MLPAO Microbiology and Parasitology Clinical Applications

Question 1

A Gram stain of a positive blood culture shows gram-positive cocci in clusters. What organism is most likely and what empiric therapy should be communicated?

Accepted Answer

Staphylococcus species; vancomycin pending identification and susceptibilities

Answer

Streptococcus pneumoniae; penicillin

Answer

Enterococcus; ampicillin

Answer

Neisseria meningitidis; ceftriaxone

Question 2

A urine culture grows more than 100,000 CFU/mL of a single organism. What does this indicate?

Accepted Answer

Significant bacteriuria consistent with urinary tract infection

Answer

Contamination

Answer

Normal flora

Answer

Specimen collection error

Question 3

A laboratory identifies a Salmonella species from a stool culture. What is the reporting obligation in Canada?

Accepted Answer

Salmonella is a reportable/notifiable disease and must be reported to public health authorities

Answer

No reporting is required

Answer

Only typhoid Salmonella needs reporting

Answer

Reporting is optional and at the physician's discretion

Question 4

Which infection control precaution is implemented when Clostridioides difficile infection is suspected?

Accepted Answer

Contact precautions with hand washing using soap and water (not alcohol-based hand rub)

Answer

Standard precautions only

Answer

Airborne precautions with N95 respirator

Answer

Droplet precautions only

Question 5

A wound culture grows a beta-hemolytic, catalase-negative, gram-positive coccus that is PYR-positive. What is the most likely identification?

Accepted Answer

Group A Streptococcus (Streptococcus pyogenes)

Answer

Staphylococcus aureus

Answer

Enterococcus faecalis

Answer

Group B Streptococcus

Question 6

A patient with HIV has CD4 count below 200 cells/µL and presents with chronic watery diarrhea. Modified acid-fast stain of stool shows small round pink oocysts (4-6 µm). What is the diagnosis?

Accepted Answer

Cryptosporidiosis

Answer

Giardiasis

Answer

Cyclosporiasis

Answer

Isosporiasis