IgM in human immunity to Plasmodium falciparum malaria.

Most studies on human immunity to malaria have focused on the roles of immunoglobulin G (IgG), whereas the roles of IgM remain undefined. Analyzing multiple human cohorts to assess the dynamics of malaria-specific IgM during experimentally induced and naturally acquired malaria, we identified IgM activity against blood-stage parasites. We found that merozoite-specific IgM appears rapidly in Plasmodium falciparum infection and is prominent during malaria in children and adults with lifetime exposure, together with IgG. Unexpectedly, IgM persisted for extended periods of time; we found no difference in decay of merozoite-specific IgM over time compared to that of IgG. IgM blocked merozoite invasion of red blood cells in a complement-dependent manner. IgM was also associated with significantly reduced risk of clinical malaria in a longitudinal cohort of children. These findings suggest that merozoite-specific IgM is an important functional and long-lived antibody response targeting blood-stage malaria parasites that contributes to malaria immunity.

Quantitative detection of viable helminth ova from raw wastewater, human feces, and environmental soil samples using novel PMA-qPCR methods.

In this study, we have evaluated the efficacy of propidium monoazide quantitative polymerase chain reaction (PMA-qPCR) to differentiate between viable and non-viable Ancylostoma caninum ova. The newly developed method was validated using raw wastewater seeded with known numbers of A. caninum ova. Results of this study confirmed that PMA-qPCR has resulted in average of 88 % reduction (P < 0.05) in gene copy numbers for 50 % viable +50 % non-viable when compared with 100 % viable ova. A reduction of 100 % in gene copies was observed for 100 % non-viable ova when compared with 100 % viable ova. Similar reductions (79-80 %) in gene copies were observed for A. caninum ova-seeded raw wastewater samples (n = 18) collected from wastewater treatment plants (WWTPs) A and B. The newly developed PMA-qPCR method was applied to determine the viable ova of different helminths (A. caninum, A. duodenale, Necator americanus and Ascaris lumbricoides) in raw wastewater, human fecal and soil samples. None of the unseeded wastewater samples were positive for the above-mentioned helminths. N. americanus and A. lumbricoides ova were found in unseeded human fecal and soil samples. For the unseeded human fecal samples (1 g), an average gene copy concentration obtained from qPCR and PMA-qPCR was found to be similar (6.8 × 10(5) ± 6.4 × 10(5) and 6.3 × 10(5) ± 4.7 × 10(5)) indicating the presence of viable N. americanus ova. Among the 24 unseeded soil samples tested, only one was positive for A. lumbricoides. The mean gene copy concentration in the positively identified soil sample was 1.0 × 10(5) ± 1.5 × 10(4) (determined by qPCR) compared to 4.9 × 10(4) ± 3.7 × 10(3) (determined by PMA-qPCR). The newly developed PMA-qPCR methods were able to detect viable helminth ova from wastewater and soil samples and could be adapted for health risk assessment.

Crusted scabies is associated with increased IL-17 secretion by skin T cells.

Scabies is an ectoparasitic infestation by the mite Sarcoptes scabiei. Although commonly self-limiting, a fraction of patients develop severely debilitating crusted scabies. The immune mechanisms underlying the development of crusted scabies are unclear, and undertaking longitudinal infection studies in humans is difficult. We utilized a porcine model to compare cellular immune responses in peripheral blood and skin of pigs with different clinical manifestations of scabies (n = 12), and in uninfected controls (n = 6). Although clinical symptoms were not evident until at least 4 weeks post-infestation, the numbers of peripheral IFNγ-secreting CD4(+) T cells and γδ T cells increased in infected pigs from week 1 post-infestation. γδ T cells remained increased in the blood at week 15 post-infestation. At week 15, skin cell infiltrates from pigs with crusted scabies had significantly higher CD8(+) T cell, γδ T cell and IL-17(+) cell numbers than those with ordinary scabies. Peripheral IL-17 levels were not increased, suggesting that localized skin IL-17-secreting T cells may play a critical role in the pathogenesis of crusted scabies development. Given the potential of anti-IL-17 immunotherapy demonstrated for other inflammatory skin diseases, this study may provide a novel therapeutic avenue for patients with recurrent crusted scabies.

Strategies for the storage of Ancylostoma caninum third-stage larvae.

