A Cross-Sectional Comparative Study of the Performance of the Widal Test and the Typhidot Immunoassay for Typhoid Fever Diagnosis in the West Region of Cameroon

Background. The diagnosis of typhoid fever based on the Widal slide agglutination test remains a major hurdle in developing countries due to varied perceptions of the value of the Widal test in determining clinical decision-making. We undertook a study to evaluate the diagnostic performance of the Widal test and the Typhidot immunoassay in patients suspected of having typhoid fever in the Menoua division, West Region of Cameroon. Methods. Blood and stool samples were collected from 558 consenting febrile patients on the basis of suspicion of typhoid fever. These patients attended three district health services of the Menoua division between April 2018 and September 2019. These patients had clinical symptoms suggestive of typhoid fever as determined by their consultant. Serum was used for the Widal slide agglutination test and for the Typhidot rapid immunoassay test based on manufacturer’s guidelines. A composite reference of fever plus positive coproculture for Salmonella typhi and Salmonella paratyphi was used as the reference. The sensitivity, specificity, and predictive values of the positive and negative tests were calculated as well as Cohen’s kappa for agreement between the two tests. Results. Of 558 patients, 12.90% tested positive for the reference method, 57.17% tested positive for the Widal slide agglutination test, while 15.59% were positive for Typhidot-IgM. The overall sensitivity, specificity, and predictive values of the positive and negative tests were 80.56%, 94.03%, 66.6%, and 97.03% for Typhidot-IgM and 94.44%, 48.35%, 21.32%, and 98.33% for the Widal slide agglutination test, respectively. Cohen’s kappa estimates were 0.1660 (0.121–0.211) and 0.386 (0.312–0.460) for the Widal test and Typhidot immunoassay for 53.6% and 76.16% agreements of all observations, respectively. Conclusion. The Widal test was found to have a lower predictive value for the diagnosis of typhoid fever in our setting. However, the Typhidot test, although better, was not ideal. Diagnosis of typhoid fever should therefore rely on adequate clinical suspicion and a positive Typhidot test to improve the clinical management of typhoid fever in our setting.

Development of a Simple Method for the Specific Detection of Anthrax Antibody in Sera by Colored Slide Agglutination Test

This study was aimed to identify humoral immune response against anthrax vaccine in mice model by using colored slide agglutination test and detection of field infectivity of anthrax. The field isolates of B. anthracis (n=05) and F34 stern strain vaccine was isolated on agar plates in order to carry out the slide agglutination test. The field isolates of B. anthracis and vaccine bacteria grew on PLET agar medium produced roughly circular and creamy white colonies with ground glass appearance. The bacteria on sheep blood agar media produced rough, sticky, white-gray non hemolytic colonies. Colony polymerase chain reaction (PCR) protocol was adapted to detect fragments of pX01 (596bp) and pX02 (777bp) plasmid of virulent field isolates of B. anthracis. The fragment of pX01 plasmid was only detected in vaccine bacteria. Growth of a field isolate and a vaccine bacteria were colored with crystal violet and used in slide agglutination test to detect anthrax antibodies. The anti-anthrax antibody was prepared by immunizing female mice with 100ül anthrax vaccine through subcutaneous route. Tail bleed were collected on day 0, 30, 60, 120 and 180 of immunization. Cardiac bleed was collected on day 180 of immunization for extensive study. 25μl of diluted (1:10, 1:20, 1:50 and 1:100) antisera and 25μl colored antigen was mixed together onto a clean slide at room temperature and the results was red following 5min, 10mins, 15mins and 20mins of reaction. Unstained antigens and non-immunized sera from the mice were used as control. Results of slide agglutination test showed that the colored vaccine bacteria and field isolates clumped the mice anti-antisera (day 30, 60, and 120) at 1:20 dilution as seen in naked eye but the reaction was seen only at 1:10 dilution while colorless antigens were used. Under microscopic investigation of slide agglutination test, the reaction was read up to 1:100 dilutions with the sera collected at day 30, 60, 120 and 180 of immunization. The Anthrax Sterne strain vaccine induced anti-anthrax immunity in mice that was detected until day 180 of immunization. The clumping reaction was distinct while colored anthrax antigen was used in slide agglutination tests. The colored slide agglutination tests protocol developed in this study can be used to detect anti-anthrax immune response and anthrax bacteria in the field condition with minimum laboratory facilities. Res. Agric., Livest. Fish.7(3): 497-506, December 2020

