Disinfection Of Antibiotic Resistant Bacteria In Hospital Wastewater And Its Drug-resistant Transmission Characteristics

Carbapenem is a class of ?-lactam antibiotic with specific molecular structures.Because of its strong antibacterial ability,it has been widely used to treat severe infections caused by cephalosporin antibiotic-resistant Enterobacteriaceas in clinics,and is known as the "last line of defense" for treating gram-negative bacterial infections.In recent years,with the extensive use of carbapenem antibiotics,a large number of carbapenemase resistant Enterobacteriaceaes(CRE)have been detected around the world,posing serious threats to human health.Hospital wastewater contains loads of ARGs and ARB,which are important sources of CRE and carbapenem resistance genes in the environment.However,the existing disinfection processes in hospitals may induce the culturable CRE to enter VBNC state,making them difficult to remove and detect.After entering the environment,they will still have the ability to transfer the resistance genes between microorganisms,helping the carbapenem resistance genes further spread in the environment.How to reduce the resuscitated ability of CRE in VBNC state in the environment and the spread ability of resistance genes after resuscitation are of great significance for controlling the transmission of carbapenem resistance genes.This study started with the investigation of the abundance of carbapenem resistance genes in hospital wastewater and the species of carbapenem-resistant bacteria in hospital effluent from three hospitals in Zhejiang Province,revealed the reduction effect of carbapenem resistance genes in existing hospital wastewater treatment.At the same time,two different disinfection methods,UV disinfection and chlorination,were researched for their reduction effect of carbapenem-resistant Escherichia coli(CREC)and carbapenem-resistant Klebsiella pneumoniae(CRKP)and bla NDM-1.In addition,this study also revealed the possibility of resuscitation and the risk of transmitting resistance genes after VBNC state carbapenem-resistant bacteria discharged from the hospitals into the environment,and proposed corresponding solutions.The main conclusions are as follows:(1)The carbapenem-resistant bacteria in the effluent of the three hospitals in Zhejiang Province mainly consist of Enterococcus(59.90%)and Proteus(35.72%),followed by a small amount of Klebsiella(3.13%)and Escherichia(1.25%).The maximum reduction rates of three carbapenem resistance genes of bla NDM-1,bla GES-5,and bla VIM-1 by the hospital disinfection process reached 74.42%,50.88%,and 83.52% respectively.The reduction effect is related to the reduction of microbial biomass.(2)Both chlorination and UV disinfection can reduce the culturable CREC and CRKP and the bla NDM-1 carried by them effectively.The ability of UV disinfection to reduce bla NDM-1 is worse than chlorination.Chlorination can effectively reduce the total number of viable CREC and CRKP,but UV disinfection cannot effectively reduce the total number of viable CREC and CRKP,which will induce most of the culturable bacteria to enter the VBNC state.(3)Both CREC and CRKP in VBNC state can be partially resuscitated in hospital effluent after disinfection.Increase the disinfection dose can reduce the resuscitation possibilities of drug-resistant bacteria in VBNC state.(4)Compared to the untreated drug-resistant bacteria,the drug-resistant bacteria which enter the VBNC state induced by chlorination has small changes of transconjugative efficiency after resuscitation.However,the drug-resistant bacteria which enter the VBNC state induced by UV disinfection has significant reduction in their transconjugative efficiency after resuscitation.Medical institutions can reduce the drug-resistance transmission possibility of bacteria in VBNC state by maintaining a high dose of chlorination or installing UV disinfection devices.