Antibiotics incorporation in Artemia franciscana nauplii, metanauplii, juveniles and adults, and their inhibitory action on Aeromonas hydrophila bacteria

Resumo

The crustacean Artemia franciscana has been used as a drug carrier, mainly in its nauplius stage; however, the use of other developmental stages, i.e., metanauplius, juvenile, and adult, potentially allows treating diseases not only in fry but also in juveniles and adults. In the present work, we studied the incorporation of antibiotics in these stages to inhibit the growth of the bacterium Aeromonas hydrophila, which causes a high mortality in freshwater fishes. The antibiotics used were: chloramphenicol (base antibiotic), nitrofurantoin (Macrodantina®, 50 mg capsules) and ciprofloxacin (Ciproflox®, 250 mg capsules). Four wells were made in Petri dishes with Trypticase® soybean agar (TSA) and 2 mL of bacterial inoculum. The wells were used for each antibiotic and one for the control. A 1- mL sample of each Artemia stage, incorporated with an antibiotic, was placed in each well and incubated for 24 h at 37°C, measuring the inhibition halos thereafter. Results indicated that 4 h are needed for the nauplii to become saturated and for the metanauplii, juveniles, and adults to fill their digestive tract with the antibiotic. In nauplii, the three antibiotics produced inhibition halos; in metanauplii, ciprofloxacin produced the best result (22.57 mm); in juveniles, chloramphenicol (38 mm) and ciprofloxacin (33 mm) gave the best results; in adults, the best results were obtained also with chloramphenicol (33 mm) and ciprofloxacin (40 mm). Nitrofurantoin did not yield positive results in metanauplii, juveniles, and adults, and because it is soluble in water, it is recommended to apply it in lipidic solutions to ease its incorporation. Results from this study allow us to establish the bases for the control and treatment of infectious diseases caused by the bacterium Aeromonas hydrophila through the use of commercial antibiotics, easily available in Mexico.