Although cryopreservation protocols for storage of hookworm larvae have been described, the circumstances under which the technique is necessary to ensure larval survival are not well defined. The motility of infective-stage larvae (as judged by observation) and their ability to migrate through canine skin in vitro were measured over a 7-mo period in worms held at room temperature and worms that had been cryopreserved at the start of the experiment. Cryopreserved worms showed motility and migration proportions of 45.6-48.0% and 26.8- 34.0%, respectively, throughout the experiment, compared with percentages of 92.7 and 84.1%, respectively, in the original fresh worms. Larvae held at room temperature showed a gradual decrease in motility and migration ability over the experimental period. Motility and migratory ability of cryopreserved larvae was only significantly higher (P < 0.01) than room temperature-stored larvae from 4 and 5 mo onward, respectively.

HIV and malaria co-infection: interactions and consequences of chemotherapy.

The global epidemiology of HIV/AIDS and malaria overlap because a significant number of HIV-infected individuals live in regions with different levels of malaria transmission. Although the consequences of co-infection with HIV and malaria parasites are not fully understood, available evidence suggests that the infections act synergistically and together result in worse outcomes. The importance of understanding chemotherapeutic interactions during malaria and HIV co-infection is now being recognized. We know that some antimalarial drugs have weak antiretroviral effects; however, recent studies have also demonstrated that certain antiretroviral agents can inhibit malaria-parasite growth. Here, we discuss recent findings on the impact of HIV/AIDS and malaria co-infection and the possible roles of chemotherapy in improving the treatment of these diseases.

Stronger activity of human immunodeficiency virus type 1 protease inhibitors against clinical isolates of Plasmodium vivax than against those of P. falciparum.

Recent studies using laboratory clones have demonstrated that several antiretroviral protease inhibitors (PIs) inhibit the growth of Plasmodium falciparum at concentrations that may be of clinical significance, especially during human immunodeficiency virus type 1 (HIV-1) and malaria coinfection. Using clinical isolates, we now demonstrate the in vitro effectiveness of two HIV-1 aspartic PIs, saquinavir (SQV) and ritonavir (RTV), against P. vivax (n = 30) and P. falciparum (n = 20) from populations subjected to high levels of mefloquine and artesunate pressure on the Thailand-Myanmar border. The median 50% inhibitory concentration values of P. vivax to RTV and SQV were 2,233 nM (range, 732 to 7,738 nM) and 4,230 nM (range, 1,326 to 8,452 nM), respectively, both within the therapeutic concentration range commonly found for patients treated with these PIs. RTV was fourfold more effective at inhibiting P. vivax than it was at inhibiting P. falciparum, compared to a twofold difference in SQV sensitivity. An increased P. falciparum mdr1 copy number was present in 33% (3/9) of isolates and that of P. vivax mdr1 was present in 9% of isolates (2/22), but neither was associated with PI sensitivity. The inter-Plasmodium sp. variations in PI sensitivity indicate key differences between P. vivax and P. falciparum. PI-containing antiretroviral regimens may demonstrate prophylactic activity against both vivax and falciparum malaria in HIV-infected patients who reside in areas where multidrug-resistant P. vivax or P. falciparum is found.

Skin infections among Indigenous Australians in an urban setting in far North Queensland.

Skin infections are highly prevalent in many Australian Aboriginal communities. This study aimed to determine the prevalence of group A streptococcus (GAS) and Staphylococcus aureus in skin sores of Indigenous people living in an urban setting. We undertook a cross-sectional study of 173 children and youths attending the Wuchopperen Clinic (Cairns) for treatment of skin infections. Participants were interviewed using a structured questionnaire, and a skin lesion swab obtained. The median age was 5.3 years, with 42% identifying themselves as Torres Strait Islanders and 34% as Aboriginal. Impetigo (65%) was the most frequent diagnosis reported followed by scabies (19%); 79% of the lesions had erythema and 70% had exudate. Of 118 lesions, 114 were positive for pathogenic bacteria, with GAS isolated in 84 cases and S. aureus in 92; both these species were recovered from 63 lesions. Significant diversity of emm-types of GAS was associated with skin lesions in Indigenous patients (22 emm-types identified). Fifteen of the 92 S. aureus isolates were suggestive of being community-acquired on the basis of antimicrobial susceptibility profile and nine of these strains were co-cultured from nine lesions. These results have implications for future changes of antibiotic policies for the treatment of skin infections in this population.

Single nucleotide polymorphism (SNP) markers for benzimidazole resistance in veterinary nematodes.

