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. The vaccine has pretty much eradicated b disease.

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


H. influenzae: otitis media, sinusitis, epiglottitis, pneumonia, meningitis (especially 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.

Curious Cases

Relevant links to my Medscape blog


Triad, Pentad, or Septad

Last update: 05/05/18