Validation of a qualitative real-time PCR assay for the detection of Candida auris in hospital inpatient screening.

Candida auris is a multidrug-resistant opportunistic fungal pathogen capable of causing serious infections and healthcare-associated outbreaks. Screening for colonization with C. auris has become routine and is recommended in many hospitals and healthcare facilities as an infection control and prevention strategy. Subsequently, and since there are currently no FDA-approved tests for this purpose, clinical microbiology laboratories have become responsible for developing protocols to detect C. auris using axial and inguinal screening swabs. In a College of American Pathologists-accredited large academic healthcare center setting, we implemented a laboratory-developed nucleic-acid amplification test for the detection of C. auris DNA. Our test validation evaluated the performance of the DiaSorin C. auris primer set used in a real-time qualitative PCR assay on the LIAISON MDX thermocycler with the Simplexa Universal Disc. The assay was highly sensitive and specific, with a limit of detection of 1-2 CFU/reaction, with no observed cross-reactivity with other Candida spp., bacterial skin commensal organisms or commonly encountered viruses. When run in parallel with a culture-based detection method, the PCR assay was 100% sensitive and specific. The assay was precise, with low variability between replicates within and between runs. Lastly, pre-analytical factors, including swab storage time, temperature, and transport media, were assessed and found to have no significant effect on the detection of C. auris at variable concentrations. Taken together, this study expands the available options for nucleic acid detection of C. auris and characterizes pre-analytical factors for implementation in both high- and low-volume laboratory settings. IMPORTANCE: This study overviews the validation and implementation of a molecular screening tool for the detection of Candida auris in a College of American Pathologist-accredited clinical laboratory. This molecular laboratory-developed test is both highly sensitive and specific and has significant health-system cost-savings associated with significantly reduced turn-around-time compared to traditional standard-of-care culture-based work up. This method and workflow is of interest to support clinical microbiology diagnostics and to help aid in hospital inpatient, and infection prevention control screening.

Atypical cartilage in type II germ cell tumors of the mediastinum show significantly different patterns of IDH1/2 mutations from conventional chondrosarcoma.

Neoplastic cartilage is a common component of teratomas in type II germ cell tumors. Although IDH1/2 mutations have been well-described in somatic cartilaginous tumors, ranging from benign enchondromas to highly aggressive dedifferentiated chondrosarcomas, the presence of IDH1/2 mutations in cartilaginous neoplasms arising from germ cell tumors has not been previously investigated. To better understand the relationship between these tumors and their bone/soft tissue counterpart, we studied the IDH1/2 mutational status of 20 cases of primary mediastinal mixed germ cell tumors with areas of readily identifiable cartilaginous differentiation. Our study found that cartilaginous lesions arising in germ cell tumors have a different frequency and distribution of IDH1/2 mutations compared to those at somatic sites. We identified IDH1/2 mutations in only 15% (3/20) of cases, compared to a frequency in the literature among differentiated chondroid tumors of bone and soft tissue of 54%, a highly significant decreased frequency (p = 0.0011; chi-square test). Furthermore, they were exclusively IDH2 R172 mutations that occurred at a non-significant, increased frequency in the germ cell tumor group compared to conventional chondrosarcoma (15% vs. 5%, respectively, p > 0.05, chi-square test). The unexpected finding, therefore, was entirely attributable to the absence of IDH1 R132 mutation in chondroid neoplasia of germ cell origin (p < 0.00001, Fisher exact test). Our results suggest that a subset of cartilaginous lesions arising within type II germ cell tumors have a similar oncogenic mechanism to their bone/soft tissue counterpart but that the majority form using different oncogenic mechanisms compared to their somatic counterparts.

Evaluating mismatch repair deficiency for solid tumor immunotherapy eligibility: immunohistochemistry versus microsatellite molecular testing.

While many landmark solid tumor immunotherapy studies show clinical benefits for solid tumors with high microsatellite instability (MSI-H) and mismatch repair deficiency (dMMR), the methodologies focus only on confirmatory polymerase chain reaction (PCR) testing for MSI-H. Because some tumors are either dMMR or MSI-H but not the other, clinicians must choose between two testing methods for a broad patient population. We investigated the level of correlation between MMR protein immunohistochemistry (IHC) and microsatellite PCR testing results in 62 cancer patients. Thirty-five of the 62 cases (56.5%) were MSI-H by PCR, whereas 35 (56.5%) were dMMR by IHC. MMR IHC results correlated well with MSI PCR in 32 co-positive cases (91.4%) and 24 co-negative cases (88.9%). Six discrepant cases (9.7%) were identified, among which three were MSI-H and MMR intact, and three were dMMR and microsatellite stable. The results of this study highlight the implications of dMMR/MSI testing strategies on precision oncology. Co-testing with both MMR IHC and MSI PCR may be an effective screening strategy for evaluating immunotherapy eligibility status for solid tumors.