Isolation and identification of a novel Staphylococcus from benzalkonium chloride solution

A bacterium was isolated from benzalkonium chloride solution (5%) stored in an uncovered bottle. The strain was identified as Staphylococcus aureas named SA-RBC through the test of its morphology, biochemical and physiological characterization. The isolated strain SA-RBC has important symbol of pathogenic Staphylococcus by producing coagulase, phosphatase and thermonuclease. Resistance of SA-RBC to disinfectants or antibiotics was tested. The results showed that the strain was highly resistant to benzalkonium chloride, benzalkonium bromide, glutaraldehyde and sodium hypochlorite, but susceptive to phenylic acid. SA-RBC was highly resistant to oxacillin, cefoperazone, cefoxitin, gentamicin, ciprofloxacin, and tetracycline. The tolerable growth concentration of SA-RBC on various surfactants was examined. The results indicated that the strain SA-RBC could grow in a higher concentration of cationic surfactants up to 5%, compared with the control strains (Escherichia coli ATCC 25922, S.epidermidis ATCC12228 and S.aureus ATCC 29213) which were unable to grow in 0.1% cationic surfactants. The strain SA-RBC could not utilize benzalkonium chloride as the sole source of carbon and/or nitrogen. The findings in this study suggested that Staphylococcus aureas might be an original contaminant in the quaternary ammonium disinfectant and has potential risk for public health.