Microbiology Flashcards

Question

Causes of neutropenic picture/pyrexia of unknown origin

Answer 1

Chemotherapy Haematological malignancies Drugs like clozapine, carbimazole

Answer 2

Caused by salmonella typhi and paratyphi (gram -ve bacilli) Transmitted in food and water, with incubation 1-2weeks Causes enteric fever --> infects Peyers Patches in intestine Symptoms include: *Fever *Constipation *Rose spots *Headaches *Relative bradycardia *Hepatosplenomegaly Treat with IV ceftriaxone, then PO azithromycin

Answer 3

Caused by flavivirus, spread by Aedes mosquito Short incubation period (days) Symptoms include: *Myalgia *Fever *Rash Reasonably mild and self-limiting however... can cause dengue hemorrhagic fever or dengue shock syndrome if re-infected with a different serotype

Answer 4

Protozoal infection (plasmodium) spread by female anopheles mosquitos Life cycle involves mosquitos and humans (RBCs and liver) **Classified by species - Falciparum vs. non-falciparum** P. falciparum - most common and most severe (admit to hospital) Non-falciparum (less severe with outpatient management) - P. vivax, P. ovale, P. malariae, P. knowlesi

Answer 5

Schüffner's dots on blood film Either an oral artemisinin combination therapy (ACT), or chloroquine

Answer 6

thick and thin blood films - thick detects malaria whilst thin detects species Mild treatment - artemisinin combination therapy (ACT) which uses Artemetherelumefantrine. If unavailable, quinine or atovaquone eproguanil can be used Severe treatment - IV artesunate. If unavailable, use IV quinine

Answer 7

Gram -ve aerobic bacilli (facultative intracellular) Transmission - contaminated food (untreated milk/dairy) and direct animal contact Presentation - undulant fever (peaks in evening), myalgia, arthritis, spinal tenderness, hepatosplenomegaly, epididymo-orchitis Serology - anti-O-polysaccharide antibody, WCC normal/neutropenia Treatment - doxycycline + streptomycin (expensive) or Rifampicin (cheap) for 4-6 weeks Complications - endocarditis, osteomyelitis, meningoencephalitis

Answer 8

Rhabdovirus Transmission commonly through dogs and bats Presents in 3 phases: 1) Prodrome - fever, headache, sore throat 2) Acute encephalitis (hyperactive state) 3) Migration to CNS (after months-years) --> fatal encephalitis, hyper salivation, hydrophobia Serology - IgM Negri bodies Treatment - rabies IgG post-exposure treatment (before symptoms) + full rabies vaccination course

Answer 9

Yersinia pestos, gram -ve lactose fermenter Transmission by fleas with reservoir in rats Presents with: 1) Bubonic plague (most common) - flea bites human, swollen tender lymph nodes (buboes), dry gangrene 2) Septicaemic plague - flea bite or direct contact on to broken skin, DIC causing haemorrhage, necrosis with purpura and gangrene, no lymph node involvement 3) Pneumonic plague (least common) - epidemic with person-person spread PCR test to confirm Treatment - Streptomycin, doxycycline, gentamicin, chloramphenicol (in meningitis)

Answer 10

Leptospira interrogans, Gram -ve Transmission - excreted in dog/rat urine, with penetration of broken skin or swimming in contaminated water Presentation - high fever, conjunctival haemorrhages, jaundice, meningism, renal failure, haemolytic anaemia Treatment: Not critically ill - doxycycline or azithromycin (within 48hrs) Mild to moderate - amoxicillin or ampicillin Severe (requiring hospitalisation) - IV penicillin G

Answer 11

Bacillus anthracis, gram +ve spore forming Routes of infection - cutaneous (95%), inhalation (pulmonary), intestinal, injection Presentation of cutaneous - ulceration of black vesicular lesion with surrounding oedema. Usually affects hands, face, forearm and neck Presentation of inhalation - massive lymphadenopathy with flu-like symptoms + mediastinal haemorrhage Treatment - doxycycline or ciprofloxacin, combined with another antibiotic of choice

Answer 12

Borrelia burgdorferi (spirochaete), which is anthropode-borne Transmission - lxodes ticks which are infected by B. burgdorferi Presentation: 1) Early - erythema chronic migrans (bullseye rash), flu-like 2) focal neurology, neuropsychiatric, arthritis Investigations - biopsy edge of rash + perform ELISA for Lyme Abs Treatment - Doxycycline 2-3 weeks (or amoxicillin or cefuroxime). If present with neurological symptoms, consider IV Abx

Answer 13

Coxiella burnetii, gram -ve parasite Transmission through farm animals (cattle and sheep) Presentation - atypical pneumonia (dry cough, fever), no rash, hepatitis, erythema nodosum Serology - rise in phase II IgG through IFA Treatment - doxycycline

Answer 14

Infection of trypanosomatid protozoan: Leishmania Transmission by female phlebotomine sandflies Presentation: 1) Cutaneous (most common) - erythematous patches at bite --> painless ulceration --> multiply in dermal macrophages --> heals after 1yr leaving depigmented scar 2) Diffuse - patients with immunodeficiency, nodular lesions that spread around body 3) Mucocutaneous - New World sandfly species, dermal ulcers like cutaneous presentation. Months to years later, patient presents with ulcers in mucous membranes of nose, mouth and throat 4) Visceral (aka Kala Azar) - usually young malnourished child. Abdominal discomfort and distension (marked hepatomegaly and enormous splenomegaly) with fever, weight loss and anorexia. Can also present with anaemia, pancytopenia and hypergammaglobulinaemia. Specifically in Leishmania Donovan - invasion of reticuloepithelial system --> hepatosplenomegaly + bone marrow invasion --> disfiguring dermal disease (aka PKDL) Treatments (many) - includes antimony compounds, miltefosine, amphotericin, paromomycin, fluconazole, pentamidine and more...

Answer 15

Superficial - diagnosed with wood lamp: 1) Tinea 2) Pityriasis Deep seated - diagnosed clinically, lab results and imaging: 1) Candida 2) Aspergillus (ABPA, invasive aspergillosis, aspergilloma) 3) Cryptococcus (particularly in HIV)

Answer 16

Polyene (e.g. amphotericin) - cell membrane integrity - yeast Azole (e.g. fluconazole) - cell membrane synthesis - yeast Terbinafine - cell membrane - mould (vs dermatophytes) Flucytosine - DNA synthesis Echinocandin (e.g. caspofungin) - cell wall - yeast (less toxic SE)

Answer 17

Protein-only infectious agent which causes rare transmissible spongiform encephalopathies in humans and animals --> rapid neuodegeneration and death in months Most common is CJD (Creutzfeldt-Jakob Disease) Pathophysiology: due to abnormal folding of protein PrP to cause beta-sheet configuration + protease/radiation resistance. This eventually causes it to become insoluble Inherited prion disease is caused by PNRP gene mutation and codon 129 polymorphism - 3 types MM, VV or MV

Answer 18

see lecture on prions. very difficult help