Rapid Detection Of Staphylococcus Aureus And Antibiotic Resistance In Raw Milk

Staphylococcus aureus is a typical common Gram-positive bacteria that can multiply in food and produce a variety of toxins under certain conditions;Human or animal intake the food which polluted by Staphylococcus aureus,resulting in infection.S.aureus is the main pathogen of dairy cow mastitis,the abuse of antibiotics leads to the emergence and spread of drug-resistant Staphylococcus aureus,while increasing the risk of multiple drug resistance,this poses a direct threat to human health.Therefore,the study on the resistance of food-borne methicillin-resistant Staphylococcus aureus and its potential harm has become a hot spot in food safety field.In this study,130 raw milk samples were collected from major dairy farms in Jinan,the S.aureus in the sample was identified using biochemical assays;identification of Staphylococcus aureus using Matrix Assisted Laser Desorption Ionization Time-ofFlight Mass Spectrometry(MALDI-TOF-MS)to verify the feasibility of rapid detection of foodborne pathogens;the enterotoxin was detected by S.aureus using the Staphylococcus aureus enterotoxin test kit;the S.aureus enterotoxin was typed by PCR;the antibiotic sensitivity test was carried out by micro-broth dilution method.The main results of S.aureus were as follows:(1)130 fresh milk samples from six different areas of Jinan,collection forms are divided into fresh milk collection stations to collect samples with dairy carriers to collect samples.Using the traditional biochemical identification and API method identification,a total of 57 samples to determine the detection of Staphylococcus aureus,the average detection rate was 44.62%.JA1 to JA6 area of fresh milk samples are detected by Staphylococcus aureus.The detection rate of Staphylococcus aureus in the samples was higher than that in the fresh milk transport vehicle;The overall pollution degree was lower than 1000CFU/ml.(2)11 strains of enterotoxin were identified by enzyme-linked immunosorbent assay and colloidal gold rapid test strip.The results were SEA,SEB and SEB.57 strains of Staphylococcus aureus were detected by PCR,a total of 57 strains of SEA,SEB,SEC,SEE,SEG and SHE type 6 enterotoxin genotypes;the number of SEG and SHE enterotoxins was the highest(SEG: 52.63%,30/57;SHE: 36.84%,21/57).(3)57 strains of Staphylococcus aureus were tested by drug susceptibility by micro-broth dilution method.The results showed that the resistant strains were the most resistant to penicillin,the resistant rate was 87.72%,followed by ampicillin,the resistance rate was 84.21%,and the resistance to erythromycin and clindamycin was also higher.The multidrug-resistant strains were mainly from JA1,JA2 and JA3,and the number of resistant strains was the highest among the three drugs and resistant to five drugs,and the resistant strains were more affected by regional differences.(4)Detection of Staphylococcus aureus in samples by MALDI-TOF MS,57 strains of Staphylococcus aureus in the level of identification of the results of the credibility of more than 95%.It is proved that the stability of MALDI-TOF MS is good in the detection of foodborne pathogens,and its detection speed is high and the high flux is superior to other methods.Clustering Analysis of 57 Fungi Fingerprints,57 strains of Staphylococcus aureus were divided into five types,six regions of the sample mixed distribution in the five cluster analysis type.(5)The spectra collected by the MALDI-TOF MS method were analyzed.The study found that MALDI-TOF MS can rapidly detect anti-?-lactam antibiotics in Staphylococcus aureus,showing a special peak in the mass spectrum;resistance to aminoglycosides,chloramphenicol,clomycin antibiotics of Staphylococcus aureus can also be detected and identified.