Browsing by Author "Sehgal, S C"
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Item Aedes aegypti (L) in Port Blair, Andaman and Nicobar islands-distribution and larval ecology.(1999-09-01) Shriram, A N; Sehgal, S CA comprehensive survey was carried out in the Port Blair town in Andaman and Nicobar islands, in order to study the distribution and relative prevalence of Aedes aegypti during the monsoon (July'1997-October'1997) season using larval survey and adult collection methods. Ae. aegypti was found in all 21 localities surveyed. Spatial variations in distribution was evident which was closely related to population density. The nature of the larval habitats was observed to be similar in all the localities. For both outdoor and in-door containers, breeding preference ratio was highest for mud/brick/cement containers, followed by metal and plastic containers. These findings are correlated with water storage habits of the residents in the localities surveyed.Item Antigenic relatedness between enterotoxins of Escherichia coli associated with adult and infantile diarrhoea.(1981-02-01) Tabaraie, B; Sehgal, S C; Singh, A; Vadehra, D VItem Clinico-epidemiological study of hospitalized cases of severe leptospirosis.(1999-03-18) Singh, S S; Vijayachari, P; Sinha, A; Sugunan, A P; Rasheed, M A; Sehgal, S CIn an attempt to understand the clinical spectrum and pathological and biochemical abnormalities and their prognostic importance in leptospirosis, a prospective study was carried out in Port Blair during September 1996 to August 1997. Out of 80 patients suspected to have leptospirosis, 58 were proved to have current leptospiral infection using serological tests and among these, 14 died giving a case fatality rate of 24.1 per cent. The incidence of the disease showed two separate peaks roughly coinciding with the paddy sowing and harvesting season and the majority of the patients had history of exposure to wet and water logged environment prior to the attack of the disease. The disease presented as two separate clinical syndromes--the hepato-renal form and the pulmonary form though some degree of overlap was present. Hepatic and renal complications occurred in 30 patients each with 26 of them having both. These generally occurred late in the course of the disease and the mortality rate was relatively low. In contrast pulmonary complication occurred quite early and the case fatality rate in those patients was very high (6.7% vs 42.9%). The other complications encountered in the current series of cases were refractory hypotension probably due to myocarditis in 40 per cent and neck stiffness and altered sensorium due to central nervous involvement in 12.1 per cent of the patients. The chances of the patients developing complications were considerably low if treated early and very few of them developed any complications after 2 days of hospitalized treatment. The early occurrence of pulmonary complications indicates a pathogenesis totally different from that responsible for the other complications.Item Comparison and efficacy of various bacteriological techniques for the isolation of group B streptococci.(1981-01-01) Sehgal, S C; Chhibber, SItem Comparison of immunoreactive proteins of commonly circulating serogroups of Leptospira in Andaman Islands, India.(2005-03-02) Biswas, D; Roy, S; Vijayachari, P; Sugunan, A P; Natarajaseenivasan, K; Sehgal, S CBACKGROUND & OBJECTIVE: Early diagnosis is the key to the treatment of leptospirosis. For development of rapid diagnostic kits, a thorough knowledge about the nature of the proteins expressed by the pathogen during infection is necessary. The present study was undertaken to understand the nature of immunoreactive proteins from commonly circulating serogroups of Leptospira in the endemic Andaman and Nicobar Islands, India. METHODS: Proteins were extracted from six strains of Leptospira representing five different serogroups following four different preparation methods, viz., whole cell lysis by sonication, detergent solubilization, outer and inner membrane isolations, and were subsequently characterized on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblots were made from the sonicated proteins using hyperimmune rabbit antisera, homologous and heterologous patient sera separately. RESULTS: The 67, 65, 45, 43, 35, 32 and 18 kDa major proteins in the whole cell lysate were common among all the five serogroups of Leptospira. The 67, 41, 35, 32, 28 and 22 kDa were the major outer membrane proteins, while 94, 32, 25 and 18 kDa protein were in inner membrane. Immunoblots with hyperimmune rabbit antisera detected 67, 65, 60, 45, 43, 41 and 32 kDa common proteins from the whole cell lysates of all strains while homologous and heterologous patient sera detected 32 kDa as the major immunoreactive protein in all pathogenic serogroups. This protein reacted against specific LipL32 antisera indicating that this protein was LipL32. INTERPRETATION & CONCLUSION: The circulating serogroups of Leptospira have common nature of expression of proteins during human infection. Among several immunoreactive proteins, three (67, 45 and 32 kDa) were recognized as major antigens by both rabbit hyperimmune sera and patients sera while the 32 kDa protein was recognized as the major immunoreactive protein by homologous and heterologous patient sera. These conserved immunoreactive proteins could be utilized in developing indigenous diagnostic tests for leptospirosis.Item Epidemiological patterns of leptospirosis.