Exserohilum infections associated with contaminated steroid injections: a clinicopathologic review of 40 cases.

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.

Myocardial injury and bacterial pneumonia contribute to the pathogenesis of fatal influenza B virus infection.

BACKGROUND: Influenza B virus infection causes rates of hospitalization and influenza-associated pneumonia similar to seasonal influenza A virus infection and accounts for a substantial percentage of all influenza-related hospitalizations and deaths among those aged <18 years; however, the pathogenesis of fatal influenza B virus infection is poorly described. METHODS: Tissue samples obtained at autopsy from 45 case patients with fatal influenza B virus infection were evaluated by light microscopy and immunohistochemical assays for influenza B virus, various bacterial pathogens, and complement components C4d and C9, to identify the cellular tropism of influenza B virus, characterize concomitant bacterial pneumonia, and describe the spectrum of cardiopulmonary injury. RESULTS: Viral antigens were localized to ciliated respiratory epithelium and cells of submucosal glands and ducts. Concomitant bacterial pneumonia, caused predominantly by Staphylococcus aureus, was identified in 38% of case patients and occurred with significantly greater frequency in those aged >18 years. Pathologic evidence of myocardial injury was identified in 69% of case patients for whom cardiac tissue samples were available for examination, predominantly in case patients aged <18 years. CONCLUSIONS: Our findings suggest that bacterial pneumonia and cardiac injury contribute to fatal outcomes after infection with influenza B virus and that the frequency of these manifestations may be age related.

Cellular immune responses to severe acute respiratory syndrome coronavirus (SARS-CoV) infection in senescent BALB/c mice: CD4+ T cells are important in control of SARS-CoV infection.

We characterized the cellular immune response to severe acute respiratory syndrome coronavirus (SARS-CoV) infection in 12- to 14-month-old BALB/c mice, a model that mimics features of the human disease. Following intranasal administration, the virus replicated in the lungs, with peak titers on day 2 postinfection. Enhanced production of cytokines (tumor necrosis factor alpha [TNF-alpha] and interleukin-6 [IL-6]) and chemokines (CXCL10, CCL2, CCL3, and CCL5) correlated with migration of NK cells, macrophages, and plasmacytoid dendritic cells (pDC) into the lungs. By day 7, histopathologic evidence of pneumonitis was seen in the lungs when viral clearance occurred. At this time, a second wave of enhanced production of cytokines (TNF-alpha, IL-6, gamma interferon [IFN-gamma], IL-2, and IL-5), chemokines (CXCL9, CXCL10, CCL2, CCL3, and CCL5), and receptors (CXCR3, CCR2, and CCR5), was detected in the lungs, associated with an influx of T lymphocytes. Depletion of CD8(+) T cells at the time of infection did not affect viral replication or clearance. However, depletion of CD4(+) T cells resulted in an enhanced immune-mediated interstitial pneumonitis and delayed clearance of SARS-CoV from the lungs, which was associated with reduced neutralizing antibody and cytokine production and reduced pulmonary recruitment of lymphocytes. Innate defense mechanisms are able to control SARS-CoV infection in the absence of CD4(+) and CD8(+) T cells and antibodies. Our findings provide new insights into the pathogenesis of SARS, demonstrating the important role of CD4(+) but not CD8(+) T cells in primary SARS-CoV infection in this model.

2009 pandemic influenza A (H1N1): pathology and pathogenesis of 100 fatal cases in the United States.

In the spring of 2009, a novel influenza A (H1N1) virus emerged in North America and spread worldwide to cause the first influenza pandemic since 1968. During the first 4 months, over 500 deaths in the United States had been associated with confirmed 2009 pandemic influenza A (H1N1) [2009 H1N1] virus infection. Pathological evaluation of respiratory specimens from initial influenza-associated deaths suggested marked differences in viral tropism and tissue damage compared with seasonal influenza and prompted further investigation. Available autopsy tissue samples were obtained from 100 US deaths with laboratory-confirmed 2009 H1N1 virus infection. Demographic and clinical data of these case-patients were collected, and the tissues were evaluated by multiple laboratory methods, including histopathological evaluation, special stains, molecular and immunohistochemical assays, viral culture, and electron microscopy. The most prominent histopathological feature observed was diffuse alveolar damage in the lung in all case-patients examined. Alveolar lining cells, including type I and type II pneumocytes, were the primary infected cells. Bacterial co-infections were identified in >25% of the case-patients. Viral pneumonia and immunolocalization of viral antigen in association with diffuse alveolar damage are prominent features of infection with 2009 pandemic influenza A (H1N1) virus. Underlying medical conditions and bacterial co-infections contributed to the fatal outcome of this infection. More studies are needed to understand the multifactorial pathogenesis of this infection.

