Microbiology

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A preliminary study of anti-bacterial effect of selected five Ayurvedic compound preparations.
(2006) Nageeb, B.M.; Widanapathirana, S.; Amarasinghe, A.P.G.
Plant based medicaments have been man?s prime therapeutic weapons to rescue him from disease. Plants are of relevance to pharmacology. Pharmacological properties of medicinal plants may be used as leads in developing modern therapeutic agents. Thalisadee, Thripala,Hinguastaka, Dathree, and Manibadra are common Ayurvedic formulae used in traditional system of medicine in Sri Lanka. Thalisadee and Thripala Choorna are being commonly used in respiratory disorders such as cough, cold bronchitis and fever. The Hinguastaka, Dathree and Manibadra Choorna are being commonly used in gastrointestinal disorders such as diarrhoea dysentery vomiting and indigestion. Most of these conditions may develop due to bacterial infections .The main objective of this study was to evaluate the antibacterial effect of these preparations. Minimum human single dose of these drugs (2.5 gram) was dissolved in sterile distilled water and kept in the shaker at 100 rpm continuously for 04 hours in order to get the maximum soluble liquid extract of these drugs. 0.7 gram of Nutrient broth was dissolved in 50 ml of distilled water and transferred in to five test tubes (10 ml. /tube) and sterilized by autoclaving at 121 C for 20 minuets. These Nutrient broth tubes were inoculated by using inoculating needle with already plated pure test cultures of Pseudomonas aeruginosa, ,Escherichia coli , Salmonella typhi.These tubes were incubated at 37 0 C for 18 to 20 hours. Sterilized Nutrient agar was transferred into ten sterilized Petri dishes at 40 0C and allowed to solidify on a horizontal plane. These plates were sealed and kept in incubator at 37 0C for 24 hours to exclude any contaminations and to reduce the moisture content. A known amount of (0.05 ml) each culture broth containing specific organisms was added to these solidified agar plates and spread evenly using a sterilized glass spreader. On these seeded agar plates sterilized metal cylinders were kept (03 Cylinders/plate) with gentle pressure. These cylinders were filled with 0.1 ml of above liquid extract of drug preparations.De ionized sterilized distilled water 0.1 ml and Chlorampenicol 0.025 mg/0.1 ml were used as controls. These plates were sealed and incubated at 37 0C .This same procedure was repeated for three times for each of the test organism. Chlorampenicol showed 1.0 cm -1.5 cm clear inhibition zones of the bacterial lawns on every test organisms. None of the drug preparations showed any effect on Escherichia coli culture plates. The Ayurvedic compound preparations of Hinguastaka Choorna and Manibadra Choorna extracts showed averagely 0.5cm and 0.3 cm clear inhibition zones of the bacterial lawns on Salmonella typhi plate respectively. Thripala Choorna showed averagely 1.0 cm clear inhibition zone of bacterial lawns on Pseudomonas aeruginosa plates. These zones were clear on every repetition. Theses results were statistically analyzed by using one sample student T-Test. All the means are in between accepted level and P value is <0.05. Comparison to the Chlorampenicol,Higuastka Choorna and Manibadra Choorna are active against Salmonella typhi. Thripala Choorna is active against Pseudomonas aeruginosa. Both, Dathree Choorna and Thalisadee Choorna are not active against any of tested microorganisms. This preliminary study scientifically justifies that the use of the powder preparations of Higuastka Choorna,Manibadra Choorna and Thripala Choorna for infective conditions such as diarrhea, dysentery, vomiting and indigestion.
A Preliminary Study on Microbial Quality Standards of an Ayurvedic Compound Preparation "Thalisadee Choorana".
(2007) Nageeb, B.M.; Widanapathirana, S.; Amarasinghe, A.P.G.; Kasthuriarchi, K.A.H.
