Haemophilus paraphrophilus brain abscess in a 9-year-old boy: Case report and literature review

© International Journal of Applied Biology 21 Abstract Human diseases due to A. paraphrophilus aren’t usual. The following case report describes the first isolated case of A. paraphrophilus brain abscess in our laboratory. A 9-year-old boy presented to pediatric emergencies for frontal headache, vomiting, blurred vision and left hemiparesis. Radiological diagnosis consists with a frontal abscess. Gram staining of purulent samples showed abundant neutrophils with gram negative bacilli. Culture was made on blood agar, chocolate agar, Chapman’s agar and incubated in 5% CO at 37°C for 24 hours. Positive culture was detected only on chocolate agar. It was monomicrobial with small yellowish non-hemolytic colonies. Gram stain of colonies showed pleomorphic gram-negative coccobacilli. The strain required V factor for growth. The isolated strain was sensitive to all antibiotics tested. The interest of this case is that it shows the emergence of A. paraphrophilus as a causative agent of brain abscesses on pediatric population without associated congenital heart disease. It may also help identifying risk factors of these infections and how to prevent them. ISSN : 2580-2410 eISSN : 2580-2119


Introduction
H. aphrophilus and H. paraphrophilus are now combined as the same species: Aggregatibacter aphrophilus, with the V-factor dependence of H. paraphrophilus being considered as a variable phenotypic characteristic [1]. A. aphrophilus belongs to the HACEK group, fastidious gram-negative bacilli that are found in the human upper respiratory and genitourinary tracts [1]. A. aphrophilus may cause brain abscess and infective endocarditis and has been isolated from various other body sites including peritoneum, pleura, wound and bone [2].

Case Report
A 9-year-old boy was admitted to pediatric emergencies for frontal headache not relieved with painkillers, vomiting and blurred vision. He had no obvious associated conditions except a sinusitis that took place two weeks ago. On admission, he was afebrile with a stable hemodynamic state. Neurological examination showed a Glasgow coma scale score of 13, a supple neck and left hemiparesis. The remaining physical examination was normal. CT with contrast demonstrates a ring-enhancing lesion along with midline shift to the left. Drainage of the abscess was achieved and empiric parenteral antibiotic therapy was initiated with metronidazole (10mg/kg/8h), and ceftriaxone (100mg/kg/j). Other investigations were carried out: ultrasound of liver, chest X-ray and dental examination. These were all negative. Blood tests showed leukocytes 14 x 10 3 / uL with 9,8 x 10 3 /uL neutrophils, hemoglobin 12g/dL and C-reactive protein 2,8 mg/L. Gram staining of purulent samples showed abundant neutrophils with gram negative bacilli. A small volume of pus was inoculated onto blood agar, chocolate agar, Chapman's agar and incubated in 5% CO 2 at 37°C for 24 hours. Positive culture was detected only on chocolate agar. It was monomicrobial with small yellowish non-hemolytic colonies (figure 1). Gram stain of colonies showed pleomorphic gram-negative coccobacilli. The strain required V, but not X factor for growth, it was oxidase positive and catalase negative. Late identification by API NH system revealed Haemophilus paraphrophilus ( Figure 3).
Antimicrobial susceptibility was detected by the disk diffusion test using an inoculum of 0, 5 McFarland on M-H base agar supplemented by 5% horse blood and 20mg/L β-NAD. The isolates were susceptible to all antibiotics tested according to EUCAST breakpoint standards ( Figure 2).
Normalization of WBC counts was obtained by the 10 th postoperative day. After six weeks of intravenous antibiotic therapy, CT scan control showed diminished lesion and neurological manifestations disappeared.

Discussion
Brain abscess is a rare disease in childhood requiring prompt medical and/or surgical treatment [3]. To our knowledge this is the third case report of A. paraphrophilus brain abscess in a child without underlying heart disease.
Bacteria reach the brain through contiguous spread, hematogenous dissemination from a distant focus or through a head trauma (penetrating injury, post-neurosurgery) [4]. Congenital heart disease is the most common underlying condition, and the most common preceding infection is sinusitis [3]. We assume that in the case of our patient, the brain abscess was due to a contiguous spread from the sinusitis that took place 2 weeks earlier.
The most frequently isolated microorganisms from brain abscesses in pediatric population are Viridans streptococci, Staphylococcus aureus and Enterobacteriaceae [5]. A. paraphrophilus has emerged as an important cause of brain abscesses [6].
A. paraphrophilus is a small, pleomorphic Gram-negative coccobacilli, it's slow growing requires enriched culture media and increased carbon dioxide tension [7]. Non motile, facultatively anaerobic with no dependence to X factor but V factor is required for growth [2]. Colonies on chocolate agar are granular, yellowish and opaque [2]. Glucose is fermented, ONPG is hydrolyzed and oxidase is positive [2]. Phenotypic characteristics differentiating A. paraphrophilus from other HACEK group species are shown in Table 1. Fortunately, A. paraphrophilus is sensitive to a wide range of antibiotics [8]. Production of beta-lactamase should be tested, while third-generation cephalosporins should be considered drug of choice [9]. Ciprofloxacin and the newer fluoroquinolones have potent activity against A. paraphrophilus, and can be used as alternatives for penicillin allergic individuals, and for those infected with strains resistant to cephalosporins [10]. Our isolated strain was susceptible to all antibiotics tested according to the EUCAST breakpoint standards [11].  The literature review since 1984 showed only 10 previously reported cases of A. paraphrophilus brain abscess ( Table 2). Two of the 10 cases are children (20%) and six are males (60%). 30% have underlying congenital heart disease while no predisposing factor was identified in two cases. Therapy is based on antibiotics combined with surgical drainage in 80% of cases. The mortality rate is 20%.

Conclusions
A. paraphrophilus is emerging as a causative agent of brain abscesses in pediatric population. Prevention is therefore crucial and involves good dental hygiene and the treatment of any ENT infection.