Improving the Specificity of Plasmodium falciparum Malaria Diagnosis in High-Transmission Settings with a Two-Step Rapid Diagnostic Test and Microscopy Algorithm.

Poor specificity may negatively impact rapid diagnostic test (RDT)-based diagnostic strategies for malaria. We performed real-time PCR on a subset of subjects who had undergone diagnostic testing with a multiple-antigen (histidine-rich protein 2 and pan-lactate dehydrogenase pLDH [HRP2/pLDH]) RDT and microscopy. We determined the sensitivity and specificity of the RDT in comparison to results of PCR for the detection of Plasmodium falciparum malaria. We developed and evaluated a two-step algorithm utilizing the multiple-antigen RDT to screen patients, followed by confirmatory microscopy for those individuals with HRP2-positive (HRP2+)/pLDH-negative (pLDH-) results. In total, dried blood spots (DBS) were collected from 276 individuals. There were 124 (44.9%) individuals with an HRP2+/pLDH+ result, 94 (34.1%) with an HRP2+/pLDH- result, and 58 (21%) with a negative RDT result. The sensitivity and specificity of the RDT compared to results with real-time PCR were 99.4% (95% confidence interval [CI], 95.9 to 100.0%) and 46.7% (95% CI, 37.7 to 55.9%), respectively. Of the 94 HRP2+/pLDH- results, only 32 (34.0%) and 35 (37.2%) were positive by microscopy and PCR, respectively. The sensitivity and specificity of the two-step algorithm compared to results with real-time PCR were 95.5% (95% CI, 90.5 to 98.0%) and 91.0% (95% CI, 84.1 to 95.2), respectively. HRP2 antigen bands demonstrated poor specificity for the diagnosis of malaria compared to that of real-time PCR in a high-transmission setting. The most likely explanation for this finding is the persistence of HRP2 antigenemia following treatment of an acute infection. The two-step diagnostic algorithm utilizing microscopy as a confirmatory test for indeterminate HRP2+/pLDH- results showed significantly improved specificity with little loss of sensitivity in a high-transmission setting.

Antibacterial, antioxidant, and sun protection potential of selected ethno medicinal plants used for skin infections in Uganda.

BACKGROUND: Rural populations in Uganda rely heavily on medicinal plants for the treatment of bacterial skin infections. However, the efficacy of these medicinal plants for their pharmacological action is not known. The study aimed at evaluating the antibacterial, antioxidant, and sun protection potential of Spermacoce princeae, Psorospermum febrifugum, Plectranthus caespitosus, and Erlangea tomentosa extracts. METHODS: The plant samples were extracted by maceration sequentially using hexane, dichloromethane, ethyl acetate, methanol, and distilled water. Antibacterial activity of each extract was carried out using an agar well diffusion assay against Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonie, Streptococcus pyogenes, and Salmonella typhi. Acute dermal toxicity of the aqueous extract of S. princeae and P. febrifugum, and E. tomentosa was assessed in young adult healthy Wistar albino rats at a dose of 8000 and 10,000 mg/kg body weight. The antioxidant activity of each extract was carried out using a 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay. The sun protection factor was determined using Shimadzu UltraViolet-Visible double beam spectrophotometer between 290 and 320 nm. RESULTS: The plant extracts showed good antibacterial activity against the tested bacterial strains with minimum inhibitory concentration (MIC) ranging between 3.12 and 12.5 mg/ml. There was no significant change in the levels of creatinine, alanine aminotransferase, and aspartate aminotransferase in the rats even at a higher dose of 10,000 mg/kg, which was related to the results of biochemical analysis of the blood samples from the treated and control groups. The aqueous and methanol extracts of S. princeae showed potential antioxidant properties, with half maximal inhibitory concentration (IC50) values of 59.82 and 61.20 µg/ml respectively. The organic and aqueous extracts of P. caespitosus showed high levels of protection against Ultraviolet light with sun protection potential values ranging between 30.67 and 37.84. CONCLUSIONS: The study demonstrated that the selected medicinal plants possessed good antibacterial, antioxidant, and sun protection properties. Therefore, the plants are alternative sources of antibacterial, antioxidant, and sun protection agents in managing bacterial skin infections.