Infectious diseases Flashcards
What is infective endocarditis
Infection of endocardium or vascular endothelium of heart
Risk factors for infective endocarditis
- IV drug use
- IV cannula
- Poor dental hygiene
- Dental treatment
- Skin and soft tissue infection
- Cardiac surgery
- Pacemaker
- Prosthetic valves (aortic and mitral)
- Congenital heart disease
Causes of infective endocarditis
- Staph. Aureus IVDU, diabetes and surgery
- Staph. Viridans dental problems
- Strep. Mutans poor oral dentition
- Pseudomonas aeruginosa
- Candida albicans immunocompromise
- Staph. Epidermis prosthetic valve
Presentation of infective endocarditis
- Headache
- Fever
- Malaise
- Confusion
- Night sweats
- Joint pain and abscesses
Examination findings in infective endocarditis
- Finger clubbing
- Roth spots = retinal haemorrhages with white or clear centres
- Osler nodes = tender nodules in digits
- Murmur
- Janeway lesions = haemorrhages and nodules in fingers
- Anaemia
- Nail haemorrhages (splinter)
- Emboli
- Embolic skin lesions = black spots on skin
- Petechiae = small red/purple spots caused by bleeds in skin
Investigations of infective endocarditis
- Use Dukes criteria
- Blood cultures = 3 sets from different sites over 24 hrs before antibiotics started
- Bloods CRP and ESR raised, Normochromic and normocytic anaemia, Neutrophilia
- Urinalysis = Look for haematuria
- CXR = Cardiomegaly
- ECG = Long PR interval at regular intervals
- Transoesophageal echo Visualising mitral lesions and possible development of aortic root abscess
Duke’s criteria for infective endocarditis
Major criteria:
- Persistently +ve blood culture for typical organisms
- ECHO shows vegetation, dehiscence, abscess
- New valvular regurgitation murmur
- Coxiella burnetii infection
Minor criteria:
- Predisposing heart condition or IVDU
- Fever >38
- Emboli to organs/brain, haemorrhages
- GLomerulonephritis, Osler’s nodes, Roth spots, rheumatoid factor
- Positive blood cultures that do no meet specific criteria
Diagnosis using Duke’s criteria
2 major
1 major and 3 minor
5 minor
Histological findings
+ve gram stain or cultures from surgery or autopsy
Management of infective endocarditis
- Consult microbiologist
- Antibiotic treatment for 4-6 weeks
o Staphylococcus = vancomycin and rifampicin
o Not staph = penicillin (Benzylpenicillin and gentamycin) - Treat complications = stroke rehab, abscess drainage
- Surgery = Removing valve and replacing with prosthetic one
o Operate if infection cannot be cured with antibiotics
o Operate to remove infected devices
o Operate to remove large vegetations before they embolise
Prevention of infective endocarditis
Good oral health
Complications of infective endocarditis
- Stroke
- Pulmonary embolus
- Bone infections
- Kidney dysfunction
- MI
- Arrhythmia
- Heart failure
- Heart block
Risk factors for tuberculosis
- Origination from high-prevalence country
- Immunosuppression (HIV/medications)
- Homeless, alcoholics, IVDU, prisoners
- Children
- Malnutrition
- Smoking
- Close contact to someone with active TB
Causes of tuberculosis
- Mycobacterium tuberculosis (aerobic acid-fast bacilli)
- Mycobacterium bovis
- Mycobacterium africanum
- Mycobacterium microti
Presentation of TB
- Fever and night sweats
- Anorexia and weight loss
- Productive cough (>3weeks) with occasional haemoptysis
- Malaise
- Breathlessness
- Pleuritic pain
- Hoarse voice = laryngeal involvement
- Clubbing
- Erythema nodosum
- Consolidation (pleural effusion)
- Lymphadenopathy
- Bone/joint pains, back pain and joint swelling
