HAEMOPHILUS, BORDETELLA and LEGIONELLA

I. HAEMOPHILUS

A. MORPHOLOGY--Gram negative, non-motile, non-spore forming "bacillus" (coccoid-bacillus to pleiomorphic).

B. CULTURE--Chocolate agar; fastidious
H. influenza grow much larger colonies around Staph colonies (satellitism)

H. influenza requires two factors:

a heat-labile V factor [nicotinic acid dinucleotide (NAD) or NAD Phosphate (NADP)
a heat-stable X factor - hematin. Factor V is required on chocolate agar
H. parainfluenza requires only V factor for growth on chocolate agar. H. influenza requires both. requires only V factor for growth on chocolate agar. H. influenza requires both.

C. ANTIGENIC STRUCTURE -- 6 encapsulated types; Type b is the most important human pathogen

D. PATHOGENESIS -- NO EXOTOXIN

Non-encapsulated forms are normal flora
Encapsulated forms cause sinusitis, otitis and, in young children, meningitis.

E. DIAGNOSIS -- Clinical specimens include nasopharyngeal swab, pus, blood, and spinal fluids.
TESTING by staining and culture on chocolate agar

F. TREATMENT--MORTALITY MAY BE UP TO 90%

Penicillin, Cefotaxime (a third generation cephalosporin)
Penicillin-resistant and chloramphenicol-resistant strains reported

A vaccine has been formulated from H. influenza capsular polysaccharide; greater than 90% efficacy in protecting infants from Hib (doses at 2 and 4 months). Even a single dose achieves a high protective efficacy. This vaccine is now routinely administered to newborns.

II. BORDETELLA

A. INTRODUCTION -- B. pertussis is the etiologic agent for pertussis or "whooping cough".

B. MORPHOLOGY -- Gram-negative coccobacilli with capsule; Bipolar metachromatic granules

C. CULTURE -- Bordet-Gengou agar; growth requires 3-7 days

D. PATHOGENESIS -- First colonization is upper respiratory (carriers); attachment via capsular material to mucosal surfaces

1. Fever and cough

2. Toxemic stage follows with characteristic inspiratory gasp (whoop)

3. Toxemic stage results from the Pertussis Toxin composed of a- and b-chains

4. The Pertussis Toxin is an adenylate cyclase activator

E. TREATMENT

1. Erythromycin

2. Prevention involves vaccination (DPT routinely administered to preschool age children in the U.S.)

3. The vaccine is of the killed, whole cell type

III. LEGIONELLAE

A. INTRODUCTION--First reported in 1976 with an outbreak of characteristic respiratory disease; was traced to the air conditioning system at a Philadelphia American Legion convention. Retrospective epidemiological studies have identified Legionella as the causative organism for pneumonias dating back to 1947 (stored serum samples). Twenty-two different species; primary human pathogen is L. pneumophila.

B. MORPHOLOGY--Gram-negative rods; Difficult to stain from cultures Should be stained with basic fuchsin instead of safranin as the counterstain in the Gram stain procedure.

C. CULTURE--complex media required; Slow growth (up to 3 days); "Unusual" growth requirements include 90% humidity, pH 6.9. Colonies may be pigmented, but can also lose colors.

D. ENZYMES -- catalase, oxidase positive (esp. L. pneumophila)
-gelatinase and beta-lactamase positive
-DNAase and RNAase positive
-hemolysin and cytotoxin are produced

E. PATHOGENESIS -- common organism (warm, moist environments)
-infects suppressed individuals (notably older men who smoke, have chronic bronchitis, emphysema)
-causes Legionnaires' disease (pneumonia, fever, chills, malaise, nonproductive cough; -X-rays reveal multilobar consolidation).
-Also causes Pontiac fever (fever, chills, myalgia, malaise, and headache; symtoms increase over 6-12 hours; dizziness, photophobia, neck stiffness, confusion)

F. TREATMENT--erythromycin

E-mail Dr. Johnson: johnsomt (at) iupui.edu
for comments or suggestions.