A novel method to detect bacterial resistance to disinfectants

In clinical practice,the important hygienic prevention of bacterial pathogen spread is disinfection of potentially contaminated area.Benzalkonium bromide and chlorhexidine acetate are commonly used disinfectants with a broad spectrum of antimicrobial effect.It is vital to inhibit the spread of pathogen in hospital.However,a large number of pathogens with the decreased antiseptic susceptibility have been isolated from clinical samples which showed an increased minimal inhibitory concentration(MIC)against those antiseptics.These resistant pathogens are the major causes for nosocomial crossinfections in hospital.The present study demonstrated the utility of Oxford plate assay system in determining the potential disinfectant resistance of bacteria.The microbiological assay is based on the inhibitory effect of tested disinfectants upon the strains of Staphylococcus aureus and Escherichia coli.Statistical analysis of the bioassay results indicated the linear correlation(r=-0.87-0.99,P<0.01)between the diameter of growth inhibition zone and the log dosage of the tested disinfectants.Moreover,comparison of inhibitory efficacy of benzalkonium bromide upon 29 S.aureus strains isolated from clinical samples by both Oxford plate method and broth dilution method showed that the diameter of growth inhibition zone has significantly negative correlation with the minimal inhibitory concentration(MIC)(r=-0.574,P<0.001).These results suggest that the Oxford plate is a simple and time-saving method in detecting potential clinical disinfectant resistance and its usefulness for routine surveillance of pathogenic resistance to disinfectants warrants further investigation.

Comparison of different disinfection processes in the effective removal of antibiotic-resistant bacteria and genes

This study compared three different disinfection processes （chlorination, E-beam, and ozone） and the efficacy of three oxidants （H202, S2O8-, and peroxymonosulfate （MPS）） in removing antibiotic resistant bacteria （ARB） and antibiotic resistance genes （ARGs） in a synthetic wastewater. More than 30 mg/L of chlorine was needed to remove over 90% of ARB and ARG. For the E-beam method, only 1 dose （kGy） was needed to remove ARB and ARG, and ozone could reduce ARB and ARG by more than 90% even at 3 mg/L ozone concentration. In the ozone process, CT values （concentration × time） were compared for ozone alone and combined with different catalysts based on the 2-log removal of ARB and ARG. Ozone treatment yielded a value of 31 and 33 （mg·min）/L for ARB and ARGs respectively. On the other hand, ozone with persulfate yielded 15.9 and 18.5 （mg.min）/L while ozone with monopersulfate yielded a value of 12 and 14.5 （mg·min）/L. This implies that the addition of these catalysts significantly reduces the contact time to achieve a 2-log removal, thus enhancing the process in terms of its kinetics.