Microbiology part 2 (p44-58- Fungal, herpes, PUO, GI, HAI, Prion + Zoonoses) Flashcards
How are fungal infections classified?
Yeasts vs Moulds
Superficial vs systemic
How are superficial fungal infections diagnosed?
Woods Lamp
Key organisms for superficial fungal infections?
Tinea- dermatophyte e.g. tricophyton rubrum: ringworm, athletes foot
Pityriasis- malassezia globossa/furfure- seborrhoeic dermatitis, T versicolor
Key organisms for deep seated fungal infections?
Candida- in immunocompromised
Aspergillus
Cryptococcus- immunocomprosised particularly HIV
How are candida infections diagnosed?
Culture, mannan, antibodies
How are candida infections treated?
Fluconazole for c. albicans and amphotericin-B for invasive disease
How do aspergillus infections present?
Pneumonia esp in immunocompromised- high mortality
How are aspergillus infections diagnosed?
ELISA, PCR, beta-glucan test, grows on czapek dox agar
How are aspergillus infections treated?
Voriconazole
How do cryptococcus infections present in HIV?
Meningitis with insidious onset
What animal are cryptococcus infections associated with?
Birds especially pigeons
How are cryptococcus infections diagnosed?
Cryptococcal antigen in serum/CSF + india ink staining
Tx of cryptococcus infections?
3/52 amphotericin B +/- flucytosine
What are the five different classes of antifungals and what do they target?
Polyene e.g. amphotericin- targets cell membrane integrity Azole- cell membrane synthesis Terbinafine- cell membrane Flucytosine- DNA synthesis Echinocandin- cell wall
How are herpes infections diagnosed?
Blood PCR, histopathology, tissue immunofluorescence, cell culture in human fibroblasts, serology
Treatment of Herpes?
Ganciclovir, cidofovir and foscarnet
How does roseola virus present?
3/7 fever then transient rash
Abx often prescribed for fever then rash blamed on penicillin falsely
Most common cause of febrile convulsions
How is roseola virus diagnosed?
Blood PCR
How does VZV present as chickenpox?
Fever, malaise, headache followed by characteristic rash. Lesions scab after a week
How is chickenpox diagnosed?
Exam- vesicles
Cytology
Immunofluorescence cytology
PCR
What can chicken pox during pregnancy led to?
Congenital varicella syndrome- scarring, hypoplastic limbs, cortical atrophy, psychomotor retardation, choreoretinitis, cataracts
Treatment for chickenpox?
Acyclovir 800mg PO TDS 7/7 in all adults with chickenpox, neonates, immunocompromised, eye involvement or pain
What causes shingles?
VZV reactivation -> stress/decreased immunity
How does shingles present?
Painful rash in specific dermatome
Treatment for shingles?
Acyclovir 800mg PO 5x daily or famciclovir or valaciclovir
Topic eye drops plus oral for opthalmic
PEP for immunocompromised
How does infectious mononucleosis present?
Fever, pharyngitis. lymphadenopathy + maculopapular rash
How is infectious mononucleosis diagnosed?
Blood film, monospot agglutination, EBV antibodies, Paul-Bunnell test
How does Burkitt’s lymphoma present?
African kids with a big jaw
What is the definition of pyrexia of unknown origin?
> 38.3’ fever on several occasions persisting for >3w without diagnosis despite >1w of intensive investigations
4 different types of PUO?
Classical
Healthcare associated- develops in patient following >24h in hospital
Neutropenic PUO (<500/uL)- EMERGENCY
HIV-associated PUO
Examples of classical PUO?
Infections
Neoplasms
CTD
Examples of healthcare associated PUO?
Surgery, drugs, medical devices, LRTI, c diff, immobilisation
Examples of neutropenic PUO?
Chemo Haematological malignancies Fungal Mycobacteria Drug fever
Causes of fever in returning traveller?
Malaria, dengue (rash), typhoid, rickettsia, bacterial diarrhoea, UTI, pneumonia, HIV seroconversion, brucella, viral haemorrhagic fevers (ebola etc)
What pathogen causes typhoid and what would you see on microscopy?
Salmonella typhi- anaerobic gram -ve bacillus
Clinical presentation of typhoid?
Fever, headache, abdo pain, diarrhoea or constipation, rose spots, relative bradycardia, hepatosplenomegaly
How is typhoid diagnosed?
Hx, blood cultures, stool
Management of typhoid?
IV fluids, oral or IV abx
What carries malaria?
Female anopheles mosquito
Bites at night, attracted by heat and CO2. Needs blood proteins for eggs
Most common pathogen causing malara?
Plasmodium falciparum
Common symptoms of p.falciparum malaria?
Fever + rigors Flu-like Headache Back pain Myalgia N+V
Investigations for p. falciparum malaria?
Thick film- find parasitaemia
Thin film- distinguish malaria species
Various antigen tests
Bloods- WCC rarely raised, decreased platelets, deranged LFTs, anaemia
Treatment for P. falciparum malaria?
Mild- quinine + doxycycline/clindamycin or malarone or riamet
Severe- artemisin combination therapy (ACT) or Quinine + doxycycline/clindamycin
Major features of severe malaria?
Impaired consciousness Seizures Renal impairment Acidosis Hypoglycaemia Pulmonary oedema Anaemia Spontaneous bleeding/DIC Shock Haemoglobinuria
What is a common source of clostridia botulinum infection?
Canned/vacuum packed foods- honey or beans
How is c. botulinum treated?
