APE 1 Flashcards
Distinguer la pathogénicité du Staphylococcus aureus des Staphylococcus à coagulase négative.
Staphylococcus aureus:
HIghly pathogenic. Contains coagulase whihc can cause fibrin formation.
Staphylococcus à coagulase négative:
do not produce coagulase
less virulant and thought of as opportunistic infections
Préciser quel test de laboratoire permet de distinguer le Staphylococcus aureus des autres espèces
Test de laboratoire: Coagulase Test
Staphylococcus aureus reservoir
Normal flora on human skin and mucosal surfaces
Organisms can survive on dry surfaces for long periods
Staphylococcus aureus Transmission
Person-to-person spread through direct contact
Exposure to contaminated
objects (e.g., bed linens, clothing)
Transmission comprenne le contact cutané et les gouttelettes respiratoires
Transmission nosocomiale
Indiquer à quelle catégorie appartient chacun des facteurs de virulence suivants et indiquer quel est leur effet biologique : la capsule, le biofilm, le peptidoglycane, l’acide téichoïque, la protéine A, les cytotoxines, les toxines exfoliatrices, les entérotoxines, la coagulase et l’hyaluronidase.
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Structural Virulence Factors:
- Capsule: enhances bacterial survival by protecting against phagocytosis and immune clearance.
- Biofilm: allows bacteria to adhere to surfaces and form a protective matrix, contributing to antibiotic resistance and immune evasion.
- Peptidoglycane : Structural component of the bacterial cell wall. It provides rigidity to the cell wall and protection against osmotic lysis.
- Acide téichoïque : Structural component of the cell wall. It contributes to cell wall stability and may be involved in host-pathogen interactions.
- Protéine A: Inhibits opsonization and phagocytosis by neutrophils and macrophages.
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Toxins:
- Cytotoxins: These include pore-forming toxins such as alpha, beta, and gamma toxins, which damage host cell membranes, leading to cell lysis.
- Toxins exfoliatrices: They cause exfoliation of the skin
- Entérotoxines: These are heat-stable toxins that cause food poisoning by stimulating vomiting and diarrhea when ingested.
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Enzymes:
- Hyaluronidase: Hydrolyzes hyaluronic acid, facilitating bacterial spread and tissue invasion.
- Coagulase: Converts fibrinogen to fibrin, leading to the formation of fibrin clots. This can protect bacteria from host immune responses
Which bacteria causes osteomyelitis, and septic arthritis.
Par quel(s) mécanismes(s) cette bactérie parvient-elle à causer des infections des os (ostéomyélite) et des articulations (arthrite septique).
Staphylococcus aureus
Osteomyelitis, and septic arthritis result from proliferation of the organisms, leading
to abscess formation and tissue destruction → Hematogenous Spread
Quelles informations épidémiologiques et cliniques (symptômes) devraient faire évoquer un diagnostic d’intoxication alimentaire attribuable à Staphylococcus aureus
Disease is caused by bacterial toxin present in food rather than from a direct effect of the organisms on the patient
Rapid Onset of Symptoms
Short Duration of Illness
No Fever
Frequent cause of nosocomial infections
Patients with indwelling medical devices such as catheters, prosthetic implants, and intravenous lines
Staphylococcus epidermidis
À propos de Staphylococcus epidermidis expliquer comment cette bactérie peu virulente réussit à causer des infections.
Ability to form biofilms on the surfaces of these devices contributes to its pathogenicity and resistance to antibiotics.
Biofilm formation on the surfaces of these devices facilitates bacterial adherence and colonization, leading to chronic, difficult-to-treat infections.
biofilm is like a protective, slimy home where bacteria live together as a community.
Décrire l’infection la plus fréquemment causée par Staphylococcus saprophyticus.
urinary tract infections in young, sexually active women and is rarely responsible for infections in other patients
Décrire le rôle de la capsule et de la protéine M dans la pathogénèse des infections causées par Streptococcus pyogenes
capsule inhibits phagocytosis by host immune cells,
M protein: Antigenic Variation, Adherence, Immune Evasion
quelle exotoxine est responsable de l’éruption observée dans la scarlatine.
Streptococcus pyogenes
pyrogenic exotoxin
expliquer la pathogenèse de la fièvre rhumatismale (RAA)
Acute Rheumatic Fever (ARF): This is an inflammatory condition that can occur following untreated or inadequately treated streptococcal pharyngitis caused by Streptococcus pyogenes.
antibiotique de choix pour le traitement des infections suppuratives à Streptococcus pyogenes.
penicillin
Streptococcus agalactiae people at risk
Neonates
acquired by neonates from mother during pregnancy or at time of birth
