Study On The Resistance Of Staphylococcus Aureus To Povidone Iodine,Glutaraldehyde And Its Mechanisms

【Objective】1.Study on the respectively resistance to Povidone Iodine,Glutaraldehyde of Staphylococcus aureus,MRSA,MSSA which are all with qac(A/B) gene.2.Study on the relationships between resistance and qac(A/B) gene of Staphylococcus aureus.3.Study on relationships between resistance to antibiotics and which to disinfectants of Staphylococcus aureus.4.Study on the resistance,induced by sublethal dose,to disinfectants of Staphylococcus aureus.【Methods】1 Experimental methodsWe used clinical 103 strains staphylococcus aureus as our experimental samples which are contiously collected from hospital,then carried out minimal inhibitory concentration tests,minimal bactericidal concentration tests and suspension quantitative germicidal tests;and PCR was employed to detect qac(A/B) 000gene of every strain of bacterium.Staphylococcus aureus which qac(A/B) gene's result is positive was devided into two groups with randomized blocks; firstly,one group's qac(A/B) gene were elimilated then compared with the other group,then elimilated the other group's qac(A/B) gene and run the other comparison of bacteria themselves between the non-elimilation and elimilation of qac(A/B) gene.At last,the resistance of Staphylococcus aureus ATCC6538, induced by sublethal dose for 30 times,was dectected again.2 Statistic methodsThe x2 tests was used to analyse the data of resistance rate.The K-W tests was used to analyse the data of minimal inhibitory concentration tests,minimal bactericidal concentration tests.The repeated measure ANOVA was used to analyse the data of suspension quantitative germicidal tests.The spearman correlate was used to analyse the relationships between the resistance to antibiotics and which to disinfectants of Staphylococcus aureus. 【Results】1 Samples'results:There are 67 strains(65.05%) MRSA,36 strains(34.95%) MSSA in all 103 strains staphylococcus aureus and among them,8 strains(7.67%) qac(A/B) gene are positive.2 Povidone Iodine effection on staphylococcus aureus2.1 Minimal inhibitory concentration:In thirty-six strains MSSA,there are four strains which MIC all were 25.0mg/l,twenty-seven strains' all were 37.5mg/l and five strains' all were 50.0 mg/l,resistance rate is 13.8%.In fifty-nine strains MRSA,there are three strains which MIC all were 37.5mg/l,nineteen strains' all were 50.0mg/l,thirteen strains' all were 62.5mg/l,nineteen strains' all were 75.0mg/l and five strains MIC all were more than 75.0mg/l,resistance rate is 94.9%;In eight strains Staphylococcus aureus with qac(A/B) gene,there are four strains which MIC all were 75.0mg/l and the other four strains' all were more than 75.0mg/l,resistance rate is 100.0%.The difference of MIC among three groups are statistical significant(H =66.785,P＜0.05),then post hoc test was used to compare every two groups with Bonferroni method and all difference are statistical significant(all P values＜0.017).2.2 Minimal bactericidal concentration:In thirty-six strains MSSA,there are two strains which MBC both were 25.0mg/l,fourteen strains' all were 37.5mg/l,eighteen strains' all were 50.0 mg/l and two strains' both were 62.5 mg/l,resistance rate is 5.5%;In fifty-nine strains MRSA,there are ten strains which MBC all were 50.0mg/l,fifteen strains' all were 62.5mg/l,thirteen strains' all were 75.0mg/l and twenty-one strains' all were more than 75.0mg/l,resistance rate is 83.1%;Eight strains Staphylococcus aureus with qac(A/B) gene which MBC all were more than 75.0mg/l.The difference of MBC among three groups are statistical significant(H =63.589,P＜0.05),then post hoc test was used to compare every two groups with Bonferroni method and all difference are statistical significant(all P values＜0.017).2.3 Killing effect:The mean and standard deviation of killing logarithm of MSSA exposed to the disinfection solution containing available iodine 40mg/L for 1min,3min,5min,7min were respectively 4.68±1.34,5.83±1.46,7.44±1.29,7.97±0.77;which of MRSA were respectively 3.34±0.73,4.24±0.66,5.02±0.79,5.91±0.98;and which of Staphylococcus aureus with qac(A/B) gene were respectively 2.29±0.12,3.11±0.24,3.59±0.50,4.24±0.53.The difference of average killing logarithm among three groups are statistical significant(F =63.589,P＜0.05), then post hoc test was used to compare every two groups with LSD method and all difference are statistical significant(all P values＜0.05).2.4 Effect of plasmid elimination:The mean and standard deviation of killing logarithm of Staphylococcus aureus with qac(A/B) gene exposed to the disinfection solution containing available iodine 40mg/L for 1min,3min,5min,7min were respectively 2.29±0.12,3.11±0.24,3.59±0.50,4.24±0.53;and