Initial wound treatment is critical in the treatment of open fractures, contaminated wounds, and abscesses. Ample evidence suggests that high-pressure pulsatile lavage damages bone structure and disrupts soft tissue. We compared the depth of penetration and amount of retention of bacteria in contaminated soft tissue subjected to one of two lavage methods: high-pressure pulsatile and low-pressure gravity flow. Fresh ovine muscle was harvested, contaminated with fluorescently stained Staphylococcus aureus, and subjected to lavage treatment. Specimens in each lavage method group were subdivided based on orientation across or in line with the muscle fibers. High-pressure lavage causes increased depth of bacterial penetration (across: 3,835 microm; in line: 4,220 microm) when compared with low-pressure lavage (across: 1,680 microm; in line: 2,095 microm). Furthermore, both high-pressure treatment groups had higher numbers of retained bacteria as counted in 50 mum x 7,500 microm x 5 microm sections of tissue after lavage (across: 197; in line: 188) when compared with the low-pressure groups (across: 94; in line: 40). These results show that high-pressure pulsatile lavage causes deeper penetration of bacteria and results in greater bacterial retention in soft tissue when compared with low-pressure lavage.