Luciana Migliore

Phytotoxicity to and uptake of enrofloxacin in crop plants

Phytotoxicity of enrofloxacin on crop plants Cucumis sativus, Lactuca sativa, Phaseolus vulgaris and Raphanus sativus was determined in a laboratory model: the effect of 50, 100 and 5000 microgl(-1) were evaluated after 30 days exposure by measuring post-germinative growth of primary root, hypocotyl, cotyledons and leaves. Concentrations between 50 and 5000 microgl(-1) induced both toxic effect and hormesis in plants, by significantly modifying both length of primary root, hypocotyl, cotyledons and the number/length of leaves. A toxic effect is induced by high concentration (5000 microgl(-1)), while hormesis occurs at low concentrations (50 and 100 microgl(-1)). A continuum between toxic effect and hormesis is found in the four plant species. Both toxic effect and hormesis can be related to an efficient plant drug uptake, in the order of microgg(-1). Plants are able to metabolize enrofloxacin into ciprofloxacin, as also happens in animals; Cucumis, Lactuca and Phaseolus biologically convert about one quarter of stored enrofloxacin. The ecological implication of enrofloxacin contamination in terrestrial environments is discussed.

Toxicity of several important agricultural antibiotics to Artemia

The possible effects of antibiotic drug contamination in marine and brackish systems were evaluated using a new methodological approach. Five drugs, namely aminosidine (A), bacitracin (B), erythromycin (E), flumequine (F) and lincomycin (L), were subjected to toxicity tests using nauplii and cysts of Artemia as a model of drug contamination from intensive farming. Tests on nauplii were performed by the ArToxKit-M test (Persoone and Van Haecke, 1981), test on cysts by our experimental protocol (Migliore et al., 1993a, b). The lethal effect on nauplii were evaluated between 24 and 120 h: the sequence of decreasing toxicity was B > F > L > A > E. A high toxicity of B was recorded. In addition, B and F were tested on cysts. B significantly lowered hatching; this depended on the interference of B with normal development. F did not depress hatching, but it deeply altered nauplii pigmentation. The interest in assessing the possible environmental risks due to drugs used in intensive farming and the need for suitable standards to improve sea-water quality is discussed.

Effect of sulphadimethoxine contamination on barley (Hordeum distichum L, Poaceae, Liliopsida)

Animal wastes from intensive farming are generally collected for field fertilisation. They may contain drugs that can become soil pollutants. To evaluate the possible effects of such contamination in terrestrial systems, sulphadimethoxine has been subjected to laboratory tests (in vitro, synthetic medium, and soil) using seeds of barley (Hordeum distichum L.). The drug suppressed normal post-germinative development and growth of roots and leaves in both test conditions; this effect was dependent on the bioaccumulation rate, which was higher on synthetic medium than in soil. Bioaccumulation was higher in roots than foliage and this was markedly evident in soil and, in particular, in soils with a low humus content. The environmental risk of sludge application on soils and the possible contamination of food chains are discussed.

Tracking acquired antibiotic resistance in commensal bacteria of Galápagos land iguanas: no man, no resistance.

Background Antibiotic resistance, evolving and spreading among bacterial pathogens, poses a serious threat to human health. Antibiotic use for clinical, veterinary and agricultural practices provides the major selective pressure for emergence and persistence of acquired resistance determinants. However, resistance has also been found in the absence of antibiotic exposure, such as in bacteria from wildlife, raising a question about the mechanisms of emergence and persistence of resistant strains under similar conditions, and the implications for resistance control strategies. Since previous studies yielded some contrasting results, possibly due to differences in the ecological landscapes of the studied wildlife, we further investigated this issue in wildlife from a remote setting of the Galapagos archipelago. Methodology/Principal Findings Screening for acquired antibiotic resistance was carried out in commensal enterobacteria from Conolophus pallidus, the terrestrial iguana of Isla Santa Fe, where: i) the abiotic conditions ensure to microbes good survival possibilities in the environment; ii) the animal density and their habits favour microbial circulation between individuals; and iii) there is no history of antibiotic exposure and the impact of humans and introduced animal species is minimal except for restricted areas. Results revealed that acquired antibiotic resistance traits were exceedingly rare among bacteria, occurring only as non-dominant strains from an area of minor human impact. Conclusions/Significance Where both the exposure to antibiotics and the anthropic pressure are minimal, acquired antibiotic resistance traits are not normally found in bacteria from wildlife, even if the ecological landscape is highly favourable to bacterial circulation among animals. Monitoring antibiotic resistance in wildlife from remote areas could also be a useful tool to evaluate the impact of anthropic pressure.

Phytotoxicity to and uptake of flumequine used in intensive aquaculture on the aquatic weed, Lythrum salicaria L.

Phytotoxicity of Flumequine on the aquatic weed Lythrum salicaria L. was determined by two laboratory models: a single concentration test, by which the effects of 100 mg l-1 were evaluated after 10, 20, 30 days and a multiple concentration test, by which the effects of 5000-1000-500-100-50 micrograms l-1 were evaluated after 35-day exposure. 100 mg l-1 are highly toxic and significantly decrease the growth of plants; this effect increases with time. Concentrations between 5000 and 50 micrograms l-1 induced hormesis in plants, by significantly increasing mean number and dimension of leaves and secondary roots. The effect is the highest at 50 micrograms l-1 and decreases with increase in concentration. Both toxic effect and hormesis can be related to plant drug uptake, quite high, in the order of micrograms g-1. The ecological implication of Flumequine contamination in aquatic environments and the possible use of Lythrum salicaria for bioremediation and/or monitoring technique are discussed.