(2006-10-23) Sehgal, S CItem Evaluation of a simple and rapid faecal concentration technique for helminthic ova and protozoal cysts.(1976-09-01) Vinayak, V K; Sehgal, S CItem Evaluation of darkground microscopy as a rapid diagnostic procedure in leptospirosis.(2001-08-12) Vijayachari, P; Sugunan, A P; Umapathi, T; Sehgal, S CBACKGROUND & OBJECTIVES: Although darkground microscopy (DGM) is the method employed for examining the growth of leptospires in culture, it is not useful for diagnosis when used directly on body fluids. However, it continues to be used as a method for diagnosing leptospirosis in many centres in India. The present study was undertaken to evaluate the diagnostic accuracy of DGM by comparing it with established tests like culture, microscopic agglutination test (MAT), IgM ELISA and Lepto-Dipstick. METHODS: A total of 170 patients clinically suspected to have leptospirosis were included in the study. The gold standard for diagnosis was positive blood culture, or seroconversion, or a four-fold rise in titre in MAT. DGM was done on plasma after centrifugation at 1000 g and 3000 g and on serum. Indices of accuracy including sensitivity, specificity, predictive values and kappa value of agreement with the gold standard diagnostic criteria were calculated. RESULTS: DGM had a sensitivity of 40.2 per cent, specificity of 61.5 per cent, a positive predictive value of 55.2 per cent and a negative predictive value of 46.6 per cent. It had agreement with the gold standard in only 50 per cent cases the kappa value being 0.017141. INTERPRETATION & CONCLUSION: DGM has low indices of accuracy. The results obtained in patients who met the gold standard criteria for diagnosis and those who did not were identical indicating that the test results are not determined by the presence of leptospiral infection in the patient. DGM, therefore, is not recommended as a sole diagnostic procedure for early diagnosis of leptospirosis.Item Evaluation of Kato thick smear technique for quantitative estimation of helminthic infections.(1978-02-01) Vinayak, V K; Sehgal, S C; Gupta, U; Chhuttani, P NItem Evaluation of Kato thick smear technique for the detection of helminthic ova in faeces.(1977-04-01) Sehgal, S C; Vinayak, V K; Gupta, UItem Evaluation of leptospira micro capsule agglutination test (MCAT) for serodiagnosis of leptospirosis.(1997-12-24) Sehgal, S C; Vijayachari, P; Subramaniam, VA micro capsule agglutination test (MCAT) was evaluated for its usefulness in the diagnosis of leptospirosis. The test was performed on 180 serum samples from 120 patients suspected to have leptospirosis and the results were compared with those obtained by microscopic agglutination test (MAT). The overall sensitivity and specificity of the test in comparison with MAT were 84.7 and 87.0 per cent respectively. Further, to study the relative merits of MCAT and MAT in diagnosing leptospirosis early in the course of the disease, its sensitivity and specificity during the early stages of the disease were compared with those of a single MAT done on acute samples in 60 patients from whom paired samples were available. The test appeared to have a higher sensitivity than MAT during the early stages of the disease (75% vs 58.3%) though the specificity was less than that of MAT (83.3% vs 100%). The sensitivity of the test declined to 61 per cent three to four weeks after the onset of illness. MCAT detected antibodies against serogroups Australis (76.9%), Autumnalis (100%) Ballum (100%), Canicola (100%), Cynopteri (100%), Grippotyphosa (71.8%), Icterohaemorrhagiae (93.3%), Javanica (100%), Pomona (75%) and Pyrogenes (100%). MCAT appears to be a useful screening test for early diagnosis of leptospirosis. It is a simple and easy to read test which does not require any special expertise or equipment.Item Evaluation of microscopic agglutination test as a diagnostic tool during acute stage of leptospirosis in high & low endemic areas.(2001-09-05) Vijayachari, P; Sugunan, A P; Sehgal, S CBACKGROUND & OBJECTIVES: Making a diagnosis on the results of a single microscopic agglutination test (MAT) is difficult because of the uncertainties about the cut-off titre. The present study was conducted to determine the significant titre for a single MAT in areas of high and low endemicity for leptospirosis. METHODS: A total of 1944 serum samples were collected from healthy individuals and confirmed patients residing in areas of high and low endemicity. All the sera were screened by MAT using 10 live leptospiral strains as antigens. From the distribution of titres among healthy individuals and in patients, the sensitivity and specificity at different cut-off titres were calculated. Likelihood ratio positive (LR+), likelihood ratio negative (LR-), and LR+/LR- were calculated. Receiver operating characteristics (ROC) curves were plotted for the early and late stages of the disease in both the areas. RESULTS: The ROC plot was totally below the no benefit line during the first week of illness in high endemic area. During the second to fourth weeks it showed better characteristics