Featured Research

from universities, journals, and other organizations

'Bacteria-eating' Viruses May Spread Some Infectious Diseases; Phage May Be New Therapeutic Target

Date:
May 26, 2003
Source:
Rockefeller University
Summary:
Until now, scientists thought that disease-causing bacteria left on the toy was the culprit in transferring the disease from the first child to the second. New research at The Rockefeller University shows that the culprit sometimes might not be the bacteria but a virus that infects and destroys the bacteria.

A strep-infected child in a daycare center plays with a toy, puts it in her mouth and crawls away. Another child plays with the same toy and comes down with strep. Until now, scientists thought that disease-causing bacteria left on the toy was the culprit in transferring the disease from the first child to the second. New research at The Rockefeller University shows that the culprit sometimes might not be the bacteria but a virus that infects and destroys the bacteria. Called a bacteriophage, this "bacteria-eating" virus causes disease by transferring toxins and other disease-causing genes between bacteria.

The findings, reported in the July issue of Infection and Immunity, show for the first time that bacteriophage, or phage -- previously thought not to be infectious to humans -- may be a new target for fighting certain bacteria that produce toxins.

"Controlling the phage may be as important as controlling the bacteria," says senior author Vincent A. Fischetti, Ph.D., professor and head of the Laboratory of Bacterial Pathogenesis and Immunology at Rockefeller.

"It's possible that phage present in the saliva of a child or another individual can cause the conversion of an existing non-toxigenic organism to a toxigenic one," adds Fischetti. "We always believed that phage were not infectious to humans, but in a sense, they are."

Scientists classify certain bacteria such as those causing scarlet fever, diphtheria and E. coli O157 (a source of food poisoning in contaminated meats) as toxigenic, meaning that these microbes produce toxins -- transported by phage -- that cause disease.

People can carry colonies of bacteria, such as strep, without being sick if the microbe doesn't carry a toxin-encoded phage. But, when a toxin-producing phage moves to a nonvirulent bacterium, it carries with it a toxin gene that is part of the phage genome, and transfers that gene to the new organism. This process, called lysogenic conversion, transforms the harmless microbe into a virulent bug.

Scientists were not sure where the bacteria picked up the phage, until two years ago when Thomas Broudy, Ph.D., then a graduate student in Fischetti's lab, identified a factor in human saliva that is secreted from cells in the pharynx -- the part of the alimentary canal between the cavity of the mouth and the esophagus -- and causes the phage to become active and burst out of the bacterium.

"Since phage and the bacterium are out in the environment, it was thought that the microbe picked up the phage there," says Fischetti. "We now know that phage are designed to do this in humans, and not in the environment, by taking advantage of a human factor called SPIF to allow the transfer process to occur efficiently."

In the lab, Broudy added SPIF (soluble phage inducing factor) to lysogenic bacteria. SPIF mobilized the phage and the bacteria disentegrated, or lysed. Because the bacterium he was studying, Group A strep, is only found in the human throat, Broudy deduced that the phage was induced or activated there, and not in the environment.

"It makes sense that the phage would want to induce at a site where it would potentially find its host," says Broudy. "The system is designed so that when a phage-carrying strep goes into the oral cavity, the phage induces, where it is released to infect any non-toxigenic bacteria that can potentially be there, transferring the phage -- and the toxin gene it carries -- to other bacteria."

So then the question was, can a non-toxigenic organism that is found in the oral cavity become toxigenic if you add a bacterium that is carrying a toxin-encoded phage?

To answer this question, Broudy, first author of the new Infection and Immunity paper, and Fischetti took human pharyngeal cells cultured in a petri dish and added toxigenic and non-toxigenic strains of Group A strep. They found that the phage "jumped" from the toxigenic strain, causing the bacterial strain that was not carrying the phage to produce toxins. The Rockefeller researchers repeated the experiment in the throat of a mouse and obtained the same results.

Broudy also isolated a toxin-carrying phage and introduced it to a mouse carrying a colony of non-infectious strep bacteria. The result: the non-infectious bacteria became toxigenic.

This research was supported by the National Institute of Allergy and Infectious Diseases, part of the federal government's National Institutes of Health.


Story Source:

The above story is based on materials provided by Rockefeller University. Note: Materials may be edited for content and length.


Cite This Page:

Rockefeller University. "'Bacteria-eating' Viruses May Spread Some Infectious Diseases; Phage May Be New Therapeutic Target." ScienceDaily. ScienceDaily, 26 May 2003. <www.sciencedaily.com/releases/2003/05/030526103831.htm>.
Rockefeller University. (2003, May 26). 'Bacteria-eating' Viruses May Spread Some Infectious Diseases; Phage May Be New Therapeutic Target. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2003/05/030526103831.htm
Rockefeller University. "'Bacteria-eating' Viruses May Spread Some Infectious Diseases; Phage May Be New Therapeutic Target." ScienceDaily. www.sciencedaily.com/releases/2003/05/030526103831.htm (accessed July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins