Tips from the Journals of the American Society for Microbiology

11/18/04

E.coli in Dried Sausage Able to Withstand Digestion Process

Acidic conditions encountered during the digestive process may not be enough to inactivate some harmful bacteria in fermented dry sausages say Canadian researchers. Their findings appear in the November 2004 issue of the journal Applied and Environmental Microbiology.

Escherichia coli O157:H7 is one of the leading causes of foodborne diseases and can result in severe complications in humans ranging from hemorrhagic colitis to death. Previous outbreaks have been primarily associated with ground beef and raw milk, but a recent increase in cases involving highly acidic foods such as fermented dry sausages, mayonnaise, and apple cider have raised new concerns.

In the study fermented dry sausages were inoculated with E. coli O157:H7 and exposed to synthetic saliva for 1 minute, synthetic gastric juice for 120 minutes, and synthetic pancreatic juice for 250 minutes. Results showed that not only did existing E. coli O157:H7 cells remain viable after exposure to both synthetic saliva and gastric juice, they began to grow at a significant rate when exposed to the pancreatic juice.

"From a food safety point of view, this implies that the industrial processes used to manufacture dry sausages must be designed in such a way that no viable E. coli O157:H7 cell can ever be found in an average portion of sausage for human consumption, because no additional protection will be afforded by the subsequent digestive process," say the researchers. "This new information will be very valuable in refining our assessment of the risk associated with the manufacture of fermented dry sausages with regard to E. coli O157:H7."

(F. Naim, S. Messier, L. Saucier, G. Piette. 2004. Postprocessing in vitro digestion challenge to evaluate survival of Escherichia coli O157:H7 in fermented dry sausages. Applied and Environmental Microbiology, 70. 11: 6637-6642.)

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Shock Therapy Effective Against Bacteria on Stainless Steel Implants

Electric currents may help prevent the growth of harmful bacteria from occurring on surgical stainless steel say researchers from The Netherlands. Their findings appear in the November issue of the journal Applied and Environmental Microbiology.

Steel implants and pins are commonly used by orthopedic surgeons to repair human bone structure. Infection occurs in patients at an alarming rate of up to 71%, often causing serious complications effecting the surrounding tissue and bone. The formation of biofilms at the implant site make the infections even more difficult to treat with antibiotics, as bacteria inside biofilms are shielded from host defense mechanisms.

"The literature indicates that 500 to 5,000 times higher levels of antibiotics are needed to achieve the same antimicrobial effects on biofilm organisms as on planktonic microorganisms," say the researchers.

In the study researchers examined whether or not electric currents (direct currents and block currents) would be effective at causing a Staphylococcus epidermidis biofilm to detach from surgical stainless steel. Results showed a detachment rate of 78% after 360 minutes of exposure to 100 microamps of direct currents, and a 31% detachment rate after receiving 100 microamps of block currents. The bacteria remaining on surface showed to be only 2 to 3% viable following treatment.

"We have described a method by which bacterial biofilms can be stimulated to detach from surgical stainless steel by use of a small electric current to disconnect the link between the biofilm and the conducting," say the researchers. "This method can be used in combination with conventional pin site care to prevent or cure infections by applying the current between a circular electrode placed around the pin and the pin itself."

(A.J. van der Borden, H. van der Werf, H.C. van der Mei, H.J. Busscher. 2004. Electric current-induced detachment of Staphylococcus epidermidis biofilms from surgical stainless steel. Applied and Environmental Microbiology, 70. 11: 6871-6874.)

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Computer Modeling Helps Identify New Smallpox Drug Candidate

Using bioinformatics and computer modeling, researchers from North Carolina and Oregon have identified a new class of compounds that block a key step in the lifecycle of the smallpox virus and have little toxicity to human cells. They report on this new antiviral drug candidate in the November issue of the Journal of Virology.

An outbreak of the smallpox virus is considered to be one of the greatest threats facing the world today. No antiviral drug has proven effective against human smallpox. One antiviral currently available for treatment of orthopoxviruses offers some defense but must be administered intravenously and has a high risk of adverse side effects.

Recent research has discovered that viruses need specific enzymes, called proteinases, to reproduce. In this study, the researchers created a computer model of the structure of one proteinase (I7L) that that is used by orthopoxviruses, the family of viruses that includes smallpox. The model was computationally queried against a database of approximately 51,000 compounds to narrow the field down to 3,460 potential I7L inhibitors. Additional testing identified a group of chemically related compounds, one of which was TTP-6171, that appear to block replication of orthopoxviruses by inhibiting I7L without being toxic to human cells.

"Based on the results reported here, the chemical compound family represented by TTP-6171 represents a promising avenue toward developing an effective antiviral drug that can be used to prevent or treat diseases caused by orthopoxviruses, such as smallpox," say the researchers.

(C.M. Byrd, T.C. Bolken, A.M. Mjalli, M.N. Arimilli, R.C. Andrews, R. Rothlein, T. Andrea, M. Rao, K.L. Owens, D.E. Hruby. 2004. New class of orthopoxvirus antiviral drugs that block viral maturation. Journal of Virology, 78. 22: 12147-12156

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