Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




EPIDEMICS
MRSA strain in humans originally came from cattle
by Staff Writers
Washington DC (SPX) Aug 19, 2013


File image.

A strain of bacteria that causes skin and soft tissue infections in humans originally came from cattle, according to a study to be published in mBio, the online open-access journal of the American Society for Microbiology.

The researchers who conducted the genetic analysis of strains of Staphylococcus aureus known as CC97 say these strains developed resistance to methicillin after they crossed over into humans around forty years ago. Today, methicillin-resistant S. aureus (MRSA) strain CC97 is an emerging human pathogen in Europe, North and South America, Africa, and Asia. The findings highlight the potential for cows to serve as a reservoir for bacteria with the capacity for pandemic spread in humans.

The researchers sequenced the genomes of 43 different CC97 isolates from humans, cattle, and other animals, and plotted their genetic relationships in a phylogenetic tree. Corresponding author Ross Fitzgerald of the Roslin Institute and the University of Edinburgh in Scotland says strains of CC97 found in cows appear to be the ancestors of CC97 strains from humans.

"Bovine strains seemed to occupy deeper parts of the phylogenetic tree - they were closer to the root than the human strains. This led us to conclude that the strains infecting humans originated in cows and that they had evolved from bovine to human host jumps," says Fitzgerald.

Although the CC97 strains from animals were quite genetically diverse, the human isolates cluster together in two tight, distinct "clades", or relatedness groups, indicating that S. aureus CC97 in cattle crossed over into humans on two separate occasions. Using mutation rates as a molecular clock, the authors determined that the ancestor of clade A jumped from a bovine host to humans between 1894 and 1977 and clade B made the jump between 1938 and 1966.

After they made the jump, the human CC97 strains acquired some new capabilities, says Fitzgerald, thanks to genes encoded on portable pieces of DNA called mobile genetic elements.

"It seems like these elements, such as pathogenicity islands, phages, and plasmids, are important in order for the bacterium to adapt to different host species," says Fitzgerald. "The reverse is true as well: the bovine strains have their own mobile genetic elements."

Perhaps the most problematic new capability the human strains acquired is the ability to resist methicillin, an important antibiotic for fighting staphylococcal infections. Only human strains of CC97 were able to resist the drug, which indicates that the bacteria acquired resistance after they crossed over into humans, presumably through exposure to antibiotics prescribed for treating human infections.

This sequence of events contrasts with the case of a S. aureus strain from pigs, Fitzgerald points out, since a study in 2012 revealed that MRSA ST398 strains evolved the ability to resist methicillin before they crossed over into humans (http://mbio.asm.org/content/3/1/e00305-11).

Any number of factors could create these differences, making pigs - but not cattle - a source of a drug-resistant bacterium. At this point, though, there isn't enough information to say whether differences in the S. aureus strains, differences between pigs and cattle, or differences between swine and dairy farming practices might be responsible.

Moving forward, Fitzgerald says he and his colleagues plan to widen the investigation.

"We have a relatively small sample size, and the findings are robust, but we want to extend the study now to include a greater number of clones to get a bigger picture of what's going on across the S. aureus species," says Fitzgerald.

A wider variety of S. aureus strains, Fitzgerald says, from a wider variety of locations and hosts and a wider range of time, will allow them to better pinpoint the timing and circumstances of the host jump events. Understanding how and when MRSA has crossed over from other species in the past can help us to put the brakes on these crossovers in the future and hopefully prevent the birth of the next pandemic S. aureus strain.

.


Related Links
American Society for Microbiology
Epidemics on Earth - Bird Flu, HIV/AIDS, Ebola






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EPIDEMICS
New H7N9 bird flu death confirmed in China: hospital
Beijing (AFP) Aug 13, 2013
A Chinese woman infected with the deadly H7N9 bird flu virus died of multiple organ failure, a Beijing hospital said, bringing the total fatalities from the disease to 45. The 61-year-old tested positive for the virus on July 20 after she fell ill in Hebei province in northern China. She was taken to Beijing's Chaoyang Hospital for treatment and died on Sunday, the hospital said in a sta ... read more


EPIDEMICS
Protesters blast Russia's undocumented immigrants detention camps

Fukushima operator pumps out toxic groundwater

Legacy of 1986 Chernobyl disaster seen in impact on region's forests

Dark tourism brings light to disaster zones

EPIDEMICS
Scientists create light/heat regulating window coating

Bubbles are the new lenses for nanoscale light beams

New insights into the polymer mystique for conducting charges

Toxicologist says NAS panel 'misled the world' when adopting radiation exposure guidelines

EPIDEMICS
Tajik President Emomali Rahmon sees country's future in hydropower

Baby corals pass the acid test

Study finds novel worm community affecting methane release in ocean

Tahiti: A very hot biodiversity hot spot in the Pacific

EPIDEMICS
Chinese tycoon still hopes to sign Icelandic land deal

Ice ages only thanks to feedback

Greenland ice is melting - also from below

Greenpeace challenges Rosneft vessel in Arctic waters

EPIDEMICS
Highest winter losses in recent years for honey bees in Scotland

Nepal steps up poultry cull to combat bird flu

Fonterra executive resigns after milk scare

New Zealand PM to make milk scare apology in China

EPIDEMICS
Powerful quake jolts major New Zealand cities

More floods expected in Sudan after 53 die

Russian rescued after days lost on Indonesia volcano

Scientists plan to probe 'plumbing' of Mount St. Helens volcano

EPIDEMICS
China's Xi vows stepped up health cooperation with Africa: Xinhua

Keita wins by landslide in Mali presidential vote

Leader of 2012 military coup in Mali promoted

DR Congo colonel defects to M23 rebels with 30 men: army

EPIDEMICS
Research effort dates oldest known petroglyphs in North America

Study contradicts concept of 'left brain,' 'right-brain' personalities

Neandertals made the first specialized bone tools in Europe

Scientists have found new evidence to show how early humans migrated into Europe




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement