Tropical Microbiology

Pollution and increased levels of heavy metals in the Lake Victoria Wetlands are suspected to be negatively influencing the biota in one of the world most important freshwater resources. In this study, fecal contamination of water in the Lake Victoria wetlands was investigated using the standard coliform test. Gram-negative bacteria were isolated by plating on Mackonkey's and EMB media. Isolates were characterized, and their ability to grow in the presence of heavy metals tested. Isolates were also tested for resistance to commonly used antibiotics. The study was conducted both in the dry and wet seasons. Fecal contamination was detected in all tested water samples, as evidenced by the isolation of Escherichia coli both in the wet and dry seasons. Coliform counts of above 1100 MPN/100 ml were detected. Ninety-five and forty-five gram-negative bacterial isolates were obtained in the dry season and wet seasons, respectively. Isolates from the dry season were resistant to nalidixic acid (66%), ampicillin (54%), and tetracycline(28%). They were however largely sensitive to gentamycin (95%) and streptomycin (98%); 41.1% percent of the isolates showed multi-drug resistance. A similar antibiotic resistance pattern was detected in the wet season, and 31.1% of the isolates were multi-drug resistant. Many of the isolates were resistant to Zinc and Copper (final conc. 1.6g/l each), but largely sensitive to mercury (0.05 g/l; 52%) and lead (2 g/l; 89%). Although, tolerance to heavy metals is usually associated with plasmids, which also encode resistance to antibiotics, a direct correlation between antibiotic resistance and heavy metal tolerance by the isolates obtained in this study cannot be established. Further work needs to be conducted to establish the molecular basis of resistance. Constant monitoring of antibiotic resistance levels in bacteria from Lake Victoria wetlands is essential, considering the prevalence of water borne diseases in the area.

Background: Diarrheagenic Escherichia coli are associated with infantile diarrhea in the developing countries. The present study was conducted to determine the occurrence and antimicrobial resistance pattern of enteropathogenic and enteroinvasive E. coli associated with diarrhoea among the paediatric patients. Methods: A total of 262 stool samples were collected from children with and without diarrhea from Mizoram, Northeast India. E. coli were isolated and subjected to multiplex PCR to detect virulent genes of EPEC (eaeA and bfpA) and EIEC (ial). Isolates were subjected to antimicrobial sensitivity assay using disc diffusion method. Selected eaeA genes were sequenced for identification and genetic relationship. Results: A total of 334 E. coli was isolated, of which 17.37% were carrying at least one virulent gene. Altogether, 14.97 and 2.40% isolates were categorized as EPEC and EIEC, respectively. Among the DEC isolates, 4.79% were EPEC and 7.78% were EIEC. A total of 8 (2.40%) isolates were EIEC (ial+), of which 6 (1.80%) and 2 (0.60%) were from diarrhoeic and non-diarrhoeic patients, respectively. A total of 24 (41.40%) DEC isolates were MDR (resistance against ≥5 antimicrobials). Conclusions: A high frequency of EPEC pathotypes associated with paediatric diarrhea was observed in Mizoram, Northeast India and majority of the isolates are resistant to antibiotics with a high frequency of MDR, which is a matter of concern to the public health. This also raises an alarm to the world communities to monitor the resistance pattern and analyse in a global scale to combat the problems of resistance development.

Systematic management of oil palm-cattle integration considers as one of the best alternative solutions to meet the need of increasing local beef and dairy. The change in oil palm plantation management systems can influence the soil microbial community. Microbes mediate many key processes in soils and are essential in driving ecosystem stability and sustainability of oil palm production. The research aimed to investigate the influence of grazing in an oil palm plantation on the bacteria involved in the soil nitrogen cycle. We evaluated the abundance of diazotrophic, nitrifying, and denitrifying bacteria in the grazing and ungrazing area of oil palm plantations. Grazing area subject to 11 and 10 times cattle grazing rotation with the two-month interval between rotation were studied. The enumeration of bacteria was evaluated using the Most Probable Number (MPN) technique. Generally, diazotrophic bacteria, nitrifier, and denitrifier were higher in the grazing area compare to ungrazing area. However, the difference between that two grazing-plantation management is not significant (P>0.05). In summary, our results show that an addition of organic materials from the dung of cattle in the grazing area of oil palm plantation influences the soil microbial community including N-transforming bacteria