- Abdo/pelvic pain, constipation, bowel obstruction
- Sterile pyuria
CXR in TB
Cavitation
Pleural effusion
Mediastinal/hilar lymphadenopathy
Parenchymal infiltrates in upper lobes
Other investigations in TB
Sputum culture (x3) Ziehl-Neelsen stain for acid and alcohol-fast bacilli = turns bright red against blue background
Screening tests for TB
- Mantoux test = previous vaccination, latent or active TB
o If positive then indicated immunity and thus contact with TB - Interferon gamma release assays
o Used when no features of active TB but positive Mantoux test to confirm latent TB
Causes of false negative mantoux test
immunosuppression
sarcoidosis
lymphoma
extremes of age
fever
hypoalbuminaemia
anaemia
Risk factors for developing active TB from latent TB
silicosis
chronic renal failure
HIV positive
solid organ transplantation with immunosuppression
IVDU
haematological malignancy
anti-TNF Tx
previous gastrectomy
Management of active TB
- Notify PHE and contact tracing
- Rifampicin (6 months)
- Isoniazid (6 months)
- Pyrazinamide (2 months)
- Ethambutol (2 months)
Side effects of rifampicin
red urine, hepatitis, drug interactions
Side effects of isoniazid
hepatitis and peripheral neuropathy
o Prescribe pyridoxine (vit B6) as well
Side effects of pyrazinamide
hepatitis, hyperuricaemia (gout), rash
Side effects of ethambutol
colour blindness and reduced visual acuity
Treatment of latent TB
o 3m isoniazid (with pyridoxine) and rifampicin <35y if hepatotoxicity concern
o 6m isoniazid (with pyridoxine) HIV or transplant
Prevention of TB
- Active case finding to reduce infectivity
- Test for other infectious diseases = HIV, Hep B/C
- Vaccination = Neonatal BCG
Epidemiology of infective diarrhoea
- Highest prevalence in South Asia and Africa
- Tends to be children and elderly
Risk factors for infective diarrhoea
- Foreign travel
- PPI and H2 antagonist use
- Crowded area
- Poor hygiene
- Immunocompromised
- Reduced gastric acid secretion
Causes of infective diarrhoea
- Viral = Rotavirus (children), norovirus (adults), adenovirus, astrovirus
- Bacterial = campylobacter jejuni, E.coli, salmonella, shigella spp, C. diff
- Parasitic = Giardia lamblia, Entamoeba histolytica, Cryptosporidium
Presentation of infective diarrhoea
- Watery diarrhoea
- Blood usually indicates bacterial infection (Salmonella, E.coli and shigella)
- Vomiting
- Abdominal pain
- Viral = Fever, fatigue, headache, muscle pain
- Life-threatening Toxic megacolon and perforation
Investigations for infective diarrhoea
- Low MCV and/or Fe deficiency = coeliac disease or colon cancer
- High MCV if alcohol abuse or decreased B12 absorption = coeliac disease or Crohn’s
- Raised WCC if parasites
- Raised ESR and CRP indicate infection, Crohn’s, UC or cancer
- Stool culture if suspect bacteria, parasites or C.diff toxin
- Sigmoidoscopy with biopsy
Management of infective diarrhoea
- Oral rehydration and avoid high-sugar drinks in children
- Antibiotics (C.diff)
o Oral vancomycin for 10 days
o Oral fidaxomicin (if recurrent infection within 12 wks)
o Oral vancomycin + IV metronidazole (Life-threatening) - Anti-motility agents = loperamide hydrochloride
- Anti-emetics = metoclopramide
Cause of enteric fever (typhoid)
Salmonella (transmitted via faecal-oral route)
Presentation of enteric fever
- Headache
- Fever
- Arthralgia
- Relative bradycardia
- Abdominal pain, distension
- Constipation ± diarrhoea
- Rose spots
Management of enteric fever
Ciprofloxacin
Complications of enteric fever
- Osteomyelitis (esp in sickle cell)
- GI bleed/perforation
- Meningitis
- Cholecystitis
