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Naegleria fowleri is the causative agent of primary amoebic meningoencephalitis, a fatal disease of the central nervous system that is acquired while swimming or diving in freshwater. A cDNA clone designated Mp2C15 obtained from N. fowleri was used as a probe to distinguish N. fowleri from other free-living amoebae. The Mp2C15 probe hybridized to genomic DNA from pathogenic N. fowleri and antigenically related non-pathogenic N. lovaniensis. Mp2C15 was digested with the restriction enzyme XbaI, resulting in two fragments, Mp2C15.G and Mp2C15.P. Four species of Naegleria and four species of Acanthamoeba were examined for reactivity with Mp2C15.P. Mp2C15.P was specific for N. fowleri and was used in the development of a nested PCR assay which is capable of detecting as little as 5 pg of N. fowleri DNA or five intact N. fowleri amoebae. In summary, a rapid, sensitive, and specific assay for the detection of N. fowleri was developed.

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BackgroundExposure to formaldehyde may lead to exacerbation of asthma.ObjectivesOur aim in this study was to investigate whether exposure to a low level (500 μg/m3) of formaldehyde enhances inhaled allergen responses.MethodsTwelve subjects with intermittent asthma and allergy to pollen were exposed, at rest, in a double-blind crossover study to either formaldehyde or purified air for 60 min. The order of exposure to formaldehyde and air-only was randomized, and exposures were separated by 2 weeks. We also performed an allergen inhalation challenge after each exposure. Airway responsiveness to methacholine and lower airway inflammation (induced sputum) were assessed 8 hr after allergen challenge.ResultsThe median dose of allergen producing a 15% decrease in forced expiratory volume in 1 sec (PD15FEV1) was 0.80 IR (index of reactivity) after formaldehyde exposure compared with 0.25 IR after air-only exposure (p = 0.06). Formaldehyde exposure did not affect allergen-induced increase in responsiveness to methacholine (p = 0.42). We found no formaldehyde-associated effect on the airway inflammatory response, in particular the eosinophilic inflammatory response, induced by the allergen challenge 8 hr before.ConclusionIn this study, exposure to 500 μg/m3 formaldehyde had no significant deleterious effect on airway allergen responsiveness of patients with intermittent asthma; we found a trend toward a protective effect.