Infectious diseases Flashcards
Amoebic dysentry
- cause
- features
- diagnosis
- treatment
Entamoeba histolytica protozoan Spread by faecal-oral route Features: profuse bloody diarrhoea May be a long incubation period Diagnosis: Stool microscopy may show trophozoites if examined within 15mins or kept warm Treat with metronidazole
Amoebic liver abscess
- what is it
- features
- diagnosis
- treatment
Single mass in the right lobe of liver
Contents of abscess often described as ‘anchovy sauce’
Feature: fever, RUQ pain
Diagnosis: serology is positive in >90% of cases
Treatment: metronidazole followed by a luminal amoebicide. Abscess may require image-guided drainage
Resp antibiotics
- exacerbations of chronic bronchitis
- uncomplicated CAP
- atypical pneumonia
- HAP
- COPD exacerbation: amoxicillin, doxycycline or clarithromycin
- CAP: amoxicilline
- Atypical pneumonia: clarithromycin
-HAP: co-amoxiclav or cefuroxime if within 5 days of admission
Tazocin if more than 5 days after admission
Abx for:
- lower UTI
- pyelonephritis
- lower UTI: trimethoprim or nitrofurantoin (or amoxicillin or cephalosporin)
- Pyelonephritis: broad-spec cephalosporin (cefuroxime, ceftriaxone) or quinolone
Skin abx
- impetigo
- cellulitis
- animal/human bite
- mastitis
- impetigo: topical fusidic acid or oral flucloxacillin
- cellulitis: flucloxacillin (co-amoxiclav if near eyes or nose)
- animal/human bite: co-amoxiclav (doxy+metro if pen allergic)
- mastitis: flucloxacillin
ENT abx
- throat infections
- sinusitis
- otitis media
- otitis externa
- throat: phenoxymethylpenicillin
- sinusitis: amoxicillin (or doxy)
- otitis media: amoxicillin (erythromycin if pen allergic)
- otitis externa: flucloxacillin (or erythromycin if pen allergic)
Genital abx
- gonorrhoea
- chlamydia
- PID
- Syphillis
- Trichomonas vaginalis
- Bacterial vaginosis
- Gonorrhoea: IM ceftriaxone
- Chlamydia: azithromycin or doxycycline
- PID: IM ceftriaxone + metronidazole PO + doxycycline PO
- Syphilis: Benzathine benzylpenicillin IM
- Trichomonas vaginalis: metronidazole PO
- BV: Metronidazole PO
GI abx-
- Clostridium difficile
- Campylobacter enteritis
- Salmonella
- Shigellosis
- Clostridium difficile: first episode metronidazole, if second/multiple episodes then vancomycin
- Campylobacter enteritis: clarithromycin
- Salmonella: ciprofloxacin
- Shigellosis: ciprofloxacin
Abx protein synthesis inhibitors
- examples
- Adverse features of each example
Aminoglyclosides (gentamicin, vancomicin): nephrotoxicity, ototoxicity
Tetracyclines (doxycycline): skin discolouration, photosensitivity
Chloramphenicol: aplastic anaemia
Clindamycin: common cause of C diff
Macrolides (azithromycin, clarithromycin): nausea, P450 inhibitor, prolonged QT
BCG vaccine
- what does it contain
- how is it given
- who is it given to
- contraindications
- Contains live attenuated Mycobacterium bovis
- Given intradermally on lateral aspect of upper left arm. Tuberculin skin test must be done first
- Given to: infants living in high risk UK areas, infants with high risk family members, children who have lived in a high risk country, healthcare workers, prison staff, those working with homeless people
- CI: immunosuppression, previous BCG vaccine, a past hx of TB, pregnancy, positive tuberculin test
Cellulitis
- Causative organism
- Features
- Eron Classification
- IV abx criteria
- Management
Inflamm of skin and subcut tissues, typically due to Strep pyogenes or Staph aureus
Features: commonly occurs on the shins, erythema, pain, swelling, may have systemic illness (fever)
Eron Classification:
- No systemic toxicity, no uncontrolled co-morbidities
- Systemically unwell, or co-morbidities
- Significantly systemically unwell or unstable co-morbidities
- Sepsis or a severe life-threatening infection
IV abx required for: Eron classification 3 or 4 Severe or rapidly deteriorating cellulitis Very young or frail Immunocompromised Significant lymphoedema Facial cellulitis
Management: Flucloxacillin for mild/moderate
Co-amoxiclav or ceftriaxone for severe cellulitis
Cholera
- cause
- features
- management
Cause: Vibro cholerae (gram neg bacteria)
Features: profuse ‘rice water’ diarrhoea, dehydration, hypoglycaemia
Management: oral rehydration therapy, antibiotics (doxycycline or ciprofloxacin)
Bacteria
- gram positive cocci
- gram negative cocci
- gram positive rods/ bacilli
- gram negative rods/ bacilli
- gram pos cocci: Staphylococci, streptococci, enterococci
- gram neg cocci: neisseria, moraxella
