Infectious Diseases - Common Infections Flashcards
Presentation of chest infections.
- cough
- sputum production
- shortness of breath
- fever
- lethargy
- crackles on chest
Typical causes of chest infections.
Streptococcus pneumonia (50%)
Haemophilus influenzae (20%)
Which bacterial colonisation is typical of a patient with pneumonia, who is immunocompromised?
Moraxella catarrhalis
Which bacterial colonisation is typical of a patient with pneumonia, who has COPD?
Pseudomonas aeruginosa
Which bacterial colonisation is typical of a patient with pneumonia, who has cystic fibrosis?
Pseudomonas aeruginosa or Staphylococcus aureus
Which bacterial colonisation is typical of a patient with pneumonia, who has bronchiectasis?
Haemophilus influenzae
Pseudomonas aeruginosa
What are the atypical causes of pneumonia?
Legions of psittaci MCQs:
Legionella pneumophilia
Chlamydia psittaci
Mycoplasma pneumonia
Chalmydydophila pneumonia
Q fever
Which antibiotic choice would be appropriate to commence in the community for a patient with typical pneumonia?
Amoxicillin
Erythromycin or clarithromycin if penicillin allergic.
What is infective endocarditis?
Infection of the endothelium of the heart, most commonly affecting the heart valves.
Risk factors for infective endocarditis.
- IVDU
- structural heart pathology
- CKD
- immunocompromised (e.g. HIV, cancer)
- history of infective endocarditis
Give an example of some structural pathologies that can increase the risk of infective endocarditis.
- valvular heart disease
- congenital heart disease
- hypertrophic cardiomyopathy
- prosthetic heart valves
- implantable cardiac devices
What are the causes of infective endocarditis?
Staphylococcus aureus is most common.
Presentation of infective endocarditis.
- fever
- fatigue
- night sweats
- muscle aches
- anorexia
Any pyrexia of unknown origin should prompt infective endocarditis as a differential.
Examination findings of infective endocarditis.
- new or changing heart murmur
- splinter haemorrhages
- petichiae
- Janeway lesions
- Osler’s nodes
- Roth spots
- splenomegaly
- finger clubbing
How should infective endocarditis be investigated?
3x blood culture samples BEFORE staring abx, separated by at least 6 hours and taken from different sites.
Echocardiography is usual imaging investigation.
Which criteria is used to diagnose infective endocarditis?
Modified Duke Criteria (see image)
How is infective endocarditis managed?
IV broad spectrum antibiotics (e.g. amoxicillin and gentamicin).
Surgery may be required for heart failure, large abscesses or infections not responding to abx.
What are the complications of infective endocarditis?
- heart valve damage (regurgitation)
- heart failure
- infective emboli
- glomerulonephritis
What is meningitis?
Inflammation of the meninges, which are the lining to the brain and spinal cord.
What is Meningococcal septicaemia?
Neisseria meningitidis enters the bloodstream.
It is the cause of the classic non-blanching rash, which indicates the infection has caused disseminated intravascular coagulopathy (DIC) and subcutaneous haemorrhages.
What are the most common causes of bacterial meningitis in children and adults?
Neisseria meningitidis
Streptococcus pneumoniae
What is the most common cause of bacterial meningitis in neonates?
Group B streptococcus.
Vertical infection route, contracted during birth from GBS bacteria that can often live harmlessly in the mothers vagina.
Presentation of meningitis in children and adults.
Triad of meningism:
- headache
- neck stiffness
- photophobia
Plus:
- n+v
- fever
- non-blanching rash in meningococcal septicaemia
Presentation of meningitis in neonates.
Very non-specific signs and symptoms such as hypotonia, poor feeding, lethargy, hypothermia and a bulging fontanelle.
NICE recommend lumbar puncture as part of the investigation for all children who:
- Under 1 months presenting with fever
- 1-3 months with fever and are unwell
- Under 1 years with unexplained fever and other features of serious illness
Which tests can be performed to look for meningeal irritation?
- Kernig’s test
- Brudzinski’s test
What is Kernig’s test?
Kernig’s test involves lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees.
This creates a slight stretch in the meninges and where there is meningitis will produce spinal pain or resistance to this movement.
What is Brudzinski’s test?
Brudzinski’s test involves lying the patient flat on their back and gently using your hands to lift their head and neck off the bed and flex their chin to their chest.
A positive test is when this causes the patient to involuntarily flex their hips and knees.
Investigation of meningitis.
- blood culture
- lumbar puncture for CSF
Send blood tests for meningococcal PCR.
Management of meningitis.
Have a low threshold for treating suspected bacterial meningitis.
UHL (2023) Ceftriaxone IV 2g BDS
AND
Dexamethasone 10mg QDS*
*Steroids reduce the frequency and severity of hearing loss and neurological damage.
Outline the post-exposure prophylaxis of meningitis.
Meningitis is a notifiable disease, therefore post exposure prophylaxis is guided by public health.
Any close contacts within the last 7 days prior to the onset of illness will receive a single dose of ciprofloxacin.
What are the most common causes of viral meningitis?
Herpes simplex virus (HSV)
Enterovirus
Varicella zoster virus (VZV)
What are the characteristics of CSF with bacterial inoculation?
Appearance:
Protein:
Glucose:
White cell count:
Culture:
Appearance: Cloudy
Protein: High
Glucose: Low
White cell count: Neutrophilia
Culture: Bacteria
What are the characteristics of CSF with viral inoculation?
