The cell block (CB) technique has allowed easy obtainment of samples such as cellular and culture suspensions, to perform specific molecular tests such as immunohistochemistry and in situ hybridization. It has been improved along time, accuracy, and quality of the diagnoses, however, the cost of a commercial gel matrix for the preparation of CB is high and not suitable depending on the situation. The objective of this study is to test agarose as an alternative to the commercial gel matrix in the preparation of Aspergillus fumigatus' CB.

Tropheryma whipplei, the agent of Whipple disease, causes a rare bacterial disease that may be fatal if not treated. The classical form of the disease includes diarrhoea, weight loss, arthritis, endocarditis and neurological manifestations. Genotyping studies done in Europe, Africa and Asia showed high genetic diversity with no correlation between genotypes and clinical features, but contributed to a better understanding of the epidemiology of the disease. More than 70 genotypes have been described. No similar assessment of T. whipplei in the USA and the Caribbean has been performed. In this study, we describe genetic analysis of DNA from histopathological samples obtained from 30 patients from the Americas with Whipple disease and compare the genotypes with those previously identified. Complete genotypes were obtained from 18 patients (60%). Only 4 genotypes were previously described, and 14 were newly reported, confirming the diversity of T. whipplei strains.

Neoplasms occur naturally in invertebrates but are not known to develop in tapeworms. We observed nests of monomorphic, undifferentiated cells in samples from lymph-node and lung biopsies in a man infected with the human immunodeficiency virus (HIV). The morphologic features and invasive behavior of the cells were characteristic of cancer, but their small size suggested a nonhuman origin. A polymerase-chain-reaction (PCR) assay targeting eukaryotes identified Hymenolepis nana DNA. Although the cells were unrecognizable as tapeworm tissue, immunohistochemical staining and probe hybridization labeled the cells in situ. Comparative deep sequencing identified H. nana structural genomic variants that are compatible with mutations described in cancer. Invasion of human tissue by abnormal, proliferating, genetically altered tapeworm cells is a novel disease mechanism that links infection and cancer.

September 2012 marked the beginning of the largest reported outbreak of infections associated with epidural and intra-articular injections. Contamination of methylprednisolone acetate with the black mold, Exserohilum rostratum, was the primary cause of the outbreak, with >13,000 persons exposed to the potentially contaminated drug, 741 confirmed drug-related infections, and 55 deaths. Fatal meningitis and localized epidural, paraspinal, and peripheral joint infections occurred. Tissues from 40 laboratory-confirmed cases representing these various clinical entities were evaluated by histopathological analysis, special stains, and IHC to characterize the pathological features and investigate the pathogenesis of infection, and to evaluate methods for detection of Exserohilum in formalin-fixed, paraffin-embedded (FFPE) tissues. Fatal cases had necrosuppurative to granulomatous meningitis and vasculitis, with thrombi and abundant angioinvasive fungi, with extensive involvement of the basilar arterial circulation of the brain. IHC was a highly sensitive method for detection of fungus in FFPE tissues, demonstrating both hyphal forms and granular fungal antigens, and PCR identified Exserohilum in FFPE and fresh tissues. Our findings suggest a pathogenesis for meningitis involving fungal penetration into the cerebrospinal fluid at the injection site, with transport through cerebrospinal fluid to the basal cisterns and subsequent invasion of the basilar arteries. Further studies are needed to characterize Exserohilum and investigate the potential effects of underlying host factors and steroid administration on the pathogenesis of infection.

BACKGROUND: Pandemic 2009 H1N1 influenza A (pH1N1) virus has caused substantial morbidity and mortality globally and continues to circulate. Although pH1N1 viral antigens have been demonstrated in various human tissues by immunohistochemistry (IHC), cellular localization of pH1N1 RNA in these tissues has largely remained uninvestigated. OBJECTIVES: To examine the distribution of pH1N1 RNA in tissues of fatal cases in order to understand the virus tissue tropism, replication and disease pathogenesis. STUDY DESIGN: Formalin-fixed, paraffin embedded autopsy tissues from 21 patients with confirmed pH1N1 infection were analyzed by influenza A IHC and by in situ hybridization (ISH) using DIG-labeled sense (detects viral RNA) and antisense probes (detects positive-stranded mRNA and cRNA) targeting the nucleoprotein gene of pH1N1 virus. RESULTS: pH1N1 RNA was localized by ISH in 57% of cases while viral antigens were detected by IHC in 76%. However, in cases with a short duration of illness (1-3 days), more cases (69%) were positive by ISH than IHC (62%). Strong ISH staining was detected by antisense probes in the alveolar pneumocytes of the lungs, mucous glands and in lymph nodes. IHC staining of viral antigens was demonstrated in the lung pneumocytes and mucous glands, but no immunostaining was detected in any of the lymph nodes examined. CONCLUSIONS: This study demonstrates cellular localization of positive-stranded pH1N1 RNA in the lungs, mucous glands and lymph nodes that suggests viral replication in these tissues. The novel ISH assay can be a useful adjunct for the detection of pH1N1 virus in tissues and for pathogenesis studies.

We evaluated pandemic influenza A (H1N1) 2009 virus isolates and respiratory tissues collected at autopsy by electron microscopy. Many morphologic characteristics were similar to those previously described for influenza virus. One of the distinctive features was dense tubular structures in the nuclei of infected cells.