Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009

<p>Abstract</p> <p>Background</p> <p>Singapore has been certified malaria free since November 1982 by the World Health Organization and despite occasional local transmission, the country has maintained the standing. In 2009, three clusters of malaria cases were reported in Singapore.</p> <p>Methods</p> <p>Epidemiological, entomological and molecular studies were carried out to investigate the three clusters, namely Mandai-Sungei Kadut, Jurong Island and Sembawang.</p> <p>Results</p> <p>A total of 29 malaria patients, with no recent travel history, were reported in the three clusters. Molecular analysis based on the <it>msp3α </it>and <it>msp1 </it>genes showed two independent local transmissions: one in Mandai-Sungei Kadut and another in Sembawang. Almost all cases within each cluster were epidemiologically linked. In Jurong Island cluster, epidemiological link remains uncertain, as almost all cases had a unique genetic profile. Only two cases shared a common profile and were found to be linked to the Mandai-Sungei Kadut cluster. Entomological investigation found <it>Anopheles sinensis </it>to be the predominant Anopheline in the two areas where local transmission of <it>P. vivax </it>was confirmed. <it>Anopheles sinensis </it>was found to be attracted to human bait and bites as early as 19:45 hrs. However, all <it>Anopheles </it>mosquitoes caught were negative for sporozoites and oocysts by dissection.</p> <p>Conclusion</p> <p>Investigation of <it>P. vivax </it>cases from the three cluster areas confirmed the occurrence of local transmission in two areas. Although <it>An. sinensis </it>was the predominant Anopheline found in areas with confirmed transmission, the vector/s responsible for the outbreaks still remains cryptic.</p

Synergistic effect of ERK inhibition on tetrandrine-induced apoptosis in A549 human lung carcinoma cells

Tetrandrine (TET), a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, is known to have anti-tumor activity in various malignant neoplasms. However, the precise mechanism by which TET inhibits tumor cell growth remains to be elucidated. The present studies were performed to characterize the potential effects of TET on phosphoinositide 3-kinase/Akt and extracellular signal-regulated kinase (ERK) pathways since these signaling pathways are known to be responsible for cell growth and survival. TET suppressed cell proliferation and induced apoptosis in A549 human lung carcinoma cells. TET treatment resulted in a down-regulation of Akt and ERK phosphorylation in both time-/concentration-dependent manners. The inhibition of ERK using PD98059 synergistically enhanced the TET-induced apoptosis of A549 cells whereas the inhibition of Akt using LY294002 had a less significant effect. Taken together, our results suggest that TET: i) selectively inhibits the proliferation of lung cancer cells by blocking Akt activation and ii) increases apoptosis by inhibiting ERK. The treatment of lung cancers with TET may enhance the efficacy of chemotherapy and radiotherapy and increase the apoptotic potential of lung cancer cells

DISTRIBUTION AND BIONOMICS OF ANOPHELES SINENSIS, AND ITS ROLE INMALARIA TRANSMISSION IN SINGAPORE

Ph.DDOCTOR OF PHILOSOPH

Influence of Nutrient Addition on the Bioethanol Yield from Oil Palm Trunk Sap Fermented by Saccharomyces Cerevisiae

This paper presents the influence of nutrient addition namely MgSO4, C3H7NO2, (NH4)2SO4 and Na2HPO4 to the bioethanol yield from oil palm trunk saps (OPTS) with fermentation carried out by Saccharomyces cerevisiae. The sugar and ethanol contents in the sample were determined using a high-performance liquid chromatography. Nutrient addition has improved the bioethanol yield markedly, with the average yield ranged from 58.50% to 77.12% compared to about 51.08% without nutrient addition. The highest bioethanol yield (81.89%) was achieved by adding MgSO4. The rank of nutrient influence on improving the bioethanol yield was MgSO4 > C3H7NO2 > (NH4)2SO4 > Na2HPO