Thalisadee choorana is a common Ayurvedic medical preparation widely used by all indigenous medical practitioners in Sri Lanka. It is used for respiratory tract ailments such as cough, common cold, bronchitis, asthmatic conditions and gastro intestinal disorders such as diarrhoea, vomiting, indigestion and loss of appetite. It contains mainly Pipemigram (Gammiris),Piperlongum(Thippili), Abies�wehhiuna (Thalispathra),Cinnamum zylanicum (Kurundupothu), Elettaria repens( Heenensal),Bamboo salt (Unakapuru) and sugar. All plant materials contain a large number of microorganisms.Some are inherent and some are contaminated during the process of harvesting and manufacturing process. Considering these facts, the World Health Assembly in its resolutions WHA-31 :33(1978) 40:33(1987), 42:43(1989) has emphasized the need of ensuring the quality in regard to microbial content of the plant products. Hence this study was carried out to determine the microbial load of this product and the possible sterilization methods of reducing the microbial load. The effect of the method on the drug which reduces the microbial load of the drug also studied. Ten different samples of Thalisadee choorana were subjected to this study. 0.1 gram of the drug sample was dissolved in 10 ml of sterile distilled water. (10�). Using this solution 10-1, 10-2 10-3 dilutions were prepared. Routine sterilization procedures were carried out in all steps.Nutrient agar and Potato dextrose agar were used as general culture media. Pour plate technique and spread plate technique were used to detect the microbial count respectively. 0.1 ml of above dilutions was used on culture plates. Each plate was controlled by using another duplicate culture plate. Plates were sealed and kept under normal room temperature. Colony counts were taken after 24 hours and 72 hours for bacteria and fungi respectively. It was assumed that each colony was formed by a single organism. Same procedure was repeated three times. According to the W.I-I.A standard, aerobic bacteria up to 105 I gram, yeast and moulds up to 103 I gram arc permitted The results ofthe above study indicate that the bacterial count was in between 3x106 to 4xl06 /gram. These results indicate that the limits were exceeding on every sample. The following methods were tried to reduce the microbial load. I 00 grams of the above samples were subjected to (a) Heat treatment in a hot air oven at 80� C for 10 minuets for three consecutive days. (b) Ultra violet radiation at 256 wave length continuously for 24 hours. (c) Steam treatment under atmospheric pressure in a closed container for 10 minuets for three consecutive days. The study of microbial load was thereafter repeated.The plates of the steamed samples were sterile up to 72 hours while the plate of other two methods does not show any reduction in microbial load. The volatile oil content by reflux method using Dead and Stark apparatus and the thin layer chromatographic (T.L.C) patterns of Ethanol extract and Water extracts using Silica gel GF 254 and G06 at the ratio of 1:3 with several solvent systems of both samples (Steamed and un steamed) were studied. The T.L.C. patterns and the volatile oil content of both samples were comparatively same .This preliminary study reveals that the steam treatment method is comparatively an effective method to reduce the microbial load of the above preparation. A detail study of the chemical compounds through other chromatography methods is needed to confirm this.
Antibacterial activity of Lactobacillus strains in spontaneously fermented curd from Sri Lanka
(2016) Wickramaratne, B.; Gunasena, G.D.D.K.
A bacteriophage infecting Mesorhizobium species has a prolate capsid and shows similarities to a family of Caulobacter crescentus phages
(Canadian Journal of Microbiology, 2020) Gunathilake, Damitha; Halmillawewa, Anupama; MacKenzie, Keith; Perry, Benjamin; Yost, Christopher; Hynes, Michael
Mesorhizobium phage vB_MloS_Cp1R7A-A1 was isolated from soil cultivated to chickpea in Saskatchewan and is dissimilar in sequence and morphology to previously described rhizobiophages. It is a B3 morphotype virus with a distinct prolate capsid and belongs to the tailed phage family Siphoviridae. Its genome has a GC content of 60.3% and 238 predicted genes. Putative functions were predicted for 57 genes, which include 27 tRNA genes with anticodons corresponding to 18 amino acids. This represents the highest number of tRNA genes yet reported in a rhizobiophage. The gene arrangement shows a partially modular organization. Most of the structural genes are found in one module, whereas tRNA genes are in another. Genes for replication, recombination and nucleotide metabolism form the third module. The arrangement of the replication module resembles the replication module of Enterobacteria phage T5, raising the possibility that it uses a recombination-based replication mechanism. Phage termini appear to be long direct repeats of length just over 12 kb. Phylogenetic analysis revealed that Cp1R7A-A1 is more closely related to phiCbK-like Caulobacter phages and other B3 morphotype phages than to other rhizobiophages sequenced thus far.
