What is Haemophilus (H.) bacteria?

From the Guidelines

Haemophilus bacteria are a common cause of infections, and vaccination is the primary method of prevention, particularly for Haemophilus influenzae type b (Hib) which can cause serious invasive diseases. Haemophilus bacteria are gram-negative, facultatively anaerobic coccobacilli that can cause various infections in humans, including otitis media and sinusitis, as noted in a 2021 study published in Leukemia 1. The most clinically significant species is Haemophilus influenzae, which requires factors X (hemin) and V (NAD) for growth.

Key Points

• Haemophilus influenzae type b (Hib) can cause serious invasive diseases including meningitis, epiglottitis, pneumonia, and septicemia, particularly in children under 5 years.
• Treatment typically involves antibiotics such as third-generation cephalosporins or ampicillin (if the strain is susceptible) combined with chloramphenicol in severe cases, as per standard medical practice.
• For less severe infections like otitis media or sinusitis caused by non-typeable H. influenzae, amoxicillin-clavulanate is often effective.
• Prevention is primarily through Hib vaccination, which has dramatically reduced invasive disease incidence, as supported by the 2021 consensus of the European Myeloma Network 1.

Laboratory Diagnosis

Haemophilus bacteria require special culture media containing both X and V factors, such as chocolate agar, for laboratory isolation and identification. Other Haemophilus species like H. parainfluenzae and H. ducreyi can cause endocarditis and chancroid, respectively, requiring specific antibiotic regimens based on susceptibility testing.

Clinical Considerations

It is essential to consider the severity of the infection and the patient's age and underlying health conditions when selecting an antibiotic regimen, and to always prioritize vaccination as the primary method of prevention, as emphasized in the 2021 study 1.

From the FDA Drug Label

Cefotaxime has been shown to be active against most isolates of the following bacteria both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section: Gram-negative bacteria Haemophilus influenzae Haemophilus parainfluenzae

• Cefotaxime is effective against Haemophilus influenzae and Haemophilus parainfluenzae bacteria, as stated in the drug label 2.
• The drug label also mentions that Cefotaxime has activity against Haemophilus influenzae, including ampicillin-resistant strains 2.
• Additionally, Azithromycin has been shown to be active against Haemophilus influenzae and Haemophilus ducreyi 3.

From the Research

Characteristics of Haemophilus influenzae

• Haemophilus influenzae is a small, nonmotile, non-spore-forming bacterium, and a strict parasite of humans found principally in the upper respiratory tract 4
• The production of capsule is of major significance to clinicians since it is an important virulence factor, with six antigenically distinct capsular types, designated a-f 4
• Haemophilus influenzae produces at least two factors that inhibit the ciliary activity of human epithelial cells in vitro, including lipopolysaccharide and a heat-stable glycopeptide 4

Disease Patterns and Diagnosis

• Two contrasting patterns of Haemophilus influenzae disease can be identified: invasive infection (e.g. meningitis, septic arthritis, epiglottitis, and cellulitis) and less serious infections (e.g. otitis media, sinusitis) 4
• A provisional diagnosis of meningitis, epiglottitis, facial cellulitis, or septic arthritis will usually be prompted by the history and clinical findings, with confirmation requiring microbiologic studies 4
• Cultures of blood, CSF and other normally sterile fluids are diagnostic and therefore under the appropriate circumstances mandatory 4

Treatment and Antibiotic Resistance

• Without treatment, infection due to Haemophilus influenzae can be rapidly fatal, particularly by meningitis and epiglottitis 4
• Certain parenteral third generation cephalosporins (e.g. cefotaxime or ceftriaxone) are often used as initial therapy when life-threatening Haemophilus influenzae infection is known or suspected in children beyond the neonatal period 4
• Azithromycin has been shown to be more potent than erythromycin and roxithromycin against Haemophilus influenzae, with a rapid bactericidal effect 5
• Cefotaxime resistance in invasive Haemophilus influenzae isolates is rare, but can occur due to sporadic mutations, such as substitutions in the PBP3 gene 6

Epidemiology and Prevention

• Haemophilus influenzae is a major pathogen in acute otitis media (AOM), particularly in older children and those with recurrent disease 7
• Widespread pneumococcal vaccination has increased the importance of Haemophilus influenzae as a major therapeutic challenge in the treatment of AOM 7
• The prevalence of cefotaxime-resistant H. influenzae in Europe is reported to be low, but systematic studies with a large set of invasive isolates are scarce 6