Outbreak of surgical wound infections associated with total hip arthroplasty.

Objectives: Describe an outbreak of surgical wound infections associated with total hip arthroplasty; identify risk factors for surgical wound infection during the pre-outbreak and outbreak periods.
Setting: A 100-bed hospital. From May 1 to September 30, 1988, 7 of 15 patients who underwent total hip arthroplasty developed surgical wound infections from Staphylococcus aureus (5), Enterobacter cloacae (1), beta-hemolytic streptococci (1), enterococci (1), coagulase-negative staphylococci (1), and Escherichia coli (1) (attack rate = 46.7%).
Design: Retrospective cohort studies comparing surgical wound infection rates by patient- and procedure-related risk factors during the pre-outbreak and outbreak periods were conducted. Drop plate quantitative air culturing was conducted in 10 consecutive total hip arthroplasties in the subsequent 6 months.
Results: Rates of surgical wound infection were surgically higher for arthroplasties in which no intraoperative prophylactic antimicrobials were given (44% versus 8%, relative risk [RR] = 5.4, p = .01), or in which the posterior approach (20% versus 3%, RR = 6.7, p = .04) or a specific prosthesis (39% versus 5%, RR = 6.3, p = 0.01) was used. The surgical wound infection rate was highest when one circulating nurse, Nurse A, assisted (47% versus 4%, RR = 12.8, p less than .001). Logistic regression analysis identified use of the posterior approach (RR = 1.8, p = .04) and Nurse A's participation (RR = 5.0, p less than .001) as independent risk factors for surgical wound infection. Interviews of the nursing supervisor indicated that Nurse A had recurrent dermatitis on her hands. During 6 months following Nurse A's reassignment, the rate declined significantly (from 7/15 to 0/10, p = .01). Drop plate culturing yielded 2 to 10 colonies per plate of organisms that did not match outbreak organisms.
Conclusions: Outbreaks associated with personnel generally involve only 1 species. In this outbreak, Nurse A (possibly because of her dermatitis), technique, the posterior approach, and/or other undetermined factors were the primary predictors of surgical wound infection.