medwireNews: A study of children shows that Mycoplasma pneumoniae is commonly carried in the respiratory tract without causing symptoms.
Furthermore, the researchers found that current diagnostic tests could not distinguish between asymptomatic carriage and symptomatic infection, raising doubts over the clinical significance of a positive test result.
"A diagnosis of M. pneumoniae-induced [respiratory tract disease] cannot be based exclusively on serology or the detection of M. pneumoniae DNA in the upper respiratory tract [URT], and caution should be taken in the interpretation of diagnostic tests for M. pneumoniae," say Emiel Spuesens (Erasmus MC-Sophia, Rotterdam, the Netherlands) and colleagues.
Between July 2008 and November 2011, the researchers recruited 405 asymptomatic children who were admitted to hospital for nonrespiratory causes, and 321 symptomatic children who had been diagnosed with respiratory tract infection (RTI).
In pharyngeal and nasopharyngeal specimens, rates of M. pneumoniae by real-time polymerase chain reaction (PCR) were comparable at 21.2% in the asymptomatic group and 16.2% in the symptomatic group, as were rates by culture at 1.0% and 1.6%, respectively.
Additionally, real-time PCR was unable to differentiate between upper RTI and lower RTI in symptomatic children.
And, serum testing for anti-M.pneumoniae antibodies also failed to demonstrate significant differences in positivity between the groups, after controlling for age.
The authors note significant variation in PCR-detected rates of M. pneumoniae in asymptomatic children according to season and year of enrollment, such that prevalence was 3% in the spring of 2009 and 58% in the summer of 2010.
"For now we can conclude that M. pneumoniae carriage is detectable and its prevalence is higher than expected, but the actual prevalence of carriage is unreliable," they comment.
Writing in PLoS One, the authors say that their findings could have major implications for the clinical diagnosis of symptomatic M. pneumoniae infection, particularly in light of the bacterium's increasing resistance to treatment.
"Our data indicate that the etiology of RTI in children is complex," say Spuesens and team. "The mere presence of one or more putative pathogens in the URT does not seem to be the sole determining factor in the development of a symptomatic RTI."
They conclude: "Future studies will therefore have to focus on how and RTI can be accurately defined and whether or not it requires treatment."
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