Bacterial strains of genus Vibrio spp. can cause severe mortality as in early death syndrome or acute hepatopancreatic necrosis syndrome. Disinfection is an important and necessary tool for the management and control of diseases in aquaculture farms dedicated to shrimp fattening. Combination of quaternary ammonium salts (QAC) and glutaraldehyde (GLU) are two of the most widely used disinfectants on shrimp’s ponds to maintain low overgrowth of Vibrio spp. The objective of the study was known the in vitro residuality and sanitizing effect of an artificial challenge with Vibrio parahaemolyticus in seawater using different concentrations of a quaternary ammonium and glutaraldehyde commercial combination (QAC+GLU).
Through an experimental study, were compare four treatments with repetitions and measurements of the CFU/mL reduction at different time intervals using an artificial challenge as previously described. QAC+GLU solutions in 1L of sterile water were prepared separately in Erlenmeyer flasks with different concentrations of the commercial product being the low concentration 117 ppm (T1), the medium concentration 334 ppm (T2) and the high concentration 668 ppm (T3) while a nontreated 0 ppm (T0) was include a control . Then a pure culture of an overnight Vibrio parahaemolyticus
(VPH) strain
SO-11 (AHPND) (donated by Dr. Ricardo Sánchez-Díaz, ITSON) was collected to prepare a bacterial suspension adjusting its turbidity to the 0.5 McFarland scale. Then, serial dilution of th is suspension was done and 100 µL
of each dilution was inoculated onto
Petri dishes with TCBS agar. All treatments were challenged at a concentration of 2.82×106 CFU/mL of
VPH. Finally, 100 µl was seeded in each flask and counting for viable bacteria on agar plate at of 0, 24, 48, 72 and 192 hours (h). Variation in QAC concentration was carried out using a colorimetric technique with reactive strip (MQuantTM Merck KGaA) . The concentrations were annotated according to the colorimetric concentration scale and then converted it to ordinal scale score as previously described; the scale was adjusted to values of 0, 1, 2, 3, 4, 5 and 6, having as quaternary ammonium concentration of 0 ppm, 10 ppm, 25 ppm, 50 ppm, 100 ppm, 250 ppm and 500 ppm respectively. The pH of each treatment was measured with the help of a potentiometer and the salinity with a refractometer.
REFERENCES.
1 Lightner 1993. Handbook mariculture vol. 1, CRC: 432.
2 Sung et al., 2003. Aquaculture 219 (1-4): 123-133.