Infection Flashcards
Cellulitis
Cause, sx, classification, ix, mx
The most common offending organisms are Streptococcus pyogenes or Group A beta-haemolytic streptococci, followed by Staphylococcus aureus.
Sx:
- erythema
- calor
- swelling
- pain
- fever
- lymphadenopathy
Eron classification:
- Class I — there are no signs of systemic toxicity and the person has no uncontrolled comorbidities.
- Class II — the person is either systemically unwell or systemically well but with a comorbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection.
- Class III — the person has significant systemic upset, such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable comorbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize.
- Class IV — the person has sepsis or a severe life-threatening infection, such as necrotizing fasciitis.
Ix:
- wound swab
- US to distinguishing nonpurulent cellulitis from cellulitis with underlying abscess and for identifying drainable fluid collection
Mx:
- Class I - high-dose oral flucloxacillin (clarithromycin/doxycyline if penicillin allergic and erythomycin if pregnant)
- Class II - admit systemically unwell patients or those systemically well but with a comorbidity. May be able to ambulate with IV antibiotics.
- Class III-IV - admit for IV antibiotics
Hospital acquired infections
Causes, mx
Cause:
- Meticillin-resistant Staphylococcus aureus
- Meticillin-sensitive Staphylococcus aureus
- PVL - Staphylococcus aureus
- Clostridium difficile
- Escherichia coli
- Pseudomonas - common cause of hospital acquired pneumonia
Mx:
- pneumonia= co-amoxiclav. piperacillin with tazobactam, cephalosporins or meropenem for severe. Add add a glycopeptide like vancomycin or teicoplaninif MRSA
- catheter associated UTI= 7 day course of nitrofurantoin or trimethoprim (for lower UTI’s) or cefalexin (for upper UTI’s)
- indwelling line sepsis= vancomycin, with or without a broad-spectrum beta-lactam
- undifferentiated hospital-acquired septicaemia= broad-spectrum beta-lactam antibiotic with pseudomonas cover. Examples include piperacillin with tazobactam, ceftazidime or meropenem. Vancomycin or metronidazole may be needed for MRSA or anaerobic cover respectively
Hypercalcaemia of malignancy
Def, classification, cause, sx, ix, mx
Elevated adjusted calcium levels (>2.6mmol/L) due to a known or suspected cancer
Classification:
- Mild hypercalcaemia is defined as a calcium level of 2.6-3.0mmol/l with minimal symptoms.
- Moderate hypercalcaemia may be symptomatic with a calcium level of 3.0-3.5mmol/l.
- Severe hypercalcaemia is defined as calcium levels greater than 3.5mmol/l and/or the presence of severe symptoms.
Causes:
- Tumour secretion of parathyroid hormone-related peptide (PTHrP), associated with squamous cell lung cancer, renal, ovarian, breast and endometrial cell cancers.
- Bone metastases promoting osteolysis and calcium release, associated with breast cancer and multiple myeloma.
- Autonomous vitamin D production by lymphoma cells
Sx:
- Bone pain & fractures
- Altered mental status, confusion & lethargy
- Mood disturbance
- Nausea & vomiting
- Constipation
- Renal colic
- Polyuria, polydipsia & dehydration
- Shortened QT interval
- Hypertension
Ix:
- ECG showing short QT interval
- calcium, vit D and PTH (low) levels
- bone profile
Mx:
- rehydration as first priority with IV saline
- review meds and stop any that raise ca if possible (thiazide diuretics)
- IV bisphosphonates or denosumab if confirmed malignancy
- corticosteroids if vitamin D-mediated hypercalcaemia of malignancy
Malaria
Cause, sx, ix, mx
Caused by protozoan parasites of the Plasmodium genus. The different malaria species are:
- P. falciparum (the most pathogenic species)
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
Sx:
- fever
- headache
- aches and pains
- splenomegaly
- jaundice
- hypotension
- pallor
- reduced urine output
Severe:
- abnormal behaviour
- altered consciousness
- parasitaemia
- temp >39
- acute respiratory distress syndrome
- renal impairment