- Chronic carriage
Risk factors for cholera
- Foreign travel to Africa, Asia, Middle East and South America
- Shellfish
Cause of cholera
Vibro cholerae (gram neg)
Presentation of cholera
- Profuse ‘rice water’ diarrhoea
- Dehydration
- Hypoglycaemia
- Hypokalaemia
- Metabolic acidosis
Management of cholera
- Oral rehydration therapy
- Antibiotics: doxycycline, ciprofloxacin
Risk factors for legionella
- Air conditioning systems
- Foreign holidays
Presentation of legionella
- Flu-like symptoms (fever)
- Dry cough
- Relative bradycardia
- Confusion
- Lymphopaenia
- Hyponatraemia
- Deranged LFTs
Investigations for legionella
- Urinary antigen
- CXR mid-to-lower zone predominance of patchy consolidation, pleural effusions
Management of legionella
Erythromycin/clarithromycin
Cause of malaria
- Plasmodium falciparum (severe)
- Plasmodium vivax (benign)
- Plasmodium ovale
- Plasmodium malariae
Risk factors for malaria
- Foreign travel
Protective factors for malaria
- G6PD deficiency
- HLA-B53
- Absence of Duffy antigens
- Sickle cell trait
Presentation of malaria
- Fever on alternating days
- Headache
- Myalgia
- Hepatomegaly
Cause of Hepatitis A
Infective hepatitis caused by RNA picornavirus via ingestion of contaminated food or water
Risk factors for hepatitis A
- Shellfish
- Travellers
- Food handlers
- Household contact
- Sexual contact
- Overcrowding and poor sanitation facilitate spread
- Injecting drug use
Pathophysiology of hepatitis A
- Spread via faecal-oral route
- Short incubation period = 2-6 weeks
- Causes acute hepatitis only (3-6 wks)
- 100% immunity after infection
Presentation of Hep A
- Flu-like prodrome
- Abdominal pain (RUQ)
- Nausea and vomiting
- Anorexia
- Fever
- Malaise
- Jaundice
- Tender Hepatosplenomegaly
Investigations for Hep A
- Bloods = low WCC, raised ESR
- LFTs = raised serum bilirubin, bilirubinuria and raised serum AST/ALT
- Viral markers = Hep A virus antibodies, Anti-HAV IgM
Management of Hep A
- Supportive treatment = resolves in 1-3 months
- Basic analgesia
- Avoid alcohol
Prevention of Hep A
- Vaccination + booster 6-12m later
o People travelling to or going to reside in areas of high prevalence
o Chronic liver disease
o Haemophilia
o MSM
o IVDU
o Occupational risk: lab workers, sewage workers, work with primates - Good hand hygiene
Risk factors for Hep B
- Healthcare personnel
- Emergency and rescue teams
- CKD/dialysis patients
- Travellers
- Homosexual men
- IV drug users
Transmission of Hep B
- Blood borne transmission
o Needle stick/sharing needles (IVDU, tattoos)
o Sexual intercourse
o Blood products
o Vertical transmission = mother to child in utero/soon after birth - Horizontal transmission
o Particularly in children
o Minor abrasions or close contact with others
o HBV can survive on household articles (toys, toothbrushes) for prolonged periods of time
Pathophysiology of hep B
- HBV (DNA) found in semen and saliva
- Following infection, 1-10% of patients not clear virus chronic Hep B cirrhosis and decompensated cirrhosis and liver failure
- Both cirrhosis and chronic infection can lead to hepatocellular carcinoma
- Chronic Hep B will result in continuing hepatocellular damage
Presentation of Hep B
- Nausea
- Fever
- Malaise
- Anorexia
- Arthralgia
- Rashes = urticaria and polyarthritis affecting small joints
- After 1-2 weeks jaundice
- Hepatosplenomegaly
Investigations for Hep B
- HBsAg present 1-6 months after exposure
- HBsAg presence for more than 6 months = carrier status/ chronic infection
- Anti-HBs = immunity (exposure or immunisation), negative in chronic infection
