Study On The Resistance Of Pseudomonas Aeruginosa To Ortho-phthalaldehyde And Iodophor And The Mechanisms

【Objective】The study observed the resistance of Pseudomonas aeruginosa to ortho-phthalaldehyde and iodophor and the mechanisms , searched on the relationship of cross resistances to antibiotics and disinfectants.【Methods】1.Experimental methodNeutralization tests were conducted with Pseudomonas aeruginosa ATCC15442. Minimal inhibitory concentration tests, minimal bactericidal concentration tests, suspension quantitative germicidal tests and continuously disinfecting tests were respectively conducted with ortho-phthalaldehyde and iodophor against Pseudomonas aeruginosa. qacE-sul1 gene was detected by PCR and located by isolating plasmid.2.Statistic methodsThe rank sum tests or chi square tests were used to compare the results of minimal inhibitory concentration and minimal bactericidal concentration by SPSS11.5 for Windows.The repeated measure ANOVA was used to compare the germicidal efficacy of ortho-phthalaldehyde and iodophor.【Results】1.The resistances of Pseudomonas aeruginosa to ortho-phthalaldehyde and iodophorThe resistant rate of Pseudomonas aeruginosa was 60% to ortho-phthalaldehyde and 20% to iodophor by MIC. The resistant rate of Pseudomonas aeruginosa was 41% to ortho-phthalaldehyde and 28% to iodophor by MBC. The resistant rate of Pseudomonas aeruginosa to 400mg/L ortho-phthalaldehyde was 60% by log mean reduction for 1 min and 34% by log mean reduction for 3 min. The resistant rate of Pseudomonas aeruginosa to 80mg/L iodophor was 51% by log mean reduction for 1 min and 32% by log mean reduction for 3 min. The resistant rate of Pseudomonas aeruginosa to ortho-phthalaldehyde was 89% and it was 60% to iodophor by the paralleling test. The resistant rate of Pseudomonas aeruginosa to ortho-phthalaldehyde was 10% and it was 11% to iodophor by the series test. 2. The resistant tendency of Pseudomonas aeruginosa to ortho-phthalaldehyde and iodophorA ascending tendency of resistances to disinfectants was observed in Pseudomonas aeruginosa isolated continuously, from none to one disinfectant and from one to two. The mean logarithm reduction of ortho-phthalaldehyde and iodophor against Pseudomonas aeruginosa were shrinked gradually with increasing of the disinfected generation continuously.3.The detected results of qacE-sul1 geneThe positive rate of qacE-sul1 gene was 19%. All of qacE-sul1 gene were located in plasmid DNA. The sequencing to the PCR product of qacE-sul1 gene was conducted. It was 261 bp. The sequence was submitted to GenBank. Its accession number was FJ687220.There was no significant difference of the germicidal efficacy of ortho-phthalaldehyde and iodophor between qacE-sul1 gene positive and negative bacterium. No significant difference of the positive rate of qacE-sul1 gene was observed between Pseudomonas aeruginosa of resistance and no resistance to disinfectants.4.The relationship of resistances to antibiotics and disinfectants against Pseudomonas aeruginosaThere was no significant difference between MIC,MBC and the mean log reduction of ortho-phthalaldehyde and iodophor between groups of Pseudomonas aeruginosa of resistance and sensitivity to antibiotics.【conclusions】The resistance was severity to ortho-phthalaldehyde or iodophor against Pseudomonas aeruginosa. The bacterium which were resistant to ortho-phthalaldehyde were not absolutely resistant to iodophor, vice versa. There was a relationship between resistance and exposure to disinfectants at the low concentration.No significant difference was observed between the positive rate of qacE-sul1 gene and resistance to ortho-phthalaldehyde or iodophor. There was no significant difference between resistances to antibiotics and ortho-phthalaldehyde or iodophor.