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
Provide the correct terminology for:
a. Location the pathogen exists, reproduces and spreads to new hosts
b. Infected individuals who are asymptomatic
c. Intermediate carrier, transporting pathogens from reservoir to host
d. An infected person or animal
a. Reservoir
b. Carrier
c. Vector
d. Host
Explain what is meant by ‘nosocomial’
Infections contracted solely in a medical setting such as hospitals or care homes
Describe in detail the FOUR stages of infection
- Incubation - Time interval between the initial exposure to the infecting organism and the appearance of the first signs/symptoms
- Prodromal period - Interval from non-specific symptoms (malaise, fever, fatigue), to more specific acute symptoms
- Acute period - Period with very pronounced symptoms specific to the disease
- Chronic infection - Infection with insidious/slow onset and of long duration
List FOUR ways in which a host can provide resistance against microbes
- Intact skin & mucous membranes
- Body secretions [stomach acid, tears etc.]
- Phagocytosis
- Interferon production
- Effective immune system
- Effective inflammatory response
List FOUR ways in which a microbe displays ‘virulence’ against a host
- Production of invasive / destructive enzymes
- Production of endo- or extotoxins
- Spore formation
- Ability to mutate [eg. MRSA, HIV]
- Presence of bacterial capsule
- Entry of large numbers of organisms [CFUs]
State THREE methods to reduce the spread of infection
- Reduce the reservoir
- Stop droplet transmission by covering the mouth
- Block the method of transmission (hand washing etc.)
- Kill the organism
- Sterilisation
Explain how the following ‘infection control’ processes work:
a. Sterilisation
b. Pasteurisation
a. All micro-organisms and their spores are destroyed with 30 minutes of hot air (180 degrees) or steam (120 degrees) for 20 minutes.
b. Kills most pathogenic microbes, but not spores. Heat up to 71.7 degrees for 15 to 25 seconds.
With regards to natural anti-microbials, name TWO examples for each of the following:
- Anti-bacterial
- Anti-fungal
- Anti-viral
- Anti-parasitic
- Oregano; Grapefruit seed extract; Aloe Vera; Calendula
- Garlic; Oregana; Caprylic acid; Cinnamon
- Elderberry; Olive leaf; Lemon balm; Pau D’Arco
- Black walnut; Wormwood; Berberine; Goldenseal
Explain briefly how ‘sepsis’ develops in the body
Sepsis develops when a pathogen has infected the blood and when the body’s response to the infection causes injury to the body’s own organs, potentially leading to multi-organ failure.
List TWO groups of individuals at higher risk of developing sepsis
The elderly and the very young
Alcoholics
Diabetics
Chemotherapy patients
Using definitions, describe the difference between ‘cellulitis’ and ‘erysipelas’
Cellulitis is a bacterial skin infection causing inflammation of dermal and subcutaneous layers.
Erysipelas is a more superficial bacterial skin infection of the dermis and upper subcutaneous layer, producing a well-defined edge.
List ONE bacterial cause of cellulitis
Staphylococcus Aureus
streptococci