Evaluation of the Performance of Widal Slide Agglutination Test Compared to Blood Culture and Evaluation of Interferon Gamma Response in the Diagnosis of Typhoid Fever

Typhoid fever remains a public health challenge in developing countries including Nigeria. Widal test is widely used for the diagnosis of typhoid fever due to its simplicity and short turnaround time. However, the specificity of this test has been debated. The aim of the study was to evaluate the performance of Widal test compared to blood culture and determine interferon gamma response among the study subjects. Blood samples were collected from 90 patients who complained of fever and other symptoms suggestive of typhoid fever. Widal slide agglutination test, automated blood culture and interferon gamma concentrations were conducted using rapid antibody detection kit, BACTEC and sandwich enzyme linked immunosorbent assay (ELISA) respectively. Of the 90 samples tested, 63 (70.0%) were positive for anti-Typhi O antigen while 42 (46.7%) were positive for anti-Typhi H antigen. Similarly, 18 (20%) of the blood samples were non- S. Typhi culture positive while 72 (80%) had no bacteria isolated. None of the cases had S. Typhi positive culture. With regards to interferon gamma, subjects with lower levels of 15pg/mL had no bacteria isolated from their blood. As the interferon gamma concentration increased, more subjects had non- S. Typhi bacteria isolated from their blood which shows the relationship between interferon gamma and bacteraemia. The study demonstrated that the use of Widal serology test in the diagnosis of typhoid fever may be erroneous as all the samples were found to be negative for S. Typhi using the gold standard culture methods while Interferon gamma concentration was statistically related to the isolation of non- S. Typhi in blood culture as such, could be a good marker for the development of an alternative screening test, possibly an interferon gamma based detection system for typhoid fever. However, further research is recommended to elucidate that. Keywords: Typhoid, Widal test, Blood culture, Interferon gamma

A comparative study of the performance of the widal slide agglutination test and the typhidot immunoassay for the diagnosis of typhoid fever in the West Region of Cameroon.

Background: The diagnosis of Typhoid fever, based on the Widal slide agglutination test, remains a major hurdle in developing countries like Cameroon due to varied perceptions of the value of the Widal test in determining clinical decision making. We undertook a study to evaluate the diagnostic performance of the Widal test and the typhidot immunoassay in patients suspected of having typhoid fever in the Menoua division, West Region of Cameroon. Methods: Blood and stool samples were collected from 558 consenting febrile patients on the basis of suspicion of typhoid fever. These patients attended three district health services of the Menoua division between April 2018 and September 2019. These patients had clinical symptoms suggestive of typhoid fever as determined by their consultant. Serum from whole blood was used for the Widal slide agglutination test and for the Typhidot rapid immunoassay test based on manufacturer’s guidelines. A composite reference of fever plus positive coproculture for Salmonella enteric serovars typhi and paratyphi was used as reference. The sensitivity, specificity, predictive values of the positive and negative tests were calculated as well as the Cohen’s Kappa for agreement between the two tests. Results: Of 558 patients, 12.90% tested positive for the reference method, 57.17% tested positive for the Widal slide agglutination test while 15.59% were positive for typhidot-IgM. The overall sensitivity, specificity, predictive values of the positive and negative tests were 80.56%, 94.03%, 66.6% and 97.03% respectively for typhidot-IgM; 94.44%, 48.35%, 21.32% and 98.33% for Widal slide agglutination test. The Cohen’s kappa estimates were 0.1660 (0.121-0.211), 0.386 (0.312-0.460) for Widal test and typhidot immunoassay respectively, with agreements of 53.76% and 76.16% respectively. Conclusion: The Widal test was found to have a lower predictive value for the diagnosis of typhoid fever in our setting. However, the Typhidot test, although better, was not ideal. Diagnosis of typhoid fever should therefore rely on adequate clinical suspicion and a positive Typhidot test to improve the clinical management of Typhoid fever in our setting.

