Mini epidemic of isoniazide resistant TB in rural TN: a need for supervised preventive therapy.

With the resurgence of tuberculosis (TB) in the late 1980s, multi-drug-resistant TB (MDR-TB) also became a serious challenge to the TB control programs across the United States (US). While the incidence of TB resumed a downward trend in the mid 1900s, drug-resistant TB continues to be a national and international problem. We reviewed the public health data of drug-resistant TB cases (1996-2002) in Greene County, TN, with a detailed analysis of their contact investigation. Our study included demographic data of age, sex, race, human immunodeficiency virus (HIV) status and other known risk factors for drug-resistant TB. Contact investigation of two patients with isoniazide-resistant active pulmonary TB led to the discovery of two additional cases of active pulmonary tuberculosis, one of them being a 14-month-old child. All four of the patients were U.S. born, had negative HIV tests, and lacked other risk factors for drug-resistant TB. In all four cases, the Mycobacterium tuberculosis isolates were resistant to isoniazide, three were streptomycin resistant, and was ethambutol resistant. A total of 65 close contacts were identified, 11 of whom had a positive purified protein derivative (PPD) skin test indicating latent TB infection. Based on the American Thoracic Society's recommendations, the contacts with a positive PPD were prescribed rifampin for chemo-prevention rather than INH. However, one active case was detected from this infected contact who had failed to comply with chemo-preventive therapy. The second active case was a child who developed active pulmonary TB before chemoprevention could be initiated. Drug culture profile and DNA analysis (RFLP) confirmed the same source for TB transmission. The 11/65 (16.5 percent) infection rate among the contact was comparable to the state average (p < 0.05), but the case rate of 4/65 (6.15 percent) was high. In two out of four active cases, who were family members of the known cases, active infection could have been prevented. High prevalence of drug-resistant TB in rural areas without any known risk factors and failure of prevention are crucial findings of our study. Clinicians practicing in a rural setting should be aware of occasional mini-outbreaks of drug-resistant TB. Supervised therapy for rifampin chemo-prophylaxis and other standard public health measures successfully controlled this mini-epidemic. Awareness of drug resistance in family clusters and an urgent need for prompt chemo-preventive measures are important in implementing successful TB control programs.

Dermatology for the practicing allergist: Tinea pedis and its complications.

Tinea pedis is a chronic fungal infection of the feet, very often observed in patients who are immuno-suppressed or have diabetes mellitus. The practicing allergist may be called upon to treat this disease for various reasons. Sometimes tinea infection may be mistaken for atopic dermatitis or allergic eczema. In other patients, tinea pedis may complicate allergy and asthma and may contribute to refractory atopic disease. Patients with recurrent cellulitis may be referred to the allergist/immunologist for an immune evaluation and discovered to have tinea pedis as a predisposing factor. From a molecular standpoint, superficial fungal infections may induce a type2 T helper cell response (Th2) that can aggravate atopy. Th2 cytokines may induce eosinophil recruitment and immunoglobulin E (IgE) class switching by B cells, thereby leading to exacerbation of atopic conditions. Three groups of fungal pathogens, referred to as dermatophytes, have been shown to cause tinea pedis: Trychophyton sp, Epidermophyton sp, and Microsporum sp. The disease manifests as a pruritic, erythematous, scaly eruption on the foot and depending on its location, three variants have been described: interdigital type, moccasin type, and vesiculobullous type. Tinea pedis may be associated with recurrent cellulitis, as the fungal pathogens provide a portal for bacterial invasion of subcutaneous tissues. In some cases of refractory asthma, treatment of the associated tinea pedis infection may induce remission in airway disease. Very often, protracted topical and/or oral antifungal agents are required to treat this often frustrating and morbid disease. An evaluation for underlying immuno-suppression or diabetes may be indicated in patients with refractory disease.