This study aimed to identify through polyphasic approach (phenotypic and genotypic methods) strains of Aeromonas spp. isolated from surface water and sediment from three different points of the Coco River, Cearà following the salinity gradient of the water. Sampling was conducted between October 2011 and March 2012 each collection consisted of six samples. Aeromonas strains were isolated according to the technique described in the literature Gelatin Phosphate Salt Agar (agar plus GSP 20 μg/mL ampicillin). The physico-chemical parameters (salinity, pH and temperature) of water were on a track that favored not only survival, but also the multiplication of micro-organisms in both sites. Among this sample was isolated 140 strains suspected of Aeromonas and (36.4%) 51 strains were confirmed like Aeromonas spp., wich will be identifiyed until species for fenotipic and genotipic tests. In parallel to the insulation work was done a survey of alternative culture media, where we assessed the efficiency of culture media with different compositions in the characterization of colonies of multiple species of Aeromonas. While the antimicrobial susceptibility profile of Aeromonas strains were resistant 100% penicillin (PEN) and cephalothin (CFL) and 100% antimicrobial susceptibility Amikacin (AMI) and imipenem (IMP) among the nine antimicrobials tested and generally A. caviae was the species that showed resistance to antimicrobials. Among the 27 strains tested (45.8%) were multidrug-resistant by making a multiple resistence antibiotic (MRA) > 2. Five factors of different virulence and all strains were tested had at least one of the five virulence factors tested so that different combinations of virulence factors were found in isolates from the same sample. The results of genetic analysis using primers Aero16S-F and Aero16S-F showed that all isolates identified by conventional microbiological tests were confirmed by PCR and 65.6% of the species identified by conventional biochemical tests were confirmed by Box-PCR method. / Este trabalho teve como objetivo principal identificar atravÃs de abordagem polifÃsica (tÃcnicas fenotÃpicas e genotÃpicas) de cepas de Aeromonas spp. isoladas de Ãgua de superfÃcie e sedimento de trÃs pontos distintos do Rio CocÃ, Fortaleza, Cearà seguindo o gradiente de salinidade da Ãgua. Foram realizadas coletas no perÃodo de outubro de 2011 a marÃo de 2012, sendo cada coleta composta por seis amostras. As cepas de Aeromonas foram isoladas de acordo com a tÃcnica descrita na literatura em Ãgar Gelatina Fosfato Sal (Ãgar GSP acrescido de 20 μg/mL de ampicilina). Os parÃmetros fÃsico-quÃmicos (salinidade, pH e temperatura) da Ãgua estavam em uma faixa que favorecia nÃo sà a sobrevivÃncia, mas tambÃm a multiplicaÃÃo dos micro-organismos em dois pontos de coleta. Foram isoladas 140 cepas suspeitas de Aeromonas, 36 (25,7%) foram identificadas atà espÃcie sendo elas: A. caviae, A. media, A. eucrenophila e A. veronii, sendo A. caviae a espÃcie que apareceu com maior frequÃncia. Em paralelo ao trabalho de isolamento foi feita uma pesquisa com dois meios de cultivo alternativos, Ãgar UNISC e Ãgar Amido Ampicilina (AAA), nos quais foi avaliada a eficiÃncia dos meios de cultura com diferentes composiÃÃes, na caracterizaÃÃo de colÃnias de vÃrias espÃcies de Aeromonas. O perfil de suscetibilidade antimicrobiana das cepas de Aeromonas apresentou resistÃncia de 100% a Penicilina (PEN) e Cefalotina (CFL) e 100% de sensibilidade aos antimicrobianos Amicacina (AMI) e Imipenem (IMP) entre os nove antimicrobianos testados e de forma geral A. caviae (38,9%) foi a espÃcie que mais apresentou resistÃncia. Dentre as cepas avaliadas 27 (45,8%) foram multirresistentes por apresentarem um MAR > 2. Foram testados cinco fatores de virulÃncia diferentes e todas as cepas apresentaram pelo menos um desses fatores, de forma que diferentes combinaÃÃes desses fatores foram observadas em isolados provenientes da mesma amostra. Os resultados da anÃlise genÃtica utilizando os iniciadores Aero16S-F e Aero16S-R mostraram que todos os isolados identificados atravÃs de testes clÃssicos de microbiologia foram confirmados por meio da tÃcnica de PCR e 65,6% das espÃcies identificadas por testes bioquÃmicos convencionais foram confirmadas pelo mÃtodo de Box-PCR.

