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Tips from the Journals of the American Society for Microbiology

American Society for Microbiology

IDENTIFIED GENE MAY CONTRIBUTE TO SALMONELLA IN EGGS

Researchers from the University of California at Berkeley have identified a gene that may allow salmonella bacteria to contaminate chicken eggs. Their findings appear in the December 2003 issue of the journal Infection and Immunity.

Salmonella enterica serovar Enteritidis in eggs is one of the leading causes of food-borne illnesses in the United States. S. enterica is the only strain able to invade eggs and survive despite the antibacterial defenses found in egg whites which limit the growth and survival of other bacteria.

In the study, S. enterica was combined with albumen from egg whites and then monitored for survival. After confirming that S. enterica was able to overcome exposure to the albumen, the researchers began identifying genes that might contribute to the resistance. One of the genes, identified as yafD, had the ability to repair DNA damage caused by the albumen enabling the bacterium to thrive.

"We report here the identification of yafD as a gene essential for the resistance of S. enterica serovar Enteritidis to egg albumen," say the researchers. "We provide evidence that YafD may play a role in the repair of DNA damage caused by egg albumen and hence may facilitate the survival of S. enterica serovar Enteritidis in chicken eggs."

(S. Lu, P.B. Killoran, L.W. Riley. 2003. Association of Salmonella enterica serovar enteritidis YafD with resistance to chicken egg albumen. Infection and Immunity, 71. 12: 6734-6741.)


DIFFERENT BACTERIA CAUSE DISEASE IN GRAPES/ALMONDS

Scientists at the University of California, Berkeley, have discovered that while Pierce's disease of grapevines (PD) and almond leaf scorch (ALS) are caused by the same species of bacteria, the bacteria are two distinctly different strains. They report their findings in the December 2003 issue of the journal Applied and Environmental Microbiology.

Pierce's disease, where bacteria cause blockage in the roots denying water and nutrients to the grapevine canes and leaves, and ALS, which also results from congestion in the water flow, are both believed to be caused by the organism, Xylella fastidiosa.

"PD and ALS have long been considered to be caused by the same strain of this pathogen, but recent genetic studies have revealed differences among X. fastidiosa isolated from these host plants," say the researchers.

In the study, X. fastidiosa isolates from grapes and almonds, previously thought to be identical, were tested to see if almond strains could cause PD in grapevines and vice versa. The researchers determined that the organisms are not biologically interchangeable.

"Our results show that genetically distinct strains from grapes and almonds differ in population behavior and pathogenicity in grapes and in the ability to grow on two different media," say the researchers.

(R.P.P. Almeida, A.H. Purcell. 2003. Biological Traits of Xylella fastidiosa strains from grapes and almonds. Applied and Environmental Microbiology, 69. 12: 7447-7452.)


SCIENTISTS IDENTIFY CAUSE OF LIMP LOBSTERS

Researchers from the University of Maine and the U.S. Food and Drug Administration have identified bacteria that may be the cause of a recently identified disease in lobsters. Their findings appear in the December 2003 issue of the journal Applied and Environmental Microbiology.

In the late 1990's an unexplained disease causing weakness, lethargy and slow responses to stimuli began appearing in American lobsters pulled from the Gulf of Maine. In the study, the researchers identified a group of Vibrio fluvialis-like bacteria in samples taken from sick lobsters as the cause of this disease. While V. fluvialis has been know to cause disease in fish and humans, this is the first time it has been identified as the cause of a disease in shellfish.

"The findings support the hypothesis that these V. fluvialis-like organisms were responsible for the originally described systemic disease, which is now called limp lobster disease," say the researchers. "Understanding how this organism is able to overcome species barriers and adapt to new hosts is crucial to the production of disease-free seafoods."

(B.D. Tall, S. Fall, M.R. Pereira, M. Ramos-Valle, S.K. Curtis, M.H. Kothary, D.M.T. Chu, S.R. Monday, L. Kornegay, T. Donkar, D. Prince, R.L. Thunberg, K.A. Shangraw, D.E. Hanes, F.M. Khambaty, K.A. Lampel, J.W. Bier, and R.C. Bayer. 2003. Characterization of Vibrio fluvialis-like strains implicated in limp lobster disease. Applied and Environmental Microbiology, 69. 12: 7435-7446.)


TRICLOSAN: THE NEXT NEW DRUG?

The antibacterial compound triclosan, used in dermatological and oral hygiene products as well as antibacterial soaps and cleaner, shows promise as a drug for treating systemic bacterial infections say researchers from India. Their findings appear in the December 2003 issue of the journal Antimicrobial Agents and Chemotherapy.

In the study, mice received a dose of triclosan two hours prior to being infected with Escherichia coli and continued to receive injections every 12 hours following. Results showed a forty-eight hour increase in survival time of mice receiving triclosan as opposed to a twenty-four to thirty hour survival time of mice receiving other antibiotics.

"We believe that the excellent safety track record of triclosan in topical use coupled with our findings qualifies triclosan as a candidate or lead compound for exploring its potential in experimental systems for treating systemic bacterial infections."

(S. Sharma, T.N.C. Ramya, A. Surolia, N. Surolia. 2003. Triclosan as a systemic antibacterial agent in a mouse model of acute bacterial challenge. Antimicrobial Agents and Chemotherapy, 47. 12: 3859-3866.)

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