Detecting national human enteric disease outbreaks linked to animal contact in the United States of America.

Enteric pathogens, such as non-typhoidal Salmonella, Campylobacter and Escherichia coli, can reside in the intestinal tract of many animals, including livestock, companion animals, small mammals and reptiles. Often, these animals can appear healthy; nonetheless, humans can become infected after direct or indirect contact, resulting in a substantial illness burden. An estimated 14% of the 3.2 million illnesses that occur in the United States of America (USA) each year from such enteric pathogens are attributable to animal contact. Surveillance for enteric pathogens in the USA includes the compilation and interpretation of both laboratory and epidemiologic data. However, the authors feel that a collaborative, multisectoral and transdisciplinary - or One Health - approach is needed for data collection and analysis, at every level. In addition, they suggest that the future of enteric illness surveillance lies in the development of improved technologies for pathogen detection and characterisation, such as genomic sequencing and metagenomics. In particular, using whole-genome sequencing to compare genetic sequences of enteric pathogens from humans, food, animals and the environment, can help to predict antimicrobial resistance among these pathogens, determine their genetic relatedness and identify outbreaks linked to a common source. In this paper, the authors describe three recent, multi-state human enteric illness outbreaks linked to animal contact in the USA and discuss how integrated disease surveillance was essential to outbreak detection and response. Additional datasharing between public health and animal health laboratories and epidemiologists at the local, national, regional and international level may help to improve surveillance for emerging animal and human health threats and lead to new opportunities for prevention.

Les agents pathogènes entériques tels que les Salmonella non typhiques, Campylobacter et Escherichia coli peuvent coloniser le tractus intestinal d'un grand nombre d'animaux y compris les espèces d'élevage, les animaux de compagnie, les petits mammifères et les reptiles. Les animaux porteurs sont souvent sains en apparence ; néanmoins, les humains peuvent contracter l'infection après un contact direct ou indirect avec un animal atteint, ce qui induit un fardeau significatif associé à ces maladies. D'après les estimations, environ 14 % des 3,2 millions de cas annuels d'infections par des agents pathogènes entériques aux États-Unis d'Amérique ont pour origine un contact avec des animaux. Aux États-Unis, la surveillance des agents pathogènes entériques est basée sur la collecte et l'interprétation des résultats de laboratoire et des données épidémiologiques. Les auteurs sont néanmoins convaincus de la nécessité de recourir à une approche collaborative, multisectorielle et transdisciplinaire (en d'autres termes, une approche Une seule santé) pour la collecte et l'analyse des données, à tous les niveaux. Ils considèrent également que la surveillance des infections entériques reposera à l'avenir sur le développement de technologies avancées dans le domaine de la détection et de la caractérisation des agents pathogènes, notamment le séquençage génomique et la métagénomique. En particulier, le recours au séquençage du génome entier afin de comparer les séquences d'agents pathogènes d'origine humaine, alimentaire, animale et environnementale permettra d'anticiper l'apparition d'antibiorésistances, de déterminer le degré de parenté génétique de ces agents et d'identifier les foyers provenant d'une même source. Les auteurs décrivent trois foyers récents d'infections entériques humaines survenus dans plusieurs états des États-Unis et soulignent à quel point l'exercice d'une surveillance sanitaire intégrée a été déterminant pour la détection de ces foyers et la mise en œuvre d'une réponse appropriée. Un partage accru d'informations entre les laboratoires et les épidémiologistes de santé publique et animale aux niveaux local, national, régional et international pourrait contribuer à améliorer la surveillance des menaces émergentes pesant sur la santé animale et humaine et à mettre en œuvre de nouvelles modalités de prévention.