Appearance:
Protein:
Glucose:
White cell count:
Culture:
Appearance: Clear
Protein: Normal
Glucose: Normal
White cell count: Lymphocytosis
Culture:Negative
What are the common complications of meningitis?
- hearing loss
- seizures
- cognitive impairment
- memory loss
- focal neurological deficits
What is acute gastritis?
Inflammation of the stomach, presenting with nausea and vomiting.
What is enteritis?
Inflammation of the intestines, presenting with diarrhoea.
What is gastroenteritis?
Inflammation of the stomach and intestines, presenting with nausea, vomiting and diarrhoea.
What is the most common cause of gastroenteritis?
Viral gastroenteritis is the most common and highly contagious:
- rotavirus
- norovirus
- adenovirus
Which organism can cause haemolytic uremic syndrome as a complication of gastroenteritis?
Escherichia coli.
E. coli 0157 produces the Shiga toxin, which causes abdominal cramps, bloody diarrhoea and vomiting.
The Shiga toxin also destroys blood cells, leading to haemolytic uraemic syndrome.
Abx increase the risk of HUS, so should be avoided if E. coli gastroenteritis is considered.
What is the most common cause of travellers diarrhoea?
E. coli
THEN
Campylobacter jejuni, causing abdominal cramps, bloody diarrhoea, vomiting and fever.
What is the typical course of Bacillus cereus gastroenteritis?
Whilst growing on the food it produces a toxin called cereulide that causes abdominal cramping and vomiting within 5 hours of ingestion. When it arrives in the intestines it produces different toxins that cause a watery diarrhoea. This occurs more than 8 hours after ingestion. All of the symptoms usually resolves within 24 hours.
Therefore the typical course is vomiting within 5 hours, then diarrhoea after 8 hours, then resolution within 24 hours.
How should gastroenteritis be managed?
- stool culture
- fluid challenge
- dioralyte or IV fluids to rehydrate
- slowly introduce light diet
Presentation of cystitis.
- dysuria
- suprapubic pain / discomfort
- frequency
- urgency
- incontinence
- confusion
Presentation of pyelonephritis.
- fever
- loin, suprapubic or back pain
- vomiting
- loss of appetite
- haematuria
- renal angle tenderness on examination
How are UTIs initially investigated?
Urine dipstick.
Nitrites are a breakdown product that bacteria produce.
Leukocytes are present in urine due to inflammation.
Nitrates + Leukocytes = UTI
Nitrates + no leukocytes = UTI
Leukocytes + no nitrates = no UTI
What is the most common cause of UTI?
Escherichia coli
Outline the abx therapy for UTIs.
Nitrofurantoin or Trimethoprim.
3/7 for simple LUTI in women.
5-10/7 for women that are immunosuppressed, have abnormal anatomy or impaired kidney function.
7/7 for men, pregnancy women or catheter related UTI.
What are the risks of UTIs in pregnancy?
Increases the risk of
- pyelonephritis
- premature rupture of membranes
- pre-term labour
How should pyelonephritis be managed?
10 day course of abx in the community:
- cefalexin
- co-amoxiclav
- trimethoprim
- ciprofloxacin
Referral to hospital if there are features of sepsis.
What is cellulitis?
Infection and subsequent inflammation of the skin and soft tissues underneath, due to a breach in the skin barrier.
This may be due to skin trauma, eczematous skin, fungal nail infections or ulcers.
Presentation of cellulitis.
- erythema
- calor
- tense
- oedematous
- bullae (fluid filled blisters)
- golden-yellow crust indicates Staphylococcus aureus infection
What are the common causes of cellulitis?
- Staphyloccus aureus
- Streptococcus pyogenes
- Streptococcus dysgalactiae
- MRSA
NICE recommend which classification to assess the severity of cellulitis?
How is cellulitis managed?
Flucloxacillin first line in Staphylococcus aureus, and has good gram +ve coverage.
Presentation of septic arthritis.
- hot, red and swollen joint
- stiffness and reduced ROM
- systemic symptoms (e.g. fever, lethargy, sepsis)
What is the most common causative organism of septic arthritis?
Staphylococcus aureus
Other causes include Neisseria gonorrhoea, Haemophilus influenza and Escherichia coli.
Give some differentials for septic arthritis.
- gout
- pseudogout
- reactive arthritis
- haemarthrosis
Management of septic arthritis.
- aspirate joint and send for gram staining, crystal microscopy, culture and antibiotic sensitivities
- blood culture
- empirical IV antibiotics
What is osteomyelitis?
Inflammation in bone and bone marrow, usually caused by bacterial infection.
What is the most common cause of osteomyelitis?
Staphylococcus aureus
What are the risk factors for developing osteomyelitis?
- open fractures
- orthopaedic operations
- diabetes
- peripheral arterial disease
- IVDU
- immunosuppression
Presentation of osteomyelitis.
- fever
- pain and tenderness
- erythema
- swelling
Investigations for osteomyelitis.
- x-ray
- MRI scan (GOLD STANDARD)
- FBC showing raised inflammatory markers
- blood culture for causative organism
- bone culture
What are the potential signs of osteomyelitis on x-ray?
- periosteal reaction
- localised osteopenia
- destruction of the bone
Management of osteomyelitis.
- surgical debridement of infected bone and tissue
- antibiotic therapy
