Risk assessment of the antibiotic amoxicillin on non-toxin-producing strains and toxin-producing strains of Microcystis.

Amoxicillin (AMX) is a common antibiotic used to treat a variety of infectious illnesses in humans and animals, including otitis media, tonsillitis, tonsillopharyngitis, laryngitis, and pharyngitis. The drug ends up in the aquatic ecosystems through animal and human excretion and industrial effluents. The ecological consequences of broad-spectrum antibiotics on non-target species like cyanobacteria are causing considerable concern. The danger of amoxicillin to non-toxin-producing and toxin-producing strains of cyanobacteria is poorly understood. The objective of this study was to analyze the risk (RQ) and physiological effects of AMX on Microcystis aeruginosa EAWAG 198 (non-toxin producing = NTP), Microcystis aeruginosa LE3 (toxin-producing = TP), and Microcystis flos aquae UTEX-LB 2677 (toxin-producing = TP). Our study showed differences in the RQ of the drug to the tested organisms - demonstrating < Microcystis flos aquae UTEX-LB 2677 > Microcystis aeruginosa LE3 > Microcystis aeruginosa EAWAG 198. The calculated EC50 values show that AMX was more toxic to the toxin-producing strains than the non-toxin-producing strains. Amoxicillin led to significant (p < 0.05) growth inhibition and chlorophyll-a content of the exposed cultures. The observed increase in the concentration of intracellular hydrogen peroxide (H2O2) of the exposed cultures at 96 h was significant (p < 0.05), demonstrating that the expressed oxidative stress patterns observed during the study were due to AMX. The current study shows significant variation (p < 0.05) in melondialdehyde (MDA) content and the antioxidant enzymes - glutathione-S-transferase (GST) and peroxidase (POD).

Immobilization, oxidative stress and antioxidant response of Daphnia magna to Amoxicillin and Ciprofloxacin.

Amoxicillin (AMX) and ciprofloxacin (CPX) are broad-spectrum antibiotics with wide application in agriculture and human and veterinary medicine. The drugs end up in the environment where their impact on zooplankton remains scantily understood. This study investigated the immobilization, risk assessment (RQ), antioxidant response, and biochemical changes of Daphnia magna post-exposure to AMX and CPX. Sixty-percent immobilization of Daphnia occurred at 200 µg L-1 AMX and CPX, while EC50 values were 2391.6 µg L-1 and 273.4 µg L-1, respectively. RQs were 113.3 and 11,481.5, while Toxic units were 41.6 and 364.9 for AMX and CPX, respectively. Both antibiotics caused a significant rise in intracellular hydrogen peroxide 48 h post-exposure, indicating oxidative stress. Lipid peroxidation and antioxidant enzyme activity were considerably altered during the research. Thus, environmentally relevant concentrations of AMX and CPX pose an adverse risk that could change the population dynamics of Daphnia magna.

Effects of the antimalarial lumefantrine on Lemna minor, Raphidocelis subcapitata and Chlorella vulgaris.

Lumefantrine is used to treat uncomplicated malaria caused by pure or mixed Plasmodium falciparum infections and as a prophylactic against recrudescence following artemether therapy. However, the pharmaceutical is released into the aquatic environment from industrial effluents, hospital discharges, and human excretion. This study assessed the effects of lumefantrine on the growth and physiological responses of the microalgae Chlorella vulgaris and Raphidocelis subcapitata (formerly known as Selenastrum capricornutum and Pseudokirchneriella subcapitata) and the aquatic macrophyte Lemna minor. The microalgae and macrophyte were exposed to 200-10000 µg l-1 and 16-10000 µg l-1 lumefantrine, respectively. Lumefantrine had a variable effect on the growth of the aquatic plants investigated. There was a decline in the growth of R. subcapitata and L. minor post-exposure to the drug. Contrarily, there was stimulation in the growth of Chlorella vulgaris. All experimental plants had a significant increase in lipid peroxidation, which was accompanied by an increase in malondialdehyde content. Peroxidase activity of L. minor increased only at low lumefantrine concentrations, while the opposite occurred at higher levels of the drug. Incubation in lumefantrine contaminated medium significantly up-regulated the activity of R. subcapitata cultures. Glutathione S-transferase of L. minor exposed to lumefantrine treatments had substantially higher activities than the controls. Our findings suggest lumefantrine could have adverse but variable effects on the growth and physiology of the studied aquatic plants.