Orientadores: Carlos Francisco Sampaio Bonafé, Cláudio Chrysostomo Werneck / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-17T12:27:33Z (GMT). No. of bitstreams: 1 Carvalho_RicardoDuraesde_M.pdf: 7651307 bytes, checksum: 3194190cf6a33de3b0cdc4ddb7424afd (MD5) Previous issue date: 2010 / Resumo: A exposição à alta pressão é um método eficiente na inativação bacteriana, o qual é importante para a esterilização de alimentos. Neste trabalho, examinamos a inativação por alta pressão hidrostática em Aeromonas hydrophila AH 191, produtora de aerolisina, a qual possui atividades citotóxica, enterotóxica e hemolítica. Trinta min a 250 MPa (25 °C em PBS 0,1 M, pH 7,4), resultou em 9 log de UFC/mL de inativação bacteriana (a partir de 109 UFC/mL para <10 UFC/mL), porém, os tratamentos não alteraram a atividade hemolítica, enterotóxica e citotóxica produzidas por A. hydrophila AH 191. O sobrenadante de cultura bacteriana e o leite contaminado por A. hydrophila AH 191, pressurizado ou não, foram aplicados sobre células Vero e CaCo2, suspensões de hemácias humanas e de carneiro, e injetadas por via oral gástrica em camundongos Swiss, reproduzindo o ensaio de Dean. Os resultados mostram que os títulos das toxinas em amostras pressurizadas permaneceram iguais aos do controle, assim como as toxinas presentes nos sobrenadantes de cultura e no leite foram capazes de produzir acúmulo de líquidos no intestino de camundongos recém-nascidos. Estes resultados indicam a relevância do estudo na inativação de bactérias para a segurança alimentar e realça a importância de cautela no uso de alta pressão para a esterilização de alimentos, pois embora as bactérias possam ser inativadas, as toxinas produzidas por este micro-organismos podem continuar ativas, representando uma ameaça à saúde humana / Abstract: Exposure to high pressure is an efficient method for bacterial inactivation, which is important for the food sterilization. We examine the inactivation by high hydrostatic pressure in A. hydrophila AH 191, producer of aerolysin, which has cytotoxic, enterotoxic and hemolytic activities. A 30 min treatment at 250 MPa (25 °C in 0.1 M PBS, pH 7,4) resulted in 9 log CFU/mL of bacteria inactivation (from 109 CFU/mL to <10 CFU/mL). However, the treatment did not inactivate the hemolytic, enterotoxic and cytotoxic activities produced by A. hydrophila AH 191. The supernatant of bacterial culture and milk contaminated with A. hydrophila AH 191 pressurized or not were applied to Vero and CaCo2 cells, suspensions of human and sheep erythrocytes, and injected into mice via oral gastric Swiss reproducing the Dean test. The results show that evidence of toxins in samples pressurized remained similar to that of control, and the toxins in culture supernatants and milk were able to produce fluid accumulation in the intestine of suckling mouse. These results indicate the relevance of the study for bacteria inactivation to food security and enhance the importance for caution in the use of high prssure in foods sterilization, since although the bacteria can be inactivated, the toxins produced by micro-organisms continue to be active, representing a human health threat / Mestrado / Bioquimica / Mestre em Biologia Funcional e Molecular

