Novel linear plasmids carrying vanA cluster drives the spread of vancomycin resistance in Enterococcus faecium in India.

OBJECTIVES: The genetic basis for the spread of vancomycin resistance in Enterococcus faecium is largely unexplored in India. The present study aimed to investigate the plasmid diversity and variation of Tn1546 associated with vanA harbouring VREfm isolates. METHODS: A total of 122 VREfm isolates collected from blood cultures were included in this study. MLST analysis was performed on all isolates, and they were also screened for the presence of vanA and vanB genes. Whole genome sequencing was performed for a subset of fifteen VREfm isolates belonging to ST1643. RESULTS: All of the 122 VREfm isolates carried the vanA gene. Twenty-four different sequence types were seen; of these, ST1643, ST80 and ST17 were predominant. Whole genome sequencing was performed on 15 VREfm isolates belonging to ST1643. For eight isolates the vanA gene was found on pRUM-like circular plasmids, and for the remaining seven isolates, the vanA gene was found on the linear plasmids. Novel Tn1546 variants carrying vanA were found on both circular and linear plasmids. Interestingly, co-presence of vanA and optrA were seen in the backbone of three linear plasmids. CONCLUSION: Multiple vanA-carrying plasmids and Tn1546-like elements were involved in the dissemination of vancomycin resistance in VREfm. The co-occurrence of Tn1546 carrying vanA and Tn554 family transposon carrying optrA on the backbone of plasmids is worrisome. The dissemination of such plasmids may pose treatment and infection control challenges.

Biosynthesis of silver nanoparticles using red algae Portieria hornemannii and its antibacterial activity against fish pathogens.

In the present study, red algae Portieria hornemannii was scrutinized for the productive synthesis of silver nanoparticles. These biosynthesized nanoparticles were characterized by visible color change and ultraviolet visible spectrophotometry that indicated the formation of nanoparticles at the absorbance of 418 nm. Fourier transforms infrared spectroscopy, X-ray Diffraction analysis was further carried out to study the functional groups and crystalline nature of the substance. Scanning electron microscopy and Transmission electron microscopy exposed the shape of the silver nanoparticles, which was found to be spherical. Energy dispersive X-ray spectroscopy confirmed the presence of the metal silver. Stability of nanoparticles was analyzed using Zeta potential. The synthesized nanoparticles were found to be active against the fish pathogens Vibrio harveyii, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio anguillarum. The highest activity was found against the pathogens V. harveyii and V. parahaemolyticus. We have established an environmental friendly synthesis of Silver nanoparticles which can be used as an alternative to commercially available antibiotics in the treatment of fish diseases.