Infectious Diseases Flashcards
Describe malaria, it’s signs and symptoms, diagnostic tests and treatment.
Malaria can be grouped into non-falciparum and falciparum as the the later is a species which causes a more severe disease.
Signs & Symptoms: •commonly a relapsing fever •chills •rigors •anaemia •hepatosplenomegaly •jaundice •headache •myalgia
Tests:
•serial thin and thick blood films
•FBC, U+E, LFTs, Glucose G6PD activity for prognostic factors
Treatment:
•uncomplicated non-falciparum malaria - chloroquine (quinine if resistant) and primaquine for liver stage (not needed in p.malariae also screen for G6PD defiency as can induce haemolysis)
• uncomplicated falciparum malaria - combination therapy preferably using artemisinin derivatives oral if able
•severe falciparum malaria - IV antimalarials as above and ITU involvement
Describe the malaria life cycle
Humans acquire malaria after being bitten by an infected female Anopheles mosquito. The sporozoites in the saliva of the mosquito enter the host and travel via the bloodstream to the liver where they mature (or in some species remain dormant where they are known as hypnozoites e.g Ovale & Vivax. The mature sporozoites then erupt releasing merozoites in to the bloodstream when they invade RBCs and undergo asexual reproduction. Mosquitoes ingest these and the organism undergoes sexual reproduction to produce thousands of sporozoites which then migrate to the salivary gland repeating the cycle.
What is the CURB-65 score?
CURB-65 is a score used to assess severity of pneumonia score 1 point for each:
C onfusion (abbreviated mental test 8 or less)
U rea greater than 7mmol/L
R espiratory Rate 30/min or more
B lood pressure less than 90mmHg systolic and/or 60mmHg diastolic
65 or greater age.
Score:
0-1 home management possible
2 indicates hospital therapy
3 or more indicates severe pneumonia with mortality 15-40% consider ITU.
Describe pneumonia, its common causes, clinical features, diagnostic tests and management.
An acute lower respiratory tract illness associated with consolidation on chest x-ray.
Community acquired pneumonia (CAP) most commonly caused by Streptococcus Pneumoniae followed by Haemophilus Influenzae, and Mycoplasma Pneumoniae. Hospital acquired pneumonias tend to be gram-negative enterobacteria or Staphylococcus Aureus.
Clinical features: Fevers, rigors, malaise, anorexia, dyspnoea, cough, purulent sputum, haemoptysis, and pleuritic pain. Signs: pyrexia, cyanosis, confusion, tachycardia, hypotension.
Tests: CXR, O2sats, Bloods (FBC, U+E, LFT, CRP, blood cultures), sputum culture.
Management: Antibiotics, orally if not severe or vomiting. severe needs IV. Oxygen to maintain sats at 94-98% and IV fluids as necessary. VTE prophylaxis. Consider ITU if shock, hypercapnia, or uncorrected hypoxia.
Describe Pneumococcal Pneumonia and its treatment
It is the commonest bacterial pneumonia. It affects all ages, but is commoner in the elderly, alcoholics, post-splenectomy, immuno-suppressed, and patients with chronic heart failure or pre-existing lung disease.
Treatment: Amoxicillin, Benzylpenicillin or Cephalosporin
Describe Staphylococcal Pneumonia, it’s features, and treatment
It may complicate influenza infection or occur in the young, elderly, IVDUs, or patients with underlying disease e.g. leukaemia, lymphoma, cystic fibrosis.
Features: it causes a bilateral cavitating bronchopneumonia.
Treatment: flucloaxacillin +/- rifampicin, MRSA (vancomycin).
Describe Klebsiella Pneumonia, it’s features, and treatment.
It is rare, it occurs in elderly, diabetics and alcoholics.
Features: Causes a cavitating pneumonia, particular of the upper lobes, often drug resistant.
Treatment: cefotaxime or imipenem
Describe Pseudomonas Pneumonia
Pseudomonas is a common pathogen in bronchiectasis and Cystic Fibrosis. It is a cause of hospital-acquired infections, particularly on ITU or after surgery.
Describe Mycoplasma pneumonia, it’s features, and treatment
It occurs in epidemics about every 4yrs. It is an atypical pneumonia.
Features: It presents insidiously with flu-like symptoms (headache, myalgia, arthalgia) followed by a dry cough. CXR shows reticular-nodular shadowing or patchy consolidation often of 1 lower lobe.
Treatment: clarithromycin or doxycycline.
Describe legionnaire’s disease, it’s symptoms, investigations, and management
Legionella pneumophilia colonizes water tanks kept at less than 60degreesC (e.g. Hotel air-conditions and hot water systems) causing out breaks of Legionnaire’s disease.
Symptoms: Flu-like symptoms (fever, malaise, myalgia) precede a dry cough and dyspnoea. Extra-pulmonary features include anorexia, D+V, hepatitis, renal failure, confusion and coma.
Investigations:
- CXR shows bi-basal consolidation
- Bloods shows lymphopenia, hyponatraemia, and deranged LFTs.
- Urinalysis may show haematuria
- Diagnosis made by legionella urine antigen/culture
Treatment:
-fluoroquinolone for 2-3wks or clarithromycin
Describe chlamydophila pneumonia, it’s features, and treatment
It is the commonest chlamydial infection, Person to person spread occurs.
Features:a biphasic illness: pharyngitis, hoarseness, otitis, followed by pneumonia.
Treatment: doxycycline or clarithromycin
Describe psittacosis, it’s features, and treatment
Chlamydiophila psittaci causes this ornithosis acquired from infected bird typically parrots.
Features: headache, fever, dry cough, lethargy, arthalgia, anorexia and D+V. CXR shows patchy consolidation.
Treatment: doxycycline or clarithromycin
Describe pneumocystis pneumonia, it’s features, and treatment.
This pneumocystis jiroveci causes this pneumonia in the immunosuppressed e.g. HIV.
Features: It presents with dry cough, exertional dyspnoea, decreased PaO2, bilateral crepitations. CXR may be normal or show bilateral perihilar shadowing. Diagnosed through visualisation of organism in culture.
Treatment: high dose co-trimoxazole
Describe Tuberculosis, its risk factors, symptoms, tests and management
TB is a notifiable disease, at risk populations often screened via Mantoux test or Interferon gamma testing (t-spot-TB)
Risk factors: poverty, alcohol, tobacco, contact with TB, immunosuppression ( HIV, DM, malignancy, extremes of age) and renal disease
Symptoms: cough, sputum, malaise, weight loss, night sweats, pleurisy, haemoptysis. May disseminate and appear in other systems causing symptoms
Tests: CXR and sputum samples, if disseminated try to get a sample, send for MC&S for Acid Fast Baccili on Ziegler-neelsen stain. Culture can take up to 12 weeks on Lowenstein-Jensen medium, PCR allows for rapid identification if rifampicin (and so likely multi-drug) resistance
Management: before treatment test colour vision (with ishihara charts) and acuity as ethambutol may cause ocular toxicity. 16 weeks on iosoniazid and rifampicin and 8 weeks on ethambutol and pyrazinamide. Monitor LFTs and FBC
What are some causative agents in bacterial meningitis?
Meningococcal (Nisseria meningitidis)
Pneumococcal (Strep Pneumoniae) (elderly)
Haemphilus influenzae ( very young)
Listeria monocytogenes (extremes of age)
