[Detection of human metapneumovirus prevalence in pediatric patients with lower respiratory tract infections].

Human metapneumovirus (hMPV) which is classified in Paramyxoviridae family has been identified in 2001 as the etiological agent of lower respiratory tract infection (LRTI) especially in children. Previous studies indicated that hMPV prevalence in LRTI is between 2-25%, being responsible for 10% of childhood LRTIs and its isolation rate is approximately 6% in hospitalized patients under age three years. The aim of this study was to investigate the hMPV prevalence in children with LRTI in our region. A total of 100 patients (41 female, 59 male) ages between 0-10 years old (median age: 4.8) and who were admitted to Pediatric Clinics of Ege University Medical Faculty Hospital with the diagnosis of LRTI between January-December 2009 were included in the study. Nasopharyngeal swab samples were taken from those patients during the first three days of their symptoms. The presence of hMPV in the samples were investigated by rapid (shell vial) cell culture method using HEp-2 cell line and by real-time reverse transcriptase polymerase chain reaction (rRT-PCR). The methods were performed to the clinical samples simultaneously. In both methods, a standard strain of hMPV provided by Erasmus University was used as positive control and QCMD-2009 hMPV panel was used as external quality control. In our study, 11 and 2 samples were found positive with cell culture and rRT-PCR methods, respectively. Two of rRT-PCR positive samples were also positive in cell culture, while the other nine were positive by only cell culture method. Both of the methods were performed twice due to inconsistent results, however, the same results were obtained in both runs. Studies with QCMD-2009 panel yielded compatible results for five samples, however a positive standard sample (hMPV A subtype, Ct value: 37.31) was found as negative by rRT-PCR test used in this study (RealAccurateTM, Pathofinder, The Netherlands). Our data showed that the prevalence of hMPV detected by rapid cell culture method was 11% in pediatric patients with LRTIs, the age range of hMPV positive cases was 6 months to 7 years old (median age: 20 months), the majority of the admissions was in winter season and the main clinical picture was bronchiolitis. In addition, rRT-PCR assay used in this study was thought to be insufficient to detect the viral RNA in the event of low levels of hMPV A subtypes. Thereby the cell culture method should be used in addition to the new developing molecular methods for the detection of hMPV until standardization is achieved.