Em um total de 90 amostras de hortaliças, incluindo 30 de alface, 30 de agrião e 30 de escarola, foi verificada a ocorrência de Aeromonas do grupo A. hydrophila, empregando-se os métodos de semeadura direta em ágar amido-amplicilina (contagem) e após enriquecimento em caldo tripticase-soja adicionado de ampicilina (teste de presença/ausência). As incubações foram feitas a 28&#186;C, durante 24 horas. A presença dessas bactérias foi detectada em 43 (47,8%) das amostras analisadas, com contagens variando de < 102 a 2, 0x 106UFC/g. As amostras de agrião foram as que revelaram, na contagem, com maiores números de Aeromonas spp. Das 43 amostras positivas para Aeromonas spp. 9 (21,0%) revelaram-se com números superiores a 104 UFC/g. sendo que 7 eram de agrião . Dentre as amostras de hortaliças analisadas, as de agrião revelaram-se com positividade para Aeromonas do grupo A. hydrophila (70,0%) significativamente maior em relação às de alface (43,3%) e de escarola (30,0%) a nível de 5%. Não foram observadas diferenças significativas entre as positividades obtidas através do método de semeadura direta em placas e do teste de presença/ausência para as amostras de alface e de agrião. Para as amostras de escarola, a positividade foi significativamente mais alta no teste de presença/ausência. Do total de 143 cepas confirmadas como sendo do gênero Aeromonas, 138 (96,5%) eram de A. caviae, 4 (2,8%) de A. hydophila e 1 (0,7%) que, pelas suas características, foi considerada como Aeromonas atipica. Dos resultados obtidos, pode-se depreender que as hortaliças dos tipos analisados, alface, agrião e escarola, dado os níveis de contaminação observados, podem representar risco aos consumidores. / A total of 90 retail vegetable samples, including 30 of lettuce, 30 of water-cress and 30 of escarole were examined for the presence of Aeromonas of the A. hydrophila group, using two different isolation methods. One of the methods envolved direct plating on starch-ampicinin agar for the purpose of enumeration and the other one, after enrichment in trypticase-soy broth with ampicillin, for detection, both using 24 hour incubation at 28&#176C. Aeromonas spp. Were detected in 43 (47.8%) samples and their numbers varied from less than 102 up to 2.0x106 CFU/g. The water-cress samples were the ones to show greater numbers of Aeromonas spp. The counts of 9 (21%) of the 43 positive samples exceeded 104 CFU/g, 7 of them consisting of water-cress. The number of water-cress positive samples (70.0%) was significantly higher at 5% than those of lettuce (43.3%) and those of escarole (30.0%). No significant differences were found in relation to positivity for Aeromonas spp. Between both isolation methods used, regarding the lettuce and the water cress samples. On the other hand, with respect to the escarole samples, positivity was significantly superior for the isolation method envolving enrichment. In therms of species level identification, among 143 strains confirmed as being Aeromonas spp., 138 (96.51%) were A, cavia, 4 (2.81%) were A, hvdrophila and 1 (O,7%) was considered as atypical due to its different biochemical profile. The results show that the vegetables examined may represent risk to consumers in terms of presence and numbers of Aeromonas of the A, hvdrophila group.