En el tracto intestinal de muchos animales, entre ellos ganado, mascotas, pequeños mamíferos o reptiles, puede haber patógenos intestinales como salmonelas no tifoideas, Campylobacter o Escherichia coli. A menudo los animales parecen sanos, pese a lo cual las personas pueden infectarse por contacto directo o indirecto con ellos, lo que da lugar a una considerable carga de morbilidad. Se calcula que, de los 3,2 millones de casos de enfermedad que estos patógenos intestinales causan al año en los EE. UU., un 14% es atribuible al contacto con animales. La vigilancia de patógenos intestinales que se practica en los EE. UU. incluye la compilación e interpretación de datos tanto epidemiológicos como de laboratorio. En opinión de los autores, sin embargo, es preciso que la obtención y el análisis de datos respondan a un planteamiento de colaboración multisectorial y transdisciplinar ­ esto es, a la lógica de Una sola salud ­ que abarque todos los niveles. Los autores apuntan además que el futuro de la vigilancia de las enfermedades intestinales pasa por el desarrollo de tecnologías más eficaces de detección y caracterización de patógenos, como la secuenciación genómica o la metagenómica. En particular, el uso de la secuenciación de genomas completos para comparar entre sí las secuencias genéticas de patógenos intestinales presentes en personas, alimentos, animales y el medio ambiente puede ayudar a predecir la aparición de resistencias a los antimicrobianos en estos patógenos, determinar su parentesco genético e identificar brotes vinculados con un origen común. Los autores, tras describir tres recientes brotes de enfermedad intestinal humana ligados al contacto con animales que afectaron a varios estados de los EE. UU., explican la función esencial que cumplió la vigilancia integrada de enfermedades para detectar esos brotes y responder a ellos. El intercambio de más datos entre los laboratorios de salud pública y sanidad animal y los epidemiólogos a escala local, nacional, regional e internacional puede ser de ayuda para mejorar la vigilancia de amenazas sanitarias y zoosanitarias emergentes y abrir nuevas posibilidades de prevención.

Use of urinary renal biomarkers to evaluate the nephrotoxic effects of melamine or cyanuric acid in non-pregnant and pregnant rats.

Although traditional assessments of renal damage detect loss of kidney function, urinary renal biomarkers are proposed to indicate early changes in renal integrity. The recent adulteration of infant formula and other milk-based foods with melamine revealed a link between melamine ingestion and nephropathy. Thus, the effects of melamine and related analogs (e.g., cyanuric acid) should be assessed in other potentially sensitive groups. We evaluated whether urinary Kim-1, clusterin, and osteopontin could detect the effects of high doses of melamine or cyanuric acid in pregnant and non-pregnant female rats gavaged with 1000 mg/kg bw/day for 10 days. We demonstrate that these biomarkers can differentiate the severity of effects induced by melamine or cyanuric acid. All melamine-treated animals experienced adverse effects; however, pregnant rats were most sensitive as indicated by increased SCr, BUN, and kidney weights, decreased body weight, and presence of renal crystals. These effects coincided with elevated urinary biomarker levels as early as day 2 of exposure. One cyanuric acid-treated rat displayed effects similar to melamine, including increased urinary biomarker levels. This work illustrates that these biomarkers can detect early effects of melamine or cyanuric acid crystal-induced nephropathy and further supports the use of urinary protein immunoassays as a powerful, non-invasive method to assess nephrotoxicity.

Depletion of melamine and cyanuric acid in kidney of catfish Ictalurus punctatus and trout Oncorhynchus mykiss.

A risk assessment conducted in 2007 identified significant knowledge gaps about tissue residues of melamine and related triazine analogs such as cyanuric acid in animals that had eaten contaminated food. The USFDA subsequently designed studies to determine residue levels in muscle, serum, and kidneys of catfish and trout given a single gavage dose of 20 mg/kg body weight (BW) of melamine, cyanuric acid, or 20 mg/kg BW of both compounds simultaneously. Renal triazines were determined by LC-MS/MS at postdose days 1, 3, 7, 14, 28 (and day 42 for trout). When dosed individually, melamine and cyanuric acid kidney residues depleted much faster than those in fish given both compounds together. Combined dose residue depletion was punctuated by extreme outliers due to the formation of persistent renal melamine cyanurate crystals.

Residue depletion of albendazole and its metabolites in aquacultured yellow perch (Perca flavescens).

Metabolism and residue depletion studies are conducted to determine the marker residue (MR) of a drug in a target tissue of food animals. The MR is used to monitor potential unauthorized use of drugs. The current work is a continuation of our efforts to study metabolism and depletion profiles of albendazole in multiple finfish species to determine a common MR. The results of this study suggest that albendazole sulfone metabolite could potentially serve as MR for albendazole in yellow perch muscle, similar to channel catfish and hybrid striped bass as reported previously by us.

