Principles of Infectious Disease III: Techniques and Testing

Question 1

What are the eight essential types of specimens?

Answer 1

• plasma
• fluid
• biopsies
• blood
• tissue
• urine
• swabs in general are not good specimens. may swab throat for respiratory virus
• sputum is a poor sample

Question 2

What are the three essential diagnostic tests?

Answer 2

• amplified nucleic acid techniques
• stains
• bacterial culture

Question 3

What are the seven types of stains (diagnostic tests)?

Answer 3

• gram stain
• acid-fast bacteria stain
• fungal stains
• parasitology stains
• vital stains (acridine orange)
• antibody to antigens
• nucleic acid probes

Question 4

What are two types of bacterial culture (diagnostic tests)?

Answer 4

• protein-based, genotype, or phenotype identification

- agar and antibiotics discs, broth dilution

Question 5

What are two types of antimicrobial testing?

Answer 5

• susceptibility to antibiotics

- agar and antibiotics discs, broth dilution

Question 6

What are the key interactions and relationships between clinicians and clinical microbiology and epidemiology, for pre-analytical, analytical and post-analytical issues?

Answer 6

• determine appropriate patients for culture
• choose appropriate specimen for culture
• read the test results correctly
• treat appropriately based on test results

Question 7

What are the general approaches to laboratory diagnosis of infection?

Answer 7

• obtain a specimen from infected site
• use appropriate procedure for the pathogen (stain specimen, observe if bacteria are present and determine morphology, gram +/-, and whether single or multiple pathogens are present)
• culture the specimen on appropriate media to obtain a pure culture. Incubate in presence or absences of oxygen as appropriate
• perform antimicrobial susceptibility tests

Question 8

What are the important steps that precede laboratory workup?

Answer 8

• choosing appropriate specimen to examine
• obtaining specimen properly to avoid contamination from normal flora
• transporting the specimen promptly to the lab or storing it correctly
• providing any essential information to the lab to guide the laboratory diagnosis

Question 9

What are the three types of specimen collected?

Answer 9

• direct
• indirect
• sample from site with normal flora

Question 10

What are types of direct specimen?

Answer 10

Specimens collected form normally sterile tissues or body fluids
- lung, liver, blood, CSF

Question 11

What are types of indirect specimen?

Answer 11

Specimens that have passed through sites that aree known to be colonized by normal flora

• specimens that are inflammatory exudates
• -> urine or expectorated sputum

Question 12

What are types of specimen collected from sites with normal flora?

Answer 12

• large intestine
• pharynx
• oral cavity
• primarily an issue with bacterial diagnosis since they dominate makeup of normal flora; less of an issue with viral flora, there is little viral normal flora

Question 13

What are direct methods for diagnosing pathogens?

Answer 13

• wet mounts

Question 14

What are routine culture tests?

Answer 14

• isolation and ID of bacteria and fungi

- isolation and ID of viruses

Question 15

What are serologic methods?

Answer 15

Serology methods include:

• antibody detection whereby antigen preparations are used to detect circulating antibodies as evidence of a current or previous infection
• antigen detection where antisera is used to detect circulating antigens

Question 16

What are nucleic acid amplification tests?

Answer 16

Polymerase Chain Reaction (PCR) is most commonly used NAAT