Capacity ofHistoplasma capsulatumto Survive the Composting Process

Abstract

Histoplasma capsulatum (H. capsulatum) is a thermal-dimorphic fungus, the causal agent of histoplasmosis. Its presence in the environment is related with chicken manure due to their high nitrogen and phosphorus content. In Colombia, chicken manure is the most used raw material in the composting process; however, there is no information about the capacity of H. capsulatum to survive and remain viable in a composted organic fertilizer. To address this question, this study shows three assays based on microbiological culture and the Hc100 nested PCR. First, a composting reactor system was designed to transform organic material under laboratory conditions, and the raw material was inoculated with the fungus. From these reactors, the fungus was not isolated, but its DNA was detected. In the second assay, samples from factories where the DNA of the fungus was previously detected by PCR were analyzed. In the raw material samples, 3 colonies of H. capsulatum were isolated and its DNA was detected. However, after the composting process, neither the fungus was recovered by culture nor DNA was detected. In the third assay, sterilized and nonsterilized organic composted samples were inoculated with H. capsulatum and then evaluated monthly during a year. In both types of samples, the fungus DNA was detected by Hc100 nested PCR during the whole year, but the fungus only grew from sterile samples during the first two months evaluated. In general, the results of the assays showed that H. capsulatum is not able to survive a well-done composting process.

Comparison between Two Molecular Techniques: Nested and Real-Time Polymerase Chain Reaction Targeting 100-kDa Hc Protein for Detection of Histoplasma capsulatum in Environmental Samples

“…Our previous studies demonstrated that properly performed composting can decrease the amount of detectable H. capsulatum in organic fertilizers. 19 Several factors may explain the observed high proportion of positive samples among composted fertilizers in this study. First, it is possible that the highly sensitive 100-kDa real-time PCR assay detects DNA from nonviable fungus, and the positive signal indicates the history of H. capsulatum contamination in the composted fertilizers.…”

“…We evaluated the performances of 100-kDa real-time and Hc100 nested PCR for the detection of H. capsulatum DNA in environmental samples and used these assays to investigate the presence of this fungus in these substrates in Colombia. Our results demonstrated that although both assays considerably outperformed culture, which was only able to detect H. capsulatum in a single sample, 18,19 100-kDa real-time PCR was able to identify 600% more positive samples compared with the Hc100 nested PCR assay. The higher sensitivity of real-time PCR compared with nested PCR was not surprising, given that the real-time PCR assay did not rely on visualization of PCR products on the agarose gel, and therefore, lower concentrations of PCR products could be detected with this method.…”

“…Positive-control samples were environmental samples that had been demonstrated positive for H. capsulatum by Hc100 nested PCR assay ( n = 38) and microbiological culture ( n = 1). 18 , 19 Detection specificity was calculated by using 11 negative-control soils samples from nonendemic areas. To test for the possibility of cross-contamination during sample handling, we tested a sterile distilled-water sample that was processed along with the environmental samples and subjected to the same DNA extraction procedures.…”

Epidemiology of Epizootic Lymphangitis Among Carthorses in Ethiopia

“…In agreement with our observation other authors documented that temperature up 29°C and humidity of 67–87% are favorable for the survival of the mycelial form of the fungus. Rainfall and or humidity can cause maceration of the skin which can easily be traumatized and allow entrance of the fungus into the body of horses ( 18 ). Here a higher humidity but a lower rainfall was associated with an increased risk of epizootic lymphangitis.…”

Occupational Histoplasmosis: Epidemiology and Prevention Measures

“…For example, Histoplasma grows especially well in soil or other environmental material containing large amounts of bird or bat droppings, although this is not a requirement for its presence in the environment. Histoplasma has been detected in some organic fertilizers in Latin America, but more studies are needed to understand whether the fungus can survive commercial fertilizer manufacturing processes [ 23 , 24 ].…”