EVALUATION OF TWO NESTED PCR-BASED DIAGNOSTIC ASSAYS FOR PLASMODIUM FALCIPARUM INFECTION

  Objective: The majority of malaria cases and deaths are caused by Plasmodium falciparum. The rapid and accurate diagnosis is very important for malaria treatment and control. The aim of this study was to evaluate two nested polymerase chain reaction (PCR)-based methods (protocol A and protocol B) for P. falciparum infection, diagnosis in Thailand.Methods: A total of 90 dried blood spot samples were investigated. The samples composed of P. falciparum-, Plasmodium vivax-infected blood and normal human blood samples. The microscopic examination was used as gold standard.Results: The results showed the sensitivity of 100/83.33%, specificity of 100/100%, and accuracy of 100/94.44% for protocol A and protocol B, respectively. The analytical sensitivity of protocol A and protocol B was 0.625 and 6.25 parasites/μl, respectively. The comparison among microscopic examination, protocol A and protocol B by statistical analysis, found that they were not a significant difference. The agreements between each method were good. The kappa value between protocol A and protocol B was 0.87, protocol A and microscopy was 1.00, and protocol B and microscopy was 0.87.Conclusion: The results demonstrated that protocol A should be used for further development of P. falciparum diagnosis in Thailand, especially in case of low parasitemia such as asymptomatic infection and for screening blood donors

Global gene expression profiling of Plasmodium falciparum in response to the anti-malarial drug pyronaridine

<p>Abstract</p> <p>Background</p> <p>Pyronaridine (PN) and chloroquine (CQ) are structurally related anti-malarial drugs with primarily the same mode of action. However, PN is effective against several multidrug-resistant lines of <it>Plasmodium falciparum</it>, including CQ resistant lines, suggestive of important operational differences between the two drugs.</p> <p>Methods</p> <p>Synchronized trophozoite stage cultures of <it>P. falciparum </it>strain K1 (CQ resistant) were exposed to 50% inhibitory concentrations (IC₅₀) of PN and CQ, and parasites were harvested from culture after 4 and 24 hours exposure. Global transcriptional changes effected by drug treatment were investigated using DNA microarrays.</p> <p>Results</p> <p>After a 4 h drug exposure, PN induced a greater degree of transcriptional perturbation (61 differentially expressed features) than CQ (10 features). More genes were found to respond to 24 h treatments with both drugs, and 461 features were found to be significantly responsive to one or both drugs across all treatment conditions.</p> <p>Filtering was employed to remove features unrelated to primary drug action, specifically features representing genes developmentally regulated, secondary stress/death related processes and sexual stage development. The only significant gene ontologies represented among the 46 remaining features after filtering relate to host exported proteins from multi-gene families.</p> <p>Conclusions</p> <p>The malaria parasite's molecular responses to PN and CQ treatment are similar in terms of the genes and pathways affected. However, PN appears to exert a more rapid response than CQ. The faster action of PN may explain why PN is more efficacious than CQ, particularly against CQ resistant isolates. In agreement with several other microarray studies of drug action on the parasite, it is not possible, however, to discern mechanism of drug action from the drug-responsive genes.</p

Isolation and characterization of a novel podovirus which infects burkholderia pseudomallei

Burkholderia pseudomallei is a saprophytic soil bacterium and the etiological agent that causes melioidosis. It is naturally resistant to many antibiotics and therefore is difficult to treat. Bacteriophages may provide an alternative source of treatment. We have isolated and characterised the bacteriophage ΦBp-AMP1. The phage is a member of the Podoviridae family and has a genome size of ~ 45 Kb. Molecular data based on the gene which encodes for the phage tail tubular protein suggests that the phage is distinct from known phages but related to phages which infect B. thailandensis and Ralstonia spp. The phage ΦBp-AMP1 is the first B. pseudomallei podovirus to be isolated from the environment rather than being induced from a bacterial culture. It has a broad host range within B. pseudomallei and can infect all 11 strains that we tested it on but not related Burkholderia species. It is heat stable for 8 h at 50°C but not stable at 60°C. It may potentially be a useful tool to treat or diagnose B. pseudomallei infections as it can lyse several strains of clinical relevance

Elimination Therapy for the Endemic Malarias

Most malaria diagnosed outside endemic zones occurs in patients experiencing the consequences of what was likely a single infectious bite by an anopheline mosquito. A single species of parasite is nearly always involved and expert opinion on malaria chemotherapy uniformly prescribes species- and stage-specific treatments. However the vast majority of people experiencing malaria, those resident in endemic zones, do so repeatedly and very often with the involvement of two or more species and stages of parasite. Silent forms of these infections—asymptomatic and beyond the reach of diagnostics—may accumulate to form substantial and unchallenged reservoirs of infection. In such settings treating only the species and stage of malaria revealed by diagnosis and not others may not be sensible or appropriate. Developing therapeutic strategies that address all species and stages independently of diagnostic evidence may substantially improve the effectiveness of the control and elimination of endemic malaria

Molecular screening of Plasmodium infections among migrant workers in Thailand

Background & objective: A cross-sectional study was conducted to determine the prevalence of Plasmodiuminfections among migrant workers in Thailand.Methods: A total of 241 migrants at Kanchanaburi, Pathumthani and Nakornpathom provinces of Thailand wererecruited in our surveillance. Blood samples were examined for human malaria parasites by using microscopyand semi-nested multiplex PCR (SnM-PCR).Results: Laboratory diagnosis revealed 6.2% total positive rate. As compared to microscopy (26.7%), SnM-PCRwas more sensitive (93.3%) for malaria. Plasmodium falciparum was predominant than P. vivax (53% : 40%,respectively). The majority of positive cases were from Myanmar workers who had low parasitaemia and withoutsymptoms. The highest prevalence (13.7%) was found among migrant workers from Kanchanaburi province inwestern Thailand.Conclusion: These findings indicate risk of malaria transmission from migrant workers. Malaria surveillanceshould be included in the health-screening program for migrants in Thailand to manage this health risk