Occurrence and antibiotic resistance of enterococci isolated from olive rhizosphere in arid regions

摘要

Soil is characterized by a high microbial diversity. Indeed, the close relationship of this matrix with plants, animals and humans makes it a source of a great diversity of bacteria with different biochemical and physiological traits. A collection of 64 enterococci was isolated from 31 olive rhizosphere samples from arid regions in Tunisia. Standard biochemical characterization, confirmed by molecular identification based on the species-specific PCR and 16S rRNA gene sequencing, showed the prevalence of Enterococcus feacium (97%) versus Enterococcus durans (3%). Sensitivity to 11 antibiotics, evaluated according to the "CLSI 2010" criteria, showed a high level of resistance to sulfonamides (100% for trimethoprim-sulfamethoxazole) and fluoroquinolones (48.5 % for ciprofloxacin). However, these isolates showed low resistance to tetracycline (12.5 %), vancomycin (6%) and macrolides (4.7 % for erythromycin). This resistance was confirmed by measuring the minimum inhibitory concentration (MIC).