Adrenal gland hemorrhage in patients with fatal bacterial infections.

A wide spectrum of adrenal gland pathology is seen during bacterial infections. Hemorrhage is particularly associated with meningococcemia, while abscesses have been described with several neonatal infections. We studied adrenal gland histopathology of 65 patients with bacterial infections documented in a variety of tissues by using immunohistochemistry. The infections diagnosed included Neisseria meningitidies, group A streptococcus, Rickettsia rickettsii, Streptococcus pneumoniae, Staphylococcus aureus, Ehrlichia sp., Bacillus anthracis, Leptospira sp., Clostridium sp., Klebsiella sp., Legionella sp., Yersinia pestis, and Treponema pallidum. Bacteria were detected in the adrenal of 40 (61%) cases. Adrenal hemorrhage was present in 39 (60%) cases. Bacteria or bacterial antigens were observed in 31 (79%) of the cases with adrenal hemorrhage including 14 with N. meningitidis, four with R. rickettsii, four with S. pneumoniae, three with group A streptococcus, two with S. aureus, two with B. anthracis, one with T. pallidum, and one with Legionella sp. Bacterial antigens were observed in nine of 26 non-hemorrhagic adrenal glands that showed inflammatory foci (four cases), edema (two cases), congestion (two cases), or necrosis (one case). Hemorrhage is the most frequent adrenal gland pathology observed in fatal bacterial infections. Bacteria and bacterial antigens are frequently seen in adrenal glands with hemorrhage and may play a pathogenic role. Although N. meningitidis is the most frequent bacteria associated with adrenal gland pathology, a broad collection of bacteria can also cause adrenal lesions.

Immunohistochemical evidence of Clostridium sp, Staphylococcus aureus, and group A Streptococcus in severe soft tissue infections related to injection drug use.

Severe soft tissue infections are caused by either single or multiple microorganisms. We performed a retrospective immunohistochemical (IHC) study on formalin-fixed, paraffin-embedded soft tissue samples from 20 injection drug users who were part of a cluster of severe illness and death after skin and soft tissue infections in Scotland and Ireland in 2000. The IHC assays used antibodies against Clostridium sp, Staphylococcus aureus, group A streptococci, and Bacillus anthracis. Intact bacilli and granular Clostridium antigen staining in areas with necrosis, edema, and inflammation were observed in skin, fascia, or muscle samples of 12 (60%) patients. A variety of clostridia were isolated from affected soft tissues in 10 IHC-positive cases. Staphylococcus aureus antigens were observed in 3 cases including 1 where S aureus was isolated, 1 with negative cultures, and 1 where mixed cultures were obtained. Group A streptococcal antigens were observed in 1 case in which Streptococcus pyogenes and S aureus were isolated. By using IHC, we detected different bacteria in archival soft tissue samples from patients with severe skin and soft tissue infections. Immunohistochemical assays can be of great diagnostic value, particularly for bacteria such as Clostridium sp, which are difficult to isolate because of their anaerobic fastidious growth requirements.

Morphologic, immunologic, and molecular methods to detect bacillus anthracis in formalin-fixed tissues.

Due to the importance of Bacillus anthracis as a cause of naturally occurring infection among humans and as an agent of bioterrorism, there is a vital need for rapid and specific assays, including immunohistochemistry (IHC) and polymerase chain reaction (PCR) assays, to detect the bacterium in formalin-fixed tissues. Colorimetric IHC assays were developed using a multistep indirect immunoalkaline phosphatase method with anti-B. anthracis cell wall (EAII-6G6-2-3) and anti-B. anthracis capsule (FDF-1B9) mAbs to detect B. anthracis antigens in formalin-fixed, paraffin-embedded bacterial cultures and tissues. B. anthracis antigens were localized, using both antibodies, in samples from B. anthracis-infected animals and humans. The colorimetric IHC assay with both antibodies was expedient in diagnosing the presence of B. anthracis in formalin-fixed, paraffin-embedded tissue from bioterrorism-associated cases of inhalational and cutaneous anthrax and from a case of naturally occurring cutaneous anthrax. Using the same antibodies, confocal microscopy demonstrated the structure of replicating B. anthracis in tissues. B. anthracis-specific primers were successfully used with PCR to amplify and detect B. anthracis sequences derived from formalin-fixed tissues of anthrax cases. In this study, morphologic, immunologic, and molecular assays were used to study and diagnose 22 veterinary and human anthrax cases.

Development of an immunohistochemical assay for the detection of babesiosis in formalin-fixed, paraffin-embedded tissue samples.

The hemoparasite Babesia can cause life-threatening infections to neonates, elderly and immunocompromised people, and people who have undergone splenectomy. By using pooled hamster serum samples collected 21 days after infection with Babesia microti, we developed an immunohistochemical assay for formalin-fixed, paraffin-embedded tissue (FFPET) samples and blood smears. By use of the immunohistochemical assay, parasites were detected inside erythrocytes present in the heart, spleen, and liver of experimentally and naturally infected animals. FFPET samples from 2 fatal and 1 nonfatal human cases demonstrated immunohistochemical assay-positive parasites in circulating erythrocytes in various organs, including lymph nodes and spleen. In addition, air-dried blood smears from 4 patients showed positive immunohistochemical staining inside the erythrocytes. The immunohistochemical assay showed cross-reactivity against the Babesia WA-1 strain but did not react against Babesia bigemina or Plasmodium falciparum. The immunohistochemical assay for Babesia microti successfully detected parasites in human and animal FFPET samples and blood smears. This technique will be useful for the diagnosis of clinically suspected cases and for differentiating Babesia microti infection from malaria. Application of this technique to animal models will better define pathogenic mechanisms, including the possible recognition of exoerythrocytic tissue stages.

The pox in the North American backyard: Volepox virus pathogenesis in California mice (Peromyscus californicus).

Volepox virus (VPXV) was first isolated in 1985 from a hind foot scab of an otherwise healthy California vole (Microtus californicus). Subsequent surveys in San Mateo County, CA, revealed serological evidence suggesting that VPXV is endemic to this area, and a second viral isolate from a Pinyon mouse (Peromyscus truei) was collected in 1988. Since then, few studies have been conducted regarding the ecology, pathology, and pathogenicity of VPXV, and its prevalence and role as a potential zoonotic agent remain unknown. To increase our understanding of VPXV disease progression, we challenged 24 California mice (Peromyscus californicus) intranasally with 1.6 × 10(3) PFU of purified VPXV. By day five post infection (pi) we observed decreased activity level, conjunctivitis, ruffled hair, skin lesions, facial edema, and crusty noses. A mortality rate of 54% was noted by day eight pi. In addition, internal organ necrosis and hemorrhages were observed during necropsy of deceased or euthanized animals. Viral loads in tissues (brain, gonad, kidney, liver, lung, spleen, submandibular lymph node, and adrenal gland), bodily secretions (saliva, and tears), and excretions (urine, and/or feces) were evaluated and compared using real time-PCR and tissue culture. Viral loads measured as high as 2 × 10(9) PFU/mL in some organs. Our results suggest that VPXV can cause extreme morbidity and mortality within rodent populations sympatric with the known VPXV reservoirs.

Diagnosis of influenza from respiratory autopsy tissues: detection of virus by real-time reverse transcription-PCR in 222 cases.

The recent influenza pandemic, caused by a novel H1N1 influenza A virus, as well as the seasonal influenza outbreaks caused by varieties of influenza A and B viruses, are responsible for hundreds of thousands of deaths worldwide. Few studies have evaluated the utility of real-time reverse transcription-PCR to detect influenza virus RNA from formalin-fixed, paraffin-embedded tissues obtained at autopsy. In this work, respiratory autopsy tissues from 442 suspect influenza cases were tested by real-time reverse transcription-PCR for seasonal influenza A and B and 2009 pandemic influenza A (H1N1) viruses and the results were compared to those obtained by immunohistochemistry. In total, 222 cases were positive by real-time reverse transcription-PCR, and of 218 real-time, reverse transcription-PCR-positive cases also tested by immunohistochemistry, only 107 were positive. Although formalin-fixed, paraffin-embedded tissues can be used for diagnosis, frozen tissues offer the best chance to make a postmortem diagnosis of influenza because these tissues possess nucleic acids that are less degraded and, as a consequence, provide longer sequence information than that obtained from fixed tissues. We also determined that testing of all available respiratory tissues is critical for optimal detection of influenza virus in postmortem tissues.

Histopathologic spectrum and immunohistochemical diagnosis of amebic meningoencephalitis.

Traditionally, Naegleria fowleri infections are labeled primary amebic meningoencephalitis because of prominent meningeal neutrophilic inflammation. Acanthamoeba spp. and Balamuthia mandrillaris are labeled granulomatous amebic encephalitis because of parenchymal granulomatous inflammation. We compared histopathologic and immunohistochemical features of 18 cases with central nervous system free-living ameba infections. Immunohistochemical assays using polyclonal antibodies that reacted specifically against each genus identified 11 patients with Balamuthia infection, four with N. fowleri, and three with Acanthamoeba. Immunohistochemical assays highlighted the presence of trophozoites that were difficult to identify with hematoxylin and eosin stains in areas of necrosis or where macrophages were abundant. Immunohistochemical assays also demonstrated the presence of granular antigens inside macrophages and blood vessel walls. Amebic cysts were observed in three patients with Acanthamoeba infection and in three with Balamuthia. Patients with Acanthamoeba infection showed granulomatous inflammation. Patients with Naegleria infection had neutrophilic inflammation. Balamuthia infections showed a spectrum of inflammation that ranged from primarily neutrophils to granulomas. Meningitis was present in 88% of cases. Immunohistochemical assays were useful to demonstrate the presence of granular antigens and confirmed the genus of the ameba. The spectrum of inflammation in cases of Balamuthia meningoencephalitis is broader than previously described. The term amebic meningoencephalitis describes better the histopathologic findings than the currently used classification of primary amebic meningoencephalitis and granulomatous amebic encephalitis.

Preclinical testing of candidate topical microbicides for anti-human immunodeficiency virus type 1 activity and tissue toxicity in a human cervical explant culture.

A human cervical explant culture was utilized for the preclinical assessment of anti-human immunodeficiency virus type 1 (HIV-1) activity and tissue toxicity of formulated, candidate topical microbicides. Products tested included cellulose acetate 1,2-benzene dicarboxylate (CAP), a carrageenan-based product (PC-515), a naphthalene sulfonate polymer (PRO 2000), a lysine dendrimer (SPL7013), a nonnucleoside reverse transcriptase inhibitor (UC781), and an antimicrobial peptide (D2A21), along with their placebos. Cervical explants were cultured overnight with HIV-1 with or without product, washed, and monitored for signs of HIV-1 infection. HIV-1 infection was determined by p24gag levels in the basolateral medium and by immunohistochemical analysis of the explant. Product toxicity was measured by the MTT [1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan] assay and histology. CAP, PRO 2000, SPL7013, and UC781 consistently prevented HIV-1 infection in all explants tested. PC-515 and D2A21 prevented HIV-1 infection in 50% or fewer of the explants tested. Placebos did not prevent infection in any of the explants tested. With the exception of PRO 2000 (4%), the MTT assay and histological analysis of the other products and placebos showed minimal toxicity to the epithelium and submucosa. Collectively, these data suggest that this culture system can be used for evaluating the safety and efficacy of topical microbicides designed for vaginal use.

An in vitro model of the leukocyte interactions associated with granuloma formation in Mycobacterium tuberculosis infection.

The principal defense of the human host against a Mycobacterium tuberculosis infection is the formation of granulomas, organized collections of activated macrophages, including epithelioid and multinucleated giant cells, surrounded by lymphocytes. This granuloma can sequester and contain the bacteria preventing active disease, and if the granuloma is maintained, these bacteria may remain latent for a person's lifetime. Secretion of a variety of chemoattractant cytokines following phagocytosis of the bacilli by the macrophage is critical not only to the formation of the granuloma but also to its maintenance. To investigate this process of early granuloma formation, we developed an in vitro model composed entirely of human cells. Combining blood lymphocytes and autologous macrophages from healthy purified protein derivative skin test-negative individuals and mycobacteria resulted in the formation of small, rounded aggregate structures. Microscopic examination found macrophage-specific CD68(+) epithelioid macrophages and small round CD3(+) lymphocytes that in complex resembled small granulomas seen in clinical pathology specimens. Acid-fast staining bacteria were observed between and possibly within the cells composing the granulomas. Supernatants from the infected cells collected at 24 and 48 h and 5 and 9 days after infection were analyzed by a multiplexed cytokine bead-based assay using the Luminex 100 and were found to contain interleukin (IL)-6, IL-8, interferon-gamma and tumor necrosis factor-alpha, cytokines known to be involved in human granuloma formation, in quantities from two-fold to 7000-fold higher than supernatants from uninfected control cells. In addition, chemotaxis assays demonstrated that the same supernatants attracted significantly more human peripheral blood mononuclear cells than those of uninfected cells (P<0.001). This model may provide insight into the earliest stages of granuloma formation in those newly infected.

Cell proliferation and inflammation on biopsy samples with multifocal atrophic gastritis before and 1 year after Helicobacter pylori eradication.

