The side chain of the antifungal antibiotic ansatrienin A from Streptomyces collinus contains a cyclohexanecarboxylic acid (CHC)-derived moiety. This moiety is also observed in trace amounts of omega-cyclohexyl fatty acids (typically less than 1% of total fatty acids) produced by S. collinus. Coenzyme A-activated CHC (CHC-CoA) is derived from shikimic acid through a reductive pathway involving a minimum of nine catalytic steps. Five putative CHC-CoA biosynthetic genes in the ansatrienin biosynthetic gene cluster of S. collinus have been identified. Plasmid-based heterologous expression of these five genes in Streptomyces avermitilis or Streptomyces lividans allows for production of significant amounts of omega-cyclohexyl fatty acids (as high as 49% of total fatty acids). In the absence of the plasmid these organisms are dependent on exogenously supplied CHC for omega-cyclohexyl fatty acid production. Doramectin is a commercial antiparasitic avermectin analog produced by fermenting a bkd mutant of S. avermitilis in the presence of CHC. Introduction of the S. collinus CHC-CoA biosynthetic gene cassette into this organism resulted in an engineered strain able to produce doramectin without CHC supplementation. The CHC-CoA biosynthetic gene cluster represents an important genetic tool for precursor-directed biosynthesis of doramectin and has potential for directed biosynthesis in other important polyketide-producing organisms.
In April 2014 an outbreak of low pathogenic avian influenza H5N8 North American genetic lineage was diagnosed in a commercial quail operation in Stanislaus County, California. Sudden increase in mortality prompted the submission of 20 Japanese quail hens (Coturnix c. japonica) to the California Animal Health and Food Safety Laboratory, Turlock Branch. Oropharyngeal and cloacal swabs tested positive for influenza A virus H5N8 by real-time reverse transcription-polymerase chain reaction. The virus was subsequently isolated. In vivo assay and sequencing of the hemagglutinin protein cleavage site classified the virus as a North American genetic lineage of low pathogenicity for chickens. Following the diagnosis, a rapid and coordinated response took place to contain the outbreak. The affected premise was depopulated, cleaned, and disinfected. Three areas from the affected premises-a 3 kilometer (km) radius (High Risk Zone), a 3-10 km area (Buffer Zone), and a 10-20 km (Surveillance Zone)-were established for avian influenza testing of commercial and noncommercial poultry operations. Surveillance testing and rapid control measures were successful in the control and eradication of the outbreak and revealed no area of spread of the virus from the index flock. This report describes the history, diagnosis, surveillance, and control measures applied to manage this outbreak.
Although a potential market for on-farm food safety services is perceived, veterinarians are unsure of their role in this area. new demands of meat packers slaughtering cull dairy cows may be the motivation practitioners need to broach the subject of food safety with clients.
Floors of trucks or trailers were sampled for Salmonella before culled dairy cows were loaded from cooperating farms and auction markets in New York (East) and California (West) prior to transport to slaughter establishments. Sampling occurred during two periods, winter and summer. These vehicles were sampled again after cattle were unloaded at slaughter establishments. Four of six vehicles picking up cattle from dairy farms were positive for Salmonella spp. before cattle were loaded at East locations during winter, while five of seven were positive during the summer. One of five vehicles picking up cattle from auction markets was positive for Salmonella spp. at an East location during winter, while all four sampled during the summer period were positive. During winter at the West location all trucks or trailers were positive for Salmonella . During the summer sampling, nine of 13 vehicles that arrived at dairy farms and four of six that arrived at auction markets to pick up cattle were positive for Salmonella before cattle were loaded. Biosecurity procedures need to address the risk of Salmonella contamination from cattle transport.
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