Gram Positive Cocci - Staphylococci 2023 PDF

Gram Positive Cocci- Staphylococci Hiba J. A. Barqawi 2023 College of Medicine University of Sharjah United Arab Emirates  Which GPC would be most likely responsible for the following conditions? A. Staphylococcus aureus B. Staphylococcus epidermidis C....

Gram Positive Cocci- Staphylococci Hiba J. A. Barqawi 2023 College of Medicine University of Sharjah United Arab Emirates  Which GPC would be most likely responsible for the following conditions? A. Staphylococcus aureus B. Staphylococcus epidermidis C. Staphylococcus saprophyticus D. Streptococcus pyogenes E. Streptococcus agalactiae F. Streptococcus pneumoniae G. Viridans Streptococci H. Enterococcus faecalis I. Enterococcus faecium 1. Pharyngitis in young adult 2. Scalded Skin Syndrome in neonate 3. Neonatal meningitis 4. Septicaemia in a hospitalized patient in the ICU 5. Toxic Shock Syndrome in 30- year-old female 6. Urinary tract infection in a 25-year-old female 7. Dental caries 8. Pneumonia in 32-year-old male 9. Impetigo in 4-year-old child 10. Necrotizing fasciitis 11. Endocarditis in patient with artificial heart valve 12. Urinary tract infection in a hospitalized patient in the ICU 13. Cellulitis Optochin sensitive Optochin resistant  Gram Positive Cocci Staphylococci – S. aureus – S. epidermidis – S. saprophyticus Streptococci – S. pyogenes (Group A) – S. agalactiae (Group B) – S. pneumoniae – Viridans Streptococci Enterococci – Enterococcus faecalis – Enterococcus faecium Staphylococci  Staphylococci Gram-positive Non-motile Non-spore forming Cocci Facultative anaerobes Form grape clusters or clumps β- haemolytic Catalase-positive (Distinguish between Staphylococci and Streptococci by catalase activity)  Human Pathogens Staphylococcus aureus – Broad spectrum of clinical syndromes Staphylococcus epidermidis – Medical device related infections Staphylococcus saprophyticus – Urinary tract infections  Staphylococcus species Staphylococcus aureus – Strains are coagulase positive – Golden pigmentation of colonies grown on rich media – β- hemolytic Staphylococcus epidermidis – Strains are coagulase negative – White pigmentation of colonies – Medical device related infections Staphylococcus saprophyticus S. aureus S. epidermidis – Strains are coagulase negative – Colonies can be white or golden depending on strain – Responsible for 20% of UTIs  Staphylococci: normal human flora Normal flora on human skin and mucosal surfaces Organisms can survive on dry surfaces for long periods Due to thickened peptidoglycan layer and absence of outer membrane Person-to-person spread through direct contact or exposure to contaminated fomites (e.g. bedlinen, clothing... etc) S. aureus is a common inhabitant of anterior nares. It can also be found in other areas of the body (skin, mucosa... etc) – Transmission: hands, sneezing, surgical wounds, contaminated food (custard pastries, potato salad, canned meats) S. epidermidis is a common inhabitant of skin Staphylococci can be seen as opportunistic pathogens – S. aureus and S. epidermidis are leading causes of nosocomial-acquired bacteraemia and sepsis Risk factors: – Presence of a foreign body e.g. splinter, prosthesis, catheter, tampon – Wound or previous surgical procedure – Intravenous drug abuse – Cystic fibrosis – Use of antibiotics; suppress the normal microbiota flora  Diseases caused by Staphylococci S. aureus is responsible for a variety of diseases: – Skin infections (usually minor), boils, furuncles, impetigo, sties, scalded skin syndrome – Endocarditis (infection of the heart) – Osteomyelitis (infection of the bones) – Pneumonia – Meningitis (uncommon) and brain abscesses – Food-bourne diseases (food contaminated with toxins; this is not a bacterial infection) S. epidermidis is responsible for: bacteraemia, endocarditis, surgical wounds, UTIs, opportunistic infections of catheters, shunts, plastic implants and prosthetic devices…etc S. saprophyticus is responsible for UTIs Staphylococcus aureus S. aureus virulence factors  Virulence Factors Biologic Effects Peptidoglycan Abscess formation Inhibits phagocytosis Teichoic Acid Helps in attachment Protein A Inhibits antibody-mediated clearance Inhibits phagocytosis Panton Valentine Leukocidin (PVL) Necrotizing Pneumonia Exfoliative Toxins (ETA, ETB) Staphylococcal Scalded Skin Syndrome (SSSS) Enterotoxins (A-E, G-I) Superantigens (stimulate proliferation of T cells and release of cytokines); increasing intestinal peristalsis and fluid loss, as well as nausea and vomiting Fast acting, heat-stable Toxic Shock Syndrome Toxin- 1 Superantigen (stimulates proliferation of T cells and release of cytokines); produces leakage or cellular destruction of endothelial cells  Specific diseases due to S. aureus Cutaneous disease: – Folliculitis – Furuncle or boil – Carbuncle Toxin mediated disease: – Staphylococcal Scalded Skin Syndrome (SSSS) – Staphylococcal Toxic Shock Syndrome (STSS) – Staphylococcal food poisoning Pyrogenic infections/ Invasive Staphylococcal Diseases: – Abscesses – Impetigo – Wound infections – Pneumonia – Mastitis – Osteomyelitis – Septicaemia  Infections of the skin and appendages Folliculitis – Most benign infection of the hair follicle – No general symptoms Furuncles (boils) – Deep-seated infection of the hair follicle – General symptoms usually absent Carbuncles – Deep-seated infection of several hair follicles – General symptoms e.g. fever and malaise present  Infections of the skin and appendages Impetigo – Superficial infection – Mostly affects children – No general symptoms – Redness, small vesicles or blisters – Usually affects face, nose, mouth, cheeks The initial lesions are small vesicles or pustules that rupture and become a honey- colored crust with a moist erythematous base Spreading pyodermas (pus in skin)  Toxin-Mediated Diseases Staphylococcal Scalded Skin Syndrome – Disseminated desquamation of epithelium in infants Staphylococcal Food poisoning – After consumption of food contaminated with heat- stable enterotoxin, rapid onset of severe vomiting, diarrhoea and abdominal cramping, with resolution within 4-6 hours Staphylococcal Toxic Shock Syndrome – Multisystem intoxication characterized initially by fever, hypotension and a diffuse, macular erythematous rash  Staphylococcal Scalded Skin Syndrome (SSSS) Generalised Exfoliative Dermatitis – Now known as ‘Ritter’s Disease’ – Exfoliatin Toxin A and B – Newborn and