Origanum vulgare L. Associated Microbiota conclusion, this study regarded the characterization of O. vulgare L. chemotype and of the bacterial communities associated to this medicinal plant, also allowing the evaluation of antibiotic resistance and antagonistic interactions. This study provided the bases for further analyses on the possible involvement of endophytic bacteria in the production of antimicrobial molecules that could have an important role in clinical and therapeutic applications.
Enterococci are leading causes of nosocomial bacteremia, surgical wound and urinary tract infections. They are ubiquitous bacteria commonly occurring in foods, and in recent years there has been increased attention towards multidrug strains incidence, since they may cause the failure of therapeutic treatments. Therefore, we analyzed the occurrence of Enterococcus species isolated from raw meat (beef, chicken and pork), cheese, and ready-to-eat salads, and the change of the antibiotic resistance in Enterococcus faecium and E. faecalis strains in a 14 year survey. Among the 589 Enterococcus strains, E. faecium and E. faecalis represented the most numerous species in all types of food examined (42.8% and 38.7% respectively). Antibiotic resistance and number of Multi Drug Resistant strains have increased, reaching very high levels from 2002 to 2015. In the last two years, E. faecalis isolates sometimes reached percentages of resistance higher than 40% against tetracycline, vancomycin, linezolid, erythromycin, and ampicillin. Antibiotic resistance in E. faecium was lower than in E. faecalis for almost all antimicrobials tested. The highest percentage of resistance in 2014-2015 was registered for erythromycin (42.5%), followed by tetracycline (30%), ciprofloxacin, and linezolid (both 27.5%). The number of resistant phenotypes also increased during this survey in both species to more than 20 in 2014-2015. Despite the fact that Enterococcus spp. do not represent a problem for immunocompetent individuals, surveillance of antibiotic resistance in this kind of microorganism continues to be important because, as shown in our results, antibiotic resistance has sharply increased in recent years.
Background: Rising of multidrug-resistant human pathogens demands novel antibiotics: to this aim, unexplored natural sources are investigated to find new compounds. In this context, bacteria associated to medicinal plants, including Phragmites australis, might represent an important source of antimicrobial compounds. Materials & methods: In the present work, 21 bacterial endophytes isolated from P. australis roots were tested, through cross-streaking, for their inhibitory activity against 36 multidrug-resistant pathogens isolated from food, clinical patients and hospitals. Results & conclusion: Seven endophytes, belonging to Pseudomonas and Stenotrophomonas, were able to inhibit the growth of most of target strains. In conclusion, this preliminary work could pave the way to the discovery of new antibiotics active against superbugs.
Medicinal plants play an important role in the discovery of new bioactive compounds with antimicrobial activity, thanks to their pharmacological properties. However, members of their microbiota can also synthesize bioactive molecules. Among these, strains belonging to the genera Arthrobacter are commonly found associated with the plant’s microenvironments, showing plant growth-promoting (PGP) activity and bioremediation properties. However, their role as antimicrobial secondary metabolite producers has not been fully explored. The aim of this work was to characterize the Arthrobacter sp. OVS8 endophytic strain, isolated from the medicinal plant Origanum vulgare L., from molecular and phenotypic viewpoints to evaluate its adaptation and influence on the plant internal microenvironments and its potential as a producer of antibacterial volatile molecules (VOCs). Results obtained from the phenotypic and genomic characterization highlight its ability to produce volatile antimicrobials effective against multidrug-resistant (MDR) human pathogens and its putative PGP role as a producer of siderophores and degrader of organic and inorganic pollutants. The outcomes presented in this work identify Arthrobacter sp. OVS8 as an excellent starting point toward the exploitation of bacterial endophytes as antibiotics sources.
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