Haemophilus spp.

Haemophilus spp.

IMPORTANT SPECIES
• H. influenzae
• H. ducreyi
H. influenzae
• Gram-negative coccobacilli/short bacilli
• Some strains capsulated
• Six serotypes (a-f) on the basis of capsular antigens
• Type b (Hib)- the main pathogen
Haemophilus influenzae
Growth Requirements
• Growth improved in CO2
• Grow on enriched media (chocolate agar)
• Needs X factor (haematin) & V factor (NAD)
° Both are present in RBCs and are released on heating (chocolate agar)
° V- factor can be produced by yeast & S. aureus
° H. influenzae can grow on blood agar in vicinity of colony of S. aureus (satellitism)

PATHOGENESIS
Type b (capsulated)
• Is primary pathogen
• IgA protease - degrades secretory IgA and help attachment to respiratory mucosa
• Capsule - antiphagocytic
• Endotoxins
DISEASES
Common in age group 2 months - 2 years
• Meningitis
• Acute epiglotitis
• Acute otitis media
• Pneumonia
LAB IDENTIFICATION
• Specimens : CSF, blood, sputum, ear swab
• Direct Gram-smear of CSF sediment
• Culture on chocolate agar (X & V factors)
• Satellitism with colonies of S. aureus
• Direct detection of type b capsular antigen in CSF by latex agglutination
TREATMENT
• Ceftriaxone OR Ciprofloxacin
• 20-30% resistant to penicillin due to B-lactamase
PREVENTION
• Vaccination (2-15 months of age)
a) Unconjugated purified PRP (polyribitol phosphate) vaccine
b) Conjugated vaccine containing PRP with diphtheria & tetanus toxoids
? Incidence of Hib meningitis has been greatly reduced due to vaccination
• Chemoprophylaxis
° Rifampicin : to close contacts as it is secreted in saliva.
° It decreases respiratory carriage & transmission
Haemophilus ducreyi
• Gram-negative coccobacilli
• Cultured on chocolate agar
• Requires only X factor
• Causes Chancroid
° A sexually transmitted disease with soft ulcers on external genitalia with local lymphadenitis (bubo)
• Treatment:
° Ceftriaxone or ciprofloxacin
Gardenerella vaginalis
• Gram-negative coccobacilli
• Formerly called Haemophilus vaginalis
• Found in small numbers in vaginal secretions of 50% of normal women
Disease : Bacterial Vaginosis
• Malodourous vaginal discharge
Lab Diagnosis
• Gram-smear of vaginal discharge
° Clue cells (epithelial cells covered with bacteria)
Treatment : Metronidazole