Infectious Disease Flashcards

Question

Necrotising Fasciitis?

Answer 1

Type 1 = caused by mixed anaesrobes and aerobes (often occurs post-surgery in diabetics) Type 2 = caused by Strep pyogenes **_Features_** * Acute onset * Painful, erythematous lesion develops (cellulitis like) * Extremely tender over infected tissue **_Mx_** * Urgent surgical debridement * IV abx

Answer 2

Gram +ve bacillus Spreads via contaminated food - unpasteurised dairy products Can induce miscarriage **_Features_** * Diarrhoea, flu-like illness * Pneumonia, meningoencephalitis * Ataxia and seizures * CSF may show pleocytosis, with 'tumbling motility' on wet mounts Sensitive to amoxicillin/ampicillin

Answer 3

* Bacillus anthracis, a Gram positive rod * Spread by infected carcasses **_Features_** * Painless black eschar (cutaneous 'malignant pustule', but no pus) * May cause marked oedema * Can cause GI bleeding Treat with ciprofloxacin

Answer 4

Legionella Pneumophilia Colonises water tanks - no person to person transmission **_Features_** * Flu-like symptoms * Dry cough * Lymphopenia * Hyponatremia * Deranged LFTs Diagnosed with urinary antigen Treat with macrolides (erythromycin)

Answer 5

Questions refer to sewage works, farmers, vets or people who work in an abattoir Leptospira interrogans (Spirochaete) Spread classically by contact with infected rat urine **_Features_** * Fever * Flu-like symptoms --\> WITHOUT PRODUCTIVE COUGH * Renal failure (seen in 50% of patients) * Jaundice * Subconjunctival hemorrhage * Headache, may herald the onset of meningitis **_Mx_** * LP to confirm meningeal involvement * High dose ben pen or doxy

Answer 6

Haemophilus influenzae type B

Answer 7

**_Borreliosis_** Caused by 3x species of bacteria belonging to genus Borrelia * Borrelia burgdorefer - main cause in USA * Borrelia afzelii and Borrelia garinii - main cause in Europe **_Features_** * Erythema chronicum migrans (small papule at site of tick bite --\> develops into larger annular lesion with central clearing - bulls eye) * Systemic symptoms - malaise, fever, arthralgia **_Later features_** * CVS - heart block, myocarditis * Neurological - cranial nerve palsies, meningitis * Polyarthritis

Answer 8

* Immune mediated type IV hypersensitivity reaction * Ml of 1:1,000 purified protein derivative (PPD) injected intradermally * Result read 2-3 days later * Erythema & induration \> 10mm = positive result - this implies previous exposure including BCG

Answer 9

Classically involves injection of PPD equivalent to 100,000 units per ml to the skin over the flexor surface of the left forearm. It is then read 3-10 days later * Negative - no induration, 6 minute puncture scars * Grade 1 - 4-6 puncture sites indurated * Grade 2 - Confluent puncture sites form indurated ring * Grade 3 - Extensive induration to form disc (5-10mm) * Grade 4 - Severe induration \>10mm with or without blistering Grades 1-2 = previous BCG or avian tuberculosis Grades 3-4 require CXR and follow up

Answer 10

* Miliary TB * Sarcoidosis * HIV * Lymphoma * Very young age (e.g. \< 6 months)

Answer 11

**_Initial Phase (2 months)_** * Rifampicin * Isoniazide * Pyrazinamide * Ethambutol **_Continuation Phase (4 months)_** * Rifampicin * Isoniazid

Answer 12

**_Latent_** * Isoniazid alone for 6 months **_Meningeal_** * Prolonged period of treatment (12 months) with addition of steroids

Answer 13

**_Rifampicin_** * Liver enzyme inducer * Hepatitis * Orange secretions * Flu like symptoms **_Isoniazid_** * Peripheral neuropathy - prevent with vitamin B6 * Optic neuritis (less common than ethambutol) * Hepatitis, agranulocytosis * Liver enzyme inhibitor **_Pyrazinamide_** * Hyperuricaemia causing gout * Hepatitis **_Ethambutol_** * Optic neuritis (visual acuity check before and during) * Dose adjustment in renal impairment **_Streptomycin (resistant TB)_** * Vestibular damage --\> vertigo and vomiting * Cochlear damage --\> deafness * Anigioedema * Nephrotoxicosis

