Tropical biomedicine最新文献

Strongyloidiasis, caused by Strongyloides stercoralis, is a neglected disease with a worldwide prevalence, particularly in tropical and subtropical regions. Most people have chronic asymptomatic infections, which may transform into potentially fatal hyper- or disseminated infections when immunosuppressed. Cancer patients on corticosteroids are at an increased risk of developing severe forms of the infection due to their impaired immune status. The present study used molecular, serological, and parasitological methods to detect S. stercoralis infection in cancer patients on corticosteroids. Using faecal and serum samples from 99 individuals, real-time PCR demonstrated the highest detection rate (27.3%), followed by the Strongyloides IgG4 rapid test (IgG4-RDT or SsRapid) (22.2%) and a commercial IgG-ELISA (4.0%). Agar plate culture performed on 88 of 99 stool samples was negative. There was no significant difference in detection prevalence between the IgG4-RDT and real-time PCR (p = 0.413), and the agreement between them was slight (kappa coefficient, 0.108). Using a composite reference standard (CRS), 41 of 99 samples (41.4%) were classified as positive for Strongyloides infection. Based on the CRS, PCR demonstrated higher sensitivity (65.9%) than IgG4-RDT (53.7%), while both assays exhibited 100% specificity and positive predictive value (PPV). The negative predictive value (NPV) was greater for PCR (80.6%) than IgG4-RDT (75.3%). McNemar's test indicated no significant difference between the two assays (p = 0.49). Notably, combining results of the real-time PCR and IgG4-RDT increased the detection rate to 41%, which was significantly higher than that of PCR alone (27%, p = 0.036) or IgG4-RDT alone (22%, p = 0.0036). The combined results showed substantial agreement with PCR (k = 0.693) and moderate agreement with IgG4-RDT (k = 0.576). In conclusion, the combination of real-time PCR and IgG4-RDT offers a more reliable approach for detecting S. stercoralis in cancer patients undergoing corticosteroid therapy than either assay alone.

Currently, the standard therapeutic approach for the prevention and management of toxoplasmosis is the administration of chemical agents, which are associated with significant adverse side effects. Considering the elucidations presented and the biological properties of camphene (CP), the current research seeks to check the effects and the synergistic interactions of this natural monoterpene against Toxoplasma gondii. The anti-Toxoplsma and synergic effects of CP were examined against T. gondii tachyzoites and its intracellular forms. Furthermore, the impact of CP on the T lymphocytes- associated cytokines and DNA damage- related genes, as well as its effects on the plasma membrane and inducing apoptosis and the nitric oxide (NO) production, were evaluated. CP, principally in conjugation with pyrimethamine (PY), notably (p<0.001) dropped the tachyzoites viability, the intracellular forms, and the rate of infection in macrophages. The obtained FICI values of lower 0.5 for CP and PY indicate synergistic effects when CP is used in conjunction with PY. CP meaningfully upregulated tumor necrosis factor-alpha (TNF-a), interferon-gamma (IFN-g), and interleukin-12 (IL-12), and DNA damage-related genes, as well as NO releases in macrophage cells and the caspase-3 activity within the tachyzoites. The application of CP to tachyzoites displayed a dosage-dependent enhancement in plasma membrane permeability. The selectivity index values for CP, PY, and PY+CP exceeded 10, suggesting their safety for macrophages and specificity toward the parasite. We discovered that CP displayed promising in vitro antiparasitic properties against T. gondii. Additionally, the findings emphasized the potential of CP to eradicate tachyzoites through triggering apoptosis, NO production, and DNA damage, provoking cellular immunity cytokine, and increasing the plasma membrane permeability. Even so, advance evaluation is needed to clarify other mechanisms underlying its action and to evaluate its effectiveness in animal models and clinical trials.

Culex pipiens is among the most abundant mosquitoes in Algeria. This mosquito poses a significant public health risk as a vector of various diseases. Developing efficient and eco-friendly pesticides has also become a highly important issue to reduce the risks associated with conventional insecticides. In this context, the present study aimed to evaluate the responses of fourth-instar larvae of Culex pipiens (C. pipiens) to the effects of two essential oils (EOs) Eucalyptus globulus (E. globulus) and Eucalyptus radiata (E. radiata), both known for their bioinsecticidal properties. The oils were obtained by steam distillation and their chemical composition was determined using gas chromatography coupled to mass spectrometry (GC-MS). Larvicidal bioassays were conducted under laboratory conditions, and in silico analyses were performed to evaluate interactions between the major essential oils constituents and two detoxification enzymes acetylcholinesterase (AChE; PDB ID: 5X61) and glutathione S-transferase (GST; PDB ID: 18GS). E. radiata yielded a higher oil content (1.25 ± 0.36% w/w) than E. globulus (0.92 ± 0.48% w/w). GC-MS profiling revealed marked compositional differences: E. globulus EO was dominated by 1,8-cineole (72.05%), whereas E. radiata contained o-cymene (32.23%) as the main compound. Both EOs showed significant larvicidal activity (p<0.001) against C. pipiens, with E. globulus demonstrating greater potency (LC⁵⁰ = 23.74 ppm) compared to E. radiata (LC⁵⁰ = 53.42 ppm). In silico studies demonstrated that the major constituents of both essential oils exhibit strong insecticidal potential through various interactions with acetylcholinesterase and glutathione S-transferase. Compounds from Eucalyptus globulus showed slightly better binding affinities overall. These results support the development of safe and eco-friendly insecticides, offering a sustainable strategy for protecting both public health and the environment, especially through natural larvicides derived from essential oils targeting Culex pipiens mosquitoes.

Melioidosis is a severe infection caused by Burkholderia pseudomallei and is endemic in tropical regions, such as Southeast Asia. Favourable climate and substantial agricultural sectors contribute to a high incidence of melioidosis in Pahang, Malaysia. This study aims to identify factors associated with melioidosis mortality in Pahang from 2020 to 2024, with an emphasis on sociodemographic, occupational, clinical, and environmental determinants. A retrospective cohort study was conducted using the state-driven melioidosis registry. All confirmed cases between 2020 and 2024 were included in the analysis. All variables were extracted and analysed using simple and multiple logistic regression to identify the risk factors for melioidosis mortality. Out of 466 confirmed cases, 68 (14.6%) died from melioidosis. The median age was 48 years (IQR: 34-60), with the majority being male (76%) and originating from rural areas (71%). The incidence, mortality and case fatality rates fluctuated over the study period. The final regression model analysis identified three risk factors for mortality which include non-Malaysian ethnicity (aOR 3.27; 95% CI: 1.43-7.51), chronic obstructive pulmonary disease (COPD) (aOR 8.71; 95% CI: 1.11-68.39), and intensive care unit (ICU) admission (aOR 3.44; 95% CI: 1.91-6.17). In contrast, diabetes mellitus, which is often associated with increased risk of mortality, was not found to be significant in this study, nor was the level of monthly rainfall. These study findings highlight the need to address social determinants of health among vulnerable populations and to prioritise early recognition and management, especially for patients with COPD.

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly and caused a pandemic in 2020. Both pharmaceutical approaches, such as vaccinations and non-pharmaceutical approaches such as social distancing through lockdown and international border restrictions had been implemented to control the outbreak and the transmission of SARS-CoV-2. However, the prolonged implementation of these measures negatively impacted the population and global economy, while the continuously emerging SARS-CoV-2 variants led to breakthrough infections among the vaccinated populations. Given the ongoing nature of COVID-19, an efficient detection method for SARS-CoV-2 that could enable mass screening and on-site screening is needed to manage the disease and prevent further outbreaks at large scale. Hence, we have developed a tetra-combo LAMP SARS-CoV-2 detection assay that targets four SARS-CoV-2 genes (RdRp, S, E and N), with an internal control (RNaseP). The LAMP assay was validated using 370 RNA samples extracted from nasopharyngeal and/or oropharyngeal swabs. The LAMP assay developed in this study has on-par performance as the qRT-PCR assay, which is the gold standard method for SARS-CoV-2 detection, with a shorter turnaround time (25 minutes). The LAMP assay possessed 98.13% sensitivity, 100% specificity, 100% positive predictive value (PPV), and 95.45% negative predictive value (NPV) for samples with Ct values <= 35.

Taeniasis is a parasitic infection in humans by tapeworm species typically acquired through the ingestion of undercooked pork or beef leading to infections with Taenia solium, Taenia asiatica or Taenia saginata. We reported a case of taeniasis in a young man of Chinese nationality who presented with recurrent episodes of expelling proglottids. He was at risk due to his preference for consuming undercooked beef. He remained asymptomatic and his physical examination was unremarkable. A 330 cm tapeworm was recovered; each mature proglottid contained 12-30 primary lateral uterine branches. Stool examination revealed eggs consistent with Taenia species. DNA sequencing from the isolate confirmed the identification of T. saginata.

Pediculosis capitis, caused by infestation of the human head louse Pediculus humanus capitis is endemic all over the world, and Malaysia is no exception. Permethrin is recommended as one of the first-line treatments for pediculosis capitis. However, after decades of intensive and continuous use, numerous treatment failures and recurrent cases have been reported globally due to established evidence of permethrin resistance. The fact that permethrin-based products are still widely used and available over the counter prompted this study to investigate the genotypic basis of permethrin resistance and to identify kdr alleles in head lice collected from seven children shelters located across Klang Valley, Malaysia. The PCR-RFLP employed in this study successfully demonstrated the kdr T917I mutation in head lice resulting in two genotypes: 31 (49.21%) homozygous susceptible (SS) and 32 (50.79%) heterozygous resistant (RS). These findings provide baseline data on permethrin resistance in Malaysia, which has not been previously investigated.

