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In the present study, a yeast species isolated from CETP, Vellore, Tamilnadu was identified as Cryptococcus sp. VITGBN2 based on molecular techniques and was found to be a potent producer of acidic diacetate sophorolipid in mineral salt media containing vegetable oil as additional carbon source. The chemical structure of the purified biosurfactant was identified as acidic diacetate sophorolipid through GC-MS analysis. This sophorolipid was used as a stabilizer for synthesis of zinc oxide nanoparticles (ZON). The formation of biofunctionalized ZON was characterized using UV-visible spectroscopy, XRD, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The antimicrobial activities of naked ZON and sophorolipid functionalized ZON were tested based on the diameter of inhibition zone in agar well diffusion assay, microbial growth rate determination, protein leakage analysis, and lactate dehydrogenase assay. Bacterial pathogen Salmonella enterica and fungal pathogen Candida albicans showed more sensitivity to sophorolipid biofunctionalized ZON compared with naked ZON. Among the two pathogens, S. enterica showed higher sensitivity towards sophorolipid biofunctionalized ZON. SEM analysis showed that cell damage occurred through cell elongation in the case of S. enterica, whereas cell rupture was found to occur predominantly in the case of C. albicans. This is the first report on the dual role of yeastmediated sophorolipid used as a biostabilizer for ZON synthesis as well as a novel functionalizing agent showing antimicrobial property.

Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), is an important cause of pyogenic skin and soft tissue infections (SSTIs). MRSA is an important pathogen in the healthcare sector that has neither been eliminated from the hospital nor community environment. In humans, S. aureus causes superficial lesions in the skin and localized abscesses, pyogenic meningitis/encephalitis, osteomyelitis, septic arthritis, invasive endocarditis, pneumonia, urinary tract infections and septicemia. Investigations focused in the search of other alternatives for the treatment of MRSA infections are in progress. Among the range of compounds whose bactericidal activity is being investigated, ZnO nanoparticles (ZnO-NPs) appears most promising new unconventional antibacterial agent that could be helpful to confront this and other drug-resistant bacteria. The aim of present study is to investigate the antibacterial potential of ZnO-NPs against Staphylococcus species isolated from the pus and wounds swab from the patients with skin and soft tissue infections in a tertiary care hospital of north India. ZnO-NPs (≈19.82 nm) synthesized by sol-gel process were characterized using scanning electron microscopy, X-ray diffraction , and Atomic force microscopy. The antibacterial potential was assessed using time-dependent growth inhibition assay, well diffusion test, MIC and MBC test and colony forming units methods. ZnO-NPs inhibited bacterial growth of methicillin-sensitive S. aureus (MSSA), MRSA and methicillin-resistant S. epidermidis (MRSE) strains and were effective bactericidal agents that were not affected by drug-resistant mechanisms of MRSA and MRSE.

The reemergence of infectious diseases and the continuous development of multidrug resistance among a variety of disease-causing bacteria in clinical setting pose a serious threat to public health worldwide. Extended-spectrum β-lactamases (ESBLs) that mediate resistance to third-generation cephalosporin are now observed all over the world in all species of Enterobacteriaceae, especially Escherichia coli and Klebsiella pneumoniae. In this work, ZnO nanoparticles (NPs) were synthesized by the sol-gel method and characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The image of synthesized ZnO NPs appeared spherical in SEM with a diameter of ≈19 nm and as hexagonal crystal in AFM. Clinical isolates were assessed for ESBL production and shown to be sensitive to ZnO NPs by different methods such as minimal inhibitory concentration (MIC) and minimal bactericidal concentration, time-dependent growth inhibition assay, well diffusion agar methods and estimation of colony forming units (CFU) of bacteria. The lowest MIC value for E. coli and K. pneumoniae was found to be 500 μg/ml. The results showed that ZnO NPs at 1,000 μg/ml completely inhibit the bacterial growth. The antibacterial effect of ZnO nanoparticles was gradual, but time- and concentration-dependent. The maximum inhibition zone at100 μg/ml for E. coli and K. pneumoniae was 22 and 20 mm, respectively. With the increasing ZnO NP loading, there is significant reduction in the numbers of CFU. At the concentration of 1,000 μg/ml, the decline in per cent survival of E. coli and K. pneumoniae was found to be 99.3% and 98.6%, respectively.