Spectrum of respiratory pathogens detected by multiplex PCR in a study of respiratory tract infections among travelers

Background: Respiratory tract infections (RTI) are a significant cause of health problems, accounting for about 10% of consultations in returning travelers. Nevertheless, the precise microbial etiology is not identified in many cases.

Methods: Prospectively collected 63 respiratory specimens(sputum or throat swab) from patients presented with respiratory symptoms(cough, sputum, chest pain, dyspnea, tachypnea, or abnormal findings of chest auscultation) after travel were tested using multiplex real-time PCR. The FTD Respiratory pathogens 33(Fast-track diagnostics, Ltd.) can simultaneously detect 33 different respiratory pathogens directly from respiratory specimens. This test ran in the PCR-Only mode on BD MAX™ (Nippon Becton Dickinson Company, Ltd.) and LightCycler480 System (Roche).

Results: 59 consecutive cases were included in the study. 39 cases were diagnosed as non-specific upper respiratory tract infections, 5 cases were influenza, bronchitis, pneumonia, 3 cases was acute sinusitis, and 1 case was acute pharyngitis, dengue fever. 24 cases had returned from travel in Southeast Asia, 9 from Africa, and 8 from Latin America, 7 from South Asia, 6 from middle east, 3 from North America, 3 from East Asia, 2 from Oceania, and 1 from Europe.
Of the 59 specimens analyzed, 48
(81.4%) tested positive for pathogens whereas 11 tested negative. Commonly detected pathogens were Haemophilus influenzae(14 cases; 23.7%), influenza A (10 cases; 17.0%), rhinovirus(9 cases; 15.2%), Staphylococcus aureus(8 cases; 13.6%), Moraxella catarrhalis(8 cases; 13.6%), Streptococcus pneumonia, coronaviruses OC43, and Mycoplasma pneumoniae(4 cases; 6.8%, respectively). Multiple pathogens were detected in 30.5% of the specimens. In 14 cases(23.7%), both virus and bacteria were detected from one specimen.

Conclusion: Not only viruses, bacterial pathogens were detected frequently than expected in the patients of RTI. Comprehensive molecular testing such as multiplex real-time PCR would change our understandings of epidemiology of RTI among travelers.