Humberto Dölz

Antimicrobial use in aquaculture re‐examined: its relevance to antimicrobial resistance and to animal and human health

The worldwide growth of aquaculture has been accompanied by a rapid increase in therapeutic and prophylactic usage of antimicrobials including those important in human therapeutics. Approximately 80% of antimicrobials used in aquaculture enter the environment with their activity intact where they select for bacteria whose resistance arises from mutations or more importantly, from mobile genetic elements containing multiple resistance determinants transmissible to other bacteria. Such selection alters biodiversity in aquatic environments and the normal flora of fish and shellfish. The commonality of the mobilome (the total of all mobile genetic elements in a genome) between aquatic and terrestrial bacteria together with the presence of residual antimicrobials, biofilms, and high concentrations of bacteriophages where the aquatic environment may also be contaminated with pathogens of human and animal origin can stimulate exchange of genetic information between aquatic and terrestrial bacteria. Several recently found genetic elements and resistance determinants for quinolones, tetracyclines, and β-lactamases are shared between aquatic bacteria, fish pathogens, and human pathogens, and appear to have originated in aquatic bacteria. Excessive use of antimicrobials in aquaculture can thus potentially negatively impact animal and human health as well as the aquatic environment and should be better assessed and regulated.

Aquaculture as yet another environmental gateway to the development and globalisation of antimicrobial resistance

Aquaculture uses hundreds of tonnes of antimicrobials annually to prevent and treat bacterial infection. The passage of these antimicrobials into the aquatic environment selects for resistant bacteria and resistance genes and stimulates bacterial mutation, recombination, and horizontal gene transfer. The potential bridging of aquatic and human pathogen resistomes leads to emergence of new antimicrobial-resistant bacteria and global dissemination of them and their antimicrobial resistance genes into animal and human populations. Efforts to prevent antimicrobial overuse in aquaculture must include education of all stakeholders about its detrimental effects on the health of fish, human beings, and the aquatic ecosystem (the notion of One Health), and encouragement of environmentally friendly measures of disease prevention, including vaccines, probiotics, and bacteriophages. Adoption of these measures is a crucial supplement to efforts dealing with antimicrobial resistance by developing new therapeutic agents, if headway is to be made against the increasing problem of antimicrobial resistance in human and veterinary medicine.

Evaluation of the toxicity of 8 insecticides in Salmo salar and the in vitro effects against the isopode parasite, Ceratothoa gaudichaudii

Abstract A comparison was carried out between trichlorfon (Neguvon), dichlorvos (Nuvan 1000), fenthion (Baytex), propoxur (Baygon), fenitrothion (Folithion), azamethiphos (Alfacron 50 WP), cyfluthrin (Solfac) and deltamethrin (K-Othrina EC) to evaluate the efficiency of commercial insecticides against Ceratothoa gaudichaudii and their safety to the host fish, Salmo salar . To evaluate the toxicity of the products to salmon, groups of 20 fish (average weight 100 g each) were mantained in tanks of sea-water and exposed to 3 concentrations of each product for a period of 60 min. Mortality was then determined. The surviving fish were changed into tanks with clean sea-water and checked after 24 h. A control group of 20 fish was mantained without treatment. Parasites were obtained from normal infected salmon and kept in sea-water at 15 °C. The efficiency of every product was tested at 3 concentrations and 2 exposure times in groups of 20 parasites of 2 sizes. Mortality of parasites was determined after 15 and 60 min of exposure to the products. The surviving parasites were then transferred to clean sea-water and observed 15, 20 and 24 h after treatment. Every tested concentration was repeated 3 times and one control group was mantained for each parasite size. Only trichlorfon, dichlorvos and fenthion were not toxic to fish at the tested concentrations. The first 2 products were 100% effective against both size of the parasite at concentrations of 300 and 3 ppm for 60 min of exposure, respectively.

