Aldehyde test (Formol-Gel test) in the diagnosis of kala-azar (visceral leishmaniasis).
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Aldehydes↗
Biomedical subjects
M A Chowdhury
Publications and source records attributed to M A Chowdhury.
Ecology and distribution of toxigenic Vibrio cholerae in aquatic environments of a temperate region.
The occurrence of a human pathogen, Vibrio cholerae, in aquatic environments and the distribution of toxigenic strains were studied for 2 years. The pathogen was isolated from freshwater, brackish and marine environments. V. cholerae non-01 was frequently recovered but the 01 serogroup was not detected. Of the 57 environmental strains tested, eight (12%) were found to be potentially toxigenic. A number of atypical V. cholerae 01 strains were found which showed higher virulence potentials than the serogroup non-01 strains. A significant correlation of the incidence of the pathogen was noted with water temperature in freshwater environments. In marine environments, a reciprocal correlation of the V. cholerae count and salinity was observed. The present study describes the ecology of V. cholerae in aquatic environments of a temperate region and notes that the occurrence of potentially virulent strains could be of public health significance.
Cholera Toxin↗
Vascular permeability enhancement by Vibrio mimicus protease and the mechanisms of action.
Vibrio mimicus, a causative agent of gastroenteritis, has also been reported to attribute to extraintestinal infections. Recently we have purified a metalloprotease produced by the pathogen: however, the role of the protease in V. mimicus infection has not been documented. The V. mimicus protease (VMP) was found to enhance vascular permeability and form edema when injected into the dorsal skin of guinea pig and rat. The permeability enhancement by VMP was observed in a dose-dependent manner in both guinea pig and rat skin. In guinea pig, an inhibitor of the angiotensin-converting enzyme was found to augment the permeability enhancement reaction. The permeability enhancement was significantly blocked by soybean trypsin inhibitor (SBTI), an inhibitor of plasma kallikrein reaction. In vitro conversion of plasma prekallikrein to kallikrein by VMP was also noted. In rat skin, the permeability enhancement reaction was not blocked by antihistamine or SBTI. However, the reaction was partially blocked when a mixture of antihistamine and SBTI was administered with VMP. It is apparent from the study that in guinea pig skin, VMP enhances vascular permeability through activation of plasma kallikrein-kinin system which generates bradykinin, whereas in addition to the activation of plasma kallikrein-kinin cascade in the case of rat, stimulation of histamine release from mast cells and other unknown mechanism seem to be also a cause of the permeability enhancement reaction. These results suggest that VMP may play a role in extraintestinal infections with edema caused by the pathogen.
Angiotensin-Converting Enzyme Inhibitors↗
Further study on polyamine compositions in Vibrionaceae.
It has previously been reported that norspermidine, one of the unusual polyamines, is present in Vibrio species. To expand this observation, the cellular polyamine compositions of additional species and strains in the family Vibrionaceae (Vibrio, Photobacterium, Listonella, and Shewanella) as well as Aeromonas species and Plesiomonas shigelloides, which have been proposed to be excluded from Vibrionacea, were determined by using gas-liquid chromatography. Some Vibrio species previously reported were reexamined under the same conditions, and their results are included in this report. Norspermidine was detected as a major triamine in 23 of 24 Vibrio species, all of 4 Listonella species, and 3 of 5 Photobacterium species. Vibrio costicola, Photobacterium fischeri, and Photobacterium phosphoreum contained no norspermidine. Listonella species were indistinguishable from Vibrio species in their polyamine profiles. However, Schewanella putrefaciens ATCC 8071, formerly allocated in the genus Alteromonas, contained no norspermidine, and its polyamine profile was similar to those of four Aeromonas species, in which putrescine was exclusively found. Plesiomonas shigelloides was very similar to Escherichia coli in that putrescine and spermidine were predominant polyamines. Our data indicate that the occurrence of norspermidine may be very helpful as a generic marker in identification and classification of Vibrio and Listonella species. A gas-liquid chromatographic method with a nitrogen-selective detector was presented for rapid and sensitive detection of cellular norspermidine.
Chromatography, Gas↗
Optimal growth temperature for the isolation of Plesiomonas shigelloides, using various selective and differential agars.
