Antibacterial Synergy of Silver Nanoparticles with Gentamicin and Chloramphenicol against Enterococcus faecalis

BACKGROUND: Enterococcus faecalis (Ef) is a multidrug-resistant pathogenic bacteria associated with hospital-acquired infections. Ef is involved in a number of infectious diseases. It generally infects patients with the weekend immune system, i.e. a person mostly acquires Ef infections in the hospital, especially in intensive care units and thus, is more likely to be resistant to many antibiotics. Development of resistance against various antibiotics and emergence of drug-resistant strains is a growing global concern. OBJECTIVE: Due to the unselective use of antibiotics for a long time multidrug resistant bacteria and extensively drug-resistant, which is now posing a new challenge to the medical community. To treat infections caused by Ef, the synergistic effect of different antibiotics with silver nanoparticles (AgNPs) was tested against Ef. MATERIALS AND METHODS: In the present study, synthesis of AgNPs was carried out from the cell-free supernatant of Klebsiella pneumoniae. AgNPs were characterized using various techniques, namely, ultraviolet-visible spectrophotometry, transmission electron microscopy, and Fourier transform infrared spectroscopy. Moreover, process optimization was done for enhanced production of AgNPs. In addition, antimicrobial activity of the nanoparticles was also tested. Furthermore, the nanoparticles were evaluated for their antimicrobial activities in combination with gentamicin and chloramphenicol, against Ef. RESULTS: The results showed that the combination of gentamicin and chloramphenicol with AgNPs has a better antibacterial effect. To add to this, hemolytic activity of AgNPs was evaluated against human red blood corpuscles (RBCs). AgNPs were found to be nontoxic to RBCs. CONCLUSION: The collective effect of AgNps with Gentamicin and Chloramphenicol was more as compared to AgNps alone which indicate the synergistic effect of these components. These observations show the potential of AgNPs in combination with above-stated antibiotics against Ef infections. SUMMARY: Enterococcus faecalis (Ef) is a multidrug-resistant bacteria with is resistant to wide range of antibiotics. Due to this increasing resistance, there is a need to find a new approach to overcome the infections caused by Ef. The combined effect of silver nanoparticles (AgNPs) with gentamicin and chloramphenicol was notably seen against Ef. Furthermore, the AgNPs were nontoxic to the human red blood corpuscles which confirm its nontoxic nature. Abbreviations used: Ef: Enterococcus faecalis, MDR: Multidrug resistance, AgNPs: Silver nanoparticles, Kp: Klebsiella pneumoniae, RBCs: Red blood corpuscles, ENPs: Engineered nanoparticles, FTIR: Fourier transform infrared spectroscopy, TEM: Transmission electron microscopy, AgNO(3): Silver nitrate, EDTA: Ethylenediaminetetraacetic acid, PBS: Phosphate-buffered saline.