Micro basics Flashcards
Example of an aerobic bacilli
C. diptheriae
Example of an anaerobic bacilli
C. difficile
Why do gram positive bacteria stain purple?
Thicker layer of peptidoglycan
How do we distinguish between gram positive cocci?
Catalase test
Example of a positive and a negative result of the catalse test
Catalse positive = Staphylococci, eg S.aureus
Catalse negative = streptococci, eg S. pneumoniae
How can we distinguish S.aureus from other staphylococci?
Coagulate test on blood agar
- S.aureus = gold
How can we distinguish between different streptococci?
Haemolysis test on blood agar
Results of the haemolysis test and an example for the results
Beta haemolysis = clear → antigenic groups
Alpha haemolysis = green, eg strep viridans
What does Lancefield grouping differentiate?
Beta haemolytic streps → A,B,C,G antigenic groups
Which group A strep is optochin resistant?
Strep viridans (alpha haemolysis) or S pyogenes (beta haemolysis)
First test to distinguihs between gram negative bacilli
MacConkey agar → lactose fermenters & non-lactose fermenters
Give 2 examples of lactose fermenting gram negative bacilli
E. coli
Klebsiella
Give 2 examples of non-lactose fermenting gram negative bacilli
Salmonella
Shigella
Function of the oxidase test?
Distinguish between non-lactose fermenters
Example of a bacteria which is gram negative, MacConkey test negative and oxidase test positive
Pseudomonas
Example of an atypical cause of pneumoniae & explain where this may be caught
Legionella
- History of a holiday
- Dodgy AC, eg multiple people all catching it after the same event
Treatment of pneumonia
Amoxicillin + clarithromycin
(clarithromycin covers atypical pneumonia causes)
If a patient has a very high CURB-65 score what does this indicate & how would we treat them?
Severe form of pneumonia
Give Co-amoxiclav and clarithromycin
Most likely cause of IE following dental visits?
Strep viridans
Abx given to pt with IE caused by strep viridans?
Benzyl penicillin & gentamycin
Dukes criteria: what is it used for and what are the criteria?
Diagnosis of IE.
2 major, 1 major 3 minor or 5 minor present for diagnosis.
BE = major, FEVER = minor
- Blood cultures +ve greater than 12 hours apart
- Echo = evidence of endocardial involvement
- F = fever
- E = echo
- V = eVidence from microbiology
- E = evidence from immunology, eg Roth spots, osler nodes etc
- R = risk groups, IVDU, prosthetic valves
Antibiotic of choice to treat S.aureus infections
Flucloxacillin
Appearance of a CSF film when infection is: bacterial, viral, fungal/TB
Bacterial = turbid, eg cloudy/opaque
Viral = clear
Fungal/TB = fibrin web
Treatment of n.meningitidis in primary care
Benzylpenicillin
