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19-05-2013 | Infectious disease | Article

Molecular testing steps up to the plate in pneumonia


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medwireNews: Anaerobes and oral bacteria are more frequently found in patients with community-acquired pneumonia (CAP) than previously thought, say Japanese researchers.

In the past, the pathogens were thought to be responsible for only a small proportion of cases but, using a molecular method to analyze bronchoalveolar lavage (BAL) fluid, the study authors found that in fact, they were the cause of around a third.

The researchers say the finding could help speed up the diagnosis and treatment of CAP, in which the causative bacterial pathogens currently go unidentified in up to half of cases.

"In contrast to the former reports using cultivation methods, this molecular method could detect bacterial phylotypes in all CAP patients," say Hiroshi Mukae (University of Occupational and Environmental Health, Kitakyushu, Fukuoka) and colleagues.

The study included 64 patients admitted to hospital with CAP between April 2010 and December 2011.

Using sputum cultivation, the authors could only identify bacteria in 50% of the patients, they report in PLoS One.

Meanwhile, conventional cultivation of BAL samples found the most commonly detected pathogen was Streptococcus pneumoniae (18.8%), followed by Mycoplasma pneumoniae (17.2%), Haemophilus influenzae (14.1%), and Moraxella catarrhalis (7.8%).

Using a cultivation-independent molecular method to analyze the same samples, the authors found that the prevalence of these pathogens was comparable at 18.8%, 17.2%, 18.8%, and 9.4%, respectively. However, they also detected oral streptococci in 9.4% of samples, the oral bacteria species Neisseria in 4.7%, and anaerobes (Prevotella spp, Fusobacterium spp, Veillonella spp, and Clostridium sp) in 15.6%.

Molecular analysis identified anaerobes in eight of the 12 patients for whom conventional techniques detected no pathogenic organisms or antigens, the authors note.

"These results suggest that resident oral streptococci and anaerobes might be the primary bacteria responsible for the unknown causative pathogens of CAP in the previous reports," suggest Mukae and colleagues.

The research also found that M. pneumoniae (24.4%) is the dominant species in mild cases of pneumonia, followed by H. influenzae (20.0%), and anaerobes (17.7%), while S. pneumoniae (36.4%), oral streptococci (27.3%), and M. catarrhalis (18.2%) were most commonly detected in severe cases.

Physicians should more frequently consider anaerobes and oral bacteria as pathogens in CAP patients, particularly those with mild pneumonia severity, the authors conclude.

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Kirsty Oswald, medwireNews Reporter