Mycobacterial PCR Is an Adjunct to Pulmonary Granuloma Diagnosis in Surgical Pathology.
Scott Kantola, Yi-Wei Tang, Joyce E Johnson. Vanderbilt University Medical Center, Nashville, TN
Background: Necrotizing granulomatous inflammation in the lung is routinely encountered in Surgical Pathology practice. Acid-fast stains are commonly negative in cases of mycobacterial infection. Rapid, accurate identification of infection with tuberculosis (TB) or non-TB mycobacteria is important for optimal, timely therapeutic decision-making and for protection of nosocomial and public health.
Design: Using SNOMED data, all surgical pathology cases of necrotizing granulomatous inflammation of lung or bronchus from 2004-8 were identified. The slides were reviewed and the H and E interpretation confirmed. "Controls" (n=24) were those in which an etiology other than mycobacterial infection was firmly established, typically with the use of histochemical stains. "Cases" (n=21) were those in which either all stains were negative (n=17), or Ziehl-Neelsen (ZN) or fluorescent AFB stains were positive or suggestive (n=4). Using the H and E slide to direct sampling, the area of the granuloma in the paraffin block was sharply sampled using a scalpel. The DNA was extracted and amplified for a mycobacterial 16S-23S ITS region by using a broad-range primer set. One genus-specific (MYC) and 35 species-specific probes were used for detection, using a Luminex 200 instrument (Austin, TX). This procedure detects and speciates 17 medically important Mycobacterium species.
Results: Mycobacterial DNA was detected in 9 of 21 "cases" and 1 of 24 "controls." Among the 9 PCR-positive "cases," species detected by PCR included M. avium (1), M. intracellulare (1), M.intracellulare/xenopi/smegmatis (1), M. kansasii (2), M. fortuitum (2) M. smegmatis (1), and M. tuberculosis (1). The single PCR-positive "control" sample was GMS-positive for yeast forms consistent with Histoplasma sp.; M. kansasii DNA was detected. PCR-negative"cases" (n=12) included 7 cases in which all stains and cultures were negative; 3 in which either the ZN or fAFB stain was positive; and 1 which was stain-negative but grew M. tuberculosis from a different specimen (BAL).
Conclusions: Mycobacteria can be detected and speciated from archived paraffin-embedded lung sections using PCR technology. Stain- and culture-negative granulomas yield a range of species by PCR, some of which are pathogenic. Up to 1/3 of cases remain negative by all modalities (stains, cultures, PCR). Uncommonly, non-mycobacterial granulomas (e.g. Histoplama sp.) may be associated with PCR positivity for mycobacteria (1/24 in our series; M. kansasii).
Monday, February 28, 2011 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 232, Monday Morning