Infectious Diseases Flashcards
Describe malaria, it’s features, investigations, and treatment.
Malaria can be grouped into non-falciparum and falciparum as the the later is a species which causes a more severe disease.
Features: 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 first line, if not tolerated oral dapsone. If this is not tolerated or inappropriate e.g. patients with g6pd then thirdly line prophylaxis is nebulised pentamidine
- A role for methylprednisolone in severe cases i.e. pO2 less than 9.3
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) E.coli + Group B strep (newborns)
Describe necrotising fasciitis and its management
It is a rapidly progressive infection of the deep fascia causing necrosis of subcutaneous tissue. In any atypical cellulitis get early surgical help. There is intense pain. Group A B-haemolytic streptococci is a major cause although infection is often polymicrobial
Management: urgent surgical debridment and IV antibiotics e.g benzylpenicillin and clindamycin
What is fourniers gangrene?
Necrotising fasciitis localised to the scrotum and perineum
Describe infective endocarditis, it’s risk factors, symptoms, tests, and management.
Fever + new murmur is endocarditis until proven otherwise. Follows an acute course and presents with acute heart failure and emboli. Usually due to Staph A or Strep Viridians, more rarely HÁČEK organisms (Haemophilus, Aggregatibacter, Cardibacetirum Hominis, Eikenella Corrodens, Kingella).
Risk Factors: IVDUs, aortic or mitral valve disease, prosthetic valves, VSD, patent ductus arteriosus, coarctation
Symptoms and signs:
- Septic signs: fever, rigors, night sweats, malaise, weight loss, anaemia, splenomegaly and clubbing.
- New murmur (usually regurgitive)
- immune complex deposition may give vasculitic symptoms, microscopic haematuria is common, Roth spots, splinter haemorrhages, janeway lesions, osler nodes
- embolic phenomena e.g abscesses in other organs, in the skin they are termed janeway lesions and together with Osler nodes are pathognomic for IE
Tests:
- blood cultures, bloods (FBC may show normochromic normocytic anaemia, neutrophilia, high ESR/CRP, check U+E, LFT for end-organ damage)
- Urinalysis may show microscopic haematuria
- CXR may show cardiomegaly
- ECG may show long PR interval due to aortic root abcess
- diagnosis made with dukes criteria and requires TOE which may show vegetations
Management:
- vancomycin +/- gentamicin if septic pre-culture
- Benzylpenicillin +/- gentamicin if strepOr flucloxacillin if staph
- echo +/- surgery if valve incompetence
What are Roth spots?
Boat shaped retinal haemorrhage with pale centres caused by microinfarcts e.g from IE, hypertension, HIV, connective tissue disease, anaemia, Behcet’s, viraemia, hypercoagulability
Describe Herpes Simplex virus
HSV is the cause of the common cold sore and genital herpes though it may cause other primary infections.
Dormant HSV in ganglion cells may be reactivated by illness, immunosuppression, menstruation, or sunlight.
Describe chickenpox
Caused by Varicella Zoster virus, it is an contagious febrile illness with crops of blisters at various stages. Usually self-limiting in children complications such as purpura fulminans/DIC, pneumonitis, and ataxia are commoner in pregnancy and adults than in children.
Incubation is 11-21days and patients are infective 4days before the rash until all lesions are scanned over.
After infection, virus is dormant in dorsal root ganglia. Reactivation causes shingles
Describe shingles
Shingles is caused by reactivation of VZV, causing pain in dermatomal distribution followed by fever, malaise and rash.
Treat with aciclovir, be aware of post-herpetic pain in affected dermatomes which can last years, try amitriptyline
What are coryzal symptoms?
Cold-like symptoms such as sneezing, coughing, sore throat, watery eyes, nasal congestion, runny nose
Describe Cellulitis, it’s presentation, and management.
Acute infection of skin and soft tissues (commonly legs). Usually due to beta-haemolytic strep, or staph A.
Presentation: Pain, swelling, warm erythematous skin, systemic upset, local lymphadenopathy.
Management:
- elevate the legs
- flucloxacillin 500mg/6h PO
- Benzylpenicillin 600mg/6h IV if systemically upset.
