Infection & Immunology Flashcards
What is an Abscess
A painful collection of puss usually caused by bacterial infection
What are the 2 types of Abscess
Skin Abscess - Common - IV drug use is a major RF
Internal Abscess
What are signs and symptoms of Abscesses
Swollen pus-filled lump under the surface of the skin with associated fever and chills
Internal abscesses are not visible but are characterised by:
- Pain in the affected area
- Swinging fevers
- Malaise
How are Abscess investigated
Ultrasound can be used in visualising and abscess
How are abscesses treated
- Some small skin abscesses may disappear by themselves
Incision and Drainage
- Before doing this, check to see whether a foreign object is causing the abscess (e.g. needle fragments in IV drug users)
- The abscess is cut open and drained of pus (Do not do in non-lactational mastitis)
Antibiotics
- Can be used alongside incision and drainage
What is Anaphylaxis
Acute life-threatening multi system syndrome caused by sudden release of mast cell and basophil-derived mediators into the circulation
What are the causes of Anaphylaxis
Immunogenic: IgE-Mediated or immune complex/complement-mediated
Non-immunogenic - Mast cell or basophil degranulation without the involvement of antibodies (Vancomycin, codeine and ACEi)
Common Allergens:
- Drugs (Penicillin)
- Latex
- Peanuts
- Shellfish
What are the signs and symptoms Anaphylaxis
Tachypnoea Wheeze Cyanosis Swollen upper airways and eyes Rhinitis Conjunctival infection Urticarial rash Hypotension Tachycardia
How is Anaphylaxis diagnosed
Clinical diagnosis
Serum tryptase level - Elevated
Serum Histamine levels
IgE immunoassays
How is Anaphylaxis treated
ABCDE
- High flow oxygen
- IM adrenaline
- Chlorpheniramine (antihistamine)
- Hydrocortisone
- If continued respiratory deterioration, may require bronchodilator
- Monitor pulse oximetry, ECG, BP
How is HIV transmitted
Sexual intercourse:
- Heterosexual intercourse is the most common mode
- Homosexual are the greater risk in the West
Blood (and other bodily fluids):
- Mother of child (Interuterine, childbirth, breast-feeding)
- Needles
- Blood transfusions
- Organ transplantation
What are the 3 phases and associated symptoms and signs of HIV
- Seroconversion phase:
- Self-limiting
- Fever
- Night sweats
- Generalised lymphadenopathy
- Sore throat
- Oral ulcers, rash, myalgia, headache, encephalitis, diarrhoea - Early/Asymptomatic phase:
- Apparently well
- Some may have persistent lymphadenopathy
- Progressive minor symptoms - AIDS
- Syndrome of secondary diseases resulting from immunodeficiency
What are the signs and symptoms of HIV in the AIDs phase
Direct effect:
- Neurological: Polyneuropathy, dementia
- Lung: Lymphocytic interstitial pneumonitis
- Heart: Cardiomyopathy, myocarditis
- Haematological: Anaemia, thrombocytopenia
- GI: Anorexia, wasting
- Eyes: Cotton wool spots
Secondary effects resulting from immunodeficiency:
- Bacterial: TB, Skin infections, pneumococcal infections
- Viral: CMV, HSV, VZV, HPV, EBV
- Fungal: Pneumocystic jiovecii pneumonia, Crypotococcus, Candidiasis, Invasive aspergillosis
- Protozoal: Toxoplasmosis, Cryptosporidia
- Tumours: Kaposi sarcoma, SCC, Lymphoma
How is HIV diagnosed
HIV testing: HIV antigen/antibody (6 week window period - False negative)
PCR for viral RNA
CD4 count
Viral load
- Pneumocystic pneumonia - CXR
- Cryptococcal meningitis - brain CT or MRI, LP
- CMV (colitis) - colonoscopy and biopsy
- Toxoplasmosis - brain CT or MRI
- Cryptosporidia - stool
microscopy
What is Infectious mononucleosis
This is the clinical syndrome caused by primary EBV infection - Glandular fever
Describe the infection pattern seen in Infectious mononucleosis
It is transmitted by close contact (e.g. kissing, sharing eating utensils)
Atypical lymphocytes in the peripheral blood are a classic feature of Infectious mononucleosis.
EBV remains latent in lymphocytes. Reactivation may occur following stress or immunosuppression
Who is commonly affected by Infectious mononucleosis
1-6yrs
14-20yrs
What are the signs and symptoms of Infectious mononucleosis
Incubation period of 4-8 weeks
Abrupt onset of symptoms:
- Sore throat
- Fever
- Fatigue
- Headache
- Malaise
- Anorexia
- Sweating
- Abdominal pain
- Oedema and erythema or the pharynx
- White creamy exudate on the tonsils
- Palatal petechiae
- Cervical/generalised lymphadenopathy
- Splenomegaly
- Hepatomegaly
- Jaundice
- Widespred maculopapular rash
How is Infectious mononucleosis diagnosed
EBV-specific antibodies
+
Heterophile antibodies - Non-specific for EBV infection
= Diagnostic
Real-time PCR - Expensive but good
How is Infectious mononucleosis treated
- Bed rest
- Paracetamol and NSAIDs - Fever and malaise
- Corticosteroids in severe cases
- No not give ampicillin or amoxicillin if Infectious mononucleosis is suspected - nearly 100% of patients with glandular fever develop a maculopapular
- Avoid contact sports for 2 weeks (because of risk of rupturing spleen)
What are complication to Infectious mononucleosis
- Lethargy for several months
- Respiratory obstruction and secondary infection
- Haemolytic or aplastic anaemia, thrombocytopenia
- Splenic rupture, fulminant hepatitis, pancreatitis, mesenteric adenines, renal failure
- CNS - GBS, Encephalitis, Viral meningitis
- EBV-associate malignancy - Burkitt’s lymphoma, nasopharyngeal cancer, Hodgkin’s lymphoma
What is Rheumatic fever
This is an autoimmune disease that may occur following group A streptococcal throat infection. It can affect multiple systems including, joints, heart, brain and skin.
