A consensus conference to define the utility of advanced infectious disease diagnostics in solid organ transplant recipients

The last decade has seen an explosion of advanced assays for the diagnosis of infectious diseases, yet evidence-based recommendations to inform their optimal use in the care of transplant recipients are lacking. A consensus conference sponsored by the American Society of Transplantation (AST) was convened on December 7, 2021, to define the utility of novel infectious disease diagnostics in organ transplant recipients. The conference represented a collaborative effort by experts in transplant infectious diseases, diagnostic stewardship, and clinical microbiology from centers across North America to evaluate current uses, unmet needs, and future directions for assays in 5 categories including (1) multiplex molecular assays, (2) rapid antimicrobial resistance detection methods, (3) pathogen-specific T-cell reactivity assays, (4) next-generation sequencing assays, and (5) mass spectrometry-based assays. Participants reviewed and appraised available literature, determined assay advantages and limitations, developed best practice guidance largely based on expert opinion for clinical use, and identified areas of future investigation in the setting of transplantation. In addition, attendees emphasized the need for well-designed studies to generate high-quality evidence needed to guide care, identified regulatory and financial barriers, and discussed the role of regulatory agencies in facilitating research and implementation of these assays. Findings and consensus statements are presented.

Human Colon Cancer-Derived Clostridioides difficile Strains Drive Colonic Tumorigenesis in Mice

Defining the complex role of the microbiome in colorectal cancer and the discovery of novel, protumorigenic microbes are areas of active investigation. In the present study, culturing and reassociation experiments revealed that toxigenic strains of Clostridioides difficile drove the tumorigenic phenotype of a subset of colorectal cancer patient-derived mucosal slurries in germ-free ApcMin/+ mice. Tumorigenesis was dependent on the C. difficile toxin TcdB and was associated with induction of Wnt signaling, reactive oxygen species, and protumorigenic mucosal immune responses marked by the infiltration of activated myeloid cells and IL17-producing lymphoid and innate lymphoid cell subsets. These findings suggest that chronic colonization with toxigenic C. difficile is a potential driver of colorectal cancer in patients.

SIGNIFICANCE

Colorectal cancer is a leading cause of cancer and cancer-related deaths worldwide, with a multifactorial etiology that likely includes procarcinogenic bacteria. Using human colon cancer specimens, culturing, and murine models, we demonstrate that chronic infection with the enteric pathogen C. difficile is a previously unrecognized contributor to colonic tumorigenesis. See related commentary by Jain and Dudeja, p. 1838. This article is highlighted in the In This Issue feature, p. 1825.

Comparing the analytical performance of three SARS-CoV-2 molecular diagnostic assays

In December 2019, a novel coronavirus (SARS-CoV-2) was first isolated from Wuhan city, China and within three months, the global community was challenged with a devastating pandemic. The rapid spread of the virus challenged diagnostic laboratories to rapidly develop molecular diagnostic methods. As SARS CoV-2 assays became available for testing on existing molecular platforms, laboratories devoted unprecedented energy and resources into evaluating the analytical performance of the new tests and in some cases developed their own diagnostic assays under FDA-EUA guidance. This study compares the validation of three different molecular assays at the Johns Hopkins Molecular Virology laboratory: the RealStar® SARS-CoV-2 RT-PCR, ePlex® SARS-CoV-2, and the CDC COVID-19 RT-PCR tests. Overall, our studies indicate a comparable analytical performance of the three assays for the detection of SARS-CoV-2.

510. Exposure Investigation Following a Confirmed Case of Candida auris and Multiple Carbapenemase-Producing Carbapenem-Resistant Organisms

Background

Co-infections of Candida auris and carbapenemase-producing carbapenem-resistant Gram-negative organisms (CP-CRO) are an increasing global concern and rarely seen in the United States. We report the case of a 59-year-old male, with recent hospitalization in India, admitted to our facility with C. auris isolated from urine and axilla/groin specimens and CP-CRO from five body sites.