Answer 14

**_Cause_** * Mycobacterium leprae * Mycobacterium lepromatosis **_Features_** * Nodular skin lesions * Erythematous raised plaque like lesions in arms and legs Can be progressive, causing permanent damange to skin, nerves, limbs and eyes **_Mx_** * Skin biopsy and needle test * \<5 lesions --\> rifampicin and dapsone for 6 months * \>5 lesions --\> rifampicin, clofazimine and dapsone 12 months

Answer 15

**_Severe Malaria_** * Schizonts on a blood film * Parasitemia \> 2% * Hypoglycemia * Temperature \> 39 °c * Severe anemia * Complications as below **_Complications_** * Cerebral malaria: seizures, coma * ARF: blackwater fever, secondary to intravascular hemolysis, mechanism unknown * Acute respiratory distress syndrome (ARDS) * Hypoglycemia * Disseminated intravascular coagulation (DIC)

Answer 16

Strains resistant to chloroquine are prevalent in certain areas of Asia and Africa WHO 2010 guidelines: artemisinin-based combination therapies (ACTs) as first-line therapy ***Examples*** * artemether plus lumefantrine * artesunate plus amodiaquine * artesunate plus mefloquine * artesunate plus sulfadoxine-pyrimethamine * dihydroartemisinin plus piperaquine

Answer 17

* A parasite counts \>2% will usually need parenteral treatment irrespective of clinical state * IV artesunate is now recommended by WHO in preference to intravenous quinine (2010 guidelines) * If parasite count \> 10% then exchange transfusion should be considered * Shock may indicate coexistent bacterial septicemia - malaria rarely causes hemodynamic collapse

Answer 18

1. Plasmodium vivax - **most common**, Central America and Indian subcontinent 2. Plasmodium ovale - Africa 3. Plasmodium malariae Almost always chloroquine sensitive In vivax and ovale - use Primaquine to destory liver hypnozoites

Answer 19

Caused by protozoa Leishmania, spread by sand flies. Multiplies in monocyctes and macrophages Incubation period can extend to 10 years

Answer 20

1. **_Cutaneous Leishmaniasis_** * Caused by Leishmania tropica or Leishmania mexicana * Crusted lesion at site of bite * May be underlying ulcer 2. **_Mucocutaneous Leishmaniasis_** * Caused by Leishmania brasiliensis * Skin lesions may spread to involve mucosae of nose, pharynx 3. **_Visceral Leishmaniasis_** * Mostly caused by Leishmania donovani * Occurs in Mediterranean, Asia, South America, Africa * Fever (typically twice in 24hours), sweats, rigors * Massive splenomegaly, hepatomegaly * Pancytopenia secondary to hypersplenism * Poor appetite\*, weight loss * Grey skin - 'kala-azar' means black sickness or black fever

Answer 21

* Protozoal disease * Two main forms * American Trypanosomiasis (Chagas' disease) * African Trypanosomiasis (Sleeping sickness) * Trypanosoma gambinese - West Africa * Trypanosoma rhodesiense - East Africa * Both spread by the tsetse fly

Answer 22

Acute clinical course * Trypanosoma chancre - tender subcutaneous nodule at site of infection * Enlargement of posterior cervical lymph nodes * Later: central nervous system involvement e.g. Meningoencephalitis **_Management_** * Early disease: IV pentamidine or suramin * Later disease or central nervous system involvement: IV melarsoprol

Answer 23

**_Caused by Trypanosoma cruzi_** * 95% asymptomatic in aucte phase * Chagoma (erythematous nodule at site of infection) and periorbital oedema sometimes seen * Chronic chagas' --\> affects heart and GI tract **_Complications_** * Myocarditis --\> HF and arrhythmias * GI --\> megaoesophagus and megacolon --\> dysphagia and constipation **_Management_** * Treatment is most effective in the acute phase using azole or nitroderivatives such as benznidazole or nifurtimox * Chronic disease management involves treating the complications e.g. heart failure

