Novel predictive assay for contact allergens using human skin explant cultures.

Contact allergens sensitize the immune system by the binding to and subsequent activation of Langerhans cells (LCs), the antigen-presenting cells of the skin. At present, new chemicals are usually tested for their contact allergenicity in animal models. To develop an animal-replacing predictive in vivo assay for the identification of potential contact allergens, we compared the effects of epicutaneous application of six known contact allergens, five known irritants and two dermatologically inactive chemicals on LCs in skin biopsy cultures from seven healthy donors. Immunohistochemical analysis of cryostat sections of all the biopsies treated with contact allergens showed 1) a large reduction in the number of LCs in epidermis, as evaluated by a decrease in human leukocyte antigens (HLA)-DR-expressing cells, and CD1a-expressing cells and 2) accumulation of the remaining LCs at the epidermal-dermal junction. In contrast, the irritants, inactive chemicals, and solvents did not induce these changes. Morphometrical analysis indicated that the contact allergen-induced reduction in the number of HLA-DR+ and CD1a+ LCs per millimeter of epidermis was significant and was dependent on the concentration of the contact allergens. Flow cytometric analysis of isolated epidermal cells confirmed the immunohistochemical findings. In combination, these results suggest that the culture of ex vivo human skin explants provides a promising model to predict potential allergenicity of newly produced chemical compounds and can therefore replace current animal models.     

Fine-needle aspiration cytology diagnosis of tuberculosis

Fine-needle aspiration cytology of lymph nodes and extranodal swellings in 160 cases showed granulomatous reaction with or without caseation necrosis in 83%. The material was acellular or predominantly composed of necrotic material, polymorphs, and lymphocytes in 17%. The age of the patient ranged from 1.5 to 72 yr. The male to female ratio was 1:1.3. Acid-fast bacilli (AFB) could be demonstrated in 40.6% of cases. In cases associated with cellular reaction and necrosis. AFB positivity was 50.0%, while it was 66.7% in cases with acellular necrotic material.     

Infection with an extended-spectrum beta-lactamase-producing strain of Serratia marcescens following tongue reconstruction

We report a case of postsurgical wound infection of polymicrobial etiology caused by Serratia marcescens and Pseudomonas aeruginosa following the use of a radial forearm free flap for oncological tongue reconstruction. S. marcescens was a producer of SHV-12 extended-spectrum beta-lactamase (ESBL). This is the first report from India of this ESBL. S. marcescens and P. aeruginosa were resistant to the empirical perioperative antibiotics administered. Delay in the recognition of the type of infection and in the institution of appropriate therapy resulted in total loss of the free flap.     

The rising trend of invasive zygomycosis in patients with uncontrolled diabetes mellitus.

Zygomycosis is an emerging infection worldwide. A study was conducted to understand its spectrum in the Indian scenario. All patients diagnosed for invasive zygomycosis at a tertiary care center in north India from 2000-2004, were retrospectively analyzed. A total of 178 cases (mean average of 35.6 cases/year) of zygomycosis were diagnosed. Rhino-orbito-cerebral type (54.5%) was the commonest presentation followed by cutaneous (14.6%), disseminated (9.0%), and gastrointestinal (8.4%) zygomycosis. Renal and pulmonary zygomycosis were seen in 6.7% patients each. Uncontrolled diabetes mellitus (in 73.6% of cases) was the significant risk factor in all types (Odds Ratio 1.5-8.0) except renal zygomycosis. Breach of skin was the risk factor in 46.2% patients with cutaneous zygomycosis. However, no risk factor could be detected in 11.8% patients. Antemortem diagnosis was possible in 83.7% cases. The commonest (61.5%) isolate was Rhizopus oryzae followed by Apophysomyces elegans in 27% patients. Combination of debridement surgery and amphotericin B therapy was significantly better in survival of the patients (P<0.005) than amphotericin B alone (79.6% vs. 51.7% survival). Thus, a rising trend of invasive zygomycosis was observed in patients with uncontrolled diabetes mellitus in India. Consistent diagnosis of renal zygomycosis in apparently healthy hosts and the emergence of A. elegans in India demand further study.     

Not everything acid fast is Mycobacterium tuberculosis--a case report.

The Ziehl-Neelsen (ZN) stain is important in identifying organisms that are acid fast, principally Mycobacterium tuberculosis. However, decolorisation with a weaker acid concentration (for example 1% hydrochloric acid), often used in ZN staining in histology, can result in a wider variety of organisms appearing acid fast and can be a cause of misidentification. To illustrate this point, a patient is described with pulmonary nocardiosis who was misdiagnosed as having tuberculous empyema on pleural biopsy.