Diagnosis Of Latent Infection Research Articles

Comparative epidemiology and pathophysiology of patent and latent babesiosis caused by Babesia bigemina in buffaloes and cattle from different agroclimatic zones of Punjab State, India.

To conduct comparative epidemiology of parasitologically positive (patent) and polymerase chain reaction positive (latent) cases of bovine babesiosis in Bet Region (low-lying areas adjoining Sutlej, Beas, Ravi, and Ghaggar rivers of Punjab) of diverse agroclimatic zones of Punjab state in relation to haematobiochemical parameters as patho-physiological markers, blood samples from 783 dairy animals (487 buffaloes and 296 cattle) were analysed parasitologically by Giemsa-stained blood smears (GSBS) and by molecular-based polymerase chain reaction (PCR) targeting SpeI-AvaI restriction fragment of Babesia bigemina. We ruled out the endemicity of the disease with 2.17% patent and 3.96% latent cases of B. bigemina with significantly higher prevalence (P < 0.01) in cattle than buffaloes. The spatial distribution for a guideline to local veterinary practitioners and policy-makers indicated highest number of patent and latent cases in western zone and undulating plain zone, respectively. District wise highest prevalence of patent as well as latent infection observed in SBS Nagar of undulating plain zone showed substantial agreement (Kappa value: 0.70) between the two techniques. Haematology revealed marked microcytic hyperchromic anaemia in patent animals of group I (GSBS positive; n = 17) and latent animals of group II (PCR positive; n = 14) as compared to disease-free controls (group III; n = 10). Blood urea nitrogen (BUN), creatinine and gamma-glutamyltransferase (GGT) levels were significantly increased (P < 0.05) in group I in comparison to group II and group III indicated comparative pathogenic effect of babesiosis in patent cases. Though patent cases showed higher pathogenicity of babesiosis, diagnosis of latent infection is significant as it may act as source of infection for spread to other highly prone bovines.

Defining an intermediate category of tuberculin skin test: A mixture model analysis of two high-risk populations from Kampala, Uganda.

One principle of tuberculosis control is to prevent the development of tuberculosis disease by treating individuals with latent tuberculosis infection. The diagnosis of latent infection using the tuberculin skin test is not straightforward because of concerns about immunologic cross reactivity with the Bacille Calmette-Guerin (BCG) vaccine and environmental mycobacteria. To parse the effects of BCG vaccine and environmental mycobacteria on the tuberculin skin test, we estimated the frequency distribution of skin test results in two divisions of Kampala, Uganda, ten years apart. We then used mixture models to estimate parameters for underlying distributions and defined clinically meaningful criteria for latent infection, including an indeterminate category. Using percentiles of two underlying normal distributions, we defined two skin test readings to demarcate three ranges. Values of 10 mm or greater contained 90% of individuals with latent infection; values less than 7.2 mm contained 80% of individuals without infection. Contacts with values between 7.2 and 10 mm fell into an indeterminate zone where it was not possible to assign infection. We conclude that systematic tuberculin skin test surveys within populations at risk, combined with mixture model analysis, may be a reproducible, evidence-based approach to define meaningful criteria for latent tuberculosis infection.

Enlargement of Gold Nanoparticles for Sensitive Immunochromatographic Diagnostics of Potato Brown Rot.

Lateral flow immunoassay (LFIA) is a convenient tool for rapid field-based control of various bacterial targets. However, for many applications, the detection limits obtained by LFIA are not sufficient. In this paper, we propose enlarging gold nanoparticles’ (GNPs) size to develop a sensitive lateral flow immunoassay to detect Ralstonia solanacearum. This bacterium is a quarantine organism that causes potato brown rot. We fabricated lateral flow test strips using gold nanoparticles (17.4 ± 1.0 nm) as a label and their conjugates with antibodies specific to R. solanacearum. We proposed a signal enhancement in the test strips’ test zone due to the tetrachloroauric (III) anion reduction on the GNP surface, and the increase in size of the gold nanoparticles on the test strips was approximately up to 100 nm, as confirmed by scanning electron microscopy. Overall, the gold enhancement approach decreased the detection limit of R. solanacearum by 33 times, to as low as 3 × 104 cells∙mL–1 in the potato tuber extract. The achieved detection limit allows the diagnosis of latent infection in potato tubers. The developed approach based on gold enhancement does not complicate analyses and requires only 3 min. The developed assay together with the sample preparation and gold enlargement requires 15 min. Thus, the developed approach is promising for the development of lateral flow test strips and their subsequent introduction into diagnostic practice.

