| BackgroundPertussis is a vaccine-preventable acute respiratory infectious diseases,caused by B.pertussis.It is one of the most common diseases of children with respiratory infections.The course can last for a few weeks or more.Typical clinical manifestations is paroxysmal spasmodic cough.Pertussis toxin antibody(PT-IgG)is pertussis specificity antibodies,resulting in no lifelong immunity after vaccination and natural infection immunity.Non-immunized people are susceptible to infections,and infected infants and children would be more seriously ill than adults.In recent years,pertussis regeneration appears constantly in the world,and the prevalence of pertussis has increased.Studies have suggested that the prevalence of pertussis in China may be greatly underestimated.The number of the not diagnosed may be as high as 95%of the infected people,especially for teens and adults.These undetected infections are a great threat for causing a pertussis epidemic.For a long time,B.pertussis infects infants and young children,but due to the change of atypical clinical symptoms and transmission mode,it has shown that it is transmitted to infants and young children mainly from teenagers and adults.Health care practitioners represent pertussis infection and carrying condition of adult.At the same time the check of influenza cases against B.pertussis can help understand the pertussis infection rate among infants and children and identify pertussis incidence in infants and children.It also can be a warning for possible infection of babies.Traditional detection techniques of B.pertussis mainly include culturing of pathogen,detection of toxin serum antibody,and rPCR detection method about specific genes IS481.Cultivating was low while serum antibody testing is suitable for the diagnosis of the previous infection of pertussis and antibody effect evaluation after vaccination,and although rPCR detection method has high sensitivity and specificity,it will affect the sensitivity of the nucleic acid detection in the process of practical application due to the decreasing of pharyngeal swab bacteria caused by specimen collection,transportation and so on.There are still insufficient investigations on germ-carrying of healthy people.For all the above reasons,this subject is on the basis of the existing rPCR detection method to further establish nPCR and rPCR detection method used for fast and accurate diagnosis of pertussis.This research regards the practitioners of health certificates,Clinical pertussis suspected cases and influenza-like cases as the research object,combining with serological detection method.It is aimed at investigating and researching Pertussis infection and the epidemic situation in Suizhou,Hubei Province.Purpose of researchThe study is based on cross-sectional research,put the practitioners of health certificates,influenza-like cases and clinical suspected cases of pertussis as the research object to investigate current status and incidence of pertussis infection,and study the epidemiological feature,to provide the basis information for prevention and pertussis monitoring in the future.MethodIn allusion to B.pertussis specific gene IS481 design suitable outside primers and optimize reaction conditions,establishing nPCR combined with rPCR method,based on the existing serum resistance PT-IgG antibody testing method to carry out the pertussis infection and epidemic status of the research in people.Results(1)This research established nPCR and rPCR combined method to detect S.pneumoniae,H.influenzae,S.aureus,M.pneumoniae,N.meningitidis,M.catarrhalis,B.holmesii,B.parapertussis,B.branchiseptica,B.pertussis,except the B.pertussis and B.holmesii others were negative.This suggests that this method has high specificity for genus detection of the Bordetella.Determining the B.pertussis nucleic acid concentration and adjusting to 10ng/μl times then(10 times)diluting on the fluorescent quantitative PCR amplification reaction,the detection efficiency of the two methods is different,the limit of rPCR was 10-4ng/μl,while nPCR combined with rPCR method detection limit was 10-6 ng/μl,and the Ct value of the latter is smaller.Compared with the two methods,the method established in this study has higher sensitivity,and can be used to survey the crowd of pertussis infection,and can provide basis for clinical diagnosis of pertussis.(2)A total of 124 samples out of 354 throat swab specimens of influenza-like cases were tested positive for influenza virus.Using the test method established in this research,17 of all influenza-like cases were tested positive for Bordetella pertussis,among which B-pertussis were detected in 8 cases tested positive for influenza virus and 9 cases tested negative for influenza virus.However,using rPCR method specific for testing B.pertussis in positive influenza virus cases,B.pertussis was found in 1 case and it was not detected in negative influenza virus cases.For 34 clinical suspected pertussis cases,12 were tested positive for B.pertussis.A total of 18 samples are positive of pertussis infection among 508 populations.The recent infection rate was 3.54%,the geometric mean concentration(GMC)was 4.67 IU/ml.PT-IgG<5 IU/ml accounted for 50.98%(259/508),and we always think PT-IgG<5IU/ml susceptibility higher internationally,the highest susceptibility age was 27～36 years old,the positive rate was 4.40%,GMC was 3.59 IU/ml.There was no significant difference between regions,different age groups and gender antibody positive rate;geometric mean concentration(GMC)had no significant difference between areas and gender,but there was significant difference between different age groups.Which has potential risk of morbidity and popularity.(3)Monitoring the clinical suspected cases of pertussis,for the first time we found that the spread of pertussis in adults to infants caused by the incidence of familial aggregation.ConclusionsWe established nPCR combined with rPCR method which has more sensitivity and specificity than the rPCR,and it can be used in the investigation of pertussis infection.We also found that there is a prevalence of pertussis infection and epidemic in Suizhou,Hubei Province.The crowd of PT-IgG antibody level is low,pertussis susceptibility is higher,it indicates potential risk.Compared with the data reported by the statutory infectious disease report system in Suizhou,there exists greatly underestimation and omission of pertussis infection and prevalence.The propagation mode of family aggregation in which infected adults passing pertussis to infants should be brought to attention in order to prevent a potential pertussis epidemic. |
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