Growth Performance and Immunity of Broilers Fed Sorghum-Soybean Meal Diets Supplemented with Phytases and Β-Mannanases.

Most grains and vegetable feedstuffs used in commercial poultry feed contain phytates and polysaccharides-non-starchy chemical structures that are not degraded by digestive tract enzymes. Exogenous enzymes optimize the use of dietary ingredients. This study aimed to determine whether combining ß-mannanases (400 g/ton) and phytases in broiler sorghum-soybean diets could improve performance and immunity in broilers. Four diets were randomized in a 2 × 2 factorial design, with two phytase levels (500 or 1500 FTU/kg) and ß-mannanase supplementation (0-400 g/ton; 158 million units/kg minimum enzyme activity). Six replicate battery cages of 10 chicks were fed each diet ad libitum. To assess cellular and humoral immune responses, 10 birds per treatment were euthanized on day 21. Supplementation with ß-mannanase enzymes led to increased body weight and a higher feed conversion index (FCI) (p < 0.05). The phytase factor improved the FCI at 1500 FTU/kg (p < 0.05). Supplementation with ß-mannanases improved the immune response by increasing the IgA concentration in the duodenum (95%) and total serum immunoglobulins (p < 0.05). The morphometric index increased in all organs (p < 0.05), and the heterophile/lymphocyte ratio (HLR) decreased by 50% (p < 0.05). Supplementing broilers with ß-mannanases in sorghum-soybean meal diets with phytases improved their performance and immunity.

Pathological findings and their association with diseases of captive psittacine birds native to Mexico.

The captivity and use of native psittacine birds is prohibited in Mexico. However, as these birds are among the groups most affected by illegal trafficking, they are commonly found as companion animals. Nevertheless, it is difficult to obtain information on their health. Therefore, a retrospective study was conducted of the clinical histories and necropsy reports of native psittacines that had been submitted to the Bird Disease Diagnostic and Research Laboratory of the Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, from 2006 to 2017. The lesions were classified according to type and anatomical location and the diseases were classified as infectious or non-infectious. During this period, 252 psittacines were submitted, the most frequent of which were the red-lored parrot (Amazona autumnalis), orange-fronted parakeet (Eupsittula canicularis) and scarlet macaw (Ara macao). The lesions were primarily located in the digestive and respiratory systems. By integrating the clinical histories and post-mortem findings, we concluded that nutritional disorders were the most frequent non-infectious diseases, systemic bacterial infections were the most frequent infectious conditions, the primary parasite was Sarcocystis spp and the most frequent neoplasm was multicentric lymphoma.

First report of Psittacid Avipoxvirus in Agapornis in Mexico

A postmortem study was performed on two lovebirds (Agapornis fischeri and Agapornis personatus) that had scabs in the periocular region and on the eyelid, as well as serous blepharitis. Microscopically, the eyelids showed ulcers, necrosis and serocellular crusts, severe hyperplasia of keratinocytes with eosinophilic intracytoplasmic inclusion bodies (Bollinger's bodies), bacterial colonies of gram-positive coccoid morphology and PAS-positive septate and 45° branching hyphae. The microbiological study identified the colonies as Staphylococcus spp. and Aspergillus fumigatus, respectively. Using molecular techniques, avian pox clade C was identified on the eyelid. This is the first report in Mexico of a case of avian pox in parrots associated with clade C Avipoxvirus.(AU)

Aquatic Environments as Hotspots of Transferable Low-Level Quinolone Resistance and Their Potential Contribution to High-Level Quinolone Resistance.

