Identification of nontuberculous mycobacterial infection by IS6110 and hsp65 gene analysis on lung tissues

Detection of microorganisms in granulomas that have been formalin-fixed: review of the literature regarding use of molecular methods

Granuloma is an organized aggregate of immune cells that under the microscope appear as epithelioid macrophages. A granuloma can only be diagnosed when a pathologist observes this type of inflammation under the microscope. If a foreign body or a parasite is not observed inside the granuloma, stains for acid-fast bacilli and fungi are ordered since mycobacteria and fungi are frequently the cause of this type of inflammation. It is calculated that 12 to 36% of granulomas do not have a specific etiology and many have wondered if with new molecular methods we could reduce this number. This paper will summarize the frequently known causes of granulomas and will present the recent literature regarding the use of molecular techniques on tissue specimens and how these have helped in defining causative agents. We will also briefly describe new research regarding formation and function of granulomas and how this impacts our ability to find an etiologic agent.

Pathological features of Mycobacterium kansasii infection in black bearded sakis (Chiropotes satanas)

Two black bearded sakis (Chiropotes satanas), kept in the same cage in a zoological park, developed multifocal subcutaneous nodular lesions and were diagnosed as having mycobacterial infection by microscopical examination of tissues and 16S rRNA polymerase chain reaction (PCR) and subsequent sequencing of amplicons. One animal died despite both being treated with prolonged antimicrobial therapy. This animal had disseminated disease with lesions in the liver, spleen, lymph nodes and brain. The lesions were granulomatous in nature, but organisms were not identified by acid-fast staining other than on an impression smear of one of the skin nodules. The granulomatous lesions lacked epithelioid macrophages, multinucleated giant cells and fibrous encapsulation. Mycobacterium kansasii was identified by PCR in the lymph nodes of the animal with disseminated disease. Mycobacterial speciation was not as readily achieved in the animal with cutaneous nodules only.

Clinical manifestations, diagnosis, and treatment of Mycobacterium haemophilum infections

Mycobacterium haemophilum is a slowly growing acid-fast bacillus (AFB) belonging to the group of nontuberculous mycobacteria (NTM) frequently found in environmental habitats, which can colonize and occasionally infect humans and animals. Several findings suggest that water reservoirs are a likely source of M. haemophilum infections. M. haemophilum causes mainly ulcerating skin infections and arthritis in persons who are severely immunocompromised. Disseminated and pulmonary infections occasionally occur. The second at-risk group is otherwise healthy children, who typically develop cervical and perihilar lymphadenitis. A full diagnostic regimen for the optimal detection of M. haemophilum includes acid-fast staining, culturing at two temperatures with iron-supplemented media, and molecular detection. The most preferable molecular assay is a real-time PCR targeting an M. haemophilum-specific internal transcribed spacer (ITS), but another approach is the application of a generic PCR for a mycobacterium-specific fragment with subsequent sequencing to identify M. haemophilum. No standard treatment guidelines are available, but published literature agrees that immunocompromised patients should be treated with multiple antibiotics, tailored to the disease presentation and underlying degree of immune suppression. The outcome of M. haemophilum cervicofacial lymphadenitis in immunocompetent patients favors surgical intervention rather than antibiotic treatment.

Mycobacterial infections in adult patients with hematological malignancy

We retrospectively analyzed the clinical and microbiological characteristics of adult patients with hematological malignancy and nontuberculous mycobacteria (NTM) infections from 2001 to 2010. During the study period, 50 patients with hematological malignancy and tuberculosis (TB) were also evaluated. Among 2,846 patients with hematological malignancy, 34 (1.2%) patients had NTM infections. Mycobacterium avium-intracellulare complex (13 patients, 38%) was the most commonly isolated species, followed by M. abscessus (21%), M. fortuitum (18%), and M. kansasii (18%). Twenty-six patients had pulmonary NTM infection and eight patients had disseminated disease. Neutropenia was more frequently encountered among patients with disseminated NTM disease (p = 0.007) at diagnosis than among patients with pulmonary disease only. Twenty-five (74%) patients received adequate initial antibiotic treatment. Five of the 34 patients died within 30 days after diagnosis. Cox regression multivariate analysis showed that chronic kidney disease (p = 0.017) and neutropenia at diagnosis (p = 0.032) were independent prognostic factors of NTM infection in patients with hematological malignancy. Patients with NTM infection had higher absolute neutrophil counts at diagnosis (p = 0.003) and a higher 30-day mortality rate (15% vs. 2%, p = 0.025) than TB patients. Hematological patients with chronic kidney disease and febrile neutropenia who developed NTM infection had significant worse prognosis than patients with TB infection.

First report of disseminated Mycobacterium skin infections in two liver transplant recipients and rapid diagnosis by hsp65 gene sequencing

We present here the first report of disseminated skin Mycobacterium infections in two liver transplant recipients, in which hsp65 gene sequencing was used for rapid species identification. Both patients had hepatitis B virus-related cirrhosis and diabetes mellitus and presented with progressive generalized, nodular skin lesions. In one patient, a 50-year-old woman who had frequent contact with marine fish, an acid-fast bacillus was isolated from skin biopsy tissue after 2 months of culture. While awaiting phenotypic identification results, hsp65 gene sequencing showed that it was most closely related to that of Mycobacterium marinum with 100% nucleotide identity. The patient was treated with oral rifampin, ethambutol, and moxifloxacin. In the other patient, a 59-year-old woman, direct PCR for Mycobacterium using hsp65 gene from skin biopsy tissue was positive, with the sequence most closely related to that of M. haemophilum with 100% nucleotide identity. Based on PCR results, the patient was treated with clarithromycin, ethambutol, moxifloxacin, and amikacin. A strain of M. haemophilum was only isolated after 3 months. Skin lesions of both patients resolved after 1 year of antimycobacterial therapy. Nontuberculous Mycobacterium infections should be considered in liver transplant recipients presenting with chronic, nodular skin lesions. This report highlights the crucial role of hsp65 gene PCR and sequencing on both cultured isolates and direct clinical specimens for rapid diagnosis of slow-growing Mycobacterium infection.

Role of histology in the diagnosis of infectious causes of granulomatous lung disease

PURPOSE OF REVIEW

Histologic examination and microbiologic cultures are the gold standards for the diagnosis of infectious granulomatous lung diseases. Although biopsies require invasive procedures, they often yield information that cannot be obtained by other methods. The aims of this article are to outline the major infections that cause granulomatous inflammation in the lung and to familiarize clinicians with the utility of histologic examination in their diagnosis.

RECENT FINDINGS

The histopathologic features of acute pulmonary histoplasmosis and granulomatous Pneumocystis pneumonia have been described in detail, the relative contributions of histology and microbiologic cultures in the diagnosis of blastomycosis have been delineated, and Cryptococcus gattii has emerged as a significant cause of granulomatous pulmonary nodules.

SUMMARY

The major infectious causes of granulomatous lung disease are mycobacteria and fungi. Histologic examination is particularly important in the diagnosis of pulmonary granulomatous infections when clinical, radiologic and serologic findings are nonspecific. Histology and microbiology play complementary but distinct roles in diagnosis. For organisms that grow slowly in cultures, histology has the additional advantage of being able to provide a rapid diagnosis.