- Erythromycin 500mg/12h PO if pen-allergic
Describe Urinary Tract Infections (UTIs), its risk factors, symptoms, investigations, and management.
May be upper (renal pelvis) or lower (urethra bladder, prostate), complicated (abnormal renal tract/GU tract, voiding difficulty/obstruction, decreased renal function) or uncomplicated (normal renal tract + function. E. coli is the main organism, others include proteus, klebsiella.
Risk factors: Female sex, sexual intercourse, exposure to spermicide in women, pregnancy, menopause, immuno-suppressed/compromised, urinary tract obstruction, stones, catheter.
Symptoms: Burning sensation when urinating, foul-smelling urine, fever rigors, vomting, loin pain, supra public pain, urgency, frequency.
Investigations:
- urinalysis +ve leucocytes and nitrites.
- MSU for MC+S
Management:
- prevention, drink more water, cranberry juice,
- empirical treatment e.g. Trimethoprim, or nitrofuratoin adjust on culture and local sensitivities.
Describe Osteomyelitis, its symptoms, tests and management.
Infection of the bone most commonly caused by Staph A, except in patients with sickle-cell where salmonella predominates. At risk groups include, diabetics, sickle-cell, IVDUs, immunosuppression, alcohol abuse.
Symptoms: gradual onset of pai with tenderness, warmth, erythema, unwillingness to move, effusion in neighbouring joints, signs of systemic infection.
Tests: MRI, blood cultures, ESR/CRP raised, WCC raised.
Management:
-flucloxacillin for 6 weeks (clindamycin if pen-allergic)
Describe Leptospirosis (Weils Disease), its symptoms, and management.
Commonly seen in questions referring to sewage workers, farmers, vets or people who work in an abattoir. It is caused by the spirochaete Leptospira interrogates which is classically spread by contact with infected rat urine.
Symptoms: Fever, flu-like symptoms, renal failure, jaundice, subconjunctival haemorrhage, headache (beware meningitis
Management:
- high dose benzylpenicillin or doxycycline.
- IV penicillin G if severe.
Describe Kaposi’s sarcoma and it’s types
A spindle cell tumour derived from capillary endothelial cells or from fibrous tissue caused by Herpes hominis virus (HHV-8).
Presents as Purple macules, papules, nodules and plaques affecting the skin associated with HIV infections an AIDS defining illness can also affect the mucosa of any organ.
Types:
- Type 1 classic especially in elderly Jewish or Mediterranean males
- type 2 endemic, in forms 1 and 2 peripheral slow growing lesions are found and visceral involvement is rare, but node involvement may cause oedema
- Type 3 KS in immunisupression e.g. Organ transplants
- Type 4 AIDs related organ involvement is more common and disease is widespread optimise HAART
Describe Tinea, its symptoms, and management
A ringworm (fungal) infection. Named depending on the area affected e.g. Tinea pedis (foot), Tinea cruris (groin), Tinea capitis (scalp), Tinea unguim (nail), Tinea corporis (body).
Symptoms: a round, scaly, itchy lesion whose edge is more inflamed than its centre.
Management:
- skin scrappings from edge (active region), nail clippings, hair pulls, for microscopy and culture.
- 1% terbinafine cream.
Describe onychomycosis (Fungal Nail Infection), it’s causes, symptoms, and management.
Causes: mostly dermatophytes, mainly trichophyton rubrum (90%). Also yeasts such as candida. And non-dermatophytes moulds.
Symptoms: unsightly nails are a common reason for presentation, they appear thickened, rough, opaque.
Management:
- nail clippings and scrapings of affected nail
- confirm microbiology before treatment
- if dermatophyte infection oral terbinafine is currently first line with oral itraconazole as an alternative. Treatment need for 6-12wks for fingernails and 3-6mths for toenails
- candida infection should be treated topical if mild e.g. Amorolfine or oral intraconazole for 12wks if more severe.
What treatment should be given to those found to be carriers of MRSA.