- gram pos rod: clostridium, diphtheria, listeria
- gram neg rod: E coli, Haem influenza, Pseudomonas aeruginosa, Salmonella, shigella, campylobacter
Cryptosporidiosis
- what is it
- who is at risk
- features
- diagnosis
- management
- Protozoa
- More common in immunocompromised patients and young children
- Features: watery diarrhoea, abdo cramps, fever
- Diagnosis: modified Ziehl-Neelson stain (acid-fast) of the stool
- Mx: supportive
Dengue fever
- what is it
- features
- treatment
- Viral infection, can progress to viral haemorrhagic fever, 7 day incubation period
- Features: headache (retro-orbital), fever, myalgia, pleuritic pain, facial flushing, maculopapular rash
- treatment: entirely symptomatic (fluids, blood transfusion, etc)
Diphtheria features
Recent travel to eastern europe/russia/asia
Sore throat with a diphtheric membrane (necrotic mucosal cells on tonsils)
Bulky cervical lymphadenopathy
Neuritis
Heart block
Enteric fever (typhoid/ paratyphoid)
- what is it caused by
- transmission
- features
- complications
- Typhoid is caused by Salmonella typhi and paratyphoid is caused by Salmonella paratyphi
- Transmitted via faecal-oral route
- Features: systemic upset (headache, fever, arthralgia), relative bradycardia, abdo pain and distension, constipation, rose spots on the trunk
- complications: osteomyelitis, GI bleed/ perforation, meningitis, cholecystitis
Malignancies associated with Epstein-Barr virus
Burkitts lymphoma, Hodgkins lymphoma, nasopharyngeal carcinoma, HIV-associated CNS lymphomas
E coli
- what type of bacteria is it
- what infections does it often cause
- E coli O157:H7
- Gram neg rod
- UTI, diarrhoeal illnesses, neonatal meningitis
- E coli O157:H7 causes a severe, haemorrhagic watery diarrhoea with a high mortality rate. Can be complicated by HUS
Causes of gastroenteritis
Traveller’s diarrhoea: E coli most common. = At least 3 loose stools in 24hrs with or without abdo cramps, fever, nausea, vomiting, or blood in stool
E Coli: common amongst travellers, watery stools, abdo cramps, nausea
Giardia Lamblia: prolonged, non-bloody diarrhoea
Cholera: profuse watery diarrhoea, severe dehydration, not common amongst travellers
Shigella: bloody diarrhoea, vomiting, abdo pain
Staph aureus: severe vomiting, short incubation
Campylobacter: flu-like prodrome, may mimic appendicitis, may cause guillain-barre syndrome
Features of HIV seroconversion
Typically occurs 3-12 weeks after infection Sore throat Lymphadenopathy Malaise, myalgia, arthralgia Diarrhoea Maculopapular rash Mouth ulcers Rarely meningoencephalitis
Diagnosis of HIV
HIV PCR and p24 antigen tests can confirm diagnosis
HIV antibody test is most common and accurate test (ELISA and Western blot). Most patients develop HIV antibodies at 4-6 weeks.
p24 antigen test: usually positive from about 1 week to 3-4 weeks after infection
Testing HIV in an asymptomatic person should be done at 4 weeks after possible exposure, repeat test at 12 weeks if result is negative
Treating HIV
Highly active anti-retroviral therapy (HAART) involves a combination of at least 3 drugs: two nucleoside reverse transcriptase inhibitors and either a protease inhibitors or a non-nucleoside reverse transcriptase inhibitor
Start HAART as soon as diagnosis is made
Kaposi’s sarcoma
Occurs in HIV patients
Connective tissue cancer caused by Human Herpes Virus 8
Presents as purple papules or plaques on the skin or mucosa
Skin lesions may ulcerate
Resp involvement: massive haemoptysis and pleural effusion
Treat with radiotherapy and resection
Neurocomplications of HIV
Toxoplasmosis Primary CNS lymphoma TB Ecephalitis Cryptococcus Progressive multifocal leukencephalopathy AIDS dementia complex
HIV opportunistic infections and disorders
CD4 200-500: Oral thrush, shingles, hairy leukoplakia, kaposi sarcoma
CD4 100-200: Pneumocystis jiroveci, HIV dementia, Cryptosporidiosis, cerebral toxoplasmosis
CD4 50-100: Aspergillosis, Oesophageal candidiasis, cryptococcal meningitis, primary CNS lymphoma
Pneumocystis jiroveci (PCP)
- what is it
- prophylaxis
- features
- Ix
- Mx
Unicellular eukaryote (fungus) All patients with CD4 count <200 should receive PCP prophylaxis
Features: dyspnoea, dry cough, fever, very few chest signs
Pneumothorax is a common complications
Extrapulmonary features: hepatosplenomegaly, lymphadenopathy, choroid lesions
Ix: CXR (bilateral interstitial pulm infiltrate), exercise-induced desaturation, bronchoalveolar lavage
Mx: Co-trimoxazole, steroids if hypoxic
Gram positive vs gram negative staining
