MLPAO Microbiology and Parasitology Clinical Applications 2

Question 1

What is the appropriate specimen collection for anaerobic culture of a wound infection?

Accepted Answer

Tissue biopsy or aspirate of deep wound, transported in anaerobic transport system

Answer

Proper anaerobic culture requires tissue or aspirate specimens from the deep wound (avoiding surface flora), collected and transported in anaerobic transport systems that maintain an oxygen-free environment. Surface swabs are unacceptable because they contain aerobic colonizers and expose anaerobes to lethal oxygen.

Question 2

A sputum Gram stain shows many squamous epithelial cells (>25 per low power field) and few white blood cells. What should the technologist do?

Accepted Answer

Reject the specimen as it represents oral contamination and request a new specimen

Answer

A sputum specimen with >25 squamous epithelial cells per low power field indicates oral/salivary contamination rather than a true lower respiratory specimen. The specimen should be rejected according to Murray-Washington or Bartlett quality criteria, and a new properly collected specimen requested. This prevents misleading culture results.

Question 3

Which organism is the most common cause of bacterial meningitis in Canadian adults?

Accepted Answer

Streptococcus pneumoniae

Answer

Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults in Canada. It appears as gram-positive lancet-shaped diplococci on CSF Gram stain. Since the introduction of Hib vaccine, H. influenzae meningitis has decreased dramatically. In neonates, Group B Streptococcus and E. coli are more common.

Question 4

A culture from a diabetic foot wound grows a polymicrobial mixture including Bacteroides fragilis. What is the significance?

Accepted Answer

B. fragilis is a significant anaerobic pathogen that is resistant to many antibiotics and requires specific anaerobic coverage

Answer

Bacteroides fragilis is the most clinically significant anaerobic pathogen, commonly found in polymicrobial diabetic foot infections, intra-abdominal abscesses, and wound infections. It produces beta-lactamase and is resistant to many antibiotics. Metronidazole, carbapenems, or beta-lactam/beta-lactamase inhibitor combinations are typically effective.

Question 5

What is the clinical significance of identifying Streptococcus agalactiae (Group B Strep) in a vaginal/rectal screening culture at 35-37 weeks of pregnancy?

Accepted Answer

Positive screening requires intrapartum antibiotic prophylaxis to prevent neonatal GBS disease

Answer

GBS colonization detected on prenatal screening (35-37 weeks gestation per Canadian guidelines) requires intrapartum antibiotic prophylaxis (IAP), typically IV penicillin or ampicillin, to prevent neonatal early-onset GBS disease (sepsis, pneumonia, meningitis). Without IAP, approximately 1-2% of colonized mothers' newborns develop invasive GBS disease.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Microbiology and Parasitology Clinical Applications 2