Characterization of Bioactive Actinomycetes Isolated from Kadolkele Mangrove Sediments, Sri Lanka
(Journal of Microbiology, vol.71, 2022) Naligama, Kishani N.; Weerasinghe, Kavindi E.; Halmillawewa, Anupama P.
Exploring untapped microbial potentials in previously uncharted environments has become crucial in discovering novel secondary metabolites and enzymes for biotechnological applications. Among prokaryotes, actinomycetes are well recognized for producing a vast range of secondary metabolites and extracellular enzymes. In the present study, we have used surface sediments from ‘Kadolkele’ mangrove ecosystem located in the Negombo lagoon area, Sri Lanka, to isolate actinomycetes with bioactive potentials. A total of six actinomycetes were isolated on modified-starch casein agar and characterized. The isolates were evaluated for their antibacterial activity against four selected bacterial strains and to produce extracellular enzymes: cellulase, amylase, protease, and lipase. Three out of the six isolates exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus cereus, but not against Listeria monocytogenes. Five strains could produce extracellular cellulase, while all six isolates exhibited amylase activity. Only three of the six isolates were positive for protease and lipase assays separately. Ac-1, Ac-2, and Ac-9, identified as Streptomyces spp. with the 16S rRNA gene sequencing, were used for pigment extraction using four different solvents. Acetone-extracted crude pigments of Ac-1 and Ac-2 were further used in well-diffusion assays, and growth inhibition of test bacteria was observed only with the crude pigment extract of Ac-2. Further, six different commercially available fabrics were dyed with crude pigments of Ac-1. The dyed fabrics retained the yellow color after acid, alkaline, and cold-water treatments suggesting the potential of the Ac-1 pigment to be used in biotechnological applications.
A comparative preliminary study of anti-bacterial effect of ayurvedic compound preparations of Dathree choorna and Hinguastaka choorna
(Sri Lanka Association for the Advancement of Science, 2006) Nageeb, B.M.; Amarasinghe, A.P.G.; Widanapathirana, S.
Effective biocide options for eliminating Ceratocystis spp associated with coir products
(Sri Lanka Association for the Advancement of Science, 2011) Senavirathna, H.G.L.A.K.; Jayaratne, D.L.
This study describes the determination of suitable methods for eliminating the fungus Ceratocystis associated with coir products. Ceratocystis spp is a pathogen causing diseases in several plants including coconut. The occurrence of this organism in coconut cultivations in Sri Lanka has been reported since 1906. Sri Lanka has extensive coconut cultivation and many coir products are exported. It is a quarantine requirement that the coir products are free from this organism. Currently, methyl bromide is used as a fumigant to eliminate the organism, but the use of this chemical is restricted due to its high toxicity and because it affects the ozone layer. In this study the organism was isolated from the coir dust samples collected from the areas of Lunuwila and Kurunegala. The morphological characters of spores were similar in the isolates obtained from these two different locations. However, the color of the chlamydospores was darker in the isolates obtained from Kurunegala than in the samples collected from Lunuwila. The effectiveness of the fumigant formaldehyde (37% formaldehyde 120 ml with 60 g potassium permanganate for 2.83 m3 or 100 ft3 air space) was tested in fumigation chambers parallel with methyl bromide (48 g/m3) on a Potato Dextrose Agar culture and in inoculated coir dust. The formaldehyde was effective for inoculated coir dust but not for the fungus grown on culture plates, while methyl bromide was effective for both. As an alternative method, water vapor heat treatment was applied at different time temperature combinations on coir dust inoculated with fungal spores. At 55 °C for 5 min., the vapor heat treatment destroyed the viable spores in it. For the elimination of Ceratocystis associated with coir dust, formaldehyde can be used in place of the currently used methyl bromide. Formaldehyde is less effective when the organism is grown on culture media due to the different conditions prevalent in culture media and coir dust. Besides the chemical formaldehyde, heat treatment can be applied for eliminating the organism. A temperature of 55 °C generated from water vapor for 5 minutes is sufficient for eliminating the fungal spores.
