Field test of a novel detection device for Mycobacterium tuberculosis antigen in cough.

BACKGROUND: Tuberculosis is a highly infectious disease that is spread from person to person by infected aerosols emitted by patients with respiratory forms of the disease. We describe a novel device that utilizes immunosensor and bio-optical technology to detect M. tuberculosis antigen (Ag85B) in cough and demonstrate its use under field conditions during a pilot study in an area of high TB incidence. METHODS: The TB Breathalyzer device (Rapid Biosensor Systems Ltd) was field tested in the outpatient clinic of Adama Hospital, Ethiopia. Adults seeking diagnosis for respiratory complaints were tested. Following nebulization with 0.9% saline patients were asked to cough into a disposable collection device where cough aerosols were deposited. Devices were then inserted into a portable instrument to assess whether antigen was present in the sample. Demographic and clinical data were recorded and all patients were subjected to chest radiogram and examination of sputum by Ziehl-Nielsen microscopy. In the absence of culture treatment decisions were based on smear microscopy, chest x-ray and clinical assessment. Breathalyzer testing was undertaken by a separate physician to triage and diagnostic assessment. RESULTS: Sixty individuals were each subjected to a breathalyzer test. The procedure was well tolerated and for each patient the testing was completed in less than 10 min. Positive breath test results were recorded for 29 (48%) patients. Of 31 patients with a diagnosis of tuberculosis 23 (74%; 95% CI 55-87) were found positive for antigen in their breath and 20 (64%; 95% CI 45-80) were smear positive for acid fast bacilli in their sputum. Six patients provided apparent false positive breathalyzer results that did not correlate with a diagnosis of tuberculosis. CONCLUSIONS: We propose that the breathalyzer device described warrants further investigation as a tool for studying exhalation of M. tuberculosis. The portability, simplicity of use and speed of the test device suggest it may also find use as a tool to aid early identification of infectious cases. We recommend studies be undertaken to determine the diagnostic sensitivity and specificity of the device when compared to microbiological and clinical indicators of tuberculosis disease.

Incidence of protozoal diarrheal disease in an expatriate community in Addis Ababa.

The incidence of diarrheal disease due to Entamoeba histolytica and Giardia lamblia in the United States Embassy American population was recorded over a 25 month period. Overall case rates of 4.2/100 person-months for amoebiasis and 3.3/100 person-months for giardiasis were distinguished by wide variations based on age group and rainfall. In some circumstances, gender and prior living in Africa also correlated with disease incidence. Practitioners should look for these entities in American expatriates in Addis Ababa, especially during the dry season.

Patients infected with the same hepatitis C virus strain display different kinetics of the isolate-specific antibody response.

The antibody response to the hypervariable region of the E2 protein (HVR1) of hepatitis C virus (HCV) was studied in 5 patients who were infected by a common virus strain during an outbreak in a hemodialysis unit. Two patients resolved the infection, while 3 developed chronic HCV infection. For studying the antibody response to HVR1 during the early phase of infection, a Western blot assay using recombinant phage displaying HVR1 was developed. The 2 patients with resolving infection had a more rapid antibody response to HVR1 than did the patients developing chronic infection. Anti-HVR1 antibodies were repeatedly absent in 1 of the chronically infected patients. Antibodies to recombinant E2 protein occurred later than the anti-HVR1 antibodies and did not correlate with resolution of the infection. Thus, the present results suggest that early appearance of antibodies to the HVR1 may predict clearance of HCV infection.

Frequent patient-to-patient transmission of hepatitis C virus in a haematology ward.

Blood transfusion is a well-documented route of transmission of hepatitis C virus (HCV). However, a persisting high frequency of HCV infections was recorded in our haematology ward even after screening of blood donors had been introduced. We investigated the viral strains in 37 patients with haematological malignant diseases who had developed hepatitis C when treated in the ward during 1990-93. 17 of the patients acquired hepatitis C despite being transfused only with blood components screened by second-generation anti-HCV tests. The viral strains were characterised by PCR genotyping and nucleotide sequencing of the hypervariable region of the E2 gene. Five clusters of closely related or identical viruses were found involving 2, 3, 4, 6, and 15 patients, respectively. Blood components could be ruled out as the common source of infection because no donor had given blood to all patients sharing a specific strain, and even donors whose blood had been given to several patients were negative for HCV RNA. All patients in each cluster had been treated in the ward during overlapping periods. These findings suggest that despite strict hygienic control, HCV transmission occurred between patients treated in the same hospital setting, as has previously been reported in a smaller group of haemodialysis patients.

Low incidence of syphilis among factory workers in Ethiopia: effect of an intervention based on education and counselling.

BACKGROUND: The prevalence and incidence of syphilis infection were examined in a cohort study of factory workers in Ethiopia. METHOD: Between February 1997 and March 1999, 409 men and 348 women were enrolled and followed in the cohort study. RESULTS: The prevalence (95% CI) of past/current syphilis (positive TPPA serology) was 28.9% (25.7% to 32.3%), and factors associated with past/current syphilis were markers of risky sexual behaviours including HIV infection. In this cohort of factory workers subject to public information/education meetings, testing for HIV antibodies, and individual counselling, the incidence (97.5% one sided CI) of new syphilis infections was 0/691 = 0 (0 to 0.5) per 100 person years. CONCLUSION: This study has documented a reduction in risky sexual behaviours and a low syphilis incidence among factory workers participating in a cohort study on HIV infection progression in Addis Ababa.