Identification Of Fungi Isolated From Clinical Wastes And Inactivation Of Fungal Spores By Using Supercritical Carbon Dioxide
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Date
2016-08
Authors
Mohammed, Efaq Ali Noman
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Abstract
Clinical wastes are considered as a serious infectious source to humans due to the existence pathogenic microorganism such as bacteria, virus and fungi. For the treatment of clinical wastes, chemical disinfection and irradiations methods including UV are commonly used, however, these treatment methods are unable to destroy pathogens completely. Incineration is not a suitable technology for the treatment of clinical wastes due to the inevitable production of hazardous pollutants (dioxins and furans). The present study deals with the identification and inactivation of fungal species present in clinical waste samples collected from health care unit; the Wellness Centre of USM, Malaysia. The inactivation of the most common pathogens (fungal spore) were carried out using an advanced non-thermal alternative technology; supercritical carbon dioxide (SC-CO2) for safe handling of clinical wastes. In this regards, 150 fungal isolates were identified from 92 clinical waste samples and cultured on V8A medium. The fungal isolates were purified using single spore technique and identified by phenotypic method. The morphological characterization of fungal spore were performed by using scanning electron microscope (SEM) analysis. On the basis of phenotypic analysis fungal isolates were classified in 8 genera and 36 species. Among all isolates, Aspergillus spp. in section Nigri (10%), A. niger (9.3%), A. fumigatus (8.7%), P. simplicissium (8%), A. tubingensis (7.3%), A. terreus var. terreus (6.6%), P. waksmanii (6%) and C. lunata (6%) were the most frequently found. It was also observed that among five sections
of the Wellness Centre, the clinical wastes collected from diagnostic labs of Haematology Section showed the highest numbers of fungal species (29). Glove wastes also demonstrated the highest number of fungal species (19) among seventeen types clinical wastes screened. Among all fungal species, Aspergillus spp. exhibited higher growth rate at 37˚C than at 28˚C, indicating the ability of these opportunistic fungi to cause diseases in human. The inactivation of fungal spores using SC-CO2 was investigated at 30-40 MPa, 35-75 ˚C for a time period of 30-90 min and optimized by response surface methodology (RSM). A. niger was used as biological indicator with initial concentrations of 6 log as determined by haemocytometer counts and culture based technique. The efficiency of SC-CO2 in the inactivation of fungal spores was determined in terms of log reduction and inactivation percentage. The optimal inactivation of spore was determined at 35 MPa, 75˚C in 90 min which showed the predicted and experimental reductions as 5.93 and 6 log, respectively with 99.9999% of inactivation. It was also found that after treatment the samples by SC-CO2, no regrowth was observed. At the optimal condition of SC-CO2, the spores of the most common fungal species were completely inactivated (6 log reduction). The attractions of the inactivated fungal spores were examined using SEM analysis which revealed that after SC-CO2 treatment, the cell wall of fungal spore was completely damaged (burst) and deformed as compared to steam autoclaved and untreated ones. The plate assay study revealed that the inactivated fungi spores did not produce any extracellular enzyme. In conclusion, clinical wastes have high contents of opportunistic fungi, which might cause several diseases in human being. This study significant in proving that SC-CO2 as an advanced non thermal method is capable in inactivating fungal species found in clinical wastes, hence reducing the health risks during the handling of these clinical waste thus making it safer.
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Identification and inactivation of fungal species present in , clinical waste samples collected from health care unit