Fungal pretreatment to enhance the yield ofphytochemicals and evaluation of α-amylase and α-glucosidase inhibition using Cinnamomum zeylanicum (L.)quills pressurized water extracts
(Letters in Applied Microbiology, 2020) Wariyapperuma, W.A.N. Madushika; Kannangara, S.; Wijayasinghe, Y.S.; Subramanium, S.; Jayawardena, B.
Bioactive compounds entrapped in plant materials can be effectively recovered using fungal enzymes. Cinnamomum zeylanicum Sri Wijaya (SW) and Sri Gemunu (SG) accessions and commercially available C. zeylanicum (CC) were subjected to fungal pretreatment and extracted with pressured water (PWE, 0 098 MPa). Thirteen fungal species were isolated and the substrate utilization ability of the species was tested using cellulose, pectin and lignin (indirectly). Total phenolic content (TPC, Folin–Ciocalteu method), proanthocyanidin content (PC, vanillin method) and α-amylase and α-glucosidase inhibitory potential of the extracts were evaluated. The anti-diabetic drug, Acarbose was used as the positive control. Trichoderma harzianum (MH298760) showed the highest cell lysis ability and hence was used for the microbial pretreatment process. Extracts of SW treated with T. harzianum species (Pre-SW) gave the highest percentage yield (4 08% 0 15%), significantly potent inhibition (P < 0 05) of α-amylase and α-glucosidase activities (IC50 57 8 and 36 8 μg ml−1 respectively), TPC (2 24 0 02 mg gallic acid equivalent g−1), and PC (48 2 0 4 mg of catechin equivalent g−1) compared to Pre-SG, Pre- CC and nontreated samples. Trichoderma harzianum treatment can enhance the hypoglycaemic properties, PC and TPC of Cinnamon extracts and provide new insights into the recovery of phytochemicals.
Identification of Potentially Hazardous Microorganisms and Assessment of Physicochemical Deterioration of Thermally Processed King Coconut (Cocos nucifera var. aurantiaca) Water under Different Processing Conditions in Sri Lanka
(Journal of Food Quality, 2022) Jayasinghe, M. D.; Madage, S. S. K.; Hewajulige, I. G. N.; Jayawardana, T. M. D. A.; Halmillawewa, A. P.; Divisekera, D. M. W. D.
King coconut water (KCW) is a sweet relish product that is more prone to rapid quality deterioration, and several safety concerns are emerging due to its inappropriate thermal processing. (erefore, the objective of this study was to identify the potential spoilage/ pathogenic microorganisms associated with the processing of KCW, with the assessment of possible physicochemical changes as providing preliminary information required for the thermal process validation of bottled KCW. Samples (n� 6, 150 ml/sample) were collected from three different KCW processing facilities at five critical processing steps (P1 − P5). A facility survey, physicochemical analyses, and microbial enumeration and isolation, along with their molecular identifications, were conducted. It was found that all tested physicochemical properties were significantly changed (p < 0.05) among sampling points at each processing facility.(ecolour of thermally processed KCW samples has significantly changed (p < 0.05) compared to the fresh KCW, which causes a distinct effect on the appealing quality of the final product. A pattern of initial lower counts with gradually increased microbial counts at intermediate processing steps (1.0 ×103–5.3×106 CFU/ml) and significantly lowered (p < 0.05) counts after thermal treatment was observed. Among the bacterial and fungal isolates identified, several potential pathogenic bacterial species, such as Pantoea dispersa, Bacillus siamensis, Pseudomonas stutzeri, and Acinetobacter lactucae; a few thermal resistant yeasts, Pichia kudriavzevii, Debaryomyces nepalensis, and Candida carpophila; and moulds, Penicillium citrinum, Microdochium fisheri, and Trichosporon asahii, have survived in the thermally processed KCW. Based on the results of the study, it is suggested that the thermal process validation of KCW should be targeted according to the revealed knowledge on the identified hazardous microorganisms, while adhering to Good Manufacturing and Hygienic Practices with minimized handling time to avoid rapid quality deterioration.