Optimisation of Bioethanol Yield from Oil Palm Trunk Sap

This paper presents the effect of nutrients addition and fermentation microorganism on bioethanol yield from oil palm trunk sap. Six microorganisms namely, Saccharomyces cerevisiae ATCC 9763, Saccharomyces cerevisiae ATCC 26602, baker’s yeast, Kluyveromyces marxianus ATCC 46537, Zymomonas mobilis ATCC 29501 and Escherichia coli ATCC 10536 were screened for ethanol production at fixed temperature, pH, agitation and inoculum size. The sugar and ethanol content were determined using a high performance liquid chromatography (HPLC). The results showed that K. marxianus produced the highest ethanol yield (60.9%) at a shorter fermentation time (16h) compared to the other strains. Six nutrients, namely, ammonium sulphate, di-ammonium hydrogen phosphate, magnesium sulphate, β-alanine, calcium chloride and potassium dihydrogen phosphate were screened using this strain and the highest ethanol yield (98.62%) was achieved in fermentation supplemented by magnesium sulphate and β-alanine. Subsequently, the optimisation study using a reseponse surfae methodology found the optimum value of magnesium sulphate was 7.93 g/L and 0.90 g/L for β-alanine. Under the optimum conditions, the predicted ethanol concentration was 34.58 g/L while the experimental value (35.50 g/L) was in agreement with the predicted value with 2.66% error

Optimisation of Oil Palm Trunk Sap Fermentation to Bioethanol

Malaysia has an abundant amount oil palm biomass (approx. 15 million tons annually) arising from replanting activities involving old oil palm aged above 20 years-old which has lower productivity. In some cases, the outer hard portion of the oil palm trunk is utilised for plywood manufacturing, but the soft inner portion is normally discarded. This soft inner portion contains a huge amount of sugar-rich sap that can be fermented into bioethano

Singapore’s Anopheles sinensis Form A is susceptible to Plasmodium vivax isolates from the western Thailand–Myanmar border

Abstract Background Singapore has been certified malaria-free by the World Health Organization since November 1982. However, sporadic autochthonous malaria outbreaks do occur. In one of the most recent outbreaks of vivax malaria, an entomological investigation identified Anopheles sinensis as the most probable vector. As metaphase karyotype studies divided An. sinensis into two forms, A and B, with different vector competence: the investigation of vector competence of An. sinensis found in Singapore was thus pursued using Plasmodium vivax field isolates from the Thailand–Myanmar border. Methods Adults and larvae An. sinensis were collected from Singapore from 14 different locations, using various trapping and collection methods between September 2013 and January 2016. Molecular identification of An. sinensis species were conducted by amplifying the ITS2 and CO1 region using PCR. Experimental infections of An. sinensis using blood from seven patients infected with P. vivax from the Thailand–Myanmar border were conducted with Anopheles cracens (An. dirus B) as control. Results Phylogenetic analysis showed that An. sinensis (F22, F2 and collected from outbreak areas) found in Singapore was entirely Form A, and closely related to An. sinensis Form A from Thailand. Artificial infection of these Singapore strain An. sinensis Form A resulted in the development of oocysts in four experiments, with the number of sporozoites produced by one An. sinensis ranging from 4301 to 14,538. Conclusions Infection experiments showed that An. sinensis Form A from Singapore was susceptible to Thai–Myanmar P. vivax strain, suggesting a potential role as a malaria vector in Singapore

Entomological Investigation and Control of a Chikungunya Cluster in Singapore

In August 2008, a team from the National Environmental Agency conducted an entomological investigation of a chikungunya cluster in Singapore, with the primary aim of identifying the vector responsible for the outbreak and to assess the vector control operation. A total of 173 adult mosquitoes were caught using both the sweep-net method and the BG Sentinel Traps in and around the affected workers' quarters. Of these, 120 (69.4%) were Aedes albopictus and the rest were Culex quinquefasciatus. More than 2700 Ae. albopictus larvae were also collected from 33 breeding habitats detected. No Aedes aegypti was found. During the preintervention period, 6 (8.4%) out of 71 adult female Ae. albopictus were found positive for the chikungunya virus (CHIKV). Vector control measures resulted in a 90% reduction of adult Ae. albopictus caught by BG Sentinel Traps. Postintervention surveillance revealed the presence of CHIKV-positive mosquitoes. These findings led to continued intensive vector control operation in the affected area that further reduced vector population and interrupted the transmission of the disease. The E1 gene sequence of the CHIKV was identical to those of CHIKV isolated from human chikungunya cases working in the affected area, and contained the A226V mutation. The incrimination of Ae. albopictus as a major vector involved in the transmission of A226V CHIKV had led to the revision of chikungunya control strategy in Singapore. This study suggests the benefit of a vector control program that includes the evaluation of control measures in conjunction to virological surveillance in vector population