The disposal of antibiotics in the aquatic environment favors the selection of bacteria exhibiting antibiotic resistance mechanisms. Quinolones are bactericidal antimicrobials extensively used in both human and animal medicine. Some of the quinolone-resistance mechanisms are encoded by different bacterial genes, whereas others are the result of mutations in the enzymes on which those antibiotics act. The worldwide occurrence of quinolone resistance genes in aquatic environments has been widely reported, particularly in areas impacted by urban discharges. The most commonly reported quinolone resistance gene, qnr, encodes for the Qnr proteins that protect DNA gyrase and topoisomerase IV from quinolone activity. It is important to note that low-level resistance usually constitutes the first step in the development of high-level resistance, because bacteria carrying these genes have an adaptive advantage compared to the highly susceptible bacterial population in environments with low concentrations of this antimicrobial group. In addition, these genes can act additively with chromosomal mutations in the sequences of the target proteins of quinolones leading to high-level quinolone resistance. The occurrence of qnr genes in aquatic environments is most probably caused by the release of bacteria carrying these genes through anthropogenic pollution and maintained by the selective activity of antimicrobial residues discharged into these environments. This increase in the levels of quinolone resistance has consequences both in clinical settings and the wider aquatic environment, where there is an increased exposure risk to the general population, representing a significant threat to the efficacy of quinolone-based human and animal therapies. In this review the potential role of aquatic environments as reservoirs of the qnr genes, their activity in reducing the susceptibility to various quinolones, and the possible ways these genes contribute to the acquisition and spread of high-level resistance to quinolones will be discussed.

Dispharynx nasuta (Nematoda: Acuarioidea: Acuariidae) infestation in exotic red-rumped parrots (Psephotus haematonotus) in captivity in the State of Michoacan, Mexico.

Dispharynx nasuta is a widespread nematode parasite located in the proventriculus. This parasite may cause mortality in free-living birds or in captivity. However, reports of this parasite in psittacines are scarce. In a private aviary, in Zamora, Michoacan, Mexico six red-rumped parrots (Psephotus haematonotus) died in one month, from mid-August to mid-September 2016, and one more specimen died during the examination. Prior to death, the birds presented depression, ruffled feathers, crop atony, and regurgitation. Upon necropsy, ulcers in the proventriculus, and hemorrhagic content associated with the presence of round worms was observed. At histopathology examination, the parasites were identified as Spirurida nematodes, located in the proventricular and ventricular mucosa. Specimens were submitted to the parasitology laboratory of the College of Veterinary Medicine and Husbandry, National Autonomous University of Mexico (UNAM), where the parasites were identified as D. nasuta. This is the first report of D. nasuta in P. haematonotus and the first report of D. nasuta in Mexico.

Pathological and mycological characterization of pulmonary Aspergillus fumigatus infection producing gliotoxin in a captive African grey parrot (Psittacus erithacus)

Aspergillosis, the main causative agent of which is Aspergillus fumigatus, causes mortality in all types of birds. Gliotoxin (GT), one of the multiple virulence factors of A. fumigatus, has a variety of immunosuppressive effects. The corpse of an African grey parrot (Psittacus erithacus) was sent for necropsy and diagnostic rule-out. The lungs were enlarged, firm, and had dark-red coloration, on the parietal faces of both lungs, some semi-circular caseous necrosis areas were observed. The caudal thoracic and abdominal air sacs were thickened and contained a fibrin-heterophilic exudate. Histopathologically, a necrotic and granulomatous bronchopneumonia was observed with intralesional hyphae with characteristics compatible with Aspergillus sp. that were positive with Grocott´s staining. Fibrinous and heterophilic airsacculitis was found in the air sacs. A. fumigatus was isolated from lungs, characterized using serial microcultures, and confirmed using polymerase chain reaction. In addition, GT production was detected in vitro from the culture filtrate in which the isolate was grown; the organic extract was analysed via thin-layer chromatography. This is the first detection of GT in a case of pulmonary aspergillosis in a parrot, which could help to understand the pathogenesis of the disease in psittacines.(AU)

Immunotherapy With Egg Yolk Eimeria sp.-Specific Immunoglobulins in SPF Leghorn Chicks Elicits Successful Protection Against Eimeria tenella Infection.

