The Following-up Investigation And Study On Diagnostic Methods Of Human Brucellosis

Brucellosis is a zoonotic disease caused by bacterial genus Brucella that is endemic worldwide, especially in Mediterranean area, Asia, Africa and Latin America. China has ever successfully controlled brucellosis incidence during 1990s. With the development of animal husbandry in recent years, human brucellosis is re-emerging in many areas, causing large economic losses and serious public health problem.Acute brucellosis has a good cure rate, but brucellosis tend to turn into chronicity and relapse. Therefore, following-up investigation of brucellosis patients benefit grasp disease process, adaption of treatment, and exploring outcomes factors. The diagnosis of human brucellosis relies on correct and sensitive laboratory diagnostic methods, aiming at seeking patients in time, giving proper treatment. Nowadays different laboratory assays have own advantages and disadvantages. Systematic evaluation of these methods in diagnosis and following-up investigation is necessary.Objective:Through following-up investigation of brucellosis patients from CDC of Songyuan City of Jilin Province, get to know disease process and clinical changes, and evaluate the significance of brucellosis following-up; analyze and compare culture, serological tests and PCR assays, providing evidence for improving diagnostic level of human brucellosis.Methods:Follow up and treatment 50 initial acute brucellosis patients of Center of Disease Control (CDC) of Songyuan City, Jilin Province, at initial diagnosis,3,6, 12 months after diagnosis. Diagnose 218 outpatients and 50 following-up patients with culture, serological tests (PAT and SAT) and PCR assays. Identify isolates with PCR at genus and species level.Results:①92.0% following-up brucellosis patients have contact history with livestocks, among which 28.3% stop contact after diagnosis.8.0% have no occupational risk.32.0% have infected family members.37.5% happened at diagnosis, and 62.5% happened during following-up period;②88.0% following-up patients come to hospital within 1 month after onset.8.0% are free of symptoms. The most frequent symptoms are Fever/chill, myalgia/arthralgia, malaise, hyperhidrosis, wandering pain, and headache/dizzy.8.0% have only one symptoms, and 84.0% have 2 and more symptoms. Symptoms difficult to cure include malaise, fever, myalgia/arthralgia, and new symptoms appeared in following-up period include myalgia/arthralgia, malaise and hyperhidrosis.③30.0% patients take drug before diagnosis.66.0% and Chinese traditional medication to antibiotics.68.0%patients cure,26.0% fail to cure.3 cases keep free of symptoms and 3cases relapse. The duration from onset to diagnosis influences outcomes (P＜0.05).④Among 218 outpatients, the positive rate of blood culture is 11.0%, the positive rate of serological tests is 32.1%, while PCR is 33.9%. The agreement of serological tests and PCR is 78.9%.⑤Among cultured-confirmed brucellosis patients, the positive rate of serological tests is 66.7%, and various PCR ranges from 17.4% to 87.0%, while the combined PCR is 100.0%; All isolates are B.melitensis identified by PCR assays.⑥Among following-up patients,12.0% are positive-culture at admittance, but the samples from following-up are all negative. The positive rate of serological test are 94.0%,14.0%,38.0% and 40.0% respectively at admittance and 3,6,12 months after diagnosis, while the positive rate of PCR are 82.0%,80.0%,66.0%,64.0% respectively. Accordingly, the agreement rates of PCR and serological tests are 76.0%, 30.0%,40.0%,44.0%. There is no statistic significance between these two methods at different time points (P＞0.05).⑦The concordance rates of symptoms and serological methods at different time point are 86.0%,54.0%,58.0%,62.0% and symptoms and PCR are 74.0%,60.0%,46,0% and 34.0%. Statistc significance is only found at 3 month after treatment between symptoms and serological tests. There is no statistic significance between symptoms and PCR assay (P＞0.05).Conclusion:Following up brucellosis patients benefit in finding new cases and develop preventive measures, understanding evolution process of disease and find chronic and relapse patients. Different laboratory methods have own advantages and disadvantages:Blood culture is golden standard but the positive rate is low and time-consuming, so is limited in screening investigation. Culture-negative people are still possibly infected. Serological methods, which are fast and convenient, are appropriate to screening, but inefficient for early detection, chronic stage. PCR is able to identify brucella isolates. PCR plays an assistant role in routine clinical application for culture and serological methods, and more helpful in following-up patients.