which of with plasmid elimination were respectively 3.85±0.15,4.93±0.32,5.76±0.49,6.45±0.61 respectively.The difference of average killing logarithm between two groups was statistical significant(F=164.153,P＜0.05).2.5 Correlation between killing logarithm and total resistance:The spearman correlation coefficients between the killing logarithm and total resistance to antibiotics of Staphylococcus aureus were respectively -0.704,-0.753,-0.761,-0.664,all correlation coefficients are statical significant(all P values＜0.05).2.6 Induction by sublethal dose:ATCC₁ MIC was 37.5mg/l and which of ATCC₁₅ was 62.5mg/l,ATCC₃₀,75.0mg/l;ATCC₁ MBC was 50.0mg/l and which of ATCC₁₅ was 75.0mg/l,ATCC₃₀,more than 75.0mg/l.3 Glutaraldehyde effection on staphylococcus aureus3.1 Minimal inhibitory concentration:In thirty-six strains MSSA,there are five strains which MIC all were 31.25mg/l,twenty-three strains' all were 65.50mg/l and eight strains' all were 125.00 mg/l,resistance rate is22.2%.In fifty-nine strains MRSA,there are ten strains which MIC all were 62.50mg/l,forty-three strains' all were 125.00mg/l and six strains' all were 250.00mg/l,resistance rate is 83.1%; Eight strains Staphylococcus aureus with qac(A/B) gene which MIC all were 250.00mg/l,resistance rate is 100.0%.The difference of MIC among three groups are statistical significant(H =52.280,P＜0.05),then post hoc test was used to compare every two groups with Bonferroni method and all difference are statistical significant(all P values＜0.017).3.2 Minimal bactericidal concentration:In thirty-six strains MSSA,there are seven strains which MBC all were 62.50mg/l and teween-nine strains' all were 125.00mg/l,resistance rate is 0.0%;In fifty-nine strains MRSA,there are four strains which MBC all were 62.50mg/l,forty-nine strains' all were 125.00mg/l and six strains' all were 250.00mg/l,resistance rate is 10.2%;Eight strains Staphylococcus aureus with qac(A/B) gene which MBC all were 250.00mg/l, resistance rate is 100.0%.The difference of MBC among three groups are statistical significant(H =38.975,P＜0.05),then post hoc test was used to compare every two groups with Bonferroni method and all difference are statistical significant(all P values＜0.017).3.3 Killing effect:The mean and standard deviation of killing logarithm of MSSA exposed to the disinfection solution containing available iodine 80mg/L for 1min,3min,5min,7min were respectively 3.74±107,5.51±1.38,7.07±1.23,8.28±0.19;which of MRSA were respectively 2.67±0.59,4.01±0.63,4.77±0.78,8.36±0.12;and which of Staphylococcus aureus with qac(A/B) gene were respectively 221.83±0.09,2.93±0.23,3.41±0.05,8.51±0.05.The difference of average killing logarithm among three groups are statistical significant(F =70.112, P＜0.05),then post hoc test was used to compare every two groups with LSD method and all difference are statistical significant(all P values＜0.05).3.4 Effect of plasmid elimination:The mean and standard deviation of killing logarithm of Staphylococcus aureus with qac(A/B) gene exposed to the disinfection solution containing available iodine 80mg/L for 1min,3min,5min,7min were respectively 1.83±0.09,2.93±0.23,3.41±0.05,8.51±0.05;and which of with plasmid elimination were respectively 2.71±0.13,4.11±0.07,4.72±0.29,8.64±0.15 respectively.The difference of average killing logarithm between two groups was statistical significant(F=878.401,P＜0.05).3.5 Correlation between killing logarithm and total resistance:The spearman correlation coefficients between the killing logarithm and total resistance to antibiotics of Staphylococcus aureus were respectively -0.701,-0.746,-0.771,0.276,all correlation coefficients are statical significant(all P values＜0.05 ).3.6 Induction by sublethal dose:ATCC₁ MIC was 62.50mg/l and which of ATCC₁₅ was 125.00mg/l,ATCC₃₀,125.00mg/l;ATCC₁ MBC was 125.00mg/l and which of ATCC₁₅ was 125.00mg/l,ATCC₃₀ 250.00 mg/l.【Conclusions】1.The resistance of Staphylococcus aureus with qac(A/B) gene and MRSA,MSSA to Povidone Iodine were different to each other and to Glutaraldehyde, which were also different to each other.Whatever to Povidone Iodine or to Glutaraldehyde,which of Staphylococcus aureus with qac(A/B) gene was the strongest,MRSA's was the second strongest.2.The resistance of Staphylococcus aureus with qac(A/B) gene to Povidone Iodine,Glutaraldehyde were respectively stronger than its without qac(A/B) gene.Therefore,qac(A/B) is a kind of gene which can resist disinfectants.3.The spearman correlation coefficient between total resistance to antibiotics and which to disinfectants of Staphylococcus aureus is positive.4.The resistance of Staphylococcus aureus to disinfectants induced by sublethal dose is stronger than which of non-induced.