Infectious Disease Compendium



Gram negative coccobacillus. H. aprophilus (now Aggregatibacter aphrophilus), H. ducreyi, H. haemolyticus (Can be confused with H. influenza in the COPD patient but is not a pathogen (PubMed), H. influenzae, H. parahaemolyticus, H. parainfluenzae, H. paraaprophilus, Haemophilus segnis (now Aggregatibacter segnis).

Epidemiologic Risks

Being human, and, for Type b H. influenza, being an unvaccinated human.

H. influenza can be type b, other types (a,c,d,e, f as examples) and untypable.

Kids used to get type b, adults usually get other types or untypable.

H. influenza type a can also cause invasive disease (PubMed) .


H. influenzae: otitis media, sinusitis, epiglottitis, pneumonia, meningitis (espcially children who are not vaccinated). And urethritis (PubMed).

Invasive disease should result in a work-up for antibody deficiencies and other immunodeficiencies (PubMed).

H. ducreyi: chancroid painful, ulcerated, genital ulcers with inguinal adenopathy.  In the developing world it causes chronic skin ulcers in children (PubMed).

H. aprophilus (now Aggregatibacter aphrophilus), parainfluenza and paraaprophilus: endocarditis. Part of any disease where spit is an issue.


H. influenzae: any and all beta lactams (except ampicillin) and quinolones. See specific disease. Type b with increasing resistance to ampicillin.

H. ducreyi: azithromycin 1 g orally in a single dose OR ceftriaxone 250 mg (IM) in a single dose OR ciprofloxacin 500 mg orally twice a day for 3 days OR erythromycin base 500 mg orally three times a day for 7 days (CDC).

H. aprophilus, parainfluenza and paraaprophilus endocarditis: ampicillin +/- gentamicin for four (native valve) to six weeks (prosthetic valve). A third generation cephalosporin OR aztreonam are reasonable alternatives if resistance OR allergies preclude the use of beta lactams.


Increasing resistance to tetracycline and sulfa precludes their use empirically.