Research Article Comparative Study on the Synergistic Action of Differentially Synthesized Silver Nanoparticles with -Cephem Antibiotics and Chloramphenicol Neethu Hari, 1 Tincy K. Thomas, 2 and A. Jayakumaran Nair 2 1 Centre for Nanoscience and Nanotechnology, University of Kerala, Kariavattom Campus, hiruvananthapuram, Kerala 695581, India 2 Department of Biotechnology, University of Kerala, Kariavattom Campus, hiruvananthapuram, Kerala 695581, India Correspondence should be addressed to A. Jayakumaran Nair; ajayakumarannair@gmail.com Received 31 July 2014; Revised 27 October 2014; Accepted 27 October 2014; Published 13 November 2014 Academic Editor: Mingwang Shao Copyright © 2014 Neethu Hari et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Synergistic activity of cephem antibiotics with silver nanoparticles (Ag NPs) was investigated. Silver nanoparticles were synthesized through biological and chemical method. he combined action of -lactam cephem antibiotics with both green and chemically synthesized silver nanoparticles enhances the antibacterial activity against wide range of antibiotic resistant pathogens and making them applicable to medical devices and microbial control systems. Synergistic activity of chloramphenicol with silver nanoparticles was also studied. 1. Introduction Beta-lactam antibiotics (penams and cephems) are the largest group of antibiotics widely used in clinical medicine because of their high antibacterial activity [1]. -Lactam groups of compounds are the most successful example of natural product application and chemotherapy [2]. All the natu- ral and semisynthetic derivatives of -lactam have their own properties and wide range of applications. Cephem derivatives are one of the new groups of -lactam antibi- otics with cephem ring and they show potent activity against diferent types of bacteria. Cephem class includes cephalosporins and cephamycins of which more than 22 antibiotics are now in clinical use and the eicacies of these drugs depend on their antibacterial spectra, potencies, and concentrations in tissues. But the empirical therapy and extent use of these agents have caused the development of bacterial resistance by diferent mechanisms like production of diferent kinds of -lactamases (-lases), alteration of the antibiotic target site, and prevention of access of the antibiotic to the target by way of altered permeability or forced elux and this may compromise the potential of - lactam antibiotics. In this regard, considerable attention has been given to silver nanoparticles (Ag NPs), which have well-known antimicrobial properties and are used extensively in various medical and general applications and also the antibacterial, antifungal, and antiviral properties of silver ions, silver compounds, and silver nanoparticles have been extensively studied [3]. Moreover, high surface to volume ratio of silver nanoparticles may contribute to their enhanced antimicrobial properties by increasing the contact surface of silver nanoparticles with the microorganisms. Several studies also suggest that silver nanoparticles, which are well known to have broad spectrum antimicrobial activity against bacteria, virus, and eukaryotic microorganisms [4], interact with the cell membrane and some of them will penetrate the bacterial cell wall, thereby causing the death of bacteria [5, 6] Synergistic action is now commonly used to describe an interaction of two antimicrobial agents or occasionally more than two [7], in which the efect produced by the drugs in combination is greater than the sum of their individual efects when the antibiotics are used alone [8]. In another study, Vivekanandan et al. proposed that the silver nanoparticles have the ability to destroy the stability of lipopolysacchrides allowing increase in permeability of outer membrane and Hindawi Publishing Corporation Journal of Nanoscience Volume 2014, Article ID 201482, 8 pages http://dx.doi.org/10.1155/2014/201482