Haemophilus and Other Fastidious Flashcards
Pasteurellaceae (Pasteurella and Haemophilus)
- gram-negative coccobacilli
- non-motile, aerobic to facultative
- reduce nitrate to nitrite
- oxidase + and catalase +
- obligate parasites of mucous membranes
- require X and V factor
- grow on chocolate agar
- part of normal flora of upper respiratory tract
Haemophilus
Haemophilus means _______
blood loving
X factor
hemin (hematin)
V factor
nicotinamide-adenine dinucleotide (NAD)
only require V factor
para- Haemophilus species
Hemolysis on 5% horse or rabbit blood agar
- H. hemolyticus and H. ducreyi
- can’t use SBA because it doesn’t have V factor
Growth patterns
- satellitism around S. aureus (and species that release V factor)
- exceptions: H. aphrophilus and H. ducreyi
H. influenzae
- often a secondary infection (was in a pandemic)
- can test for beta-lactamase
H. influenzae (virulence factors)
- capsule (A-F types)
- IgA protease
- outer membrane proteins and lipopolysaccharide (LPS)
- adherence (pili)
H. influenzae capsule
- antiphagocytic molecules (ribose, ribitol, and phosphate)
- nontypable strains cause localized infections (pneumonia, otitis media, sinusitis)
Haemophilus influenzae serotype b (Hib)
- primarily in children
- bacteremia can spread to tissues
- # 1 cause of meningitis in unvaccinated children
Clinical disease of Hib
- meningitis (children under 6)
- epiglottitis (can cause airway obstruction)
- bacterial tracheitis
- cellulitis, pharyngitis, pneumonia
Non-encapsulated H. influenzae (diseases)
otitis media, bronchitis, sinusitis, pneumonia
H. aegyptius is the causative agent of _________
pinkeye (conjunctivitis)
H. aegyptius (clinical infections)
- conjunctivitis
- Brazilian purpuric fever (BPF): has a high mortality rate
H. ducreyi
- sexually transmitted infection
- chancroid (soft chancre)
- incubation up to 14 days
- painful legion, enlarged lymph nodes, buboes
H. parainfluenzae (clinical infections)
endocarditis
H. aphrophilus/Aggregatibacter aphrophilus (clinical infections)
bite wound infections, endocarditis
Culturing Haemophilus
- must plate immediately, they die rapidly
- BAP for those that don’t require V factor
- DON’T GROW ON MAC
- transluscent, moist, smooth colonies
Culturing H. influenzae
chocolate agar with bacitracin (to inhibit other respiratory flora)
Culturing H. ducreyi
- extremely fastidious (7 days to grow)
- “school of fish” morphology on gram stain
Lab ID of Haemophilus
- place colonies in nutrient broth, then streak Mueller-Hinton agar plate, use X and V strips and incubate
- Quad plate to ID factors needed (X, V, X & V, horse blood)
Porphyrin test
- differentiates species that require X factor
- Positive: organism converts delta-aminolevulinic acid to porphyrin (intermediate of X factor)
- positive result means organism doesn’t need X factor
- positive result on Wood lamp fluoresces