STAPHYLOCOCCI Pathogenesis, Clinical Syndromes

PATHOGENESIS:
  • Adhere to damaged skin, mucosa or tissue surfaces
  1. At these sites, they evade defence mechanisms of the host, colonize and cause tissue damage
  • S.aureus produces disease by
  1. Multiplying in tissues
  2. Liberating toxins,
  3. Stimulating inflammation
CLINICAL SYNDROMES:
  • Conjuctivitis
  • Cutaneous infections
  1. Folliculitis
  2. Boils/furuncles
  3. Carbuncle
  4. Impetigo/Ecthyma
  5. Wound infections
  6. botryomycosis 
  • Deep infections
  1. Osteomyelitis 
  2. Periostitis
  3. endocarditis
  4. Botryomycosis
  5. Septic arthritis( in children)
  6. Pneumonia( In patient with bronchiectasis)
  • Exfoliative diseases
  • Sore throat 
  • Pneumatocoele 
  • Toxin shock syndrome
  • Staphylococcal food intoxication
CUTANEOUS INFECTIONS:
  • Folliculitis: 
  1. It is inflammation of the hair follicles
  2. A small red bump or pimple develops at infection sites of hair follicle.
  • Sty: 
  1. A sty is folliculitis affecting one or more hair follicles on the edge of the upper or lower eyelid.
  • Furuncle/boils:
  1. Furuncle is deep seated infection, originating from folliculitis,( if infection extends from follicle to neighbour tissue)
  2. Causes redness, swelling, severe pain
  3. Commonly found on the neck, armpit and groin regions
  • Carbuncle:
  1. Carbuncle is an aggregation of infected furuncles. Carbuncles may form large abscesses.
  2. It is a large area of redness, swelling and pain, punctuated by several sites of drainage pus.
  • Bullous Impetigo:
  1. Very superficial skin infection common in children, usually produces blisters or sores on the face, neck, hands, and diaper area.
  2. It is characterized by watery bristles, which become pustules and then honey coloured crust
  • Botryomycosis:
  1. Cutaneous infection classically occurs on the extremities in areas of trauma and in immunocompromised individuals.
  • Staphylococcal pneumonia
  1. URTI , pyoderma or other associated purluent disease
  2. Besides the usual features of pneumonia child has fever and anorexia and is listless and irritable.
  3. Abdomen is usually distended due to septicemia and ileus.
  4. Cyanosis may be present
  5. Most common pathogen causing, pulmonary infection in cystic fibrosis in infants & young children is Staphylococcus aureus
  6. Chest radiograph shows patchy areas of consolidation and multiple bilateral thin walled air containing cysts
DEEP INFECTIONS:
  • Osteomyelitis:
  1. Both acute & chronic osteomyelitis is caused by S.aureus
  2. Bacteria can get to the bone Via bloodstreamFollowing an injury
  3. Clinical features: pain, swelling, deformity, defective healing, in some case pus flow,
  4. Diagnosis: X-ray, MRI, bone aspirates
  • Periostitis:
  1. Clinical features: fever, localised pain, leucocytosis
  2. Diagnosis: needle aspiration of subperiosteal fluid
  • Endocarditis: 
  1. It is an inflammation of the inner layer of the heart, the endocardium
  2. Prosthtetic valve, tooth extraction may be the aggrevating factor in Infective endocarditis by s. aureus
  3. Endocarditis occurs when bacteria enter bloodstream, travel to heart, and lodge on abnormal heart valves(Prosthetic valve endocarditis ) or damaged heart tissue. 
  4. Myocardial abscess is most common in acute endocarditis caused by Staphylococcus aureus
Exfoliative diseases:
  • Also known as ‘Staphylococcal skin scalded syndrome’previously called dermatitis exfoliativa, pemphigus neonatorum, Lyell’s disease and Ritter’s disease
  • Epidermal toxin produced by S.aureus at skin and is carried by bloodstream to epidermis , where it causes a split in a cellular layer i.e., this toxin separates outer layer of epidermis from underlying tissue
TOXIC SHOCK SYNDROME:
  • Caused when Toxin shock syndrome toxin (TSST) liberated by S.aureus enters bloodstream
  • It is a multisystem illness, that occurs due to superantigen& is characterized by:
  1. High Fever
  2. Headache
  3. Conjunctival reddening
  4. Hypotension
  5. Vomiting
  6. Diarrhoea
  7. Skin rashes
  8. Kidney failure
STAPHYLOCOCCUS FOOD POISIONIG:
  • Caused when consuming food in which S.aureus has multiplied and pre-formed endotoxin i.e., intradietic toxin is responsible for intestinal symptoms.
  • Commonly occurs with dairy products
  • Optimum temperature for toxin production is 37°C
  • Incubation period is 1-6 hours
  • Gastroenteritis within 4-6 hrs of consumption of cooked food indicates the cook to be in the carrier state of staphylococcus
  • Staphylococcus appear in stool 
  • Symptoms:
  1. Nausea
  2. Vomiting
  3. Severe abdominal cramp
  4. Diarrhoea
  5. Sweating
  6. Headache,etc.
STAPHYLOCOCCUS SAPROPHYTICUS :
  • Staphylococcus saprophyticus is a coagulase— negative organism that causes 0%-20% of acute urinary tract infections in young, sexually active females & acute cystitis
  • It is resistant to the antibiotic novobiocin. Trimethoprim and sulfamethoxazole is the treatment of choice.
Exam Question
  • Staphylococcus saprophyticus causes acute cystitis
  • Staphylococcus aureus causes pneumonia in a patient with bronchiectasis
  • Staphylococcus aureus causes Prosthetic valve endocarditis 
  • Ecthyma & Furuncle are caused by Staphylococcus aureus
  • Staphylococcus aureus is implicated in the causation of botryomycosis 
  • Toxic shock syndrome is caused by Staphylococcus aureus
  • Staphylococcus in stool occurs in Staphylococcal food poisoning
  • Staphylococcus saprophyticus is gram positive organism that is most common cause of UTI among sexually active women
  • Toxic shock syndrome is Staphylococcus infection is due to Superantigen
  • Gastroenteritis within 4-6 hrs of consumption of cooked food indicates the cook to be in the carrier state of staphylococcus 
  • Myocardial abscess is most common in acute endocarditis caused by Staphylococcus aureus
  • Pyoderma with respiratory distress showing patchy areas of consolidation and multiple bilateral thin walled air containing cysts in chest xray is suggestive of pneumonia caused by Staphylococcus aureus
  • Septic arthritis in a 2 year old child is often caused by Staphylococcus aureus
  • Most common pathogen causing, pulmonary infection in cystic fibrosis in infants & young children is Staphylococcus aureus
  • Most common bacteria associated with conjunctivitis is Staphylococcus aureus
  • Causative agent of sore throat is Staphylococcus aureus
  • Pneumatocoele is most commonly caused by Staphylococcus aureus
  • Staphylococcus food poisioning Commonly occurs with dairy products
  • Bullous impetigo is caused by Staphylococcus aureus
  • Staphylococcus aureus is responsible for vesicular eruptions and honey-coloured crusts over face Infective endocarditis after tooth extraction is probably due to Staphylococcus aureus
  • Both acute & chronic osteomyelitis is caused by S.aureus
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