Toxicity of the 13 priority pollutant metals to Vibrio fisheri in the Microtox chronic toxicity test.

The Microtox Acute Toxicity Test has been successfully used to measure the toxicity of metals and other pollutants at high concentrations (ppm) in selected environmental samples. However, metals and other toxicants are often found in much lower concentrations (ppb) in many municipal wastewaters and receiving waters. In order to assess the toxicity of these pollutants in these samples, a more sensitive toxicity assay is needed. The Microtox chronic toxicity test has been developed to measure the sublethal effect of toxicants over multiple generations of the test species, Vibrio fisheri. In this study, the toxicity of the 13 priority pollutant metals [i.e. As, Se, Cd, Cr (III and VI), Cu, Pb, Sb, Ag, Tl, Zn, Be, Hg and Ni] to V. fisheri was evaluated using the Microtox chronic toxicity test. In this test, the inhibitory concentration (IC), lowest observable effect concentration (LOEC), and no observable effect concentration (NOEC) were obtained after 22-h of incubation at 27+/-1 degrees C, by comparing the light output of the control to that of the test sample. Among the 13 priority pollutant metals, beryllium (Be) was found to be the most toxic in the test (LOEC=0.742-1.49 microg/l) while thallium (Tl) was the least toxic (LOEC=3840-15300 microg/l). The LOECs for copper (as Cu) and lead (Pb) in reagent (ASTM Type I) water were 6.78-13.6 microg/l and 626-1251 microg/l, respectively. The toxicity of copper sulfate (as Cu) in reagent water was shown and significantly reduced with the addition of natural organic matter (fulvic acid) or EDTA to the sample. The LOEC values for the 13 priority pollutant metals in this test were comparable to or lower than those reported for commonly used aquatic toxicity tests, such as the Ceriodaphnia dubia assay.

Fate of Selected Bacterial Pathogens and Indicators in Fractionated Poultry Litter During Storage.

A study of broiler litter re-utilization potential was conducted with the goal of determining if storage of litter significantly reduced potential pathogens to levels safe for re-utilization. Litter from four broiler houses was separated into a fine fraction for fertilizer use and a coarse fraction for use as a supplement to wood shavings in growing subsequent flocks of birds. Fractions and whole litter were stored in indoor piles for four months with periodic analysis for culturable pathogenic and indicator bacteria. Significant reductions in microbial concentrations occurred in a majority of samples tested during four months of storage (in most cases to below detection limits of approximately 30 CFU/g dry weight). Poultry feed was found to be one possible source of litter contamination.

Cytotoxicity and Antibiotic Resistance Profiles of Aeromonas hydrophila Isolates From a Broiler Processing Operation.

The cytotoxicity and antibiotic resistance profiles of Aeromonas hydrophila isolates recovered from broiler carcasses and chill water samples taken from a Georgia processing plant were determined. Carcasses were sampled at pre- and post-evisceration locations, immediately after immersion chilling, and after being boxed, iced and refrigerated for 48 h. Grab samples of chill water were randomly selected for A. hydrophila recovery. Resistance of isolates to nine antibiotics was determined with the Bauer disc diffusion method (i.e., to ampicillin, cephalothin, streptomycin, kanamycin, chloramphenicol, naladixic acid, tetracycline, neomycin, and gentamicin). Multiple antibiotic resistance occurred in 46.2% of 119 isolates. The majority of the multiple antibiotic-resistant isolates (76.4%) were resistant only to ampicillin and cephalothin. The remaining multiple antibiotic-resistant isolates (23.6%) were resistant to various combinations of 2, 3, or 4 antibiotics, most of which were recovered from carcasses immediately after evisceration. Cytotoxin activity was detected in 63.8% of all isolates using the Y-1 mouse adrenal tumor cell line. Cytotoxin positive isolates were recovered from all sampling locations including chill water. The highest cytotoxicity titers were shown among isolates recovered from carcasses immediately after evisceration. These data suggest bird fecal contamination as an important source of A. hydrophila in broilers and broiler processing plants rather than environmental contamination.

