Abstract
The pathogenic strains of Salmonella typhi, paratyphi, and typhimurium are the major cause of typhoid and food poisoning in children and adults in developing countries. According to WHO estimation, 22 million cases of typhoid fever and 200,000 related deaths occur worldwide each year with an additional 6 million cases of paratyphoid fever estimated to occur annually with the highest incidence in children, resulting in a high death rate. The high use of antibiotics has also given rise to drug-resistant strains. Hence, it was of importance to assess the inhibition and quick detection of pathogenic strains of Salmonella. This study aims to investigate the chemically synthesized gold nanoparticles (GNPs) for its antibacterial activity against clinical isolates of S. typhi and S. paratyphi including food sample isolates. The GNPs were characterized using visible color change, UV-Vis spectrophotometry, FTIR, XRD, DLS, FESEM, TEM, and zeta potential. The plasmon peak at 525 nm and 535 nm confirmed the synthesis of gold nanoparticles. The size of the chemically synthesized gold nanoparticles (GNPs) were in the range of 40-60 nm, while FESEM and TEM images revealed that the GNPs were spherical in shape. For antimicrobial activities, five of the Salmonella strains were isolated from fish and egg samples, while the other seven were S. typhi and S. paratyphi from clinical samples. The inhibition factor for GNPs showed higher inhibition against S. paratyphi, while the inhibition factor for S. typhi were found to be higher than Ciprofloxacin-30. This is the first study of the antibacterial efficacy of GNPs against pathogenic strains of Salmonella. The obtained results suggest that nanobioconjugated gold may be of interest in the detection of typhoid and high potential use in areas in biomedicine as an alternative to antibiotics.
Highlights
The Salmonella spp. are enteric human pathogenic bacteria hazardous to the public health
This work is aimed at fabricating gold nanoparticles (GNP) using a low-cost approach, and its various characterizations were done first by visualization of physical color change and by UV-Vis, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), field emission scanning electron microscope (FESEM), TEM, Dynamic Light Scattering (DLS), and zeta potential
In the Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) slants in Figure 2, the organism produced black colonies confirming the absence of Vibrio cholera in the isolates as reported earlier in the literature [50]
Summary
The Salmonella spp. are enteric human pathogenic bacteria hazardous to the public health. All noble metals have some potent antimicrobial activity, silver nanoparticles show significant ability to inhibit the growth of microorganisms and the literature has numerous reports on their therapeutic potentials [1,2,3]. Silver NPs have been reported to have microbial inhibition against Salmonella strains (Salmonella typhi and Salmonella paratyphi) [4]. A green synthesis of silver NPs has been demonstrated to have antibacterial activity against Salmonella typhimurium [5]. It has been further demonstrated that Salmonella growth is greatly inhibited by a synergistic antibacterial activity achieved by combining silver NPs with antibiotics [6]. It has been reported that the resistance of various enteric human pathogenic bacteria against many synthetic drugs is being enhanced day by day [7]. According to the earlier published results of the antimicrobial activity of Journal of Nanomaterials
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