Catalase Neg GPC Flashcards
What is the scientific name for Group A Streptococcus? Where is it found as normal flora?
- Streptococcus pyogenes
- found in skin and mucous membranes of URT
What is the scientific name for Group B Streptococcus? Where is it found as normal flora?
- Streptococcus agalactiae
- URT, GIT*, Genital tracts
What would be the minimum set of primary and secondary tests required to positively identify Group A and Group B Streptococcus without using grouping sera? (ensure you understand what is meant by primary and secondary).
A:
1º GPC, Catalase neg, Fermentative, Lrg B haem.
2º Bacitracin S
B:
1º GPC, Catalase neg, Fermentative, narrow a/g haem
2º Bacitracin R, Hippurate pos
a) What does VRE stand for?
b) How have these organisms thought to have become resistant?
c) How do these organisms get into the human GIT?
a) VRE: Vancomycin resistant Enterococcus
b) High use of vancomycin and cephlasporins; use of avoparcin (glycopept. too) as animal growth promoter
c) due to R enterococci in human food from encouraging R w/ use of growth promoters
If you identified an unknown organism as a GPC that was catalase negative and salt tolerant? What genera would most likely be implicated?
group D Enterococcus
If you identified a GPC that was catalase negative and was sensitive to Bacitracin what would the most likely identity be?
Streptococcus pyogenese
Features of Streptococci & Enterococci
- GPC in chains/pairs (in clinical smear)
- catalase neg
- non-motile
- Facultative anaerobe
Virulence factors of Strep. pyogenes (Group A) & brief explanation on how it cause disease
- M proteins: adhere to epithelial cells, resist phagocytosis, & cross reactive Aby resp.
- Haemolysin O & S: toxic to cells
- Streptococcal Pyrogenic exotoxins (SPE): toxic shock syndrome, hypotension and shock, scarlet fever
- Enzyme production: (Hyaluronidase) break down CT ground substance = spread
- Hyalorunic acid capsule: adherence & resist phogocytosis
Which virulence factor is thought to be responsible for causing rheumatic fever?
(following pharyngitis infection)
M protein = cross reaction of Aby produced against Strep. Ag that react to own tissue (similar Ag)
Differentiate between rheumatic fever and glomerular nephritis.
- 1º: pharyngtitis -> 2º: Rhuematic fever
* 1º: URT infection/scarletfever OR skin/wound infection -> 2º: glomeruar nephritis
post streptococcal rheumatic fever. Discuss the clinical symptoms and lab. diagnosis.
- S: sudden onset of fever & joint pain
- congestive heart failure bc Abys produced for Ag cross react w/ tissue Ag
- LD: Inc ESR, CRP, ASOT, aDNAseB
glomerular nephritis. Discuss the clinical symptoms and lab. diagnosis.
- S: Onset after couple of weeks
- S: malaise, weakness, anorexia, oedema, headache, hypertension
- S: Aby/Ag complexes deposit in kidney => damage glomeruli
- LD: Inc ESR, dec C3, haematuria, proteinuria, inc ASOT and aDNAseB
What is the significance of measuring ASOT and DNAse B?
Measures the titre of Aby made against O Ag (ASOT) and DNAse B
In the coroner’s report (slide 20), a) what claim was made regarding the blood cultures taken from the patient by PathWest? b) Later on during the afternoon of the 5th April, 2006 the doctors at the hospital were notified of a culture result, what was the culture result? c) What assumption was made by the doctor(s)? d) What did the evidence given to the inquest say about the significance of the culture result? e) Subject to the patient having any allergies to antibiotics, what antibiotic of choice could have been used to treat this infection?
a) Expired blood culture bottles
b) Positive blood culture
c) Dural tap for headache and involution pain for abdominal pain
d) Streptococcus or Enterococcus
e) erythromycin or 1GC
If GPC have been seen in the Gram smear from a clinical sample but the culture plates record no growth, what could this indicate? What action, if any, should be taken?
Could indicate culture not incubated at ideal media and conditions (O2/AnO2/CO2). Try to re culture but best to take another sample