Inhibition of Listeria monocytogenes and Escherichia coli O157:H7 on Beef by Application of Organic Acids †.

Lean beef surfaces were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and then sanitized with fumaric, acetic, or lactic acid alone and in combined solutions of those acids at 55°C for 5 s. The initial inoculum level was 8.62 log CFU/cm2 and 5.13 log CFU/cm2 for L. monocytogenes and E. coli O157:H7, respectively. Fumaric acid at a concentration of 1% was the most effective acid in reducing the populations of L. monocytogenes by up to 1 log unit and E. coli O157:H7 by up to 1.3 log units when compared with acetic or lactic acids. The rank order of acids tested against the growth of L. monocytogenes and E. coli O157:H7 was fumaric acid followed by lactic and acetic acids. Fumaric acid at concentrations of 1.0% and 1.5% was more effective than any of the combined solutions of acids.

Reduction of Bacterial Populations on Vacuum-Packaged Ground Beef Patties with Fumaric and Lactic Acids.

The effects of fumaric and lactic acid on the total numbers of aerobic, psychrotrophic, and coliform bacteria on vacuum-packaged ground beef patties at 0, 1, 3, 5, 7, 10, and 14 days of storage at 4°C were studied. Fumaric acid treatments resulted in greater reductions in microbial growth than lactic acid treatments. When 5.0% fumaric acid was used, the lag phase was prolonged and microbial growth was reduced (P < 0.05), with total aerobic, psychotrotrophic, and coliform populations reaching net maximum growths of only 1.46, 1.44, and 0.98 log units, respectively, after storage at 4°C for 10 days. Increasing the acid concentrations significantly decreased the growth of all microorganisms. The 5.0% lactic acid was the most inhibitory against coliforms, resulting in a 3.88-1og unit reduction after 10 days of storage.

Vagal syncope during recurrent pulmonary embolism.

The mechanism for syncope during pulmonary embolism is not well understood. We describe two patients with transient sinus bradycardia and atrioventricular (AV) block during syncope from recurrent pulmonary embolism. Consciousness was regained each time the rhythm returned to normal. We believe that the syncope and bradyarrhythmia was caused by a parasympathetic reflex, since simultaneous slowing of the sinus rate with concomitant AV block is a common manifestation of increased vagal tone. Such a reflex is consistent with known cardiac reflexes, may occur frequently, and may be one of the mechanisms for syncope in patients with pulmonary embolism.