Infections Flashcards
What organism causes cellulitis
B-haemolytic streptococci usually group A strep (progenies)
Others include staph aureus
Describe the clinical presentation of cellulitis
infected area is painful, hot and oedematous usually with lymphangitis
What si the treatment for cellulitis
antibiotics - amoxicillin
necrotising fasciitis may require surgery
What is the curative treatment for an abscess
drainage
What organism is responsible for the tetanus infection
C. tetani bacillus (anaerobic)
Where is tetanus more often seen
tropics
How long is the incubation period of tetanus
2 days to 3 weeks
What can cause tonic and clonic muscle contracture in a tetanus infection
What muscles are often affected
a powerful neurotoxin which is produced at site of infection and then the facial and jaw muscles producing lockjaw.
Gradual muscle involvement spreads and leads to respiratory arrest
What causes gas gangrene
Anaerobic bacillus C perfringens
Where does gas gangrene occur
in wounds contaminated by soil and manure especially if necrotic tissue is present
What is often associated with wound botulism
IV drug usage where spew contaminated batches of heroin have been injected directly into tissues (skin popping)
What is the classical presentation of wound botulism
Bilateral cranial neuropathies associated with symmetrical descending weakness
absence of fever
normal heart rate
blurred vision
What is the treatment for wound botulism
Soft tissue debridement
appropriate antibiotics (metronidazole)
anti-toxin administration
Supportive care - ITU and intubation
What is acute osteomyelitis
a common condition that is usually caused by Staph progenies
Who is most commonly affected by acute osteomyelitis
children
What may predispose to acute osteomyelitis
poor living conditions
What bones are most commonly affected by acute osteomyelitis
Lower end of the femur
upper end of the tibia
either end of humerus, radius and ulna
vertebral bodies
What actually happens in acute osteomyelitis
Usually a preceding injury
confined space and tension results in tissue necrosis
abscess may form within the bone
plus breaks out under the periosteum penetrating a point on the surface of the skin
What are some of the clinical features of acute osteomyelitis
fever pain swelling tenderness oedema and pus Swelling of nearby joint due to a sympathetic effusion failure to thrive cries when limb is moved
What is the management fro acute osteomyelitis
Blood culture Broad spectrum antibiotics Surgical drainage is pus is suspected Change of antibiotics depending on the microbiology result 6 weeks of antibiotic therapy
What is a guide to the rate of recovery of acute osteomyelitis
ESR levels
How is a diagnosis of osteomyelitis of the spine sometimes made
blood culture and aspiration or drainage of pus from a paravertebral abscess
How does osteomyelitis of the spine occur
usually secondary to bacteraemic spread; common sources include skin and soft tissue infections, cannula/ line associated infections
UTI
endocarditis
RTI
How can acute suppurative arthritis occur
from progression of osteomyelitis
from haematogenous spread
in rheumatoid joints
following penetrating injuries
What joints affected by osteomyelitis are more likely to cause acute suppurative arthritis
Hip and upper end of the radius (elbow)
Describe the radiological changes in acute suppurative arthritis
may be none in the early stages
later, sub-periosteal new bone may become visible with generalised periarticular porous
How can a diagnosis of acute suppurative arthritis be made
aspiration and identification of organisms by blood culture
What is the management for acute suppurative arthritis
infected joint must be surgically washed out
What is chronic paronychia
a persistent nail-fold infection usually caused by a fungus or by repeated irritation e.g. detergents
What is the usual causative organism of chronic paronychia
Herpes simplex
How might chronic pyogenic osteomyelitis arise
After trauma to bone (open fracture, penetrating injury, bullet wounds)
Haematogenous spread
Inadequately treated acute osteomyelitis
Complication of surgery particularly when foreign material is implanted
Describe the clinical course of chronic pyogenic osteomyelitis
Flares of infection with pain and swelling and often pus alternating with periods of quiescence sometimes lasting several years
What investigations should be performed for chronic pyogenic osteomyelitis
X Rays - demonstrate the abnormal bone texture with thickening and diffuse cavity formation
Culture of the pus from a persistent sinus usually yields mixed organisms from secondary infection
What is involved in treating chronic pyogenic osteomyelitis
Acute episodes - appropriate antibiotic and surgical drainage if necessary
Eradication- long term antibiotics combined with excision of sequestra and opening up or poorly draining cavities
Open a wound widely, scrape out cavities and close the defect with muscle on a vascular pedicle or a split-skin graft
Amputation may occasionally be required
What are the prominent features of TB of bones and joints
Destruction of bone and articular cartilage by TB granulation tissues
Thickening of synovial membrane - destroys the articular cartilage
Abscess formation - in spinal tuberculosis - pus tracks along tissue planes
Fibrosis - occurs in the healing phase
What are the Xray features of TB of bones and joints
Osteoporotic changes around the joint
Erosion of the joint surfaces and loss of joint space
Destruction of bone
Soft tissue shadows representing abscesses (BIRD’S NEST SHADOW)
What are the investigations for TB of bones and joints
ESR Moderate lymphocytosis Tuberculin test may be positive Biopsy of lymph glands may show TB - biopsy of bone or synovium usually more reliable Bacilli may be cultures from sputum
What is the treatment of TB of bone and joints
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
What are the 4 reasons for formation of a sinus
congenital - persistance of an embryological structure
Foreign body - often a problem with infected prostheses
Chronic infection - TB or fungal infection may produce a chronic sinus after the abscess has discharged or been drained
Neoplasia - a sinus may communicate with a neoplastic mass
