Question

1. When a urine culture shows greater than three different colonies on the SBA plate, no growth on the MAC plate and some growth on the CNA plate, this may be reported as?

1. No growth at 24 hours
2. cc > 100,000 CFU/ml Gram negative bacilli
3. A contaminated culture
4. Cc < 10,000 CFU/ml Gram positive bacilli

2. Which of the following urine cultures best indicates a possible infection?

1. Mixed culture with > 3 organisms seen
2. < 1,000 CFU/ml
3. >/ 100,000 CFU/ml
4. 10 CFU/ml

3. Treponema pallidum is the causative agent of?

1. Chlamydia
2. Syphilis
3. Gonorrhea
4. HIV

4. Which of the following organism is a common cause of UTI and grows best on SBA and CAN but shows no growth on MAC?

1. Klebsiella pneumoniae
2. Enterococcus faecalis
3. Escherichia coli
4. Pseudomonas aeruginosa

5. The most common type of UTI resulting from bacteria colonizing the external urogenital surface that ascend through the urethra of the bladder is known as:

1. Pyelonephritis
2. Urinitis
3. Cystitis
4. Kidneyitis

6. When a urine culture shows at least 100 colonies on the SBA plate, some isolated growth on the MAC plate, and no growth on the CAN plate, this will be reported as:

1. A contaminated culture
2. No growth at 24 hours
3. Cc > 100,000 CFU/ml Gram negative bacilli
4. Cc < 10,000 CFU/ml Enterococcal species

7. When a urine culture shoes no growth on the SBA plate, no growth on the MAC plate, and no growth on the CAN plate, this will be reported as:

1. No growth at 24 hours
2. A contaminated culture
3. Cc > 100,000 CFU/ml Gram negative bacilli
4. Cc<10,000 CFU/ml Gram positive bacilli

8. When a urine culture shows at least 100 colonies on the SBA plate, no growth on the MAC plate, and at least 100 colonies on the CAN plate, and the PYR is positive, this will be reported as:

1. A contaminated culture
2. cc > 100,000 CFU/ml Gram negative bacilli
3. cc < 10,000 CFU/ml Enterococcus species
4. No growth at 24 hours

9. A culture grown on chocolate agar and Modified Thayer Martin reveals a catalase positive, oxidase positive, Gram-negative diplococci. Which of the following organisms is most likely the causative agent?

1. Salmonella species
2. Neisseria gonorrhea
3. E. coli
4. H. influenzae

Answer 1

• Urinary tract infection (UTI) involve upper urinary tract infection, affecting the kidneys and ureter or lower urinary tract infection, affecting the urinary bladder or urethra.
• UTI is mainly caused by Escherichia coli. Other organisms associated are: Proteus, Enterococcus, Klebsiella, Staphylococcus and occasionally yeast.
• Usually. Single type of colonies is considered with count > 100,000 cfu/ml as UTI infection.
• Also, if symptoms are evident count of 1000 to 100,000 cfu/ml may be considered

• Selective and differential media like:

  SBA (Sheep blood agar)- Testing hemolysis.

  CNA (Columbia Nalidixic Acid Agar)- Differential agent antibiotic nalidixic acid

  MacConkey Agar- Selects for gram-negative bacteria. Differentiates lactose fermenters from non-fermenters.

• If there is no growth for 24-48 hours, the sample is considered as not infected.

1. Answer: C

• Different type of colonies on SBA indicate contamination with other hemolytic organisms.

2. Answer: C

• Count > 100,000 cfu/ml (of a type of organism) is considered as UTI.

3.Answer: B

• Syphilis is a sexually transmitted infection caused by organism Treponema pallidum.

4. Answer: B

• Enterococcus group D species, shows growth on CNA, SBA, but does not show growth on MacConkey agar, as are lactose non-fermenters.

4.