First, to identify the relationship between age and sex, this study analyzed the sex and age data of 679 pediatric patients with severe CAP. The results showed that among all severe CAP cases, there were 64.80% (440/679) males and 35.20% (239/679) females. The patients with severe CAP ≤1 year old were 266, comprising 173 (65.04%) males and 93 (34.96%) females; and there were 413 patients with severe CAP >1 year old, comprising 267 (64.65%) males and 146 (35.35%) females. No significant difference in sex was found in the children with severe CAP between the two age groups (χ2 = 0.011, P = 0.918).
Second, to identify the relationship between the etiology and sex, this study divided all cases into positive and negative groups according to the results of pathogen detection to compare the two sexes. The results showed that the number of male cases was higher than that of female cases regardless of the presence or absence of pathogen infection. Among them, the patients with positive bacterial, viral, MP, CP, and fungal infections accounted for 30.04%, 25.92%, 32.55%, 5.74%, and 7.95%, of the total cases, respectively. Further analysis showed that MP infection was significantly associated with the patient’s sex (χ2 = 5.939, P <0.05), whereas bacterial, viral, CP, and fungal infections had no significant association with the patient’s sex (χ2 = 0.445, 0.824, 0.009, and 0.350, respectively, all P >0.05, Table 1).
A previous study has shown that age significantly affected the incidence of severe CAP in children.(10) To investigate the relationship between age and pathogen infection in severe CAP, this study divided all cases into ≤1-year-old and >1-year-old groups, which were then compared for the presence of pathogen infection. The results showed that the bacterial, viral, MP, and CP infections were significantly associated with patient’s age using 1-year-old as the age boundary (χ2 = 8.581, 6.263, 117.403, and 5.158, respectively, P <0.05). Compared with the opposite age group, patients ≤1-year-old had a higher positive rate of CP infection, while patients >1-year-old had a higher positive rate of bacterial, viral, and MP infections. However, no significant correlation was found between the fungal infection and age (χ2 = 0.684, P = 0.408, Table 2).
To further analyze the etiology of children with severe CAP, this study analyzed the infectious pathogens in these patients, and specifically focused on the top three pathogenic bacteria and respiratory viruses. The results showed that the top three bacteria in the culture were Haemophilus influenza (n = 57 cases of infection), Streptococcus pneumoniae (n = 50 cases of infection), and Pseudomonas aeruginosa (n = 25 cases of infection). The top three viruses detected were ADV (n = 124 cases of infection), RSV (n = 24 cases of infection), and parainfluenza virus (n = 21 cases of infection). Importantly, the case numbers of ADV and MP infections were 124 (18.26%) and 221 (32.55%), respectively, which were significantly higher than other single pathogen infections (Figure 1).
The above results showed that the numbers of severe CAP cases caused by ADV or MP infection were much higher than those of the other pathogen infections. Clinically, the proportion of viral infection-induced CAP was the highest.(7, 11) Therefore, we further focused on studying the correlation between ADV infection and other pathogen infections. The results showed that ADV infection was significantly associated with MP infection (χ2 = 44.991, P = 0.000), but not significantly associated with bacterial, CP, and fungal infection in the severe CAP (χ2 = 0.026, 3.097, and 2.308, respectively, P >0.05, Table 3).
Lastly, to further analyze the risk factors of severe ADV-infected pneumonia, we used ADV infection as an independent variable and patient’s age, sex, bacteria, MP, CP, and fungi as covariates to evaluate the effects of these factors on ADV infection. The logistic regression analysis showed that MP-positive infection was a risk factor for ADV infection (OR = 0.279, P = 0.000), while no significant correlation was found between the ADV infection and other factors, including patient’s sex, age, bacteria, CP, and fungi (OR = 0.809, 1.416, 0.834, 3.070, and 0.570, respectively, P >0.05). To further verify the correlation of ADV and MP co-infection, we used MP infection as an independent variable and patient’s sex, age, bacteria, fungi, CP, and ADV as covariates to identify the risk factors affecting MP infection. The results showed that the patient’s sex, age, and bacterial, CP, and ADV infections were risk factors for MP infection (OR = 1.712, 10.313, 1.678, 0.332, and 0.277, respectively, P <0.05), whereas no significant correlation was found between MP infection and fungal infection (OR = 1.207, P >0.05, Tables 4 and 5).