The U.S. aquaculture industry has become well established in the last three decades, and channel catfish aquaculture is the most significant component of this industry. Virulent Aeromonas hydrophila has been a serious disease problem since 2009 in the U.S. catfish aquaculture, and Aeromonas veronii and Edwardsiella piscicida are emerging pathogens of catfish. Therefore, this study aims to address fundamental questions on virulence mechanisms of these three fish pathogens, which I expect to support the development of control measures for preventing these diseases. In this study, E. piscicida and virulent Aeromonas hydrophila (vAh) genomes were sequenced, and comparative analyses were conducted using the genome sequences. Average nucleotide identity (ANI) calculations showed that E. piscicida strains share high sequence identity, yet they are from diverse host species and geographic regions. vAh isolates share very high sequence identity, while the other A. hydrophila genomes are more distantly related to this clonal group. We applied several comparative genomics approaches to evaluate E. piscicida genomes and E. ictaluri genomes, providing valuable information about unique and shared features of these two important pathogens in the Edwardsiella genus. Comprehensive secretion system analysis of 55 A. hydrophila genomes and deletion of tssD and tssI core elements of T6SS from vAh isolate ML09-119 has provided new knowledge. We sequenced the genome of virulent Aeromonas veronii strain ML09-123 from catfish indicated that it was highly similar to an A. veronii strain from China. Evaluation of all 41 A. veronii genomes available in the National Center for Biotechnology Information (NCBI) provides a base platform to investigate in detail the molecular mechanism of A. veronii biology and virulence. Lastly, we constructed deletion mutants vAhΔsia, vAhΔent, vAhΔcol, vAhΔhfq1, vAhΔhfq2, and vAhΔhfq1Δhfq2 to determine roles of A. hydrophila secreted proteins and regulatory proteins on virulence in catfish. Results showed that sialidase (vAhΔsia) and enterotoxin (vAhΔent) mutants were significantly attenuated.

Aeromonas hydrophila is a Gram-negative, rod shaped, facultative anaerobic bacterium that is ubiquitous to freshwater and slightly brackish aquatic environments and can cause infections in fish, humans, reptiles, and avian species. Recent severe outbreaks of disease in catfish aquaculture have been associated with a highly virulent Aeromonas hydrophila strain (VAH) that is genetically distinct from less virulent strains. Given that A. hydrophila is known to infect birds, we hypothesized that fish eating birds may serve as a reservoir for VAH and spread the pathogen by flying to uninfected ponds. Great Egrets were used in this transmission model because these wading birds frequently predate catfish farms. We found that Great Egrets that were fed VAH infected catfish shed VAH demonstrating their potential to spread VAH. Histologically there were changes found in selected tissue samples.

Aeromonas salmonicida, une bactérie pathogène du poisson, possède le système de sécrétion type trois (TTSS) essentiel à sa virulence. Il a été montré qu'une culture à 25°C de ces bactéries cause la perte du plasmide pAsa5 portant le TTSS engendrant ainsi une perte de virulence. Ce projet avait pour but de tester systématiquement l'effet de la chaleur sur certains facteurs de virulence. La thermolabilité du pAsa5 a été vérifiée par PCR pour des souches cultivées à 25°C. Leur virulence a été comparée à leur souche parentale avec l'amibe Dictyostelium discoideum. Les résultats ont montré que la perte de virulence est associée au réarrangement de pAsa5 qui s'est montré variable entre les souches et pour une même souche après différents traitements thermiques. Ce projet propose une nouvelle vision sur la thermolabilité du pAsa5. L'identification de l'origine du réarrangement permettra de contrer la virulence d'A. salmonicida lors de futurs projets.