Gram positive will turn purple/blue
Gram negative will be red/pink
Infectious mononucleosis
- what is it
- features
- diagnosis
- management
Glandular fever, caused by Epstein Barr virus
Features:
Classic triad of sore throat, pyrexia, lymphadenopathy
Other features: malaise, anorexia, headache, splenomegaly, hepatitis, lymphocytosis, haemolytic anaemia
Maculopapular pruritic rash develops if amoxicillin is given
Symptoms typically resolve after 2-4 weeks
Diagnosis: monospot test and FBC in the 2nd week of illness to confirm diagnosis
Management: rest, fluid, simple analgesia, avoid contact sport for 8 weeks due to risk of splenic rupture
Lyme disease features
Spread by ticks
Bulls eye rash, fever, arthralgia, heart block, myocarditis, facial nerve palsy, meningitis
Investigations and management of Lymes disease
Ix: clinical diagnosis if bulls eye rash is seen, otherwise ELISA antibodies to Borrelia Burgdorferi are first line test
Mx: doxycycline
Features and complications of malaria
Features: schizonts on a blood film, parasitaemia, hypoglycaemia, acidosis, temp >39, severe anaemia
Plasmodium vivax/ovale causes a cyclical fever every 48 hours, Plasmodium malariae causes a cyclical fever every 72 hours
Complications: cerebral malaria (Seizure, coma), AKI, ARDS, hypoglycaemia, DIC
Management of malaria
Plasmodium falciparum:
Uncomplicated: combination therapy is first line (eg. artesunate plus mefloquine, or aertesunate plus sulfadoxine-prtimethamine)
Severe: IV artesunate
Non-falciparum malaria:
Chloroquine or artesunate-based combination therapy like above
Interpreting mantoux test (Tuberculin Skin Test)
Intradermal injection -> result read 48-72 hours later
Positive result: erythema and induration >10mm. Implies previous exposure including BCG (if strongly positive, ?TB)
False negative Mantoux test: immunosuppression, sarcoidosis, lymphoma, extremes of age, fever, hypoalbuminaemia, anaemia
Necrotising fasciitis
- what is it
- two types
- features
- management
Medical emergency, difficult to recognise in early stages
Type 1: caused by mixed anaerobes and aerobes (often post-op in diabetics), most common type
Type 2: Strep pyogenes
Features: acute onset, painful erythematous lesion, often presents as rapidly worsening cellulitis with pain out of keeping with physical features, extremely tender over infected tissue
Management: urgent surgical debridement, IV abx
Norovirus
- features
- transmission
- limiting transmission
- diagnosis
- management
- Features: symptoms develop within 15-50 hours of infection, N+V, diarrhoea, headache, low grade fever, myalgia
- Transmission: faecal-oral
- Limiting transmission: isolation, good hand hygiene with soap and water
- Diagnosis: clinical history and stool culture viral PCR
- Mx: self-limiting (72hrs), rehydration and electrolyte supplementation
Post-exposure prophylaxis for HIV
Combination of oral antiretrovirals as soon as possible, ideally within 1-2 hours but may be started up to 72 hours following exposure, for 4 weeks
Which vaccinations should be given to hyposplenic patients?
Pneumococcal (every 5 years) Haemophilus type B Meningococcal type C Annual influenza vaccine Penicillin V prophylaxis (at least 2 years but often for life)
Tetanus
- organism
- transmission
- features
- management
- Clostridium tetani
- Tetanus spores are present in soil and may be introduced into the body from a wound
- prodrome fever, lethargy, headache, trismus (lockjaw), risus sardonicus, opisthotonus (arched back, hyperextended neck), spasms (eg. dysphagia)
- Management: supportive (ventilatary support, muscle relaxants), IM human tetanus immunoglobulin for high risk wounds, metronidazole abx
Indications for annual influenza vaccination
65yrs+ Chronic resp disease Chronic heart disease Chronic kidney disease Chronic liver disease Chronic neuro disease DM Immunosuppression Hyposplenism Pregnancy
Health and social care staff
Those in long term residential homes
Carers
Indications for pneumococcal vaccine
65yrs+ Hyposplenism Chronic resp disease Chronic heart disease CKD Chronic liver disease Immunosuppression DM Cochlear implants Cerebrospinal fluid leaks
Yellow fever
- what is it
- features
Viral haemorrhagic fever
Zoonotic infection
Incubation period 2-14 days
Features:
- may cause mild flu-like illness lasting less than one week
- Sudden onset high fever, rigors, N+V, bradycardia. Brief remission followed by jaundice, haematemesis, oliguria
- Councilman bodies (inclusion bodies) may be seen in the hepatocytes