CONTEXT: Results of clinical trials that have assessed whether gastric cancer is preventable with Helicobacter pylori eradication therapy remain inconclusive. These trials have used atrophy, intestinal metaplasia, and dysplasia as histopathologic end points that reflect possible preneoplastic lesions. Trial results would be more compelling if cell proliferation and inflammatory markers improved simultaneously with histopathologic lesions. OBJECTIVE: To study the presence of cell proliferation markers and type of inflammatory cells in biopsy specimens with gastritis, atrophy, and intestinal metaplasia before and 1 year after H pylori therapy and to determine if immunohistochemistry can be used to study these. DESIGN: We evaluated 12 subjects with gastritis and 16 with gastritis and multiple foci of atrophy and intestinal metaplasia by using immunohistochemical assays for tumor suppressor protein p53, proliferation marker Ki-67, cell cycle regulator cyclin D1, T and B lymphocytes, macrophages, and TUNEL (terminal deoxynucleotide transferase deoxyuridine triphosphate nick end labeling) assay for apoptosis. The biopsy specimens were selected from a randomized clinical trial that studied improvement of histopathologic gastric lesions after H pylori eradication. RESULTS: Groups of surface epithelial cells that expressed p53 and Ki-67 were observed more often in subjects with atrophy and intestinal metaplasia compared with those with gastritis alone. T lymphocytes in the lamina propria were frequently observed 1 year after treatment in subjects with atrophy and intestinal metaplasia. CONCLUSIONS: Immunohistochemical assays for cell proliferation and inflammatory cell markers showed different distribution patterns in these gastric biopsy specimens. The presence of T lymphocytes and groups of cells that expressed proliferation markers in subjects with multiple foci of atrophy and intestinal metaplasia needs further study.

Can pre-neoplastic lesions be detected in gastric biopsies of children with Helicobacter pylori infection?

BACKGROUND: Active gastritis, gastric mucosal atrophy and intestinal metaplasia are lesions associated with Helicobacter pylori infection. Atrophy and intestinal metaplasia are only seen in adults. OBJECTIVES: We describe pediatric patients with atrophy and metaplasia, and compare the inflammatory response in these patients to controls. METHODS: As part of a multicenter study of pediatric H. pylori infection, gastric biopsy specimens obtained during diagnostic upper endoscopy of 19 H. pylori-infected children and 45 uninfected controls were reviewed and graded by using the updated Sydney system. The inflammatory response was characterized using immunohistochemistry for T lymphocytes, B lymphocytes, and macrophages, and TUNEL assay for apoptosis. RESULTS: Histology of H. pylori-infected and control biopsy specimens showed active gastritis in 32% and 2% respectively (P = 0.002). Mild intestinal metaplasia was found in 4 H. pylori-infected children, in two of whom it appeared to be accompanied by atrophy. Specimens from patients with H. pylori infection contained increased numbers of B lymphocytes in lymphoid nodules, and apoptosis in the superficial epithelium and inflammatory cells. T lymphocytes and macrophages appeared in similar numbers in specimens from controls and infected patients. CONCLUSIONS: We describe intestinal metaplasia associated with H. pylori infection in children. Since atrophy usually precedes intestinal metaplasia in adults, we suggest that atrophy exists in children. High numbers of B lymphocytes and apoptosis in the surface epithelium are seen in patients with H. pylori infection and may be related to the development of atrophy and intestinal metaplasia.

Histopathologic features of Mycobacterium ulcerans infection.

Because of the emergence of Buruli ulcer disease, the World Health Organization launched a Global Buruli Ulcer Initiative in 1998. This indolent skin infection is caused by Mycobacterium ulcerans. During a study of risk factors for the disease in Ghana, adequate excisional skin-biopsy specimens were obtained from 124 clinically suspicious lesions. Buruli ulcer disease was diagnosed in 78 lesions since acid-fast bacilli (AFB) were found by histopathologic examination. Lesions with other diagnoses included filariasis (3 cases), zygomycosis (2 cases), ulcerative squamous cell carcinomas (2 cases), keratin cyst (1 case), and lymph node (1 case). Thirty-seven specimens that did not show AFB were considered suspected Buruli ulcer disease cases. Necrosis of subcutaneous tissues and dermal collagen were found more frequently in AFB-positive specimens compared with specimens from suspected case-patients (p<0.001). Defining histologic criteria for a diagnosis of Buruli ulcer disease is of clinical and public health importance since it would allow earlier treatment, leading to less deforming sequelae.