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Plasmids are an integral part of the horizontal gene pool and, therefore, are the main vectors for the spread of antibiotic and heavy metal resistance genes in the environment. Functional and taxonomic characterization of novel plasmids is, therefore, central to our general understanding of plasmid biology and their contribution to microbial evolution. Two 14-kb mobilizable plasmids, p31T1 and p36T2, conferring resistance to tetracycline were isolated from the opportunistic fish pathogens Aeromonas sobria and Aeromonas hydrophila and were found to have indistinguishable restriction fragment length polymorphism (RFLP) patterns (Marx, MSc Thesis). DNA sequence analysis of the two isogenic plasmids (only p36T2 was sequenced) revealed the presence of 18 putative open reading frames (ORFs), of which the tetAR tetracycline resistance genes, associated with a truncated Tn1721, were the only ORFs with significant similarity to known sequences within the NCBI database. Putative functions were assigned to 10 of the ORFs based on their distant homology with proteins of known function. Six of the 18 ORFs, spanning 5.7-kb, were found to comprise the minimal region required for replication (minimal replicon) by means of deletion analysis using derivatives of p31T1. Of the six ORFs, ORF2 and ORF4 were found to be essential for plasmid replication. Inactivation of ORF3 resulted in an increase of plasmid copy number (PCN) from ~3 to ~7 plasmids per chromosome and a decrease in plasmid stability from ~80 % to 16 % over approximately 127 generations (7 days). Furthermore, by means of β-galactosidase promoter fusion assays it was shown that ORF3 autoregulated its own promoter. These results, therefore, suggested that although ORF3 was not essential for replication, it may be involved in plasmid copy number regulation and control. Host range analysis indicated that p31T1 was able to replicate in two other members of the γ-proteobacteria group (Escherichia coli and Pseudomonas putida) but was unable to do so in an α-proteobacterium strain, thus suggesting a limited host range. Furthermore, p31T1 was mobilized only at low frequencies (5.4 x 10-5 transconjugants per donor) by an IncP-1 conjugative system though it is possible that the mobilization system of these plasmids is adapted to function optimally with alternate conjugative systems. Given the unique PCN, stability, host range and mobilization characteristics determined for p31T1 and that no other plasmid replication and mobilization systems with significant sequence similarity to these plasmids have yet been identified, it is likely that these two plasmids are the first representative members of a new family of plasmids found within aquacultureassociated Aeromonas species and which are involved in the spread of tetracycline resistance. / AFRIKAANSE OPSOMMING: Plasmiede vorm ‘n integrale deel van die horisontale geen poel en vorm daarom die hoof vektore vir die verspreiding van antibiotika- en swaarmetaal-weerstandbiedende gene in die omgewing. Funksionele en taksonomiese karakterisering van nuwe plasmiede is belangrik in die begrip van plasmied biologie en hul bydrae tot mikrobiese evolusie. Twee 14-kb mobiliseerbare plasmiedes, p31T1 en p36T2, met tetrasiklien weerstandigheid was vanaf die opportunistiese vis patogene Aeromonas sobria en Aeromonas hydrophila geïsoleer en het identiese restriksie fragment lengte polimorfisme (RFLP) patrone. DNA volgorde analise van die twee isogeniese plasmiede (slegs die volgorde van p36T2 was bepaal) het die teenwoordigheid van 18 moontlike oop leesrame (OLR) getoon. Die tetAR tetrasiklien weerstandbiedende gene, wat met ‘n verkorte Tn1721 transposon geassosieerd is, was die enigste OLR wat beduidende volgorde ooreenkoms met bekende volgordes binne die NCBI databasis getoon het. Moontlike funksies was toegeken aan 10 van die OLRe en was gebasseer op vêrlangse homologie met proteïene met bekende funksies. Ses van die 18 OLRe strek oor ‘n 5.7- kb minimale replikon fragment wat benodig word vir