Answer 24

Parasitic flatworm infection * Schistosoma mansoni and Schistosoma intercalatum: intestinal schistosomiasis * Schistosoma Hematobium: urinary schistosomiasis * Typically presents as a 'swimmer's itch' in patients who have recently returned from Africa. * Frequency, haematuria and bladder calcification * Schistosoma Hematobium is a risk factor for squamous cell bladder cancer * Mx = single dose of oral praziquantel

Answer 25

**_Features_** * Prodrome: headache, fever, agitation * Hydrophobia: water-provoking muscle spasms * Hypersalivation Following animal bite in at risk countries * If an individual is already immunised then 2 further doses of vaccine should be given * If not previously immunised then human rabies immunoglobulin (HRIG) should be given along with a full course of vaccination

Answer 26

Doxy and metronidazole

Answer 27

Caused by gram -ve rod *Bartonella henselae* * fever * history of a cat scratch * regional lymphadenopathy * headache, malaise

Answer 28

* Infectivity = 4 days before rash, until 5 days after the rash first appeared * Incubation period = 11-21 days * School exclusion - 5 days from start of skin eruption * Immunocompromised/newborns with peripartum exposure --\> varicella zoster immunoglobulin (VZIG) * If chickenpox develops then IV aciclovir

Answer 29

Secondary bacterial infection of the lesions * Pneumonia: varicella pneumonia is the most common and serious complication of chickenpox infection in adults. Auscultation of the chest is often unremarkable --\> IV acyclovir * Encephalitis (cerebellar involvement may be seen) * Disseminated hemorrhagic chickenpox * Arthritis, nephritis and pancreatitis may very rarely be seen

Answer 30

Risk of VFS following exposure if 1% if before 20 weeks Very small chance 20-28 weeks, no chance after 28 weeks **_Features_** * Skin scarring, eye defects (microphthalmia), limb hypoplasia, microcephaly and learning disabilities **_Management of Exposure_** * If there is any doubt about the mother previously having chickenpox maternal blood should be checked for varicella antibodies * If the pregnant woman is not immune to varicella she should be given varicella zoster immunoglobulin (VZIG) as soon as possible. RCOG and Greenbook guidelines suggest VZIG is effective up to 10 days post exposure * Consensus guidelines suggest oral aciclovir should be given if pregnant women with chickenpox present within 24 hours of onset of the rash

Answer 31

* RNA paramyxovirus * Spread by droplets * Infective from prodrome until 5 days after rash starts * Incubation period = 10-14 days Complications * Encephalitis: typically occurs 1-2 weeks after the onset of the illness. * Subacute sclerosing panencephalitis: very rare, may present 5-10 years following the illness * Febrile convulsions * Pneumonia, tracheitis * Keratoconjunctivitis, corneal ulceration * Diarrhoea * Increased incidence of appendicitis * Myocarditis

Answer 32

**_Local_** * urethral strictures * epididymitis and salpingitis (hence may lead to infertility) **_Disseminated Gonococcal Infection_** * Haematogenous spread from mucosal infection * Triad = tenosynovitis, migratory polyarthritis and dermatitis. * Later complications = septic arthritis, endocarditis and perihepatitis (Fitz-Hugh-Curtis syndrome)

Answer 33

HPV 6 and 11 (16, 18 and 33 predispose to cervical cancer) **_Management_** * Podophyllum or cryotherapy * Multiple, non-keratinised warts are generally best treated with topical agents whereas solitary, keratinised warts respond better to cryotherapy * Imiquimod = topical cream, 2nd line * Often resistant to treatment, recurrence common - most infections clear within 1-2 years

Answer 34

HSV 2 (cold sores are HSV 1) * Primary attacks often severe, associated with fever; subsequent attacks generally less severe and localised to one site * Features --\> severe gingivostomatitis, cold sores, painful genital ulceration * Management * Gingivostomatitis: oral aciclovir, chlorhexidine mouthwash * Cold sores: topical aciclovir although the evidence base for this is modest Genital herpes: oral aciclovir. Some patients with frequent exacerbations may benefit from longer term aciclovir

Answer 35

Spirochaete - Treponema pallidum **_Primary_** * Chancre - painless ulcer at site of sexual contact * Often not seen in women **_Secondary_** (4-10 weeks after initial infection) * Systemic symptoms: fevers, lymphadenopathy * Rash on trunk, palms and soles * Buccal 'snail track' ulcers (30%) * Condylomata lata **Latent period** **_Tertiary_** * Gummas * Aortic aneurysms * General paralysis of the insane * Tabes dorsalis (slow degeneration of the sensory neurons. The degenerating nerves are in the dorsal column; proprioception, vibration, and fine touch).

