Carbon dioxide inhibits the growth rate of Staphylococcus aureus at body temperature

Background Since the 1930s, carbon dioxide (CO 2 ) has been combined with cold storage for the preservation of food. However, its use for the prevention of surgical wound infection was long considered to be impractical. Now CO 2 is widely used during laparoscopic procedures, and a method has been developed to create a CO 2 atmosphere in an open wound. The aim of this study was to investigate the effect of CO 2 on the growth of Staphylococcus aureus at body temperature. Methods First, S. aureus inoculated on blood agar were exposed to pure CO 2 (100%), standard anaerobic gas (5% CO 2 , 10% hydrogen, 85% nitrogen), or air at 37°C for a period of 24 h; then a viable count of the bacteria was made. Second, S. aureus inoculated in brain–heart infusion broth and kept at 37°C were exposed to CO 2 or air for 0, 2, 4, 6, and 8 h; then the optical density of the bacteria was measured. Results After 24 h, the number of S. aureus on blood agar was about 100 times lower in CO 2 than in anaerobic gas ( p = 0.001) and about 1,000 times lower than in air ( p = 0.001). Also, in broth, there were fewer bacteria with CO 2 than with air ( p < 0.01). After 2 h, the number of bacteria was increased with air ( p < 0.001) but not with CO 2 ( p = 0.13). After 8 h, the optical density had increased from zero to 1.2 with air but it had increased only to 0.01 with CO 2 ( p = 0.001). Conclusion Pure CO 2 significantly decreased the growth rate of S. aureus at body temperature. The inhibitory effect of CO 2 increased exponentially with time. Its bacteriostatic effect may help to explain the low infection rates in patients who undergo laparoscopic procedures.