Clinical manifestations and bacteriological features of culture-proven Gram-negative bacterial arthritis

Background/Purpose: To investigate the clinical manifestations and bacteriological features of culture-proven, Gram-negative bacterial arthritis. Methods: This study was conducted at the Chi Mei Medical Center, a 1300-bed teaching hospital located in southern Taiwan. Patients with synovial fluid cultures positive for Gram-negative bacilli (GNB) during the period January 2009 to May 2014 were identified from the hospital's computerized microbiology database. Results: During the study period, a total of 48 patients with culture-confirmed, GNB septic arthritis were identified. In the majority of patients (n Z 33, 68.8%), the knee was the most commonly involved joint. The most common causative pathogen was Pseudomonas spp. (n Z 16, 33.3%), followed by Escherichia coli (n Z 13, 28.1%). Among the 29 clinical isolates of Enterobacteriaceae, eight (27.6%) were resistant to ceftriaxone and six (20.7%) were resistant to cefpirome. Three E. coli isolates and three Klebsiella pneumoniae isolates were extended-spectrum beta-lactamase producers (n Z 6, 20.7%). Among the nonfermenting GNB (NFGNB), 21.1% were resistant to ceftazidime, 21.1% were resistant to ciprofloxacin, 26.3% were resistant to piperacillin-tazobactam, and 15.8% were resistant to imipenem. The overall mortality rate was 10.4%, and the significant risk factors for death were concomitant bacteremia [odds ratio (OR): 14.6, 95% confidence interval (CI): 1.9-115.2, p Z 0.011] and liver cirrhosis (OR: 20.0, 95% CI: 2.4-169.9, p Z 0.006). Conclusion: Approximately 25% of cases of septic arthritis were due to GNB and resistance to commonly used antimicrobial agents was common. Liver cirrhosis and concomitant bacteremia were significant risk factors for death. Copyright | 2015, Taiwan Society of Microbiology.