Isolation and characterization of bacteria capable of degrading Polycyclic Aromatic Hydrocarbons
(Sri Lanka Association for the Advancement of Science, 2013) Silva, S.I.D.
Isolation and characterization of Rhodomicrobium vannielii from Winogradsky column
(Sri Lanka Association for the Advancement of Science, 2015) Weerasingha, P.D.S.; Gunawardane, M.M.
Isolation and identification of Thiobacillus species and cellulose degrading Clostridium species from Winogradsky column
(Sri Lanka Association for the Advancement of Science, 2014) Weerasingha, P.D.S.; Gunawardane, M.M.
Microbiological investigations of Sigiriya Frescos
(2006) Fernando, S.; Jayaratne, D.L.
The archaeologically valued Frescoes at Sigiriya, a World Heritage Site in Sri Lanka,play a major role in remarkable historic interest. Microbial growth on fresco paintings has been identified worldwide as a significant factor which affects the quality of paintings. Microbiological investigation of fresco paintings therefore has become an important aspect of conservation strategy. The microbiological investigation of the Sigiriya frescoes was carried out in June 2005 by visual detection, microscopic investigations and using microbial culture techniques. The samples for microbial culture techniques were taken from each colour regions separately using sterile cotton swabs and cultured in Nutrient Agar (NA), Trypton Soy Agar (TSA) and Potato Dextrose Agar (PDA) media.The observations revealed that the fresco surface was free from any fungal, lichen or cyanobacterial growth but eleven bacterial cultures were isolated from a decayed patch,from non painted plaster and from a cavity. All the isolates belong to the Genus Bacillus having no conformity with any of the Bacillus spp either indicated in ?Bergy?s manual of systematic bacteriology vol I and II or included in the computer database developed by Trevor Bryant, University of Southampton, UK (2005). One isolate showed similar morphological characteristic features to the Bacillus decoloratiois sp. Nov. bacterium which has been proposed for the new isolate that was responsible for de-colorization of the fresco paintings in Spain and Austria. However, the biochemical characterization of the isolate showed that is a distinctive species having no conformity with Bacillus decoloratiois sp. Nov. Further characterizations using DNA based techniques are being carried out in order to determine whether the isolate is a new species or a similar strain of the Bacillus decoloratiois sp. Nov. In the process of conservation, periodic monitoring and further investigations are being carried out for the detection of microbial growth forms including the Bacillus species on the fresco paintings in order to protect them from any microbial de-colorization and degradation.
Microbiological quality of ballast water discharged from ships arriving in Colombo inner harbour
(Marine Environment Protection Authority, 2015) Jayasundera, C.D.; Rathnayake, I.V.N.
A microbiological study of an Ayurvedic compound preparation Dasamoola Arista with a view to defining an acceptable microbial quality standard
(Sri Lanka Association for the Advancement of Science, 2008) Nageeb, B.M.; Widanapathirana, S.; Amarasinghe, A.P.G.
The Indigenous system of medicine has been practiced successfully over several thousand years. The basic ingredients of indigenous medicine are plant materials. These materials contain natural inherent microbial flora and also may become contaminate during processing. Considering these facts the World Health Assembly in its resolutions WHA-31:33, 40:33, and 42:43 has emphasized the need for the microbial quality standard of medicinal plant products. Dasamoola Arista, has been used in therapeutics for several centuries. The objectives of this study were to enumerate the total viable count of bacteria, fungi and specific microorganisms such as Coliforms and Salmonella in the market samples of this drug. Fourteen different market samples were subjected to this study. Nutrient agar and Potato Dextrose agar were used as culture media. Pour plate and Spread plate techniques were used to study the microbial load in dilution series up to 10-3. Microbial counts on Nutrient agar and Potato dextrose agar were taken after 24 hours and 72 hours. Tests for Coliforms and Salmonella were done according to International standards. Coliform test was performed by MPN method using single strength MacConkey broth. Salmonella was tested after an enrichment process in buffered peptone. 0.1ml of this peptone was transferred to test tubes of Tetrathionate and Selenite broth separately and Incubated at 37 0C for 48 hours. These broths were streaked on Bismuthsulphiteagar (B/S.Agar) and Brilliantgreenbile agar(BGB ) Black colonies on B/S-Agar and Pink colonies on BGB Agar were considered as positive for Salmonella. These colonies were bio chemically tested for salmonella . All tests were repeated thrice and results were confirmed. The microbial load observed in this study was with in the limits of the WHA. The Colony count for Bacteria was in between 10x10 to 10x68. Fungi Colony count was in between 1x10 to 36x 10. The biochemical tests revealed that the Bacteria present in this preparation was Bacillus firmus. None of the drug samples were positive for Coliforms or Salmonella. These results revealed that these tested samples were microbiologically safe and up to the microbial quality standard.
