Abstract: Objective To understand the pathogenic evolution of throat swab specimens of kindergarten children suffering from acute upper respiratory tract infections (AURTIs) for the first time.Methods Kindergarten was taken as the place of a cohort study and the subjects were pre-school children who were enrolled in a kindergarten for the first time. The kindergarten life was taken as the exposure factor. During the physical examination before the enrollment and the first onset of AURTIs after 48 hours of enrollment and at the end of the first semester (pre-school children without AURTIs), nasopharyngeal secretions were collected by throat swabs, and bacteria culture was done and tests were carried out for respiratory syncytial virus (RSV), adenovirus (ADV), influenza virus A (Iva), influenza virus B(Ivb), parainfluenza virus Ⅰ (PIV Ⅰ), parainfluenza virus Ⅱ (PIV Ⅱ), parainfluenza virus Ⅲ (PIV Ⅲ), Mycoplasma pneumoniae and Chlamydia.Results Nine kinds of bacteria were found in 114 of 115 cases with an average age of 3.4 years. One case had (3.3±0.8) kinds of bacteria on average and there was one mycoplasma-positive (1.1%) case. During the semester 91 cases (79.1%) had AURTIs, for the first time the second to sixth onset of AURTIs were 63, 29, 16, 6, and 2 cases respectively and twelve cases developed to lower respiratory tract infection and 1 case to sepsis. Twelve kinds of virus were found after the culture of throat swab specimens of 115 preschool children collected at the time of enrollment. Compared with the time of enrollment, at the first onset of AURTIs there was an increase in the number of Streptococcus pneumoniae, Haemophilus influenzae, Streptococcus hemolyticus, Escherichia coli and Streptococcus pyogenes which were identified ≥3+ increased. There were 25 cases of (27.5%) mycoplasma and virus including 14 cases of mycoplasma, 5 cases of Iva, 2 cases of PIV Ⅰ, Ivb and ADV. AURTIs did not occur in 24 preschool children during the semester. A total of 9 kinds of bacteria were cultured at the time of enrollment, with an average of 3.5±0.7 in each case. At the end of the semester, 9 kinds of bacteria were cultured, with an average of 3.6±0.5 in each case. Compared with the time of enrollment, there was one more case of Streptococcus pyogenes which were identified ≥3+. No mycoplasma, chlamydia and virus were detected. For 115 cases of healthy pre-school children at the time of enrollment and 24 cases without AURTIs during the semester, bacteria colonization included Neisseria, Streptococcus viridans, Micrococcus, Gram-positive bacilli, Coagulase-negative Staphylococcus, Streptococcus pneumoniae, Influenza Haemophilus, Staphylococcus aureus, Enterobacter cloacae and Streptococcus pyogenes.Conclusion Senventy-nine percent of healthy pre-school children have AURTIs after enrollment, mostly infected by bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Streptococcus hemolyticus, Escherichia coli and Streptococcus pyogenes), Mycoplasma and viruses (Iva, PIV Ⅰ , Ivb, ADV) .

Key words: Bacterial, Nasopharyngeal pathogen, Preschool children, Upper respiratory infection, Virus