| As one of the important achievements in human history,the discovery of antibiotics changed medicine and saved countless lives.However,problems such as the abuse of antibiotics have led to the emergence of Resistomes and Microbiomes which not only affect public health,but also attract attention as new environmental pollutants.Humans breathe all the time,but the spread of Resistomes and Microbiomes in the atmosphere is often overlooked.In some indoor public places,especially kindergartens where children live and study,the widespread use of air conditioners provides a breeding ground for the growth of Microbiomes and promotes the spread of Resistomes.In recent years,there have been reports of diseases caused by exposure of pathogenic microorganisms in air-conditioning in public places,and the untargeted and irregular cleaning of air-conditioning has exacerbated the potential risk of disease.Therefore,it is necessary for the Resistomes and Microbiomes in the air-conditioning system.This study analyzed 13 air-conditioning filter dust samples from 3 kindergartens(named A,B,and C kindergartens correspondingly)in the suburbs,urban areas,and outer suburbs of Tianjin.Combining 16S r RNA high-throughput sequencing,real-time fluorescent quantitative PCR(q PCR),isolation,culture and identification of drug-resistant bacteria,and CFU plate count,etc.,to study the abundance and diversity of Resistomes and Microbiomes,the correlation with the Microbiomes and Resistomes,and the potential risk of human exposure.The main conclusions drawn are as follows:(1)The kindergarten air-conditioning system serves as an important repository of Resistomes.In this study,95 drug resistance gene subtypes and 5 mobile genetic elements(MGEs)were detected.The relative abundance of total drug resistance genes was 0.11～0.84copies/16S r RNA genes.The proportions of the detected abundances of various drug resistance genes in the three kindergartens were consistent,mainly Vancomycin,Tetracycline and mobile genetic elements(MGEs).In terms of the total relative abundance of 7 types of ARGs(Tetracycline,β-lactam,Vancomycin,Chloramphenicol,Sulfonamide,MLSB and MGEs),kindergarten B showed a significantly higher abundance than the other two kindergartens(p<0.05).In addition,there was a significant positive correlation between ARGs and MGEs in the three kindergartens(r≥0.9999,p<0.001).The results showed that the kindergarten located in the urban area was more polluted by drug-resistant genes than in the suburbs and outer suburbs,and the drug-resistant genes detected in the three kindergartens all had potential horizontal transfer risks.(2)The Microbiomes in the dust of the air-conditioning filter of kindergarten is rich in composition.The dominant pathogenic bacteria phyla of the three kindergartens are all Proteobacteria(A,B,and C kindergartens accounted for 79.8%,65.92%and59.98%respectively),Firmicutes(A,B,C)The percentages of kindergartens were17.93%,13.49%,and 18.93%)and Actinobacteria(A,B,and C kindergartens accounted for 2.11%,15.03%,and 8.33%,respectively).The dominant pathogenic bacteria are different among the three kindergartens.The dominant pathogenic bacteria in kindergartens A and C are Acinetobacter,accounting for 75.03%and 21.32%,respectively.Kindergarten B is Pantoea.Accounted for 15.93%.In terms of the total absolute abundance of bacteria,kindergarten B(10~6 copies/m3)was significantly higher than kindergarten C(10~5 copies/m3)by an order of magnitude(p<0.05).For colony forming unit,there is little difference in abundance among three kindergartens.(3)A total of 289 single bacteria with carbapenem and polymyxin resistant phenotypes were isolated.The dominant drug-resistant pathogens in the air-conditioning system of kindergarten A are Ochrobactrum(27%)and Staphylococcus(46%).The dominant drug-resistant pathogens in the air-conditioning system of kindergarten B are Staphylococcus(accounting for 55%)and Ochrobactrum(15%).The dominant drug-resistant pathogens in the air conditioning system of kindergarten C are Klebsiella(18%)and Ochrobactrum(17%).The results show that there are a large number of active drug-resistant pathogens in the air-conditioning filter systems of the three kindergartens,which pose a potential risk of disease to the kindergarten population.(4)Through Network analysis,it is found that there is a spearman correlation between the Resistomes and Microbiomes in the air conditioning systems of the three kindergartens.It is further found that the correlation between the drug resistance gene subtypes and bacteria detected in kindergarten B(Network has 210 nodes)is denser than that of kindergarten A(28 nodes)and kindergarten C(20 nodes).And Ochrobactrum isolated from the drug-resistant phenotype was used as a potential pathogenic host for 18 drug-resistant genes in kindergarten B.(5)By calculating the inhalation of potential pathogenic bacteria and the resistance genes they may carry,it is found that the inhalation of Ochrobactrum,Staphylococcus and Neisseria in kindergarten B is all Significantly higher than A and C kindergarten 1 order of magnitude.Potential pathogenic hosts may carry resistance genes,especially erm X,mef A,and str B.The inhalation amount exposed to kindergarten B is 4-6 times that of kindergarten A and C.The results showed that the drug resistance genes in the air conditioning system of kindergartens may be carried by a large number of potential pathogenic bacteria,and showed a higher risk of drug resistance inhalation.This study analyzed the Resistomes and Microbiomes in the air-conditioning filters of kindergartens from different regions and found that there are a large number of drug-resistant groups and microbiomes in the air-conditioning filter systems of kindergartens,and a variety of potential pathogenic bacteria carry drug-resistant genes,and exhibit a high potential exposure risk.The results of this study lay the foundation for the subsequent analysis of Resistomes and Microbiomes in the air-conditioning system,spreading and pollution prevention,and also provide theoretical support for the future development of indoor air-conditioning system disinfection and cleaning strategies. |
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