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INTRODUCTION: For 7 years we gained experience of how asthma and chronic rhinosinusitis with nasal polyposis respond to biologics. In contrast, it is much less known, how ASA/NSAID intolerance (Widal's disease) behaves under biologicals. We therefore describe the case of a patient with both clinical conditions who reacted with a severe intolerance reaction under perioperative metamizole administration.

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Enteric fever, an endemic disease, is a significant health problem in developing low- and middle-income countries (LMICs). We studied the utility of Typhoid IgM/IgG assay in Widal titre positive samples among malaria negative patients. A total of 30 febrile patients were included. A blood sample was collected for performing the Widal test and a rapid lateral flow immune assay (Typhoid IgG/IgM tests). A total of 13/30 were positive on blood culture; however, Salmonella typhi grew on only two (6.6%). Of the 30 samples, 24 (80%) were positive for the rapid immunochromatographic (ICT) test None of the samples negative by the rapid ICT test grew Salmonella typhi. The rapid ICT test has better sensitivity and is easy to perform with minimal infrastructure; hence, it is a practical alternative to the age old Widal test.

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Introduction: Widal agglutination test is a serologic investigation that is used to diagnose typhoidfever. This is an easy, fairly inexpensive, and readily available test it'ith questionable reliability. The test performance differs from setting to setting depending on the technique used and otherfactors. The accuracy ofthis test in Ethiopia is poorly understood. So, the aim of this scientific work was to analyze the accuracy of Widal agglutination in diagnosing typhoidfever in Ethiopia. Methods: We performed a systematic review and meta-analysis. Two electronic databases (PubMed/Medline and Google scholar) were searched using preset search strategv to find relevant studies. The methodological quality of the studies included was evaluated "'ith a QUADAS-2. We extracted important variables from the eligible articles. Statistical analysis was conducted using STATA version 14. The protocol of our systematic review and metaanalysis is registered in the International Prospective Register of Systematic Reviews (PROSPERO) with the record number CRD42020194252. Results: The electronic quests yielded 42 papers of which 8 "'ere eligible for analysis. The quality of these studies was rated to be moderate based on the QUADAS-2. The pooled sensitivity, specificity, and negative, andpositive predicthe values ofthe Widal test were 80.8%, 53.0%, 98.5%, and 2.1% respecth'ely. Conclusion: The "'idal agglutination test has average specificity, ven good negative predicth'e value, and ven poor positive predictive value for the diagnosis of typhoidfever. Depending on Widal to diagnose typhoid fever may lead to over-diagnosis of typhoid fever and related complications including inappropriate use of antibiotics. There is an urgent needfor quick and dependable tests for diagnosing typhoidfever, particularly in settings like Ethiopia M'here doing timely culture is notfeasible.

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Invasive Salmonella infection, which can cause typhoid/paratyphoid fever and invasive non-typhoidal salmonellosis, is a public health burden in Africa. Accurate diagnosis and etiological characterization are required to conduct prevalence and risk estimations for Salmonella infection; however, the utilization of optimal techniques and surveillance data are still insufficient. In this study, we performed a laboratory-based survey in Freetown, which is the biggest city in Sierra Leone with a high burden of typhoid fever, by using blood culture and molecular methods but not the Widal test, to estimate the prevalence and aetiology of invasive Salmonella infection among fever patients. We found a very low prevalence of typhoid fever in patients with fever during the investigation period, and this prevalence was clearly overestimated by the Widal test. Genome sequencing of the S. Typhi isolate from this work revealed that the strain carried multiple antibiotic resistance genes, and an epidemic clone that has existed in West Africa for years was also detected in Sierra Leone. By using metagenomic sequencing, one patient with invasive non-typhoidal salmonellosis was identified as having bacterial co-infections. Our data highlight that Salmonella surveillance based on accurate laboratory diagnosis and genome sequencing needs to be strengthened to provide a better estimation of the real epidemics and enable potential risk assessment by etiological analysis in Africa. Even in a laboratory with only basic equipment, it is possible to conduct next-generation sequencing for pathogen discovery in bloodstream infections and to determine the etiological characteristics of pathogene without complex combinations of laboratory methods.

