Studies On Minimum Inhibitory Concentration And Mutant Prevention Concentration Of Antibacterial Drugs Against Brucella

Brucellosis is a zoonosis which is caused by Brucella bacteria infection. The antibiotictherapy requires long time treatment that makes it difficult for patients to adhere to themedication; this situation will easily lead to the emergence of drug resistance. In themeanwhile, some patients suffering from brucellosis may have symptoms of other bacterialinfection. Therefore, how to choose antimicrobial agents for the effective treatment ofbrucellosis is a problem which is required to solve immediately. In this study, the separationand identification of bacteria in the blood of brucellosis patients were conducted to diagnosewhether a patient infected by Brucella would have symptoms of other bacterial infections atthe same time. For the purpose of prevention of drug resistance, the minimum inhibitoryconcentration (MIC) and mutant prevention concentration (MPC) for a Brucella bacterialstrain were determined. This work will provide reference for the clinical treatment ofantibacterial drugs in the future.In this article, eight blood samples of brucellosis confirmed cases and suspected casesfrom Siziwangqi Central Hospital in Wulanchabu City and Dakouzi Village were sampled asresearch materials and the bacteria in the blood were separated; the bacterial genomic DNAwas extracted to determine whether the isolated bacteria were the genus of Brucella throughBrucella auele specific primer eri and PCR analysis; The16S rDNA were PCR amplifiedand sequenced. Sequences were compared to the NCBI database, showing that the19strainsof bacteria belonged to9different species, including Bacillus pumilus, Bacillus thuringiensis,Arthrobacter phenanthrenivorans, Bacillus megaterium, Pseudomonas stutzeri, Delftiaacidovorans, Bordetella avium, Brevundimonas subvibrioides and Acinetobacter baumannii.Therefore, blood culture should be carried out first for the drug dosage schedules and for thechoosing types of the drug to be used in the treatment of brucellosis.The MICs of six drugs on Brucella living vaccine S2strain were determined usingCLSI Broth Filution method as follows: gentamicin sulfate0.470μg/mL, kanamycin sulfate1.362μg/mL, the rifampicin1.821μg/mL, streptomycin sulfate1.700μg/mL, tetracycline2.710μg/mL, moxifloxacin0.298μg/mL respectively. Compared with the other five drugs,the fourth generation fluoroquinolone moxifloxacin had the lowest MIC value, indicatingthat it possesses the strongest antimicrobial activity. Among the Aminoglycoside antibioticsdrugs, gentamicin sulfate has the lowest MIC and streptomycin sulfate possesses the highestMIC value. The MPCs and drug resistance selectivity index (SI) on Brucella living vaccine S2strain were determined using the agar dilution method for gentamicin sulfate, kanamycinsulfate, rifampicin, streptomycin sulfate and moxifloxacin. Among the five drugs,moxifloxacin had the lowest MPC value and rifampicin had the highest MPC value;gentamicin sulfate had the minimum SI and rifampin had the highest SI, indicating thatmoxifloxacin and gentamicin sulfate have better ability to prevent emergence of drugresistance mutants than kanamycin sulfate, rifampicin and streptomycin sulfate do. Our datashowed that drugs with the lower MPC values did not necessarily have the lower SI values.Furthermore, antibacterial drugs in the same categories with a similar mechanism of actionmay have different MPC and SI values; thus their MPC and SI values need to be determinedindividually, and the variation of MPC and SI for the drugs should be taken intoconsideration at the same time for choosing antimicrobial agents in clinics.