RESUMO
The aim of this study was to determine the prevalence and antibiotic susceptibility of Escherichia coli from retail raw chickens in different provinces of China.A total of 1 152 whole chicken samples were collected and screened for the prevalence of E.coli,and then the E.coli isolates were further tested for the antimicrobial susceptibility using agar dilution method.Results showed that the overall positive rate for E.coli in retail chickens was 65.97％ (760/1 152);resistance was most common to nalidixic acid (66.84％),followed by amoxicillin-clavulanic acid (66.05％),tetracycline (65.00％),trimethoprim-sulfamethoxazole (63.16 ％),ampicillin (60.66 ％),amoxicillin (51.32 ％),streptomycin (50.39 ％),chloramphenicol (48.32 ％),kanamycin (38.29 ％),gentamicin (26.31％),ciprofloxacin (25.79 ％) and cefoxitin (21.05 ％).The last were gatifloxacin,cefoperazone and amikacin (each ＜20％).Overall,70.53％ of the isolates were resistant to at least three antimicrobials.A large proportion of multidrug resistant isolates were resistant to 8 kinds of antimicrobials (10.26 ％).No strain was resistant to 15 kinds of antimicrobials.Furthermore,isolates recovered from different regions exhibited different resistance levels to most antimicrobials.Our findings indicate that retail chicken in China was commonly contaminated with E.coli,and many E.coli strains exhibited multiple drug resistance.Presence of multiple drug E.coli in raw chickens may pose a potential threat to human health.
RESUMO
Nine compounds were isolated and purified by column chromatographic techniques including macroporous resin, silica gel, ODS, Sephadex LH-20, and preparative reversed-phase HPLC. Their structures were elucidated as taxifolin (1), naringenin (2), chalconaringenin (3), acacetin (4), quercetin 3-O-beta-D-galactopyranoside (5), 6-prenylnaringenin (6) xanthohumol (7), desmethylxanthohumol (8), xanthohumol B (9) on the basis of MS and NMR spectroscopic data analysis. Compounds 1-5 were isolated from Humulus lupulus for the first time.