Flashcards in Infection Deck (82)
What is an abscess?
A collection of pus walled off by an area of inflammation
What is the aetiology of an abscess?
- Pyogenic abscesses are caused by infection that the body's defences have failed to completely overcome
- Common bacteria include S. aureus, streptococci, enteric organisms, other coliforms and anaerobes.
- TB classically causes 'cold' abscesses
What are the risk factors for abscesses?
- Local: tissue necrosis, a closed underperfused space of foreign body that provides a focus for infection e.g. tooth or root fragment, splinters, mesh of hernia repairs, embedded hair, malignancy
- Systemic: Diabetes, immunosuppression
What is the epidemiology of abscesses?
Common in all ages
What are the presenting symptoms of abscesses?
- Pt may complain of local effects of pain, swelling, heat, redness and impaired function of the area where abscess is present
- And/or systemic effects such as fever and feeling unwell
What are the signs of abscesses on examination?
- Local effects as presenting symptoms
- If present within organ, localising signs may be absent, only sign being swinging pyrexia
What are the investigations for abscesses?
- Bloods: FBC, increased neutrophils
- Imaging: Ultrasound, CT, MRI scanning may be used to search for site
- Aspiration: Pus is low in glucose and acidic. Culture of pus for organisms and sensitivity to organisms
How are abscesses prevented?
Prophylactic antibiotics (e.g. during operations) or if given early during an infection. Often not effective once abscess has formed
How are abscesses managed by surgery?
Drainage of pus is carried out by incision and drainage, with debridement of cavity and subsequent free drainage by packing of cavity (if superficial) or by drains (if deep)
How are abscesses generally managed?
Principles involved include drainage of pus, removal of necrotic and foreign material, antimicrobial cover and correction of the predisposing cause
What are the possible complications of abscesses?
- Spread may result in cellulitis (in skin) or bacteraemia with systemic sepsis
- If focus of infection is not removed, a chronic abscess or discharging sinus or fistula may form.
- Occasionally, antibiotics may penetrate and result in the formation of a sterile collection or antibioma
- If constrained by strong facial planes, slow expansion can cause pressure necrosis of surrounding tissues
What is the prognosis for abscesses?
- Good, if adequately drained and predisposing factor removed
- If left untreated, abscesses tend to 'point' to the nearest epithelial surface and may spontaneously discharge their contents
- Deep abscesses may become chronic, undergoing dystrophic calcification
What is oral candidiasis?
- Infection of oral tissues
- Can also cause oropharyngeal, oesophagitis, vulvovaginits, endopthalmitis, meningitis, endocarditis
What is candidaemia?
- Infection of blood, pleural, peritoneal fluid with Candida
- Usually fever, hypotension, leukocytosis
- Disseminates to retina, kidney, liver, spleen, bones, CNS
What is the epidemiology of candidiasis?
- Oral: Infants, older adults, immune suppression
- Candidaemia: Pts in hospital, intravascular catheters, neutropenia
What are the causes and risk factors of candidiasis?
C. Albicans is most common infection
- Oral candidiasis: HIV infection, Xerostomia, dentures, malnutrition, advanced malignancy, cancer chemo or radiotherapy, pregnancy, diabetes, immunosuppressive therapy
- Candidaemia: Central venous catheter, use of broad spectrum abx, haemodialysis, surgery, parenteral nutrition, immunosuppressants
What are the presenting symptoms of candidiasis?
- Fever due to sepsis
- Hoarse voice
- Genital candidiasis: vulval pruritis, burning, swelling, dyspareunia
What are the signs of oral candidiasis on examination?
- Creamy white or yellowing plaques
- Adheres to oral mucosa
- Removal of plaque may show erythamatous base of bleeding surface
- Cracks, ulcers, crusted fissures from angles of mouth
- Lesion anywhere on oral mucosa
- Immunodeficiency: patchy loss of filiform papillar, spotty red areas on buccal mucosa
- Lesion confined to outline of dental prosthesis
- Burning oral pain
What are the signs of candidaemia on examination?
- Poor capillary refill
- Acute mental confusion
- Decresed urine output
- Low 02 sats
What are the investigations for candidiasis?
- Oral: Superficial smear of lesion for microscopy, biopsy of lesion, culture of mouth rinse sample
- Candidaemia: Blood cultures, ABG (hypoxaemia, hypercapnia), high lactate, creatinine, high LFTs
What is cellulitis?
Acute non-purulent spreading infection of the subcutaneous tissue, causing overlying skin inflammation
What is the aetiology of cellulitis?
- Often results from penetrating injury (e.g. intravenous cannulation), local lesions (e.g. insect bites, sebaceous cysts, surgery) or fissuring (e.g. in anal fissures, toe web spaces), which allows pathogenic bacteria to enter the skin.
- Most common organisms: S. pyogenes and S.aureus.
- If occurring in the orbit: H. influenzae is most common cause
What is the epidemiology of cellulitis?
- Very common
- Main risk factors are skin break, poor hygiene and poor vascularisation of tissue (e.g. diabetes mellitus)
What are the presenting symptoms of cellulitis?
There may be a history of a cute, scratch or injury
- Periorbital: Painful swollen red skin around eye
- Orbital cellulitis: Painful or limited eye movements, visual impairment
What are the signs of cellulitis on examination?
- Lesion: Erythema, oedema, warm tender indistinct margins. Pyrexia may signify systemic spread
- Exclude abscess: Test for fluid thrill or fluctuation. Aspirate if pus suspected.
- Periorbital: Swollen eyelids. Conjuctival injection
- Orbital cellulitis: Proptosis, impaired acuity and eye movement. Test for relative afferent pupillary defect, visual acuity and colour vision (to monitor optic nerve function)
What are the investigations for cellulitis?
- Blood: WCC, blood culture
- Discharge: Culture and sensitivity
- Aspiration: As it is often non-purulent, it is not usually necessary
- CT/MRI scan: When orbital cellulitis is suspected (to assess posterior spread of infection)
How is cellulitis managed?
- Medical: oral penicillins (e.g. flucloxacillin, benzylpenicillin, coamoxiclav) or tetracyclines are effective in most community acquired cases. In hosp, treat as per microbiological guidelines
- Surgical: Orbital decompression may be necessary in orbital cellulitis. It is an emergency
- Abscess: can be aspirated, incised and drained or excised completely
What are the possible complications of cellulitis?
- Sloughing of overlying skin
- Localised tissue damage
- In orbital cellulitis, may be permanent vision loss and spread to brain, abscess formation, meningitis, cavernous sinus thrombosis
What is the prognosis for cellulitis?
Good with treatment