Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. METHODS Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy. FINDINGS The characteristic UV-visible absorbance peak was observed in the 420-430 nm range. Most of the particles were spherical in shape within a size range of 33-300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans. MAIN CONCLUSION As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

Effect of leather industry effluents on soil microbial and protease activity.

Release of leather industry effluents into the agricultural fields causes indicative changes in nutrient cycling and organic matter processing. In the present study, leather industry effluent discharged soil (test) and undischarged soil (control) were collected from the surrounding areas of industry. The physico-chemical, biological properties and soil protease activity were examined. The study reflected the average mean value of pH, electrical conductivity and water holding capacity of the test soil was found to be 7.94, 0.89 =Mhos cm-1 and 0.51 ml g-1, respectively. In chemical parameters, organic matter, total nitrogen, phosphorus and potassium has the mean of 6.73%, 0.23 g kg-1, 4.28 mg g-1 and 28 =g g-1, respectively. In all the respects, the test soil showed higher values than the control. The soil protease enzyme activity was determined by using substrate casein and the activity was found to be higher (180 =g TE g-1 24 hr-1) in test soil than the control soil (63 =g TE g-1 24 hr-1).

Perinatal mortality--a hospital based study.

A total of 5082 consecutive deliveries in Medical College Hospital, Kottayam during the period August 1992 to July 1993 constituted the study. Perinatal mortality rate (PMR) was 38.5 per 1000 total births and autopsy rate was 72%. More than 85% of perinatal deaths occured in low birth weight and preterm babies. Perinatal hypoxia and congenital anomalies were the leading causes in late fetal deaths (LFD). The main causes of early neonatal deaths (END) were perinatal hypoxia, infections, congenital anomalies and hyaline membrane disease (HMD).