Incidence of Aspergillus fungal species in cured fish of Gujarat based on internal transcribed spacer regions 1 and 4

Abstract

Fungal infestations cause quality losses and often pose serious health hazards to the consumers. The sun dried fish samples such as ribbon fish, bombay duck, catfish, horse mackerel, dhoma, leather jacket, prawn and acetes were collected from the dried fish processing facilities and commercial markets from Veraval and Nawabhandar in Gujarat. Ten gram of the fish samples were homogenised in sterile normal saline and serial dilution was made from 10-1 to 10-6 and spread onto a duplicate plate of Rose Bengal Chloramphenicol Agar and incubated at 25 to 30 degree celsius for 5 days. The total fungal counts ranged from 2.0 x 101 to 5.0 x 102 cfu. per gram and the higher counts were frequently seen in the ribbon fish sample. The morphologically distinct colony was streaked on to Sabouraud Dextrose Agar for DNA isolation. The fungal DNA was isolated and purified as per the manufacturer’s guidelines and PCR was carried out with the universal primers for the 18 S gene with the ITS1 and ITS4 regions of 670 bp. The DNA sequences were submitted to the European Nucletide Archives and found that Aspergillus nidulans, Aspergillus oryzae, Aspergillus flavus, Aspergillus sydowii, A. foetidus and Aspergillus rugulosa. The highest similarity was observed between Aspergillus flavus with Aspergillus oryzae and Aspergillus nidulans with Aspergillus rugulosa. The least genetic similarity was found between Aspergillus flavus with Aspergillus rugulosa and Aspergillus oryzae with Aspergillus rugulosa. The phylogenetic tree revealed that two clade were formed among the fungal species with one clade belongs to Aspergillus flavus, Aspergillus rugulosa and Aspergillus sydowii and the another with Aspergillus flavus and Aspergillus oryzae. The present study shows the presence of different pathogenic fungal species which can be from different sources of contamination at various stages of dry fish processing.