Infectious Diseases Flashcards
What is meningitis?
Inflammation of the meninges of the brain. Can be a bacterial, viral or fungal cause.
What are the bacterial causes of meningitis in neonates?
E.coli
Group B Strep
Listeria monocytogenes
What are the bacterial causes of meningitis in infants?
Neisseria meningitidis
H.influenzae
Strep pneumoniae
What are the bacterial causes of meningitis in young adults?
N.meningitidis
Strep pneumoniae
What are the bacterial causes of meningitis in the elderly?
Strep pneumoniae
N.meningitidis
Listeria
What are the viral causes of meningitis?
Mumps virus Echo virus Coxsackie virus Other enterovirus Herpes simplex virus
Risk factors for meningitis?
Immunocompromised Elderly Pregnant Malignancy Diabetes Bacterial endocarditis Crowding Intrathecal drug administration IVDU
How does meningitis present?
TRIAD
- headache
- neck stiffness
- fever
Other:
- meningismus (photophobia, neck stiffness)
- reduced GCS
- papilloedema
- intense malaise, fever, riggers, vomiting
- irritable + prefers to lie still
- meningococcal septicaemia (rash)
- seizures
- progressive drowsiness
- positive Kernig’s + Brudzinki’s sign
If viral may be less signs and more self-limiting
How do you diagnose meningitis?
Blood cultures Bloods: FBC, U+E, CRP, serum glucose CT head Lumbar puncture Throat swabs Serum PCR (pneumococcal + meningococcal)
When do you do a CT before LP?
- > 60 years
- immunocompromised
- Hx of CNS disease
- new onset/recent seizures
- decreasing conscious levels
- focal neurological signs
- papilloedema
What are the LP results for bacterial meningitis?
Cells: polymorphs (neutrophils)
Protein: raised
Glucose: low
What are the LP results for viral meningitis?
Cells: lymphocytes
Protein: normal/raised
Glucose: normal
What are the LP results for TB meningitis?
Cells: lymphocytes
Protein: raised
Glucose: low/normal
How do you treat meningitis?
If non-blanching petechial or purpuric rash = meningococcal septicaemia
> immediate IM benzylpenicillin (community)
> immediate IV cefotaxime (hospital)
+ do not perform LP, confirm diagnosis by blood culutres
If bacterial meningitis:
> IV cefotaxime or IV ceftriazone 2-3g QID
(if Hx of anaphylaxis with penicillin, give IV chloramphenicol)
If viral:
> self-limiting
> aciclovir if cause is HSV
When would you add IV amoxicillin to meningitis treatment? And why?
If bacterial cause and patient is: - immunocompromised - >50 years - pregnant In order to cover listeria.
If the cause is likely pneumoccocal for bacterial meningitis, what could you add to the treatment and why?
Oral dexamethasone to reduce cerebral oedema
What do you do with contacts of meningitis patients?
Prophylaxis for close contacts
> oral ciprofloxacin stat (all ages + pregnancy)
> oral rifampicin (all ages but NOT pregnancy)
What are some complications of meningitis?
Hearing loss
Seizures
Developmental problems
What is encephalitis?
Infection and inflammation of the brain parenchyma which affects the extremes of age (children + elderly.)
What causes encephalitis?
Mainly viral:
- herpes simplex virus 1 + 2
- varicella zoster
- EBV, CMV, HIV
- mumps, measles
Non-viral:
- bacterial meningitis
- TB
- malaria
Clinical presentation of encephalitis?
TRIAD
- fever
- headache
- altered mental status
Begins with features of viral infection (fevers, headache, myalgia, fatigue, nausea) and progresses to personality and behavioural changes, decreased consciousness, confusion + drowsiness
How is encephalitis diagnosed?
MRI
EEG
LP
Blood + CSF serology
How is encephalitis treated?
Viral:
> IV aciclovir immediately (don’t wait for results)
Anti seizure medication
e.g. primdone
If suspected meningitis: IM benzylpenicillin
What causes tetanus?
Clostridium tetani
- soil organism, terminal spores
- gram positive anaerobe
- infects via dirty wounds, releasing toxin which translate via peripheral nerve and enter CNS and bind to GABA receptors of inhibitory inter-neurones.
What are the clinical features of tetanus?
- Paraesthesia of wound
- Trismus (lockjaw)
- Opisthotonus (sustained muscle contraction)
- Risus sardonic (involvement of facial muscles)
- Paroxysmal generalied spasms
- Autonomic dysfunction
How do you diagnose tetanus?
Wound culture
How do you treat tetanus?
- debride wound quickly
- benzylpenicilin
- human tetanus immunoglobulin
- spasms: dantolene, baclofen
- control HTN/tachdysrythmia
- ITU/airway mx
How do you prevent tetanus?
Tetanus toxoid
- 3 doses (primary immunisation)
- single booster dose (after wounds if >5 years since primary course or booster)
What is botulism?