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Introduction Early diagnosis and treatment are crucial to reducing the morbidity of patients with enteric fever/typhoid fever. Among the available diagnostic tests, the blood culture is considered a gold standard. However, in most of the developing and resource-limited settings, the diagnosis is made utilizing the traditional Widal test and rapid immunochromatographic test (ICT). This study was aimed to compare the diagnostic value and efficacy of ICT and traditional Widal test in the diagnosis of typhoid fever. Methods A prospective study was conducted, and 40 patients were included in the study. The Widal test and Salmonella enterica serovar Typhi IgM/IgG immunochromatographic test were performed for all the patients. The Widal is a tube agglutination test, and the rapid ICT utilizes the principle of enzyme-linked immunosorbent assay (ELISA). All the samples were also tested for the presence of antibodies (IgG and IgM) against the S. enterica serovar Typhi and the titers against 'O' and 'H' antigens of S. enterica serovar Typhi. An antibody titer of 1:80 or more against the 'O' and 'H' antigen was considered positive. Results In the ICT, 24 samples (60%) tested positive for the IgM antibodies, and only 15 samples tested positive and for IgG antibodies. In the Widal test, 27 samples (67.6%) returned positive for antibodies against the S. enterica serovar Typhi 'O' antigen. The sensitivity (90% vs 72.73%), specificity (81.25% vs 64%), and accuracy (82.12% vs 64.87%) for the Widal test were found to be more when compared to the ICT. Conclusion The results indicate that the traditional Widal agglutination test is superior to the rapid ICT in the diagnosis of enteric fever. However, both these tests cannot be considered as gold standards for the diagnosis owing to their low positive predictive values.

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INTRODUCTION: Definitive diagnosis of Enteric fever is by blood culture for Salmonella enterica serotype Typhi, Paratyphi A, and Paratyphi B which takes long turnaround time and is costly, whereas Widal test is simple, rapid, and cost-effective test whose interpretation depends on the baseline Widal titers among healthy individuals in a defined population. OBJECTIVES: To determine the baseline Widal titers among apparently healthy urban population of district Jammu (J&K). MATERIALS AND METHODS: 302 individuals in the age group of 18-50 years were recruited. A pretested questionnaire was used to collect demographic and clinical details. The Widal testing was done using commercial Salmonella antigen kit. RESULTS: A total of 302 samples were screened by Widal test. 138 samples (45.69%) were reactive for TO antigen and 64 (21.19%) tested reactive for TH antigen, 3 (0.01%) samples showed agglutination for AH antigen and 3 (0.01%) were positive for BH antigen. Majority of seropositive samples were in dilutions of 1:40 for both TO and TH antigens. CONCLUSIONS: Hence, next higher dilutions showing positivity for both TO and TH antigens, i.e., ≥1:80 may be considered diagnostic for enteric fever in the urban population of Jammu district.

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OBJECTIVE: To determine and compare the performance of TUBEX®TF, Widal test and blood culture in the diagnosis of enteric fever. METHODS: The retrospective study was conducted at the Northwest General Hospital and Research Centre, Hayatabad, Peshawar, Pakistan, and comprised medical record from January to December 2018 related to patients who presented with fever. Typhidot, Widal test and blood culture had been performed as part of evaluation. Data was analysed using SPSS 16. RESULTS: Of the 241 patients, 68(28.21%) tested positive for salmonella in blood culture. Among them, TUBEX®TF was positive in 29(42.64%) and Widal was positive in 25(36.76%). TUBEX®TF had positive predictive value 33.33%, negative predictive value 71.77%, sensitivity 42.65% and specificity 62.34%. The corresponding values for Widal were 24.51%, 69.06%, 36.76% and 55.49%. CONCLUSIONS: Sensitivity, specificity, positive predictive value and negative predictive value of TUBEX®TF and Widal test were very low compared to blood culture.

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BACKGROUND: Typhoid (Salmonella typhi and paratyphi) carriers and gall bladder cancer (GBC) are endemic in northern India. Results of previous studies about association of typhoid carriers with GBC are inconsistent. We studied antibodies against Salmonella typhi and paratyphi in serum samples of patients with GBC. METHODS: We performed modified Widal test for antibodies against Salmonella typhi (Vi and O) and Salmonella paratyphi (AO and BO) antigens in patients with GBC (n=100), xanthogranulomatous cholecystitis (XGC, n=24), chronic cholecystitis (CC, n=200) and healthy controls (HC, n=200). RESULTS: Serum antibodies against Salmonella were more frequently positive in GBC (22%) and XGC (29%), particularly in males in age ≥50 years (GBC: 47% and XGC: 50%) vs. HC (0) (p <0.01). Vi antibody was more common in GBC (13%, OR:9.8) and XGC (8%, OR:5.9) than HC (2%). O antibody was more common in GBC (8%, OR: 8.6) and XGC (8%, OR: 9.0) than HC (1%). O antibody was also more common in males with GBC (12%) than CC (1%) and HC (1%) (P=0.02 and p <0.001, respectively). AO (6%) and BO (4%) antibodies were detected in GBC, particularly in males, than HC (0), (p <0.01). Salmonella antibodies were more frequent in GBC with GS than those without GS (50% vs. 20%, OR=3.94, P=0.01). CONCLUSIONS: Salmonella carrier state was more common in GBC and XGC, particularly in elderly males than HC. The Vi antibody was more common in GBC and XGC than HC. Salmonella infection was more common in GBC with GS than those without GS.

