Intervertebral discitis caused by nontypeable Haemophilus influenzae in an adult: Case report

Abstract

INTRODUCTION: Haemophilus influenzae is a common cause of bacterial meningitis in children and can cause upper respiratory tract infections in adults, but has yet to be reported solely involving intervertebral discitis. PRESENTATION OF CASE: A 67-year-old builder presenting with fever, myalgia and back pain is found to have intervertebral discitis (confirmed on MRI) caused by H. influenzae (identified on blood cultures). DISCUSSION: A nontypeable form of H. influenzae has not been reported causing discitis. We describe a case in a relatively fit individual who was treated successfully with antimicrobial treatment. A preceding upper respiratory tract infection is the presumed source of infection, predisposed by long-term low-dose steroid therapy. CONCLUSION: H. influenzae is a rare, but treatable cause of discitis.

1. Introduction

Haemophilus influenzae is the most common cause of bacterial meningitis in children, and causes otitis media, epiglottitis and upper respiratory tract infections in older people, yet it is infrequently reported causing disease elsewhere. Vertebral osteomyelitis due to H. influenzae is uncommon, and to our knowledge, only seven other cases have been reported. None solely involve the intervertebral discs, and only one of the previous seven cases was caused by a nontypeable strain.⁷ We describe a case in a relatively fit individual who was treated successfully with antimicrobial treatment. A preceding upper respiratory tract infection is the presumed source of infection, predisposed by long-term low-dose steroid therapy.

2. Presentation of case

A 67-year-old builder was admitted following a two-week history of nausea, vomiting, lethargy, fever and rigors unresponsive to Oseltamivir. In the last three days he had developed a painful right shoulder, with no history of trauma and lower backache. He had no respiratory or abdominal symptoms and no recent dental procedures. His past medical history included gastritis, hypertension, nodular prurigo requiring long-term low-dose steroid therapy and a Hartman's procedure with subsequent reversal for ulcerative colitis in 1992.

Vital signs were temperature 38.3 °C, pulse rate 120/min, respirations 20 breaths/min and BP150/95 mmHg. Cardiac, respiratory, abdominal and oral examination was normal. His extremities were neurologically intact, power 5/5 bilaterally (MRC scale) and sensation intact, but his right shoulder had globally reduced range of movement with joint line tenderness. Palpation of the back revealed exquisite pinpoint tenderness at the L4/5 intervertebral disc and decreased lumbar flexion due to pain.

WBC count was 28.3 × 10⁹/L with 88% neutrophils, hemoglobin 15.1 g/dL, urea 17.4 mmol/L, creatinine 167 mmol/L, liver function tests normal and C-reactive protein 510 mmol/L. Aerobic and anaerobic blood cultures taken on admission identified H. influenzae bacteraemia. Subsequent serotyping proved the strain to be nontypeable, sensitive to ceftriaxone. Right shoulder septic arthritis was excluded after a negative joint aspiration (needle position confirmed under image intensifier) and normal plain radiograph (Fig. 1). Transthoracic echocardiogram did not identify any vegetation or thrombi. Magnetic resonance imaging (MRI) of his brain, shoulder and lumbar region showed inflammation of the L4/5 disc, consistent with a diagnosis of intervertebral discitis (see Figs. 2 and 3).

Fig. 1.

AP radiograph showing normal anatomy of the right shoulder.

Fig. 2.

Sagittal, T2-weighted MR image showing increased signal intensity in the L4/L5 disc, consistent with discitis.

Fig. 3.

Transverse, post-contrast, T2-weighted MR image obtained at the level of the L4/5 intervertebral space showing enhanced tissue in the center of the disc.

His H. influenzae discitis was treated for 6 weeks with IV antibiotics (co-amoxiclav, then ceftriaxone once sensitivities were identified), then a further 6 weeks with oral antibiotics. CRP and ESR at presentation were 510 and 17 respectively, but normalized at twelve weeks with resolution of the back pain.

3. Discussion

This case is atypical for a number of reasons. Firstly, the presentation is unusual; given the main presenting symptom was shoulder pain with systemic features of infection but no history of weight loss. Back pain only developed after admission and commencement of intravenous antibiotic therapy. Secondly, the organism isolated is an unusual form of an unlikely organism, nontypeable H. influenzae. This organism commonly causes infections in children, but is less likely in adults.³ It is a fastidious non-motile Gram-negative coccobacillus that is part of the normal respiratory tract, conjunctiva and genitourinary flora. The patient's preceding upper respiratory tract infection is the presumed source of infection leading to a bacteraemia and resultant myositis and discitis. Thirdly, the site of infection for this particular serotype of Haemophilus has never previously been described and even vertebral osteomyelitis with this organism is exceedingly rare (the authors identified only seven case reports,^1,3,6,8 and only one of these was nontypeable⁷). In these patients, many have underlying diseases including alcoholism, cirrhosis and diabetes mellitus.^1,5 It is likely, however, that the long-term steroid intake contributed to the etiology of this case.

Recent dental procedures are a likely causative factor, but no association exists for the published case reports² as with our case. Other subspecies (Haemophilus aphrophilus) have also been identified as the causative organism of vertebral osteomyelitis⁴ and discitis.^2,5 Of the four cases of discitis caused by H. aphrophilus, two were at the L4/5 level, one at T11/12 and one at C4-7.⁵ Diagnosis was most commonly made through clinical history and MRI findings, as in this case, although ideally, tissue biopsy from the disc should be obtained before commencing empirical treatment to confirm the diagnosis. H. influenzae is notoriously difficult to culture from sites other than the respiratory tract, particularly after antimicrobial therapy has been initiated. The decision not to perform a vertebral disc biopsy in this case was made as the patient had already received 24 h of antibiotics, was reluctant to undergo another procedure and demonstrated a quick clinical response.

H. influenzae is more virulent when encapsulated in polysaccharide, as this protects the organism from phagocytic activity. Serological typing differentiates organisms by the capsular antigens they express. Nontypeable strains are not encapsulated, but are considered more invasive and were found to be responsible in 64% of Haemophilus soft tissue infections in adults.⁹

Sensitivity to antibiotics differs widely for these organisms, our isolate was found to be sensitive to ceftriaxone, vancomycin and ciprofloxacin. Duration of antibiotic treatment differed in the case reports from 4 to 27 weeks, with a mean of 10 weeks.⁵ Our case was treated for a total of 12 weeks without recurrence or complications at 6 months.

4. Conclusion

Nontypeable H. influenzae is a rare, but treatable cause of discitis. Diagnosis should be made from clinical history, examination findings, positive cultures and imaging using MRI where possible. Ideally, tissue biopsy from the disc should be obtained before commencing empirical treatment if the clinical situation allows. Treatment duration should be dictated by clinical and biochemical response. The authors would advocate ten to twelve weeks unless contraindicated.

Conflict of interest

The authors wish to declare there are no conflicts of interest in the production of this case report.

Funding

This work did not receive any financial support.

Ethical approval

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Authors’ contribution

R. Boulton, was directly involved in the treatment of the case, obtained consent for publication, obtained the relevant data and produced the report in conjunction with the second author. A. Swayamprakasam assisted in the literature review and write up. M. Raza was responsible for the overall content of the article, including review of the initial report and subsequent modifications. He also guided the other authors in relevant literature.