Pathology of pulmonary tuberculosis and non-tuberculous mycobacterial lung disease: Facts, misconceptions, and practical tips for pathologists.

Most pathologists are familiar with the microscopic features of tuberculosis and the need to examine special stains for acid-fast bacteria (AFB) in cases of granulomatous lung disease. However, misconceptions do exist, including the concept that finding AFB in "caseating granulomas" confirms the diagnosis of tuberculosis. This dogma is attributable to the high prevalence of tuberculosis in many countries, as well as unfamiliarity with the microscopic spectrum of non-tuberculous mycobacterial lung disease. This review aims to provide surgical pathologists with practical tips to identify AFB, illustrate the histologic overlap between pulmonary tuberculosis and non-tuberculous mycobacterial lung disease, and highlight the importance of cultures in this setting. M. tuberculosis and non-tuberculous mycobacteria cannot be reliably differentiated either on the basis of the tissue reaction or by bacterial morphology on acid-fast stains. Although a presumptive clinical diagnosis of tuberculosis can be made without culture-confirmation, the only definitive means to determine the true identity of AFB is by cultures or molecular methods. Making this distinction is most critical when AFB are found in incidentally detected lung nodules in geographic locations where the incidence of tuberculosis is low, because in such settings AFB in necrotizing granulomas of the lung are more likely to be non-tuberculous mycobacteria than M. tuberculosis.

Selecting suitable solid organ transplant donors: Reducing the risk of donor-transmitted infections.

Selection of the appropriate donor is essential to a successful allograft recipient outcome for solid organ transplantation. Multiple infectious diseases have been transmitted from the donor to the recipient via transplantation. Donor-transmitted infections cause increased morbidity and mortality to the recipient. In recent years, a series of high-profile transmissions of infections have occurred in organ recipients prompting increased attention on the process of improving the selection of an appropriate donor that balances the shortage of needed allografts with an approach that mitigates the risk of donor-transmitted infection to the recipient. Important advances focused on improving donor screening diagnostics, using previously excluded high-risk donors, and individualizing the selection of allografts to recipients based on their prior infection history are serving to increase the donor pool and improve outcomes after transplant. This article serves to review the relevant literature surrounding this topic and to provide a suggested approach to the selection of an appropriate solid organ transplant donor.

Complex prosthetic joint infections due to carbapenemase-producing Klebsiella pneumoniae: a unique challenge in the era of untreatable infections.

OBJECTIVES: Limited clinical experience exists regarding the management of prosthetic joint infection (PJI) due to multidrug-resistant (MDR) Gram-negative organisms. We review three cases of carbapenem-resistant Klebsiella pneumoniae (CRKP) complicating PJI. METHODS: This was a retrospective study of all patients at a tertiary care institution with CRKP complicating PJI between January 2007 and December 2010. Demographic data, procedures, organisms involved, length of stay, antibiotic treatments, and outcomes were collected. Antimicrobial susceptibility testing was performed on CRKP isolates, and the mechanism of resistance was ascertained by PCR. RESULTS: This analysis demonstrated that: (1) the CRKP possessed blaKPC and were difficult to eradicate (persistent) in PJI; (2) multiple surgeries and antibiotic courses were undertaken and patients required a prolonged length of stay; (3) resistance to colistin and amikacin emerged on therapy; (4) the same strain of CRKP may be responsible for relapse of infection; (5) significant morbidity and mortality resulted. CONCLUSIONS: These cases highlight the opportunistic and chronic nature of CRKP in PJIs and the need for aggressive medical and surgical treatment. Further investigations of the management of CRKP PJI and new drug therapies for infections due to MDR Gram-negative organisms are urgently needed.

Challenges of interferon-γ release assay conversions in serial testing of health-care workers in a TB control program.

BACKGROUND: Clinical data with use of serial interferon-γ release assay (IGRA) testing in US health-care workers (HCWs) are limited. METHODS: A single-center, retrospective chart review was done from 2007 to 2010 of HCWs who underwent preemployment QuantiFERON-TB Gold In-Tube testing. Demographic data, bacille Calmette-Guérin history, prior tuberculin skin test result if done, and baseline and serial IGRA values were obtained. The number of IGRA converters and reverters and their subsequent management by infectious disease physicians were reviewed. Quantitative IGRA-negative values were not available. RESULTS: A total of 7,374 IGRAs were performed on newly hired HCWs. Of these tests, 486 (6.6%) were positive at baseline, 305 (4.1%) were indeterminate, and 6,583 (89.3%) were negative. From 2007 to 2010, 52 of 1,857 HCWs (2.8%) with serial IGRA tests were identified as converters, with a serial IGRA median value of 0.63 IU/mL. Seventy-one percent of HCWs with IGRA conversion had values ≤ 1 IU/mL. None of the converters had active TB or were part of an outbreak investigation. CONCLUSIONS: Clinical significance of most QuantiFERON-TB Gold In-Tube conversions in serial testing remains a challenging task for clinicians. The use of a single cutoff point criterion for IGRA may lead to overdiagnosis of new TB infections. Clinical assessment and evaluation may help to prevent unnecessary therapy in these cases. The criteria for defining conversions and reversions by establishing new cutoffs needs to be evaluated further, especially in HCWs.

Prosthetic joint infection: when to suspect it, how to manage it.

The number of prosthetic joint infections in the United States is rising because of our aging population and the increasing number of adults undergoing joint replacement surgery. The cardinal symptom of prosthetic joint infection is recurrent pain in the joint. Fever and leukocytosis may be absent in elderly patients, particularly in late infections. Diagnosis requires joint aspiration or operative biopsy. Successful outcomes require expert orthopedic surgical management and prolonged antibiotic therapy. Treatment should be individualized according to the specific pathogen and clinical circumstances.