[Clinical characteristics and prognosis of cultured negative pyogenic spondylitis]

There are limited data describing the clinical characteristics and prognosis of culture negative pyogenic spondylitis. The aim of this study was to investigate the treatment, prognosis and clinical characteristics of culture negative pyogenic spondylitis.

A retrospective study reviewed 74 patients who were diagnosed with spondylitis in Peking University First Hospital from January 2010 to December 2015. A total of 27 patients suffered from pyogenic spondylitis. According to the pathogenic culture results, the patients were divided into two groups: culture negative group and culture positive group. The clinical characteristics and treatment outcomes between the two groups were compared.

The elder were more vulnerable to pyogenic spondylitis, and of the 27 patients, 12 patients were female and 15 male. All patients had no history of administration of antibiotics prior to obtaining culture samples. A causative germ was identified in 14/27 patients (51.9%) with Staphylococcus aureus being the most common pathogen. There was no significant difference between the two groups in the patient's age, gender, visual analogue score (VAS), predisposing factor, clinical symptom, sign and spinal segment (P>0.05). Erythrocyte sedimentation rate (ESR) (P=0.056) and C-reactive protein (CRP) (P=0.040) of culture negative group were lower in contrast to culture positive group. The incidence of vertebral abscess in culture negative group was higher than in culture positive group (P=0.046). After treatment, ESR dropped almost equally in both groups, and CRP dropped faster in the culture positive group (P=0.192). At last, there was no significant difference between the two groups in hospital stay, pain relief, open debridement operation rate, and recurrence rate of infection.

ESR and CRP of the culture negative patient were lower than those of the culture positive patient, and the incidence rate of paravertebral abscess was higher than that of the culture positive patient. After administration of antibiotics, there was no significant difference between the two groups in duration of antibiotics, open debridement operation rate and recurrence rate of infection. So, culture negative may not necessarily be a negative prognostic factor for pyogenic spondylitis. However, we should watch out for the drug resistant bacteria or double infection, due to the long term use of wide-spectrum antibiotic in culture negative patients.