URT & LRT

Question 1

What group of organisms is most commonly responsible for pharyngitis?

Answer 1

• most infections (80%) caused by viruses

- if bacterial, primarily look for B-haemolytic streptococci

Question 2

a) What is the causative agent of whooping cough?

b) List the media that you would use to isolate the pathogen.

Answer 2

a) Bordetella pertussis

b) Bordet-Gengou, Charcoal medium, Regan Lowe (all HBA with other ingredients for detecting Bordetella sp.)

Question 3

What two organisms must be present in a Gram stain to report the presence of Vincent’s angina?

Answer 3

1. Treponema vincentii: squiggly GNeg (Bacillus?)

2. Fusobacterium sp.: GNB cigar-shaped

Question 4

Which B haemolytic streptococci are routinely associated with pharyngitis?

Answer 4

B haemolytic Streptococci from Groups A, B, C, F, G

Question 5

List two common causes of conjunctivitis?

Answer 5

St. pneumoniae & Haemophilus influenzae (note both NF)

Question 6

What is:

a) otitis media?
b) otitis externa?

Answer 6

a) Otitis media: middle ear infection (where ear drum is)

b) Otitis externa: outer ear infection

Question 7

a) What is the most common cause of bacterial otitis media?

b) Otitis externa?

Answer 7

a) Otitis media: St. pneumoniae (50%) & Haemophilus influenzae (20-30%)
b) Otitis externa: Pseudomonas aeruginosa (80%)

Question 8

If you saw black dots/specks growing in culture from an ear swab together with cotton wool like colonies, what would the likely identity of the organism be?*

Answer 8

Fungal? Aspergillus sp?

Question 9

During processing of sputum, why is the macroscopic description usually recorded?

Answer 9

gives clues as to what to expect microscopically and also can detect URT contamination if contains saliva

Question 10

If you identified a very small GNB in a Gram smear from a sputum sample and the resulting culture plates grew numerous small-medium grey colonies on a CHOC agar plate incubated in CO2, NG on MAC and minimal growth on BA, what would be the most likely identity of this organism?

Answer 10

Haemophilus influenzae

Question 11

List 3 reasons why sputum samples are digested and then set up for culture?

Answer 11

• Exposes pathogens that might be obscured by leucocytes & mucus
• DIlutes out NF
• Provides cfu limits for significance

Question 12

How many bacteria on an agar plate from a digested sputum sample would equate to >10^7 orgs/ml?

Answer 12

> 25 colonies (of 1 organism)

Question 13

What does the presence of large numbers of epithelial cells in a sputum or urine indicate? Is the sample adequate for assessing bacterial infection?

Answer 13

Contaminated sample due to poor collection = Hi # of NF = not adequate for assessing bacterial infection

Question 14

List 3-6 reasons antimicrobial susceptibility testing might be undertaken if < 10^7 orgs/ml of an organism was present in a digested sputum?

Answer 14

• If isolated previously
• fungal pathogen
• if organism is pathogenic )on any level) e.g. M. TB
• Immunocompromised
• patient has cystc fribrosis
• Patient has tracheostomy tube

Question 15

What is the reason for placing an optochin disc onto a sputum BA culture plate from an undigested sputum?

Answer 15

to test if the organism is Strep. pneumoniae (S to optochin)

Question 16

What are the names of the two staining methods used to detect TB in a clinical smear?

Answer 16

• Ziehl-Neelsen or Kinyoun stain (acid-fast bacilli)

- Fluoroscent staining

Question 17

If you saw numerous GNC in a Gram smear from a sputum, what organisms might be indicated?

Answer 17

Neisseria sp.

Question 18

What structures fall under the:

a) URT
b) LRT

Answer 18

a) URT: middle ear, mastoid cavity, nasal sinuses, nasopharynx
b) LRT: larynx to lungs

Question 19

Lab features of Bordetella pertussis

Answer 19

• GNCB
• Silvery colonies (when incubated for 3-5 days)
• Haemolysis on BG medium (Bordet-gengou)

Question 20

Difference b/w bacterial & viral infection in eye regarding discharge

Answer 20

• B: mucopurulent discharge - sticky

* V: clear, watery discharge

Question 21

Name 2 common bacteria that causes Acute conjunctivitis & name 1 treatment

Answer 21

a) Cause: S. pneumoniae & H. influenzae

b) Chloramphenicol

Question 22

Difference b/w Typical & Atypical Pneumonia;

• Hx
• Clinical findings
• Lab features
• Causitive agent:

Answer 22

T  |   At (opposite results as T)
Hx: Abrupt onset, Rigors, Severe symptoms
CF: Purulent sputum
LF: Neutrophilia (L. shift)
CA: bacterial (vs viral for At)