Avian coccidiosis is the first to most economically important parasite disease affecting poultry industries worldwide. Current prevention measures are largely based upon prophylactic chemotherapy supplemented by the application of live attenuated or wild-type parasite vaccines. However, the rising appearance of drug resistance, consumer's concern for antibiotics use in poultry production and higher manufacturing cost of live vaccines has driven to adopt new technologies aimed at increasing animal health and production efficiency. Supplementing chickens with egg yolk Eimeria sp.-specific immunoglobulins can be a viable alternative to avoid severe outbreaks of the disease. Twelve-week-old SPF White Leghorn chickens were experimentally infected with a large dose of E. tenella. During the prepatent period, the birds were supplemented by oral gavage with 60 or 120 mg/bird of hyperimmune egg yolk Eimeria species-specific immunoglobulins Y (Supracox®, SC) on a daily basis. The animals were euthanized 7 days post-infection (PI) and their passive immune protection was evaluated. Birds treated with 120 mg/bird of SC showed more viability, increased body weight gain (BWG), a normal hematocrit level (HCT), reduced oocyst output per gram of feces (OPG) or cecal tissue (OPGC), and fewer cecal lesions compared to the untreated infected (UI) control group. Birds supplemented with 60 mg/bird of SC did not show any significant difference on BWG, HCT, OPG, OPGC, and cecal lesion score when compared with the UI group. An ELISA test of the SC showed a weak cross-reactivity of IgY toward two asexual zoite stages of E. tenella. Western blot analysis of the sporozoite with SC showed few antigens barely recognized, while more stained bands were detected in the merozoite (≈82, ≈60, ≈54, ≈40, ≈38, ≈27.5, and ≈13 kDa). Oral immunotherapy using egg yolk polyclonal IgYs against Eimeria sp. represents an effective and natural resource against severe E. tenella infection favoring the gradual withdrawal of the anticoccidial drugs and antibiotics.

Characterization of a Novel Variant of the Quinolone-Resistance Gene qnrB (qnrB89) Carried by a Multi-Drug Resistant Citrobacter gillenii Strain Isolated from Farmed Salmon in Chile.

The main objective of this study was to characterize using whole-genome sequencing analysis, a new variant of the qnrB gene (qnrB89) carried by a fluoroquinolone-susceptible bacterium isolated from mucus of farmed Salmo salar fingerling in Chile. Citrobacter gillenii FP75 was identified by using biochemical tests and 16S ribosomal gene analysis. Nucleotide and amino acid sequences of the qnrB89 gene exhibited an identity to qnrB of 81.24% and 91.59%, respectively. The genetic environment of qnrB89 was characterized by the upstream location of a sequence encoding for a protein containing a heavy metal-binding domain and a gene encoding for a N-acetylmuramoyl-L-alanine amidase protein, whereas downstream to qnrB89 gene were detected the csp and cspG genes, encoding cold-shock proteins. The qnrB89 gene was located on a large chromosomal contig of the FP75 genome and was not associated with the 10-kb plasmid and class 1 integron harbored by the FP75 strain. This study reports for the first time the carriage of a qnrB gene by the C. gillenii species, and its detection in a bacterial strain isolated from farmed salmon in Chile.

First report of Boydaia falconis (Trombidiformes: Ereynetidae: Speleognathinae) in a Merlin (Falco columbarius) (Falconiformes: Falconidae) in Veracruz, Mexico.

The report presented herein documents the finding of mites in the nares of a Merlin (Falco columbarius) (Linnaeus, 1758; Falconiformes: Falconidae) during its capture for identification and ringing at the conservation reserve area in the municipality of Cansaburro, state of Veracruz, Mexico.The mites were collected from the nostril of the bird and identified as Boydaia falconis (Fain, 1956; Trombidiformes: Ereynetidae: Speleognathinae). There are few records of nasal mites in Faconiforms in North America. This is the first report of Boydaia falconis in falconiform hosts from Mexico. Further study is required on these mites to aid in our understanding of the biology, ecology and symbiotic relationships of speleognathine nasal mites.

First report of psittacine beak and feather disease in importedbudgerigar (Melopsittacus undulatus) chicks in Mexico

This case reports an outbreak of psittacine beak and feather disease in imported budgerigars (Melopsittacusundulatus) in a breeding site in Mexico. Feather abnormalities occurred in 3-month-old budgerigars and the percentage of affected birds was 40 of 100 birds (40%). The disease begins with varying degrees of bare skin on the back, the ventral region of the body, and the thoracic and pelvic regions without clinical signs or mortality offspring. Thirty-tree budgerigars were referred to the laboratory for diagnostics work-up. The hemogram showed different stages of inflammation in all studied birds, where 66% had relative erythrocytosis, leukocytosis due to heterophilia and monocytosis associated with chronic inflammation. The biochemical analysis showed mainly hypoproteinemia and hypouricemia in 5/8 and 4/9 birds, respectively. The absence of feathers with some tiny calamus of the pectoral region was the most significant feature and no other significant pathologic changes were observed. Histopathologic findings were apoptosis and a moderate amount of spherical intracytoplasmic basophilic inclusion bodies in clusters in some epithelial cells of feather follicles (12/14 sections examined) and bursa of Fabricius (8/10 sections examined). End-point PCR of bursa of Fabricius, genome sequencing and phylogenetic analysis, confirmed circovirus identification of the psittacine beak and feather disease virus species and belonging to the group 2 previously found in budgerigars. This is the first description of the psittacine beak and feather disease in budgerigars in Mexico showing the need of monitoring health status of companion and free-ranging endemic and endangered psittacine birds in Mexico in order to collaborate with the trade regulation of these bird species.(AU)