Ix:
- thick (parasite presence) and thin (species) blood films are the gold-standard
- ABG for severe
- blood culture
- stool culture
- CXR
- lumbar puncture
Mx:
- Uncomplicated falciparum: artemisinin-based combination (Artemether with lumefantrine) therapy
- Uncomplicated non-falciparum: artemisinin-combination therapy or chloroquine
- Severe falciparum: IV artesunate
Metastatic disease
Sx, ix, mx
Sx:
- Metastasis to the bones can cause pain and fractures
- Metastasis to the brain can result in headaches, seizures, or neurological deficits
- Metastasis to the lungs may lead to cough, shortness of breath, or chest pain
Ix:
- CT, MRI, PET and bone scans
- biopsy
Mx:
- surgery
- radiation
- chemo
- targeted therapy
- palliative care
Notifiable diseases
Def, causes
legally required to report to the UK Health Security Agency (UKHSA)
Notifiable diseases:
- Acute encephalitis
- Acute infectious hepatitis
- Acute meningitis
- Acute poliomyelitis
- Anthrax
- Botulism
- Brucellosis
- Cholera
- COVID-19
- Diphtheria
- Enteric fever
- Food poisoning
- Haemolytic uraemic syndrome
- Dysentery
- Invasive group A streptococcal disease
- Legionnaire’s disease
- Leprosy
- Malaria
- Measles
- Meningococcal septicemia
- Monkeypox
- Mumps
- Plague
- Rabies
- Rubella
- Severe acute respiratory distress syndrome
- Scarlet fever
- Smallpox
- Tetanus
- Tuberculosis
- Typhus
- Viral haemorrhagic fever
- Whooping cough
- Yellow fever
Sepsis
Cause, sx, ix, mx
The commonest sources of infection are respiratory, genitourinary, renal and gastrointestinal. Most causative pathogens are bacteria, although fungal, parasitic and viral infections can also lead to sepsis. The commonest organisms identified are Staphylococcus aureus, Escherichia coli and Pseudomonas species
Sx:
- rash
- decreased urine output
- confusion
- breathlessness
- nausea and vomiting
- tachycardia
- hypotension
- pyrexia or hypothermia
- resp distress
- delayed cap refill
Ix:
- blood culture
- lactate
- urine output
- CXR
Mx:
- IV fluid resuscitation (usually a 500ml bolus over 15 minutes initially)
- O2
- Broad-spectrum IV antibiotics
Metabolic alkalosis
Def, cause, sx, ix, mx
A metabolic alkalosis refers to a state where the blood pH is reduced with a high bicarbonate.
Cause:
- Loss of acid (H+) via the kidneys eg. Conn’s syndrome, Cushing’s syndrome, Loop and thiazide diuretics, Bartter’s and Gitelmann’s syndromes
- Loss of acid (H+) via the gastrointestinal tract usually due to vomiting
- Hypokalaemia (acts via multiple mechanisms including shifting hydrogen ions intracellularly)
- Excessive bicarbonate
- Compensation for chronic respiratory acidosis
Sx:
- Vomiting
- Confusion
- Reduced levels of consciousness
- Paraesthesias or numbness
- Weakness
- Palpitations
- Muscle twitching
- Tremor
Ix:
- ABG showing high pH, high/normal PaCO2 and high HCO3. PaCO2 would be high due to respiratory compensation
- CT abdo and pelvis if excessive vomiting
Mx:
- treat underlying cause
Metabolic acidosis
Def, classification, cause, sx, ix, mx
A metabolic acidosis refers to a state where the blood pH is less than 7.35 (i.e. an acidosis) with a low bicarbonate (less than 22 mmol/L). Metabolic acidosis can be compensated for by hyperventilation (also known as Kussmaul’s respiration, i.e. deep and laboured breathing) to excrete more carbon dioxide.
Classification:
- Anion Gap = (Sodium + Potassium) - (Bicarbonate + Chloride)
- Normal anion gap metabolic acidoses are caused by bicarbonate loss, and high anion gap metabolic acidoses are caused by accumulation of organic acids or reduced excretion of hydrogen ions.
Cause:
- raised anion gap = lactic acidosis, DKA, renal failure, aspirin poisoning, rhabdomyolysis, starvation
- normal anion gap = type 1 and 2 renal tubular acidosis, diarrhoea, adrenal insufficiency, spironolactone, pyloric stenosis
Sx:
- nausea
- vomiting
- anorexia
Ix:
- ABG showing low pH, low/normal PaCO2 and low HCO3. PaCO2 may also be low due to respiratory compensation
Mx:
- treat underlying cause
