Cat bite wounds: risk factors for infection.

STUDY OBJECTIVE: In the last ten years, many emergency medicine specialists have studied animal bite wounds. The majority of these studies have addressed the controversies of prescribing prophylactic antibiotics or suturing wounds. This study was undertaken to determine risk factors for cat bite wound infections.

DESIGN: Prospective survey.

SETTING: Community hospital emergency medicine residency program.

TYPE OF PARTICIPANTS: One hundred eighty-six consecutive patients with 216 cat bite/scratch wounds over a two-year period.

INTERVENTIONS: A standardized wound cleaning protocol with debridement and suturing, if indicated, was used. Variables analyzed included patient age and gender; wound age, type, number, location, and depth; prehospital therapy; emergency department therapy; and antibiotics used.

RESULTS: The mean patient age was 19.5 +/- 15.9 years. The mean time interval from wounding to ED treatment was 10.2 +/- 39.2 hours. By anatomical sites, there were 33 (15%) head/neck, 48 (22%) arm, 97 (45%) hand, ten (5%) truncal, and 28 (13%) lower extremity wounds. By wound type, there were 122 (56%) punctures, 54 (25%) abrasions, 37 (17%) lacerations, and two (1%) avulsions. One hundred fifty (71%) of the wounds were partial thickness, and 62 (29%) were full thickness. Twenty-four (12.9%) of the patients had clinical evidence of wound infection on arrival to the ED. Five (2.7%) developed clinical evidence of infection despite ED treatment. None of the 14 (7.5%) patients with only "claw" injuries developed infection. The overall patient infection rate for those with cat "bites" was 15.6%. Factors associated with wound infections included older age (P less than .001), longer time intervals until ED treatment (P less than .0001), wounds inflicted by "pet" cats (P = .001), attempting wound care at home (P = .0004), having a more severe wound (P = .01), and having a deeper wound (P = .0001). Data from 148 patients who had only "bite" wounds and did not have clinical evidence of infection on initial presentation to the ED also were analyzed for wound infection risk factors. Wound infections were more likely to develop in patients with lower extremity wounds who did not receive prophylactic oral antibiotics (P = .071) and those with puncture wounds who did not receive prophylactic oral antibiotics (P = .085).

CONCLUSION: In this study, wound type and wound depth were the most important factors in determining the likelihood of developing wound infection regardless of whether the patient was prescribed prophylactic oral antibiotics.