Biomedical subjects

J B Neilson

Publications and source records attributed to J B Neilson.

3 recordsLinked to original sources

PubMed1979

Cryptococcus neoformans: gastronomic delight of a soil ameba.

During 7 days of incubation in vitro the trophozoite stage of the free-living soil amoeba, Acanthamoeba polyphaga, phagocytized and killed 78-97% of the cells of three strains of Cryptococcus neoformans. With one strain, incubation time was increased to nine days and 99% of the yeast cells were killed. It was calculated that during 4-9 days of incubation a single trophozoite phagocytized and killed a daily average of 84 yeast cells. The lethal effect of A. polyphaga on C. neoformans may represent a biological control mechanism in nature. Some of the surviving cells of C. neoformans developed into colonies containing pseudohyphae; these pseudolhyphal forms may be a biological 'escape hatch'.

Amoeba↗

PubMed1978

Cryptococcus neoformans: pseudohyphal forms surviving culture with Acanthamoeba polyphaga.

During experiments on the gastrointestinal tract as a possible portal of entry for Cryptococcus neoformans, we occasionally observed the free-living amoeba, Acanthamoeba polyphaga, growing in the presence of C. neoformans cultured from mouse feces. Examination of the amoebic trophozoites revealed that they were engorged with yeast cells. Over a period of 2 to 3 weeks of incubation, the amoebae apparently killed most of the yeast cells. Some of the surviving C. neoformans cells formed atypical colonies which contained pseudohyphae. Seven other strains have since been cultured with this amoeba. Pseudohyphal forms were found among the surviving colonies in all strains tested. Virulence studies were performed on one randomly selected pseudohyphal isolate from each of the eight strains of C. neoformans. Pseudohyphal isolates from seven of the eight strains failed to kill mice 30 days after intracranial inoculation. The potential role of soil amoebae in the control of C. neoformans in nature is discussed.

Amoeba↗

PubMed1977

Cryptococcus neoformans: size range of infectious particles from aerosolized soil.

Although cryptococcosis is characterized as a chronic central nervous system disease, it is generally accepted that the lungs are the primary portal of entry for the etiological agent. Despite this, there is a distinct lack of evidence that viable airborne particles of Cryptococcus neoformans are small enough to reach the alveoli. Two encapsulated strains and one nonencapsulated strain of C. neoformans were inoculated into 250-g quantities of sterile soil. Throughout the 0 to 12 weeks of incubation, this soil was aerosolized in a sealed chamber with a Waring blender. Samples of the resultant dust cloud were taken with an Anderson air sampler from which the numbers and sizes of viable airborne particles were determined. Of the viable organisms aspirated into the air sampler, 15% were 0.65 to 2 micron in diameter. As incubation time in soil increased, the size of the particles decreased, and increased numbers of C. neoformans cells 0.65 to 2 micron in diameter were isolated. The presence of viable cells less than 2 micron in soil aerosols indicated that, under certain conditions in nature, C. neoformans cells exist in sizes that are capable of deep lung deposition.

Aerosols↗