Absence of dihydropteroate synthase mutations in Pneumocystis jirovecii from Brazilian AIDS patients.

Several studies from developed countries have documented the association between trimethoprim-sulfamethoxazole prophylaxis failure and mutations in the Pneumocystis jirovecii gene coding for dihydropteroate synthase (DHPS). DNA was extracted from Giemsa-stained smears of 70 patients with P. jirovecii pneumonia seen in Porto Alegre, Brazil, from 1997 to 2004.

Umbilical cord-blood infections with Plasmodium falciparum malaria are acquired antenatally in Kenya.

Background: It is unknown whether the presence of Plasmodium falciparum malaria parasites in umbilical cord blood denotes infection acquired antenatally or contamination with infected maternal blood at delivery.

Methods: Parasites were quantified by real-time quantitative polymerase chain reaction (RTQ-PCR) and were genotyped in paired maternal- and cord-blood samples obtained from 632 pregnant Kenyan women and their newborns. Placental alkaline phosphatase (PLAP) and polyclonal immunoglobulin E levels were also quantified in paired maternal- and cord-blood samples, as markers of admixture of maternal blood with cord blood.

Sensitivity and specificity of nested and real-time PCR for the detection of Pneumocystis jiroveci in clinical specimens.

A polymerase chain reaction (PCR)-based test for Pneumocystis jiroveci (formerly Pneumocystis carinii f. sp. hominis) might be an alternative to histologic diagnoses of P.

Maternal-fetal microtransfusions and HIV-1 mother-to-child transmission in Malawi.

Background: Between 25% and 35% of infants born to HIV-infected mothers become HIV-1 infected. One potential route of mother-to-child transmission (MTCT) could be through a breakdown in the placental barrier (i.e.

Mutations associated with sulfadoxine-pyrimethamine and chlorproguanil resistance in Plasmodium falciparum isolates from Blantyre, Malawi.

We conducted a prevalence study of mutations in Plasmodium falciparum that are associated with antifolate resistance in Blantyre, Malawi. The dihydrofolate reductase 164-Leu mutation, which confers resistance to both pyrimethamine and chlorproguanil, was found in 4.7% of the samples.

Malaria during pregnancy and foetal haematological status in Blantyre, Malawi.

Background: Although maternal anaemia often stems from malaria infection during pregnancy, its effects on foetal haemoglobin levels are not straightforward. Lower-than-expected cord haemoglobin values in malarious versus non-malarious regions were noted by one review, which hypothesized they resulted from foetal immune activation to maternal malaria. This study addressed this idea by examining cord haemoglobin levels in relation to maternal malaria, anaemia, and markers of foetal immune activation.

Effects of HIV-1 serostatus, HIV-1 RNA concentration, and CD4 cell count on the incidence of malaria infection in a cohort of adults in rural Malawi.

Background: To assess the effects of human immunodeficiency virus (HIV) infection on susceptibility to malaria, we compared the incidence rates of malaria by HIV type 1 (HIV-1) serostatus, baseline blood HIV-1 RNA concentration, and baseline CD4 cell count, over the course of a malaria season.

Methods: We followed a cohort of 349 adults in Malawi. For the 224 HIV-1-seropositive adults (64% of the cohort), we measured HIV-1 RNA concentration (n=187) and CD4 cell count (n=184) at baseline.

Measuring allelic heterogeneity in Plasmodium falciparum by a heteroduplex tracking assay.

We developed a novel Plasmodium falciparum genotyping strategy based on the heteroduplex tracking assay (HTA) method commonly used to genotype viruses. Because it can detect both sequence and size polymorphisms, we hypothesized that HTA is more sensitive than current methods. To test this hypothesis, we compared the ability of HTA and a nested polymerase chain reaction (PCR) to detect genetic diversity in 17 Thai samples.

Efficacy of DB289 in Thai patients with Plasmodium vivax or acute, uncomplicated Plasmodium falciparum infections.

Background: DB289 is the orally active prodrug of the diamidine DB75, which was developed for the treatment of human African trypanosomiasis.

Methods: We tested the safety and efficacy of DB289 for the treatment of Plasmodium vivax and acute, uncomplicated P. falciparum infections in an open-label pilot study at the Hospital for Tropical Diseases in Bangkok.

Real-time PCR methods for monitoring antimalarial drug resistance.

Drug-resistant Plasmodium falciparum is a challenge to malaria control programs. Policy makers currently depend on in vivo (and, sometimes, in vitro) resistance testing to set treatment guidelines. Molecular markers such as mutations in dhfr, dhps, pfcrt and pfmdr1 represent potential surveillance tools.

pfmdr1 genotyping and in vivo mefloquine resistance on the Thai-Myanmar border.

Molecular markers have been proposed as a method of monitoring malaria drug resistance and could potentially be used to prolong the life span of antimalarial drugs. Single nucleotide polymorphisms (SNPs) in the Plasmodium falciparum gene pfmdr1 and increased gene copy number have been associated with in vitro drug resistance but have not been well studied in vivo. In a prospective cohort study of malaria patients receiving mefloquine treatment on the Thai-Myanmar border, there was no significant association between either pfmdr1 SNPs or in vitro drug sensitivity and mefloquine resistance in vivo.

