Infections Flashcards
(33 cards)
Explain the difference between primary and secondary immunodeficiency (2)
Primary immunodeficiencies are genetic defects of the immune system that result in impaired immune function. The defects are present from birth. Secondary immunodeficiencies are acquired – see below.
Any 4 of: HIV infection, Haematological malignancies (esp. leukaemias), Chemotherapy for cancer, Certain autoimmune diseases, Immunosuppressive drugs (e.g. for transplantation, corticosteroids), Malnutrition, Diabetes, Extremes of age. Note: “Stress” was accepted but is a rather marginal cause of immunodeficiency.
List four (4) causes of secondary immunodeficiency (2)
Any 4 of: HIV infection, Haematological malignancies (esp. leukaemias), Chemotherapy for cancer, Certain autoimmune diseases, Immunosuppressive drugs (e.g. for transplantation, corticosteroids), Malnutrition, Diabetes, Extremes of age. Note: “Stress” was accepted but is a rather marginal cause of immunodeficiency.
State what the definitive treatment for Severe Combined Immunodeficiency Syndrome is. Give a reason for this (1)
Bone marrow transplant/ haemopoetic stem cells (½). Because all stem cells originate in the bone marrow (½)
Define the term “opportunistic infection” (2)
Not usually capable of causing disease in healthy individuals (1) as it is of low virulence (1)
Name two (2) fungal organisms that can typically cause lung infection in immuno-compromised patients (2)
Aspergillus species, Pneumocytis jirovercii
Outline the role that normal/indigenous flora plays in the human body (5)
Variety of organisms (½), associated with particular ecological niche (½)
Helps maintain environment (½) and prevent infection with other organisms (½)
Occupy epithelial surfaces (1)
Compete for essential nutrients (1)
Secrete inhibitory substances ‘bactericidins’ that inhibit/kill pathogens (1)
Define mucositis associated with malignancies and briefly explain how it is associated with infection (3)
Chemotherapy/radiotherapy causes damage to the integrity of mucosa with inflammation (1), this may cause translocation of GIT bacteria (1) thus leading to systemic infection (1)
State the term used for infections that are more likely to occur in an immunocompromised patient. Name three (3) such infections that are commonly seen in South African patients (2)
Opportunistic infections (½) TB, cryptococcal infection, pneumocystis, toxoplasma, CMV (½ each)
Define the term “opportunistic infection” (2)
An infection caused by an organism that seldom if ever causes infection in an immunocompetent person, but can cause infection in people whose immune systems are not functioning normally.
Define the term “opportunistic pathogen” (2)
Not usually capable of causing disease in healthy individuals (1) as it is of low virulence (1)
Name in full three (3) opportunistic pathogens (NB), as well as an appropriate agent for the treatment of the organism (4½)
Pneumocstis jirovecii (carinii) Cotrimoxazole
Cryptococcus neoformans Amphotericin B, fluconazole
Toxoplasma gondii Cotrimoxazole
Mycobacterium avium-intracellulare Clarithrpmycin, ethambutol
Cryptosporidium parvum No specific therapy, but restoration of immune function important e.g. with ARVs)
Isospora belli Cotrimoxazole
Name one typical bacterial (full name) and fungal (mould) opportunist typically found in patients with (2)
Pseudomonas aeruginosa (1), Aspergillus spp. (1)
The Herpes virus family as a whole are a common cause of opportunistic disease. Briefly explain why this is so (2)
These viruses are ubiquitous (almost everyone is infected). They cause life-long latent infections and can reactivate in the face of immunosuppression (and other stresses).
Members of the herpesvirus family commonly cause disease in immunosuppressed patients. Explain why this happens despite measures to prevent exposure to pathogens (2) (NB)
Herpes virus infections are common and once individuals have been exposed, the virus establishes a lifelong latent infection. They commonly reactivate in immunosuppressed patients. Reactivation in an immunosuppressed patient may be associated with life threatening infection.
List three (3) herpesviruses and name a complication that each virus can cause in an immunosuppressed patient (3) (NB)
VZV Shingles
CMV Retinitis, encephalitis, enteritis, etc
EBV Pre-malignant lymphoproliferative disorders, non-hodgkin’s lymphoma
HHV8 Kaposi sarcoma
List two (2) serious cytomegalovirus infections causing end-organ disease in immunocompromised patients (2x1 = 2)
Interstitial/ hypoxic pneumonia, Retinitis, Gastrointestinal ulceration, Neurological disease
Certain malignancies are common in HIV infection. Outline the role that HIV plays in their pathogenesis (3)
HIV is not oncogenic. It causes immuno-suppression which increases the chances of viral persistence and expansion of persistently infected cells. This increases the chance for infected cells to acquire additional mutations and undergo malignant transformation.
Despite his very high white blood cell count, a leukaemia patient may still be susceptible to infections. Briefly explain why this is so (2)
He has abnormal white blood cells, which despite being numerous, do not function normally
Define mucositis associated with malignancies and outline how is it associated with infection (2)
Chemotherapy/radiotherapy causes damage to integrity of mucosa with inflammation (1), this may cause translocation of GUT bacteria thus systemic infection (1)
Bacteria, fungi and viruses can cause infection in patients following stem cell transplant. State one example of each organism (1½)
Bacteria: Pseudomonas aeruginosa, Fungi: Candida/aspergillus, Viruses: Herpes simplex/cytomegalovirus
Name in full the organism that most commonly causes oral thrush (1)
Candida albicans
Oral cavity, GIT, skin, genital tract
This organism is usually a commensal. Outline, using examples, different mechanisms by which this organism can breach host defences and cause clinical disease (1½)/ Describe its pathogenesis (1½)
- If immune system is compromised through chemotherapy, HIV, diabetes, C.albicans may cause local infection
- If normal flora is disturbed through antibiotics, C.albicans may cause local infection
- Trauma, or indwelling devices may result in C. albicans local infection
State the full name of the organism most likely responsible for the above condition and state what type of organism it is (2)
Candida albicans, fungus, yeast
State what chemotherapeutic agent may be used to treat Ms Jones infection (1) [candida]
Nystatin lozenges, clotrimazole, fluconazole
