Infectious Diseases Flashcards
Name six gram positive bacteria.
Staphylococcus (including aureus, epidermis, viridans) Strep pneumoniae Strep pyogenes Strep viridans Diphtheria C.difficile
Name eight gram negative bacteria.
Bordetella pertussis Escherichia coli, shigella, salmonella Haemophilus influenzae Vibrio cholerae Legionella pneumoniae Heliobacter pylori Chlamydia Neisseria
What are the six subtypes of E.coli infection?
Enterotoxigenic (traveller's diarrhoea) Enteropathogenic Enterohaemorrhagic Enterioinvasive Enteroaggregative Uropathogenic
What type of bacteria is Neisseria?
Gram negative non-flagellated diplococci
What is primary complex TB?
Granuloma + inflammation in the lymphatics and lymph nodes
What are three risk factors for tuberculosis?
HIV
Malnutrition
CKD
What type of bacteria causes tuberculosis?
Acid-fast aerobic mycobacteria
What are the pulmonary symptoms of tuberculosis?
Productive cough + haemoptysis
Weight loss, fever, sweats
Hoarse voice
Pleuritic pain
What does CXR show in a patient with tuberculosis?
Consolidation
Cavitation
Pleural effusion
Thickening/widening of mediastinum
Which nodes are infected in TB following pulmonary infection?
Extrathoracic
Cervical
Supraclavicular
Which patients with TB develop GI symptoms?
Immunocompromised
Ethnic minorities
What can develop after typical TB infection?
Bone/spine involvement Tuberculus meningism Tuberculus peritonitis Pericardial TB Miliary TB
What stain is used to rapidly identify TB mycobacteria in a sample?
Auramine-phenol
How is TB diagnosed?
Sample culture
PCR: rapid and sensitive. Confirms species e.g. TB v non-tuberculus mycobacteria
What is the treatment of TB?
2 months isoniazid, ethambutol, rifampicin, pyrazinamide
4 months isoniazid and rifampicin
What is the treatment of latent TB?
6 months isoniazid or 3 months isoniazid and rifampicin
What are the side effects of rifampicin and isoniazid?
Rifampicin - oral contraceptive not effective. Stains body secretions pink
Isoniazid - polyneuropathy
What are the side effects of ethambutol and pyrazinamide?
Ethambutol - optic retrobulbar neuritis
Pyrazinamide - hepatic toxicity
How is latent TB diagnosed?
Tuberculin skin test shows a raised indurated lesion (delayed hypersensitivity reaction)
What is multidrug resistant TB?
TB that is at least resistant to isoniazid and rifampicin
How is contact screening performed for a TB patient?
Mantoux test
Quantiferon/Elispot - interferon gamma release assay (IGRA)
What colour is sputum in pneumococcal pneumonia?
Rusty
What are three signs of pneumonia on examination?
Lung consolidation on percussion and auscultation
Crackles +/- wheeze
Bronchial breathing
What score is used to grade severity of pneumonia?
CURB-65
What is the treatment of mild, moderate, and severe pneumonia?
Mild - PO amoxicillin (macrolide/tetracycline if allergic)
Mod - PO amoxicillin + macrolide
Severe - IV co-amoxiclav/cefuroxime + macrolide
Give three examples of macrolide antibiotics.
Erythromycin
Clarithromycin
Azithromycin
What are the signs of empyema?
Pleuritic pain
Signs of pleural collection - dull to percussion and decreased air entry
Thoracocentesis of empyema shows what?
pH<7.2
Glucose <3.3mmol/L
Pus
LDH>1000iu
How is hepatitis B transmitted?
Vertical transmission - during parturition or soon after
Horizontal transmission - close contact, sharps, sexual
What is the presentation of acute hepatitis B infection?
Subclinical usually
Fever, jaundice, rash, arthralgia
Extra-hepatic manifestations - PAN or glomerulonephritis
What is the function of the following antigens and antibodies?
1) HBsAg and HBsAb
2) HBeAg and HBeAb
1) Surface antigen = infection
Surface antibody = immunity
2) Envelope antigen = assess phase of infection Envelope antibody = evidence of immune response as appears in the later phase of acute or chronic disease.
What is the function of HBV DNA?
Quantified by PCR, helps determine viral activity
What is the function of HBcAb (core antibody)?
Identifies exposure - previous, current, chronic etc
How is Hepatitis B usually managed?
Usually none, or supportive
What percentage of Hepatitis B patients do not clear the virus?
1-10% - they develop chronic infection and fulminant hepatitis
What patient groups are more at risk of developing chronic hepatitis B infection?
