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Port Adelaide, Australia

Rodgers G.G.,James Cook University | Roberts S.D.,Primary Industries and Regions SA | Dixon C.D.,South Australian Research And Development Institute
Marine and Freshwater Research | Year: 2013

Temperature, salinity and food availability are generally considered to have the most influence on larval growth and survival in penaeid species. Larval size has previously been used as a measure of animal quality in a range of crustacean species. The aim of this project was to investigate the effects of temperature (17°C, 20°C, 22.5°C and 25°C) on stage-specific larval size in Penaeus latisulcatus collected from the Spencer Gulf, in South Australia. Five different measurements of larval size were assessed: body length, body width, antenna length, carapace length and abdomen length. Results showed that larval growth rate was dependant on temperature, with growth rate greater at higher temperatures. Despite this, larvae reared at 20°C reached the largest size, while those at the temperature extremes (17°C and 25°C) were smallest. When considering average annual temperature, the spawning time that would most likely maximise larval size in the Spencer Gulf is approximately December. This coincides with current management arrangements for the fishery that protect the spawning biomass at this time of year. © 2013 CSIRO.

Gole V.C.,University of Adelaide | Torok V.,South Australian Research And Development Institute | Sexton M.,Primary Industries and Regions SA | Caraguel C.G.B.,University of Adelaide | Chousalkar K.K.,University of Adelaide
Journal of Clinical Microbiology | Year: 2014

This study involves longitudinal and point-in-time surveys of Salmonella carriage and environmental contamination on two commercial cage layer farms positive for Salmonella enterica subsp. enterica serovar Typhimurium (flock A age, 32 weeks; flock B age, 34 weeks). Salmonella-positive fecal, egg belt, and dust samples were all unconditionally associated with eggshells testing positive for Salmonella. The odds of an eggshell testing positive for Salmonella were 91.8, 61.5, and 18.2 times higher when fecal, egg belt, and dust samples, respectively, tested positive for Salmonella. The agreement between the culture-based methods and real-time PCR on preenriched broths for detecting Salmonella was almost perfect for eggshell (observed agreement, 99.19%; kappa coefficient, 0.94) and egg belt samples (observed agreement, 95%; kappa coefficient, 0.88), and it was substantial for fecal (observed agreement, 87.14%; kappa coefficient, 0.47) and floor dust samples (observed agreement, 80.61%; kappa coefficient, 0.58). A 1-log increase in the load of Salmonella detected in the fecal, egg belt, and floor dust samples resulted in 35%, 43%, and 45% increases, respectively (P < 0.001), in the odds of an eggshell testing positive for Salmonella. The multilocus variable-number tandem-repeat analysis (MLVA) patterns of the S. Typhimurium strains isolated from flock A were distinct from those of flock B. S. Typhimurium strains detected from human food poisoning cases exhibited an MLVA pattern similar to those of the strains isolated from flocks A and B. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Gole V.C.,University of Adelaide | Caraguel C.G.B.,University of Adelaide | Sexton M.,Primary Industries and Regions SA | Fowler C.,University of Adelaide | Chousalkar K.K.,University of Adelaide
International Journal of Food Microbiology | Year: 2014

The shedding of Salmonella in a single age commercial egg layer flock was investigated at the onset of lay (18. weeks) followed by two longitudinal samplings at 24 and 30. weeks. At the age of 18. weeks, when the first sampling was performed, the prevalence of Salmonella in faeces was 82.14% whereas all egg belt and dust samples were Salmonella positive by culture method. In later samplings, at the age of 24 and 30. weeks, the prevalence of Salmonella in faeces was significantly reduced (p. <. 0.001) to 38.88% and 12.95% respectively, however all egg belt and dust samples remained positive by culture method. The prevalence of Salmonella in faeces collected from the low tier cages was significantly higher (p = 0.009) as compared with samples from the high tier cages. In all types of samples processed by culture method, S. Mbandaka was the most frequently (54.40%) isolated serovar followed by S. Worthington (37.60%), S. Anatum (0.8%), and S. Infantis (0.8%). All samples were also tested by real-time PCR method. The observed agreement between culture method and real-time PCR in detecting Salmonella-positive dust and egg belt samples was 100%. There was almost perfect agreement (observed agreement = 99.21%) for the detection of Salmonella-positive eggshells. Observed agreement between culture method and real-time PCR for detecting Salmonella-positive shoe cover and faecal samples was, however, moderate (80%) and low (54.27%) respectively. Real-time PCR results showed that there was a significant increase in the load of Salmonella on egg belt, dust and shoe cover samples at the 24 and 30. weeks of lay as compared to the 18. weeks of lay. Real-time PCR provided a more rapid and reliable method of detection of Salmonella on all dry sample types whereas the traditional culture method proved much more reliable when trying to detect Salmonella in wet faecal samples. © 2014.

Gole V.C.,University of Adelaide | Chousalkar K.K.,University of Adelaide | Roberts J.R.,University of New England of Australia | Sexton M.,Primary Industries and Regions SA | And 3 more authors.
PLoS ONE | Year: 2014

Salmonella is an important foodborne pathogen, causing an estimated 11,992 cases of infection in Australia per year. Egg or egg product related salmonellosis is a major concern for the egg industry. Worldwide, S. Typhimurium is one of the most common serovars identified in Salmonella food poisoning cases. The current study investigated the ability of five S. Typhimurium strains to penetrate washed and unwashed eggs using whole egg and agar egg penetration methods. All S. Typhimurium strains were able to penetrate eggshells and survive in egg albumen (at 20°C) according to whole egg penetration results. Polymerase Chain Reaction results demonstrated that S. Typhimurium strain 2 (103 and 105 CFU/mL), and strain 5 (103 and 105 CFU/mL) egg penetration was significantly higher (p<0.05) in washed eggs when compared to unwashed eggs. Statistical analysis of the agar penetration experiment indicated that S. Typhimurium was able to penetrate washed eggs at a significantly higher rate when compared to unwashed eggs (p<0.05). When compared to unwashed eggs, washed eggs also had significantly damaged cuticles. Statistical analysis also indicated that eggshell penetration by S. Typhimurium was related to various eggshell ultrastructural features such as cap quality, alignment, erosion, confluence, Type B bodies and cuticle cover. © 2014 Chousalkar et al.

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