Caused by clostridium botulinum, a powerful neurotoxin
- assoc with home-canned fruit/veg or fish products
- IVDU
- descending paralysis with cranial neuropathy first
- diplopia, dysarthria, dysphagia, peripheral weakness
Tx: equine or human antitoxin
What is pneumonia?
Inflammation of the lung tissue and fluid collection within the lungs that results from infection.
What causes pneumonia?
Bacterial
- strep pneumonia (90% of cases)
- staph aureus
- legionella’s
- jirovecci
Viral
- h.influenza
What are the different types of pneumonia?
Community acquired
Hospital acquired
Aspiration (inhaled foreign objects that bring in bacteria)
Who is at risk of pneumonia?
- infants + elderly
- COPD + other chronic lung conditions
- HIV, AIDS
- nursing home residents
- impaired swallowing
- diabetics
- congestive heart disease
- alcoholics and IVDU
Clinical features of pneumonia?
Symptoms
- confusion
- tired
- pleuritic chest pain
- SOB
- headache
Signs
- low BP
- fever
- tachycardia
- high RR
- sputum
Ix for pneumonia?
CXR Auscultation Sputum sample Blood culture Legionella's urinary antigen test (ELISA) Thoracentesis
What is CURB-65?
Assess the severity of CAP and increased likelihood of a patient’s 30 day mortality rate:
- Confusion
- Urea >7
- RR >/30
- BP <90/60
- > /65 years
1 point for each
How do you treat a pt who scores 0-2 on curb65?
Oral amoxicillin as an outpatient
How do you treat a pt who scores 3-4 on curb65?
Oral amoxicillin + clarithromycin
How do you treat a pt who scores 5 on curb65?
IV co-amoxiclav + clarithromycin
How do you treat a pt with legionellas pneumonia?
Fluoroquinolone + clarithromycin
What causes TB?
Mycobacterium tuberculosis
Mycobacterium bovis
What is a Gohn focus?
A lung lesion that forms in primary TB composed of tubercle-laden macrophages. It becomes a Gohn complex when it’s: Gohn focus + hilar lymph nodes.
Usually heals by fibrosis.
Clinical features of TB?
Weight loss Night sweats Fever Cough Haemoptysis
- lymph node swelling + discharge
- painful swollen joints (Potts)
- ascites
- epididymitis, dysuria, haematuria
Ix for TB?
Ziehl-Neelsen stain for acid fast bacilli
CXR
What is seen on CXR in TB?
- consolidation
- cavitation
- calcification
- pleural effusion
How do you treat TB?
Rifampicin (6months)
Isoniazid (6 months)
Pyranzinamide (2months)
Ethambutol (2months)
SE of TB medication?
Rifampicin: red urine, hepatitis
Isoniazid: hepatitis, neuropathy
Pyranzinamide: hepatitis, arthralgia/gout, rash
Ethambutol: optic neuritis
How do you screen for TB?
Mantoux test (for latent TB) Interferron gamma blood test
What is infective endocarditis?
Infection of heart valves or other endocardial lined structures within the heart.
RF for IE?
- IVDU
- poor dental hygiene
- skin + soft tissue infection
- dental treatment
- IV cannula
- cardiac surgery
- pacemaker
- prosthetic heart valve patients
What organisms cause IE?
Staph aureus!! Pseudomonas aeruiginosa Strep viridians (dental problems)
Clinical presentation of IE?
New valve lesion/regurgitate murmur Fever Valve dysfunction Embolic events Haematuria Finger clubbing Headache, malaise, confusion, night sweats
Peripheral stigmata of IE?
- splinter haemorrhages
- osler nodes
- laneway lesions
- roth spots
- petechiae
- embolic skin lesions
How do you diagnose IE?
DUKE’S CRITERIA is used
Blood cultures
- 3 sets from different sites over 24hours
- do this before Abx are started
Bloods
- CRP + ESR (raised)
- Normochromic normocytic anaemia
- Neutrophilia
Transoesophageal echo (better at diagnosing) Transthoracic echo
Urinalysis
- haematuria
CXR
- cardiomegaly
ECG
- long PR interval
How do you treat IE?
Abx for 6 weeks
Staph: IV vancomycin + rifampicin
Non-staph: IV benzylpenicillin + gentamicin
Treat complications (arrhythmias, heart failure etc)
Surgery
- remove valve
Good oral health
What is Duke’s criteria?
Either need: - 2 major - 1 major + 3 minor - 5 minor to diagnose a definite IE
What are some major criteria in dukes?
- bugs grown from blood cultures
- evidence of endocarditis on echo, or new valve leak
What are some minor criteria in dukes?
- predisposing factors
- fever
- vascular phenomena
- immune phenomena
- equivocal blood cultures
What is HIV?
A sexually transmitted disease. Often has a long, latent and dormant period which is very prone to mutations.
It is a retrovirus the contains RNA.