COMPARISON OF PERFORMANCE OF TWO WIDAL TEST TECHNIQUES WITH STOOL CULTURE IN THE DIAGNOSIS OF TYPHOID FEVER AT THE DSCHANG DISTRICT HOSPITAL, WEST CAMEROON

Objective: This study is aimed to compare the performance of two Widal test techniques with stool culture in the diagnosis of typhoid fever. Methods: A cross-sectional study was performed at the Dschang District Hospital in patients clinically suspected to have typhoid fever, whose stool was collected for stool culture. Furthermore, venous blood was collected and the serum was tested by both Widal slide agglutination test and Widal tube titration test. Results: The results showed that out of 750 participants include in the study, 325 (43.33%) were positive for Widal slide agglutination test, 174 (23.20%) for Widal tube titration test, and 159 (21.20%) for stool culture. The sensitivity, specificity, positive predictive value, and negative predictive value of Widal slide agglutination test with respect to stool culture were 97.48%, 71.23%, 47.69%, and 99.22%, respectively, but 100%, 97.46%, 91.37%, and 100% for the Widal tube titration test. With the stool culture, Widal slide agglutination test had a moderate agreement (kappa = 0.47), but Widal tube titration test had an absolute agreement (kappa = 0.94). Conclusion: Widal tube titration test should be used in place of Widal slide agglutination test in the diagnosis of typhoid fever in the case of limited access to stool culture test.

COMPARISON OF QUANTITATIVE TUBE AGGLUTINATION AND SEMIQUANTITATIVE SLIDE AGGLUTINATION TEST FOR DIAGNOSING OF THE SUSPECTED CASES OF ENTERIC FEVER

Introduction: Enteric fever is the major health problem of developing country like India, with a notable morbidity and mortality. Isolation of Salmonella the causative agent from Blood is the standard laboratory method for diagnosis, but it is not available at PHC level. So, rapid and affordable diagnostic test like Widal tube and slide agglutination test are used. The present study was done to comparatively evaluate the Widal slide agglutination and tube agglutination test in detecting enteric fever. Methods: A total of 500 patients with clinical presentation suggestive of enteric fever were included in the study whose venous blood was collected. All the samples were tested for the presence of anti O and anti H agglutinins against S. typhi and S. paratyphi A by semi quantitative slide and quantitative tube agglutination tests as per standard protocols. The titers of 1:80 (O agglutinins) and 1:160 (H agglutinins) were taken as the significant titer for the diagnosis of enteric fever. Results: Out of 500 collected samples, 183 (36.6%) was positive by slide agglutination test, whereas, only 145 (29%) were positive by tube agglutination method. The slide test had a sensitivity of 97.2%, specificity of 88.1%, positive predictive value of 77% and negative predictive value of 98.7% as compared to Widal tube agglutination test. Conclusions: Due to high false positivity shown by slide test, it is suggested that serological diagnosis should not be made solely on the basis of slide test rather its results should be confirmed by using Widal tube agglutination test. Keywords: Enteric fever, Slide agglutination test, Widal tube agglutination test, Sensitivity, Specificity

Seroprevalence of Brucella canis in dogs and at-risk humans in Jordan

Brucella canis infection is a neglected zoonotic disease and its seroprevalence in dogs and at-risk humans has not been previously studied in several countries including Jordan. The main aim of this study was to determine the seroprevalence and identify risk factors of B. canis infection in police, breeding and stray dogs and in at-risk humans in Jordan. A total of 169 sera samples from apparently healthy dogs and 185 samples from apparently healthy people (85 from dog handlers and 100 from the general population) were tested in the study. Antibodies against B. canis were tested using the canine D-Tec^® CB Rapid Slide Agglutination Test (RSAT) kit with secondary 2-mercaptoethanol (ME-RSAT). Overall, 8.3% of the dog sera samples tested positive to antibodies against B. canis, and 37.8% of stray dogs tested positive. Seroprevalence was higher in male dogs than in females. Furthermore, none of the tested human samples was positive to antibodies against B. canis. There was a significant association between seropositivity and the type of dog. The study reports preliminary findings that suggest the presence of B. canis among stray dogs in Jordan. Thus, preventive measures should be taken to control the transmission of this pathogen from stray dogs to other dogs and humans as well.