GENERATION OF BIOLUMINESCENTMORGANELLA MORGANIIAND ITS POTENTIAL USAGE IN DETERMINATION OF GROWTH LIMITS AND HISTAMINE PRODUCTION

Development of a new method for extracting histamine from marine fish flesh using the salting-out technique

A simple and practical method was developed to extract histamine from fish products using sodium chloride (NaCl). After obtaining a saline extract from fish samples, histamine was derivatized by a condensation reaction with ortho-phthalaldehyde. Fluorescence intensity was measured by a fluorimeter. The first part of this work concerned a solid-liquid extraction tested with samples from the food analysis performance assessment scheme. The best histamine extraction yield (97%) was obtained using an extraction time of 4 minutes, a temperature of 40°C, and a NaCl/water ratio of 41% (w/w). The second part focused on a liquid-liquid extraction carried out on standard solutions of histamine (45, 90, and 180 mg/kg). The use of NaCl (41%) and trichloroacetic acid [(TCA) 10%] did not show any significant difference in extraction yield. The yield obtained was 99.15-100.1% for TCA (10%) and 98.65-99.45% for NaCl (41%). The validation criteria (repeatability and reproducibility) were checked by evaluating the reliability of the method. Extraction using NaCl has proven to be an interesting alternative method for the extraction of histamine from fish, as it is reliable, inexpensive, and less hazardous.

Propagation capacity of bacterial contaminants in platelet concentrates using a luciferase reporter system

INTRODUCTION

Currently the use of molecular tools and techniques of Genetic Engineering in the study of microbial behavior in blood components has replaced the employment of classical methods of microbiology. This work focuses on the use of a novel lux reporter system for monitoring the contaminating propagation capacity of bacteria present in platelet concentrates under standard storage conditions in the blood bank.

METHODS

A miniTn5 promotor probe carrying the lux operon from Photorhabdus luminiscens (pUTminiTn5luxCDABEKm2) was used to construct four bacterial bioluminescent mutants: Escherichia coli, Salmonella typhi, Proteus mirabilis and Pseudomonas aeruginosa. Luminescent mutants were used for contamination tests with 20 CFU in platelet concentrates bags and were stored under standard storage conditions in the blood bank (100 rpm at 22 °C). The measurements of luminous activity and optical density were used to monitor bacterial proliferation during 7 days (168 h).

RESULTS

During the exponential growth phase (log) of bacterial strains, a lineal correlation between luminous activity vs biomass was observed (R(2) = 0.985, 0.976, 0.981) for E. coli::Tn5luxCDABEKm2, P. mirabilis::Tn5luxCDABEKm2 and P. auriginosa::Tn5luxCDABEKm2, respectively. The above indicates that metabolic activity (production of ATP) is directly related to biomass in this phase of microbial growth. While conducting experiments, the inability to propagate S. typhi::Tn5luxCDABEKm2 was detected. We can speculate that platelet concentrates contain specific components that prevent the propagation of S. typhi.

CONCLUSION

The use of luxCDABE system for the quantification of luminous activity is a rapid and sensitive alternative to study the propagation and auto-sterilization of bacterial contaminants in platelet concentrates.