Tips from the Journals of the American Society for Microbiology

05/13/05

Organisms in Soil May Protect Lettuce from E. coli

Researchers from Norway believe that naturally occurring organisms present in soil may protect lettuce from contamination by a common foodborne pathogen. Their findings appear in the May 2005 issue of the journal Applied and Environmental Microbiology.

Several recent outbreaks of Escherichia coli O157:H7 have raised concerns that contaminated fertilizer may be affecting crops of fruits and vegetables. The bacterium is commonly found in manure used as fertilizer and can survive for extended periods of time.

In the study lettuce seedlings were planted in soil fertilized with E. coli O157:H7 contaminated manure and grown for fifty days. Although the pathogen was detected in the soil for up to eight weeks, it was determined that the bacterium did not contaminate the roots, outer leaves, or edible parts of the lettuce. Pseudomonas fluorescens, a bacterium shown to inhibit E. coli O157:H7 when tested in vitro, was identified in soil found on the lettuce roots.

"In conclusion, transmission of E. coli O157:H7 from manure to lettuce was not observed when seedlings were transplanted into soil fertilized with manure inoculated with low concentrations of the pathogen," say the researchers. "The results also indicated that some of the organisms native in the soil microflora have antagonistic effects against pathogenic bacteria introduced into soil."

(G.S. Johannessen, G.B. Bengtsson, B.T. Heier, S. Bredholt, Y. Wasteson, L.M. Rorvik. 2005. Potential uptake of Escherichia coli O157:H7 from organic manure into crisphead lettuce. Applied and Environmental Microbiology, 71. 5: 2221-2225.)


Antiviral Therapy Following Dental Treatment May Inhibit Herpesviruses

Treatment with an antiviral drug following dental work may decrease levels of herpesviruses in saliva say researchers from Kentucky. Their findings appear in the May 2005 issue of the Journal of Clinical Microbiology.

With over ninety-five percent of the adult population infected with human herpesviruses (HHVs), the need for prevention and treatment is paramount. Formulating a vaccine is difficult because there are eight known strains of the virus and saliva appears to be the most prominent mode of transmission.

In the study valacyclovir, an antiviral drug, was administered to one-hundred and twenty-five random patients twice on the day of dental treatment and twice the day after. Saliva samples were collected on the day of treatment and three and seven days following and tested for HHVs. It was determined that dental treatment did not affect asymptomatic viral presence, but treatment with valacyclovir did keep levels of the Epstein-Barr virus (EBV) strain low at both postoperative visits. EBV, the virus that causes mononucleosis, is one of the most common and highly contagious human viruses found in people of all ages.

"These results suggest that HHVs are simultaneously present in the saliva of healthy adults at levels that could facilitate transmission, and valacyclovir therapy decreases the prevalence of EBV in saliva but has little effect on HHV-6 and HHV-7," say the researchers.

(C.S. Miller, S.A. Avdiushko, R.J. Kryscio, R.J. Danaher, R.J. Jacob. 2005. Effect of prophylactic valacyclovir on the presence of human herpesvirus DNA in saliva of healthy individuals after dental treatment. Journal of Clinical Microbiology, 43. 5: 2173-2180.)

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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