Bacterial counts in experimental, contaminated crush wounds irrigated withvarious concentrations of cefazolin and penicillin

The objective of this study was to determine if three different concentrati ons of cefazolin and penicillin irrigation solutions reduce quantitative ba cterial counts in experimental crush wounds contaminated with multiple spec ies of bacteria. The design used was a randomized, blinded, experimental an imal study. An animal bite wound model was created by innoculating crushed incisions with three species of bacteria. Four para vertebral incisions ext ending to deep fascia were created in each of twelve anesthetized albino gu inea pigs. Wound edges were clamped with a hemostat for five seconds to cre ate crushed, devitalized tissue within each wound. Wounds were inoculated w ith 0.4 mt of a standard solution of Staphylococcus aureus, Bacterioides fr agilis, and Pasturella multocida and covered. Four hours after inoculation, each wound was scrubbed for 30 seconds with 20% poloxamer 188 and then irr igated with 100 mL of one of four solutions: normal saline solution (contro l); cefazolin (CZ) 2 mg/mL, plus penicillin G (PCN) 200 units/mL (low dose) ; CZ 10 mg/mL, plus PCN 2,000 units/mL (intermediate dose); and CZ 50 mg/mL , plus PCN 20,000 units/mL thigh dose). Investigators were blinded to the s olutions used. Wounds were covered with a vapor permeable dressing, Six day s after treatment, each wound was examined for signs of infection and then excised for quantitative bacteriologic analysis. colony counts were reporte d as counts per gram of tissue. Wounds in the four irrigation solution grou ps were compared using ANOVA, A log difference of 3 was considered signific ant. The average log total bacteria/gram tissue for the four groups were: c ontrol, 4.35 (95% CI; 1.01); low dose, 4.09 (95% CI; 1.42); intermediate do se, 4.47 (95% CI; 1.27); and high dose, 3.45 (95% CI; 1.33). No wounds in t he high dose group had any clinical signs of infection, whereas 50% of woun ds in the intermediate dose group, 42% in the low dose group, and 33% in th e control group had either erythema, induration, or purulence. There were n o statistically significant differences in the bacterial counts/gram tissue or clinical infection rates in any of the groups. A format trend analysis failed to find a significant linear trend for decreasing bacterial counts f or either antibiotic. In this experimental bite wound model containing cont aminated, crushed tissue, irrigation with various solutions of cefazolin pl us penicillin G did not reduce quantitative bacterial counts more than 3.1 log total bacteria/gram tissue. (Am J Emerg Med 2001;19:1-5, Copyright (C) 2001 by W.B. Saunders Company).