Bacterial Pathogens and Indicators in Catfish and Pond Environments.

Channel catfish ( Ictalurus punctatus ) fed a diet containing 26 or 38% protein with restricted and satiety feeding methods were examined for microorganisms on the fish surface and viscera. Water, sediment, and fish samples from the ponds were tested for fecal streptococci, fecal coliforms, Aeromonas hydrophila , and Pseudomonas aeruginosa , while fish samples were also analyzed for presumptive Listeria spp. (count on m-VJ agar) and psychrotrophic bacteria. There were no significant differences (P<0.05) in the fecal streptococci and fecal coliform counts for the water, sediment, and fish visceral samples. However, the aeromonad count for the visceral samples (4.20 log CFU/g wet weight) was significantly higher (P<0.05) than that of the water and sediments (2.40 log CFU/ml and 3.78 log CFU/g wet weight, respectively). Similarly, the P. aeruginosa count for the fish visceral samples was significantly higher (P<0.05) than that of the water and sediments. The mean presumptive Listeria spp. count for the fish visceral samples was 1.99 log CFU/g wet weight. Because of the higher bacterial concentrations in the fish viscera, it was concluded that cross-contamination of fish samples could occur during evisceration. Finally, the feed protein level and feeding method used in the ponds influenced the bacterial concentrations in selected sample types (i.e., water, sediment, fish surface rinse, or fish viscera).

Prevalence of Salmonella enteritidis and Other Serovars in Ovaries of Layer Hens at Time of Slaughter.

Ovaries aseptically collected from commercial layer hens at time of slaughter were assayed for Salmonella as an indication of systemic infection of birds within a flock. Birds were randomly selected at the time of slaughter from 42 flocks from seven southeastern states and Pennsylvania. Ovaries were pooled, four per pool, mascerated, and Salmonella , isolates were recovered by conventional methods. Thirty-two of 42 flocks (76.2%) were positive at >10% infection rate based on sampling methods. Fifteen different serovars were detected in flocks. Salmonella heidelberg was the predominant serovar, representing 56.5% of the salmonellae detected. However, S. agona , S. oranienburg , S. mbandaka , S. kentucky , S. montevideo , S. london , S. typhimurium , S. infantis , S. schwarzenqrund , S. ohio , S. cerro , S. anatum , and Salmonella untypeable were also found. S. enteritidis , phage type 23 was recovered from only one (2.4%) of the flocks. Single and multiple serovar infections were found with up to five serovars recovered from a single flock. Twenty-one positive flocks (50%) were positive with a single Salmonella serovar; of these S. heidelberg represented 76.2%. An overall mean of 26.6% of the pooled ovary samples within each infected flock was positive for salmonellae, with an overall range of 0-100%. The significance of Salmonella serovars other than S. enteritidis found at the levels reported has yet to be determined.

Recovery of Aeromonas hydrophila from Carcasses and Processing Water in a Broiler Processing Operation.

Aeromonas hydrophila , a potential pathogen associated with cases of human diarrhea, was enumerated using a rinse method on broiler carcasses and in processing water at selected locations in a commercial processing plant. A. hydrophila was detected on 98% of all carcasses tested, and 92% of all chill water samples; scald and rinse water samples were negative for this organism. Mean numbers on carcasses ranged for 28 CFU/ml of rinse fluid, detected immediately after the chiller, to 580 CFU/ml of rinse fluid at the post-evisceration stage. Water chilling and washing resulted in a significant reduction in A. hydrophila numbers on carcasses, while refrigerated storage (48 h) resulted in a significant increase. Data suggest that isolates recovered from carcasses may likely have been of intestinal origin and that the evisceration step was a probable cause of contamination. A. hydrophila levels on carcasses and processing waters showed no correlation to other bacteriological parameters which might be used in a process evaluation program.