Introduction Early etiologic diagnosis can help for effective treatment of PCAP as well as for elaboration of guidelines of empirical antibioticotherapy of PCAP.

Objectives The aim of the study was to detect the etiological viral and bacterial agents in children with X-ray confirmed alveolar PCAP.

Material and methods From May 2011 until December 2012 we prospectively enrolled 118 children with a diagnosis of X-ray confirmed alveolar PCAP admitted to hospital. Sputum cultures were taken for microbiology. Respiratory secretion samples also were analysed by multiplex real time PCR (Seeplex RT-PCR Magicplex; Seegene, Korea) for 9 viruses and 6 bacteria. A real-time PCR assay was used to identify the rhinovirus in the enterovirus / rhinovirus positive samples. Children were divided into two groups: 3 months – 4 years (1st) and 5–17 years (2nd).

Results 104 children (88.1%.) were positive for at least one virus: the most frequently detected was adenovirus (33.9%.). Rhinoviruses were significantly more frequently detected in 1st group (p < 0.05). Viral co-infections with 2–7 viruses were found in 47 children (39.8%). S.pneumoniae and H.influenzae were detected using PCR more often than in microbiological cultures in 1st group. Correlation was found between adenovirus and S.pneumoniae in 1st group (p = 0.012) and between HMPV, rhinoviruses and S.pneumoniae in 2nd group (p = 0.01 and p = 0.021 respectively).

Conclusions The results of the study confirmed high incidence of viral-bacterial as well as viral-viral infection in alveolar PCAP. It was found virus specific co-infection in pneumococcal PCAP in preschool and school age children.