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Objective To investigate the mechanism of efflux pump AcrAB-TolC involved in the cross-resistance between quaternary ammonium compounds ( QAC) and fluoroquinolones ( FQ) in Escherich-ia coli. Methods Seventy-eight Escherichia coli strains were isolated from clinical samples and then tested for the sensitivity to benzalkonium bromide by ager dilution method. Six strains were randomly selected and induced with benzalkonium bromide. Changes in the sensitivity of these strains to benzalkonium bromide and ciprofloxacin were analyzed after induction. Expression of the efflux pump genes acrA, acrB and tolC at mRNA level in the induced strains and their parent strains were detected by quantitative real-time PCR. Re-sults Among the 78 strains, the minimum inhibitory concentrations ( MIC) ranged from 8 μg/ml to 64μg/ml and 47. 4％ of strains have higher MIC than the standard strain. Compared with the parent strains, the induced strains showed higher expression of acrA and tolC genes, and the differences between the two groups were statistically significant. The MIC values of ciprofloxacin to the six induced strains were 4-8 times higher than those to their parent strains. Conclusions It was speculated that the increased expression of acrA and tolC genes at transcription level in the induced strains were related to the cross-resistance between quaternary ammonium compounds and fluoroquinolone antibiotics.
ABSTRACT
@#Microbial infections affect people worldwide. Quaternary ammonium salts serve antibacterial, antifungal, antiviral, anti-matrix metalloproteinase and polymerization functions. While the modification of biomaterials with quaternary ammonium salts cannot affect the physical or chemical properties of the biomaterials, this process can confer them with stable biological activity. Currently, quaternary ammonium salts are widely used in the development of functional orthopedic materials, sutures, dressings and dental materials, and the idea of modifying biomedical materials with quaternary ammonium salts has become the most promising, e.g., for preparing antimicrobial biomaterials. Recent studies have found that quaternary ammonium salt-modified antimicrobial monomers are cytotoxic. Therefore, it is of great significance to explore the cytotoxic mechanism of quaternary ammonium salt-modified antimicrobial monomers and determine possible cytoprotective measures for improving the biological safety of these antimicrobial resin-based materials and expanding their clinical applications. In addition, further validation of the clinical efficacy of these biomaterials is particularly important for accurately evaluating the clinical prospects of these biomaterials. Based on a literature review, this paper summarizes the applications and toxicity of biomedical materials modified with quaternary ammonium salts.
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OBJECTIVE To investigae the gene resistant to quaternary ammonium compounds of multiple drug resistant Acinetobacter baumannii(MDR-ABA).METHODS The quaternary ammonium compounds qacE?1 gene in 20 MDR-ABA strains were detected by PCR.RESULTS The 20 MDR-ABA strains showed multiple resistance,its sensitivity to imipenm was 65% only.Among twenty strains of MDR-ABA qacE?1 gene were all positive.CONCLUSIONS The results indicate that qacE?1 gene were all carred class 1 integron.The chlorhexidine usage in prevnting hospital infection after surgery should be reevaluated.