This study was a retrospective, observational study conducted at Shenzhen Children’s Hospital, a 1300-bed tertiary care facility in Shenzhen, China. The study population consisted of children hospitalized from January 2017 to December 2019 with positive B. pertussis polymerase chain reaction (PCR) and/or culture tests. Patients with a negative RSV PCR test and negative immunofluorescence assay of 7 respiratory viruses were included in the pertussis group. Patients who met both of the following criteria were included in the RSV coinfection group: a positive RSV test using PCR or immunofluorescence assay; and a negative immunofluorescence assay of the other 6 respiratory viruses except for RSV. Patients who met one of the following criteria were excluded: newborns; infection of HIV; leukemia; known or suspected active tuberculosis; receiving immunosuppressive agents; immunodeficiency; and chronic conditions (malnutrition, congenital heart disease, or chronic lung disease).
Data Collection And Management
Demographic information (age, sex, preterm birth history, and vaccination status), symptoms and signs (cough, inspiratory whooping, cyanosis, and auscultation of the chest), laboratory results (hematology and pathogen tests), chest image results (chest x-ray and/or computed tomography), antibiotic treatment, hospitalization information (readmission due to relapse and length of hospital stay), and outcome (survival, death, recovery or discharged against medical advice) were recorded.
This study was approved by the ethics committee of Shenzhen Children’s Hospital, and written informed consent was obtained from patients’ guardians.
Two nasopharyngeal samples and two oropharyngeal samples were obtained per patient. All of the respiratory tract samples were transported to the laboratory within 4 hours.
Bordetella pertussis detection by culture and PCR
Nasopharyngeal swab samples were used for B. pertussis culture and PCR. Samples were cultured on charcoal agar plates (OXOID, United Kingdom) supplemented with 10% defibrinated sheep blood and cephalexin. The plates were incubated in a humidified incubator at 37 °C for up to 7 days and inspected daily. Real-time PCR was performed using “Bordetella pertussis real-time fluorescence PCR detection kit” (DaAn Gene Co. Ltd., Guangzhou, China), following the manufacturer's instructions.
Respiratory Virus Detection
Oropharyngeal swab samples were tested for respiratory viruses. Immunofluorescence assay of 7 respiratory viruses (influenza A, influenza B, RSV, adenovirus, parainfluenza 1, parainfluenza 2, and parainfluenza 3 viruses) was performed using “D3® UltraTM DFA Respiratory Virus Screening and ID Kit” (Diagnostic Hybrids, Inc. USA). RSV Real-time PCR was performed using “the respiratory syncytial virus real-time fluorescence PCR detection kit” (DaAn Gene Co. Ltd., Guangzhou, China), following the manufacturer's instructions.
We did a univariate correlation analysis of clinical variables to determine significant differences in clinical characteristics between the 2 groups. Mann-Whitney test and chi-square test were used for quantitative and qualitative variables, respectively. Continuous variables were summarized as mean (standard deviation) when they were normally distributed and as median (interquartile range, IQR) if they had a skewed distribution. Data analysis was performed by SPSS 26.0 software. All P-values were two-tailed, and P < 0.05 was considered to indicate statistical significance.