First report of psittacine beak and feather disease in importedbudgerigar (Melopsittacus undulatus) chicks in Mexico

This case reports an outbreak of psittacine beak and feather disease in imported budgerigars (Melopsittacusundulatus) in a breeding site in Mexico. Feather abnormalities occurred in 3-month-old budgerigars and the percentage of affected birds was 40 of 100 birds (40%). The disease begins with varying degrees of bare skin on the back, the ventral region of the body, and the thoracic and pelvic regions without clinical signs or mortality offspring. Thirty-tree budgerigars were referred to the laboratory for diagnostics work-up. The hemogram showed different stages of inflammation in all studied birds, where 66% had relative erythrocytosis, leukocytosis due to heterophilia and monocytosis associated with chronic inflammation. The biochemical analysis showed mainly hypoproteinemia and hypouricemia in 5/8 and 4/9 birds, respectively. The absence of feathers with some tiny calamus of the pectoral region was the most significant feature and no other significant pathologic changes were observed. Histopathologic findings were apoptosis and a moderate amount of spherical intracytoplasmic basophilic inclusion bodies in clusters in some epithelial cells of feather follicles (12/14 sections examined) and bursa of Fabricius (8/10 sections examined). End-point PCR of bursa of Fabricius, genome sequencing and phylogenetic analysis, confirmed circovirus identification of the psittacine beak and feather disease virus species and belonging to the group 2 previously found in budgerigars. This is the first description of the psittacine beak and feather disease in budgerigars in Mexico showing the need of monitoring health status of companion and free-ranging endemic and endangered psittacine birds in Mexico in order to collaborate with the trade regulation of these bird species.

Effect of the Age and Body Weight of the Broiler Breeders Male on the Presentation of Oxidative Stress and Its Correlation with the Quality of Testicular Parenchyma and Physiological Antioxidant Levels.

Chicken meat is a food of high nutritional quality; its production requires birds called broilers breeders and looking after all aspects that influence their reproductive capacity. An ongoing controversy exists among researchers related to the weight of the rooster and its fertilization capacity. By histological and biochemical tests, the association between weight and age with oxidant damage, testicular parenchyma and antioxidant capacity was evaluated in Ross 308 roosters. Testicular integrity was assessed by histological analysis, oxidative stress was determined by malondialdehyde content, non-enzymatic antioxidant capacity was determined by oxygen radical absorbance capacity assay and enzymatic antioxidant capacity through glutathione peroxidase, glutathione reductase and glutathione-S-transferase activities. Histological analysis showed vacuolization of the epithelium from the seminiferous tubules. A significant negative association was observed between malondialdehyde and the deterioration of the integrity of the seminiferous epithelium, as well as between age and integrity of the seminiferous epithelium. It became evident that oxidative damage directly affects the quality of testicular parenchyma. Weight and age were not associated with the antioxidant enzymes activities, but with non-enzymatic capacity. The data obtained suggest that weight is not the most important factor that influences the fertility of the rooster.

Live Feeds Used in the Larval Culture of Red Cusk Eel, Genypterus chilensis, Carry High Levels of Antimicrobial-Resistant Bacteria and Antibiotic-Resistance Genes (ARGs).

