Comparing the sensitivity of chlorophytes, cyanobacteria and diatoms to major-use antibiotics

The occurrence of antibiotic residues in the aquatic environment is an emerging concern. In contrast to daphnia and fish, algae are known to be particularly sensitive to antibiotic exposure. However, to date, a systematic evaluation of the sensitivity of different algal species to antibiotics has not been performed. The aim of the present study was therefore to explore the sensitivity of a battery of algal species towards antibiotic exposures. The present study investigated the growth inhibition effects of three major-use antibiotics, tylosin, lincomycin and trimethoprim, on seven algal species from the chlorophyte, cyanobacteria and diatom groups. Based on EC50 values, cyanobacteria (EC50 = 0.095-0.13 µmol/L) were found to be the most sensitive group to lincomycin followed by chlorophytes (EC50 = 7.36-225.73 µmol/L) and diatoms (EC50 >225.73 µmol/L). Cyanobacteria were also the most sensitive group to tylosin (EC50 = 0.09-0.092 µmol/L) but, for this compound, diatoms (EC50 = 1.33-5.7 µmol/L) were more sensitive than chlorophytes (EC50 = 4.14-81.2 µmol/L). Diatoms were most sensitive to trimethoprim (EC50 = 7.36-74.61 µmol/L) followed by cyanobacteria (EC50 = 315.78-344.45 µmol/L) and chlorophytes (EC50 >344.45 µmol/L) for trimethoprim. While the results of our study partly support the current approach to regulatory environmental risk assessment where cyanobacterial species are recommended for use on antibiotic compounds, they indicate that for some antibiotics this group might not be the most appropriate test organism. We would therefore advocate that environmental risk assessments consider data on three algal groups (chlorophytes, cyanobacteria and diatoms) and use test species from these groups that are consistently found to be the most sensitive (Pseudokirchneriella subcapitata, Anabaena flos-aquae and Navicula pelliculosa). This article is protected by copyright. All rights reserved

Effects of Antibiotics on the Growth and Physiology of Chlorophytes, Cyanobacteria, and a Diatom

The occurrence of antibiotics in surface waters has been reported worldwide with concentrations ranging from ng L−1 to low µg L−1 levels. During environmental risk assessments, effects of antibiotics on algal species are assessed using standard test protocols (e.g., the OECD 201 guideline), where the cell number endpoint is used as a surrogate for growth. However, the use of photosynthetic related endpoints, such as oxygen evolution rate, and the assessment of effects on algal pigments could help to inform our understanding of the impacts of antibiotics on algal species. This study explored the effects of three major usage antibiotics (tylosin, lincomycin, and trimethoprim) on the growth and physiology of two chlorophytes (Desmodesmus subspicatus and Pseudokirchneriella subcapitata), a cyanobacteria (Anabaena flos-aquae), and a diatom (Navicula pelliculosa) using a battery of parameters, including cell density, oxygen evolution rate, total chlorophyll content, carotenoids, and the irradiance–photosynthesis relationship. The results indicated that photosynthesis of chlorophytes was a more sensitive endpoint than growth (i.e., EC50 derived based on the effects of tylosin on the growth of D. subspicatus was 38.27 µmol L−1 compared with an EC50 of 17.6 µmol L−1 based on photosynthetic rate), but the situation was reversed when testing cyanobacteria and the diatom (i.e., EC50 derived based on the effects of tylosin on the growth of A. flos-aquae was 0.06 µmol L−1; EC50 0.33 µmol L−1 based on photosynthetic rate). The pigment contents of algal cells were affected by the three antibiotics for D. subspicatus. However, in some cases, pigment content was stimulated for P. subcapitata, N. pelliculosa, and A. flos-aquae. The light utilization efficiency of chlorophytes and diatom was decreased markedly in the presence of antibiotics. The results demonstrated that the integration of these additional endpoints into existing standardised protocols could provide useful insights into the impacts of antibiotics on algal species

Evaluation of splanchnic oximetry, Doppler flow velocimetry in the superior mesenteric artery and feeding tolerance in very low birth weight IUGR and non-IUGR infants receiving bolus <it>versus</it> continuous enteral nutrition

Abstract Background IUGR infants are thought to have impaired gut function after birth, which may result in intestinal disturbances, ranging from temporary intolerance to the enteral feeding to full-blown NEC. In literature there is no consensus regarding the impact of enteral feeding on intestinal blood flow and hence regarding the best regimen and the best rate of delivering the enteral nutrition. Methods/design This is a randomized, non-pharmacological, single-center, cross-over study including 20 VLBW infants. Inclusion criteria * Weight at birth ranging: 700–1501 grams * Gestational age up to 25 weeks and 6 days * Written informed consent from parents or guardians Exclusion criteria * Major congenital abnormality * Patients enrolled in other trials * Significant multi-organ failure prior to trial entry * Pre-existing cutaneous disease not allowing the placement of the NIRS’ probe In the first 24 hours of life, between the 48th and 72nd hours of life, and during Minimal Enteral Feeding, all infants’ intestinal perfusion will be evaluated with NIRS and a Doppler of the superior mesenteric artery will be executed. At the achievement of an enteral intake of 100 mL/Kg/day the patients (IUGR and NON IUGR separately) will be randomized in 2 groups: Group A (n=10) will receive a feed by bolus (in 10 minutes); then, after at least 3 hours, they will receive the same amount of formula administered in 3 hours. Group B (n=10) will receive a feed administered in 3 hours followed by a bolus administration of the same amount of formula (in 10 minutes) after at least 3 hours. On the randomization day intestinal and cerebral regional oximetry will be measured via NIRS. Intestinal and celebral oximetry will be measured before the feed and 30 minutes after the feed by bolus during the 3 hours nutrition the measurements will be performed before the feed, 30 minutes from the start of the nutrition and 30 minutes after the end of the gavage. An evaluation of blood flow velocity of the superior mesenteric artery will be performed meanwhile. The infants of the Group A will be fed with continuous nutrition until the achievement of full enteral feeding. The infants of the Group B will be fed by bolus until the achievement of full enteral feeding. Discussion Evaluations of intestinal oximetry and superior mesenteric artery blood flow after the feed may help in differentiating how the feeding regimen alters the splanchnic blood flow and oxygenation and if the changes induced by feeding are different in IUGR versus NON IUGR infants. Trial registration number NCT01341236</p