Comparative assessment of Plasmodium falciparum sensitivity to chloroquine and amodiaquine in vitro

The in vitro sensitivity of Plasmodium falciparum isolates to chloroquine and amodiaquine were assessed in children with symptomatic uncomplicated malaria in Ibadan, Nigeria. The WHO standard in vitro micro-test method was employed for the study. A total of one hundred and two children were admitted into the study. Inhibition of schizont maturation at varying concentration of the study drugs was used as an index for drug activity. Effective concentrations by probit analysis of log dose/response for 50, 90 and 99% (EC50, EC90and EC99) inhibition were 0.37, 2.38 and 5.76 mol/l, respectively, for chloroquine and 0.06, 0.26 and 0.59 mol/l, respectively, for amodiaquine. Forty isolates of P. falciparum were tested for chloroquine sensitivity. Eighty percent (32/40) showed schizont maturation at 1.6 mol/l and were classified as resistant, while 39% (14/36) of isolates tested for amodiaquine matured at 0.4 mol/l and were also classified as resistant. This shows that amodiaquine is significantly more effective than chloroquine. While this data provides no absolute demonstration of chloroquine resistance, it underlies the need for continuous monitoring of the susceptibility of P. falciparum to chloroquine in southwest Nigeria

Establishment of the 1st World Health Organization International Standard for Plasmodium falciparum DNA for nucleic acid amplification technique (NAT)-based assays

BACKGROUND: In order to harmonize results for the detection and quantification of Plasmodium falciparum DNA by nucleic acid amplification technique (NAT)-based assays, a World Health Organization (WHO) collaborative study was performed, evaluating a series of candidate standard preparations. METHODS: Fourteen laboratories from 10 different countries participated in the collaborative study. Four candidate preparations based upon blood samples parasitaemic for P. falciparum were evaluated in the study. Sample AA was lyophilized, whilst samples BB, CC and DD were liquid/frozen preparations. The candidate standards were tested by each laboratory at a range of dilutions in four independent assays, using both qualitative and quantitative NAT-based assays. The results were collated and analysed statistically. RESULTS: Twenty sets of data were returned from the participating laboratories and used to determine the mean P. falciparum DNA content for each sample. The mean log10 "equivalents"/ml were 8.51 for sample AA, 8.45 for sample BB, 8.35 for sample CC, and 5.51 for sample DD. The freeze-dried preparation AA, was examined by accelerated thermal degradation studies and found to be highly stable. CONCLUSION: On the basis of the collaborative study, the freeze-dried material, AA (NIBSC code No. 04/176) was established as the 1st WHO International Standard for P. falciparum DNA NAT-based assays and has been assigned a potency of 10(9) International Units (IU) per ml. Each vial contains 5 x 10(8) IU, equivalent to 0.5 ml of material after reconstitution

Hepatitis C Virus Infection May Lead to Slower Emergence of P. falciparum in Blood

International audienceBACKGROUND: Areas endemic for Plasmodium falciparum, hepatitis B virus (HBV) and hepatitis C virus (HCV) overlap in many parts of sub-Saharan Africa. HBV and HCV infections develop in the liver, where takes place the first development stage of P. falciparum before its further spread in blood. The complex mechanisms involved in the development of hepatitis may potentially influence the development of the liver stage of malaria parasites. Understanding the molecular mechanisms of these interactions could provide new pathophysiological insights for treatment strategies in Malaria. METHODOLOGY: We studied a cohort of 319 individuals living in a village where the three infections are prevalent. The patients were initially given a curative antimalarial treatment and were then monitored for the emergence of asexual P. falciparum forms in blood, fortnightly for one year, by microscopy and polymerase chain reaction. PRINCIPAL FINDINGS: At inclusion, 65 (20.4%) subjects had detectable malaria parasites in blood, 36 (11.3%) were HBV chronic carriers, and 61 (18.9%) were HCV chronic carriers. During follow-up, asexual P. falciparum forms were detected in the blood of 203 patients. The median time to P. falciparum emergence in blood was respectively 140 and 120 days in HBV- and HBV+ individuals, and 135 and 224 days in HCV- and HCV+ individuals. HCV carriage was associated with delayed emergence of asexual P. falciparum forms in blood relative to patients without HCV infection. CONCLUSIONS: This pilot study represents first tentative evidence of a potential epidemiological interaction between HBV, HCV and P. falciparum infections. Age is an important confounding factor in this setting however multivariate analysis points to an interaction between P. falciparum and HCV at the hepatic level with a slower emergence of P. falciparum in HCV chronic carriers. More in depth analysis are necessary to unravel the basis of hepatic interactions between these two pathogens, which could help in identifying new therapeutic approaches against malaria

The Use of Helicobacter Pylori Stool Antigen Test for the Diagnosis of Helicobacter Pylori in Lagos, Nigeria

Objectives: This study was carried out to screen the use of Helicobacter pylori stool antigen (HpSA) tests for diagnosis and monitoring of H pylori in Nigeria. Methods: Seven hundred and forty participants were enrolled after informed consent was obtained, while 83 came back for a post-eradication test. The stool samples were taken from the patients at endoscopy and tested for HpSA. Results: The proportion of patients that were positive at the pretest, 520 (70.3%) was significantly higher (Fisher’s exact p = 0.001) than those positive at the post-test, 44 (53%). There was a significant difference (F = 4.106, p = 0.043) between the mean age of those that came for the pretest (40.0 ± 14.5 years) and those that came for the post-test, 43.6 ± 11.6 years. More males than females had the tendency to come back for a post-eradication test. Conclusion: Although potential bias was introduced during this study, HpSA using monoclonal antibody could still be used for diagnosis and monitoring of H pylori in Nigeria. Keywords: Helicobacter pylori, stool antigen test "El uso del test de Antígeno en Heces para el Diagnóstico de la Infección por Helicobacter pylori en Lagos, Nigeria" RESUMEN Objetivos: Este estudio se llevó a cabo con el propósito de examinar el uso del test de antígeno en heces (HpSA) para el diagnóstico y monitoreo de Helicobacter pylori en Nigeria Método: Tras obtener su consentimiento informado, se enrolaron ciento cuarenta participantes, mientras que 83 regresaron para un test de post-erradicación. Las muestras de heces fueron tomadas de pacientes en endoscopia e investigadas en busca de HpSA. Resultados: La proporción de pacientes que resultaron positivos en el test previo, 520 (70.3%) fue significativamente mayor (Test exacto de Fisher p = 0.001) que la de los que resultaron positivos en el test posterior, 44(53%). Hubo una diferencia significativa (F = 4.106, p = 0.043) entre la edad promedio de los que vinieron al test previo (40.0 ± 14.5 años) y la de aquellos que vinieron al test posterior, 43.6 ± 11.6 años. Más varones que hembras mostraron tendencia a regresar al test de post-erradicación. Conclusión: Aunque un sesgo potencial fue introducido en este estudio, HpSA con anticuerpos monoclonales podría todavía usarse para el diagnóstico y monitoreo de H pylori en Nigeria. Palabras claves: Helicobacter pylori, prueba de antígeno en hece