Answer 36

Serological tests divided into 1. **_Cardiolipin tests_** * Syphilis infection leads to the production of non-specific antibodies that react to cardiolipin * Examples include VDRL (venereal disease research laboratory) & RPR (rapid plasma reagin) * Insensitive in late syphilis * Becomes negative after treatment * Causes of false positives = pregnancy, SLE, antiphospholipid, TB, leprosy, malaria, HIV 2. **_Treponemal specific antibody tests_** * Example: TPHA (Treponema pallidum hemagglutination test) * Remains positive after treatment

Answer 37

Chlamydia trachomatis Three stages 1. Small painless pustule which later forms an ulcer 2. Painful inguinal lymphadenopathy 3. Proctocolitis

Answer 38

Overgrowth of anaerobes such as Gardnerella vaginalis Fall in lactic acid producing aerobic lacobacilli resulting in raised vaginal pH 3 of the 4 following for diagnosis * Thin, white homogenous discharge * Clue cells on microscopy * Vaginal pH \> 4.5 * Positive whiff test (addition of potassium hydroxide results in fishy odour) Managmenet = 5-7 days oral metronidazole Pregnancy - increased risk of preterm labour, LBW, late miscarriage - oral metronidazole can be used throughout pregnancy

Answer 39

* Epididymitis * Pelvic inflammatory disease * Endometritis * Increased incidence of ectopic pregnancies * Infertility * Reactive arthritis * Perihepatitis (Fitz-Hugh-Curtis syndrome)

Answer 40

* Parrot disease, parrot fever * Characterized by malaise, fever, myalgias and pneumonia * Exposure to an ill bird and a rash (Horder’s spots) are pathognomonic. * Erythromycin or tetracyclines are the drugs of choice.

Answer 41

Most common = CMV

Answer 42

* Protozoa which infects the body via the GI tract, lung or broken skin * Its oocysts release trophozoites which migrate widely around the body including to the eye, brain and muscle. * The usual animal reservoir is the cat, although other animals such as rats carry the disease. * Most infections asymptomatic - if symptomatic normally self-limiting infection, features resembling infectious mono --\> less commonly meningoencephalitis and myocarditis

Answer 43

Vibro cholerae (gram -ve) **_Features_** * Profuse 'rice water' diarrhoea * Dehydration * Hypoglycemia **_Management_** * Oral rehydration therapy * Antibiotics: doxycycline, ciprofloxacin

Answer 44

Causes by flagellate protozoan Giardia lamblia Faecal oral route **_Features_** * Often asymptomatic * Lethargy, bloating, abdominal pain * Non-bloody diarrhoea * Chronic/prolonged diarrhoea, malabsorption and lactose intolerance can occur * Stool microscopy for trophozoite and cysts are classically negative, therefore duodenal fluid aspirates or 'string tests' (fluid absorbed onto swallowed string) are sometimes needed

Answer 45

Aerobic gram -ve rods (not normally present in gut) **_Features_** * Initially systemic upset as above * Relative bradycardia * Abdominal pain, distension * Constipation: although Salmonella is a recognised cause of diarrhoea, constipation is more common in typhoid * Rose spots: present on the trunk in 40% of patients, and are more common in paratyphoid **_Possible Complications_** * Osteomyelitis (especially in sickle cell disease where Salmonella is one of the most common pathogens) * GI bleed/perforation * Meningitis * Cholecystitis * Chronic carriage (1%, more likely if adult females)

Answer 46

* Causes bloody diarrhoea, abdo pain * Severity depends on type: S sonnei (e.g. from UK) may be mild, S flexneri or S dysenteriae from abroad may cause severe disease * Treat with ciprofloxacin

Answer 47

Caused by Rickettsiae * Black sopits on thigh * Hx of tick bites * Low grade fever * Faint macular rash

Answer 48

Spread by ticks, common in the USA * Fever * Rash on hands, feet which later --\> desequamte (peel) * Tachycardia with no hypotension (unlike Staphylococcal Toxic Shock Syndrome) Treat with doxycycline

