16. Infectious diseases workshop 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 organisms which is initially commensal or mutualistic, but then becomes parasitic such as Candida albicans (oral/vaginal)
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 wall 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 both 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 fission (asexual)
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 have no metabolism of their own, hence anti-microbial agents cannot be targeted towards enzymes.
- They lack 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. Viral particles burst out of the host cell into the extracellular space, leading to the death of the host cell.
b. Viruses aquire an envelope from the host cell on exiting the cell, usually 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 - constant 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
Name TWO characteristic signs / symptoms of cellulitis
Very red, inflamed skin
Fever and malaise-
A patient displays the following signs and symptoms. Which pathology do you suspect?
‘Pustules with round oozing patches and golden yellow crusts that grow larger daily. Mostly affects hands and face or in skin folds’.
Impetigo
Explain why an immune-compromised patient is at increased risk of oral candidiasis.
Candida is an opportunistic infection and when immuno-compromised, the immune system (specifically CD4 cells) do not mount an effective defense.
List TWO causes / triggers of genital candidiasis
- Antibiotic use
- Diabetes Mellitus
- Pregnancy
Describe TWO characteristic signs/symptoms of genital candidiasis
Vaginal / genital itch, discomfort or irritation
Thick, clumpy discharge (cottage cheese)
Describe the rash associated with Lyme disease
A circular pink or red rash at the site of tick attachment that radiates, usually over 5cm diameter.
Name the bacterial cause of ‘diphtheria’
Corynebacterium diphtheriae
Describe the appearance of the tonsils in diphtheria
Grey membrane growing accross the tonsils or pharynx
Explain how complications develop in diphtheria
The exotoxins can cause endothelial necrosis by inhibiting protein synthesis. This can cause myocarditis and paralyse the diaphragm.
The membrane can also block the airways.
Briefly describe the pathophysiology of scarlet fever
Streptococci pyogenes bacteria secrete haemolytic enzymes and exotoxins damaging capillaries and causing red rash.
Describe briefly the difference between a rash associated with ‘scarlet fever’ and ‘meningitis’
The rash in scarlet fever blanches under pressure, unlike the rash in meningitis that is non-blanching
Describe the appearance of the tongue in scarlet fever
Initially white with red papillae,
Later on it has a red raw appearance
Name ONE cranial nerve where the herpes simplex virus (Type I) remains dormant
Trigeminal nerve (V)
Describe the appearance of lesions associated with cold sores
Painful, fluid-filled lesions around the mouth that scab over and then heal.
Using definitions, compare ‘chickenpox’ and ‘shingles’
Chickenpox is a highly contagious viral infection caused by the varicella-zoster virus
Shingles, also known as herpes zoster, is a viral infection caused by the reactivation of the varicella-zoster virus
Describe the distribution of lesions / rash in ‘chickenpox’ and ‘shingles’
Chickenpox: Very itchy vesicular eruptions on mostly the head, neck and trunk.
Shingles the eruptions are usually confined to the affected dermatome.
List ONE serious complication of chickenpox
Encephalitis
Viral pneumonia
Using definitions, compare ‘whooping cough’ and ‘tuberculosis’
Whooping cough is a bacterial infection caused by Bordetella pertussis with characteristic coughing attacks where there is a desperate attempt to breathe in, creating a ‘whooping’ sound.
Tuberculosis is a systemic infection usually caused by pyogenic bacteria (Mycobacterium tuberculosis). It is a chronic granulomatous disease that primarily affects the lungs.
List ONE bacterial cause of whooping cough
Bordetella pertussis
Describe the cough associated with whooping cough
There are characteristic coughing attacks where there is a desperate attempt to breathe in, creating a ‘whooping’ sound.
Describe briefly the pathophysiology of tuberculosis
When first encountered, macrophages in the lungs engulf the bacteria and carry them to the hilar lymph nodes, forming granulomas. In 80% of cases, the granulomas are eliminated by the immune system. In the remaining 20%, the bacteria can become active immediately or later or may remain dormant.
List ONE bacterial cause of tuberculosis
Mycobacterium tuberculosis
Explain why the lungs are a primary target for tuberculosis
M. tuberculosis is an aerobic bacterium, meaning it thrives in environments with high oxygen levels. The lungs provide an oxygen-rich environment.
