VARIATION OF ENDOSULFAN RESIDUES IN WATER AND SEDIMENT TAKEN FROM THE MOSS LANDING DRAINAGE OF MONTEREY COUNTY
Data from previous studies conducted by the State Mussel Watch Program (SMW) implied increasing endosulfan residues inmollusks used as indicator organisms of chemical contamination in the Moss Landing Drainage area of Monterey County. As a first step in confirming a chronological trend, studies were conducted by the California Departments of Food and Agriculture (CDFA) and Fish and Game (CDFG) to determine within-site variability of endosulfan concentrations, and to estimate sample size necessary for future research. Personnel from the Environmental Hazards Assessment Program (EHAP) of CDFA collected sediment and water samples while personnel from the Pesticide Investigations Unit (PIU) of CDFG collected mollusk and fish samples at the same sites in a coordinated effort. This report contains results from the EHAP study. Three sites previously monitored by SMW in Monterey County were selected for the collection of sediment and water samples. All samples were analyzed for endosulfan I, II and sulfate. Only 33, 33 and 25% of the sediment samples contained detectable residues of endosulfan I, II and sulfate, respectively. Endosulfan concentrations in sediment were not uniformly distributed in the Moss Landing Drainage area with residues occurring more frequently in agricultural areas, away from tidal action and dredging activities. Only 25% of the water samples contained detectable endosulfan residues in the form of endosulfan sulfate. However, it is conceivable that endosulfan residues exist in water (either dissolved or on suspended sediment) below the detection limit given the consistent find of residues in mollusks and fish in this area and the established bio-concentration factors for fish species. Minimum sample sizes of 22 and 11 for sediment and water, respectively, were estimated as necessary to calculate the true mean for a given site. Future study of temporal or spatial trends in endosulfan residues of this drainage area might best be concentrated on sediment and biological organisms since residues in water are mostly below the current detection limits.
Human health risk assessment of endosulfan: II. Dietary exposure assessment.
The California Department of Pesticide Regulation (CDPR) and the United States Environmental Protection Agency (USEPA) performed dietary exposure assessments for endosulfan in 1998 and 2002, respectively. Results of the USEPA assessment showed an increased risk for the population sub-group "Children 1-6 years" (>100% of the Population Adjusted Dose [PAD]). USEPA then required registrants to satisfy database uncertainties by performing subchronic neurotoxicity and developmental neurotoxicity studies and, based on the results, USEPA decreased the Food Quality Protection Act (FQPA, 1996) Safety Factor from 10x to 1x. Additionally, several tolerances on commodities consumed in quantity by children were cancelled in 2006. CDPR re-evaluated the dietary risk initially performed in 1998 after review of these same studies. Based on a review of the revised USEPA tolerances, decreased usage, decreased consumption, cancellations, and prior health protective margins of exposure (MOEs>100), CDPR determined that it was not necessary to redo the 1998 exposure assessment. In 2007, USEPA conducted a new human health risk assessment for endosulfan combining food+drinking water residues that characterized dietary risk as %PAD=([Exposure/PAD]x100). For all relevant USEPA population sub-groups, the %PADs were<100% (health protective benchmark).
Coexistence of Virulence and Antibiotic Resistance Genes in Pasteurella multocida Isolated from Diseased Rabbits
Pasteurella multocida (P. multocida)is considered a predominant pathogenic bacterial agent causing respiratory manifestations (snuffles) in rabbits with considerable economic losses and unfavorable prognosis in Egypt. A few recent P. multocida strains exhibit resistance to the most commonly used antibiotics in the veterinary field. Therefore, the present study was carried out to investigate the prevalence of both virulence and antibiotic resistance genes among P. multocida isolated from diseased rabbits in Sharkia Governorate, Egypt. Only 10 out of 100 tested rabbits` nasal swabs were finally confirmed positive for P. multocida of serogroup A by polymerase chain reaction (PCR). Antibiotic susceptibility testing of the recovered isolates revealed that they were all multidrug resistant (MDR) with a predominance of resistance to amoxicillin, ampicillin, amoxicillin/clavulanic acid, neomycin and tetracycline (100% each), followed by kanamycin and streptomycin (90% each). All the recovered isolates were further subjected to PCR screening of some common virulence and antibiotic resistance genes of interest . With the exception of toxA gene, the other virulence associated genes (ptfA, Omp87 and nanB) were found among all the examined isolates. Totally, all MDR P. multocida isolates contained at least one antibiotic resistance gene with aphA1 being the most prevalent (100%), followed by ermX gene (40%). Antibiotic resistance genotyping demonstrated the presence of multiple antibiotic resistance genes among majority of the isolates (40%) with only one isolate harboring 4 genes encoding identical resistance phenotypes. Evidentially, all MDR P. multocida isolates possessed at least 3 virulence genes accompanied by the attendance of antibiotic resistance genes. These findings evidenced that rabbits are potential sources of pathogenic P. multocida strains harboring virulence and antibiotic resistance genes. Therefore, it is evident that there is an urgent need for the judicious use of antibiotics in rabbits` treatment systems to successfully mitigate the propagation of drug resistance across P. multocida species.