The culture of red cusk eel Genypterus chilensis is currently considered a priority for Chilean aquaculture but low larval survival rates have prompted the need for the continuous use of antibacterials. The main aim of this study was to evaluate the role of live feed as a source of antibacterial-resistant bacteria in a commercial culture of G. chilensis. Samples of rotifer and Artemia cultures used as live feed were collected during the larval growth period and culturable bacterial counts were performed using a spread plate method. Rotifer and Artemia cultures exhibited high levels of resistant bacteria (8.03 × 104 to 1.79 × 107 CFU/g and 1.47 × 106 to 3.50 × 108 CFU/g, respectively). Sixty-five florfenicol-resistant isolates were identified as Vibrio (81.5%) and Pseudoalteromonas (15.4%) using 16S rRNA gene sequence analysis. A high incidence of resistance to streptomycin (93.8%), oxytetracycline (89.2%), co-trimoxazole (84.6%), and kanamycin (73.8%) was exhibited by resistant isolates. A high proportion of isolates (76.9%) carried the florfenicol-resistance encoding genes floR and fexA, as well as plasmid DNA (75.0%). The high prevalence of multiresistant bacteria in live feed increases the incidence of the resistant microbiota in reared fish larvae, thus proper monitoring and management strategies for live feed cultures appear to be a priority for preventing future therapy failures in fish larval cultures.

A retrospective study of neoplasms in ornamental and pet birds diagnosed at the Hospital de Aves of the Universidad Nacional Autónoma de México (2007-2014)

A retrospective study including a total of 44 ornamental and pet birds with neoplasms diagnosed at the Hospital de Aves, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México from January 2007 to April 2014 was conducted. Most of affected birds were Psittaciformes (n=26, 59%) including budgerigars (Melopsittacus undulatus) (n=12/26, 46.15%) and amazon parrots (Amazona spp.) (n=7/26, 26.92%), and followed by Passeriformes and Anseriformes (n=7/44, 15.90%, each) and Galliformes (n=4/44, 9.09%). The youngest studied bird was a 6.5-week-old lovebird (Agapornis sp.) with a papilloma, and the oldest bird was a 37-year-old yellow-naped parrot (Amazona auropalliata) with a hemangiosarcoma. Most of the affected birds were adults (n=23, 52.27%). The gender was determined for 17 birds (38.63%), of which eight (47.05%) were females and nine (52.94%) males. There were 45 reported neoplasms,as one salmon-crested cockatoo (Cacatua moluccensis) had two neoplasms. The two most frequent neoplasms were fibrosarcomas (n=9/45, 20%) and hemangiosarcomas (n=5/45, 11.11%). The largest number of neoplasms was found in the integumentary system (n=18/45, 40%), followed by the reproductive system (n=10/45, 22.22%). Of the 16 types of neoplasms, seven (43.75%) were malignant, six (37.5%) were benign, and three (18.75%) were potentially malignant. This study showed similarities with retrospective previously reported studies and contributes to the knowledge of the neoplastic diseases that occur in ornamental and pet birds in Mexico.(AU)

A retrospective study of neoplasms in ornamental and pet birds diagnosed at the Hospital de Aves of the Universidad Nacional Autónoma de México (2007-2014)

A retrospective study including a total of 44 ornamental and pet birds with neoplasms diagnosed at the Hospital de Aves, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México from January 2007 to April 2014 was conducted. Most of affected birds were Psittaciformes (n=26, 59%) including budgerigars (Melopsittacus undulatus) (n=12/26, 46.15%) and amazon parrots (Amazona spp.) (n=7/26, 26.92%), and followed by Passeriformes and Anseriformes (n=7/44, 15.90%, each) and Galliformes (n=4/44, 9.09%). The youngest studied bird was a 6.5-week-old lovebird (Agapornis sp.) with a papilloma, and the oldest bird was a 37-year-old yellow-naped parrot (Amazona auropalliata) with a hemangiosarcoma. Most of the affected birds were adults (n=23, 52.27%). The gender was determined for 17 birds (38.63%), of which eight (47.05%) were females and nine (52.94%) males. There were 45 reported neoplasms,as one salmon-crested cockatoo (Cacatua moluccensis) had two neoplasms. The two most frequent neoplasms were fibrosarcomas (n=9/45, 20%) and hemangiosarcomas (n=5/45, 11.11%). The largest number of neoplasms was found in the integumentary system (n=18/45, 40%), followed by the reproductive system (n=10/45, 22.22%). Of the 16 types of neoplasms, seven (43.75%) were malignant, six (37.5%) were benign, and three (18.75%) were potentially malignant. This study showed similarities with retrospective previously reported studies and contributes to the knowledge of the neoplastic diseases that occur in ornamental and pet birds in Mexico.