Antitoxin
What is the pathophysiology of c. botulinum?
Toxin blocks Ach release from peripheral nerves -> descending paralysis
What is a common source of c. perfringens infection?
Reheated meats
What is the pathophysiology of c. perfringens?
Superantigen enterotoxin binds to TCR + MHC outside peptide binding site -> massive cytokine production by CD4- systemic toxicity + suppression of adaptive responses -> watery diarrhoea and cramps
What is a common cause of c difficile?
Use of abx e.g. cephalosporins/floroquinones
Treatment of c difficile?
Metronidazole then vancomycin
What is a common source of bacillus cereus infection?
Reheated rice
Treatment for b cereus?
Self limiting
Main virulence factor in staph aureus?
Protein A
Four different types of E Coli?
ETEC- Toxigenic/Travellers
EIEC- Invasive dysentery
EHEC- haemorrhagic
EPEC- paeds
Treatment for E.coli?
Can be self limiting but can treat with ciprofloxacin
Treatment for salmonella?
Ceftriaxone or ciprofloxacin
How does shigella present?
Mainly affects the distal ileum + colon -> mucosal inflammation, fever, pain, bloody diarrhoea
What is a common route of transmission for yersinia enterocolitis?
Food contaminated with domestic animals excreta
Which condition causes ‘rice water stool’?
Cholera
What is the pathophysiology of cholera?
Increased cAMP opens Cl- channel at apical membrane of enterocytes -> efflux of Cl- to lumen
Common sources of camplyobacter jejuni?
Drinking unpasteurised milk or eating food like poultry
Treatment for c jejuni?
Erythromycin or cipro if first 4-5d
Common sources of listeria monocytogenes?
Refrigerated food- unpasteurised dairy or veg
Perinatal infection or immunocompromised
Treatment for listeria monocytogenes?
Ampicillin
Ceftriaxone
Cotrimoxazole
Which GI infection is common in MSMs?
Entamoeba histolytica- flask shaped ulcers on histology
Shigella etc
What GI infection is common in travellers, hikers, MSM and mental hospitals and what is its aetiology?
Giardia lambia- from ingesting cysts from faecally contaminated H2O
Treatment for Giardia lambia?
Metronidazole
How is C diff transmittted?
Spore ingestion
What predisposes c diff infection?
Existing gut flora disturbed by antibiotics- particularly 3Cs- clindamycin, cephalosporin + ciprofloxacin
What is the bowel like in c diff?
Pseudomembranous colitis
How do you treat c diff?
Oral metronidazole
Common UTI HAI?
E. coli- RF is catheter
What is prion disease?
Protein only infectious agent
Prognosis of prion disease?
Leads to rapid neurodegeneration an death in months- currently untreatable
Definition of zoonoses?
Diseases and infections which are transmitted naturally between vertebrate animals and man
What infections are associated with water sports?
Leptospirosis, HAV, Giardia, Toxoplasmosis, Mycobacterium marinum/ulcerans,
Burkholderia pseudomallei, E. coli
What infections are carried by food?
Listeria (cow cheese-human), Taenia, Cysticercosis, toxoplasmosis, trichinellosis,
yersiniosis, Giardia
How is brucellosis transmitted?
Inhalation, skin or mucous membrane contact or consumption of contaminated food (dairy), animal contact
Symptoms of brucellosis?
Fever- undulant (peaks in eve), malaise, rigors, sweating, myalgia, arthralgia, tiredness
Complications of brucellosis?
Endocarditis, osteomyelitis
Signs of brucellosis?
Arthritis, spinal tenderness, lymphadenopathy, splenomegaly, hepatomegaly, epididymo-orchitis
Investigations in brucellosis?
Serology- anti-O polysaccharide antibody, WCC normal, rare leucocytosis, neutropenia
Treatment of brucellosis?
Tetracycline or doxycline combined with streptomycin
What are pathognomonic of rabies?
Negri bodies
What is presentation of rabies?
Prodrome (fever, headache, sore throat) -> encephalitis
Treatment of rabies?
Rabies IgG post exposure
Pathogen that causes plague?
Yersinia pestis
Types of plague?
Bubonic- flea bites human 0 swollen lymph - dry gangrene
Pneumonic- seen during epidemics, person-person
Treatment of plague?
Streptomycin, doxycycline, gentamicin, chloramphenicol
How is leptospirosis commonly transmitted?
Excreted in dog/rat urine. Penetrates broken skin/swimming in contaminated water
Treatment of leptospirosis?
Amoxicillin, erythromycin, doxycycline or ampicillin
What pathogen causes anthrax?
Bacillus anthracis
Symptoms of anthrax?
Painless round black lesions with rim of oedema
Pulmonary- massive lymphadenopathy + mediastinal haemorrhage, pleural effusion and resp failure
What pathogen causes Lyme disease?
Borrelia burgdoferi (spirochaete)
Presentation of lyme disease- early localised, disseminated and late persistent?
Early localised- cyclical fevers, non specific flu like, erythema chronicum migrans (ECM)- Bullseye rash
Early disseminated- malaise, lymphadenopathy, hepatitis, carditits, arthritis
Late persistent- arthritis, focal neurology, neuropsychiatric disturbances
How is Lyme disease diagnosed?
Biopsy edge of ECM + ELISA for Lyme Abs
Treatment of Lyme disease?
Doxycycline 2-3/52
What pathogen causes Q fever?
Coxiella burnetti
How is cutaneous leishmania transmitted?
Sandfly bites- skin ulcer