Clinical microbiology 2

Question 1

Introduction

Answer 1

Fast and correct identification are important

Correct treatment of patient
Decrease spread of infection

Lab samples

Correctly collected, stored and transported

Good collaboration is key

Question 2

Remissen?

Answer 2

Sample type Enough sample and few contaminents

Sample-topical - From where and circumstances

Transport time - correct T?

Infection started?

Traveling - lab has to broaden the analysis

Prev. or ongoing treatment - antibiotic-allergies

Condition of patient - Low immune status broaden the analysis

Question 3

Collecting?

Answer 3

Swabs made from different material with high absorbency

• Transport media included
• Fibers on swab act as a brush
• Releasing sample.material to solution

Several analysis from one sample

Question 4

Direct methods?

Answer 4

Specific bacterial species with different methods

• Growth and identification -long time
• Nucleic acids - short

Question 5

Indirect methods?

Answer 5

Traces from microorganisms

• Levels of antibodies
• Toxins

Question 6

Defined media?

Answer 6

Defined amount of pure chemicals in deionized water - exact composition, qualitative and quantitative is unknown

Question 7

Complex media?

Answer 7

Digested products and the exact composition is unknown

Question 8

Agar?

Answer 8

A complex polysaccharide from marine algae - bacteria cannot degrade it melts at 85 and solidify at 40

Question 9

Enriched growth media?

Answer 9

Supplemented with specific growth factors to improve growth of specific pathogens

Question 10

Selective growth media?

Answer 10

Supplemented with substances that slectively inhibits growth to some

Question 11

Differential growth media?

Answer 11

Supplemented with an indicator that reacts on special chemical reactions and can be used to differentiate between species. Often based on changes in pH.

Question 12

Hemolysis?

Answer 12

Many bacteria produces hemolysins

alphahemolysins - green color
betahemolysins - total hemolysis
gammahemolysis - No hemolysis

Question 13

Blood-culturing?

Answer 13

Anaerobic - organe
Aerobic - green
Pediatric/children - yellow

Question 14

Procedure?

Answer 14

8-10 is added to each flask and 2-4 per patient

Positive cultures - gram staining or selective - differential agar
MALDI-TOF after 6h
Resistance testing - KirbyBauer test

Question 15

Direct methods?

Answer 15

MALDITOF - gold standard

Question 16

Chromogenic agar?

Answer 16

Inoculation to chrome-agar

- Differential media and contains biochemical markers - specific colony = specific color

Question 17

PCR?

Answer 17

DNA and fast nucleic acid from both living and dead organisms

Question 18

Quick tests?

Answer 18

No equipment and < 30 min to perform and max 2 reagents

Question 19

Indirect methods?

Answer 19

Urinanalysis - nitrate to nitrite

Nitrite positive - E. coli Klebsiella spp and Proteus spp

Nitrite negative - Staphyloccus spp enteroccus spp Pseudomonas spp

Question 20

Sources of error - Nitrite test?

Answer 20

False negative

• Short bladder incubation time
• Low bacterial concentration
• Low nitrite concentration
• High intake of Vit C

False positive

• Intenesely colored urine
• Medication

Question 21

Source of error - Leucocyte test?

Answer 21

False negative
- Tetracycline

False positive
- Discolored urine

Question 22

UTI’s?

Answer 22

Semi-quantitaive estimations
- Growth method that determines CFU/ml 
Two media is needed 
- Blood agar as reference media 
CLED-media 
- Differential but not selective 
- Lack electrolytes 
Chromogenic agar 

10 microl on agarplates

• Plastic loop
• Micropipette and plastic loop

> 10 microL generates more accurate results

Question 23

Resistance testing?

Answer 23

MIC - bacteria in tubes with increasing concentration of antibiotics

Kirby-Bauer - incubated on agar with paper discs containing antibiotics

S - sensitive = standard dose
I - Intermediate = Higher dose req.
R - Resistant = cannot use