Venkata Vaddella

Assessing Salmonella typhimurium persistence in poultry carcasses under multiple thermal conditions consistent with composting and wet rendering

Mitigation of Salmonella associated with poultry carcasses is primarily accomplished by rendering or carcass composting. While rendering temperatures and pressures are well established for pathogen inactivation in poultry carcasses, parameters controlling composting processes are less defined in part because multiple conditions and procedures are utilized. Consequently, limited knowledge exists describing the impacts of composting with varying temperature and mixing protocols with respect to the inactivation of Salmonella in poultry carcasses. To improve the existing knowledge of Salmonella survival in poultry carcasses, inactivation of Salmonella enterica serovar Typhimurium (ST) LT2 was investigated. The impacts of various composting temperatures (55, 62.5°C) and low-rendering (i.e., pasteurization) temperatures (70, 78°C) on Salmonella inactivation were tested in a bench-top setting using a ground carcass slurry and whole birds under mixed and non-mixed conditions. Results showed that the ground carcass slurry and the whole carcass exposed to temperatures consistent with composting had no detectable Salmonella after 110 h with a level of detection of one CFU/mL of ground carcass slurry and one CFU/g of whole carcasses, respectively. In addition, grinding of carcasses as opposed to whole carcasses was more predictable with respect to Salmonella heat inactivation. Furthermore, results showed that constant mixing decreased the overall time required to eliminate Salmonella under composting and low-rendering temperatures.

Water and Sediment Microbial Quality of Mountain and Agricultural Streams

Increased public health risk caused by pathogen contamination in streams is a serious issue, and mitigating the risk requires improvement in existing microbial monitoring of streams. To improve understanding of microbial contamination in streams, we monitored in stream water columns and streambed sediment. Two distinct streams and their subwatersheds were studied: (i) a mountain stream (Merced River, California), which represents pristine and wild conditions, and (ii) an agricultural stream (Squaw Creek, Iowa), which represents an agricultural setting (i.e., crop, manure application, cattle access). Stream water column and sediment samples were collected in multiple locations in the Merced River and Squaw Creek watersheds. Compared with the mountain stream, water column concentrations in the agricultural stream were considerably higher. In both mountain and agricultural streams, concentrations in bed sediment were higher than the water column, and principal component analysis indicates that land use affected water column levels significantly ( < 0.05). The cluster analysis showed grouping of subwatersheds for each basin, indicating unique land use features of each watershed. In general, water column levels in the mountain stream were lower than the USEPAs existing water quality criteria for bacteria. However, the levels in the agricultural stream exceeded the USEPAs microbial water quality criteria by several fold, which substantiated that increased agricultural activities, use of animal waste as fertilizers, and combined effect of rainfall and temperature may act as potential determining factors behind the elevated levels in agriculture streams.

Correction to: Escherichia coli persistence kinetics in dairy manure at moderate, mesophilic, and thermophilic temperatures under aerobic and anaerobic environments (Bioprocess and Biosystems Engineering, (2015), 38, 3, (457-467), 10.1007/s00449-014-1285-3)

Escherichia coli persistence kinetics in dairy manure at moderate, mesophilic, and thermophilic temperatures.