Past MCQs Flashcards
Is Salmonella Urease positive or negative?
Urease positive
What media would be most suitable for isolation of Salmonella enterica serotype typhi? Why?
Bismuth Sulphite agar
Selective for Salmonella species
How will S. typhi grow on Bismuth Sulphite agar
Black colonies surrounded by brownish-black zone
What part of the Salmonella bacterium are the O (somatic) antigens found on?
Lipopolysaccharide
What is the optimal enrichment medium for the isolation of Salmonella?
Selenite cystine broth
What media is best for the selective isolation of Corynebacterium diptheria?
Hoyle’s Tellurite agar
How does Corynebacterium diptheria grow on Hoyle’s Tellurite agar
Grows as black/grey colonies
White kind of infection does H. influenzae commonly cause?
Acute bronchitis
What would slender gram negative coccobacilli in a sputum gram stain indicate?
Haemophilus influenzae
How does S. pyogenes grow on MacConkey agar?
S. pyogenes is usually unable to grow
What biochemistry CSF results would you expect from a bacterial meningitis
Increased protein
Decreased glucose
How does viral meningitis affect CSF glucose levels?
Shouldn’t really affect glucose levels
For how long should blood cultures be incubated when querying sub-acute bacterial endocarditis
21 days
What is meant by sterile pyuria and what would cause this
High white blood cells in urine
Without culturable bacteria
Antibiotic treatment
Non culturable organisms e.g. TB or Chlamydia
Cancer of bladder/urinary tract
What would indicate a contaminated urine specimen
Squamous epithelial cells
What is cystitis and what is a common cause in young women?
Inflammation of the bladder
95% of cases = E. Colil
What media does EUCAST recommend for disc sensitivities for non fastidious organisms
Mueller-Hinton agar
What does EUCAST stand for
European Committee on Antimicrobial Susceptibility Testing
Give an example of an obligate anaerobe which is usually susceptible to metronidazole
Bacteroides fragilis
Give an example of an organism where extended spectrum beta-lactamases may be detected
Escherichia coli
What gene is responsible for MR in staph aureus
MecA
Is E. Coli O157 able to ferment sorbitol?
No -> usually unable to ferment sorbitol
But normal E. Coli is able to
What is the only non zoonotic Enteric organism (generally)
Shigella dysenteriae
How is C.diff diagnosed
Demonstration of enterotoxin A and cytotoxin B in patient faeces
Give an example of a hazard group 3 pathogen
Mycobacterium tuberculosis
What is Hoyles tellurite used for?
Corynebacterium diphtheriae
What does sodium poylanetholsulfonate (SPS) in blood culture media do?
Inhibits phagocytosis and bactericidal activity of serum
Inactivates complement
Neutralises lysozymes and aminoglycosides
i.e. keeps organisms alive -> stops immune reaction in patient blood
prevents the killing of bacteria by innate cellular and humoral factors
What bio results would you expect in the CSF of someone with bacterial meningitis?
Increased protein
Decreased gluocse
What test is used to differentiate C. albicans from other Candida species
Germ tube test
What would indicate renal damage in urine specimen
Protein casts
Is Proteus mirabilis urease positive or negative?
Urease positive
What is the germ test for Candida
We dont do this
Fungal spores are suspended in animal serum and examined by microscopy
What would coffin-shaped crystals in urine indicate
Triple phosphate crystals
What organism cultured from a superficial wound swab is most associated with impetigo and scalded skin syndrome?
Staphylococcus aureus
What are some tell tale symptoms of S. aureus wound infection
Impetigo
Scalded skin syndrome
What MacFarland standard is required for disc sensitivities by EUCAST
0.5 MacFarland
What is the commonest reported cause of bacterial gastroenteritis in Ireland
Campylobacter jejuni
What organism is associated with pseudomembraneous colitis
C. diff
How would you make chocolate agar more selective for H. influenzae for use on a sputum sample
Add bacitracin
What is the most common cause of pharyngitis
Viruses
What is the most common cause of “swimmer’s ear”/acute diffuse ottis externa
Psuedomonas aeruginosa
What is the most important virulence factor of pathogenic S. pneumoniae
Polysaccharide capsule
What is the most common cause of meningitis in neonates
Streptococcus agalactiae (BHS)
What would be indicative of a sub-arachnoid haemorrhage in a CSF
Yellow coloured CSF
Xanthochromia of CSF
What is a bladder infection known as
Cystitis
What infection does S. saprophyticus most commonly cause?
Urinary tract infection in the sexually active young women
How should you report the resistance of MRSA?
Resistance to all beta-lactams
Generally how are all wound swabs cultured?
Aerobically and anaerobically