Protozoan and helminthic parasitism remain significant health and economic burdens, particularly in developing countries such as the Philippines. This study evaluated the Rinconada Lake System (RLS) in Camarines Sur, comprising Lakes Buhi, Bato, and Baao, as a potential reservoir for medically important parasites. Microscopic examination of surface water samples from 20 stations revealed no helminthic ova, which may have settled in sediments, but detected potential coccidian oocysts of Cryptosporidium spp. (55%, 11/20) and Cyclospora sp. (40%, 8/20). Culture-based detection of free-living amoeba was at 60% (36/60), showing organisms resembling Acanthamoeba spp. (35% or 21/60) significantly linked to Lake Baao and Lake Bato (P < 0.01) likely reflecting greater anthropogenic influence. The metabarcoding confirmed the presence of protozoan parasites in the lakes, such as Echinamoeba sp. and Vermamoeba vermiformis, while no helminthic parasites were detected using current methods. Additional microbial eukaryotes of medical relevance, such as fungi and algae, were also identified. Retrospective analysis of the available health records from surrounding communities showed that Entamoeba histolytica was the most documented case for 4 years (47.8% or 75/157), followed by various helminthic infections (49.7% or 78/157), predominantly caused by Ascaris lumbriocoides. There was no significant association with the patient's residence or sex, except for significantly higher cases in those aged 0-10 years. In conclusion, findings suggest that the RLS may serve as an environmental reservoir for opportunistic protozoan parasites, while its role in helminthic transmission requires further investigation. Based on current evidence, emphasis on surveillance and mitigation strategies in communities surrounding the RLS, especially for protozoan parasites, is highly recommended.

Despite ongoing vector control programs, dengue incidence in Malaysia continues to rise. A significant contributing factor is the emergence of insecticide resistance in Aedes mosquitoes, particularly against pyrethroids such as permethrin. This study aimed to evaluate permethrin resistance in Aedes aegypti and Aedes albopictus from Kuala Lumpur and Selangor and to investigate the prevalence of knockdown resistance (kdr) mutations in the voltage-gated sodium channel (Vgsc) gene. Due to limited sample quantity and quality, molecular assessment of kdr mutations was performed only for Ae. aegypti. Ovitraps were deployed in three dengue hotspot areas to collect Aedes eggs. Eggs were reared to adulthood under controlled laboratory conditions. Adult female mosquitoes were subjected to the WHO tube bioassay using permethrin to assess phenotypic resistance. Genomic DNA was extracted from individual Ae. aegypti, and polymerase chain reaction (PCR) was conducted to amplify target regions of the Vgsc gene using published kdr-associated primers. Direct sequencing of PCR products was performed to identify point mutations associated with pyrethroid resistance. Both Ae. aegypti and Ae. albopictus populations showed high levels of permethrin resistance, with mortality rates of <5% and <50%, respectively, indicating confirmed resistance. Sequencing of Ae. aegypti revealed the presence of pyrethroid resistance-associated kdr mutations, including S989P, A1007G, V1016G, and F1534C. These findings suggest strong selective pressure on local Ae. aegypti populations, reflecting ongoing adaptation to insecticidal interventions. The identification of these mutations emphasizes the challenges faced by current vector control strategies relying predominantly on chemical control.The detection of both phenotypic permethrin resistance and kdr mutations in Ae. aegypti populations from Kuala Lumpur and Selangor highlights the urgent need to revise and diversify vector control strategies. Improved sampling and molecular surveillance of Ae. albopictus are recommended to provide a more comprehensive understanding of insecticide resistance dynamics in Malaysian dengue vectors.

Ovitrap surveillance of Aedes vectors in Sri Lanka needs improvement to effectively monitor vector abundance in dengue high-risk areas and detect emerging infestation zones. A study was conducted in two dengue high-risk areas, Narahenpita and Battaramulla in the Western Province, to assess the influence of ovistrip texture, color, and water type on Aedes oviposition, while adhering to WHO guidelines. The relationship of OI and the mean number of eggs per trap with ovitrap designs were determined by General Linear Model (GLM), which revealed a significant difference in the OI between the two study sites (P=0.005), while the mean number of eggs per ovitrap did not differ significantly (P=0.134). Water type had no significant influence on OI and mean number of eggs per ovitraps. A significant effect of ovistrip type (F=6.73, P<0.001) was found on OI and mean egg per trap (F=9.85, P<0.001), where filter paper exhibited the largest coefficient in magnitude (-0.1698), indicating a strong negative correlation with OI and mean eggs per trap (-2.445) while white fabric showed a strong positive co-efficient magnitude with OI (0.1108) and mean egg per trap (1.605). According to Spearman's rank correlation, the rainfall did not have a statistically significant effect on the number of eggs collected or the OI. The study suggested that fabric ovistrips colored white combined with rainwater or tap water, make ovitraps highly effective for Aedes vector surveillance, while the currently used filter paper ovistrip having a negative effect on the egg number laid.