and the best cut-off titre was 1:200, where the sensitivity was 93.4 per cent and specificity 74.7 per cent LR+ LR- ratio was 41.82 indicating reasonable separation between the positive and negative test results. In the other states the ROC plot was above the no benefit line even during the first week, the best cut-off being 1:50 where the sensitivity was 56.7 per cent and specificity was 90.6 per cent. During the second to fourth weeks the test showed the best characteristics in the low endemicity regions with an ROC curve having the ideal shape. Best cut-off was at 1:100 where the sensitivity was 96.6 per cent and specificity 94.8 per cent LR+ LR- ratio was 523.25 indicating a wide separation between the positive and negative test results. INTERPRETATION & CONCLUSION: MAT does not have any diagnostic value during the first week, particularly in high endemic areas. The best cut-off to be used will be 1:50 in low endemicity areas during the first week, 1:100 during the second to fourth week and 1:200 in high endemicity regions during the second to fourth weeks.Item Existing status of shigellosis in Andaman & Nicobar islands.(1996-03-01) Ghosh, A R; Sehgal, S CA total of 691 children below five years of age, who were suffering from acute diarrhoea, were investigated. Conventional bacterial pathogens were isolated in 133 (19.2%) cases. Shigella sp. was the most common isolate being positive in 72 (10.4%) faecal specimens. No isolation of Shigella sp. was observed in paediatric patients less than 6 months of age while the maximum isolations were observed among 7-12 month old children. All isolates were sensitive to ciprofloxacin, norfloxacin, gentamycin and nalidixic acid and resistant to ampicillin. Multiple drug resistant isolates were observed during the study also. In all, 7 antibiograms were observed.Item Gel filtration pattern of axenic Entamoeba histolytica and characterization of immunological specificities of various fractions.(1982-01-01) Sehgal, S C; Gupta, S; Chhibber, S; Vadehra, D VItem Haemolysin production by environmental isolates of Vibrio parahaemolyticus from Andamans.(1998-04-30) Ghosh, A R; Sehgal, S CSixty marine water samples were collected from various coastal sites around Port Blair at different times during August 1996 to July 1997. The specimens were subjected to standard procedure for isolation and identification of V. parahaemolyticus. Forty four V. parahaemolyticus isolates were detected from these specimens and all showed clear haemolysis on Wagatsuma agar plates. The haemolytic activity was abolished by heating the culture supernatants at 60 degrees C for 10 min and enhanced when plates were kept at 4 degrees C. When isolates were subjected to PCR assay for tdh gene, only one showed the presence of the gene. The results indicate the existence of pathogenic V. parahaemolyticus in the marine environment of these islands.Item Intestinal parasitic infestation among different population groups of Andaman and Nicobar islands.(1996-12-01) Sugunan, A P; Murhekar, M V; Sehgal, S CA survey was carried out among the rural and urban settlers and two tribal groups viz. Nicobarese and Onges, of Andaman and Nicobar islands. The survey covered preschool school aged children and adults. Out of the total 1,384 stool samples examined, 652 (47.1%) showed ova or cysts of one or more intestinal parasites. Among the preschool children, Nicobarese showed the highest overall prevalence rate (80.5%) followed by urban (46.7%) and rural (38.6%) preschool children. Ascaris lumbricoides was the commonest form of parasite encountered in all the groups of preschool children, followed by Trichuris trichura. While ascariasis and trichuriasis were more common among the urban children than in rural children, giardiasis was more common among the rural preschool children. The school age children among rural settlers showed an overall prevalence rate of 61.1% which was significantly higher than that among the rural preschool children. Among the school age children also, ascariasis was the commonest form of parasitosis followed by trichuriasis. The Nicobarese and Onge adults showed significantly higher overall prevalence rates (72.2%) and 71.1% vs 48.6%) compared to rural adults. In all the groups studied ascariasis was the commonest form of parasitosis except in Onges among whom trichuriasis and giardiasis were more common than ascariasis. Change in prevalence rates over age was studied among the rural settlers. While ascariasis and trichuriasis showed peak prevalence rates in school age children prevalence of giardiasis declined with increase in age from a peak in the preschool age group and prevalence rates of hook worm infestation continued increasing beyond school age.Item Lai-like leptospira from the Andaman Islands.