Introduction: Since the 1930s CO2 has been combined with cold storage for the preservation of food. Its use for the prevention of surgical wound infection was considered impractical. Now CO2 is used in endoscopic surgery and a method has been developed to create a CO2 atmosphere in an open cardiothoracic wound cavity. Therefore we studied the effect of CO2 on the growth of Staphylococcus aureus at body temperature.
Method: Firstly, S. aureus inoculated on blood agar was exposed to carbon dioxide (100%), standard anaerobic gas (5% CO2, 10% hydrogen, 85% nitrogen), or air at 37°C during 24 hours, whereupon a viable count was made. Secondly, S. aureus inoculated in brain-heart infusion broth cultures, kept at 37°C, was exposed to CO2 or air for 0, 2, 4, 6, and 8 hours when optical density was measured.
Results: After 24 hours the number of S. aureus on blood agar was about 100 times lower in CO2 than in anaerobic gas (P = 0.001, Wilcoxon's test), and about 1000 times lower than in air (P = 0.001). Also in broth there were fewer bacteria with CO2 than with air (P < 0.01). After 2 hours the number of bacteria was increased with air (P < 0.001) but not with CO2 (P = 0.13). After 8 hours the optical density had increased from zero to 1.2 with air and to 0.01 with CO2 (P = 0.001).
Conclusions: 100% CO2 significantly decreased the growth rate of S. aureus at body temperature. The inhibiting effect of CO2 increased exponentially with time. Its bacteriostatic effect may help to explain the low infection rates in endoscopic surgery.
1 Coyne FP. The effect of carbon dioxide on bacterial growth. Proc Royal Soc Series B
2 Persson M, van der Linden J. De-airing of a cardiothoracic wound cavity model with carbon dioxide: theory and comparison of a gas diffuser with conventional tubes. J Cardiothorac Vasc Anesth
3 Dixon NM, Kell DB. The inhibition by CO2
of the growth and metabolism of microorganisms. J Appl Bacteriol
: 109-136. Review.