The growth characteristics of known strains of Plesiomonas shigelloides were compared with those of Aeromonas species (the major competing species in environmental waters) on plesiomonas differential agar, inositol brilliant green bile salt, and modified salmonella-shigella agar at incubation temperatures of 37, 42, and 44 degrees C. Using local isolates from clinical and environmental sources, optimal growth conditions, as determined by colony counts and the colony characteristics, plesiomonas differential agar proved to be ideal when incubated at 44 degrees C. Contrary to earlier recommendations for 48 h incubation, the colonies could be recognized readily after an incubation of 24 h.
Agar↗
Role of Vibrio mimicus protease in enterotoxigenicity.
Recently, we have purified and characterised a metalloprotease produced by Vibrio mimicus. The role of V. mimicus protease (VMP) in fluid accumulation (FA) in rabbit ileal loops (RIL) was investigated. Although live cells or crude VMP prepared from cell-free culture supernatant showed activity in RIL, the purified VMP failed to induce FA in the RIL. When VMP in crude preparation was inactivated by preparing the fraction in the presence of EGTA (Ethyleneglycol-bis [beta-aminoethylether]-N, N, N1, N1,-tetraacetic acid), a chelating agent for Ca2+ (EGTA-crude), or treatment with phosphoramidon (a metalloprotease inhibitor), the preparation became negative in RIL assay. Again, the EGTA-crude induced FA in RIL when retreated with 2mM CaCl2 after elimination of EGTA. The results show evidences of attribution of VMP in RIL activity. These observations, therefore, suggest that the protease produced by V. mimicus may play a potential role in enterotoxigenicity.
Animals↗
Detection of Vibrio cholerae O1 in the aquatic environment by fluorescent-monoclonal antibody and culture methods.
Vibrio cholerae O1 in plankton samples collected from ponds and rivers between February 1987 and January 1990 in Matlab, Bangladesh, was detected by the fluorescent-monoclonal antibody (FA) technique. Samples were collected at sites which were monitored fortnightly (fixed sites) as well as at sites that were part of a case-control study. FA results were compared with those obtained by conventional culture methods (CM). A total of 876 samples were collected; V. cholerae O1 was detected in 563 samples (64.27%) by the FA method and in 3 samples (0.34%) by CM. Of the fixed-site plankton samples, 439 (63.62%) were positive by FA and none were positive by CM. Of the 93 case sites sampled on the day after the occurrence of a case of cholera, 73 (78.49%) were positive for V. cholerae O1 by FA and 3 (3.2%) were positive by CM. In comparison, of the 93 first-day sample collections at control sites at the time a case of cholera occurred, only 51 (54.83%) were positive by FA and none were positive by CM. From the data, it is concluded that V. cholerae O1 is present throughout the year in the ponds and rivers of Bangladesh that were examined in this study and that V. cholerae can be detected by FA but not always by CM. The FA procedure was found to be very useful in detecting V. cholerae in plankton, with which it was associated and often occurred in large numbers in the nonculturable stage. Thus, studies investigating the significance of the role of environmental factors in the epidemiology of cholera can be performed effectively by using FA. Such studies are in progress.
Animals↗
Purification and characterization of a protease produced by Vibrio mimicus.
A protease produced by Vibrio mimicus was purified to apparent homogeneity by ammonium sulfate fractionation and successive column chromatography on Sephacryl S-100 and Mono Q Monobeads. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) of the final preparation of the enzyme revealed the homogeneity of the purified enzyme. Conventional PAGE showed that the purified protease migrated as a single band with protease activity. The molecular weight of the protease was estimated to be about 31,000 on the basis of its mobility on sodium dodecyl sulfate-PAGE. The purified protease had both proteolytic and hemagglutination (HA) activities. The proteolytic and HA activities were inhibited by metalloprotease inhibitors and heat treatment. V. mimicus protease therefore appeared as a heat-labile, bifunctional molecule capable of mediating proteolysis and HA. The immunodiffusion analysis showed that the proteases produced by Vibrio cholerae and V. mimicus are immunologically cross-reactive.
Amino Acids↗
Ecology of mesophilic Aeromonas spp. in aquatic environments of a temperate region and relationship with some biotic and abiotic environmental parameters.