Renal crystal formation after combined or sequential oral administration of melamine and cyanuric acid.

We evaluated renal melamine-cyanurate crystal spherulite formation after single and repeated ingestion of both melamine (MEL) and cyanuric acid (CYA) in catfish and trout. MEL and CYA were co-administered orally over a range of doses, 0.1-20mg/kg body weight (bw) of each compound, either once or repeatedly for 4, 14 or 28 days (d). In catfish, the No Observable Adverse Effects Levels (NOAELs) for crystal formation for single, 4d or 14 d dosing were 10, 2.5 and 0.5mg/kg bw, respectively. In trout, the respective NOAELs were 2.5, 2.5 and 0.5mg/kg bw. No renal crystals formed in catfish fed 0.1mg/kg bw of each compound for 28 d. Sequential administration of 20mg/kg bw of MEL followed by 20mg/kg bw of CYA or vise-versa, with waiting periods of 1, 3, 7, 14 or 21 d between compound dosing also induced renal crystal formation in fish. These studies show that both catfish and trout are sensitive, non-mammalian models, for renal crystal formation following MEL and CYA ingestion. Since fish generally excrete chemicals more slowly than mammals, they may provide a "worst case scenario" model for higher risk populations, such as infants or persons with compromised renal function.

Residue depletion of melamine and cyanuric acid in catfish and rainbow trout following oral administration.

The intentional addition of triazines such as melamine to animal feeds and the lack of information about residue accumulation in food animals caused global concerns for food safety during 2007 and 2008. We report the results of a good laboratory practices (GLP) study to determine melamine and cyanuric acid residues in catfish and trout filets harvested at 1, 3, 7, 14, 28, and 42 days after a single oral dose of 20 mg/kg body weight of melamine, cyanuric acid, or melamine and cyanuric acid together. Peak melamine concentrations were 12.73 mg/kg (ppm) in catfish (mean = 9.98), 12.26 mg/kg in trout (mean = 7.89) on day 1. Within 7 days (catfish) or 14 days (trout) residues were <2.5 mg/kg, a level in foods accepted by many risk assessors worldwide to be unlikely to pose health risks to consumers. Peak cyanuric acid residues also occurred on day 1, 0.68 mg/kg in catfish (mean = 0.46), 2.59 mg/kg in trout (mean = 0.86). Cyanuric acid muscle residues were <2.5 mg/kg by day 3. The half-lives for melamine and cyanuric acid ranged between 1 and 4 days. Renal crystals formed in fish given both melamine and cyanuric acid, persisting for weeks after the single dose.

In vitro kinetics of hepatic albendazole sulfoxidation in channel catfish (Ictalurus punctatus), tilapia (Oreochromis sp.), rainbow trout (Oncorhynchus mykiss) and induction of EROD activity in ABZ-dosed channel catfish.

Liver microsomes from market-size (n = 6) rainbow trout, channel catfish and tilapia were used to investigate in vitro biotransformation kinetics of albendazole (ABZ). ABZ was transformed to a single metabolite, ABZ sulfoxide (ABZ-SO). Catfish displayed the highest maximal velocity (V(max) = 264.0 +/- 58.6 pmols ABZ-SO/min/mg protein) followed by tilapia (112.3 +/- 8.2) and rainbow trout (73.3 +/- 10.3). V(max) in catfish was significantly different (P < 0.05) from the other two species. Michaelis-Menten constant (K(m)) values (microm) varied significantly among the species: rainbow trout (3.9 +/- 0.5), tilapia (9.2 +/- 1.7) and catfish (22.0 +/- 3.2). However, V(max)/K(m) ratios showed no difference among the three species, making them equally efficient performing this phase I biotransformation reaction. In a second series of experiments, channel catfish (n = 6 per treatment) were dosed in vivo with gel-food containing ABZ (10 mg/kg, p.o.). Fish were killed at 24, 48, 72 and 120 h after dosage. Control fish were fed ABZ-free feed. Induction of ethoxyresorufin-o-deethylase activity was significant (P < 0.05) in all ABZ-dosed treatments as compared with controls.