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INTRODUCTION: During identification and diagnosis, typhoid fever (TF) causes various issues such as nonspecific symptoms and nontyphoidal Salmonella-associated febrile diseases. Accurate identification and diagnosis are still a substantial concern. The current study was undertaken to study the clinical profile of TF and the role of Typhifast IgM and Enterocheck WB in early diagnosis. MATERIALS AND METHODS: Clinically suspected TF patients (121) were included in the study. Patients with antibiotic history during the period of febrile illness were excluded. The diagnosis was confirmed with blood culture test. Widal test and two new rapid serological tests: Typhifast IgM and Enterocheck WB were performed. The outcomes were compared with blood culture-confirmed cases to derive the sensitivity and specificity of the diagnostic tests. The clinical characteristics were compared with diagnostic tests using Chi-square test. RESULTS: The most common presentations of TF were fever, chills, vomiting, abdominal pain, anorexia, constipation, and diarrhea. Among the 121 clinically suspected TF patients, 67 had positive blood culture tests for Salmonella typhi. The Typhifast IgM and Enterocheck WB showed sensitivity of 97.01% and 68.52%, respectively. Specificity was also more with Typhifast IgM (85.07%) than with Enterocheck WB (62.96%). When tests were used in parallel combination, 97.01% sensitivity was attained, while the specificity dropped to 46.30%. When used in serial combination, sensitivity of 85.07% and specificity of 85.19% were observed. CONCLUSION: Stepladder fever, abnormal serum glutamic oxaloacetic transaminase (SGOT), and abnormal albumin are associated with blood culture, Typhifast IgM, and Enterocheck WB tests. Rapid serological tests might assist in accurate and early identification of TF. HOW TO CITE THIS ARTICLE: Bhume RJ, Babaliche P. Clinical Profile and the Role of Rapid Serological Tests: Typhifast IgM and Enterocheck WB in the Diagnosis of Typhoid Fever. Indian J Crit Care Med 2020;24(5):307-312.

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INTRODUCTION: Nonsteroidal anti-inflammatory drugs (NSAID)-exacerbated respiratory disease (NERD) is defined by intolerance to cyclooxygenase 1 inhibitors, chronic rhinosinusitis with recurrent nasal polyps, and/or intrinsic bronchial asthma. Long-term administration of acetylsalicylic acid (ASA) after desensitization has been used to mitigate these sequelae, but the optimal dose and balancing symptom relief and side effects remain unsettled. METHODS: Retrospective data analysis of 85 patients with NERD receiving maintenance therapy of 300 mg ASA was followed by questionnaires (our own, not validated and the Sino-Nasal Outcome Test-20). We received responses from 55 patients and examined 30 of them clinically. RESULTS: Patients with no ASA-associated side effects were 56.4% (56 of 85 patients) of the cohort. In this study, 60% (33 of 55 patients) continued prophylaxis of 300 mg ASA daily for an average of 34.7 months. Elective surgery was the most frequent cause of discontinuation of ASA (21.8%; 12 of 55 patients). Rhinomanometry values were significantly improved with ASA (P < .05; Wilcoxon), but there was no significant reduction in nasal polyposis or improvement in olfaction at the time of follow-up examination. CONCLUSIONS: Minor clinical improvements were identified. Side effects were well tolerated by most patients, and no serious sequelae occurred. The indications for long-term ASA therapy in NERD patients remain unsettled.

