Risk factors for gram-negative bacterial surgical site infection: do allergies to antibiotics increase risk?

OBJECTIVE

To determine the relationship between inadequate antimicrobial prophylaxis and development of gram-negative bacterial (GNB) surgical site infection (SSI).

DESIGN

Retrospective case-control study.

SETTING

A 369-bed acute care community hospital in Durham, North Carolina.

PATIENTS: Case patients were defined as patients who developed a GNB SSI after undergoing a surgical procedure during the period from January 1, 1998, through January 1, 2007. Control patients were uninfected patients who underwent surgery during the same study period and were matched to case patients by surgeon and type of procedure. Both patient groups were selected on the basis of prospectively collected data on patients who underwent surgery.

METHODS

Patient data were collected from patient medical records. Multivariable analysis was performed using logistic regression with backward selection, to identify variables independently associated with GNB SSI.

RESULTS

Case patients were similar to control patients with respect to demographics and comorbid conditions, but were older (P = .04), more obese (P = .03), and more likely to have diabetes mellitus (P = .03). Inappropriate timing of antimicrobial prophylaxis was the predominant reason that prophylaxis was deemed inadequate for both patient groups (59.1% of case patients vs 64.0% of control patients; P = .56). Case patients who had a history of allergic reactions to antimicrobial prophylaxis were significantly less likely to receive antimicrobial prophylaxis in a timely manner (P = .03). Variables independently associated with GNB SSI in multivariable analysis included urinary catheterization before surgery (odds ratio [OR], 3.74 [95% confidence interval {CI}, 1.11-12.62), diabetes mellitus (OR, 2.25 [95% CI, 1.02-4.94]), and an American Society of Anesthesiologists score greater than 2 (OR, 2.14 [95% CI, 1.13-4.06]).

CONCLUSIONS

A beta-lactam allergy was not associated with increased risk for GNB SSI. Further studies, using patient data from larger hospital databases, are needed to examine the relationship between use of urinary catheter before surgery and risk of GNB SSI.