Pectobacterium carotovorum Phage vB_PcaM_P7_Pc Is a New Member of the Genus Certrevirus
(Microbiology Spectrum, 2022) Naligama, K. N.; Halmillawewa, A. P.
Pectobacterium carotovorum is an economically important phytopathogen and has been identified as the major causative agent of bacterial soft rot in carrots. Control of this phytopathogen is vital to minimizing carrot harvest losses. As fully effi- cient control measures to successfully avoid the disease are unavailable, the phage- mediated biocontrol of the pathogen has recently gained scientific attention. In this study, we present a comprehensive characterization of the P. carotovorum phage vB_PcaM_P7_Pc (abbreviated as P7_Pc) that was isolated from infected carrot samples with characteristic soft rot symptoms, which were obtained from storage facilities at market places in Gampaha District, Sri Lanka. P7_Pc is a myovirus, and it exhibits growth characteristics of an exclusively lytic life cycle. It showed visible lysis against four of the tested P. carotovorum strains and one Pectobacterium aroidearum strain. This phage also showed a longer latent period (125 min) than other related phages; however, this did not affect its high phage titter (.1010 PFU/mL). The final assembled genome of P7_Pc is 147,299 bp in length with a G1C content of 50.34%. Of the 298 predicted open reading frames (ORFs) of the genome of P7_Pc, putative functions were assigned to 53 ORFs. Seven tRNA-coding genes were predicted in the genome, while the genome lacked any major genes coding for lysogeny-related products, con- firming its virulent nature. The P7_Pc genome shares 96.12% and 95.74% average nu- cleotide identities with Cronobacter phages CR8 and PBES02, respectively. Phylogenetic and phylogenomic analyses of the genome revealed that P7_Pc clusters well within the clade with the members representing the genus Certrevirus. Currently, there are only 4 characterized Pectobacterium phages (P. atrosepticum phages phiTE and CB7 and Pectobacterium phages DU_PP_I and DU_PP_IV) that are classified under the genus, making the phage P7_Pc the first reported member of the genus isolated using the host bacterium P. carotovorum. The results of this study provide a detailed characteriza- tion of the phage P7_Pc, enabling its careful classification into the genus Certrevirus. The knowledge gathered on the phage based on the shared biology of the genus will further aid in the future selection of phage P7_Pc as a biocontrol agent.
Pectobacterium spp. isolated from rotting carrots obtained from markets in Gampaha district, Sri Lanka exhibit the potential of having broad host ranges
(Eur J Plant Pathol, 2022) Naligama, K.N.; Halmillawewa, A.P.
Carrot production in Sri Lanka faces severe post-harvest losses due to bacterial soft rot. The quality deterioration of vegetables owing to typical bacterial soft rot can greatly affect the market value and consumer preference. Although the carrot soft rot causing bacteria occur all over the world, and are well-studied and characterized, the scarcity of data on the precise identification of the causal agents of the disease in Sri Lanka acts as a great barrier in managing such post-harvest losses. In an attempt to bridge this knowledge gap, we have isolated potential causative agents of bacterial soft rot from diseased carrot samples collected from Gampaha district, Sri Lanka.All the seven bacterial isolateswere confirmed for their ability to exhibit pectolysis, and vegetable disk assays were used to evaluate the pathogenicity of bacterial isolates. The pathogenicity assays showed that these isolates have the ability to infect not only carrot, but also potato, radish, beetroot and Napa cabbage, suggesting their possible broad host range. The ITS–PCR RELP profiles of the pectobacterial isolates and hierarchical clustering of the resulting profiles have placed the strains isolated in this study into four groups. The 16S rRNA gene sequencing and subsequent analyses aided in identifying isolates as Pectobacterium carotovorum (C1B5, C2B6, C2B7 and C2B8), P. aroidearum (C1B3 and C1B4), and P. polaris (C3B9). The study indicated the possibility of different Pectobacterium spp. being involved in causing carrot soft rot in the area, emphasizing the need to carry out an island-wide, comprehensive analysis to understand the distribution of the pathogen, which could be used in implementing successful disease management strategies.