Neonates
Child below 5 years
How is chronic hepatitis B diagnosed?
Moderate rise in aminotransferases and ALP
Ground glass appearance of liver
HBsAg and HBcAb found
What is required for Hepatitis D to replicate?
Hepatitis B
How is chronic Hepatitis B managed?
48 weeks PEGylated alpha-2alpha interferon
Entacavir or tenofovir disoproxil - more likely this as less side effects
In chronic hepatitis B infection, what is a marker of fulminant hepatitis?
Increasing INR
How is hepatitis C transmitted?
Blood/blood products - parenteral
What is the presentation of acute hepatitis C?
Flu-like illness
Jaundice and RUQ pain
What percentage of patients with acute hepatitis C develop chronic disease and end stage liver disease?
66%
33% in first 25 years
What suggests a patient is less likely to clear the virus and will progress to end stage liver disease?
They are asymptomatic in the acute stage.
Co-existing hepatic pathology
HIV
African American
What are the extra-hepatic manifestations of hepatitis C?
Essential mixed cryoglobulinaemia
Membranoproliferative glomerulonephritis
Porphyria cutanea tarda
Autoimmune thyroid disease
How is hepatitis C diagnosed?
Enzyme immunoassay
Immunoblot assay for HCV antibody
PCR for HCV RNA
How is liver fibrosis assessed in chronic hepatitis C?
Assessment of transient liver elastography: Fibroscan
What are the details of hepatocellular carcinoma screening in patients with advanced fibrosis or cirrhosis?
6 monthly alpha-FP
Liver USS
The aim of Hepatitis C treatment is to cure. Define cure:
Undetectable HCV RNA in blood 12 weeks post treatment (suggests a sustained virological response)
What is the treatment of Hepatitis C?
2+ Direct-Acting Antivirals (DAAs) for 8-16 weeks
May have the addition of ribavarin
Give an example of DAAs for Hepatitis C?
Harvoni: ledipasvir (NS5A inhibitor) and sofosbuvir (NS5B inhibitor)
In pregnant patients with HIV, what value of viral load makes vaginal delivery a possibility?
Undetectable viral load
What are three risk factors for HIV?
Multiple sexual partners
Sharing needles
MSM
What may be the first presentation of HIV?
Generalised lymphadenopathy
Acute generalised rash on palms and soles
Oral candida/herpes simplex
Recently developed seborrheic dermatitis/psoriasis
Odd looking mouth lesions
How is HIV tested for?
Venous blood sample - HIV antibodies are detected in serum 4 weeks post exposure
What are the three phases of HIV?
1) Acute primary infection
2i) Asymptomatic phase
2ii) Early symptomatic HIV
3) AIDS
Define AIDS.
CD4+ count <200 or presence of an AIDs defining illness
What viral load suggests uncontrolled HIV?
> 500,000 copies
What are the main risks once CD4+ count falls below 50?
Mycobacterium avium intracellulare (MAI)
CMV
Where does the HIV virus replicate?
Genital tract
CNS
Bone marrow
GI tract
Name two bacterial AIDS-defining conditions in adults.
Mycobacterium tuberculosis
MAI
Name two viral AIDS-defining conditions in adults.
CMV other than liver, spleen, or nodes
HSV chronic ulcer >1m or bronchitis, pneumonitis, or oesophagitis
Name three other AIDS-defining conditions.
Candidiasis of bronchi, lungs, or oesophagus
Histoplasmosis
Toxoplasmosis of brain
PCP - fungal
Name three AIDS-defining malignancies.
Cervical carcinoma
Burkitt’s lymphoma
Kaposi’s sarcoma
What are three side effects of HAART?
Lipodystrophy
Lactic acidosis
Insulin resistance
Define persistent generalised lymphadenopathy.
Enlarged lymph nodes involving at least 2 non-contingous sites other than inguinal nodes.
Name six conditions that may present during the early symptomatic HIV (Phase 2ii).
Oral hair leukoplakia Varicella zoster virus >2 episodes Cervical dysplasia Bacillary angiomatosis Pelvic inflammatory disease ITP
Which virus is oral hair leukoplakia associated with?
EBV
What type of retinitis can be seen in HIV?
CMV
Toxoplasma
What is the most common combination of HAART drugs for treatment of HIV, and give an example?
NRTI backbone (2NRTIs) plus one of:
- Integrase inhibitor
- NNRTI
- Protease inhibitor
E.g. tenofovir+emtricitabine PLUS raltegravir
What is a NRTI and give an example.
Nucleoside reverse transcriptase inhibitor
Abacavir
What is post-exposure prophylaxis?
