Common Sites Flashcards
Common sites
Skin
Ant nares
Oropharynx
Axilla
Vagina
Morphology
1.Gram positive cocci
2.Grape like clusters
3.Grows in all three planes- horizontal
Vertical
Oblique
4. Non motile
5. Non spore forming
6. Coagulase positive. ( stap aur)
7. Catalase positive
8.Hemolyses rbc. B hemolysis.
(Ut. Fe in synthesis of cytochrome enzymes used to produce energy)
9. Ferments mannitol
10. Pathogenic staphylococcus causes hemolysis on blood agar media.
Species
Stap aureus
Stap epidermidis
Stap saprophiticus
Difference points
Coagulase activity
Novobiocin sensitivity
Typical hemolysis
Mannitol fermentation
Phosphatase activity
DNAase activity
Typical diseases
Antigenic structure/cell wall components
Teichoic acid
Protein A
Peptidoglycan
Clumping factor
Capsular polysaccharide
Determinants of pathogenicity
Surface antigens
Extracellular enzymes and toxins
Surface antigens
Polysaccharide
Some strains produce exopolysaccharide- leads to successful colonization of organism to implanted prosthetic devices
(Prosthetic heart valve catheter + prev antigenic structures)
Enzymes
Catalase
Coagulase
Hyaluronidase
Staphylokinase
Others
Toxins
Enterotoxin
Exotoxin alpha, beta, delta
Leukocidins
Exofoliative toxin
Toxic shock syndrome toxin
Enterotoxin
.Superantigen
.6 serogroups(A-F)
- Serotype A- associated with food poisoning. Preformed toxin
.Plasmid mediated
.Abrupt onset: 2-6 hrs after ingestion.
.Stimulate enteric receptor in abdominal viscera from where sensory stimulus reaches vomiting center via vagus nerve
. Self limiting
.more vomitting than diarrheoa
. No fever
.food:
improperly refrigerated custard
Bakery products
Milk products
.Fairly resistant to and usually not activated by breif cooking
. Resistant to stomach acid and enzymes in stomach and jejunum
.characteristic feature:
Prominent vomitting
Watery non bloody diarrheoa
M/A of enterotoxin
Pathogenesis of stap food poisoning
. Acts as super antigen within GIT to stimulate release of large amts of IL 1 ans IL 2 from macropahages and helper T Cells respectively.
. Prominent vomitting is caused by serotonin released by mast cells, which stimulates the enteric system via vagus nerve to activate the vomitting center in brain (chemoreceptor triggering zone)
Toxic shock syndrome
. A severe and fatal disorder characterized by multiple organ dysfunction
. In most cases, associated with menstruating female who uses tampons or indivisuals with wound infection
. Patients with nasal packing used to stop bleeding from nose
. TSST Produced locally by s. Aureus in nose, vagina and other infected sites
. Toxins enter blood stream and cause toxaemia
.
Clinical features:
Myalgia
Rash
Fever
Hypotension
Diarrheoa
Desquamation
Diseases by s. Aureus
Fununcles and carbuncles
Food poisoning
Impetigo
Pneumonia
Pyoarthrosis
Bacteremia
Osteomyelitis
Scalded skin syndrome
Toxic shock syndrome
Diseases by other staphylococcus
Infections associated with prosthetic devices -
by s. Epidermidis
Urinary tract in sexually active women-
By s. Saprophyticus
Methicilin resistant staphylococcus aureus
Means multi drug resistant.
Treated by vancomycin
. Abt 20% s. Aureus are methicilin resistant. Due to presence of mecA gene
. Nowadays vancomycin resistant staphylococcus has been isolated.
This is treated with linozolide.