Duplex PCR for detection of early and late blight coinfecting potato

The disease identification at initial level is utmost factor for management of any disease. The detection of early and late blight at initial level is more important for its management due to fast spreading behaviour of these diseases as late blight devastates entire crop within a week. Although, morphological and serological methods are available, but due to their time consuming nature, sometimes there is failure in diagnosing latent infection with very low level inoculums. Moreover, diagnosis of both the diseases one by one is laborious. Therefore in the present investigation, a duplex PCR method was developed for simultaneous detection of Alternaria solani and Phytophthora infestans. PCR conditions and annealing temperature of both the primers [PINFTH2 (F)-GGGGGTCTTACTTGGCGGCG, PINFTH2(R)-CAAACCGGTCGCCAACTCGC for P. infestans and BIAMASbt (F)-GCTCCCACTCCTTCCGCGC, NBAIMASbt(R)-GGAGGTGGAGTTACCGACAA for A. solani] were standardized separately. Then the optimization of the PCR reactions and condition of duplex PCR was also standardized. The results revealed detection of single amplicon of 524bp with P. infestans while with A. solani 289bp amplicon was detected in genomic DNA from mycelium as well as in plants infected with both the diseases. This duplex PCR enabled the simultaneous detection of both the pathogens. In early stages of disease development, suspected samples (plants & tubers) were tested with this duplex PCR, which could diagnose both the pathogens correctly. The protocol will help in diagnosis of latent infection in potato tissues; and it will also be used as a diagnostic tool for researchers engaged in potato seed production and multiplication reducing cost and time thereby.

A Step toward Tuberculosis Elimination in a Low-Incidence Country: Successful Diagnosis and Treatment of Latent Tuberculosis Infection in a Refugee Clinic.

Objectives. Approximately 65 percent of tuberculosis (TB) cases in Canada each year occur from reactivation in foreign-born individuals. Refugees are at high risk after immigration. Routine screening of this population for latent TB infection (LTBI) is generally considered infeasible. We evaluated the outcome of LTBI screening and treatment amongst refugees. Methods. Government-sponsored refugees in Edmonton are seen at the New Canadians' Clinic and screened for TB and LTBI. We reviewed records of patients between 2009 and 2011. Completeness of initial assessment, diagnosis of latent infection, and completion of LTBI treatment were evaluated. Treatment for LTBI was offered when patients had a positive Tuberculin Skin Test (TST) and risk factors for progression to TB. An Interferon-Gamma Release Assay (IGRA) was performed on all other TST positives; treatment is only offered if it was positive. Results. 949 refugees were evaluated. 746 TSTs were read, with 265 positive individuals. IGRA testing was performed in 203 TST positive individuals without other TB risk factors; 110 were positive. LTBI treatment was offered to 147 of 151 eligible patients, 141 accepted, and 103 completed a treatment course. Conclusion. We observed high proportions of patient retention, completion of investigations, and treatment. This care model promises to be a component of effective TB prevention in this high-risk population.

Tuberculose infantil novas formas de diagnóstico

Introduction: Tuberculosis is still a serious public health problem. To decrease the number of cases of active tuberculosis in populations of low and intermediate incidence, a rapid diagnosis and effective treatment is necessary. The tuberculin test is the recommended method of screening, but there are well-known limitations. Since 2001, the interferon gamma release assays have emerged, being considered useful in the diagnosis of latent infection with Mycobacterium tuberculosis and already widely used in adults. Objectives: Summarize the available information on interferon gamma release assays, particularly with regard to the technique; advantages in the diagnosis of latent infection with Mycobacterium tuberculosis; sensitivity and specificity in the pediatric population; characterization of interfering factors; and their significance of monitoring of tuberculostatic treatment. Development: Interferon gamma release assays are immunoassays that measure Interferon Gamma Release Assays response to Mycobacterium tuberculosis antigens. These tests have been applied in paediatrics population and in regions with different prevalence rates of tuberculosis, in order to compare them with the tuberculin skin test in regard to sensitivity and specificity. Conclusions: Its usefulness as a means of screening in Paediatrics has limitations. Studies are needed at national level to identify how tuberculin skin test and interferon gamma release assays must be articulated. Currently, interferon gamma release assays only complement tuberculin skin test.