Nose swab +ve = mupirocin 2% in white soft paraffin TDS 5days
Skin swab +ve = chlorhexidine gluconate OD 5days
Vancomycin, telco planing and linezolid are used in treatment of MRSA.
Describe Schistosomiasis, it’s presentation, investigations, management, and complications.
Also known as swimmers itch, caused by a worm.
Presentation: Can present Acutely, or with chronic infection.
- Acute syndrome (Katayama syndrome) is due to sudden release of antigenic eggs. Symptoms include swimmers itch (urticaria like rash after parasite has penetrated skin), malaise, arthralgia, myalgia, cough, Diarrhoea, and RUQ pain, fever, hepatomegaly.
- Chronic disease may present months to years after exposure, symptoms include bloody diarrohoea, abdominal pain, RUQ pain, haematemesis, haematuria, frequency, dyspnoea on exertion, cough, chest pain.
Investigations: Microscopic examination of stool or urine for eggs. Serology can detect less advanced infections.
Management: Praziquantel is treatment of choice.
Complications: Secondary infection, renal stones, bladder carcinoma, hydronephrosis, CKD, portal hypertension, pulmonary hypertension
Describe Rheumatic Fever, it’s diagnostic criteria, and management.
Systemic infection caused by sensitivity reaction to Group A beta-haemolytic streps which can lead to permanent damage to heart valves.
Diagnostic Criteria: Requires evidence of Group A strep infection + 2 major or 1 major and 2 minor criterion.
- Evidence of Group A Strep infection e.g. Positive throat culture, recent scarlet fever, +ve rapid streptococcal antigen test, elevated ASO
- Major Criterion: Carditis, Polyarthritis, Subcutaneous nodules, Erythema Marginatum, Sydenham’s Chorea
- Minor Criterion: Fever, Raised ESR/CRP, Arthralgia, Prolonged PR interval, Previous Rheumatic fever.
Management:
- Bed rest until CRP normal for 2wks, helps joints and heart
- Benzylpenicillin IV stat plus Penicillin for 10days
- High dose aspirin for carditis
- Haloperidol or diazepam for chorea
- Secondary Prophylaxis
Describe Rubella, it’s symptoms, and complications.
An RNA virus, live vaccine available. Screened for antenatally due to risk of malformation. infective 5days before and 5days after rash.
Symptoms: may be asymptomatic, or macular rash, suboccipital lymphadenopathy.
Complications: in utero malformations. Most at risk in first 16wks gestation. Cataracts with in infection at 8-9wks, deafness with infection at 5-7wks, cardiac lesions at 5-10wks.
Describe Cytomegalovirus, its presentation, and management.
Thought that 50% have been exposed but usually only causes disease in the immunocompromised e.g. HIV. Infected cells have an ‘Owl’s eye’ appearance due to intranuclear inclusion bodies.
Presentation: similar to glandular fever (sore throat, fever, splenomegaly) or hepatitis (fever, jaundice), also retinitis and colitis.
Management:
-Ganciclovir IV 5mg/kg/12h
Describe Toxoplasmosis, it’s presentation, and management.
Protozoan Toxoplasma Gondii found in poorly cooked meat, soil-contaminated vegetables. High risk in Pregnancy and HIV.
Presentation:
- Similar to Infectious mononucleosis e.g. Sore throat, lymphadenopathy, petechial palate, fever. CNS signs if immuno-comprised
- Cerebral: accounts for 50% of cerebral lesions in patients with HIV, headache, confusion, drowsiness, CT shows ring enhancing lesions.
- Congenital: Abortion, seizures, choroidoretinitis, hydrocephalus, microcephaly, cerebral calcification.
Management:
-sulfadiazine and pyrimethamine
Describe Cryptococcal Meningitis, its symptoms, investigations, and management.
HIV associated disease, most common fungal infection of CNS.
Symptoms: Headache, fever, malaise, nausea/vomiting, seizures, focal neurological signs.
Investigations: CSF high opening pressure, India ink test +ve, CT shows meningeal enhancement and cerebral oedema.
Management:
- amphotercin B IV + 5-Flucytosine
- secondary prophylaxis of fluconazole until CD4 over 150 and cryptococcal antigen -ve.
