Flashcards
Define ‘pathogenic’
Pathogenic is the ability to cause disease
Define and give an example of a commensal microbial relationship
A commensal relationship is one in which one organism benefits and the other is unaffected such as microbes on human skin.
Define and give an example of an opportunistic microbial relationship
A symbiotic relationship between orginisms which is initially commensal or mutualistic, but then becomes parasitic such as candida albicans in the intestines/mouth
In which way is the relationship between humans and E. Coli mutualistic?
E. coli make vitamin K for humans
Describe the difference between ‘Pasteur’ and ‘Bechamp’ theories
Pasteur formulated the ‘germ theory’ of disease in which he proposed that germs are all bad and cause disease. Bechamp proposed the ‘terrain theory’ in which he says that germs are opportunistic in nature and live with us symbiotically and that we should promote health instead of killing germs.
Are bacteria prokaryotic or eukaryotic?
Prokaryotic - their cell structure is simple and they have no nucleus or membrane-bound organelles
List TWO differences between ‘gram-negative’ and ‘gram-positive’ bacteria
Gram-positive bacteria have a thick mesh-like cell wal made of peptidoglycan and stains purple with Gram’s method.
Gram-negative bacteria have a thinner cell wall with an additional outer lipid-rich membrane and it stains pink with Gram’s method.
Describe TWO key differences between ‘exotoxins’ and ‘endotoxins’
Exotoxins are released by gram-positive and negative bacteria and it is released by living microbes and is very toxic. Endotoxins are only released from the cell wall of gram-negative bacteria when they die and is usually less toxic.
Name ONE method by which bacteria reproduce
Binary fissure
With regards to resident and transient microflora, list:
a. Two body locations where microflora is present
b. Two body locations where microflora is absent
a. Small and large intestine, mouth, nasal cavity, skin, vagina, perineum
b. Blood, CSF, lungs, stomach, uterus, ovaries, bladder, kidneys
Describe how microflora organisms can become pathogenic
If the local environment changes or the immune system becomes compromised.
Explain how broad-spectrum antibiotics affect microflora in the body
Broad-spectrum antibiotics have no specificity for the bacteria they are taken to kill, and can have devastating effects on the body’s microflora by killing the good flora and disrupting the balance.
List TWO adverse effects of broad-spectrum antibiotics
Candida overgrowth
Impaired immunity
Higher risk of asthma and IBD
Colds, flu, cold sores
Describe the structure of a virus
A virus consists of a strand of DNA or RNA enclosed in a hard protein coat (capsid) unique to that virus.
Name two DNA viral pathologies
Varicella zoster, herpes, smallpox
Name two RNA viral pathologies
HIV, mumps, measles
Describe how viruses reproduce
Viruses reproduce by injecting their RNA or DNA into a living host cell and uses that cell’s apparatus for reproduction
Describe FOUR ways in which viruses make it difficult for the body to identify and destroy
- Viruses hide within the host cell and can be latent
- Viruses do not have a metabolism of their own, hence anti-microbial agents cannot be targeted towards enzymes.
- They do not have many structures of their own
- They are able to mutate to avoid host immune response.
Explain the following terms:
a. Viral lysis
b. Viral budding
c. Latent stage
a. Viruses need a living host cell for replication and do this through viral lysis, where viral particles burst out of the host cell into the extracellular space, leading to the death of the host cell.
b. Viruses use the process of budding, where they exit the cell and aquires an envelope from the host cell, usually also leading to host cell death.
c. Stage of infection where the disease is present, but hidden and inactive.
Describe how the following promote fungal growth in the body:
a. Yeasts
b. Dermatophytes
a. Yeasts are single-celled fungi that reproduce by budding e.g. Candida albicans
b. Dermatophytes are fungi causing skin disease and they obtain nutrients from keratin in the skin. They colonise the stratum corneum and are dependent on humans e.g. ringworm or tinea
List FOUR factors that promote growth of fungi in the body
- Warmth
- Moisture
- Acidity
- Rich nutrition
List TWO ways in which fungi reproduce
- Asexual reproduction: occurs via budding. The extension of the hyphae contains cromatin and develop into an independent organism
- Sexual reproduction: occurs via the formation of fungal spores and is less common
Name ONE example of a protozoa
Plasmodium (malaria parasite)
Define the following terms:
Epidemic
Pandemic
Endemic
Epidemic - infection in a large group of individuals
Pandemic - worldwide infection
Endemic - infection restricted to an area