Methods

Travel screening in the emergency department identified a patient at high risk for colonization/infection with multidrug-resistant organisms (MDRO). Contact precautions were initiated. Eight CP-CRO isolates were subsequently identified from clinical and routine surveillance cultures from five separate sites. Of the isolates, seven contained one or more carbapenemase-producing genes detected by Xpert Carba-R assay (Cepheid, Sunnyvale, CA) (Table 1). The microbiology laboratory alerted the infection control department of a presumptive positive C. auris from a clinical urine culture from the same patient. Enhanced mitigation strategies were initiated in regards to cleaning and disinfection.

An exposure investigation was also conducted using a point prevalence approach. Surveillance cultures were obtained from inpatients currently admitted to the same unit as the index patient. Axilla/groin specimens were collected for C. auris testing, and rectal specimens were collected for CP-CRO gene testing (CRE Real-Time PCR).

Results

Eighteen patients in addition to the index patient were hospitalized on the acute medicine unit. One patient refused testing for CP-CRO; therefore, 17 patients were tested for CP-CRO, and 18 patients were tested for C. auris. Neither CP-CRO nor C. auris were recovered from any patient.

Conclusion

A patient co-infected with C. auris and multiple CP-CRO was identified by clinical and routine surveillance cultures at Johns Hopkins Hospital. Travel screening allowed proactive isolation upon presentation. Enhanced infection control measures were implemented and a point prevalence surveillance study was conducted on the general acute care medicine inpatient unit. No transmission of either C. auris or CP-CRO was detected, likely due in part to rapid identification and strict infection control measures.

Disclosures

All authors: No reported disclosures.

Emergence and establishment of KPC-2-producing ST11 Klebsiella pneumoniae in a general hospital in Shanghai, China

The aim of this study was to investigate the characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP) collected during an outbreak in a Chinese teaching hospital and to provide insights into the prevention and control of nosocomial infection. We collected unique CRKP clinical isolates from 2009 to 2013. Antibiotic-resistant genes were identified by polymerase chain reaction (PCR) and sequencing. The isolates were typed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Plasmids were classified using a PCR-based incompatibility/replicon typing method and a replicon sequence typing method. Conjugation experiments were performed to evaluate the transferability of carbapenem-resistant genes. Whole genome sequencing (WGS) was conducted to further investigate the genetic background of the isolates. Infection control practices were reviewed throughout the study period. Klebsiella pneumoniae sequence type (ST) 11 emerged in 2010 and acquired the bla _KPC-2 gene by 2011. From 2011 to 2013, ST11 KPC-2-producing CRKP (G type) prevailed as the most common CRKP in our hospital, causing a prolonged outbreak. The majority of these CRKP strains possess an IncFII plasmid, with Tn1721-bla _KPC-2-ΔTn3-IS26 bearing the genetic structure for bla _KPC-2. Infection prevention control measures available at the time contained the initial outbreak, but had no effect on the spread of CRKP later. This study demonstrated the seriousness concerning the spread of KPC-2-producing ST11 CRKP in a Chinese hospital, indicating that current prevention and control strategies for carbapenem-resistant Enterobacteriaceae (CRE) nosocomial infection need to be investigated and adjusted.

Isolation of multiple carbapenemase-producing Gram-negative bacilli from a patient recently hospitalized in Nigeria

A 29-year-old female transferred to a tertiary care hospital in Winnipeg, Canada, after a prolonged period of hospitalization in Nigeria was found to be colonized with a VIM-2-producing Pseudomonas aeruginosa, a NDM-1-producing Klebsiella pneumoniae, and an OXA-181-producing Escherichia coli. Detection of carbapenemase-producing organisms from a rectal swab was accomplished by screening with chromogenic media, followed by confirmation with the Rapid CARB Screen kit (Rosco Diagnostica, Taastrup, Denmark). This case illustrates the need for clinical microbiology laboratories to have a protocol in place to screen patients for carbapenemase producers, even in countries where these organisms are rarely encountered.