Featured Research

from universities, journals, and other organizations

How bacteria keep ahead of vaccines and antibiotics

Date:
January 28, 2011
Source:
Wellcome Trust Sanger Institute
Summary:
A new study has used DNA sequencing to provide the first detailed genetic picture of an evolutionary war between Streptococcus pneumoniae bacteria and the vaccines and antibiotics used against it over recent decades. By looking at the genomes of 240 samples, the scientists could precisely describe the recent evolution and success of a drug-resistant lineage of the bacteria. They suggests that their technique could improve infection control measures against bacterial diseases in the future.

Global phylogeny of PMEN1. The maximum likelihood tree, constructed using substitutions outside of recombination events, is coloured according to location, as reconstructed through the phylogeny using parsimony. Shaded boxes and dashed lines indicate isolates that have switched capsule type from the ancestral 23F serotype. Specific clades referred to in the text are marked on the tree: 'A' (South Africa), 'I' (International), 'V' (Vietnam), 'S' (Spain 19A) and 'U' (USA 19A).
Credit: Image courtesy of Wellcome Trust Sanger Institute

New research provides the first detailed genetic picture of an evolutionary war between Streptococcus pneumoniae bacteria and the vaccines and antibiotics used against it over recent decades. Large-scale genome sequencing reveals patterns of adaptation and the spread of a drug-resistant lineage of the S. pneumoniae bacteria.

Related Articles


The study unmasks the genetic events by which bacteria such as S. pneumoniae respond rapidly to new antibiotics and vaccines. The team suggest that knowing the enemy better could improve infection control measures.

S. pneumoniae is responsible for a broad range of human diseases, including pneumonia, ear infection and bacterial meningitis. Since the 1970s, some forms of the bacteria have gained resistance to many of the antibiotics traditionally used to treat the disease. In 2000 S. pneumoniae was responsible for 15 million cases of invasive disease across the globe. A new vaccine was introduced to the US in 2000 in an attempt to control disease resulting from the most common and drug resistant forms of the bacteria.

The new research uses DNA sequencing to precisely describe the recent evolution and success of a drug-resistant lineage of the bacteria called PMEN1 that has spread successfully to all continents.

"Drug resistant forms of S. pneumoniae first came onto the radar in the 1970s," says Dr Stephen Bentley, from the Wellcome Trust Sanger Institute and senior author on the study. "We sequenced 240 samples collected over the course of 24 years from the PMEN1 lineage of S. pneumoniae. By comparing the sequences, we can begin to understand how this bacterium evolves and reinvents itself genetically in response to human interventions."

The power of next-generation sequencing exposes S. pneumoniae as a pathogen that evolves and reinvents itself with remarkable speed. The degree of diversity was a real surprise in such seemingly closely related organisms.

First, the team had to distinguish between single letter mutations that are passed down 'vertically' when cells divide in two, and so-called 'horizontal' changes -- called recombinations -- where chunks of DNA letters are passed across from one bacterium to another and swapped over, changing the structure of their genomes.

"Separating these two kinds of change was the critical first step in unlocking the evolutionary history of the PMEN1 lineage," says Professor Julian Parkhill, Head of Pathogen Genomics at the Wellcome Trust Sanger Institute. "By looking only at the DNA mutations that are passed down through direct ancestry, we constructed an evolutionary tree. When we looked at our tree, we could see that the drug-resistant PMEN1 lineage originated around 1970 -- about the time that saw the introduction of the widespread use of antibiotics to fight pneumococcal disease."

The team also use their tree to trace the origin of PMEN1 to Europe, and suggest that the lineage may have been introduced to the Americas and Asia on multiple occasions.

The 'vertical' mutations, however, could not fully account for the evolution and adaptability of this pathogen.

The team found that the 'horizontal' transfer of DNA had affected three-quarters of the S. pneumoniae genome. The team also found hotspots -- areas of the genome that are particularly affected by horizontal transmission.

"We found that genes for antigens -- the molecules that trigger our immune response -- were particularly prone to this kind of change," says Dr William Hanage, Associate Professor of Epidemiology at Harvard School of Public Health, and a Visiting Reader at Imperial College London, where he devised the study with scientists at the Wellcome Trust Sanger Institute. "The remarkable amount of variation at these hotspots hints at ways S. pneumoniae can evade vaccines against these antigens.