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Background: Over-dependence on clinical presentation and/or the Widal agglutination test for the diagnosis of typhoid fever in developing countries can lead to antibiotic abuse. In Nigeria, the antibiotic resistance of typhoid organisms is poorly characterized. In this study, we determined the prevalence of culture positivity among patients suspected of having typhoid fever, evaluated the diagnostic value of the Widal test and the burden created by the multi-drug resistance of typhoid organisms in South-East Nigeria. Methodology: This was a prospective and case-controlled study carried out between 2013 and 2016. We acquired samples of blood/stool/urine cultures, and data relating to the Widal agglutination test and malaria parasites from 810 febrile patients (suspected of having typhoid) and 288 apparently healthy controls. Individuals with a history of antibiotic use within the previous 14 days were excluded. We then carried out antibiotic susceptibility tests on all isolates. Multi-drug resistance was defined as a resistance to ≥3 of the antibiotics tested. We determined the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Widal test for typhoid laboratory diagnosis compared to bacterial culture which is the gold standard. A P-value <0.05 was considered to be statistically significant. Results: The mean age of typhoid suspects was 33.1±6.5 years and 50.7% were women. Of the 810 typhoid suspects tested, 114 (14.1%) had positive cultures for the typhoid organisms Salmonella enterica serovar paratyphi (72) and S. enterica serovar Typhi (42). Sample-specific rates of culture positivity were as follows: stool (72; 8.9%), blood (21; 2.6%) and urine (21; 2.6%), P<0.001. None of the controls had typhoid isolates. The sensitivity, specificity, PPV and NPV of the Widal test were 49.1%, 90.7%, 46.2% and 91.6%, respectively. Malaria parasitaemia was detected in 180 (22.2%) febrile patients, out of whom 115 (63.9%) had a positive Widal test for O/H antigens vs. 1% (6/630) in those with negative malaria parasite test results (P<0.001). The rate of false-positive Widal titres was 48%. Antibiotic multi-drug resistance was detected in 52.6% of patients. The antibiotics with the highest susceptibility were ciprofloxacin, levofloxacin and meropenem (all 100% susceptibility) and ceftriaxone (95.6% susceptibility). Conclusion: Our data showed that while typhoid fever is common in Nigeria, malaria is more prevalent. Our analysis showed that the Widal test performed poorly as a diagnostic test and that the burden created by multi-drug resistance was high. Our data indicate that periodic surveillance of antibiotic susceptibility is critical for optimal typhoid therapy.

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This review discusses currently available serological diagnostic methods for typhoid fever with a focus on the clinical utility of TUBEX® TF as an alternative to the Widal or Typhidot test. A literature search was conducted in PubMed for related publications written in English. A qualitative analysis was done to determine various serological tests used for typhoid fever diagnosis with emphasis on TUBEX® TF in comparison to the Widal of Typhidot test. Further, a meta-analysis was performed to obtain a pooled estimate of diagnostic accuracy (sensitivity and specificity) using different analysis models. A total of sixteen studies was included in the qualitative analysis. Further screening of these studies yielded ten studies that were used for the meta-analysis. The sensitivity/specificity range of different commonly used serological tests in typhoid patients is between 55-100%/58-100% for TUBEX® TF, 54-67%/54-95% for Typhidot, and 32-95%/4-98% for the Widal test. As for the pooled meta-analysis estimates, the TUBEX® TF showed superior results when differentiating individuals with febrile illness of unknown origin from those with typhoid fever. Overall, the results of this review and meta-analysis suggest that the TUBEX® TF is more advantageous to use as a serological test for typhoid fever diagnosis due its accuracy and simplicity. However, further studies are still needed to validate our results.

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OBJECTIVE: We set an experiment to determine the diagnostic performance of the Widal test and stool culture in typhoid-suspected cases attending tertiary hospitals in Dar es Salaam, Tanzania using blood culture as a golden standard. We also evaluated the agreement between Widal, stool and blood culture. RESULTS: This was a cross-sectional study conducted between June and September 2018, in three Regional Referral Hospitals in Dar es Salaam, Tanzania. A total of 158 typhoid-suspected cases were enrolled, after obtaining an informed consent. Of the 158 patients participated in the study, 128 (81%) tested positive for the Widal test and 17 (11%) patients were stool culture positive. Widal test recorded 81.5% sensitivity, 18.3% specificity, 10.1% positive predictive value and 89.7% negative predictive value. Stool culture showed 31.3% sensitivity, 91.5% specificity, 29% positive predictive value and 91.5% negative predictive value. In conclusion, Widal test is not reliable for diagnosis of typhoid fever since false positive and negative results are common. In addition, Widal test recorded poor agreement with the blood culture (kappa = 0.014, p < 0.05) while stool culture had strong agreement with the blood culture (kappa = 0.22, p < 0.05).