Pollution and increased levels of heavy metals in the Lake Victoria Wetlands are suspected to be negatively influencing the biota in one of the world most important freshwater resources. In this study, fecal contamination of water in the Lake Victoria wetlands was investigated using the standard coliform test. Gram-negative bacteria were isolated by plating on Mackonkey's and EMB media. Isolates were characterized, and their ability to grow in the presence of heavy metals tested. Isolates were also tested for resistance to commonly used antibiotics. The study was conducted both in the dry and wet seasons. Fecal contamination was detected in all tested water samples, as evidenced by the isolation of Escherichia coli both in the wet and dry seasons. Coliform counts of above 1100 MPN/100 ml were detected. Ninety-five and forty-five gram-negative bacterial isolates were obtained in the dry season and wet seasons, respectively. Isolates from the dry season were resistant to nalidixic acid (66%), ampicillin (54%), and tetracycline(28%). They were however largely sensitive to gentamycin (95%) and streptomycin (98%); 41.1% percent of the isolates showed multi-drug resistance. A similar antibiotic resistance pattern was detected in the wet season, and 31.1% of the isolates were multi-drug resistant. Many of the isolates were resistant to Zinc and Copper (final conc. 1.6g/l each), but largely sensitive to mercury (0.05 g/l; 52%) and lead (2 g/l; 89%). Although, tolerance to heavy metals is usually associated with plasmids, which also encode resistance to antibiotics, a direct correlation between antibiotic resistance and heavy metal tolerance by the isolates obtained in this study cannot be established. Further work needs to be conducted to establish the molecular basis of resistance. Constant monitoring of antibiotic resistance levels in bacteria from Lake Victoria wetlands is essential, considering the prevalence of water borne diseases in the area.

Pollution and increased levels of heavy metals in the Lake Victoria Wetlands are suspected to be negatively influencing the biota in one of the world most important freshwater resources. In this study, fecal contamination of water in the Lake Victoria wetlands was investigated using the standard coliform test. Gram-negative bacteria were isolated by plating on Mackonkey's and EMB media. Isolates were characterized, and their ability to grow in the presence of heavy metals tested. Isolates were also tested for resistance to commonly used antibiotics. The study was conducted both in the dry and wet seasons. Fecal contamination was detected in all tested water samples, as evidenced by the isolation of Escherichia coli both in the wet and dry seasons. Coliform counts of above 1100 MPN/100 ml were detected. Ninety-five and forty-five gram-negative bacterial isolates were obtained in the dry season and wet seasons, respectively. Isolates from the dry season were resistant to nalidixic acid (66%), ampicillin (54%), and tetracycline(28%). They were however largely sensitive to gentamycin (95%) and streptomycin (98%); 41.1% percent of the isolates showed multi-drug resistance. A similar antibiotic resistance pattern was detected in the wet season, and 31.1% of the isolates were multi-drug resistant. Many of the isolates were resistant to Zinc and Copper (final conc. 1.6g/l each), but largely sensitive to mercury (0.05 g/l; 52%) and lead (2 g/l; 89%). Although, tolerance to heavy metals is usually associated with plasmids, which also encode resistance to antibiotics, a direct correlation between antibiotic resistance and heavy metal tolerance by the isolates obtained in this study cannot be established. Further work needs to be conducted to establish the molecular basis of resistance. Constant monitoring of antibiotic resistance levels in bacteria from Lake Victoria wetlands is essential, considering the prevalence of water borne diseases in the area.

Pollution and increased levels of heavy metals in the Lake Victoria Wetlands are suspected to be negatively influencing the biota in one of the world most important freshwater resources. In this study, fecal contamination of water in the Lake Victoria wetlands was investigated using the standard coliform test. Gram-negative bacteria were isolated by plating on Mackonkey's and EMB media. Isolates were characterized, and their ability to grow in the presence of heavy metals tested. Isolates were also tested for resistance to commonly used antibiotics. The study was conducted both in the dry and wet seasons. Fecal contamination was detected in all tested water samples, as evidenced by the isolation of Escherichia coli both in the wet and dry seasons. Coliform counts of above 1100 MPN/100 ml were detected. Ninety-five and forty-five gram-negative bacterial isolates were obtained in the dry season and wet seasons, respectively. Isolates from the dry season were resistant to nalidixic acid (66%), ampicillin (54%), and tetracycline(28%). They were however largely sensitive to gentamycin (95%) and streptomycin (98%); 41.1% percent of the isolates showed multi-drug resistance. A similar antibiotic resistance pattern was detected in the wet season, and 31.1% of the isolates were multi-drug resistant. Many of the isolates were resistant to Zinc and Copper (final conc. 1.6g/l each), but largely sensitive to mercury (0.05 g/l; 52%) and lead (2 g/l; 89%). Although, tolerance to heavy metals is usually associated with plasmids, which also encode resistance to antibiotics, a direct correlation between antibiotic resistance and heavy metal tolerance by the isolates obtained in this study cannot be established. Further work needs to be conducted to establish the molecular basis of resistance. Constant monitoring of antibiotic resistance levels in bacteria from Lake Victoria wetlands is essential, considering the prevalence of water borne diseases in the area.

