Certain formulations of nanoscale powders possess antimicrobial properties. These formulations are made of simple, nontoxic metal oxides such as magnesium oxide (MgO) and calcium oxide (CaO, lime) in nanocrystalline form, carrying active forms of halogens, for example, MgO. Cl2 and MgO. Br2. When these ultrafine powders contact vegetative cells of Escherichia coli, Bacillus cereus, or Bacillus globigii, over 90% are killed within a few minutes. Likewise, spore forms of the Bacillus species are decontaminated within several hours. Dry contact with aflatoxins and contact with MS2 bacteriophage (surrogate of human enterovirus) in water also causes decontamination in minutes.

Presumptive identification of Escherichia coli O157:H7 is possible in an individual, nonmultiplexed PCR if the reaction targets the enterohemorrhagic E. coli (EHEC)eaeA gene. In this report, we describe the development and evaluation of the sensitivity and specificity of a PCR-based 5′ nuclease assay for presumptively detecting E. coli O157:H7 DNA. The specificity of the eaeA-based 5′ nuclease assay system was sufficient to correctly identify all E. coliO157:H7 strains evaluated, mirroring the previously described specificity of the PCR primers. The SZ-primed,eaeA-targeted 5′ nuclease detection assay was capable of rapid, semiautomated, presumptive detection of E. coliO157:H7 when ≥103 CFU/ml was present in modified tryptic soy broth (mTSB) or modified E. coli broth and when ≥104 CFU/ml was present in ground beef-mTSB mixtures. Incorporating an immunomagnetic separation (IMS) step, followed by a secondary enrichment culturing step and DNA recovery with a QIAamp tissue kit (Qiagen), improved the detection threshold to ≥102 CFU/ml. Surprisingly, immediately after IMS, the sensitivity of culturing on sorbitol MacConkey agar containing cefeximine and tellurite (CT-SMAC) was such that identifiable colonies were demonstrated only when ≥104 CFU/ml was present in the sample. Several factors that might be involved in creating these false-negative CT-SMAC culture results are discussed. The SZ-primed,eaeA-targeted 5′ nuclease detection system demonstrated that it can be integrated readily into standard culturing procedures and that the assay can be useful as a rapid, automatable process for the presumptive identification of E. coli O157:H7 in ground beef and potentially in other food and environmental samples.

Implementing control strategies for E coli O157:H7 at all levels of the cattle industry will decrease the risk of this organism entering the human food chain. Devising effective on-farm strategies to control E coli O157:H7 in cow-calf herds will require an understanding of the epidemiologic characteristics of this pathogen.

No abstract

Inhibition of Clostridium perfringens spore germination and outgrowth by lactic acid salts (calcium, potassium, and sodium) during exponential cooling of injected turkey product was evaluated. Injected turkey samples containing calcium lactate, potassium lactate, or sodium lactate (1.0, 2.0, 3.0, or 4.8% [w/w]), along with a control (product without lactate), were inoculated with a three-strain cocktail of C. perfringens spores to achieve a final spore population of 2.5 to 3.0 log CFU/g. The inoculated product was heat treated and exponentially cooled from 54.5 to 7.2 degrees C within 21, 18, 15, 12, 9, or 6.5 h. Cooling of injected turkey (containing no antimicrobials) resulted in C. perfringens germination and an outgrowth of 0.5, 2.4, 3.4, 5.1, 5.8, and 5.8 log CFU/g when exponentially cooled from 54.4 to 7.2 degrees C in 6.5, 12, 15, 18, and 21 h, respectively. The incorporation of antimicrobials (lactates), regardless of the type (Ca, Na, or K salts), inhibited the germination and outgrowth of C. perfringens spores at all the concentrations evaluated (1.0, 2.0, 3.0, and 4.8%) compared to the injected turkey without acetate (control). Increasing the concentrations of the antimicrobials resulted in a greater inhibition of the spore germination and outgrowth in the products. In general, calcium lactate was more effective in inhibiting the germination and outgrowth of C. perfringens spores at > or = 1.0% concentration than were sodium and potassium lactates. Incorporation of these antimicrobials in cooked, ready-to-eat turkey products can provide additionalprotection in controlling the germination and outgrowth of C. perfringens spores during cooling (stabilization).