Silver Nanocomposite Biosynthesis: Antibacterial Activity against Multidrug-Resistant Strains of Pseudomonas aeruginosa and Acinetobacter baumannii

Bacterial resistance is an emerging public health issue that is disseminated worldwide. Silver nanocomposite can be an alternative strategy to avoid Gram-positive and Gram-negative bacteria growth, including multidrug-resistant strains. In the present study a silver nanocomposite was synthesized, using a new green chemistry process, by the addition of silver nitrate (1.10(-3) molL(-1)) into a fermentative medium of Xanthomonas spp. to produce a xanthan gum polymer. Transmission electron microscopy (TEM) was used to evaluate the shape and size of the silver nanoparticles obtained. The silver ions in the nanocomposite were quantified by flame atomic absorption spectrometry (FAAS). The antibacterial activity of the nanomaterial against Escherichia coli (ATCC 22652), Enterococcus faecalis (ATCC 29282), Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 25923) was carried out using 500 mg of silver nanocomposite. Pseudomonas aeruginosa and Acinetobacter baumannii multidrug-resistant strains, isolated from hospitalized patients were also included in the study. The biosynthesized silver nanocomposite showed spherical nanoparticles with sizes smaller than 10 nm; 1 g of nanocomposite contained 49.24 mu g of silver. Multidrug-resistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii, and the other Gram-positive and Gram-negative bacteria tested, were sensitive to the silver nanocomposite (10-12.9 mm of inhibition zone). The biosynthesized silver nanocomposite seems to be a promising antibacterial agent for different applications, namely biomedical devices or topical wound coatings.