Predictive Factors of Cloxacillin Susceptibility in Primary Bacterial Spinal Infection

Abstract

Study DesignPrognostic study.ObjectivesThe objective of this study is to identify predictive factors for cloxacillin susceptibility in spinal infections.MethodsA retrospective analysis was conducted using data from January 1, 1997, to December 31, 2021. The study included patients presenting with back pain and either a positive bacterial culture from the spine or radiological evidence of spinal infection (spondylodiscitis and/or epidural abscess) along with positive bacterial blood culture.ResultsAmong 171 patients (127 males, 44 females), 53.2% had Staphylococcus isolates, with 40.4% showing cloxacillin resistance. Lower globulin levels (<33.5 g/L), recent hospitalization within 90 days, and residence in an old age home predicted gram-positive bacteria with cloxacillin resistance and gram-negative bacteria as causative organisms (P<.05). The 30-day and 1-year all-cause mortality rates were 0% and 8.2%, respectively. Higher red cell distribution width (RDW >16.1%) and Charlson comorbidity index (CCI) scores predicted 1-year all-cause mortality (P<.05). Intensive care unit admission was required for 9.9% of patients.ConclusionsThis study identified predictive factors for spinal infection by gram-positive bacteria with cloxacillin resistance and gram-negative bacteria. Patients with lower globulin levels (<33.5 g/L), recent hospitalization within 90 days, or residency in an old age home upon admission should avoid standalone cloxacillin therapy and consider antibiotics with gram-negative coverage. Higher RDW (>16.1%) and CCI scores were associated with increased 1-year all-cause mortality. These findings contribute to treatment decision-making and improving patient outcomes in spinal infections.

Keywords: infection; spine; spondylodiscitis.

Figure 1.

Flowchart of patient recruitment. 171 patients were included in the final analysis.

Figure 2.

Causative bacteria breakdown: majority of the infections were caused by staphylococci. Note: Since multiple bacteria were detected in the polymicrobial spinal infection, the percentages did not add up to a total of 100.

Figure 3.

Distribution of causative bacteria throughout the review period. Note: Most of the patients had incomplete records before 2004 and thus excluded from the study. MSSA, methicillin-sensitive Staphylococcus aureus; MRSA, methicillin-resistant S. aureus.

Figure 4.

ROC curve for cloxacillin resistance (Area Under Curve (AUC) = .59).

Figure 5.

ROC curve for RDW to predict 1-year all-cause mortality (Area Under Curve (AUC) = .67).