List TWO signs and / or symptoms more characteristic of tuberculosis
Chronic cough
Purulent / bloody sputum
Describe ‘Koplik spots’ seen in measles
Small grey spots on oral mucosa opposite molar teeth
Name TWO glands affected by the mumps virus
Parotid gland
Testes
List ONE complication of mumps
Testicular inflammation leading to sterility
Name ONE major complication of the ‘rubella’ virus
Abnormal foetal development, miscarriage and death
Describe any TWO signs and / or symptoms associated with viral hepatitis in the following stages:
a. Pre-icteric stage
b. Icteric stage
a. Malaise and diarrhoea
b. Jaundice, pruritic skin, pale stools/dark urine
List ONE serious complication of viral hepatitis
Chronic liver disease (hep. C)
Name THREE viruses that can cause hepatitis
Hepatitis virus type A, B, C, D, E
Name the area of the brain that is affected by the ‘poliovirus’
Anterior horn cells of the CNS
Describe in detail the pathophysiology of Human Immunodeficiency Viral (HIV) infection
HIV virus binds to CD4 receptors, which are found on T-helper cells and macrophages. The viral envelope fuses with the cell membrane and the viral RNA enters the cell. RNA is converted into viral DNA by the enzyme ‘reverse transcriptase’. Using ‘integrase’, it integrates into the host cell DNA and forces the host cell to produce viral RNA and proteins. It assembles in the cytoplasm and buds off, killing more T-cells as the viral load increases.
Name the T-cell affected by HIV
Helper T-Cells (CD4 cells)
Explain why a pregnant woman infected with HIV would choose to:
a. Have a caesarean section
b. Not breastfeed her baby
a. To limit the spread of HIV through blood
b. To limit the possible transmission of HIV through milk
Explain why diagnostic tests for HIV antibodies are often inaccurate in the first 2 weeks to 6 months of HIV infection
There is a delay in the appearance of HIV antibodies in the the first 2 weeks to 6 months.
List TWO signs / symptoms of HIV progression:
a. 1‒6 weeks post infection
b. Late stage
a. Flu / glandular fever-like sore throat; fever; malaise; muscle / joint pain; swollen lymph nodes
b. Recurrent opportunistic infections; Cognitive dementia; Anorexia; Anaemia
Name FOUR opportunistic infections which may occur with HIV infection
Candida (oral, vaginal) Pneumonia Tuberculosis Herpes zoster (shingles) Herpes simplex Kaposi's sarcoma
Describe ONE key difference between ‘HIV’ and ‘AIDS’ (Acquired Immune Deficiency Syndrome)
HIV is a virus that attacks the human immune system and is directly transmissable.
AIDS is the immune suppressed state resulting from HIV, with life-threatening opportunistic infections and is not transmissable
Define dysentery
Dysentery is an infection of the intestines that causes diarrhoea containing blood and / or mucus.
List TWO causes of dysentery
Shigella bacteria
Amoebic (protozoa)
List ONE characteristic sign and / or symptom of dysentery
Diarrhoea with mucus and blood
Describe in detail how malarial infection develops in the human body
- Infected female anopheles mosquito bites human
- Plasmodium parasites are taken up by the liver where they proliferate and mature or lie dormant for up to a year
- They spread to erythrocytes and proliferate further, causing symptoms such as fever
- Infected cells burst and spread infection
- Protozoan gametes are formed and are taken up by mosquito during a blood meal.
Describe the fever associated with malaria
Cyclical fever attacks
-> chills
-> fever (several hours)
-> extreme sweating
-> shivering
List TWO key signs of malaria AND explain why they develop
Jaundice, splenomegaly and hepatomegaly develops due to excessive haemolysis.
Using definitions compare ‘chlamydia’ with ‘gonorrhoea’
Chlamydia is a very common sexually-transmitted infection caused by Chlamydia trachomatis, mostly affecting under-25s.
Gonorrhoea is a very common sexually-transmitted disease caused by Neisseria gonorrhoea bacteria.
Describe TWO signs and / or symptoms in a male affected by chlamydia
Milky-white or yellow discharge from penis
Dysuria due to urethritis
List ONE complication of chlamydia
Pelvic Inflammatory Disease and risk of infertility
Describe THREE keys signs and / or symptoms of gonorrhoea in a female
Yellow vaginal discharge Dysuria Irregular vaginal bleeding Lower abdominal pain Dyspareunia
Name the specific virus that causes genital herpes
Herpes simplex Type II
Describe the lesions associated with genital herpes
Initially painful vesicles, then shallow ulcers
State ONE way in which ‘syphilis’ is transmitted
Sexual contact or damaged skin/mucous membranes
Name the specific virus that causes genital warts
Human papillomavirus (HPV)
Describe the lesions associated with genital warts
Soft, fleshy projections / cauliflower-like masses / small pointed masses / flat lesions on vagina, penis, cervix