4 week HAART treatment given to patients who are HIV seronegative but have had a high risk exposure
Which antibiotic is given as prophylaxis against PCP pneumonia?
Co-trimoxazole
What is the name given to the malaria parasite when inside the mosquito, inside the liver, and inside RBC?
Mosquito: sporozoites
Liver: merozoites
RBC: gametocytes
How does a virus evade host defence mechanisms?
Antigenic variability
Prevention of host cell apoptosis
Down regulation of interferon production
What is the function of complement proteins in the humoral immune response?
Opsonisation and lysis
How does a bacterium evade host defence mechanisms?
Secrete proteases that lyse IgA
Polysaccharide capsule prevents phagocytosis
Antigenic variation
Secretion of elastase inhibits C3a and C5a
What are the symptoms of Dengue fever?
Fever
Headache
Severe MSK pain
Rash
What is the aetiology of Dengue fever?
RNA flavivirus using aedes mosquito as a vector
Name two transmissible haemorrhagic viruses.
Ebola
Lassa fever
What are the two types of trypanosomiasis?
South American - Chagas disease
African - Tsetze fly
How is malaria transmitted?
The bite of the female anopheles mosquito that is infected with plasmodia spp
Following a bite, what is the pathogenesis of malaria?
Merozoites are released into the bloodstream and infect red blood cells every 72 hours
What are the symptoms of malaria?
Fever, sweats, headache, fatigue, myalgia
Nausea, vomiting, diarrhoea
Anaemia, jaundice, hepatosplenomegaly
Dark urine
How is malaria diagnosed?
Mildly raised ALT/AST
Low platelets and anaemia, low glucose
Hyperbilirubinaemia
Thick and thin blood films identify species
Blood cultures
MSU, CXR, stool culture for ovum, parasites, cysts
What are the signs and symptoms of cerebral malaria?
Increased ICP and shock
Hypoglycaemia and coma
Convulsions
ARDS
Why are malaria patients hypoglycaemic?
The parasite utilises glucose.
What is the treatment of non-falciparum malaria?
Chloroquine OR
Artemisinin based combination therapy (ACT) - includes artesunate and amodiaquine
What is the treatment of uncomplicated falciparum malaria?
Artemisinin based combination therapy (ACT) - artesunate and amodiaquine
What is the treatment of complicated falciparum malaria?
IV artesunate
What is the treatment of toxoplasma?
Sulfadiazine and pyrimethamine
What is the treatment of amoebiasis?
Metronidazole
What is the treatment of trypanosomiasis?
Pentamidine
What is the treatment of giardiasis?
Metronidazole
What is the treatment of schistosomiasis?
Praziquantel
What is the treatment of pinworms/threadworms?
Mebendazole or pyrantel
Give five causes of drug induced fever?
Malignant hyperthermia from general anaesthetic Lamotrigine/progesterone Neuroleptic malignant syndrome Serotonin syndrome Cocaine
What is the cause of malignant hyperthermia?
AD inherited myopathy due to ryanodine receptor gene on chromosome 19
What are five symptoms and signs of malignant hyperthermia?
Tachycardia Hypoxia and hypercapnia Fever Muscular rigidity Hypotension
How is malignant hyperthermia managed?
Give 100% oxygen Deepen anaesthesia with opioids IV dantrolene Correct blood gases and arrhythmias Cool patient
Which antibiotic is recommended to treat invasive (bloody) diarrhoea?
Ciprofloxacin
How do you monitor the response to treatment of a malaria patient?
Parasite count
What must you check for before initiating anti-malarials?
Glucose 6-phosphate dehydrogenase deficiency
Name the most common anti-malarial drug.
Malarone - atovaquone and proguanil
What is seen in legionella pneumonia?
Hyponatraemia
Increased transaminases
What does mucous in the stool suggest?
Malabsorption/giardia
How is PCP pneumonia diagnosed?
Sputum sample for detection of the fungus using silver staining of the cyst wall. If no sputum can be aspirated then broncholavage for deep lung tissue
High resolution CT
What is the most common cause of infective endocarditis?
S.aureus/strep.viridans
How do you differentiate between staph and strep with the catalase test?
Staph: catalase positive
Strep: catalase negative
How do you differentiate staph aureus from other types of staph?
Staph aureus: coagulase positive
Staph epidermis: coagulase negative
What is the treatment of c.difficile?
Metronidazole or vancomycin
What are three risk factors for development of c.difficile?
Clindamycin/penicillin
PPIs
Increasing age
How does Parvovirus B19 infection present in children and adults?
Children - slapped cheek rash
Adults - lacy macular widespread rash, rheumatoid-like arthritis