Laboratory models to evaluate phytotoxicity of sulphadimethoxine on terrestrial plants

Abstract Antimicrobial drugs soil contamination is a possible side effect of spreading animal wastes from intensive farming on arable land: waste often contain persistent drugs (like sulphonamides) that pollute soil. In laboratory tests different crop plants and weeds demonstrated, on both synthetic medium and soil, toxicity and sulphadimethoxine bioaccumulation. These data suggest potential adverse implications for organisms higher up the food net, including humans. The increasingly used technique ofsoil top dressing will impose the monitoring of antimicrobial contamination in arable lands and their crops, to protect natural ecosystems and consumer. A possible tool for this monitoring is the use of weeds that can constitute a “mesh” where antimicrobial contamination can be detected.

Antibiotics of zootechnical use: Effects of acute high and low dose contamination on Daphnia magna Straus

To gather data on the effects of antibiotic pollution in freshwater systems and to determine methodological approaches, aminosidine (A), bacitracin (B), erythromycin (E) and lincomycin (L) were subjected to acute high dose toxicily tests (AHDTT) using Daphnia magna and following the EEC protocol (EEC Commission 84/449, 1984); the lethal effect evaluated at 24, 48 and 72 h determined the sequence of decreasing toxicity to be B > E > A > L. Furthermore, the four antibiotics were tested in acute low dose totoxiciiy teats (ALDTT) using Daplmia magna by studying the alteration of phototactic behaviour. This test showed that L and B depressed phototaxis, while A increased the light induced migration rate. E did not alter the phototactic behaviour.

Sulphadimethoxine and Azolla filiculoides Lam.: a model for drug remediation.

Plants can be an interesting tool for in situ remediation of drug contaminated waters. In a laboratory model Azolla filiculoides Lam., an aquatic fern known to absorb pollutants, has been exposed to an environmental persistent antibiotic commonly used in intensive farming, sulphadimethoxine (S), to test its bioremediation capability. In a 5 week experiment, plants were cultivated outdoor at four drug concentrations (50, 150, 300 and 450 mg l(-1)) in N-free mineral medium. Drug affects growth rate (as biomass yield per week), N2-fixation, heterocyst frequency, but plants are able to survive. Notwithstanding, at all concentrations tested drug was actively removed from the medium and the accumulation in the biomass is in order of magnitude up to mg g(-1) plant dry weight (1000 ppm). Drug uptake and degradation rates increase with S concentrations in the culture medium. The efficacy of the model was very high. These results demonstrated that Azolla can be taken into consideration as a tool for sulphonamides environmental monitoring and decontamination.

Hormetic effect(s) of tetracyclines as environmental contaminant on Zea mays.

Animal wastes from intensive pig farming as fertilizers may expose crops to antimicrobials. Zea mays cultivations were carried out on a virgin field, subjected to dressing with pig slurries contaminated at 15 mg L(-1) of Oxy- and 5 mg L(-1) of Chlor-tetracycline, and at 8 mg L(-1) of Oxy and 3 mg L(-1) of Chlor, respectively. Pot cultivation was performed outdoor (Oxy in the range 62.5-1000 ng g(-1) dry soil) and plants harvested after 45 days. Tetracyclines analyses on soils and on field plants (roots, stalks, and leaves) did not determine the appreciable presence of tetracyclines. Residues were found in the 45-day pot corn only, in the range of 1-50 ng g(-1) for Oxy in roots, accounting for a 5% carry-over rate, on average. Although no detectable residues in plants from on land cultivations, both experimental batches showed the same biphasic growth form corresponding to a dose/response hormetic curve.

Effects of sulphadimethoxine on cosmopolitan weeds (Amaranthus retroflexus L., Plantago major L. and Rumex acetosella L.).

Animal wastes from intensive farming are generally collected for field fertilisation. They may contain drugs that can become soil pollutants. The effect of such contamination on terrestrial biota has been demonstrated in laboratory tests on different plant species, using a common antimicrobial, sulphadimethoxine. In the near future, the monitoring of antimicrobial contamination in arable lands and their crops will be of importance for the protection of natural ecosystems and consumers. A possible tool for this monitoring is the use of weeds that can constitute a ‘mesh’ from which antimicrobial contamination can be detected. In laboratory tests, some direct effects of sulphadimethoxine contamination were demonstrated on normal development and growth of three cosmopolitan weed species, Amaranthus retroflexus L., Plantago major L. and Rumex acetosella L. These effects depended on the very high accumulation rates in plants (thousand μg g−1). P. major accumulated the highest amount of drug followed by A. retroflexus and R. acetosella. These data further highlight the environmental risk of sludge application on soils and the possible contamination of food nets; but also give a potential tool for the monitoring of antimicrobial soil contamination.