Resistance to the benzimidazole class of anthelmintics in nematodes of veterinary importance has a long history. Research into the mechanisms responsible for this resistance is subsequently at a more advanced stage than for other classes of anthelmintics. The principal mechanism of resistance to benzimidazoles is likely to involve changes in the primary structure of beta-tubulins, the building blocks of microtubules. Specifically, point mutations in the beta-tubulin isotype 1 gene leading to amino acid substitutions in codons 167, 198, and 200 of the protein have been associated with resistance in nematodes. These single nucleotide polymorphisms offer a means of detecting the presence of resistance within populations. In this mini-review, we focus on the prevalence and importance of these polymorphisms in three groups of nematodes: trichostrongylids, cyathostomins, and hookworms. A brief overview of existing strategies for genotyping single nucleotide polymorphisms is also presented. The CARS initiative hopes to exploit these known polymorphisms to further our understanding of the phenomenon of BZ resistance.

Malaria in the post-genomics era: light at the end of the tunnel or just another train?

Malaria remains the third leading cause of death attributable to an infectious disease worldwide, with an estimated death toll of over 2 million per year, predominately in sub-Saharan Africa. The first serious attempt to eradicate this disease was unsuccessful, and 50 years later in 1998 a second programme coined "roll back malaria" was started. While this programme is at present unlikely to reach its stated aims, the completion of the genome sequencing projects on the human host, the mosquito vector, and the malaria parasite offers new hope. It is probable that the burden of disease caused by the most malignant form of the parasite Plasmodium falciparum can be, if not eliminated, then effectively suppressed within a generation through new and novel treatments aimed at all three arms of malaria control.

Field evaluation of anthelmintic drug sensitivity using in vitro egg hatch and larval motility assays with Necator americanus recovered from human clinical isolates.

A field-applicable assay for testing anthelmintic sensitivity is required to monitor for anthelmintic resistance. We undertook a study to evaluate the ability of three in vitro assay systems to define drug sensitivity of clinical isolates of the human hookworm parasite Necator americanus recovered from children resident in a village in Madang Province, Papua New Guinea. The assays entailed observation of drug effects on egg hatch (EHA), larval development (LDA), and motility of infective stage larvae (LMA). The egg hatch assay proved the best method for assessing the response to benzimidazole anthelmintics, while the larval motility assay was suitable for assessing the response to ivermectin. The performance of the larval development assay was unsatisfactory on account of interference caused by contaminating bacteria. A simple protocol was developed whereby stool samples were subdivided and used for immediate egg recovery, as well as for faecal culture, in order to provide eggs and infective larvae, respectively, for use in the egg hatch assay and larval motility assay systems. While the assays proved effective in quantifying drug sensitivity in larvae of the drug-susceptible hookworms examined in this study, their ability to indicate drug resistance in larval or adult hookworms remains to be determined.

An in vitro larval motility assay to determine anthelmintic sensitivity for human hookworm and Strongyloides species.

With the implementation of programs to control lymphatic filariasis and soil-transmitted helminths using broad spectrum anthelmintics, including albendazole and ivermectin, there is a need to develop an in vitro assay for detection of drug resistance. This report describes an in vitro assay for measuring the effects of ivermectin and benzimidazoles on the motility of larvae of the hookworm species Ancylostoma ceylanicum, A. caninum, and Necator americanus, and Strongyloides species including Strongyloides stercoralis, and S. ratti. A dose-response relationship was demonstrated with each of the parasite species, with distinct differences observed between the various species. In pilot field testing of the assay with N. americanus larvae recovered from human fecal samples, a dose-response relationship was observed with ivermectin. While the assay has demonstrated the ability to determine drug responsiveness, its usefulness in resistance detection will require correlation with the clinical outcome among individuals infected with parasite strains showing different drug sensitivities.

Scabies: more than just an irritation.

Human scabies, caused by skin infestation with the arthropod mite, Sarcoptes scabiei, typically results in a papular, intensely pruritic eruption involving the interdigital spaces, and flexure creases. Recent research has led to a reassessment of the morbidity attributable to this parasite in endemic communities, particularly resulting from secondary skin sepsis and postinfective complications including glomerulonephritis. This has led to studies of the benefits of community based control programmes, and to concerns regarding the emergence of drug resistance when such strategies are employed. The renewed research interest into the biology of this infection has resulted in the application of molecular tools. This has established that canine and human scabies populations are genetically distinct, a finding with major implications for the formulation of public health control policies. Further research is needed to increase understanding of drug resistance, and to identify new drug targets and potential vaccine candidates.

A Phase II trial of docetaxel and cisplatin in patients with recurrent or metastatic nasopharyngeal carcinoma.