How do you diagnose HIV?
CD4 count (low) Viral load (high)
Why is the CD4 count used in HIV?
The CD4 cells are T-helper lymphocytes which are attacked by the HIV virus. Therefore a low CD4 count suggests it has been affected by the virus.
What is AIDs?
Acquired Immune Deficiency Syndrome
- diagnosed when the CD4 count <200 or by presence of AIDS-defining illness
What are the AIDs defining illnesses?
- PCP
- CMV
- TB
- Kapos’s sarcoma
- Lymphoma
How is HIV treated?
Anti-retroviral therapy
(HAART) started regardless of CD4 count.
- 2 NRTIs with an integrate inhibitor, an NNRTI or a PI
What are some combination drugs made for HIV tx?
Truvada (tenofovir + emtricitabine)
Kivexa (abacavir + latitudine)
What prophlyaxis is given to pt with CD4 count <200?
Co-timoxazole
Nebulised pentamidine
Azithromycin
Ganciclovir
How is Hep B transmitted?
Vertical Horizontal - sexual - blood transfusions - needles/sharps - shared razors or toothbrushes
Explain the different antigens in Hep B?
Surface antigen
- protein found in blood of pt that have CURRENT infection (diagnostic confirmation)
- can be genetically produced to be used as a vaccine
Envelope antigen
- allows assessment of phase of infection
Core antigen
- not used diagnostically
What are the different antibodies found in Hep B?
Surface antibody
- indicates immunity to hep B following immunisation or infection
Envelope antibody
- appears in later phase of both acute/chronic disease ad evidence of immune response
Core antibody
- found in most people exposed to HBV
- IgM = acute infection
- IgG = chronic infection
What is HBV DNA?
Measured and quantified by nucleic acid testing such as PCR.
Helps determine the grade of replication + activity of the virus.
What treatments are used in Hep B?
Pegylated interferon alpha
- weekly injectable for 48 weeks
Oral agents (daily long term)
- tenofovir
- entecavir
What is the main mode of transmission for hep C?
parenteral
- IVDU
Clinical features of hep c?
Mostly asymptomatic Malaise Nausea RUQ apin Jaundice
How is hep C diagnosed?
Enzyme immunoassay serology
Immunoblot assay
PCR for HCV RNA
What can chronic HCV infection develop into?
ESLD
What other tests are done for HCV patients?
Liver fibrosis assessment
- fibroscan
Liver biopsy
HCC screening
OGD to look for varices if evidence of portal hypertension
What is involved in hepatocellular carcinoma screening?
6 monthly AFP testing + liver USS
Difference in tx aim in HBV + HCV?
HBV: control not cure
HCV: cure
How is a cure defined in HCV?
Undetectable HCV RNA in blood 12 weeks after the end of treatment
What is HCV treatment?
Direct acting antiviral drugs which act on specific HCV viral enzymes and prevent its replication
- NS3/4A inhibition (-previr)
- NS5A inhibitors (-asvir)
- NS5B (-buvir)
What are the 5 species that cause malaria?
- plasmodia falciparum (most common)
- plasmodia ovale
- plasmodia viva
- plasmodia malariae
- plasmodia knowlesi
Clinical features of malaria?
Fever N+V+diarrhoea Headache, myalgia, fatigue Chills + sweats Hepatosplenomegaly Blood in urine Anaemia + jaundice
How do you diagnose malaria?
3 thin + thick blood films at least 24 hours apart
FBC, U+E, LFT, glucose, lactate + clotting
Blood cultures
Blood gas
What does the thick film tell you in malaria testing?
- determines whether the parasite is present
- calculate the parasitaemia %
What does the thin film tell you in malaria testing?
- determines morphology + plasmodium species present
How is uncomplicated malaria treated?
PO riamet
or
PO quinine + doxycycline
How is a benign malaria treated?
PO chloroquine
Give Primaquine for P.vivax and ovale hypnozoites
How is complicated malaria treated?
IV Artesunate
Once patient improved and tolerating oral medications this can be switched to Artemether-lumefantrine (Riamet) or Quinine and doxycycline
How would you monitor someone’s response to malaria treatment?
- Monitoring the patient clinically (routine observations, daily symptom review etc.)
- 12 hourly blood films to monitor the parasitaemia.
- Daily bloods to monitor for evidence of anaemia, clotting derrangements and developing end organ failure.
What are some major features of complicated/severe malaria?
- Imparied GCS or seizures
- Renal impairment
- Acidosis (pH <7.3)
- Hypoglycaemia
- Pulmonary oedema or ARDs
- Haemoglobin (<80g/L)
- Disseminated intravascular coagulation/ spontanous bleeding
- Shock (BP <90/60)
- Haemaglobinuria
- Parasitaemia >10%
What anti-malarials can be used for prophylaxis?
Proguanil Doxycycline Mefloquine Chloroquine and/or proguanil Atovaquone/proguanil