Occurrence of Transferable Integrons and sul and dfr Genes Among Sulfonamide-and/or Trimethoprim-Resistant Bacteria Isolated From Chilean Salmonid Farms.

Salmon farming industry in Chile currently uses a significant quantity of antimicrobials to control bacterial pathologies. The main aims of this study were to investigate the presence of transferable sulfonamide- and trimethoprim-resistance genes, sul and dfr, and their association with integrons among bacteria associated to Chilean salmon farming. For this purpose, 91 Gram-negative strains resistant to sulfisoxazole and/or trimethoprim recovered from various sources of seven Chilean salmonid farms and mainly identified as belonging to the Pseudomonas genus (81.0%) were studied. Patterns of antimicrobial resistance of strains showed a high incidence of resistance to florfenicol (98.9%), erythromycin (95.6%), furazolidone (90.1%) and amoxicillin (98.0%), whereas strains exhibited minimum inhibitory concentrations (MIC90) values of sulfisoxazole and trimethoprim of >4,096 and >2,048 µg mL-1, respectively. Strains were studied for their carriage of these genes by polymerase chain reaction, using specific primers, and 28 strains (30.8%) were found to carry at least one type of sul gene, mainly associated to a class 1 integron (17 strains), and identified by 16S rRNA gene sequencing as mainly belonging to the Pseudomonas genus (21 strains). Of these, 22 strains carried the sul1 gene, 3 strains carried the sul2 gene, and 3 strains carried both the sul1 and sul2 genes. Among these, 19 strains also carried the class 1 integron-integrase gene intI1, whereas the dfrA1, dfrA12 and dfrA14 genes were detected, mostly not inserted in the class 1 integron. Otherwise, the sul3 and intI2 genes were not found. In addition, the capability to transfer by conjugation these resistance determinants was evaluated in 22 selected strains, and sul and dfr genes were successfully transferred by 10 assayed strains, mainly mediated by a 10 kb plasmid, with a frequency of transfer of 1.4 × 10-5 to 8.4 × 10-3 transconjugant per recipient cell, and exhibiting a co-transference of resistance to florfenicol and oxytetracycline, currently the most used in Chilean salmon industry, suggesting an antibacterial co-selection phenomenon. This is the first report of the characterization and transferability of integrons as well as sul and dfr genes among bacteria associated to Chilean salmon farms, evidencing a relevant role of this environment as a reservoir of these genes.

Purification and characterization of indochrome type blue pigment produced by Pseudarthrobacter sp. 34LCH1 isolated from Atacama desert.

The interest in and demand for natural dyes has increased significantly in recent years; however, very few natural blue dyes are commercially available, because blue colored compounds in nature are relatively rare. In this study, a blue pigment-producing bacteria from Lake Chungará (Atacama Desert, Chile) was isolated, and its blue pigment was purified and chemically characterized. The pigment-producing strain was identified as Pseudarthrobacter sp. by 16S rRNA gene sequencing. The pigment was separated from the filtered culture medium by column chromatography/solid-phase extraction using different resins (ionic exchange, C-18, size exclusion). The strain produced up to 2.5 g L-1 of blue pigment, which was very soluble in water, partially soluble in methanol and insoluble in other organic solvents. The pigment was analyzed and characterized by analytical HPLC, UV-Vis, FT-IR, and H-NMR, and purified by semi-preparative HPLC. The pigment was non-toxic to brine shrimp (LD50 > 2.3 g L-1) and was stable at pH 6-10 at temperatures below 60 °C. HPLC analysis shows that the pigment is composed of four major blue fractions. The physicochemical properties and structural analysis demonstrate that this pigment belongs to the indochrome isomers, whose properties have yet to have been characterized. The high solubility in water, good stability in neutral and basic pH, and negligible toxicity of the blue pigment make it a good candidate suitable for several industrial and possibly some food applications.

Current Status of the Use of Antibiotics and the Antimicrobial Resistance in the Chilean Salmon Farms.