Recent Advances in Tuberculosis Diagnosis: IGRAs and Molecular Biology

Tuberculosis (TB) is one of the most deadly, curable infectious diseases. In 2012, the World Health Organization (WHO) reported 8.6 million new TB cases and 1.3 million deaths. Despite intensive research to improve tuberculosis diagnosis and drug susceptibility testing, TB still remains one of the most threatening curable infectious diseases. Effective control of TB remains in prevention, the immediate detection of Mycobacterium tuberculosis and rapid detection of drug-resistant strains, followed by prompt implementation of an adequate anti-tuberculous therapy. Providing rapid antibiotic resistance detection systems is essential to treat accurately the patients, especially with the emergence and spread of drug-resistant TB. In 2012, WHO reported 84,000 confirmed multi-drug-resistant TB cases worldwide, and 9.6 % of these cases were extensively drug-resistant TB. However, conventional techniques for culture isolation and antibiotic susceptibility testing are slow. In recent years, the molecular basis of resistance to anti-tuberculous drugs has been elucidated. Molecular methods based on sequencing have been used to detect the main mutations involved in resistance from isolated strains and clinical samples. New molecular methods have been developed to detect the most common mutations conferring M. tuberculosis resistance. Furthermore, the diagnosis of the latently infected people allows measures to prevent them from developing the active disease, and thus help break the chain of transmission of the microorganism. The tuberculin skin test, the classical method for diagnosing latent TB infection, has several drawbacks: low specificity, and also a low sensitivity in immunosuppresed patients. The development of the IFN-γ release assays (IGRAs), with a recognized higher specificity, has improved the diagnosis of latent TB infection. However, for the correct use and interpretation a close cooperation between physicians and expert microbiologists is required.

Conventional PCR for molecular diagnosis of human strongyloidiasis

Strongyloidiasis is frequently asymptomatic and diagnosis of latent infection is difficult due to limitations of current parasitological and serological methods. This study aimed to verify the use of conventional polymerase chain reaction (PCR) assay for molecular diagnosis of Strongyloides stercoralis infection. Fresh stool samples were obtained from 103 individuals: 33 S. stercoralis positive, 30 positive for other parasites and 40 negative for parasitological methods. These samples were examined by the Lutz, Rugai and agar plate culture methods and conventional PCR assay. Two sets of primers (S. stercoralis species-specific and genus-specific sets), located in the 18S ribosomal RNA gene, were used for PCR. Of the 33 samples positive for S. stercoralis by parasitological methods, 28 (84.8%) were also detected by PCR assay using species-specific primers and 26 (78.8%) using genus-specific primers. Among the stool samples negative by parasitological methods, seven (17.5%) were positive by PCR using species-specific primers and two (5.0%) using genus-specific primers. In conclusion, the conventional PCR assay described in this study using a species-specific primer pair provided a molecular method for S. stercoralis diagnosis in human stool samples.

Immunogenicity of latency-associated antigens of Mycobacterium tuberculosis in DNA-vaccinated mice

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), persists within infected macrophages for long periods of time in a metabolically inactive but reversible state known as dormancy. Since the majority of adult pulmonary TB is caused by the reactivation of persistent Mtb, novel vaccines to protect against disease reactivation and novel biomarkers to provide the basis of new diagnosis of latent infection are urgently needed. To meet this demand, we assessed the immunogenicity of 32 latency-associated proteins in DNA-vaccinated mice. By using a Helios gene gun, BALB/c and C57BL/6 mice were vaccinated with plasmids carrying DNAs for latency-associated antigens encoded by the DosR regulon. Of the 32 antigens tested, 12 induced antigen-specific T-cell responses in vaccinated BALB/c mice and 9 induced responses in C57BL/6 mice. Five antigens (Rv1998c, Rv2031c, Rv2032, Rv2623, and Rv3132c) induced T-cell responses in both mice strains. In addition, at least 12 and 3 antigens induced antigen-specific antibody production in vaccinated BALB/c and C57BL/6 mice, respectively. Of these, 3 antigens (Rv2029c, Rv2626c, and Rv3132c) induced strong antibody production in both mice strains. These results might be applicable for the future development of a novel vaccine and biomarkers for latent TB infection, although further analyses in human blood samples are necessary.

O474 Utility of the IFN-g assays using Mycobacterium tuberculosis -specific antigens for the diagnosis of latent infection in contacts of people with sputum smear-positive pulmonary tuberculosis

O474 Utility of the IFN-g assays using Mycobacterium tuberculosis -specific antigens for the diagnosis of latent infection in contacts of people with sputum smear-positive pulmonary tuberculosis

Diagnosis of Latent Infection About The Jaws: II

Diagnosis of Latent Infection About The Jaws: II

Diagnosis of Latent Infection About The Jaws: I

Diagnosis of Latent Infection About The Jaws: I