Survival Of Methicillin-resistant Staphylociccus Aureus Rfrom Different Sources In Water

Staphyloccus aureus is an opportunistic pathogen capable of causing a wide variety of infectious diseases and is usually associated with humans as commensal colonizing organisms in at least 30% of the population.Staphylococcal infections are primarily of the skin and soft tissues;however,they are capable of causing much more serious systemic infections and death,especially when associated with methicillin resistance.Methicillin-resistant Staphylococcus aureus(MRSA)was evolved from methicillin-susceptible Staphylococcus aureus by acquisition of genetic material associated with the mec A gene.Since the first report of livestock-associated MRSA(LA-MRSA)infections in the Netherlands in 2004,concerns about LA-MRSA have continued to increase.China takes the first place in pig production and pork consumption in the world,and antibiotics are more commonly used in the pig breeding industry.Therefore the Chinese pig herd could be an important repository for MRSA.However,the current investigation on the prevalence of staphylococcus aureus and MRSA in Chinese pig herds is not comprehensive enough.MRSA is an important and representative drug-resistant bacteria.It is of great public health significance to understand the prevalence and the characteristics of MRSA in pig farms.At the same time,water may play a potential role in microbial transmission as one of the important media in the farm environment.This study was based on the MRSA and MSSA strain libraries obtained from the samples,This paper studied the phenotypic characteristics of MRSA population survival in water,analyzed the correlation between the strain’s survival ability in water and its source and genotype,and mined the genes related to the survival ability in water.1.Two methods of separation of MRSAThe study collected samples from 23 pig farms of different sizes in central China.In each pig farm,nasal swabs were used to collect samples from sows,fattening pigs at the age of 20 weeks,and the workers.At the same time,Samples of dust in the pig house were collected in jars containing sterile medium.A total of 1268 samples were collected from 23 pig farms.The two methods were used to isolate and identify MRSA.In the first method,MRSA was separated by MRSA chromogenic medium,and the MRSA was preliminary determined by fem B detection and confirmed by biochemical assay.In the second method,the Staphylococcus aureus was isolated by using Baird-Parker agar medium,then extract the DNA of the strain and the fem B gene was amplified by DNA,the staphylococcus aureus was detected and identified with fem B gene and finally MRSA was identified by MH agar culture with 4μg/m L oxacillin.Previously,our laboratory has isolated and identified MRSA in 85 samples by using the first method.The separation rate of MRSA was 6.70%.The average isolation rates of MRSA for sows,fattening pigs,dust and pig farm workers were7.01%,5.97%,2.46%,and 11.54%,respectively.In order to simultaneously separate MRSA and MSSA from the sample,the method 2 used to separate Staphylococcus aureus from sample.Staphylococcus aureus was isolated from 193 samples,and the isolation rate of Staphylococcus aureus was 15.30%.Staphylococcus aureus isolated from 90 samples was MRSA,and the detection rate of MRSA was 7.01%。MSSA was isolated from another 103 samples,with a detection rate of 8.12%。MRSA accounted for 46.63% of Staphylococcus aureus.Neither MRSA nor MSSA were isolated from the same sample.The two methods were used to separate MRSA,and there was a difference in each field separation,but the overall sample MRSA detection rate was similar2.Survival of different MRSA populations in waterThe experimental strain comes from two aspects.289 strains of staphylococcus aureus(257 MRSA and 32 MSSA)were isolated from other pig farms and saved by the laboratory.105 strains of staphylococcus aureus(103 MRSA strains and 2 MSSA strains)from three hospitals.The results showed that the survival ability of MRSA in water was indeed different from different sources.The strains from hospital patients had the strongest survival ability in water,followed by the strains from pig worker,fatten pig,and pig house dust,and the MRAS from sows had weaker survival ability in water.From the perspective of the MLST type of staphylococcus aureus,the survival of different MLST types of staphylococcus aureus in water is different,among which the ST9 strain is significantly different from other ST strains in the viability of water.When the MLST type was the same,the survival of MSSA is batter than MRSA in water.Correlation analysis of survival characteristics and genomes in different MRSA populations revealed that one of the MRSA-ST59 strains encoding the putative prophage protein gene(Gene2456)was associated with the viability of MRSA in water.The experimental comparison showed that the MRSA-ST59 strain carrying the Gene2456 gene was more viable in water than the strain without the gene.