Haemophilus parainfluenzae Septic Arthritis: Report of a Case and Review of the Literature

Dear Editor:

We describe the first case of septic arthritis caused by Haemophilus parainfluenzae reported in Spain.

An otherwise healthy 12-year-old boy was seen in our Emergency Department with swelling and pain in his right knee along with limp for the past day. There was no history of trauma or fever. On physical examination the joint was swollen, tender and with a limited range of motion. Blood inflammatory markers were minimally altered. Arthrocentesis revealed a total leukocyte count of 38,750/mm³ with 20% neutrophils and 80% monocytes. No bacteria were observed on the Gram stain. Aliquots of joint fluid were directly plated onto solid media and inoculated into blood culture bottles. The patient was admitted with a provisional diagnosis of synovitis and suspected possible osteomyelitis of the distal femur. On day two, magnetic resonance imaging showed no involvement of the adjacent bones. However, the blood culture bottle inoculated with the joint specimen was positive for Gram-negative coccobacilli. Consequently, the patient underwent arthroscopic drainage, and intravenous cefotaxime (1 g/8 hours) was started. When this positive blood culture bottle was subcultured, the microorganism grew on chocolate agar, but not on conventional 5% sheep blood agar. It was later identified as Haemophilus parainfluenzae on the basis of its growth requirement for V-factor (but not for X-factor) and the biochemical characteristics. Bacterial growth on agar chocolate seeded with the joint sample was observed after two days of incubation. The strain did not produce beta-lactamase and was susceptible to a wide range of antibiotics. The patient was successfully treated with 10 days of intravenous cefotaxime followed by three weeks of oral amoxicillin.

Haemophilus parainfluenzae has recently been reported with increasing frequency in a broad spectrum of serious infections.¹ In fact, it is believed that its true prevalence could be underestimated due to its fastidious growth requirements and the lack of use of proper growth media.^2,3 For example, the recovery rate in biliary tract infections was found to be increased in one study in which negative bile specimens by conventional cultures were inoculated into blood culture bottles.² In this context, it is worth mentioning that in our case Haemophilus parainfluenzae was promptly detected in the specimen inoculated into the blood culture bottle. These findings suggest that the enriched liquid medium contained in blood culture bottles may contribute to enhance the recovery of this microorganism. It should be remembered that Kingella kingae, another member of the HACEK group, has become the main etiological agent of osteoarticular infections in young children in settings where this procedure has been systematically employed.⁴

We were able to find 15 reported cases of osteoarticular infections caused by Haemophilus parainfluenzae in the international medical literature.^5–8 Fifty-three percent of these patients were over 65 years of age (range 8 months-95 years). There were 10 cases of septic arthritis with a clear predilection for the knee (50% of the patients). The vertebral column was involved in 4 of the 5 reported patients with osteomyelitis. Although most cases affected patients without underlying conditions or immunosuppression, up to 67% had a history of dental or gastrointestinal procedures, intestinal mucosa damage after chemotherapy, tooth abscess or upper respiratory tract infections.^5–8 This feature indicates that the most common pathway of infection could be an osteoarticular seeding after hematogenous spread facilitated by mucosal rupture, bearing in mind that this pathogen is found among the commensal flora of the oral cavity, pharynx, and digestive and urogenital tracts.⁵ As in systemic infections other than endocarditis caused by other Haemophilus species, patients should be treated with ceftriaxone or cefotaxime until beta-lactamase production is ruled out¹. Most patients who received appropriated antimicrobial therapy, combined with timely surgical treatment when indicated, can be cured without long-term sequelae.⁵