Isolation and characterization by conventional methods and genetic transformation of Psychrobacter and Acinetobacter from fresh and spoiled meat, milk and cheese

Abstract

Of 126 samples of fresh and spoiled meat and dairy products, 40% were positive for the presence of Moraxella-like bacteria and 64% of Acinetobacter; 279 and 466 strains, respectively, were isolated and a part of these were tested by biochemical methods and DNA transformation assays. In some cases, the Moraxellaceae in the samples examined reached considerable quantitative levels, but their percentage in the microflora was generally low. Moraxella-like bacteria were predominant in fresh meat, Acinetobacter in spoiled meat and milk. Most acinetobacters belonged to biotype lwoffii (sensu lato) and all 90 strains tested were positive for DNA transformation with an auxotrophic Acinetobacter. Moraxella-like bacteria were identified as Psychrobacter immobilis in 96% of 103 transformation assays. Moraxellaceae show lipolytic activity but they are considered of low incidence in food spoilage. Only 3.7% of acinetobacters from dairy sources was able to produce ropy milk. Unlike strains from clinical isolates, psychrobacters and acinetobacters isolated from food often do not grow at 37 degrees C.