Pathology of Infections II Flashcards
describe staphylococci
- G+ve positive cocci in clumps
- normally colonize human skin
- 3 common species:
- S. aureus, S. epidermidis, S. saprophyticus
- can produce 2 types of lesion:
- inflammatory
- toxin-mediated
most infections of the staphylococci species are caused by ___
most infections of the staphylococci species are caused by S. aureus
describe inflammatory lesions of staphylococci
- skin:
- folliculitis, furuncle, carbuncle, cellulitis, impetigo, abscess paronychia and surgical wound infection
- postpartum mastitis
- bacteremia
- endocarditis:
- tricuspid valve: common in IV addicts
- osteomyelitis
- organisms reach bone hematogenously or directly from adjacent abscesses or through traumatic implantation
- pneumonia:
- bronchopneumonia, abscess, empyema
- bacteremia abscesses: lung, kidney, brain
- 80% penicillin resistant (MRSA)
describe impetigo and risk factors for it
superficial skin infection, highly contagious
- risk factors: crowding, DM, poor nutrition
describe etiology of impetigo
- etiology:
- Staph aureus
- Streptococcus pyogenes
describe clinical features of impetigo
- clinical features:
- rash usually begins on face
- vesicles and pustules rupture to form honey-colored crusted lesions
describe complications of impetigo
- cellulitis, septicemia, scarlet fever (rare)
describe a furuncle, and risk factors and diagnosis of it
- skin abscess
- common on neck, face, buttocks and armpit
- involve hair follicle and surrounding tissue
- risk factors: diabetes, obesity, immunocompromised, crowding with poor hygiene
- diagnosis: clinical, swab for culture and sensitivity
describe what is seen in the image
describe what is seen in the image
describe what is seen in the image
describe lung abscesses and risk factors and clinical features
localized area of superficial necrosis within the lung
- risk factor: aspiration of gastric contents, bronchial obstruction, endocarditis, dental extraction
- clinical features: cough productive of foul-smelling sputum, fever and finger clubbing
describe a chest x-ray of lung abscesses
- intrapulmonary cavity with irregular air-fluid level
describe what is seen in the image
describe what is seen in the image
describe the toxin-mediated lesions of staphylococci
describe the pathogenesis of toxic shock syndrome
- associated with the use of intra-vaginal tampon and other risk factors (skin wound, recent surgery)
- if left longer, leads to growth of Staph → release of exotoxin (super antigen) → stimulate polyclonal T cell activation which induces T cells to release high levels of cyotkines → diffuse rash, vasodilation, hypotension and death
describe clinical features and diagnosis of toxic shock syndrome
- clinical features: fever, hypotension, vomiting, diarrhea, skin erythema, confusion, rash resembling a sunburn especially on palms and soles
- diagnosis: blood culture, cervical swabs
describe streptococci
- G+ve cocci
- present in pairs or chains
- species: S. pyogenes, S. pneumoniae, S. agalactiae viridans group and enterococcus
- produce hemolysis
_____ is the most important human pathogen (streptococci)
Group A beta hemolytic is the most important human pathogen (streptococci)
describe direct, exotoxin and indirect damage by streptococci
- direct damage:
- suppurative - cellulitis, abscess, pneumonia
- exotoxin mediated
- Scarlet fever
- indirect damage by immune responses
- Rheumatic heart disease/glomerulonephritis
describe streptococcus pneumonia (aka pneumococcal pneumonia) and risk factors, clinical features and investigations of it
- causes lobar pneumonia
- G+ve lancet-shaped diplococci, most common cause of community-acquired pneumonia
- healthy young adults
- risk factors: diabetes, CHF, COPD, absent spleen
- clinical features: fever, productive cough, chest pain, bloody sputum, dullness to percussion (consolidation), bronchial breath sounds, late inspiratory crackles
- investigations: CXR (gold standard), blood/sputum culture, neutrophilic leukocytosis
describe the pathology of streptococci pneumonia
- bronchioles and alveolar walls are not damaged
- spreads through the pores of Kohn to involve the entire lobe
- it passes through different stages:
- congestion: exudates rich in fibrin, RBC, a few PMN
-
red hepatization: exudates consist of RBCs, fibrin, more PMNs
- lung loses its spongy consistency, feels solid and red like a liver
- grey hepatization: congestion and fibrin disappear, PMNs replaced by macrophages
- resolution: macrophages clear up the debris a few days later
