BackgroundIn Mexico, primary pulmonary histoplasmosis is the most relevant clinical form of the disease. The geographical distribution of specific strains of Histoplasma capsulatum circulating in Mexico has not been fully established. Outbreaks must be reported in order to have current, updated information on this disease, identifying new endemic areas, manner of exposure to the fungi, and molecular characterization of the causative agents. We report a recent outbreak of histoplasmosis in treasure hunters and the molecular characterization of two isolates obtained from these patients.MethodsSix patients admitted to the National Institute of Respiratory Diseases (INER) in Mexico City presented severe respiratory symptoms suggestive of histoplasmosis. They acquired the infection in the Veracruz (VZ) endemic zone. Diagnosis was made by X-ray and Computed tomography (CT), liver function, immunological techniques, and culture. Identification of H. capsulatum isolates was confirmed by using Polymerase chain reaction (PCR) was conducted with a probe from the M antigen, and the isolates were characterized by means of Random amplification of polymorphic DNA (RAPD)-PCR employed the 1253 oligonucleotide and a mixture of oligonucleotides 1281 and 1283. These were compared to eight reference strain isolates from neighboring areas.ResultsX-ray and CT revealed disseminated micronodular images throughout lung parenchyma, as well as bilateral retrocaval, prevascular, subcarinal, and hilar adenopathies, hepatosplenomegaly, and altered liver function tests. Five of the six patients developed disseminated histoplasmosis. Two H. capsulatum strains were isolated. The same band profile was detected in both strains, indicating that both isolates corresponded to the sole H. capsulatum strain. Molecular characterization of the isolates was similar in 100% with the EH-53 Hidalgo human (HG) strain (reference strain integrated into the LAm A clade described for Latin America).ConclusionsThe two isolates appeared to possess the same polymorphic pattern; they are indistinguishable from each other and from EH-53. It is important to remain updated on recent outbreaks of histoplasmosis, the manner of exposure to the fungi, as well as the molecular characterization of the isolates. The severity of cases indicates that this strain is highly virulent and that it is probably prevalent in Hidalgo and Veracruz states.

Antigenic fractions of 100, 50, 37, and 28 kDa obtained through the SDS-PAGE method that were more frequently recognized by anti-Coccidioides antibodies in the sera of coccidioidomycosis patients were selected using western blotting. Subsequently, these bands were sequenced, and the obtained proteins were analysed by BLAST to choose peptides specific for Coccidioides spp. from among the shared aligned sequences of related fungi. A peptide specific for C. immitis was selected from the “GPI anchored serine-threonine rich protein OS C. immitis”, while from the “uncharacterized protein of C. immitis”, we selected a peptide for C. immitis and C. posadasii. These proteins arose from the 100 kDa antigenic fraction. From the protein “fatty acid amide hydrolase 1 of C. posadasii” that was identified from the 50 kDa antigenic fraction, a peptide was selected that recognized C. immitis and C. posadasii. In addition, the analysis of all the peptides (353) of each of the assembled proteins showed that only 35 had 100% identity with proteins of C. immitis and C. posadasii, one had 100% identity with only C. immitis, and one had 100% identity with only C. posadasii. These peptides can be used as diagnostic reagents, vaccines, and antifungals.

Coccidioidin, an extract from the saprophytic mycelial form of Coccidioides spp., has been a very useful antigen preparation both for skin and serological tests for coccidioidomycosis. Unfortunately, coccidioidin is not currently available for skin testing in the United States. Coccidioidin has been produced commercially in Mexico by a vaccine and reagents laboratory of the Mexican Federal Government. It also has been produced at the Microbiology Laboratory of the Faculty of Medicine, Universidad Nacional Autónoma de México exclusively as an antigen for research projects. The objective of the study was to compare both coccidioidins in their reactivity and safety when applied in humans. One hundred and eighty-four volunteers were tested; median age was 33 (range 14-82). When the cutoff point is set in 5 mm, 88 subjects (47.8%) had a positive test for the commercial coccidioidin and 76 (41.3%; CI(95%) 0.50, 1.15; P = 0.20) were positive with the research antigen. Seventy-five subjects were positive for both antigens and 96 were negative for both. Fifty-nine subjects (31.3%) reported an adverse reaction after the application of the antigen; they were mostly very mild local reactions. Mexican research coccidioidin is a safe and reliable antigen that can be used for the detection of coccidioidomycosis infection in mammals.