replisering en is deur middel van delesie analises van p31T1 derivate gevind. Van hierdie ses OLRe, word OLR2 en OLR4 benodig vir plasmied replisering. Inaktivering van OLR3 het ‘n toename in plasmied kopiegetal (PKG) vanaf ~3 tot ~7 plasmiede per kromosoom en ‘n afname in stabiliteit vanaf ~80% tot 16% oor 127 generasies (7 dae) tot gevolg gehad. Verder kon daar deur middel van β-galaktosidase fusie analises getoon word dat OLR3 sy eie promotor outoreguleer. Hierdie resultate stel dus voor dat alhoewel OLR3 nie benodig was vir replikasie nie, mag dit dalk by plasmied kopiegetal regulering en beheer betrokke wees. Bakteriële gasheer analises het getoon dat p31T1 in 2 addisionele lede van die γ-proteobakterieë groep (Escherichia coli en Pseudomonas putida) kon repliseer, maar nie in ‘n α-proteobacterium nie. Verder kon p31T1 teen ‘n lae frekwensie (5.4 x 105) gemobiliseer word deur ‘n IncP-1 konjugasie sisteem, maar dit mag wees dat die mobilisering eerder optimaal kan plaasvind met ‘n alternatiewe konjugasie sisteem. Na aanleiding van die unieke PKG, stabiliteit, gasheer en mobilisering eienskappe wat vir p31T1 bepaal is en die feit dat geen ander replisering en mobilisering sisteme met noemenswaardige volgorde homologie tot hierdie plasmiede gevind kon word nie, blyk dit dat hierdie van die eerste lede van ‘n nuwe familie van plasmiede binne die akwakultuur-geassosieerde Aeromonas spesies is, wat betrokke is by die verspreiding van tetrasiklien weerstandbiedendheid.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Orientador: Fabiana Pilarski / Banca: Jonas Augusto Rizzato Paschoal / Banca: Luiz Augusto do Amaral / Resumo: Os surtos de bacterioses na piscicultura são imprevisíveis, por essa razão é necessário dispor de opções terapêuticas eficazes para reduzir a morbidade e mortalidade. Para que a terapia seja eficaz, a escolha do antimicrobiano deve se basear nas informações farmacocinéticas do fármaco no hospedeiro, nas condições de produção e na sensibilidade do patógeno. No Brasil, atualmente só dois antimicrobianos são legalizados para uso na aquicultura, a oxitetraciclina (OTC) e o florfenicol (FFC), os quais muitas vezes são ineficazes. Destes, somente o FFC é autorizado para tratar bacterioses em tilápia-do-Nilo, a espécie mais produzida no país. Este cenário nos levou a investigar a atividade antimicrobiana do tianfenicol (TAF) contra as principais bactérias patogênicas de peixes cultivados no Brasil. Foi determinada a concentração inibitória mínima (CIM) e a concentração bactericida mínima (CBM) do TAF para 49 cepas isoladas de surtos de bacteriose ocorridos no período 2011 a 2017 em três estados. Adicionalmente, avaliou-se a atividade antimicrobiana do TAF (G1: 10 mg/kg), do FFC (G2: 10 mg/kg) e da combinação do TAF com o FFC (G3: TAF+FFC: 5 + 2,5 mg/kg e G4: 2,5 + 1,25 mg/kg) no tratamento de aeromonose em tilápia-do-Nilo experimentalmente infectadas com Aeromonas hydrophila. Como resultado do estudo in vitro, mais da metade das cepas testadas foram sensíveis ao TAF, sendo que os gêneros Aeromonas, Lactococcus e Vibrio foram os mais sensíveis. No estudo in vivo, o TAF foi eficaz no ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Outbreaks of bacterial diseases in fish farm are unpredictable; therefore, it is necessary to have effective therapeutic options to reduce the morbidity and mortality. For effective therapy, the anticipated pharmacokinetics and antibacterial activity of the antimicrobial in the target fish species under the given conditions must be considered before decide which antimicrobial to use. In Brazil, only two antimicrobials are approved for use in aquaculture, oxytetracycline (OTC) and florfenicol (FFC), which are often innefective. Moreover, only FFC is approved for use to treat bacterial diseases in Nile tilapia, the main specie in Brazil. This scenario led us to investigate the antibacterial activity o thiamphenicol (TAP) against the main bacteria infecting fishes in Brazil. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of TAP were determined for 49 strains isolated from diseases outbreaks registered during 2011 - 2017 in three States. Additionally the antibacterial activity of TAP (10 mg kg-1), FFC (10 mg kg-1) and TAF combined with FFC (G3: TAF+FFC: 5 + 2.5 mg kg-1 e G4: 2.5 + 1.25 mg kg-1) against Aeromonas hydrophila in Nile tilapia aeromoniosi models were evaluated. More than half of the tested strains were in vitro sensitive to TAP, being TAP highly potent against Aeromonas, Lactococcus, and Vibrio. The in vivo therapy with TAP alone and combined with FFC was effective to treat aeromoniosis in Nile tilapia. Groups G1, G2, G3, G4 and co... (Complete abstract click electronic access below) / Mestre

Orientador: Marco Antonio de Andrade Belo / Coorientador: Claudinei da Cruz / Banca: Silvia Patrícia Carraschi de Oliveira / Banca: Wilson Gomez Manrique / Banca: Eduardo Makoto Onaka / Banca: Annelise Carla Camplesi dos Santos / Resumo: O presente estudo teve por objetivos avaliar a eficácia terapêutica a segurança clínica e ecotoxicológica do antimicrobiano fosfomicina para o tratamento de aeromonose e streptococose em tilápia do Nilo (Oreochromis niloticus). Para tal, a segurança clínica foi avaliada com as doses de 10, 20 e 40 mg de fosfomicina.kg-1; os estudos de eficácia com a dose terapêutica de 10 mg de fosfomicina.kg-1, foram conduzidos com peixes desafiados com Aeromonas hydrophila e Streptococcus agalactiae; os ensaios de ecotoxicidade foram feitos para a determinação de CL50 em peixes (O. niloticus) e plantas aquáticas (Lemna minor) e de CE50 para crustáceos (Daphnia magna) e moluscos (Pomacea canaliculata). Nos estudos foram utilizadas tilápias de 112g ± 5,6g, acondicionadas em tanques de 400 L (n=10). Ambos os estudos de eficácia terapêutica com 10 mg.kg-1 demonstraram a eficácia para A. hydrophila e S. agalactiae, pois nas análises de reisolamento destes microrganismos não ocorreu crescimento dos mesmos em amostras de fígado, rim, baço e cérebro dos peixes tratados quando comparados aos grupos infectados e não tratados nos quais o número de unidades formadoras de colônias (UFC) foi de 7,6 ± 2,4 por placa. Na infecção por A. hydrophila apresentaram microcitose e linfopenia, assim como, trombocitose na fase inicial da infecção seguida de trombocitopenia. Lesões nos tecidos hepáticos e renais corroboraram as alterações da atividade enzimática sérica de ALT, AST, FA e nos níveis de creatinina, cole... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present study aimed to evaluate the therapeutic efficacy of clinical and ecotoxicological safety of antimicrobial fosfomycin for the treatment of aeromonose and streptococcosis in Nile tilapia (Oreochromis niloticus). For this, clinical safety was evaluated with doses of 10, 20 and 40 mg of fosfomycin.kg-1; Efficacy studies with the therapeutic dose of 10 mg of fosfomycin.kg-1 were conducted with fish challenged with Aeromonas hydrophila and Streptococcus agalactiae; The ecotoxicity assays were performed for the determination of LC50 in fish (O. niloticus) and aquatic plants (Lemna minor) and EC50 for crustaceans (Daphnia magna) and molluscs (Pomacea canaliculata). In the studies, tilapia of 112 g ± 5.6 g were used, packed in 400 L tanks (n = 10). Both therapeutic efficacy studies with 10 mg.kg-1 demonstrated efficacy for A. hydrophila and S. agalactiae, because in the reisolation analyzes of these microorganisms there was no growth in liver, kidney, spleen and brain samples of treated fish, While in the infected and untreated groups, mean growth was greater than ten colony forming units (CFU) per plaque. In the A. hydrophila infection they presented microcytosis and lymphopenia, as well as thrombocytosis in the initial phase of infection followed by thrombocytopenia. Liver and renal tissue damage corroborated the changes in serum enzyme activity of ALT, AST, FA and creatinine, cholesterol and triglyceride levels. In S. agalactiae infection, there was a decrease in the n... (Complete abstract click electronic access below) / Doutor