Metabolism and depletion of albendazole in the muscle tissue of channel catfish following oral treatment.

The residue depletion of albendazole (ABZ) and its metabolites was studied in channel catfish muscle tissue. Channel catfish were dosed once with 10 mg/kg ABZ via stomach tube with manual restraint. Muscle tissue samples were collected at 8, 16, 24, 48, 72, 96 and 120 h postdose. A high-performance liquid chromatographic method was used to assay ABZ and its major metabolites: ABZ sulfoxide (ABZ-SO), ABZ sulfone (ABZ-SO2) and ABZ aminosulfone (ABZ-2-NH2SO2) in the muscle tissue. The results indicate that ABZ and ABZ-SO were present in low concentrations, i.e. <15 and <10 microg/kg, respectively, at 8 h postdose in catfish muscle with and without skin. ABZ-SO2 was present at 1 microg/kg concentration levels until 48 h in muscle alone and 72 h in muscle with skin. ABZ-2-NH2SO2 was not detected at any withdrawal periods.

Standardization of a broth microdilution susceptibility testing method to determine minimum inhibitory concentrations of aquatic bacteria.

A multiple laboratory study was conducted in accordance with the standards established by the Clinical and Laboratory Standards Institute (CLSI), formerly the National Committee for Clinical Laboratory Standards (NCCLS), for the development of quality control (QC) ranges using dilution antimicrobial susceptibility testing methods for bacterial isolates from aquatic animal species. QC ranges were established for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 when testing at 22, 28 and 35 degrees C (E. coli only) for 10 different antimicrobial agents (ampicillin, enrofloxacin, erythromycin, florfenicol, flumequine, gentamicin, ormetoprim/sulfadimethoxine, oxolinic acid, oxytetracycline and trimethoprim/sulfamethoxazole). Minimum inhibitory concentration (MIC) QC ranges were determined using dry- and frozen-form 96-well plates and cation-adjusted Mueller-Hinton broth. These QC ranges were accepted by the CLSI/NCCLS Subcommittee on Veterinary Antimicrobial Susceptibility Testing in January 2004. This broth microdilution testing method represents the first standardized method for determining MICs of bacterial isolates whose preferred growth temperatures are below 35 degrees C. Methods and QC ranges defined in this study will enable aquatic animal disease researchers to reliably compare quantitative susceptibility testing data between laboratories, and will be used to ensure both precision and inter-laboratory harmonization.

Antimicrobial susceptibility testing of aquatic bacteria: quality control disk diffusion ranges for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C.

Quality control (QC) ranges for disk diffusion susceptibility testing of aquatic bacterial isolates were proposed as a result of a multilaboratory study conducted according to procedures established by the National Committee for Clinical Laboratory Standards (NCCLS). Ranges were proposed for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C for nine different antimicrobial agents (ampicillin, enrofloxacin, erythromycin, florfenicol, gentamicin, oxolinic acid, oxytetracycline, ormetoprim-sulfadimethoxine, and trimethoprim-sulfamethoxazole). All tests were conducted on standard Mueller-Hinton agar. With >/=95% of all data points fitting within the proposed QC ranges, the results from this study comply with NCCLS guidelines and have been accepted by the NCCLS Subcommittee for Veterinary Antimicrobial Susceptibility Testing. These QC guidelines will permit greater accuracy in interpreting results and, for the first time, the ability to reliably compare susceptibility test data between aquatic animal disease diagnostic laboratories.

Myxosporean plasmodial infection associated with ulcerative lesions in young-of-the-year Atlantic menhaden in a tributary of the Chesapeake Bay, and possible links to Kudoa clupeidae.

