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  • Author or Editor: Renate Reimschuessel x
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Objective—To develop epidemiologic cutoff values by use of frequency distributions for susceptibility to 4 antimicrobial agents when tested against a representative population of a major aquaculture pathogen, Aeromonas salmonicida.

Sample Population—217 typical and atypical A salmonicida isolates obtained from 20 states and 12 countries.

Procedures—Species identification of A salmonicida isolates was confirmed by detection of specific nucleotide sequences by use of a PCR assay. Minimal inhibitory concentration (MIC) and diameter of the zone of inhibition for oxytetracycline, ormetoprim-sulfadimethoxine, oxolinic acid, and florfenicol were determined for each isolate in accordance with standardized antimicrobial susceptibility testing methods that have been approved by the Clinical and Laboratory Standards Institute for bacterial isolates from aquatic animals. Susceptibility data were tabulated in a scattergram and analyzed by use of error rate bounding.

Results—Susceptibility tests for oxytetracycline, ormetoprim-sulfadimethoxine, and oxolinic acid revealed 2 distinct populations of bacteria. Isolates tested against florfenicol clustered into a single population. Oxolinic acid susceptibility data revealed higher MICs in the non–United States A salmonicida isolates. Slow-growing (atypical) A salmonicida isolates were generally more susceptible than typical isolates for all antimicrobials, except oxolinic acid.

Conclusions and Clinical Relevance—Use of frequency distributions of susceptibility results to develop epidemiologic cutoff values appears to be applicable to aquatic isolates. Frequency distributions of susceptibility results for A salmonicida revealed clear divisions between isolate susceptibilities. This type of data, considered in conjunction with pharmacokinetic and efficacy data, may be useful for developing clinical breakpoints for use in aquaculture.

Full access
in American Journal of Veterinary Research



To investigate the effects of copper exposure and recovery from copper toxicosis on the nonspecific immune response in Mycobacterium marinum-inoculated goldfish.


Goldfish (Carassius auratus) with a mean weight of 33.5 g.


Superoxide (O2-) production was measured in fish 2 to 6 weeks after injection with phosphate-buffered saline (PBS) solution or M marinum (102 to 107 colony-forming units [CFU]/fish). Then, paired groups of fish were injected with PBS solution or 104 CFU of M marinum and exposed to copper (100 µg/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.


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.


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. (Am J Vet Res 1999;60:669–675)

Free access
in American Journal of Veterinary Research


Objective—To determine whether renal crystals can be experimentally induced in animals fed melamine or the related triazine compound cyanuric acid, separately or in combination, and to compare experimentally induced crystals with those from a cat with triazine-related renal failure.

Animals—75 fish (21 tilapia, 24 rainbow trout, 15 channel catfish, and 15 Atlantic salmon), 4 pigs, and 1 cat that was euthanatized because of renal failure.

Procedures—Fish and pigs were fed a target dosage of melamine (400 mg/kg), cyanuric acid (400 mg/kg), or melamine and cyanuric acid (400 mg of each compound/kg) daily for 3 days and were euthanatized 1, 3, 6, 10, or 14 days after administration ceased. Fresh, frozen, and formalin-fixed kidneys were examined for crystals. Edible tissues were collected for residue analysis. Crystals were examined for composition via Raman spectroscopy and hydrophilic-interaction liquid chromatography–tandem mass spectrometry.

Results—All animals fed the combination of melamine and cyanuric acid developed goldbrown renal crystals arranged in radial spheres (spherulites), similar to those detected in the cat. Spectral analyses of crystals from the cat, pigs, and fish were consistent with melamine-cyanurate complex crystals. Melamine and cyanuric acid residues were identified in edible tissues of fish.

Conclusions and Clinical Relevance—Although melamine and cyanuric acid appeared to have low toxicity when administered separately, they induced extensive renal crystal formation when administered together. The subsequent renal failure may be similar to acute uric acid nephropathy in humans, in which crystal spherulites obstruct renal tubules.

Full access
in American Journal of Veterinary Research


Case Description—In April 2012, Salmonella enterica serotype Infantis was detected in an unopened bag of dry dog food collected during routine retail surveillance. PulseNet, a national bacterial subtyping network, identified humans with Salmonella Infantis infection with the same genetic fingerprint as the dog food sample.

Clinical Findings—An outbreak investigation identified 53 ill humans infected with the outbreak strain during January 1 to July 5, 2012, in 21 states and 2 provinces in Canada; 20 (38%) were children ≤ 2 years old, and 12 of 37 (32%) were hospitalized. Of 21 ill people who remembered the dog food brand, 12 (57%) reported a brand produced at a plant in Gaston, SC. Traceback investigations also identified that plant. The outbreak strain was isolated from bags of dry dog food and fecal specimens obtained from dogs that lived with ill people and that ate the implicated dry dog food.

Treatment and Outcome—The plant was closed temporarily for cleaning and disinfection. Sixteen brands involving > 27,000 metric tons (> 30,000 tons) of dry dog and cat food were recalled. Thirty-one ill dogs linked to recalled products were reported through the FDA consumer complaint system.

Clinical Relevance—A one-health collaborative effort on epidemiological, laboratory, and traceback investigations linked dry dog foods produced at a plant to illnesses in dogs and humans. More efforts are needed to increase awareness among pet owners, health-care professionals, and the pet food industry on the risk of illness in pets and their owners associated with dry pet foods and treats.

Full access
in Journal of the American Veterinary Medical Association