The Chilean salmon industry has undergone a rapid development making the country the world's second largest producer of farmed salmon, but this growth has been accompanied by an intensive use of antibiotics. This overuse has become so significant that Chilean salmon aquaculture currently has one of the highest rates of antibiotic consumption per ton of harvested fish in the world. This review has focused on discussing use of antibiotics and current status of scientific knowledge regarding to incidence of antimicrobial resistance and associated genes in the Chilean salmonid farms. Over recent years there has been a consistent increase in the amount of antimicrobials used by Chilean salmonid farms, from 143.2 tons in 2010 to 382.5 tons in 2016. During 2016, Chilean companies utilized approximately 0.53 kg of antibiotics per ton of harvested salmon, 363.4 tons (95%) were used in marine farms, and 19.1 tons (5%) in freshwater farms dedicated to smolt production. Florfenicol and oxytetracycline were by far the most frequently used antibiotics during 2016 (82.5 and 16.8%, respectively), mainly being used to treat Piscirickettsia salmonis, currently considered the main bacterial threat to this industry. However, the increasing development of this industry in Chile, as well as the intensive use of antimicrobials, has not been accompanied by the necessary scientific research needed to understand the impact of the intensive use of antibiotics in this industry. Over the last two decades several studies assessing antimicrobial resistance and the resistome in the freshwater and marine environment impacted by salmon farming have been conducted, but information on the ecological and environmental consequences of antibiotic use in fish farming is still scarce. In addition, studies reporting the antimicrobial susceptibility of bacterial pathogens, mainly P. salmonis, have been developed, but a high number of these studies were aimed at setting their epidemiological cut-off values. In conclusion, further studies are urgently required, mainly focused on understanding the evolution and epidemiology of resistance genes in Chilean salmonid farming, and to investigate the feasibility of a link between these genes among bacteria from salmonid farms and human and fish pathogens.

Sulphur-cycling bacteria and ciliated protozoans in a Beggiatoaceae mat covering organically enriched sediments beneath a salmon farm in a southern Chilean fjord.

The colourless mat covering organically enriched sediments underlying an intensive salmon farm in Estero Pichicolo, southern Chile, was surveyed by combined 454 PyroTag and conventional Sanger sequencing of 16S/18S ribosomal RNA genes for Bacteria and Eukarya. The mat was dominated by the sulphide-oxidizing bacteria (SOB) Candidatus Isobeggiatoa, Candidatus Parabeggiatoa and Arcobacter. By order of their abundances, sulphate-reducing bacteria (SRB) were represented by diverse deltaproteobacterial Desulfobacteraceae, but also within Desulfobulbaceae, Desulfuromonadaceae and Desulfovibrionaceae. The eukaryotic PyroTags were dominated by polychaetes, copepods and nematodes, however, ciliated protozoans were highly abundant in microscopy observations, and were represented by the genera Condylostoma, Loxophyllum and Peritromus. Finally, the abundant Sulfurimonas/Sulfurovum also suggest the occurrence of zero-valence sulphur oxidation, probably derived from Beggiatoaceae as a result of bacteriovorus infaunal activity or generated as free S(0) by the Arcobacter bacteria. The survey suggests an intense and complex sulphur cycle within the surface of salmon-farm impacted sediments.

Distribution and growth of Vibrio parahaemolyticus in southern Chilean clams (Venus antiqua) and blue mussels (Mytilus chilensis).

We evaluated the distribution and growth of Vibrio parahaemolyticus in the inland sea of southern Chile, where the world's largest foodborne gastroenteritis outbreak by the pandemic strain O3:K6 occurred in 2005. Intertidal samples of Mytilus chilensis and Venus antiqua were collected around port towns between 41°28'S and 43°07'S, during April to May 2011 and January to March 2012. We used most probable number real-time polymerase chain reaction (MPN-PCR) for enumeration of the tlh, tdh, and trh genes in freshly harvested bivalves and after a controlled postharvest temperature abuse. Pathogenic markers (tdh+ or trh+) were not detected. Total V. parahaemolyticus (tlh+) in freshly harvested samples reached up to 0.38 and 3.66 log MPN/g in 2011 and 2012, respectively, with values close to or above 3 log MPN/g only near Puerto Montt (41°28'S, 72°55'W). Enrichments by temperature abuse (>2 log MPN/g) occurred mainly in the same zone, regardless of the year, suggesting that both natural or anthropogenic exposure to high temperatures were more critical. Lower salinity and higher sea surface temperature in Reloncaví Sound and Reloncaví Estuary were consistent with our observations and allowed confirmation of the existence of a high-risk zone near Puerto Montt. Based on the results, a strategy focused on risk management inside this defined hazard zone is recommended.