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Hemophagocytic lymphohistiocytosis (HLH) is a severe disorder of systemic immune dysregulation which can be primary or secondary to autoimmune disorders, malignancy, or infections. We hereby describe a case of a 23-year-old male with severe hepatitis along with pancytopenia and prolonged fever of unknown origin that developed HLH triggered by staphylococcal urinary tract infection. This is a discussion of this unusual disease and its presentation and the diagnostic difficulties which may be encountered in general clinical practice.

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BACKGROUND: Enteric fever is one of the common infectious diseases of humans. The objectives of this study were to:1) estimate the prevalence of enteric fever among febrile patients visiting Ambo hospital; 2) comparison of Widal test and stool culture;3) evaluation of the antimicrobial susceptibility of isolates; and 4) assess potential risk factors to acquire enteric fever infection. METHODS: Blood and stool samples were collected from 372 febrile patients with symptoms clinically similar to enteric fever. Widal test was used for testing sera while stool culturing and bacterial identification was done using WHO standard methods. Susceptibility testing was done using Kirby-Bauer disc diffusion method. Chi-Square test and Logistic Regression analysis were used to analyze the data. RESULTS: The apparent and true prevalence of enteric fever were 56.2% (95% confidence interval [CI]: 50.97-61.29%) and 57.52% (95% CI: 52.3-62.6%) respectively, while, the culture prevalence was 2.7% (95% CI: 1.30-4.89%). Isolation rates of S. Typhi and S. Paratyphi were 0.8% (95% CI: 0.17-2.34%) and 1.9% (95% CI: 0.76-3.84%) respectively. The isolates showed 100% resistance to amoxicillin, bacitracin, erythromycin, 80%resistance to cefotaxime and streptomycin and 20% for chloramphenicol. The sensitivity, specificity, positive and negative predictive values of Widal test was 80.0, 44.5, 3.8 and 98.8% respectively. Multivariable logistic regression analysis revealed that age (adjusted odds ratio [aOR] = 2.45; 95% CI: 1.38-4.37; P = 0.002), religion (aOR = 15.57, 95% CI: 3.01-80.64; P = 0.001), level of education (aOR = 2.60, 95% CI: 1.27-5.28; P = 0.009), source of water (aOR = 2.20, 95% CI: 1.21-3.98; P = 0.009), raw milk (aOR =2.19, 95% CI:1.16-4.16; P = 0.016) and raw meat consumption (aOR = 1.80, 95% CI: 1.07-3.01; P = 0.026) are the predictors of enteric fever seropositivity. CONCLUSIONS: Patients were wrongly diagnosed and treated for enteric fever by Widal test. Therefore, rapid tests with better sensitivity and specificity are needed for the diagnosis of enteric fever. Provision of safe water and health education are vital to bring behavioral change towards raw food consumption.

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BACKGROUND: Widal test is the most widely used laboratory investigation for diagnosis of typhoid. However, the test interpretation remains controversial in the context of endemic regions such as Bangladesh, as agglutination occurs at varied titrations among a large percentage of healthy population. Paired Widal tests are often not feasible; hence single unpaired test has to be used for screening, diagnosis and treatment. OBJECTIVE: We aimed to assess the normal range of baseline titre for Anti TO, TH, AO, AH, BO agglutinins among healthy population in an endemic country with a view to guide the researchers and the clinicians, facilitating further investigation on updating cut off points of single Widal test for screening and diagnosis of typhoid fever in the context of Bangladesh. METHODS: A cross-sectional study was carried out in Mymensingh Medical College, Bangladesh on 2925 male immigration applicants. A single blood sample was collected for Widal test and interpreted using standard guidelines. RESULTS: The highest baseline titer for Anti TO, TH, AO, AH, BO agglutinins among 95% of the healthy participants was found to be 1:80 for each respectively. A titre of 1: 40 was observed for BH antigen. CONCLUSION: In case of singular Widal test, baseline values for the normal range was found to be 1:20 - 1:80 for all the antigens (TO, TH, AO, AH, BO, BH), except BH, for which it was 1:20-1:40. Further studies, inclusive of other sociodemographic groups and positive controls are required to determine the updated cut off values.

