Browsing by Author "Perera, E. H. L."

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Antibacterial efficacy and phytochemical properties of Citrus crenatifolia (Heen Narang) and Citrus reticulata (Jama Narang)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Salwathura, I. A.; Deraniyagala, N. G. I. A.; Fernando, N. H.; Perera, M. D.; Perera, E. H. L.; Ranasinghe, H. A. K.
The Citrus family encompasses various plant species known for their antibacterial properties. Various parts of Citrus plants have been used in traditional Sri Lankan medicine for an extended period. Citrus reticulata was selected for its established antibacterial properties, providing a foundation to further investigate its potential alongside the less-researched Citrus crenatifolia. The present study was conducted to investigate the antibacterial properties of C. crenatifolia and C. reticulata found in Sri Lanka. Active phytochemicals were extracted from the peels, using the reflux method employed in an aqueous medium. The antibacterial properties of plant extracts were assessed using the well diffusion method against six common bacterial pathogens; Staphylococcus aureus (ATCC 23235), Pseudomonas aeruginosa (ATCC 15442), Proteus mirabilis (ATCC 35659), Klebsiella pneumoniae (ATCC 13883), Escherichia coli (ATCC 25922) and Enterococcus faecalis (ATCC 29212). Double distilled water was used as the negative control, while commonly used antibiotics (ampicillin, penicillin, gentamicin, vancomycin, augmentin, and ciprofloxacin) served as the positive controls. A McFarland standard was employed for each test microbe. The diameter of inhibition zones was measured after incubation, and statistical analysis was performed using the SPSS software package. The independent sample t-test revealed that there was no significant difference between the mean values of the control and both peel sample extractions for all tested bacteria. (p = 0.115). There was no statistically significant difference in antibacterial activity among the six microbes according to the One-Way ANOVA test for C. reticulata (p = 0.271). But there was a statistically significant difference in the antibacterial activity of C. crenatifolia (One-Way ANOVA: p = 0.021). Tukey’s Post-Hoc analysis of C. crenatifolia extract showed a significant difference in the mean inhibition zone diameters between S. aureus and P. aeruginosa (p = 0.044) as well as S. aureus and K. pneumoniae (p = 0.049). The antibacterial activities of both extracts were supported by the presence of phytochemicals such as alkaloids, steroids, flavonoids, phenol, and tannins which showed combination effects. Anyhow, saponins were not detected in both extracts. The present findings highlight the potential of C. crenatifolia and C. reticulata extracts as valuable sources of antibacterial agents, warranting potential applications in the field of microbial control. Further investigation to elucidate its specific mechanisms of action is recommended.
Assessment of the distribution of Aedes breeding sites at the households of district of Gampaha
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, E. H. L.; Hapugoda, M. D.; Viswakula, S.; Gunawardene, Y. I. N. S.; Subasinghe, U.; Fernando, L.; Manamperi, A.
Dengue is the most important mosquito-borne viral infection in Sri Lanka at present. Integrated Vector Management (IVM) targeting dengue vector mosquitoes has become the main disease control measure. The objective of this study was to assess the distribution of the Aedes breeding habitats in dengue high and low risk areas in the District of Gampaha where the second highest incidence of dengue reported during last 10 years. Negombo Medical Officer of Health (MOH) area was selected based high incidence of dengue cases reported in the District of Gampaha during last 10 years. A dengue high risk (Kurana East) and low risk (Udayarthoppuwa) Grama Niladhari (GN) divisions with similar geographical situation in the same MOH area were selected as study and control areas respectively. Standard larval surveillance was conducted randomly selected 150 houses in each site for 18 months (April, 2018-October, 2019). In the dengue high risk and low risk areas, the proportions of the larvae of Aedes species to the total larval collection were 34.19% (185/541) and 21.68% (147/678) respectively. High densities of Ae. albopictus larvae were reported in both high [171/185=92.4%)] and low [141/147=95.92%) risk areas. Ae. aegypti was present in low abundance in both areas [High risk-7.56% (14/185) and Low risk- 2.72% (4/147)]. In the high-risk site, breeding sites of the Ae. albopictus larvae were reported as plastic buckets/barrels (55.19 %-154/279), waste plastics (35.15%-98/279), metal tins (3.94%-11/279) and tube wells (2.86%-8/279). In low-risk area, the majority of breeding sites for Ae. albopictus larvae was found in coconut shells (76.14%- 201/264) and plastic waste (21.96%-51/264). In both areas, Ae. aegypti larvae was found in plastic buckets/barrels only. There is a significance difference between the Ae. albopictus breeding places in the dengue high and low risk areas (P=0.024). Although Ae. aegypti is considered as the major vector of dengue, Ae. albopictus was reported as the prominent dengue vector species in the high dengue risk area in the District of Gampaha. Even though, municipal council removes solid waste weekly, a large number of breeding sites are available at both areas. As there is a significant difference between Ae. albopictus breeding sites at the dengue high and low risk areas, it is essential to specifically focus on removal of breeding sites for successful vector control measure.
