Overcoming diagnostic pitfalls of Haemophilus influenzae type b frontal osteomyelitis: a systematic review plus index-case analysis in the post-vaccination era

Invasive Haemophilus influenzae type b (Hib) infections have become exceedingly rare in adults following universal childhood vaccination. This decline poses a diagnostic challenge, as clinical suspicion and laboratory protocols may not be optimized for its detection. To systematically review adult frontal osteomyelitis caused by H. influenzae in the post-vaccination era, with an emphasis on the diagnostic challenges and therapeutic implications of an index Hib case. We conducted a systematic literature review in accordance with the PRISMA 2020 guidelines, searching PubMed, Embase and Web of Science from database inception to February 28, 2026. A contemporary index case of an elderly man with Hib frontal osteomyelitis was analyzed in depth alongside retrieved historical cases. Descriptive and comparative synthesis was performed for the collected data. Eight cases were analyzed in total. Seven historical cases (100% non-type b) all required surgical debridement. The index case was the first reported Hib-induced frontal osteomyelitis in an elderly adult in two decades. Initial culture of abscess fluid using only blood and MacConkey agars failed, despite a positive Gram stain. Diagnosis was achieved only after bedside inoculation that included chocolate agar, yielding a β-lactamase-negative Hib strain susceptible to amoxicillin/clavulanate. Consequently, the patient was successfully cured with targeted antibiotic therapy alone, without surgical intervention, and has remained asymptomatic for more than 4 years to date. This systematic review characterizes invasive Hib disease among vulnerable adults in the post-vaccination era based on a rare index case successfully managed without surgical debridement. The findings reinforce that standard culture protocols including chocolate agar should be followed for Gram-stain-positive sterile-site specimens to recover fastidious organisms. Observations regarding non-surgical antibiotic-only management remain hypothesis-generating and require further validation.