Diagnostic Microbiology culture based diagnostics

Question 1

What is the role of microbiology labs in diagnosing infectious diseases

Answer 1

1. Diagnosis of infectious diseases
2. Clinical interface with clinicians
3. Surveillance
4. Infection control and antimicrobial stewardship
5. Research
6. Teaching and training

Question 2

What is the difference between culture-based diagnosis and non-culture based diagnosis

Answer 2

Culture-based: Determine the presence of microorganisms by initiating Growth of the organisms using suitable laboratory conditions

Non-culture based: Determine the presence of microorganisms using genetic material, antibody reaction to organisms and antigens

Question 3

List the 3 steps of the diagnostic cycle

Answer 3

1. Pre- analytical eg patient goes to HCP, the sample is taken and delivered to the lab
2. Analytical eg Examination and processing of the specimen
3. Post-analytical eg doctor interprets the result to the patient

Question 4

What is the function of the trio

Answer 4

The function of the trio is to enable the doctor to manage the patient to determine if the chosen treatment is correct

Question 5

Explain the procedure of the trio in assisting the HCP to treat disease

Answer 5

1. Microscopy: Gram staining will tell the HCP if the choice of antibiotics covers the microorganisms empirically
2. Culture: To determine the name of the organism
3. Susceptibility: Will the choice of antibiotics work on the exact strain of the organism

Question 6

Which samples can be processed using MCS to determine the presence of bacteria

Answer 6

blood culture ,CSF , Sputum ,Urine ,Stool ,Tissue , Fluid ,pus and pus swab

Question 7

Which samples can be processed using MCS to determine the presence of fungi?

Answer 7

Blood culture, Urine, stool, body fluids, CSF Sputum, tissue, pus, pus swab

Question 8

Which samples can be processed using microscopy to determine the presence of parasites

NB: Culture and susceptibility cannot be used on parasites

Answer 8

Sputum, stool, Tissue, fluid, pus, and urine

Question 9

T/ F: Viruses cannot be cultured

explain your answer

Answer 9

False, viruses can be cultured, it is a difficult and tedious process and thus most viral diseases are diagnosed using molecular methods

Question 10

How long does it take to grow bacteria, fungi, and mycobacteria

Answer 10

Most bacteria: 24-48 hrs, some bacteria : 3-5 days
Fungi: 6 weeks
Mycobacterium: 6 weeks

Question 11

How are organisms identified after being cultured

Answer 11

• Array of biochemical tests
• Molecular identification eg PCR
• Mass spectrology

Question 12

What are the methods used to determine the susceptibility of a bacteria

Answer 12

• Disk diffusion
• Antibiotic gradient strips
• Automated systems

Question 13

What criteria is used to reject samples from the lab

Answer 13

• Unlabled / Imprperly labeled
• leaking / cracked container
• old sample
• inapprpriate test required
• specimen recieved in formatin
• Insufficient sample
• Expired collection devise used
• incorrect packaing
• incomplete form