Study on the resting preferences of Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse) adult mosquitoes in the district of Colombo
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, E. H. L.; Gunawardene, Y. I. N. S.; Hapugoda, M. D.; Ranathunge, T.; Udayanga, N. W. B. A. L.
Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) are the world’s most widely distributed mosquito species and, act as major contributors to many mosquito-borne diseases. Remarkable behavioral and ecological attributes make these mosquitoes as efficient vectors. Due to the behavioral and ecological plasticity of Ae. aegypti and Ae. Albopictus, it has become a major limitation in vector control and disease management measures in Sri Lanka. The objective of this study was to determine key bionomics aspects, namely resting preferences of Ae. aegypti and Ae. albopictus in the District of Colombo. Three Medical Officer of Health (MOH) areas were selected for the current study based on previous dengue cases. The two high risk areas (Maharagama and Kolonnawa) and a low-risk area (Padukka) were selected as study sites. Adult mosquito surveillance was conducted in outdoor and indoor settings using a mouth aspirator for one year (November, 2019-October, 2020). Adult mosquito collection included the aspiration from all rooms within the home including furniture, behind hanging clothes and curtains, behind and around cooking utensils and from dark and humid places, where mosquitoes were found resting. A total of 658 Aedes adult mosquitoes were collected from both indoor and outdoor resting locations (total number of resting sites= 432). The most abundant vector species was Ae. aegypti (65.0%; n=428), followed by Ae. albopictus (35.0%; n= 230) in Maharagama and Kolonnawa MOH areas. The most and least abundant Aedes mosquito collection MOH areas were Maharagama 44.5% (n=293) and Padukka 23.2% (n=153), respectively. Ae. Aegypti adult mosquitoes denoted an endophilic behaviors (97.1%; n=416), while Ae. albopictus denoted an exophilic resting behavior (81.30% n= 187). In terms of resting places, Ae. aegypti was mostly found in resting places such as bedroom (36.0%; n=154), kitchen (26.2%; n=112) living room (21.3%; n=91), and outdoor vegetation (1.4%; n=06). Meanwhile, Ae. albopictus was conducive to rest on the vegetation (50.4%; n=116), front of the house-external (23.8%; n=109). The highest percentage of Aedes mosquitoes were found resting on wooden surfaces in both indoor and outdoor sites (52.3%; n=344), followed by clothes/curtains (24.2%; n=159) and cement surfaces (17.0%). Resting behavior of vectors is an important fact since they are prerequisites to determine their role in disease transmission in endemic settings. This study revealed that the resting behavior varied between the two Aedes vector species, were Ae. aegypti adult mosquitoes denoted highly endophilic nature, while Ae. albopictus demonstrated exophilic behavior. In this study Ae. aegypti was mainly found resting in bedrooms, living rooms and kitchens and Ae. albopictus was found resting mainly among outdoor vegetation. The outcome of this study facilitates the relevant health authorities who engage with dengue control programs, to successfully eradicate the vector from resting sites.