- Anti-HBc = previous or current infection
- IgM anti-HBc = acute or recent infection, present for 6m
- HbeAg = marker of infectivity
Management of acute Hep B
o Supportive + monitor LFTs
o Avoid alcohol
o Manage close contacts by giving human normal immunoglobulin for Hep B and vaccination
o Monitor HBsAg at 6 months to ensure there is full clearance and no progression
o Majority will get spontaneous resolution and will not progress to chronic infection
Management of chronic Hep B
o SC pegylated interferon-alpha 2A weekly = immunomodulatory
o Oral Nucleos(t)ide analogues daily (tenofovir)= inhibit viral replication
Prevention of Hep B
- Antenatal screening of pregnant mothers
- Screening and immunisation of sexual and household contacts
- Universal childhood immunisation
- Universal screening of blood products
- Sterile equipment and universal precautions in healthcare
- Immunisation of healthcare workers and other risk groups
Complications of Hep B
- Cirrhosis
- Liver failure
- Hepatocellular carcinoma
Hep D
RNA virus that can only survive in patient with hep B transmitted by blood-borne
Risk factors for Hep C
- People with haemophilia treated before screening of blood products was introduced
- IV drug users
- Men, HIV, high viral load, alcohol = more severe infection
Presentation of Hep C
- Most acute infections asymptomatic
- 10% have mild flu-like illness
- Jaundice
Investigations for Hep C
- HCV antibody = Present with 4-6 weeks
o False negative in immunosuppressed and in acute infection - HCV RNA = current infection
- Rise in aminotransferases
- Fibroscan for cirrhosis
- Ultrasound for hepatocellular carcinoma
Management of Hep C
- Acute HCV = conservative if viral load falling
- If HCV RNA doesn’t decline then SC Pegylated interferon-alpha 2A/B + oral ribavirin
- Interferon based drugs have many mental side effects so direct acting antiviral treatment without interferon better
- Triple therapy with direct acting antivirals (oral)
o NS5A inhibitor = ledipasvir
o NS5B = sofosbuvir
Prevention of hep C
- No vaccine
- Previous infection doesn’t confer immunity = re-infected
- Screen blood products
- Precaution when handling body fluid
- Lifestyle modification = needle exchanges
- Treatment and cure of ‘transmitters’
Hep E
RNA virus transmitted by faecal oral route usually spread by contaminated water, rodents, dogs and pigs
Risk factors for meningitis
- Immunocompromised renal failure
- Extremes of age
- Pregnant
- Bacterial endocarditis
- Crowding
- Diabetes
- Malignancy
- IV drug abuse
Causes of meningitis
- Adults and children
o Neisseria meningitides = gram-neg diplococci
o Streptococcus pneumonia
o Haemophilus influenza - Pregnant women/older adults Listeria monocytogenes
- Neonates E.coli, Group B haemolytic streptococcus
- Immunocompromised
o Cytomegalovirus
o Crytococcus neoformans
o TB
o HIV
o Herpes simplex virus - Other viral causes: non-polio enteroviruses, mumps, measles
Presentation of meningitis
- Triad = Headache, neck stiffness and fever
- Acute bacterial infection
o Onset typically sudden
o Intense malaise, fever, rigors, severe headache, photophobia and vomiting = within hrs/mins
o Patient irritable and prefers to lie still
o Papilloedema
o Positive Kernig’s and Brudzinski’s sign can appear within hrs
o Non-blanching petechial + purpuric skin rash = meningococcal septicaemia
o Altered mental state with high fever = often absent
o Neonates = hypotonia, poor feeding, lethargy, hypothermia, bulging fontanelle - Viral meningitis
o Benign, self-limiting condition lasting 4-10 hrs