The Ecology of mesophilic Aeromonas species has been investigated since January 1988 to examine their occurrence and distribution in aquatic environments of Okayama Prefecture. Water and plankton samples were quantitatively as well as qualitatively analyzed throughout the seasons from five selected stations including fresh, brackish, and saline environments. Analysis of variance and correlation coefficients among the biotic and abiotic parameters were sought. The organisms were found in all the environs with high densities through all the seasons. Plankton samples yielded higher counts of Aeromonas than the water samples in all the environs. Water temperature seemed to play a significant role on their growth during the winter months, however, no significant seasonal variation nor any correlation with fecal pollution were observed in most of the environments. A reciprocal relationship was seen with salt concentration in the saline environment. Among the currently recognized mesophilic species; A. caviae, A. hydrophila, A. sobria, and A. media were isolated with the predominance of anaerobic biovar. The present study reveals that Aeromonas are widely distributed in fresh, brackish and saline environments of this region. The study also reveals that Aeromonas are autochthonous members in aquatic ecosystems and are indigenous to these environs. Aeromonas species isolated from our environments were found to exhibit drug resistance potential which differed from that of isolates from diverse geographical locales. The high incidence of clinically significant Aeromonas species in this aquatic region could be of public health significance for the inhabitants of this region, as well as a challenge to their dependence on aquatic resources.
Aeromonas↗
Ecology of Vibrio mimicus in aquatic environments.
An environmental study was done to examine the prevalence of Vibrio mimicus in some aquatic environments of Dhaka, Bangladesh, and of Okayama, Japan. Water samples from Dhaka environments and water and plankton samples from Okayama environments were quantitatively as well as qualitatively analyzed throughout the seasons for V. mimicus. The organism was isolated from Bangladesh environments throughout the year, whereas it was not isolated in Okayama when the water temperature fell below 10 degrees C. Samples with as many as 9.0 x 10(2) CFU of V. mimicus per 100 ml of water in Dhaka and 1.5 x 10(4) CFU of V. mimicus per 100 ml of water in Okayama were detected during the study period. V. mimicus was not found in any environment with an average salinity of 10% or more. Brackish environments with an average salinity of 4% were observed to be the optimal natural condition for the pathogen. Using the API 20E system with the conventional test methods, we observed variations in biochemical properties within the V. mimicus species. This study reveals the inefficacy of the API 20E system to identify a significant percentage of V. mimicus. Therefore, in addition to the API 20E system, a salt tolerance test and a string test are recommended for identification of this species. Susceptibility testing of strains isolated from Okayama environments showed higher resistance to ampicillin and susceptibility to trimethoprim-sulfamethoxazole when compared with environmental isolates of V. mimicus from Bangladesh.
Bangladesh↗
Toxin production by Vibrio mimicus strains isolated from human and environmental sources in Bangladesh.
Vibrio mimicus has recently been isolated from aquatic environments of Bangladesh. A total of 125 of 300 environmental isolates, representing various biotypes, and 19 human isolates were tested for enteropathogenicity by using several models. Less than 1% of the environmental isolates and slightly more than 10% of the clinical isolates produced cholera toxin-like toxin. A significant percentage of the environmental isolates (25%) and of the human isolates (74%) induced fluid accumulation in ligated rabbit ileal loops. One environmental strain produced heat-stable toxin-like enterotoxin, whereas all of the human isolates did not. V. mimicus strains were divided into the following three groups on the basis of their activity in various toxin assays: (i) organisms which produce a heat-labile enterotoxin immunobiologically similar to cholera toxin, (ii) organisms which produce a heat-stable enterotoxin-like toxin, and (iii) organisms whose whole-cell cultures have some activity characteristic of heat-labile toxin (e.g., fluid accumulation in ligated rabbit ileal loops and positive permeability factor) but are not positive by the GM1 enzyme-linked immunosorbent assay. One isolate from this group was able to elicit these results with cell-free culture filtrates. There was no correlation of biotype with toxic activity of V. mimicus isolates.
Animals↗
Antibiotic resistance patterns of Vibrio mimicus isolated from human and environmental sources in Bangladesh.
Twenty-five environmental and 19 clinical strains of Vibrio mimicus were tested for antibiotic susceptibility patterns. Environmental strains were resistant to streptomycin, kanamycin, and trimethoprim-sulfamethoxazole; clinical strains were susceptible. Environmental strains showed variable resistance to ampicillin (44%), but clinical strains were susceptible. All strains tested were susceptible to chloramphenicol and gentamicin.
Drug Resistance, Microbial↗
Toxigenicity and drug sensitivity of Vibrio mimicus isolated from fresh water prawns in Bangladesh.
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Animals↗