"If the immune system targets these antigens, then the bacteria can simply change them, like a criminal changing their appearance to evade detection."

The authors also identify differences in the patterns of adaptation in response to antibiotics and vaccines.

"With antibiotics, different strains quite often adapt in the same way to become resistant," says Nicholas Croucher, from the Wellcome Trust Sanger Institute and first author on the paper. "With vaccines, it is quite different. What we see is a decline in the prevalence of bacteria that are susceptible to the vaccine. This, in turn, opens the door for bacteria that can evade the vaccine to fill the niche and become the dominant strain."

While the latest vaccination measures in the USA have almost completely removed the target pneumococcal strains from the population, the pathogen has deep resources to draw on in response. The research suggests that variants that allowed some bacteria to escape the new vaccine were present before the vaccine was introduced. These variants then flourished, expanding to fill a 'gap in the market' as the grip of the dominant strain was weakened through vaccination.

The researchers suggest that the study provides important new clues into the genetic adaptability of bacteria like S. pneumoniae. They suggest that further focused sequencing programs may prove crucial to the future control of this, and other, bacterial pathogens that use similar mechanisms to outsmart human control measures.


Story Source:

The above story is based on materials provided by Wellcome Trust Sanger Institute. Note: Materials may be edited for content and length.


Journal Reference:

  1. N. J. Croucher, S. R. Harris, C. Fraser, M. A. Quail, J. Burton, M. van der Linden, L. McGee, A. von Gottberg, J. H. Song, K. S. Ko, B. Pichon, S. Baker, C. M. Parry, L. M. Lambertsen, D. Shahinas, D. R. Pillai, T. J. Mitchell, G. Dougan, A. Tomasz, K. P. Klugman, J. Parkhill, W. P. Hanage, S. D. Bentley. Rapid Pneumococcal Evolution in Response to Clinical Interventions. Science, 2011; 331 (6016): 430 DOI: 10.1126/science.1198545

Cite This Page:

Wellcome Trust Sanger Institute. "How bacteria keep ahead of vaccines and antibiotics." ScienceDaily. ScienceDaily, 28 January 2011. <www.sciencedaily.com/releases/2011/01/110127141655.htm>.
Wellcome Trust Sanger Institute. (2011, January 28). How bacteria keep ahead of vaccines and antibiotics. ScienceDaily. Retrieved October 30, 2014 from www.sciencedaily.com/releases/2011/01/110127141655.htm
Wellcome Trust Sanger Institute. "How bacteria keep ahead of vaccines and antibiotics." ScienceDaily. www.sciencedaily.com/releases/2011/01/110127141655.htm (accessed October 30, 2014).

Share This



More Plants & Animals News

Thursday, October 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Galapagos Tortoises Bounce Back, But Ecosystem Lags

Galapagos Tortoises Bounce Back, But Ecosystem Lags

Newsy (Oct. 29, 2014) The Galapagos tortoise has made a stupendous recovery from the brink of extinction to a population of more than 1,000. But it still faces threats. Video provided by Newsy
Powered by NewsLook.com
Obama: The US Will Not 'run and Hide' From Ebola

Obama: The US Will Not 'run and Hide' From Ebola

AP (Oct. 29, 2014) Surrounded by health care workers in the White House East Room, President Barack Obama said the U.S. will likely see additional Ebola cases in the weeks ahead. But he said the nation can't seal itself off in the fight against the disease. (Oct. 29) Video provided by AP
Powered by NewsLook.com
Oatmeal Healthy Recipes and Benefits

Oatmeal Healthy Recipes and Benefits

Buzz60 (Oct. 29, 2014) Oatmeal is a fantastic way to start your day. Whichever way you prepare them, oats provide your body with many health benefits. In celebration of National Oatmeal Day, Krystin Goodwin (@krystingoodwin) has a few recipe ideas, and tips on how to kickstart your day with this wholesome snack! Video provided by Buzz60
Powered by NewsLook.com
GoPro Video Gives a Lion's-Eye View of The Hunt

GoPro Video Gives a Lion's-Eye View of The Hunt

Buzz60 (Oct. 29, 2014) If you’ve ever wondered what getting takeout looks like for lions in Africa, the GoPro video from Lion Whisperer Kevin Richardson will give you a lion’s-eye view of the hunt. Jen Markham has more. Video provided by Buzz60
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:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

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