LECTURE - Haemophilus influenzae

Question 1

H. influenzae characteristics

Answer 1

• gram neg coccobacilli
• non-motile
• requires both X and V factors
  > X = protoporphyrin precursors
  > NAD (nicotinamide adenine dinucleotide) or related
  both can be released from erythrocytes fmo gentle heating
• growth on choc agar
• satellitism with hemolytic S. aureus

Question 2

two main classifications for H. influenzae

Answer 2

• nonencapsulated or non-typable (colonize resp tract)
• encapsulated = polyribitol ribose phosphate (PRP); very effective conjugate vaccine! bc clonal and not genetically diverse like non-typable

Question 3

epiglottitis

Answer 3

• aka supraglottitis
• H. influenzae infects = false chords around epiglottis swell; subglottic tissue will swell and close off = asphyxiating person
  = starts with barking cough (like Croup)
• can progress quickly and be very serious
• vaccine protects against this

Question 4

diagnosis of invasive Hib

Answer 4

• culture of blood and CSF
• most meningitis cases show typical organisms in gram stains of CSF (70%); but more reliable is looking for PRP from CSF
  > latex or co-agglutination of CSF to detect PRP free in CSF or concentrated urine = RAPID

Question 5

T or F. diagnosis of nontypeable H. influenzae is difficult and rarely done

Answer 5

T! but one exception = H. influenzae biogroup aegyptius

• causes purulent contagious conjunctivitis (hot climates)
• Brazilian purpuric fever
• non-encapsulated
• Kochs-Weeks bacillus
• longer, thinner bacillus

Question 6

three main causes of bacterial meningitis

Answer 6

S. pneumoniae
N. meningitidis
H. influenzae

Question 7

antibiotics for invasive disease caused by H. influenzae

Answer 7

third gen cephalosporins like ceftriaxone

Question 8

profound impact of Hib vaccine

Answer 8

Hi non-b invasive disease

- CONCERN IN CHILDREN AND ELDERLY

Question 9

normal inhabitamts of URT and mouth (other Haemophilus sp)

Answer 9

• H. parainfluenzae
• H. aphrophilus
• H. paraphrophilus
• H. haemolyticus
• H. parahaemolyticus
  > opportunistic
  > cause serious diseases esp. endocarditis after dental procedures
  > arterial embolism
  > treatment similar to H. influenzae
  > no antibiotic resistance

Question 10

genetically dissimilar to Haemophilus

Answer 10

H. ducreyi

> gram stain and biochem feature are the same though

Question 11

H. ducreyi

Answer 11

• more common in men than women
• outbreaks in developed countries; more endemic in developing countries
• drug use and sex workers
• comparable to syphilis but this is hurtful; syphilis chancres are harder and do not hurt
• lesions can provide entryway (like herpes) for HIV; painful = soft chancres
• not limited just to STD - can be lesions in arm, etc.