Effect of vacuumª²assisted closure on bacteria load and G+ to G- bacteria ratio in pig¬ðs infected soft tissue blast injury

    LI Wangª²Zhou, LI Jinª²Qing, LI Xueª²Yong, CHEN Shaoª²Zong, LI Yueª²Jun, L¦a Xiaoª²Xing

    Department of Plastics and Burns, Tangdu Hospital, Fourth Military Medical University, Xi¬ðan 710038, China

    ¡¾Abstract¡¿ AIM: To observe the effect of vacuumª²assisted closure (VAC) on the bacteria load and the ratio of G+ bacteria to G- bacteria in pig¬ðs infected soft tissue blast injury. METHODS: Sixteen blast wounds£¬created by explosion of a specific type of electric detonators which were fixed at 1 cm over the skin of the shoulders and hips of 4 small white domestic pigs (15-20) kg£¬ were divided into 2 groups: the control group treated with conventional dressing change, and the experimental group treated with VAC at -15 kPa. All wounds were left untreated until the 3rd day after explosion and subsequently were infected. Tissue specimens, collected from the wounds before treatment and at different time points (1, 3, 6, 9, 14, and 19 d) after treatment, were weighed and homogenized, and each specimen¬ðs homogenate, after diluted, was plated on blood agar and incubated at 37¡æ for 24 h. After the number of bacterial colonies was counted, 200 out of the bacterial colonies of each specimen were processed for conventional Gramª²staining and the rate of gramª²positive bacteria was calculated. RESULTS: Before treatment, the wound bacteria load of the 2 groups was up to about 3¡Á107 cfu/g; it decreased to (1.91¡À0.245) ¡Á105 cfu/g at day 3 after treatment in experimental group, and to (0.51¡À0.120) ¡Á105 cfu/g at day 6; it decreased more slowly in control group to (19.54¡À3.67) ¡Á105 cfu/g at day 9 after treatment and to (3.26¡À0.83) ¡Á105 cfu/g at day 19 after treatment. Meanwhile, the rate of Gramª²positive bacteria was about 31%-36% of total bacteria in all wounds before treatment; that of experimental group increased to (55.58¡À2.98)% at day 6 after treatment and maintained at a high level thereafter; that of control group fluctuated between 30% and 40% from 1 to 19 d after injury. Compared with control group, experimental group had less bacteria and higher rate of gramª²positive bacteria (P<0.01) from 1 to 19 d after treatment. CONCLUSION: VAC can significantly decrease the bacteria load and the rate of Gramª²negative bacteria in pig¬ðs infected soft tissue blast injury. ......