o Headache may follow for some months
o Photophobia
o Confusion
Investigations for meningitis
- Blood cultures before lumbar puncture
- Lumbar puncture at L4
o If unable to perform within 30 mins give empirical antibiotics
o Can give headache, paresthesia, CSF leak and damage to spinal cord
o <1m presenting with fever
o 1-3m with fever and unwell
o <1y with unexplained fever and other features of serious illness - CT pre LP = Focal neurological signs
- Blood tests = FBC, U+Es, CRP, serum glucose
- Throat swabs
- Pneumococcal and meningococcal serum PCR
- If there is non-blanching petechial or purpuric rash = meningococcal septicaemia
o No lumbar puncture due to risk of coning of cerebellar tonsils and raised ICA
Management of meningitis
- If suspect bacterial meningitis, start antibiotics before tests come back
- Community IM/IV benzylpenicillin, transfer to hospital
- Bacterial meningitis
o IV ceftriaxone or IV cefotaxime
o If under 3m/over 50/immunocompromised then add IV amoxicillin = Listeria
o Oral dexamethasone for 4 days = reduce cerebral oedema, hearing loss
o Consider IV vancomycin in returning travellers or penicillin resistant
o Meningitis septicaemia = IV benzylpenicillin
Prophylaxis for contacts of meningitis
o Oral ciprofloxacin state = all ages and pregnancy
o Oral rifampicin = all ages but not pregnancy
Complications of meningitis
- Hearing loss
- Seizures and epilepsy
- Cognitive impairment and learning disability
- Memory loss
- Focal neurological deficits = limb weakness and spasticity
Normal CSF fluid from LP
Clear
Protein 0.2-0.4
Glucose 0.6-0.8
WCC <5
Culture neg
Bacterial CSF fluid in LP
Cloudy
>1.5g/L
Glucose <0.5
WCC >1000 + neutrophils
Bacterial culture
Viral CSF in LP
Clear
Mildly raised/normal protein
Normal glucose
WCC >1000 + lymphocytes
Negative culture
What is encephalitis
Infection and inflammation of brain parenchyma (frontal and temporal lobes)
Causes of encephalitis
- Herpes simplex virus 1 (children)
- HSV 2 (neonates)
- Varicella zoster,
- EBV,
- Cytomegalovirus,
- HIV,
- Polio, mumps, measles, rubella
- Non-viral = Bacterial meningitis, TB, Malaria
- Autoimmune
Presentation of encephalitis
- Triad = fever, headache and altered mental status
- Altered consciousness
- Altered cognition
- Unusual behaviour
- Acute onset of focal seizures
- Myalgia, fatigue, nausea
- History = Travel, Animal bite
- Focal neurological deficit = Hemiparesis and dysphasia
- Raised ICP and midline shift may occur resulting in coning
- Coma
Investigations for encephalitis
- Lumbar puncture = CSF for viral PCR (elevated lymphocytes)
- MRI after LP
o Shows areas of inflammation and swelling, generally in temporal lobes in HSV encephalitis
o May be midline shifting due to raised ICP - CT head if LP contraindicated = GCS <9, haemodynamically unstable, active seizures, post-ictal
- Electroencephalography = Shows periodic sharp and slow wave complexes
- Throat and vesicle Swabs identify causative organism
- HIV testing
Management of encephalitis
- Immediate treatment with anti-viral before results=
o IV acyclovir = HSV, VSV
o IV ganciclovir = cytomegalovirus - Anti-seizure medication = primidone
- If meningitis suspected = Emergency IM benzylpenicillin
- Repeat lumbar puncture
- Other viral causes supportive management
Complications of encephalitis
- Lasting fatigue and prolonged recovery
- Change in personality or mood
- Changes to memory and cognition
- Learning disability
- Headaches
- Chronic pain
- Movement disorders
- Sensory disturbance
- Seizures
- Hormonal imbalance
