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Nasal passage bacteria may help prevent pneumonia, ear infections
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Corynebacterium accolens, a benign lipid-requiring bacterium, hydrolyzes skin surface triacylglycerols, releasing free fatty acids that inhibit pneumococcal growth, and may play a beneficial role in forming the human microbiome, according to a study published in MBio.
“We and others have hypothesized that pneumococcal interactions with commensal bacteria impact the ability of pneumococcus to colonize, proliferate, and persist,” Lindsey Bomar, PhD, postdoctoral fellow at the Forsyth Institute department of microbiology, in Cambridge, Massachusetts, and colleagues wrote. “If so, then defining pediatric nasal microbiota in the presence and absence of pneumococcal colonization might reveal potential clinically relevant interactions that affect pneumococcal colonization dynamics. For example, Pettigrew and colleagues observed that children free of nostril pneumococcal colonization had a greater relative abundance of Corynebacterium spp. than did children with pneumococcal colonization.
“Although non-diphtheriae Corynebacterium spp., along with pneumococcus, commonly colonize the skin and nasal passages, their function(s) in these complex microbial communities is poorly understood.”
To test their hypothesis that free fatty acids from human triacylglycerols are a mechanism by which C. accolens inhibits pneumococcal growth, the researchers analyzed a randomly selected subset of approximately 200 of the 1,000 nasopharyngeal swabs collected from October 2008 to April 2009 as part of a previous study of pneumococcal colonization. The swabs were taken from children aged 6 months to 7 years.
The researchers performed 16S rRNA gene sequencing on a subset of 45 samples. Data were analyzed using discriminant analysis effect size to compare the microbiota composition of children with and without Streptococcus pneumoniae.
According to the researchers, Corynebacterium spp. are overrepresented in children without S. pneumoniae. C. accolens inhibits pneumococcal growth during in vitro co-cultivation on medium supplemented with human skin surface triacylglycerols, which are likely present in the nostrils. This depends on LipS1, a triacylglycerol lipase required for C. accolens growth on triacylglycerols such as triolein. The researchers determined that C. accolens hydrolysis of triolein releases oleic acid, which acts against pneumococcus, as do other free fatty acids that may be released by LipS1 from these triacylglycerols.
“To our knowledge, this work provides the first evidence that C. accolens, a commensal Corynebacterium species that colonizes the nose, can inhibit S. pneumoniae,” Bomar and colleagues wrote. “The goal of identifying antagonistic interactions between commensal nasal bacteria and S. pneumoniae is to lay the foundation for future translational research aimed at preventing pneumococcal colonization and subsequent infection.” – by Jason Laday
Reference:
Laufer AS, et al. mBio. 2011;doi:10.1128/mBio.00245-10.
Disclosure: Bomar reports receiving funding from the National Institute of Dental and Craniofacial Research. See the full study for a list of all other authors’ relevant financial disclosures.
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