What are signs and symptoms of Rheumatic fever
Fever Joint pain Recent sore throat Chest pain SOB Palpitations Heart murmur - MR Pericardial rub Signs of cardiac failure Swollen joints
How is Rheumatic fever diagnosed
It is diagnosed using the Jones criteria. There must be a recent strep infection plus 2 Major criteria, or 1 major and 1 minor.
Evidence of a group A strep infection:
- Positive throat culture (Usually negative by the time RF symptoms appear)
- Rapid streptococcal antigen test +ve.
- Elevated or rising streptococcal antibody titre (eg anti-streptolysin O (ASO) or
DNase B titre).
- Recent scarlet fever.
Major:
- Carditis: Tachycardia, Murmurs, Pericardial rub, CHF, Cardiomegaly, Conduction defects (45–70%)
- Arthritis: A migratory, ‘flitting’ polyarthritis; usually affects larger joints (75%)
- Subcutaneous nodules: Small, mobile, painless nodules on extensor surfaces of joints and spine (2–20%)
- Erythema marginatum: Geographical-type rash with red, raised edges and clear centre; occurs mainly on trunk, thighs and arms (2–10%)
- Sydenham’s chorea (St Vitus’ dance): Occurs late in 10%. Unilateral or bilateral involuntary semi-purposeful movements. May be preceded by emotional lability and uncharacteristic behaviour.
Minor criteria:
- Fever.
- Raised ESR or CRP.
- Arthralgia (but not if arthritis is one of the major criteria).
- Prolonged PR interval (but not if carditis is major criterion).
- Previous rheumatic fever.
What is Neutropenic sepsis
The development of sepsis in s patient with neutropenia
Diagnostic criteria:
- Temperature > 38 degrees
- Neutrophil count < 0.5
Neutropenic shock is possible without a fever as patients may be on antipyretic drugs or steroids
What are cause of neutropenic shock
Incidental Neutropenia:
Congenital
- Ethnic variation
- Cyclical neutropenia in children
Acquired
- Decreased/ineffective neutrophil production: Bone marrow infiltration, Aplastic anaemia, B12/folate deficiency, chemotherapy, radiotherapy
- Felty’s syndrome
- Hypersplenism
- Malaria
Others
- Toxoplasmosis
- Dengue fever
Febrile neutropenia: Temperature over 38.5 or over 38 for 2 hours and an absolute neutrophil count < 0.5
What are the signs and symptoms of Neutropenic sepsis
Check history for:
- High risk features: Active cancer, recent chemo, use of immunosuppressants or immunosuppressive illness
- CKD
- Recent blood products
- Intravascular devices
Examination findings:
- Signs of infection
- Fever
- Features of IE
- Lymphadenopathy
- Skin rashes
How is Neutropenic sepsis diagnosed
FBC: Neutrophils <0.5
Blood cultures: Positive for causative organism
Others - Blood film, D-dimer (for DIC), U&Es, creatinine, LFTs
What is Necrotising fasciitis
A life-threatening infection of subcutaneous soft-tissue that may extend to the deep fascia but not into the underlying muscle
What are causes of Necrotising fasciitis
Type I: Polymicrobial due to mixed anaerobic/facultative anaerobic organisms. Bacteroides or peptostreptococcus + E Coli, Enterobacter, Klebsiella, Proteus or non-Group A Strep
Type II: Due to a single organism, most commonly Streptococcus pyogenes, also called group A streptococcus.
What are the signs and symptoms of Necrotising fasciitis
- Anaesthesia or severe pain over site of cellulitis that may be disproportionate to the skin lesion
- Fever
- Palpitations, tachycardia, tachypnoea, hypotension
- N+V
- Redness and oedema
- Haemorrhagic blisters may be present
How is Necrotising fasciitis investigated
Low Na High Urea and creatinine CRP elevated CK elevated Lactate elevated
Diagnostic - Blood and tissue cultures
Surgical exploration
What is Malaria
Infection with protozoan plasmodium
What are the 5 types of plasmodium that can cause Malaria
Plasmodium:
- Falciparum - Most serious
- Vivax
- Ovale
- Malariae
- Knowlesi
How is Malaria transmitted
Bite of the female Anopheles mosquito
The protozoa grow in red blood cells
Which population of people have innate immunity to malaria
Sickle cell trait
G6PD deficiency
Pyruvate kinase deficiency
Thalassemia
What are signs and symptoms of Malaria
Feverish traveller (Incubation up to 1 year) Cyclical symptoms: - High fever - Flu-like symptoms - Severe sweating - Shivering cold/rigors
- Anaemia
- Hepatosplenomegaly
The cycles of symptoms are slightly different in different types of malaria
Cerebral Malaria:
- Headache
- Disorientation
- Coma
How is Malaria diagnosed
Thick and thin blood smears stained with Giemsa stain remain the ‘gold standard’ - Detection of the parasite
Thick - Quantify
Thin - Identify
FBC - Haemolytic picture
Urinalysis - Protein, UBG + CB