Systematic management of oil palm-cattle integration considers as one of the best alternative solutions to meet the need of increasing local beef and dairy. The change in oil palm plantation management systems can influence the soil microbial community. Microbes mediate many key processes in soils and are essential in driving ecosystem stability and sustainability of oil palm production. The research aimed to investigate the influence of grazing in an oil palm plantation on the bacteria involved in the soil nitrogen cycle. We evaluated the abundance of diazotrophic, nitrifying, and denitrifying bacteria in the grazing and ungrazing area of oil palm plantations. Grazing area subject to 11 and 10 times cattle grazing rotation with the two-month interval between rotation were studied. The enumeration of bacteria was evaluated using the Most Probable Number (MPN) technique. Generally, diazotrophic bacteria, nitrifier, and denitrifier were higher in the grazing area compare to ungrazing area. However, the difference between that two grazing-plantation management is not significant (P>0.05). In summary, our results show that an addition of organic materials from the dung of cattle in the grazing area of oil palm plantation influences the soil microbial community including N-transforming bacteria

The quantitative assessment of the roles of fungi and bacteria in nitrogen (N) transformation in virgin and cultivated soils was done. Measurements of biomass of bacteria and fungi, selective inhibition of their activities in the soils and comparisons of activities of inoculated fungal and bacterial strains in sterile soils with rates of N processes in native soils were performed in laboratory experiments. Fungi were responsible for most of ammonification (80%) of ready available N compounds (peptone) added to the forest soddy-podzolic soil. In the arable soil bacteria and fungi had an equal contribution to the mineralization of peptone to NH4. Heterotrophic nitrification (mainly fungal) was higher in virgin soils than in cultivated soils of the same types. Contribution of heterotroph microorgamisms in nitrate production was highest in the soil under mature spruce (about 90%); it was much less (10-40%) in the soils of other natural ecosystem (leaf forests, grasslands). Autotrophic b...

The knowledge of the behavior of the nitrifying microorganisms is of real use, because the microbial activities related to the nitrogen circuit and especially the nitrification determine the results of the agronomic practices. In this paper, the influence of the Lotus corniculatus L. (IIV culture years) on the nitrifying bacteria and the correlation between the growth of these bacteria and soil moisture was studied.The soil samples were taken during the flowering period (summer season), from the rhizosphere of the pottery, but also from the uncultivated plots (control), placed in the western part of the country. Studies have shown that plants and soil moisture have influenced the evolution of nitrifying bacteria.

The knowledge of the behavior of the nitrifying microorganisms is of real use, because the microbial activities related to the nitrogen circuit and especially the nitrification determine the results of the agronomic practices. In this paper, the influence of the Lotus corniculatus L. (IIV culture years) on the nitrifying bacteria and the correlation between the growth of these bacteria and soil moisture was studied.The soil samples were taken during the flowering period (summer season), from the rhizosphere of the pottery, but also from the uncultivated plots (control), placed in the western part of the country. Studies have shown that plants and soil moisture have influenced the evolution of nitrifying bacteria.

The effects of phenmedipham, propham, carbetamide, lenacil and benzthiazuron on soil nitrification was studied in the laboratory using a perfusion technique. The nitrification process was markedly retarded at a phenmedipham concentration of 50-5OOpg g-' soil, so that 55-150 days were required for complete oxidation of supplied NH:-N as compared with 33 days for the untreated control. Phenmedipham caused a reduction in both the maximum population and the proliferation rate of nitrifying organisms, as evaluated from kinetic parameters. These inhibitory effects showed a low persistance probably due to herbicide breakdown. The effects of 100 pg g-' soil of propham, carbetamide, lenacil or benzthiazuron on the nit&cation process was very weak, although the kinetics of the nitrification process was affected by all these herbicides.

The number of nitrifiers (NH4 - oxidizers and NO2 -oxidizers), total heterotrophs, amount of ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) were determined in a Red Yellow Podzolic soil with gravels (pH 4.2), under a coconut-pasture association in Sri Lanka to understand the distribution of inorganic nitrogen in coconut-growing soils and to study the effect of pasture on nitrification.

The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangladesh in monsoon tropical climate. Clear felled area or burnt site and 15−21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly (p≤0.001) lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as denitrifying bacteria compared to their adjacent mixed plantation. From environmental consideration, this finding has implication in managing natural ecosystem.