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The Fernand Widal syndrome is a set of associations between asthma, nasal polyposis and aspirin sensitivity. Selective cyclo-oxygenase 2 (COX 2) inhibitors are recognized as being a therapeutic alternative in cases needing analgesic or anti-inflammatory treatment. In a retrospective study, we have compiled data concerning oral provocation tests (OPT) undertaken with celecoxib, one of most the selective COX 2 inhibitors, in eight patients with the Fernand Widal syndrome. They were compared with twenty-seven control patients with sensitivity to aspirin or non-steroidal anti-inflammatories, manifesting as asthma, urticaria or rhino-conjunctivitis. Four patients with the Fernand Widal syndrome developed bronchospasm after taking the usually recommended daily dose of celecoxib while all the control patients tolerated it. The Fernand Widal patients who reacted during the OPT had a lower threshold of reactivity to aspirin, a more severe reaction with aspirin, and/or more severe asthma. In patients with the Fernand Widal syndrome, celecoxib is not always a possible alternative to non-steroidal anti-inflammatory drugs. Its introduction must be carried out in a hospital environment under medical supervision.

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AIM: To report a rare case of Salmonella typhi associated endogenous endophthalmitis in an immunocompetent male and to review the available literature. METHODS: Retrospective chart review. RESULTS: A 28-year-old immunocompetent male presented with a 3-day-old history of pain, redness and diminished vision in his left eye. Conjunctival chemosis, corneal haze, and hypopyon were noted and yellowish exudates filled the vitreous cavity. A detailed elicitation of history revealed that patient had been treated for enteric fever that presented with diarrhea and fever, two weeks prior to current presentation. Blood and vitreous cultures grew Gram negative bacilli, identified as S. typhi. Despite intensive intravitreal and systemic antibiotic therapy, an evisceration had to be performed. CONCLUSIONS: Endogenous endophthalmitis can be one of the rare sequelae of enteric fever and may present in the acute and relapsing phases and often times have a rapidly fulminant course with poor visual outcomes.

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INTRODUCTION: Typhoid fever remains a scourge of humanity, especially in developing and under-developed countries due to poor sanitation and food hygiene. Diagnostic methods available for detection of this disease are not satisfactory due to a lack of sensitive, specific, rapid and convenient diagnostic test kits available in the market. AIM: To evaluate the feasibility of a Dot-EIA method for Ig-class specific salivary antibody detection for diagnosis of typhoid fever. MATERIALS AND METHODS: Paired saliva and serum samples were collected in the year 2010 from patients and normal volunteers in Hospital Universiti Sains Malaysia, Kelantan, Malaysia, which is endemic for typhoid fever. A total of 11 culture-confirmed typhoid fever patients, 43 non-typhoid fever patients and 53 normal human control subjects were evaluated for antibodies against a 50 kDa antigen specific for Salmonella Typhi using Dot-EIA. RESULTS: Ig class-specific screening of the test samples showed a higher sensitivity for IgA (90.9%) compared to either IgG (72.7%) or IgM (72.7%) antibodies in saliva, but for serum, IgG (90.9%) had a higher degree of sensitivity compared to IgA (36.4%) and IgM (63.6%). Combining all isotypes (IgA, IgG or IgM), serum showed a higher sensitivity (100.0%) compared to saliva (90.9%). Also, the specificity for serum (100.0%) was much higher than saliva (85.4%). CONCLUSION: Salivary IgA anti-50kDa antibody was found to be more suitable biomarker for routine screening, whereas serum IgG was more suitable for confirmatory test as it has higher specificity. Nevertheless, salivary IgA Dot-EIA is a convenient method for rapid testing, such as for Point-of-Care Diagnostics (POCD) and field epidemiological studies, due to its non-invasive nature and ease of use.

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A nested multiplex polymerase chain reaction (PCR) based diagnosis was developed for the detection of virulent Salmonella typhi in the blood specimens from patients suspected for typhoid fever. After the Widal test, two pairs of primers were used for the detection of flagellin gene (fliC) of S. typhi. Among them, those positive for fliC alone were subjected to identification of genes in Via B operon of Salmonella Pathogenesity Island (SPI-7) where four primer pairs were used to detect tviA and tviB genes. Among 250 blood samples tested, 115 were positive by fliC PCR; 22 of these were negative for tviA and tviB. Hence, the method described here can be used to diagnose the incidence of Vi-negative serovar typhi especially in endemic regions where the Vi vaccine is administered.

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