(2000-10-14) Sehgal, S C; Vijayachari, P; Smythe, L D; Norris, M; Symonds, M; Dohnt, M; Korver, H; v d Kemp, H; Hartskeerl, R A; Terpstra, W JBACKGROUND & OBJECTIVES: Leptospirosis has been an important public health problem in the Andaman Islands since 1988. As information about the exact etiological agent is not available, the present study was undertaken to isolate and identify Leptospira from human patients. METHODS: An isolate coded AF61 was recovered from the blood of a patient clinically suspected to have leptospirosis, with fever, headache and body aches as the main symptoms. The isolation was done using Ellinghausen-McCullough-Johnson-Harris (EMJH) medium following standard procedure. The isolate was identified using microscopic agglutination test (MAT) with 'groupsera', cross agglutination absorption test (CAAT) and monoclonal antibodies. RESULTS: Agglutination tests with rabbit antisera revealed that the isolate belonged to the serogroup icterohaemorrhagiae. The CAAT results showed that it was closely related to the serovar lai. Analysis of AF61 with monoclonal antibodies confirms our observation with CAAT that it is closely related to the reference strain Lai serovar lai. INTERPRETATION & CONCLUSIONS: Serovar lai, has been associated with pulmonary haemorrhage in China and Korea. However, the strain AF61 was not isolated from a patient with pulmonary symptoms. Further studies are needed to understand the possible relationship between serovars and clinical patterns and the distribution of serovar lai and lai-like strains in Asia.Item Leptospiral proteins expressed during acute & convalescent phases of human leptospirosis.(2004-09-19) Natarajaseenivasan, K; Vijayachari, P; Sugunan, A P; Sharma, S; Sehgal, S CBACKGROUND & OBJECTIVES: The available serological techniques for the diagnosis of leptospirosis have less sensitivity during the early stage of the disease. Understanding of leptospiral proteins expressed during acute and convalescent phases of leptospirosis, would be help the develop of new serodiagnostic strategies. Therefore, the present study was carried out to identify (i) an antigen that is conserved among the various pathogenic leptospira; (ii) best protein antigen to which immune response can be identified in the acute phase; and (iii) best protein antigen which is present in convalescent sera which can be used for seroepidemiological studies. METHODS: Quantitative immunoblot analysis was performed using acute and convalescent phase human sera along with sera from normal healthy individuals and from patients with typhoid, malaria and hepatitis as the controls. All the samples were analyzed for the leptospiral protein recognition by using IgM and IgG immunoblots. Leptospiral cell fractionation was performed using triton X-114 and lysozyme and further the conservation of leptospiral proteins was also performed. RESULTS: In confirmed cases of leptospirosis, the IgG recognition in acute phase sera was 30.2, 39.5, 27.9, 55.8 and 27.9 per cent for the leptospiral proteins p32, p41/42, p58, p62 and p82 respectively. The IgG has considerably increased to 65.1, 55.8, 46.5, 67.4 and 48.8 per cent against the same proteins during convalescent phase. The IgM recognition was 32.6 , 32.6, 30.2 and 37.2 per cent for acute phase sera and 32.6, 37.2, 44.2 and 41.9 per cent for convalescent phase sera for the leptospiral proteins p14, p25, p32 and p41/42, respectively. Leptospiral proteins like p62 and p82 were recognized among all the control groups with 3.3-15.3 per cent for IgG recognition. INTERPRETATION & CONCLUSION: Leptospiral protein p32 was found to be highly sensitive and specific and could be useful for the development of newer techniques for diagnosis and seroepidemiological studies. Combination of p32 and p41/42 for IgG and p14, p25, p32, p41/42 for IgM would increase the sensitivity of these techniques further.Item Leptospirosis disease burden estimation and surveillance networking in India.(2003-09-25) Sehgal, S C; Sugunan, A P; Vijayachari, PAlthough leptospirosis is known to have occurred in India since the early years of the 20th century, no accurate data on disease burden exist. During the past two decades, leptospirosis cases have been reported with increasing frequency from different parts of the country. Several large outbreaks have occurred. In the year 2000, the Indian Council of Medical Research set up a Task Force on Leptospirosis. The Task Force conducted a multicentric study on disease burden due to leptospirosis. As part of the study, 3,682 patients with acute febrile illness, from 13 different centers in India, were investigated for the presence of current leptospiral infection using the Lepto-dipstick test. Of these patients, 469 (12.7%) were found to have leptospiral infection. The positivity rate ranged from 3.27% in the central zone to 28.16% in the southern zone. Fever, body aches and chills were the common symptoms observed. Urinary abnormalities, such as oliguria, yellow discoloration of urine and hematuria were found in 20%-40% of patients. Distribution of serogroups was studied based on microscopic agglutination test (MAT) titers. The southern zone had all the eleven serogroups in the panel, the eastern zone had nine, the northern zone eight, and the central and western zones had five circulating serogroups each. Among various risk factors studied, rat infestation of houses had the strongest association with leptospiral infection. Many other factors related to the environment, personal and occupational habits, etc, also had significant associations. The study had a few drawbacks. The Task Force has decided to continue the study with modified protocols to generate more accurate and detailed information about disease burden.Item Leptospirosis on the horizon.(2000-09-24) Sehgal, S C