Bugs for Clinical Diseases

Question 1

What bacterial organisms cause pharyngitis?

Answer 1

*somewhat trick question, as there are several spp that can be pathogenic
*THINK GROUP A STREP FIRST (steptococcus pyogenes)
*Secondary (other) species:
Group C Strep
Arcanobacterium haemolyticum
Chlamydophila pneumoniae
Neisseria gonorrhoeae
Corynebacterium diptheriae
Corynebacterium ulcerans,
Mycoplasma pneumoniae
Francisella tularensis (rare, bioterrorism, serious)

Question 2

What bacterial organisms most commonly cause sinusitis?

Answer 2

COMMON:
Streptococcus pneumoniae
Haemophilus influenzae
mixed anaerobes and aerobes
Moraxella catarrhalis
LESS COMMON:
Staph aureus
group A strep
Chlamydophila pneumoniae
Pseudomonas aeruginosa
'gram negative rods'

Question 3

What bacterial organisms most commonly cause epiglottitis?

Answer 3

Haemophilus influenzae
Strep pneumoniae
Staph aureus

Question 4

What bacterial organisms most commonly cause otitis externa?

Answer 4

Pseudomonas aeruginosa
Staph aureus
Group A strep

Question 5

What bacterial organisms most commonly cause otitis media?

Answer 5

BIG THREE:
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
OTHER, LESS COMMON:
Staph aureus
group a strep
mixed anerobes and aerobes (polymicrobial...abcess?)

Question 6

How should one treat a Streptococcus agalactiae infection?

Answer 6

These are universally susceptible to penicillin and beta-lactams

• the only tricky part comes from true, serious allelrgic (anaphylactic) reactions to penicillins
• even then, each generation of cephalosporin has lower chance of cross-reactivity
• NOTE: bactrim doesn’t work on group b strep

Question 7

How should one treat a group a strep infection?

Answer 7

Strep pyogenes isolates are universally susceptible to penicillins and beta-lactamases

Question 8

Should one empirically treat a staph aureus infection with penicillins?

Answer 8

No. Staph aureus often has an acquired mecA resistance gene, which encodes an altered pennicillin binding protein. Thus, penicillins (and related, similar beta lactams) won’t work.

• MRSA = staph aureus strains with the mecA gene
• NOTE: in susceptibility testing, oxacillin is used to predict methicillin resistance, so it’s really specifically oxacillin-resistant staph aureus

Question 9

What bacterial organisms are most associated with conjunctivitis?

Answer 9

BIG THREE:
Staph aureus
Strep pneumo
Haemophilus aegyptius (note, NOT influenzae)
OTHER, LESS COMMON
Neisseria gonorrhoeae
Pseudomonas aeruginosa
Francisella tularensis (again, rare and bioterorrism agent)
Chlamydia trachomatis