Common Lower Resp pathogens

Question 1

Name 5 categories of gram stain and associated “bug” that are major causes of bacterial lower respiratory infections

Answer 1

1. GPC chains: Strep pneumo
2. GPC clusters: Staph aureus
3. GN coccobacilli, small: Haemophilus influenzae
4. GN diplococci: MOraxella or Neisseria meningitidis
5. GNB: enterics or pseudomonas

Question 2

How would you ID H. influenzae?

Answer 2

1. No growth in SBA but smooth, round, flat opaque tan on CHOC in CO2
2. small gram-neg coccobacilli
3. Cat +, Ox+, nonmotile
   requires both X and V factor found on CHOC

Question 3

What H. influenzae type causes meningitis, to which there is now a vaccine that has reduced childhood infection dramatically?

Answer 3

type b, HIb

Question 4

What haemophilus biotype causes pinkeye and what spp causes chancroid?

Answer 4

pinkeye: H. influenzae, biotype aegyptius
Chancroid: H. ducreyi

Question 5

How is Moraxella diff from Neisseria meningitidis?

Answer 5

It doesn’t produce acid from any sugars on CTA; it is butyrate esterase positive (the cat disk), DNAse, and catalase positive; has more opaque colonies