Ulcers in Atlantic menhaden Brevoortia tyrannus (Latrobe) (Clupeidae), observed along the USA east coast, have been attributed to diverse etiologies including bacterial, fungal and, recently, harmful algal blooms. To understand the early pathogenesis of these lesions, we examined juvenile Atlantic menhaden collected during their seasonal presence in Chesapeake Bay tributaries from April to October 1999 and from March to August 2000. We conducted histopathological examinations of young-of-the-year fish from the Pocomoke River tributary, which has a history of fish mortalities and high lesion prevalence. Kudoa clupeidae (Myxozoa: Myxosporea) spores were present in the muscles of fish collected in both years. Of the fish assessed by histology in April, 5 to 14% were infected, while in May 90 to 96% were infected. Infection rates remained high during the summer. Mature spores were primarily located within myomeres and caused little or no observable pathological changes. Ultrastructure showed spores with capsulogenic cells bearing filamentous projections, and a basal crescentic nucleus with mottled nucleoplasm containing cleaved, condensed chromatin. Also, a highly invasive plasmodial stage of a myxozoan was found in the lesions of juvenile Atlantic menhaden. The plasmodia were observed in fish collected between May and July, with the maximum occurrence in late June 1999 and late May 2000. Plasmodia penetrated and surrounded muscle bundles, causing grossly observable raised lesions in 73% of all fish infected with this invasive stage. Plasmodia were also detected in the visceral organs, branchial arches, and interocular muscles of some fish. Some of the invasive extrasporogonic plasmodial lesions were associated with ulcers and chronic inflammatory infiltrates. The plasmodial stage appeared to slough out of the tissue with subsequent evidence of wound healing. Ultrastructure showed plasmodia with an elaborate irregular surface, divided into distinct ectoplasm and endoplasm; the latter contained numerous spherical vegetative nuclei, secondary generative cells, and occasional cell doublets. Our ultrastructural studies indicate that the plasmodial organisms, which are important in the etiology of the skin lesions, are myxozoans, and they may represent early stages of K. clupeidae.

Metabolism and residue depletion of albendazole and its metabolites in rainbow trout, tilapia and Atlantic salmon after oral administration.

Metabolic and residue depletion profiles of albendazole (ABZ) and its major metabolites in three fish species, rainbow trout, tilapia and Atlantic salmon are reported. Based on these profiles, similarities (or dissimilarities) between species will determine the potential to group fish species. ABZ at 10 mg/kg body weight was incorporated into fish food formulated in a gelatin base or in gel capsule and fed as a single dose to six fish from each species. Rainbow trout were held three each in a partitioned 600-L tank. Tilapia and Atlantic salmon were housed in separate 20-L tanks. Samples of muscle with adhering skin were collected at 8, 12, 18, 24, 48, 72, and 96 h postdose from trout kept at 12 degrees C, at 4, 8, 12, 24, 48, 72, 96, 120, and 144 h postdose from tilapia kept at 25 degrees C and at 8, 14, 24, 48, 72, and 96 h postdose from Atlantic salmon kept at 15 degrees C. The samples were homogenized in dry ice and subjected to extraction and cleanup procedures. The final extracts were analyzed for parent drug ABZ and its major metabolites, albendazole sulfoxide (ABZ-SO), albendazole sulfone (ABZ-SO2) and albendazole aminosulfone using high-performance liquid chromatography with fluorescence detection. ABZ was depleted by 24 h in trout and tilapia and by 48 h in salmon; ABZ-SO, a pharmacologically active metabolite, was depleted by 48 h in tilapia, by 72 h in rainbow trout and was present until 96 h in salmon; and low levels of ABZ-SO2 and albendazole aminosulfone, both inactive metabolites, were detectable at least till 96 h in all three fish species.

A fish model of renal regeneration and development.

The fish kidney provides a unique model for investigating renal injury, repair, and development. Like mammalian kidneys, fish kidneys have the remarkable ability to repair injured nephrons, designated renal regeneration. This response is marked by a recovery from acute renal failure by replacing the injured cells with new epithelial cells, restoring tubule integrity. In addition, fish have the ability to respond to renal injury by de novo nephron neogenesis. This response occurs in multiple fish species including goldfish, zebrafish, catfish, trout, tilapia, and the aglomerular toadfish. New nephrons develop in the weeks after the initial injury. This nephrogenic response can be induced in adult fish, providing a more abundant source of developing renal tissue compared with fetal mammalian kidneys. Investigating the roles played by different parts of the nephron during development and repair can be facilitated using fish models with differing renal anatomy, such as aglomerular fish. The fish nephron neogenesis model may also help to identify novel genes involved in nephrogenesis, information that could eventually be used to develop alternative renal replacement therapies.