Analysis of Pneumocystis jirovecii DHPS alleles implicated in sulfamethoxazole resistance using an Escherichia coli model system.

Pneumocystis jirovecii is a major opportunistic pathogen that causes Pneumocystis pneumonia (PCP). Drug treatment failure has been associated epidemiologically with point mutations in the gene for dihydropteroate synthase which is part of a gene that encodes three covalently linked enzymes involved in folic acid synthesis (FAS). The evaluation of whether mutations found in P.

Cytochrome b mutations that modify the ubiquinol-binding pocket of the cytochrome bc1 complex and confer anti-malarial drug resistance in Saccharomyces cerevisiae.

Atovaquone is a new anti-malarial agent that specifically targets the cytochrome bc1 complex and inhibits parasite respiration. A growing number of failures of this drug in the treatment of malaria have been genetically linked to point mutations in the mitochondrial cytochrome b gene. To better understand the molecular basis of atovaquone resistance in malaria, we introduced five of these mutations, including the most prevalent variant found in Plasmodium falciparum (Y268S), into the cytochrome b gene of the budding yeast Saccharomyces cerevisiae and thus obtained cytochrome bc1 complexes resistant to inhibition by atovaquone.

Mefloquine--its 20 years in the Thai Malaria Control Program.

Due to the deteriorating efficacy of sulfadoxine-pyrimethamine (SP or Fansidar), from the mid-1970s the Thai Malaria Control Program was actively involved in testing potential replacement drugs to be used as the primary therapy for falciparum malaria in Thailand. In 1983, a large-scale field trial of mefloquine, a long-acting antimalarial drug known for its efficacy against chloroquine- and SP-resistant Plasmodium falciparum, was initiated on the Thai-Cambodian border. The study enrolled over 60,000 patients and eventually led to the formal establishment of mefloquine as the first line drug for the treatment of uncomplicated falciparum malaria in the country.

Mutations in the Pneumocystis jirovecii DHPS gene confer cross-resistance to sulfa drugs.

Pneumocystis jirovecii is a major opportunistic pathogen that causes Pneumocystis pneumonia (PCP) and results in a high degree of mortality in immunocompromised individuals. The drug of choice for PCP is typically sulfamethoxazole (SMX) or dapsone in conjunction with trimethoprim. Drug treatment failure and sulfa drug resistance have been implicated epidemiologically with point mutations in dihydropteroate synthase (DHPS) of P.

Prevalence of pfcrt mutations in Congolese and Malawian Plasmodium falciparum isolates as determined by a new Taqman assay.

A real-time PCR assay was developed to detect the K76T point mutation in the Plasmodium falciparum putative chloroquine resistance transporter gene. The assay was used with malaria positive clinical isolates from Rutshuru in the eastern part of the Democratic Republic of the Congo (DRC) and from Malawi. The K76T mutation was found in 52/56 (93%) clinical isolates from the DRC, where chloroquine resistance is high, but in none of the 12 isolates tested from Malawi where chloroquine is now rarely used.

Cloning of the Pneumocystis jirovecii trifunctional FAS gene and complementation of its DHPS activity in Escherichia coli.

Pneumocystis pneumonia or PCP is caused by Pneumocystis jirovecii, an obligate parasite of the human lung. In this study P. jirovecii genomic sequence encoding FAS, a trifunctional protein including dihydroneopterin aldolase (DHNA), hydroxymethyldihydropterin pyrophosphokinase (PPPK) and dihydropteroate synthase (DHPS) were identified by PCR amplification from fixed broncheolar lavage samples from patients having Pneumocystis pneumonia.

Sulfa use, dihydropteroate synthase mutations, and Pneumocystis jirovecii pneumonia.

A systematic review was conducted to examine the associations in Pneumocystis jirovecii pneumonia (PCP) patients between dihydropteroate synthase (DHPS) mutations and sulfa or sulfone (sulfa) prophylaxis and between DHPS mutations and sulfa treatment outcome. Selection criteria included study populations composed entirely of PCP patients and mutation or treatment outcome results for all patients, regardless of exposure status. Based on 13 studies, the risk of developing DHPS mutations is higher for PCP patients receiving sulfa prophylaxis than for PCP patients not receiving sulfa prophylaxis (p < 0.

Prevalence of dihydropteroate synthase mutants in HIV-infected South African children with Pneumocystis jiroveci pneumonia.

Background: Pneumocystis jiroveci (formerly Pneumocystis carinii) pneumonia (PCP) is a major cause of mortality in human immunodeficiency virus (HIV)-infected infants in Africa, but the prevalence of mutations in the gene encoding dihydropteroate synthase (DHPS) in isolates from Africa has not been reported.

Methods: This study investigated the prevalence of DHPS mutations in P. jiroveci isolates from South African HIV-infected children with PCP by amplifying DNA using 2 different polymerase chain reactions.