Bacterial respiratory tract colonization prior to catching the flu may protect against severe illness

July 10, 2014
Bacterial respiratory tract colonization prior to catching the flu may protect against severe illness
Jan Erikson, Ph.D.

Many studies have shown that more severe illness and even death are likely to result if you develop a secondary respiratory infection after developing influenza. Now, however, a team of researchers based at The Wistar Institute has determined that if you reverse the order of infection, the bacteria Streptococcus pneumoniae (often called pneumococcus) may actually protect against a bad case of the flu.

The researchers discovered that the bacterial protein pneumolysin, which is described as a bacterial virulence factor, might protect macrophages—a type of immune system cell—in the lungs. Their findings, performed in a mouse model of influenza , appear in the August issue of the journal Virology, available online now.

"Influenza remains a major killer, and there is a preponderance of evidence, both scientific and historical, to show how secondary bacterial infections can be fatal," said Jan Erikson, Ph.D., professor at The Wistar Institute. "However, pneumococci often colonize the asymptomatically, particularly in children, leading us to consider how pre-colonization would impact a subsequent influenza infection."

"Our studies showed that prior colonization offered a against severe disease in mice," Erikson said, "and we were able to point to the bacterial virulence factor pneumolysin in mediating this protection."

In their investigations, Erikson and her colleagues found that mice who were colonized by Streptococcus pneumonia ten days prior to exposure to were significantly less likely to develop severe disease or pneumonia than mice who were not colonized by the bacteria. In contrast, disease symptoms were exacerbated in mice that were exposed to the flu prior to a secondary pneumococcal infection.

"Mice that were first exposed to pneumococci exhibited less inflammation in the lungs following . Virus infection wasn't blocked but the response to it was changed such that the mice no longer showed signs of illness," Erikson said.

The researchers then went about investigating how this might occur. Using mutant strains of that lacked certain proteins, Erikson and her colleagues were able to single out one bacterial protein, pneumolysin, which was necessary to generate the protective effect of pneumococcus. While the exact mechanisms by which pneumolysin lessens the severity of disease remain unknown, Erikson and her colleagues were able to show how alveolar macrophages were less likely to recruit inflammation-causing immune cells to the lungs. Less inflammation would mean less chances of developing pneumonia, which is a major source of flu deaths, Erikson says.

According to Erikson, her results suggest that one factor contributing to the highly variable response to and severity of disease observed in humans is the presence of specific respiratory tract microbes. "It remains to be seen what lessons we can learn from pneumococcus in lessening flu infections," Erikson said, "but I would be interested in seeing if we could get the benefit of pneumococcal colonization without the associated risks."

Explore further: 2009 H1N1 pandemic flu more damaging to lungs, opens opportunities for bacterial infection

Related Stories

2009 H1N1 pandemic flu more damaging to lungs, opens opportunities for bacterial infection

September 19, 2011
Many of the people who died from the new strain of H1N1 influenza that broke out in 2009 were suffering from another infection as well: pneumonia. A new study to be published Tuesday, September 20 in the online journal mBio ...

Mechanism that prevents lethal bacteria from causing invasive disease revealed

July 7, 2014
An important development in understanding how the bacterium that causes pneumonia, meningitis and septicaemia remains harmlessly in the nose and throat has been discovered at the University of Liverpool's Institute of Infection ...

Flu helps spread pneumonia

April 11, 2011
Bacteria that cause pneumonia and meningitis are only able to spread when individuals are infected with flu, says a scientist reporting at the Society for General Microbiology's Spring Conference in Harrogate. The work could ...

Interleukin-22 protects against post-influenza bacterial superinfection

May 30, 2013
Researchers from the Pasteur Institute, Lille, France have shown in a mouse model that interleukin-22 protects against bacterial superinfections that can arise following influenza. Their research is published in the June ...

Influenza infection increases likelihood of bacterial pneumonia 100-fold

June 26, 2013
It's been known for more than two centuries that pneumonia cases increase during flu epidemics.

Study finds depletion of alveolar macrophages linked to bacterial super-infections

July 22, 2013
A recent study published in the July issue of the Journal of Immunology helps explain why some humans contract bacterial super-infections like pneumonia with influenza. The research was led by Le Bonheur Pediatrician-in-Chief ...

Recommended for you

Google searches can be used to track dengue in underdeveloped countries

July 20, 2017
An analytical tool that combines Google search data with government-provided clinical data can quickly and accurately track dengue fever in less-developed countries, according to new research published in PLOS Computational ...

MRSA emerged years before methicillin was even discovered

July 19, 2017
Methicillin resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published in the open access journal Genome Biology. It was ...

New test distinguishes Zika from similar viral infections

July 18, 2017
A new test is the best-to-date in differentiating Zika virus infections from infections caused by similar viruses. The antibody-based assay, developed by researchers at UC Berkeley and Humabs BioMed, a private biotechnology ...

'Superbugs' study reveals complex picture of E. coli bloodstream infections

July 18, 2017
The first large-scale genetic study of Escherichia coli (E. coli) cultured from patients with bloodstream infections in England showed that drug resistant 'superbugs' are not always out-competing other strains. Research by ...

Ebola virus can persist in monkeys that survived disease, even after symptoms disappear

July 17, 2017
Ebola virus infection can be detected in rhesus monkeys that survive the disease and no longer show symptoms, according to research published by Army scientists in today's online edition of the journal Nature Microbiology. ...

Mountain gorillas have herpes virus similar to that found in humans

July 13, 2017
Scientists from the University of California, Davis, have detected a herpes virus in wild mountain gorillas that is very similar to the Epstein-Barr virus in humans, according to a study published today in the journal Scientific ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.