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Investigation of Microbiological Spoilage and Demonstration of the Anti-bacterial Activity of the Major Imported Fruits Within Dhaka Metropolis

Farahnaaz Feroz
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Rashed Noor
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Jannatun Tahera
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Kamal Kanta Das
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Jessica Das Senjuti
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Abstract/ Executive Summary:

With a previous observation of the in vitro anti-bacterial traits posed by both local and imported fruit alcoholic extracts, present study further endeavored principally to chalk out such properties of the imported fruit blends without alcoholic extraction. Experiments regarding microbiological load demonstrated the prevalence of huge number of total viable bacteria (~107 cfu/g) as was also observed in the earlier research while the fungal load was nominal. Among the pathogenic bacteria, Pseudomonas spp. was found to be more prevalent, closely followed by staphylococcal proliferation. The study of anti-bacterial activity revealed that guava, apple and malta samples possessed strong anti-bacterial traits while the dragon fruit samples exhibited least activity and the orange samples were found with moderate anti-bacterial activity. On the basis of our earlier results, the findings of the current study thus put forward a comparison among the alcoholic extracts and the crude fruit blends.

Keywords: Fresh fruits; Microorganisms; Consumer safety; Anti-bacterial activity

Location: Department of Microbiology, Stamford University Bangladesh

Start Date:

End Date:

Program Area: Food Safety and Security

Commodity: Guava

Objectives:

1. To investigate the probability of the existence of the anti-bacterial activity of the crude blends of commonly imported fruits.

Methodology:

Sampling and sample processing. Imported samples of five types of fresh fruits including Guava (Psidium guajava), malta (Citrus sinensis), apple (Malus domestica), orange (Citrus reticulate) and dragon fruits (Hylocereus polyrhizus) were randomly collected from super shops within the city of Dhaka, Bangladesh. Samples were collected early in the morning and transported quickly to the laboratory according to the standard method. Microbiological analyses were carried out according to standard procedures as described earlier. Briefly 10 g of each fruit sample was homogenized with 90 ml normal saline and serial dilutions were prepared up to 10-6. Quantification of microorganisms. For the enumeration of total viable bacteria (TVB) and fungi, 0.1 ml of each sample from the dilutions 10-3 and 10-5 was spread onto the nutrient agar (NA) and Sabouraud’s dextrose agar (SDA) plates, respectively. The NA plates were incubated at 37⁰C for 24 hours and the SDA plates were incubated at 25⁰C for 48 hours. For the estimation of specific bacterial pathogens, 0.1 ml from each of the 10-3 and 10-5 dilutions of all samples were spread onto the membrane fecal coliform (MFC) agar and MacConkey agar for the enumeration of total fecal coliform (TFC), and coliforms (i.e., Escherichia coli and Klebsiella spp.), followed by incubation at 44.5⁰C and 37⁰C for fecal coliform and coliforms, respectively for 24 hours. Likewise, Staphylococcus spp. was isolated by spreading 0.1 ml of the diluted samples onto the mannitol salt agar (MSA). The plates were incubated at 37⁰C for 24 hours. For the isolation and quantification of Salmonella, Shigella, and vibrio spp., the enrichment procedure was applied as described earlier. For this purpose, after completing homogenization, 1 ml of samples were transferred into 9 ml of selenite cysteine broth (SCB) and alkaline peptone water (APW) for the enrichment of Salmonella, Shigella, and vibrio spp., consecutively and incubated at 37⁰C for 4-6 hours. An aliquot of 0.1 ml of each of the sample from 10-3 and 10-5 dilutions were spread onto Salmonella-Shigella (SS) agar and thiosulfate citrate bile salt sucrose (TCBS) agar for the isolation of Salmonella spp. and Shigella spp., and Vibrio spp., consecutively. Followed by incubation at 37⁰C, the appearance of typical colonies (if any) was noticed within for 24-48 hours. Finally, a series of biochemical tests were conducted to confirm the identity of all the isolates as described previously. Determination of anti-bacterial activity. Determination of anti-bacterial activity was performed by using the agar well diffusion method as previously described. Culture suspensions of 9 laboratory bacterial strains (Bacillus spp., Pseudomonas spp., Vibrio spp., Escherichia coli, Klebsiella spp., Staphylococcus spp., Listeria spp., Salmonella spp., and Aeromonas spp.) were prepared in normal saline equivalent with the turbidity of the McFarland standard. Each of the test bacterial lawn was made by separately spreading evenly over the separate Muller-Hinton agar (MHA). Wells with volumes of 8 mm³ were made through the MHA. Each of the crashed fruit blends (100 μl) was added to the wells along with the disc of gentamicin 10µg as the positive control and an aliquot of 100 µl normal saline was used as the negative control. After drying the plates were then incubated at 37 °C for 12-18 hours. Presence of clear zone (if any) around the samples was analytical for the existence of the anti-bacterial traits of the samples studied.

Source of Information: Stamford Journal of Microbiology, December 2014. Vol. 4, Issue 1, p. 1-4; ISSN: 2074-5346

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Microbiological profile along with anti-bacterial traits of five selected imported fruit samples presented through this study would be suggestive enough to find out possible way to prevent food borne illness and as well as encourage the consumption of fresh fruits which produces secondary metabolite having anti-bacterial properties. Thus our studies on the microbiological contamination extent within the common fruits along with the anti-bacterial traits of the samples studied would be informative in the light of natural preventive strategies against food borne diseases as well as for the overall consumer safety.

Knowledge Management: Journal