Brain abscess due to Haemophilus aphrophilus: case report

Haemophilus aphrophilus and Eikenella corrodens Coinfection of Brain: An Unusual Case from China

Background

The HACEK group comprises Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae, are Gram-negative bacteria that are slow-growing and fastidious. These organisms are common causes of culture-negative endocarditis. However, brain abscesses caused by Haemophilus aphrophilus and E. corrodens have been rarely reported. The case we describe, which was promptly identified and successfully treated, will be meaningful for the diagnosis and treatment of such infectious diseases.

Case Presentation

Herein, we report a case of brain abscess in a young man who was infected with Haemophilus aphrophilus and E. corrodens. The patient was admitted to the hospital with sudden onset of vomiting, coma, and fever. Magnetic resonance imaging (MRI) of the brain and cerebrospinal fluid cell counts suggested cerebral abscess, he underwent drainage of the abscess and empirical antimicrobial therapy of meropenem (2 g every 8 hours) and linezolid (0.6 g every 12 hours) for more than 10 days without significant improvement. Metagenomic next-generation sequencing (mNGS) of drainage fluid and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) detection for isolated bacteria from samples suggested the presence of H. aphrophilus and E. corrodens. After 7 weeks of ceftriaxone (2 g every 12 hours) and meropenem (2 g every 8 hours) intravenously, the patient was discharged with a normal temperature and brain MRI showed improvement of the lesion.

Conclusion

Similar cases reported in previous studies were always associated with bacterial blood dissemination after dental surgery or myocarditis; however, the patient in our case had no any associated risk factors. As far as we know, this is the only case of central nervous system infection caused by H. aphrophilus and E. corrodens that has utilized combined mNGS and MALDI-TOF MS in the diagnosis.

An unusual case of multiple hepatic and pulmonary abscesses caused by Aggregatibacter aphrophilus in a young man: a case report

Background

Aggregatibacter aphrophilus, formerly known as Haemophilus aphrophilus, belongs to the HACEK organisms, a group of pathogens classically associated with infectious endocarditis. A. aphrophilus is a rarely found pathogen, though abscess formation in various organs has been described, typically due to spread from an infected heart valve. Here we describe the unusual case of multiple hepatic abscesses caused by A. aphrophilus.

Case presentation

A 33-year-old Caucasian man presented at our hospital with fever and malaise, elevated inflammatory markers, and liver enzymes. Imaging was compatible with multiple liver and pulmonary abscesses, without evidence of endocarditis. Cultures of blood and liver abscess material remained without growth. Polymerase chain reaction finally revealed Aggregatibacter aphrophilus in the liver tissue. The patient recovered fully within 6 weeks of doxycycline treatment.

Conclusions

There are only a few case descriptions of liver abscesses caused by A. aphrophilus. As a ubiquitous organism in the gastrointestinal tract, A. aphrophilus may reach the liver via the portal venous system, as well as through hematogenous spread from the oropharynx. HACEK organisms are notoriously difficult to grow on culture, which highlights the diagnostic importance of eubacterial PCR.

Selective medium for the isolation of Haemophilus aphrophilus from the human periodontium and other oral sites and the low proportion of the organism in the oral flora

We developed a medium for the selective recovery of Haemophilus aphrophilus. The medium, designated TSBVF, was composed of 4% tryptic soy agar, 10% heat-inactivated horse serum, 75 micrograms of bacitracin per ml, 5 micrograms of vancomycin per ml, and 50 micrograms of sodium fluoride per ml. TSBVF yielded a threefold higher recovery of oral H. aphrophilus than did chocolate agar with 75 micrograms of bacitracin per ml, which is a medium routinely used to diagnose human Haemophilus infections. H. aphrophilus and the few contaminating organisms on TSBVF were readily distinguished on the basis of colony morphology. The H. aphrophilus isolates exhibited variable fermentation of raffinose and dextrin but otherwise were biochemically similar. In a clinical study, H. aphrophilus was frequently recovered from supragingival plaque and saliva and occasionally from buccal mucosa and the tonsils. It was also isolated from 29 of 56 subgingival sites in 11 of 14 subjects. Its proportion of the subgingival microflora averaged 0.13% for healthy periodontal sites, 0.05% for adult periodontitis lesions, and 0.03% for localized juvenile periodontitis lesions. We concluded that H. aphrophilus is an indigenous bacterium of the human oral cavity. It occurs in low proportions in subgingival plaque and plays no apparent role in advanced periodontal disease in humans.