Lecture 11- Streptococci Flashcards
How are streptococci classified?
By haemolysis
Alpha haemolysis?
Viridans streptococci
Partial haemolysis
Streptococcus pneumoniae
Beta haemolysis?
Streptococcus pyogenes
Com9lete haemolysis
Gamma haemolysis?
Non haemolytic
Enterococcus faecalis
Staph vs strep?
Staph is like grapes while strep is in chains
Streptococci pos or neg
Gram positive (positively purple)
Gram neg would be red
Streptococci classification schemes?
Lance filed, Sherman and dna sequencing analysis
Streptococcus pyogenes?
Beta haemolytic lanefield group a often causing pharyngitis and tonsillitis
What is a virulence factor?
Molecules produced by a bacteria that help it to colonise
Streptococcal pharyngitis?
Caused by strep pyogenes.
Peak incidence 5-15 years
Droplet spread
Almost always resolves by itself antibiotics only slightly reduce course and prevent antibodies from developing
Clinical features include fever, malaise, sore throat, lymphoid hyperplasia
What is scarlet fever?
Complication of streptococcal pharyngitis if infected with certain strain. Causes high fever, arthritis, jaundice and sepsis
Supppation?
Pus forming
Suppurative complications of pharyngitis?
Pus can move down to the lateral pharyngeal space and enter carotid artery and move to brain etc.
Peritonsillar cellulitis and retropharyngeal abscess
Pharyngitis and acute rheumatic fever?
Antibodies produced against infection work against body’s own antigens.
Causes inflammation of joints, heart and CNS
Pharyngitis and acuute post streptococcal glomerulonephritis?
Antibodies attack antigens in glomerulus leads to inflammation
Strep pyogenes skin infections?
Impetigo
Erysipelas
Cellulitis
Necrotising fasciitis
Cellulitis?
Can be caused by staph aureus or strep pyogenes. Infection of skin and subcutaneous tissue. Risk factors include IV drug use and impaired lymphatic drainage.
Treat with flucloxacillin whether the cause be aureus or pyogenes.
Necrotising fasciitis?
Infection of deeper subcutaneous tissues and fascia.
Get rapid and extensive necrosis. Make incision and insert finger, if easy to move then necrotic tissue present and surgical debridement required. Causes high fever and high mortality with sudden onset
What is streptococcal toxic shock syndrome?
Deep tissue infection with strep pyogenes that enters blood and causes organ failure. In 80’s tampons left in long time and caused it
