Efficacy of disinfectants against naturally occurring and artificially cultivated bacteria

Naturally occurring bacteria, is exist in nature, and is never cultivated on conventional culture medium. We evaluated the efficacy of disinfectants against naturally occurring bacteria in in-use cotton balls soaked in 0.02% benzalkonium chloride solution which had been used to disinfect the genital area by patients undergoing self-catheterization at home and the same bacteria subcultured on nutrient broth (artificially cultivated bacteria). The colony forming units (CFU) of naturally occurring bacteria such as Serratia marcescens, Alcaligenes xylosoxidans, and Burkholderia cepacia were not decreased after 48 h exposure to 0.025-0.1% benzalkonium chloride solution, but the same strains subcultured on nutrient broth were killed within only 10 min exposure to 0.025-0.1% benzalkonium chloride solution. In addition, the CFU of these three kinds of naturally occurring bacteria were not decreased after 48 h exposure to 0.02% chlorhexidine gluconate solution, but the same strains subcultured on nutrient broth were killed within 2 h exposure to chlorhexidine gluconate solution. The result showed that disinfectant efficacy differed markedly against naturally occurring and artificially cultivated bacteria. Therefore, it is preferable to use the naturally occurring bacteria not only artificially cultivated bacteria when examining disinfectant efficacy.