Isolation And Identification Of Staphylococcus Aureus From Fresh Meat And Study On Its Antibiotic Resistance

Staphylococcus aureus is one of the major pathogens in fresh meat and can transmit to humans through the food chain,causing human infections.With the extensive use of antibiotics,Staphylococcus aureus has became increasingly resistant,among them,the resistance of methicillin-resistant Staphylococcus aureus(MRSA)is particularly prominent,which brings great difficulties to clinical treatment.This study collected 100 raw meat samples from Tai'an supermarkets and farmers' markets,using national standard method to separate and identify Staphylococcus aureus and validated by PCR,antibiotic susceptibility testing by paper diffusion method(K-B),adopting double PCR method to analysis resistant genes of isolating S.aureus strains.The main results are as follows:(1)A total of 100 fresh meats were collected by random sampling,including 53 fresh pork,27 fresh beef,and 20 fresh chicken,using national standard method to separate and identify Staphylococcus aureus and validated by PCR,a total of 21 samples were detected for Staphylococcus aureus,one sample for each positive sample;Among them,the detection rate was 26.4% for fresh pork,22.2% for fresh beef,and 5% for fresh chicken.The detection rate of Staphylococcus aureus in supermarkets(22.2%)was higher than that of Staphylococcus aureus in farmers' markets(18.9%).(2)Antibiotic susceptibility testing of 13 antibiotics using the disk diffusion method on 21 Staphylococcus aureus isolates,the drug resistance rate in descending order were: Kana(57.1%)?FOX(47.6%)?AMK(47.6%)?TET(38.1%)?CIP(38.1%)?CLI(33.3%)?GEN(33.3%)?CFZ(28.6%)?CRO(28.6%)?CHL(19%)?NOR(19%)?OFLX(4.8%),not resistant to RIF.The MRSA detection rate was 47.6%(10/21),verification of mec A gene by PCR method,conformity rate is 40%(4/10).Multiple drug resistance analysis was performed on 10 strains of MRSA and it was found that there were different levels of multidrug resistance,the rate of resistance to 5 or more than 5 antibiotics was 50%(5/10),with the most serious resistance are tetracyclines,aminoglycosides,and cephalosporins.(3)Detection of drug resistance gene results,the highest detection rate of aac(6')/aph(2'')and aph(3')-III genes in 21 strains of Staphylococcus aureus,it is 47.6%(10/21),the positive predictive values for GEN,KANA,and AMK are 60%,70%,and 50%,respectively;Negative predictive values are 90.9%,54.4%,54.4%,respectively.The detection rate of mec A gene is28.6%(6/21),the positive predictive value for CFZ and CRO are 100%;Negative predictor is100%.The tet K gene detection rate is 14.3%(3/21),the positive predictive value for TET is100%;The negative predictive value is 68.75%.The erm C gene detection rate was 9.5%(2/21),the positive predictive value for clindamycin is 100%;The negative predictive value is73.7%.