New nephron development in goldfish (Carassius auratus) kidneys following repeated gentamicin-induced nephrotoxicosis.

Renal development in mammalian kidneys can only be studied in embryonic animals. Hence, research in this area is hampered by the need to maintain pregnant animals and by the small size of the embryonic kidney. Here, we describe a goldfish (Carassius auratus) model for studying renal repair and nephron development in an adult animal. Previous studies have indicated that chemically induced nephrotoxicosis in goldfish is followed by new nephron development. We tested the hypothesis that new nephron development is not a one-time only event and, thus, will occur after repeated nephrotoxic events. We used repeated injections of gentamicin (50 mg/kg of body weight), a nephrotoxic antibiotic, which has been used as a model nephrotoxicant to study renal repair. Fish were allowed either a recovery period of 9 or 24 weeks between injections. In both experiments, new nephrons developed after each injection of gentamicin, supporting our hypothesis. Nephron development occurring after a 9-week recovery period was similar to development observed after a 24-week recovery period; therefore, the shorter experimental paradigm appears sufficient and can save time and money. Future research using this fish nephrogenesis model may identify the genes responsible for nephron neogenesis. Such information is a prerequisite for developing alternative renal replacement therapies based on the induction of de novo nephrogenesis in diseased kidneys.

Etiologies, observations and reporting of estuarine finfish lesions.

Lesions in estuarine finfish are associated with a variety of organisms including parasites and bacterial, viral, and fungal infectious agents. In addition, trauma, suboptimal water quality, and other abiotic stress factors may result in the loss of homeostasis. We have observed solitary ulcerative lesions on menhaden sampled from the Chesapeake Bay, Maryland, the Pimlico River, North Carolina, and the St. Johns River, Florida. Histologically, the lesions demonstrated a marked chronic inflammatory infiltrate and granulomas in response to fungal hyphae throughout large areas of exposed necrotic muscle. Gram-negative rod-shaped bacteria were also observed in the lesions, a common finding in ulcers of aquatic organisms. Similar observations in menhaden and other species have been described previously in the literature as ulcerative mycosis, mycotic granulomatosis, red spot disease, and epizootic ulcerative syndrome. Despite the many different known causes of fish lesions, the popular press and the scientific literature have recently emphasized Pfiesteria piscicida and other Pfiesteria-like dinoflagellates (and their bioactive compounds) as the primary causative agent for finfish lesions, particularly mycotic granulomatous ulcers in Atlantic menhaden. While some laboratory data suggest that Pfiesteria may play a role in field-observed lesions, much more cause-and-effect evidence is needed to determine the importance of other risk factors, both alone or and in combination with Pfiesteria. In order to better understand the etiology of lesion initiation and progression in estuarine finfish, accurate assessments of environmental conditions collected on appropriate temporal and spatial scales, and fish morphological indicators consistent with gross and histological pathologic terminology, should be used for reporting fish lesion observations and kills. Further, this outlook will help to avoid bias and may foster a broader perspective for examining the health of estuarine systems in general.

Superoxide production in phagocytes obtained from Mycobacterium marinum-stimulated goldfish (Carassius auratus) that were exposed to copper.

OBJECTIVE: To investigate the effects of copper exposure and recovery from copper toxicosis on the nonspecific immune response in Mycobacterium marinum-inoculated goldfish. ANIMALS: Goldfish (Carassius auratus) with a mean weight of 33.5 g. PROCEDURE: Superoxide (O2-) production was measured in fish 2 to 6 weeks after injection with phosphate-buffered saline (PBS) solution or M marinum (10(2) to 10(7) colony-forming units [CFU]/fish). Then, paired groups of fish were injected with PBS solution or 10(4) CFU of M marinum and exposed to copper (100 microg/L) for 7 days or for 4 days with 3 days of recovery. One paired group not exposed 14 days later to copper served as control fish. Phagocyte production of O2-was measured by use of the nitroblue tetrazolium reduction assay. Inflammation and bacterial colony counts were determined by use of routine histologic and microbiologic procedures. RESULTS: Superoxide production achieved a maximal response 2 to 4 weeks after M marinum inoculation. Compared with control fish, O2- production increased in the groups exposed to copper but then decreased in the exposed groups that were allowed to recover. Superoxide response and peritoneal inflammation were greater in M marinum-inoculated groups than in non-inoculated groups. CONCLUSIONS: Copper exposure and inoculation with M marinum increased O2- production, whereas recovery after exposure decreased O2- production, even in fish that were immunostimulated by M marinum. CLINICAL RELEVANCE: When the antimicrobial oxidative response is suppressed after copper exposure, steps should be taken to avoid imposing additional stress and minimize the possibility of resurgent or secondary pathogenic infections.