Uso inadecuado y excesivo de antibióticos: Salud pública y salmonicultura en Chile

Salmon aquaculture was one of the major growing and exporting industries in Chile. Its development was accompanied by an increasing and excessive use of large amounts of antimicrobials, such as quinolones, tetracyclines and florfenicol. The examination of the sanitary conditions in the industry as part of a more general investigation into the uncontrolled and extensive dissemination of the ISA virus epizootic in 2008, found numerous and wide-ranging shortcomings and limitations in management of preventive fish health. There was a growing industrial use of large amounts of antimicrobials as an attempt at prophylaxis of bacterial infections resulting from widespread unsanitary and unhealthy fish rearing conditions. As might be expected, these attempts were unsuccessful and this heavy antimicrobial use failed to prevent viral and parasitic epizootics. Comparative analysis of the amounts of antimicrobials, especially quinolones, consumed in salmon aquaculture and in human medicine in Chile robustly suggests that the most important selective pressure for antibiotic resistant bacteria in the country will be excessive antibiotic use in this industry. This excessive use will facilitate selection of resistant bacteria and resistance genes in water environments. The commonality of antibiotic resistance genes and the mobilome between environmental aquatic bacteria, fish pathogens and pathogens of terrestrial animals and humans suggests that horizontal gene transfer occurs between the resistome of these apparently independent and isolated bacterial populations. Thus, excessive antibiotic use in the marine environment in aquaculture is not innocuous and can potentially negatively affect therapy of bacterial infections of humans and terrestrial animals.

Resistencia a los antimicrobianos en Chile y el paradigma de Una Salud: manejando los riesgos para la salud pública humana y animal resultante del uso de antimicrobianos en la acuicultura del salmón y en medicina

The emergence and dissemination of antimicrobial-resistant bacteria (ARB) is currently seen as one of the major threats to human and animal public health. Veterinary use of antimicrobials in both developing and developed countries is many-fold greater than their use in human medicine and is an important determinant in selection of ARB. In light of the recently outlined National Plan Against Antimicrobial Resistance in Chile, our findings on antimicrobial use in salmon aquaculture and their impact on the environment and human health are highly relevant. Ninety-five percent of tetracyclines, phenicols and quinolones imported into Chile between 1998 and 2015 were for veterinary use, mostly in salmon aquaculture. Excessive use of antimicrobials at aquaculture sites was associated with antimicrobial residues in marine sediments 8 km distant and the presence of resistant marine bacteria harboring easily transmissible resistance genes, in mobile genetic elements, to these same antimicrobials. Moreover, quinolone and integron resistance genes in human pathogens isolated from patients in coastal regions adjacent to aquaculture sites were identical to genes isolated from regional marine bacteria, consistent with genetic communication between bacteria in these different environments. Passage of antimicrobials into the marine environment can potentially diminish environmental diversity, contaminate wild fish for human consumption, and facilitate the appearance of harmful algal blooms and resistant zoonotic and human pathogens. Our findings suggest that changes in aquaculture in Chile that prevent fish infections and decrease antimicrobial usage will prove a determining factor in preventing human and animal infections with multiply-resistant ARB in accord with the modern paradigm of One Health.

Absorcion Intestinal en Escolares Asintomático Portadores de Giardia Lamblia

Fourteen children, aged 6.2 to 1 3.6 years, asymptomatic Giardia Jamblias carriers, were studied. An tro pome trie evaluation and the following laboratory test, were done before and after treatment with Tinidazole and Mebendazole: hematocrit, blood hemoglobin; plasma total protein, and albumin concentration; basal scrum carotene concentration; vitamin A and D-xylose intestinal absortion test. Significant differences in tricep skinfold, hematocrit, hemoglobin and total plasmatic protein were found between pre and post treatment values. Blood xylose figures were 38.8 ± 8.9 and 57.5 ± 10.8 mg/dl pre and post treatment respectively (p<0.005). Plasma vitamin A levels after a priming dose were 60.5 ± 26.0 and 213 ± 113.0 /^g/dl and change in concentration of vitamin A, 32.7 ± 25.3 and 152.7 ± 115.8 pg/dl before and after treatment respectively (p <C 0.005). This data arc consistent with a significant increment in intestinal absortion rates after apropriate treatment of Giardia lamblias asymptomatic infections. (