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Articles by Monzur Morshed Ahmed
Total Records ( 5 ) for Monzur Morshed Ahmed
  Md. Fakruddin , Sumaiya Islam , Monzur Morshed Ahmed , Abhijit Chowdhury and Md. Mahfujul Hoque
  Lack of reliable and rapid method for detection of pathogens from shrimp in Bangladesh is an obstacle in ensuring the microbiological quality of the shrimp before export. Salmonella sp. and Vibrio parahaemolyticus are two potential pathogen for shrimp export value chain in Bangladesh. The objective of this study was to establish a multiplex polymerase chain reaction method for rapid and simultaneous detection of Salmonella spp. and Vibrio parahaemolyticus from export oriented shrimp samples. The targeted genes were tdh for V. parahaemolyticus and sefA for Salmonella spp. The genomic DNA was extracted and amplified for subsequent profiling. Validity of the multiplex PCR assay was tested by artificially inoculating the shrimp homogenate with viable cells of target pathogens. The genes were successfully amplified individually and simultaneously both from natural and spiked samples. Sensitivity of the assay was determined to be as low as 104 CFU mL-1. Amplification of DNA extracted from other bacterial pathogens viz. Bacillus cereus, Shigella flexneri and Staphylococcus aureus yielded negative results. This multiplex PCR assay will provide specific, rapid and reliable results and allow for the cost effective detection of target pathogens in a single reaction tube in mixed bacterial communities that are prevalent in shrimp products.
  Md. Fakruddin , Md. Mizanur Rahaman , Md. Nur Hossain and Monzur Morshed Ahmed
  Background and Objective: Cronobacter sakazakii considered to be an important human pathogen and has been increasingly linked to food-borne illness. This study aimed to investigate the fate of C. sakazakii in lake water under low temperature and to evaluate the potential hazard of viable but nonculturable (VBNC) cells induced under such stressful conditions. Methodology: A laboratory strain of Cronobacter sakazakii was induced into VBNC state at low temperature in water microcosm and resuscitation and virulence gene was examined. Effect of growth phase and inoculum level on induction into VBNC was determined. Results were analysed by student’s t-test. Results: Results suggested that C. sakazakii strain can enter into VBNC state at low temperature. Growth phase and inoculum level has no effect on induction of VBNC. The VBNC forms of the strain examined can be resuscitated by temperature upshift and addition of catalase. The VBNC C. sakazakii strain showed the potential to retain virulence. Virulence gene expression and alteration of protein secretion was observed during VBNC state. Conclusion: It is concluded that under some stress conditions, Cronobacter sakazakii can not only enter into VBNC state but also retain virulence and resuscitation potential. This study will help researchers to explore mechanisms of survival and virulence of the pathogen in food value chain. Understanding these mechanisms may pave the way to device new control strategies.
  S.M. Ahsan Habib , A.N.M. Fakhruddin , Shamima Begum and Monzur Morshed Ahmed
  Optimum incubation period, temperature and pH for production of extracellular alkaline protease production by novel bacterium Halobacterium sp. AF1 were investigated. The protease were also characterized for its stability on various environmental conditions. Extracellular thermo-alkaline activity was determined by measuring proteolytic activity of the culture supernatants and stability of the protease was determined by incubating protease under different environmental conditions. The optimum production of AF1 protease was achieved within 72 h of culture at 40°C with the pH 8. The activity of the protease produced by this organism was stable up to 91% at 70°C and 83% at pH 9.5. AF1 protease was not only stable in the presence of organic solvent (25% v/v) but also exhibit a higher activity for acetone and n-hexane than in the absence of solvents. These results suggested that the protease produced by the organism was thermo-stable organic solvent tolerant extracellular alkaline protease. The remarkable stability was found for 5 mM Ca+2, Na+, Hg+2 and Fe+3 as they had been showed marginal effect on proteolytic activity of isolated protease. The AF1 protease was retained their activity up to 57-67% for 1.5% sodium dodecyl sulfate and H2O2. Higher proteolytic activity was found for gelatin (1% w/v) than that of casein or bovine serum albumin. The AF1 protease exhibited excellent stability towards temperature, pH, organic solvents and metal ions. These properties make it suitable to be used in tannery industrial applications as well as detergent additive which reduce the industrial use of chemicals wastes in the environment.
  Shuva Bhowmik , Sumaiya Islam , Monzur Morshed Ahmed , M. Belal Hossain and Md. Abul Hossain
  Proteases, the group of enzyme with significant commercial value, was isolated from proteolytic bacteria available in gut of tiger shrimp (Penaeus monodon). The isolation of bacteria from the gut of the collected shrimp was performed by serial dilution and plating method. Six bacterial isolates were screened out on the basis of their formation of zone of casein hydrolysis on skim milk agar. Among the six isolates, three isolates (S1, S3 and S5) were found gram positive and the rest three isolates (S2, S4 and S6) were found gram negative. Protease activity of the isolates was determined both qualitatively and quantitatively. In qualitative plate assay, isolate S1 exhibited the largest clear zone (30±1.13 mm) in skim milk agar and isolate S5 exhibited the lowest (18±1.41 mm). Quantitative protease assay was performed by using azo-casein as substrate. Protease activity of isolates S1, S2, S3, S4, S5 and S6 were found 49.75±2.13, 60.50±1.97, 66.25±2.41, 56.25±1.69, 59.25±1.32 and 52.75±2.21 U mL-1, respectively following incubation at 37°C in aerobic condition for 24 h. The effect of pH and NaCl concentration on the growth and protease production of the isolates were also studied by assaying protease activity at different pH range and NaCl concentrations. The isolates exhibited maximum protease production at varying pH and NaCl concentrations. The data showed potentiality of the bacterial isolates to be a useful source of industrial protease. Finally, the isolates were also tested against six standard antibiotics (Tetracycline, Nitrofurantoin, Erythromycin, Penicillin, Ciprofloxacin and Doxycycline) to observe their antibiotic sensitivity and the isolates S5 and S6 were found resistant to all of the six antibiotics and isolates S3 and S4 were found sensitive to all of the antibiotics.
  M.D. Fakruddin , Mahmuda Sultana , Monzur Morshed Ahmed , Abhijit Chowdhury and Naiyyum Choudhury
  The coastal aquaculture mainly shrimps constitute major export sector in Bangladesh and is increasingly shaped by international trade conditions and by national responses to those stringent quality and safety standards. PCR based validated methods for detection of major bacterial pathogens in shrimp might be very useful tool for ensuring quality and safety standards of exportable shrimps. The objective of this study was to evaluate overall performance (sensitivity and specificity) of the multiplex PCR assay for detection of Vibrio cholerae, Vibrio parahaemolyticus, Salmonella sp. and Escherichia coli O157:H7 from spiked shrimp samples. The targeted genes were ompW for V. cholerae, tdh for V. parahaemolyticus, sefA for Salmonella spp. and hlyEHEC for E. coli O157:H7. The genomic DNA was extracted by using standard method and amplified accordingly. Sensitivity of the assay was tested by inoculating the shrimp homogenate with viable cells of laboratory references strains (target pathogens). The genes were amplified individually both from culture homogenate and spiked samples. Twenty different uniplex and multiplex PCR assay were performed; the results showed that the sensitivity and specificity of multiplex PCR are comparable to that of the results of uniplex PCR for the samples. DNA extracted from shrimp samples spiked with non-target pathogen (Bacillus cereus, Shigella flexneri and Staphylococcus aureus) yielded negative results.
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