| BackgroundAcute respiratory tract infection (ARTI) is a group of diseases that respiratory system infection is the main clinical manifestation, there are many pathogens can be the cause of it, such as viruses, bacteria, mycoplasma and Chlamydia. ARTI can be devided into acute upper respiratory tract infection (AURI) and acute lower respiratory infections (ALRTI). ARTI is one of the most common human infectious diseases in world, the incidence of the disease is to lead a variety of infectious diseases.ARTI is a main threat to children’s health and killing about 2 million children each year, it has become the second cause of death in children under five years old, and also one of the major public health problems.Studies have reported that a preschool child can get respiratory infection 6-10 times a year on average, and about 3% of children under the age 1 are hospitalized with severe lower respiratory tract infections. Pneumonia is a common, frequently-occurring disease in infants and young children, there are about 156 million children with pneumonia each year, of which 151 million are in developing countries, it is the leading cause of death in children under 5 accounted for 19% of all deaths.About 90% of the acute respiratory tract infections caused by viruses, bacteria often infect the body after virus.The main bacterial pathogens are streptococcus pneumonia, haemophilus influenza, etc. But it’s hard to distinguish whether bacterial or viral pathogen infections through clinical symptoms, signs, or radioactive check, so using molecular biology method to determine the pathogen has become an important method to guide diagnosis and clinical medicine.A number of studies have confirmed that several pathogens are the cause of acute respiratory disease in children, but there may be a variety of respiratory pathogens infection at the same time, so it’s hard to explain the occurrence of respiratory disease is caused by a certain pathogens.Then the use of control is very important to improve the quality of the results of the study, more and more studies begin to adopt the method of case-control study to obtain more accurate results.ObjectThe study will collect the specimens all around a year, and analysis the distribution of the bacterial pathogens in gender, age and time;By comparing with the control to get the main bacterial pathogen of children under the age 5 of severe acute respiratory disease.MethodsThe study selected the children as cases who hospitalized with acute respiratory infection in the first people’s hospital of Chenzhou city of hunan province from July 2013 to June 2014, and the childern as controls who are in the hospital for a healthy examination or a operation at the same time, the ratio of the cases to controls is 2:1.The research collected nose swabs and pharyngeal swab specimens of the cases and controls at the same time.The specimens have been saved in -70℃ refrigerator immediately after collections. Q-PCR detections have been done after all specimens have been collected.The study has been detected 9 kinds of bacterial pathogens such as streptococcus pneumoniae, and Candida albicans, Chlamydia pneumonia and Mycoplasma pneumoniae.Resultsl.The study has collected 598 cases and 289 controls, while after screening according to the inclusion criteria and exclusion criteria there are 489 cases and 244 controls;2. In the 489 cases, there are 234 specimens (47.85%) detected in at least one kind of bacterial pathogens,200 of them are only a single pathogen infection (85.47%), while 34 of them are mixed infection (6.95%).In the control group, there are 65 specimens (26.64%) detected in at least one kind of pathogens,55 of them are only a single pathogen infection (84.62%), while 10 of them are mixed infection (15.38%).The difference between the case group and the control group is significant (X2=30.329, P <0.05);3. Eosinophilic lung legionella, s. pyogenes and candida albicans were not detected either in the case and the control group;Pseudomonas aeruginosa, b haemophilus influenzae and mycoplasma pneumoniae were not detected in the control group. Streptococcus pneumoniae is the pathogen most frequently be detected.while the positive rate in the case group is 32.72%; the followed pathogen is e. coli (8.38% of the cases) and chlamydia pneumonia (positive rate 8.18%), the rest of the pathogen detection rate is low;4. The detection rates of the pathogens in two gender group are no significant difference (P> 0.05), the detection rates of each pathogen in all age groups are no significant difference (P> 0.05).5. On time distribution, the highest rate of the case group appeared in August 2014, while the control group was the lowest (not detected);In February 2015 to April the detection rate of the two groups are very close; the total annual detection rates of the case group and control group have significant differences; which in January and July to November, the rates of the case group and control group are with significant difference, the rest of the month, there are no significant difference;6. Co-infection aspects in the 489 cases,421 of them have been detected at least one kind of pathogens (one virus or bacteria),the positive rate is 86.09%;And there are 34 of the bacterial pathogens infections(14.53%)have been detected two or more kinds of bacterias,the most of the mergers between bacterial pathogen infections is mainly streptococcus pneumoniae and e. coli, streptococcus pneumoniae and pneumonia chlamydia infection; 173 of specimens were virus and bacterial infections (at least 1 kind of virus infection and 1 kind of bacteria at the same time), accounted for 41.09% of all positive specimens, and accounting for 73.93% of the bacteria positive specimens.In bacteria and virus infections, the most of merged virus is RSV, followed by ADV,HRV,and PIV2.7. There are no significant differences of the pathogen load between the case group and the control group of each pathogen; and no significant differences of the pathogen load between the single infection and mergered infection groups.ConclusionsWe compare the test results of the case and control groups and found that: bacterial pathogens are the cause of severe acute respiratory tract infections in children under 5;Summer and fall may be the peak season of the bacterial pathogen infetctions; Age is not the factor of bacterial pathogen infection in children under 5;and the number of infected pathogens is also not the factor of bacterial pathogen infections;Bacteria often infect with virus;In severe acute respiratory infection, the most frequently detected bacterial pathogen is streptococcus pneumoniae in specimens of the upper respiratory tract;The study only detected the upper respiratory tract specimens,and failed to fully reflect the bacterial pathogens of infection; Application of antibiotic may influence the outcome of study. |
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