Growth Media of Escherichia coli Does Not Affect Its Survival in Soil under Static Conditions.

ABSTRACT: Many studies have examined the survival of Escherichia coli and foodborne pathogens in agricultural soils. The results of these studies can be influenced by various growth conditions and growth media used when preparing cultures for an experiment. The objectives of this study were to (i) determine the growth curves of rifampin (R)-resistant E. coli in three types of growth media containing R: tryptic soy agar (TSA-R); tryptic soy broth (TSB-R); and poultry pellet extract (PPE-R) and (ii) evaluate the influence of growth media on the survival of E. coli in agricultural soil. Poultry pellet extract (PPE) was prepared by filter sterilizing a 1:10 suspension of heat-treated poultry pellets in sterile water. Generic E. coli (TVS 353) acclimated to 80 µg/mL of R was grown in TSA-R, TSB-R, and PPE-R at 3.0 to 3.5 log CFU/mL and incubated at 37°C. Growth curves were determined by quantifying E. coli populations at 0, 4, 8, 16, 24, and 32 h. Soil microcosms were inoculated with E. coli (6.0 log CFU/g) previously cultured in one of the three media types and stored at 25°C, and soil samples were quantified for E. coli on days 0, 1, 3, 7, 14, 28, and 42. Growth curves and survival models were generated by using DMFit and GInaFiT, respectively. E. coli growth rates were 0.88, 0.77, and 0.69 log CFU/mL/h in TSA-R, TSB-R, and PPE-R, respectively. E. coli populations in the stationary phase were greater for cultures grown in TSA-R (9.4 log CFU/mL) and TSB-R (9.1 log CFU/mL) compared with PPE-R (7.9 log CFU/mL). The E. coli populations in the soil remained stable up to 3 days before declining. An approximate 2 log CFU/g decline of E. coli in soil was observed for each culture type between days 3 and 7, after which E. coli populations declined more slowly from days 7 to 42. A biphasic shoulder model was used to evaluate E. coli survival in soils on the basis of growth media. Using standardized culture growth preparation may aid in determining the complex interactions of enteric pathogen survival in soils.

The transformative effects of illness.

In "The Soft Core" Arturo Vivante examines the bonds between a middle-aged son and his aging father. Years of habit that had solidified into accustomed but uncomfortable ways of behaving and interacting with each other are altered when the father's stroke evokes a tumultuous range of emotions in the son, leading him, in the end, to feel compassion, not just for his father but also for himself. Vivante shows the reader that illness has the ability to transform an individual who is willing to reexamine and reevaluate the meaning he or she gives to life. This process, however, is not an easy one, as it is often undertaken as in the story, when the individual fears the death of self or of a loved one. The suffering, though, can transform. The self-awareness gained leads to a more gentler way of being, and compassion results. This compassion is borne of understanding, recognition, and appreciation that the frailties of human nature exist in each of us. Recognizing and applying this to all manner of relationships in our lives is the wisdom that compassion gives to our existence.