UNLABELLED: A Phase II study was conducted to determine the efficacy and toxicity of the combination of docetaxel and cisplatin, in patients with recurrent or metastatic nasopharyngeal carcinoma (NPC). Nine patients (median age 39 years) with NPC were enrolled, none had prior chemotherapy for their recurrent or metastatic disease. Docetaxel was administered as a 1-h intravenous infusion at a dose of 75 mg/m(2) on day 1; cisplatin was administered at a dose of 75 mg/m(2) on day 1, immediately after docetaxel. Treatment was repeated every 3 weeks. The primary endpoint was objective response rate and the secondary endpoints were duration of response, time to progression, and overall survival. A total of 45 chemotherapy cycles were administered. In an intention-to-treat analysis two patients (22%, 95% confidence interval (CI): 3-60%) achieved a partial response. The median duration of response was 4.1 months, the median time to progression 8.4 months and the overall survival at 1 year from start of treatment was 76%. Grade 3-4 neutropenia was observed in all (100%) patients over 93% of the treatment cycles, and in three cases this was complicated by fever. Other toxicities were mild. CONCLUSIONS: The combination of docetaxel and cisplatin has manageable toxicity but little efficacy as first-line treatment in patients with recurrent or metastatic NPC. In view of the low response rate, accrual was terminated and the trial was aborted.

Evaluation of clinical guidelines for the management of Staphylococcus aureus bacteraemia.

BACKGROUND: While treatment guidelines have been developed to guide the management of Staphylococcus aureus bacteraemia, there is a need to validate these guidelines in different clinical settings and to relate the effect of compliance to clinical outcome. AIMS: To assess the impact of adherence to treatment guidelines on clinical outcome and to explore the role of transoesophageal echocardiography (TOE) in risk stratification. METHODS: We undertook a 2-year mixed retrospective and prospective study of all cases of S. aureus bacteraemia at Fremantle Hospital, documenting the clinical and microbiological features of each case, the results of echocardiography, adherence with published clinical guidelines and clinical outcome. RESULTS: Failure to comply with guidelines was observed in 41% (38 of 93) of cases, the majority receiving abbreviated treatment. An increased rate of relapse was observed among patients who received inadequate therapy (5/38 vs 1/55; P= 0.04). Ten of 28 eligible patients underwent TOE and the test led to significant changes in management in two of those cases. CONCLUSIONS: While non-adherence with clinical guidelines was associated with an increased risk of relapse, the role of TOE in risk stratification was limited by factors including cost, limited acceptance of the test and the need for prolonged therapy for other indications.

Could tourist boots act as vectors for disease transmission in Antarctica?

BACKGROUND: Over the last decade there has been a rapid increase in the number of visitors landing at wildlife sites on the Antarctic continent, and concern has been raised that tourists may transmit important pathogens to or between wildlife colonies. The aim of this study was to determine if tourist activities pose a potential threat to Antarctic wildlife, or possibly to human populations through carriage of pathogens on boots. METHODS: In two trips conducted to Antarctica in the summer season of 2000/2001, swabs were collected from tourist boots: prior to landing, to determine baseline level of bacterial flora on the boots (A isolates); immediately on return to the ship, to quantify the level of contamination (B isolates); and after the boots were washed in seawater to determine the recovery of the organisms after cleaning (C isolates). Swabs were cultured for coliforms, and isolates identified using the API system. RESULTS: Twenty organisms resembling coliforms were isolated from 15 of 72 pairs of boots. Two isolates were recovered from group A, 4 from group B, and 14 from group C. Of these 20 isolates, 11 could be identified using the API identification method. The remaining 9 isolates all produced an unknown but identical profile number. CONCLUSION: These results indicate that current practices for cleaning the boots of tourists visiting Antarctic wildlife colonies may not be sufficient to prevent the transmission of pathogens, and indicate that further studies are needed to define the best method of disinfection.

Caffeine-induced cardiac arrhythmia: an unrecognised danger of healthfood products.

We describe a 25-year-old woman with pre-existing mitral valve prolapse who developed intractable ventricular fibrillation after consuming a "natural energy" guarana health drink containing a high concentration of caffeine. This case highlights the need for adequate labelling and regulation of such products.

Towards the eradication of hookworm in an isolated Australian community.

Hookworm (Ancylostoma duodenale) and other enteric parasites such as Giardia and Hymenolepis are common in Aboriginal communities in northem Australia, and their presence is associated with iron deficiency, anaemia, and failure to thrive. We report the outcome of a sustained, community-based control programme that used regular albendazole in one isolated community. Whereas hookworm has been effectively controlled by the programme, no sustained effect on the prevalence of Giardia and Hymenolepis was seen; the control of these parasites will depend on improvements in health education. This programme might serve as a model for community-based or population-based drug treatment programmes elsewhere.