| Backgroud and ObjectiveStreptococcus pneumoniae is the main pathogen causing community-acquired infections,causing high morbidity and mortality worldwide.S.pneumoniae plays an important role in children's community-acquired infections.China is a high incidence area of pneumococcal infectious diseases.According to different infection sites,S.pneumoniae infectious diseases are classified into two categories: noninvasive pneumococcal disease(NIPD)and invasive pneumococcal diseases(IPD).IPD refers to an infectious disease in which S.pneumoniae is isolated from normal sterile parts such as blood,cerebrospinal fluid and so on.IPD is a global disease that seriously threatens human health.It is characterized by high pathogenicity and high mortality,especially in immunocompromised populations such as children,the elderly,AIDS and congenital immunodeficiency patients.Children's immune system is not well developed,and the rate of colonization of S.pneumoniae in the nasopharynx is high.These factors lead to a higher prevalence of invasive pneumococcal disease in children.At present,there are more than 90 types of S.pneumoniae serotypes that have been verified by research.S.pneumoniae serotypes vary from country to country.The serotypes of S.pneumoniae infection in children under 5 years old in China are most common in 19 F,19A,14,6B,23 F,and 15.The selection of S.pneumoniae vaccine is closely related to the distribution of local serotypes.Populations from different countries and regions should use the corresponding pneumococcal vaccine according to the local serotype distribution.At present,the commonly used S.pneumoniae serotyping methods mainly include a capsule swelling test and a multiplex PCR method.In recent years,with the wide application of antibiotics,a large number of drug-resistant S.pneumoniae has appeared in the clinic,which poses a great challenge to the current treatment strategy of S.pneumoniae.The drug resistance problem of S.pneumonia has become a worldwide public health problem.In 2017,the World Health Organization listed S.pneumoniae as one of the 12 priority pathogens.The persistent high disease burden and increased resistance to antibiotics such as penicillins and macrolides have attracted the attention of scholars around the world.S.pneumoniae mainly produces resistance to ?-lactam antibiotics through genetic alteration of penicillin binding proteins(PBPs).Mutations in the PBPs gene reduce the affinity of ?-lactam antibiotics for S.pneumoniae and lead to drug resistance.There are three main mechanisms of resistance to S.pneumoniae to macrolide antibiotics: changes in ribosome target sites;enhanced efflux mechanisms;50S ribosomal mutations.Mastering the drug resistance and major drug resistance mechanisms of S.pneumoniae in the region are of great significance for guiding the rational use of antibiotics and controlling the development of drug resistance.In this study,the clinical characteristics of children with invasive infection of S.pneumoniae was statistically analyzed,and the serotype distribution,drug resistance and drug resistance mechanism of S.pneumoniae were studied.This study will promote the diagnosis and treatment of children with invasive pneumococcal disease;help to reduce infection rate and mortality;provide basis for vaccination and vaccine research for children with pneumococcal vaccination;and provide reference for clinical rational application of antibacterial drugs,control of drug resistance development and antibacterial drugs research.Materials and methods1.Select 93 children diagnosed with invasive pneumoniae diseases from January 2016 to December 2018 as the experimental group.We consulted the patient's medical record information and preserved the S.pneumoniae strain.2.Statistics on gender,age,season of onset,type of infection,clinical manifestations,isolated specimens,complications,auxiliary examination,treatment and prognosis of children with S.pneumoniae infection.Then we studied the clinical characteristics and susceptibility factors of children with S.pneumoniae infection.3.We used capsular swelling experiments to serotype S.pneumoniae strains.4.We conducted drug susceptibility tests on S.pneumoniae strains and statistically analyzed antibiotic resistance of S.pneumonia.5.The DNA of S.pneumoniae was extracted and the expression of macrolide lactone resistance gene of S.pneumoniae was determined by PCR.Result1.Clinical characteristics and susceptibility factors of children with pneumococcal infection1.1 Invasive pneumoniae diseases mainly affect infants and young children under 3 years of age,causing bloodstream infections and central nervous system infections.1.2 The clinical manifestations of children with invasive pneumoniae diseases are mainly fever,cough,and apathy.In this study,26.9% of the children had underlying diseases,and 35.5% of the children had complications during the course of the disease.1.3 Most of the infected children with blood leukocytes,CRP,PCT and other infection indicators increased significantly.1.4 In this study,10 patients eventually died.Children under 1 year old,complications such as organ failure,decreased white blood cells,significantly elevated CRP,and significantly elevated PCT are the main risk factors for death.2.Distribution of S.pneumoniae serotype2.1 The isolates of 108 strains of invasive S.pneumoniae isolates in this study were: 19F(28.7%),19A(15.7%),6B(11.1%),14(9.3%),and 23F(7.4%).2.2 The serotype coverage rates of the four vaccines PCV7,PCV10,PCVl3,PPV23 were: 59.3%,59.3%,95.4%,94.4%.2.3 The serotype distribution of invasive S.pneumoniae isolates of different age groups had no obvious specificity.3.Analysis of drug resistance of S.pneumoniae3.1 The resistance rate of S.pneumoniae to ?-lactam antibiotics such as penicillin continued to increase.In this study,the resistance rate of S.pneumoniae to penicillin has reached 17.1%.The resistance rates of other ?-lactam antibiotics such as amoxicillin,cefotaxime,cefepime and meropenem were slightly lower.3.2 The drug resistance of S.pneumoniae in infants under 1 year old is significantly higher than that in other age groups,which should be paid attention to.The resistance rate of S.pneumoniae cerebrospinal fluid isolates was higher than that of other isolates;3.3 The resistance rate of PNSP to ?-lactam antibiotics is higher than PSSP.It is indicated that the resistance of S.pneumoniae to ?-lactam antibiotics is mainly caused by the production of PBPs.4 Study on the resistance mechanism of S.pneumoniae to macrolide antibiotics4.1 The resistance mechanism of S.pneumoniae to macrolide antibiotics is mainly due to ermB gene-mediated ribosome target changes.4.2 A certain proportion of mefA and mefE gene-mediated active efflux mechanisms were also detected in children with invasive infections in the region.4.3 The detection rate of dual macrolide resistance genotypes of children with invasive infection of S.pneumoniae in this region was as high as 56.5%.Conclusion1.Invasive pneumococcal infection mainly affects infants under 3 years of age,invading the bloodstream,central nervous system,etc.Ages,complications,and elevated inflammatory markers are risk factors for death.2.The distribution of serotypes of children with invasive S.pneumoniae infection was mainly 19 F,19A,6B,14,23 F,etc.PCV13 vaccine coverage(95.4%)is the highest.3.Invasive infection with S.pneumoniae continues to increase resistance to ?-lactam antibiotics such as penicillin.Invasive infection with S.pneumoniae is highly resistant to erythromycin and clindamycin.Clinicians should rationally choose antibiotics to treat children with invasive S.pneumoniae infection based on drug susceptibility results.4.The resistance mechanism of S.pneumoniae to macrolide antibiotics were mainly caused by the change of ribosome target mediated by ermB gene,and the mef gene were detected. |
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