CHALLENGE TEST FOR LIQUID SOAP WITH CHLORHEXIDINE

AC04

Fiorentino, FAM, Perez,JP, Correa, MA, Salgado, HRN

Universidade Estadual Paulista “Júlio de Mesquita Filho”, UNESP, Araraquara, SP, Brazil

Introduction: Nonsterile products might be contaminated with microorganisms, specially those with higher amount of water. Antimicrobial preservatives are added to nonsterile products to protect them from microbiological growth or from microorganisms that are introduced during manufacturing process or using by consumer. The challenge test allows analyzing the efficacy of preservative system in specific formulations. In this test, the formulation is inoculated with a well-known concentration of microorganisms to verify a presence of microorganisms through of colony-forming units (CFU).  Chlorhexidine is an antiseptic with large spectrum, active against Gram-positive and Gram-negative bacterias, any fungis and virus used in many medical areas. Objective: It was to analyze a formulation of liquid soap with chlorhexidine and the same formulation without chlorhexidine using the method of fast test (value D) and the conventional test (analyzing for 28 days), to verify the speed necessary to kill the microorganisms used. Method: The formulations were contaminated with concentration of test microorganisms of 10⁶ CFU/mL of the product. S. aureus, E. coli, P. aeruginosa, C. albicans and A. niger were used as test microorganisms. The test was carried out during 0 hour, 2^nd, 6^th, 12^th, 24^th, 48^th hour, 7^th day, 14^th , 21^st and 28^th day. The value D (time necessary to degree 1 log, in other word, to kill 90% of microbial population) was determineted using the negative reciprocal of the slopes of the regression line, using the linear portions of the survivor curves (log₁₀ CFU/mL versus time of exposure to the antimicrobial preservative. Results: Both formulations were satisfactory for challenge test for all microorganisms used because the microorganisms killed in less 48 h and during the time of the test did not have developing of cultures. The value D for P. aeruginosa for formulation with chlorhexidine was 3.9 h and for formulation without chlorhexidine, was 8.0 h;  for E. coli, the value D for formulation with chlorhexidine was 1.9 h and for formulation without chlorhexidine, was 3,9 hours; for A. niger, the value D of formulation with chlorhexidine was 3.9 h and for formulation without chlorhexidine, was 8.0 h; for  S. aureus and C. albicans did not was possible to calculate the value D because the time necessary to kill completely these microorganisms was very short, less of 2 h. Conclusion: The two formulations were satisfactory for antimicrobial preservative and both were effectiveness to meet criteria specified for challenge test by BP (2003) and USP (2006). The value D agree with conventional method for all microorganisms used in this test. It was observed the among microorganism analyzed, P. aeruginosa was the more resistant.