Molecular characterization of Histoplasma capsulatum isolated from an outbreak in treasure hunters

Abstract

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.

Reevaluation of Commercial Reagents for Detection of Histoplasma capsulatum Antigen in Urine

“…The individual performance characteristics of these methods vary, with their overall clinical utility being largely dependent on disease presentation (localized versus disseminated), level of patient immunosuppression, and symptom duration prior to testing. Briefly, while culture, histopathological examination, and NAAT offer high specificity, the overall sensitivity of these methods is variable, ranging from 10% to Ͼ90%, depending on the disease state, specimen source, and assay methodology (3,(6)(7)(8)(9)(10). Additionally, these three methods often require collection of specimens directly from the site of infection through invasive procedures (e.g., bronchoalveolar lavage [BAL] or biopsy), which may be contraindicated for patients with severe disease.…”

Histoplasmosis: Epidemiology in Latin America

“…According to the reports, primary pulmonary histoplasmosis is the most relevant clinical form of the disease in Mexico [47]. In the period between 1953 and 1997, 102 outbreaks of histoplasmosis (corresponding to 1,444 cases) were reported to the Instituto Nacional de Diagnóstico y Referencia Epidemiológica in Mexico City [15].…”

Diagnostic Methods for Histoplasmosis: Focus on Endemic Countries with Variable Infrastructure Levels

“…In Mexico, histoplasmosis is commonly acquired in bat-infested locations, and outbreaks occur among persons exposed to guano [50, 51]. The few published studies of PDH in Mexico indicate that clinical diagnosis is supported with conventional laboratory tests, including a capillary tube precipitation test (CTP) performed at the National Institute of Diagnosis and Epidemiological Reference (InDRE), the nation’s public health agency [50–52].…”