laboratory testing

Question 1

when should you send samples

Answer 1

only if you think there is an infection at that site and if you think that the results will give you an answer OR if there is a clinically relevant colonising organism you should know about

Question 2

many people are healthy carries of what

Answer 2

strep pneumonia but blood cultures are more likely to be positive in severe disease caused by strep pneumonia

Question 3

false positive blood cultures can occur

Answer 3

and are most commonly caused by poor aseptic technique which most commonly causes skin commensals to contaminate the sample

Question 4

common skin commensals

Answer 4

staph epidermis, corneybacterium, bacillus species

Question 5

exception to ignoring skin commensals

Answer 5

skin commensals can be the cause of disease in those with prosthetic material

Question 6

soes strep pneumonia commonly cause false positive results

Answer 6

no if strep pneumonia positive then it is likely to be causing disease

Question 7

cultures for pneumonia

Answer 7

• blood culture and sputum culture

Question 8

sputum cultures commonly contain

Answer 8

commensals from the mouth and throat

Question 9

almost all cases of haemophilus influenza isolated from the blood and CSF are

Answer 9

capsular type B

Question 10

haemophilus influenza is a

Answer 10

gram negative coccobacillus which is generally aerobic but can grow as a facilitate anaerobe

Question 11

what is used to culture haemophilus influenza

Answer 11

chocolate agar, blood agar will not work

Question 12

host factors which increase risk of infection

Answer 12

• hospitalised for more than 48 hours
• on a ventilators
• immunosuppression
• chronic lung disease
• epidemiological (i.e. mycoplasma more common in young)
• recent reveal (Mers Co-V)

Question 13

what is Mers Co-V

Answer 13

middle east respiratory syndrome coronavirus

Question 14

atypical pneumonia is

Answer 14

any pneumonia which is not caused by strep penumonia= legionella, mycoplasma, coxeilla, chamydophillia psittaci

Question 15

most atypical pneumonia is sensitive to

Answer 15

doxycycline except legionella which is treated with erythromycin

Question 16

legionella pneumonia has

Answer 16

a high mortality

Question 17

mycoplasma pneumonia

Answer 17

is more common in children and young adults, it is known as the walking pneumonia as it does not cause many symptoms

Question 18

complication of mycoplasma pneumonia

Answer 18

erythema multiforme

Question 19

coxiella brunetti is known as

Answer 19

Q fever and is spread from sheep and goats

• causes a pneumonia and pyrexia of unknown origin
• diagnosed using serology

Question 20

to diagnose all atypical pneumonia (except legionella)

Answer 20

use serology; send acute and convalescent blood samples (convalescent sample is taken 7 or more days after the acute sample)

Question 21

what does serology do

Answer 21

compares immunoglobulin response levels over time

Question 22

diagnosing a virus

Answer 22

nasopharyngeal or throat swabs for PCR

Question 23

pcr detects

Answer 23

• influenza type A and B, parainfluenza virus types 1-4, coronavirus, rhinovirus, metapneumonovirus, adenovirus, enterovirus, and mycoplasma

Question 24

mycoplasma is the only

Answer 24

bacteria detected by PCR

Question 25

urine antigen is used to detect

Answer 25

legionella it only detects serogroup 1 as 95% of legionella is caused by this

Question 26

legionella penumonia

Answer 26

gram negative strict aerobic bacillin

Question 27

legionella is spread via

Answer 27

lukewarm aerosolised water (air-condition, hot tubs and pools)

Question 28

legionella multiplies within

Answer 28

amoeba and protozoa, but human alveolar macrophages look like protozoa so legionella invades and multiplies within them