Pathogenicity of Mycobacterium fortuitum and Mycobacterium smegmatis to goldfish, Carassius auratus.

Despite the ubiquitous presence of atypical mycobacteria in the environment and the potential risk of infection in humans and animals, the pathogenesis of diseases caused by infection with atypical mycobacteria has been poorly characterized. In this study, goldfish, Carassius auratus were infected either with the rapidly growing fish pathogen, Mycobacterium fortuitum or with another rapidly growing mycobacteria, Mycobacterium smegmatis. Bacterial persistence and pathological host response to mycobacterial infection in the goldfish are described. Mycobacteria were recovered from a high percentage of inoculated fish that developed a characteristic chronic granulomatous response similar to that associated with natural mycobacterial infection. Both M. fortuitum and M. smegmatis were pathogenic to fish. Fish infected with M. smegmatis ATCC 19420 showed the highest level of giant cell recruitment compared to fish inoculated with M. smegmatis mc(2)155 and M. fortuitum. Of the three strains of mycobacteria examined, M. smegmatis ATCC 19420 was the most virulent strain to goldfish followed by M. fortuitum and M. smegmatis mc(2)155, respectively.

Fish lesions in the Chesapeake Bay: Pfiesteria-like dinoflagellates and other etiologies.

Ulcerative lesions and mass mortalities of Atlantic estuarine fish, particularly menhaden (Brevoortia tyrannus), have been associated with exposure to Pfiesteria-like dinoflagellates and their toxins. We collected fish from the Chicamacomico River, Maryland, and observed solitary ulcerative lesions on the majority of menhaden sampled. One striped bass (Morone saxatilis) had an area of reddening around the base of the dorsal fin. Bluegill (Lepomis machrochirus), channel catfish (Ictalurus punctatus), yellow perch (Perca flavescens), and carp (Cyprinus carpio) were externally nonremarkable. Histologically ulcerative menhaden lesions demonstrated marked chronic inflammatory infiltrate in large areas of exposed necrotic muscle. The ulcers contained granulomata with fungal hyphae in the necrotic tissue. Gram negative rod-shaped bacteria were also observed in the lesions, a common finding in ulcers of aquatic organisms. Our data suggest that typical ulcerative lesions observed on fish from areas of Pfiesteria-like dinoflagellate blooms are reflective of dermatosis, which may be related to a variety of individual or combined environmental stressors. Exposure to dinoflagellate toxin)s) potentially represents one such stressor. The role of Pfiesteria-like dinoflagellate toxin in fish primary lesion development is currently under investigation.

Goldfish, Carassius auratus, a novel animal model for the study of Mycobacterium marinum pathogenesis.

We have developed an animal model for studying mycobacterial pathogenesis using Mycobacterium marinum and the goldfish, Carassius auratus. Goldfish are injected intraperitoneally with doses between 10(2) and 10(9) CFU of M. marinum organisms. Depending on the dose of M. marinum organisms administered, an acute or chronic disease is produced. The acute disease is characterized by systemic mycobacterial infection, severe peritonitis, tissue necrosis, and a short median survival time. The chronic disease is characterized by granuloma formation in all organs and survival of animals to the end point of the experiment (56 days). Colony counts in organ homogenates showed recovery of mycobacteria from a high percentage of inoculated animals. We believe this well-characterized animal model will be useful for studying mycobacterial pathogenesis.