Phenotypic and genotypic characterization of antibiotic resistance of Listeria monocytogenes isolated from raw milk samples collected from Polonnaruwa, Sri Lanka
(Emirates Journal of Food and Agriculture, 2022) Harshani, H.B.C.; Ramesh, R.; Halmillawewa, A.P.; Wijendra, W.A.S.
Listeria monocytogenes is a food-borne pathogen that can cause severe invasive infection called ‘listerosis’ in humans. Development of antibiotic resistance is a major setback in the management of conditions caused by Listeria in both human and veterinary medicine. In this study, antibiotic resistance of fifty L. monocytogenes strains isolated from raw milk samples collected from farms in Polonnaruwa district, Sri Lanka was determined for four commonly used antibiotics; penicillin, ampicillin, streptomycin and tetracycline. The strains were also tested for the presence of selected antibiotic resistant genes (penA, ampC, strA, strB, tetA and tetB). L monocytogenes isolates showed resistance to ampicillin (60%), penicillin (40%) streptomycin (16%) and tetracycline (8%) in diffusion assays. Phenotypic multidrug resistance was exhibited by twenty isolates. The tetracycline resistant gene (tetA) was detected in seven isolates, while tetB was not detected in any. Presence of streptomycin resistant genes (strA or strB) was confirmed in seven isolates. Ampicillin (ampC) and penicillin (penA) resistant genes were not detected in any of the tested isolates. Except from the samples collected from Sungavila area, isolates from other sampling areas showed resistance to at least one of the antibiotics tested, suggesting that raw milk samples are prone to be contaminated with L. monocytogenes strains with different antibiotic resistant profiles. Therefore, necessary hygienic precautions are recommended to avoid any potential public health threats and to safeguard the health of raw milk consumers.
Potential Biocide Options and Biological Control Agent For Ceratocystis paradoxa Isolated From Coconut Growing Areas of Sri Lanka
(2016) Jayaratne, D.L.; Dayarathna, M.T.A.
Potential use of Chlorella vulgaris KCBAL01 from a freshwater stream receiving treated textile effluent in hexavalent chromium [Cr(VI)] removal in extremely acidic conditions
(Journal of Environmental Science and Health, 2022) Aththanayake, A. M. K. C. B.; Rathnayake, I. V. N.; Deeyamullab, M. P.; Megharaj, Mallavarapu
Remediation of hexavalent chromium with conventional chemical and physical methods is a costly process, while replacing some critical steps in physiochemical remediation with self-sustaining bioremediation agents are expected to be cost-effective and environmentally friendly implementation. In this study, a microalga isolated from a freshwater stream receiving treated textile wastewater was identified up to its molecular level and investigated its ability to tolerate and remove hexavalent chromium from extremely acidic conditions under different temperatures. The ability of microalgae to tolerate and remove Cr(VI) was investigated by growing it in BG11 media with different pH (1, 2, 3 & 7), amended with several concentrations of Cr(VI) and incubated under different temperatures for 96 hrs. Microalga was identified as Chlorella vulgaris and found that the isolated strain has a higher hexavalent chromium removal potential in extremely acidic conditions than in neutral pH conditions at 25 C. In contrast, its Cr(VI) removal potential is significantly influenced by the pH and temperature of the growth medium. Furthermore, it exhibited a permanent viability loss at extreme acidic conditions (pH 1 3) and prolonged exposure to the higher chromium content. The microalga investigated will be a highly useful bioagent in hexavalent chromium remediation in high acidic conditions.