Answer 49

Caused by the Rickettsia conorii and transmitted by the dog tick Rhipicephalus sanguineus * Incubation period: 7 days. * Abrupt onset - chills, high fevers, myalgia and joints pain, severe headache, photophobia and diarrhea. * The location of the bite forms a black spots or ulcerous crust (tache noire). * Around the fourth day of the illness exanthem appears, first macular and then maculopapular and sometimes petechial Treat with Doxycycline

Answer 50

Type of viral haemorrhagic fever (yellow fever, Lassa fever, Ebola) **_Low platelet count and raised transaminase level is typical_** * Transmitted by the Aedes aegyti mosquito * Incubation period of 7 days * Africa, Central and South America, the Caribbean, the Eastern Mediterranean, South and Southeast Asia, and Oceania. * Form of DIC called dengue haemorrhagic fever (DHF) may develop --\> Dengue shock syndrome (DSS) **_Features_** * Causes headache (often retro-orbital) * Myalgia * Pleuritic pain * Facial flushing (dengue) * Maculopapular rash * Pyrexia Treatment is symptomatic - fluid resus, transfusions etc.

Answer 51

Caused by EBV * Sore throat * Lymphadenopathy * Pyrexia * Malaise, anorexia, headache * Palatal petechiae * Splenomegaly - occurs in around 50% of patients and may rarely predispose to splenic rupture * Hepatitis * Presence of 50% lymphocytes with at least 10% atypical lymphocytes * Hemolytic anaemia Management - rest, fluids, simple anaglesia. No contact sport for 8 weeks.

Answer 52

* Burkitt's lymphoma * Hodgkin's lymphoma * Nasopharyngeal carcinoma * HIV-associated central nervous system lymphomas Hairy leukoplakia also associated with it (non-malignant)

Answer 53

* RNA virus * Spread by the faecal-oral route, incubation period = 3-8 weeks * Common in Central and South-East Asia, North and West Africa, and in Mexico * Causes a similar disease to hepatitis A, **but carries a significant mortality (about 20%) during pregnancy** * Does not cause chronic disease

Answer 54

Erythema infectiosum (also known as fifth disease or 'slapped-cheek syndrome') * Systemic symptoms: lethargy, fever, headache * 'slapped-cheek' rash spreading to proximal arms and extensor surfaces **_Other presentations_** * Asymptomatic * Pancytopenia in immunosuppressed patients * Aplastic crises e.g. in sickle-cell disease (parvovirus B19 suppresses erythropoiesis for about a week so aplastic anemia is rare unless there is a chronic hemolytic anemia)

Answer 55

* Condition found in sheep and goats although it can be transmitted to humans. * Caused by the parapox virus. **_In humans_** * Generally affects the hands and arms * Initially small, raised, red-blue papules * Later may increase in size to 2-3 cm and become flat-topped and hemorrhagic **_In animals_** * Scabby leisons around mouth and nose

Answer 56

1. **_Ancylostoma braziliense_** * Most common cause of cutaneous larva migrans * Common in Central and Southern America 2. **_Strongyloides stercoralis_** * Acquired percutaneously (e.g. Walking barefoot) * Causes pruritus and larva currens - this has a similar appearance to cutaneous larva migrans but moves through the skin at a far greater rate * Abdo pain, diarrhoea, pneumonitis * May cause gram negative septicemia due to carrying of bacteria into bloodstream * Eosinophilia sometimes seen * **Management**: thiabendazole, albendazole. Ivermectin also used, particularly in chronic infections 3. **_Toxocara canis_** * Commonly acquired by ingesting eggs from soil contaminated by dog faeces * Commonest cause of visceral larva migrans * Other features: eye granulomas, liver/lung involvement

Answer 57

**_Cysticercosis_** * Caused by Taenia solium (from pork) and Taenia saginata (from beef) * Management: niclosamide **_Hyatid disease_** * Caused by the dog tapeworm Echinococcus granulosus * Life-cycle involves dogs ingesting hydatid cysts from sheep liver * Often seen in farmers * May cause liver cysts * Management: albendazole

Infectious Disease Flashcards

(82 cards)