Study of the anti-MRSA activity of Rhizoma coptidis by chemical fingerprinting and broth microdilution methods

AIM： Methicillin-resistant Staphylococcus aureus （MRSA） is a pathogenic bacterium that causes both hospital- and community-acquired infections, and for which single-drug treatments are becoming less efficient. Rhizoma coptidis has been used for more than two thousand years in China to treat diarrhea, fever, and jaundice. In this study, the anti-MRSA activity of Rhizoma coptidis is examined and its effective components sought. METHODS： The mecA and norA genes were determined by PCR amplification and sequencing. Drug susceptibility of Staphylococcus aureus ATCC43300 was performed using the VITEK2 compact system. The chemical fingerprint of Rhizoma coptidis was investigated using HPLC and preparative liquid chromatography, and the anti-MRSA activity was determined using an improved broth microdilution method. RESULTS： The drug susceptibility test revealed that the penicillin-binding protein phenotype of the strain changed in comparison to penicillin-sensitive Staphylococcus aureus. Ten batches of Rhizoma coptidis showed anti-MRSA activity on the norA-negative Staphylococcus aureus strain, as well as the strain that contained a norA gene. The spectrum-effect relationship revealed that the berberine alkaloids were the effective components, within which berberine, coptisine, palmatine, epiberberine,, and jatrorrhizine were the major components. CONCLUSION： This study lays a foundation for in vivo studies of Rhizoma eoptidis and for the development of multi-component drugs.

Analysis of Antibiotic Resistance of Escherichia coli Isolated from Pets

[ Objective] This paper aimed to understand drug resistance of Escherichia coli isolated from pets in Guangzhou. I Method ] Broth microdilution method was used to determine the minimal inhibitory concentration （MIC） of ceftiofur, enrofloxacin and other 11 kinds of antibiotics for antimicrobial agent susceptibility testing of 120 strains of clinical E. coli and the experimental data were processed by WHONET 5.4 software. Based on the results of drug resistance pattern analysis, it helped to analyze and study the resistance mechanism. EResultl Clinical E. coli isolated from pets showed a different drug resistance to the 13 kinds of veterinary clinical antibiotics, and the different sources of E. coli also showed a different drug resistance pattern.[Cenclmion] The study provided a theoretical basis for the clinical use of drugs and druq resistance surveillance.

Wild-type MIC Distribution and Epidemiological Cut-off Value and Resistant Characteristics of Colistin Against Escherichia Coli from Chickens

The aim of the present study was to investigate minimum inhibitory concentration(MIC)distributions by broth microdilution(BMD)method and to determine the preliminary epidemiological cut-off value(ECV)of colistin by epidemiological cut-off(ECOFF)finder against E.coli from chickens in China.Anal swabs were collected from chicken farms in China.BMD method was used to measure MIC50 and MIC90 of colistin which were 2 and 4μg•mL^(-1),respectively.MIC frequency distributions for colistin were used to estimate preliminary ECV(8μg•mL^(-1)).High percentages of resistance to ampicillin(94.12%),nalidixic acid(94.12%),enrofloxacin(94.12%),tetracycline(94.12%),ciprofloxacin(88.24%),florfenicol(88.24%),neomycin(64.71%),gentamicin(58.82%),levofloxacin(58.82%),doxycycline(88.24%)and cefalexin(76.47%)were found.In addition,low percentages of resistance to amikacin(5.88%),spectinomycin(17.65%)and fosfomycin(41.18%)were noted.Notably,amoxicillin,sulfisoxazole and trimethoprim resulted in a 100%resistance generation efficacy rate.Prevalence of mcr-1 in E.coli(9/17)in chromosomal DNA was higher than mcr-4(2/17)gene,and mcr-1(5/17)was higher than mcr-4(3/17)in plasmid.