Epidemiology and Clonality of P marneffei Epidemiology

One of the most significant issues surrounding P. marneffei infections is the source from which infections derive. Given that infections are thought to occur by inhalation of conidia, it is expected that source will be the hyphal form, which can undergo conidiation, growing in the environment as a saprophyte. Despite a number of extensive studies, the ecology of P. marneffei remains obscure. Several studies have suggested that bamboo rats may be an enzootic reservoir for P. marneffei (Chariyalertsak et al., 1996b; Gugnani et al., 2004) and a study using microsatellite typing revealed a genotypic correlation between P. marneffei is isolates from bamboo rats and humans (Fisher et al., 2005). However, the evidence for a zoonotic transmission is still lacking and is unlikely to explain all the cases of infection. Interestingly, infections by Cryptococcus neoformans, the causative agent of cryptococcosis, can be acquired by inhalation of either desiccated spores or yeast cells but aerosolized spores are 100 times more infectious than yeast cells. C. neoformans is readily found in the environment and in a mating-type dependent manner, can undergo monokaryotic fruiting to produce spores (Heitman, 2006 and references therein). Despite extensive sampling, isolation of P. marneffei from soil has seen limited success (Vanittanakom et al., 2006). As with C. neoformans, aerosolized yeast cells originated from patients or rats could be a means of infection by P. marneffei. Yeast cells grown in the laboratory were capable of being phago-cytosed by macrophage in culture, although it was media-dependent (Tongchusak et al., 2004). However, there is no evidence for human-to-human transmission to date. The main risk factors for infections remain associated with an HIV-positive status and an agricultural occupation. P. marneffei infection rates also show a seasonal variation, being more frequent during the rainy season (Chariyalertsak et al., 1996a).

Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

Get My Free Ebook


Post a comment