Derrick J. Chen
· Associate Professor (CHS), Medical Director of MicrobiologyVerifiedUniversity of Wisconsin-Madison · Pathology and Laboratory Medicine
Active 2009–2026
About
Derrick J. Chen is an Associate Professor (CHS) at the Department of Pathology and Laboratory Medicine at the University of Wisconsin School of Medicine and Public Health. He serves as the Medical Director of Microbiology. His research interests include the molecular detection of Helicobacter pylori and macrolide resistance. His clinical interests are focused on Clinical Microbiology, where he applies molecular and microbiological techniques to diagnose infectious diseases. Dr. Chen's work involves utilizing PCR, culture, and antigen detection methods for the diagnosis of Legionellosis, and he has contributed to understanding the clinical significance of coryneform Gram-positive rods from blood, as well as the study of small-bowel polyps. His expertise and research aim to improve diagnostic methods and understanding of infectious diseases within clinical microbiology.
Research topics
- Medicine
- Biology
- Microbiology
- Internal medicine
- Intensive care medicine
- Virology
- Immunology
- Obstetrics
- Pathology
- Anesthesia
- Emergency medicine
Selected publications
Open Forum Infectious Diseases · 2026-01-01
articleOpen accessAbstract Background Lung transplant (LTx) recipients require lifelong immunosuppression and monitoring for respiratory infections and graft rejection. The American Society of Transplantation recommends molecular tests when evaluating pneumonia, and in 2023 our lab implemented the BioFire FilmArray Pneumonia panel, a multiplex PCR assay designed for lower respiratory tract specimens including bronchoalveolar lavage (BAL) fluid. This test does not distinguish pathogenic from colonizing organisms and may lead to excessive antimicrobial use or inappropriate reduction in immunosuppression. Methods This retrospective cohort included adult LTx recipients from February 2023 to October 2023 with simultaneous BAL bacterial culture and PCR BioFire. PCR positivity was compared by treatment team reported bronchoscopy indication: rejection surveillance or infection evaluation. PCR-culture concordance was defined as both methods identifying the same PCR targeted bacterial pathogens. Pre/post-test antimicrobials and mycophenolate dosing for immunosuppression were compared. R version 4.4.1 was used for statistical analyses: bivariate logistic regression to assess factors associated with PCR positivity and chi-square to evaluate categorical variables. Results We included 95 LTx recipients [mean age 58 years, 20% single LTx, 94% basaliximab induction immunosuppression, 85% LTx in 2015 or later, 10% diagnosed with rejection in prior 90 days]. The PCR panel was collected for rejection surveillance in 41% and infection evaluation in 59%, and there was no difference in PCR positivity (33.3% v 37.5%; p=0.84) (Table 1). PCR-culture concordance was high (Table 2). Antimicrobials were more frequently started (35.3% v 14.8%; p=0.04) and broadened (17.6% v 3.3%; p=0.04) after a positive than negative PCR; there were no differences in narrowing antimicrobials or decreasing mycophenolate dosing (Table 3). There were no significant factors associated with PCR positivity (Table 4). Conclusion While LTx recipients are at high risk for pulmonary infections, the PCR panel was frequently positive regardless of the pre-test concern of infection. The PCR panel should not be routinely ordered during rejection surveillance in the absence of clinical concern for infection. Disclosures All Authors: No reported disclosures
American Journal of Clinical Pathology · 2025-08-03
articleSenior authorOBJECTIVE: Chlamydia trachomatis and Neisseria gonorrhoeae present substantial public health challenges. Accurate diagnostic testing is essential to prevent misdiagnosis and unnecessary treatment. Although nucleic acid amplification tests offer excellent performance, they are not infallible. This study sought to evaluate the semiquantitative utility of relative light unit (RLU) values from the Hologic Aptima Combo 2 Assay to improve the diagnostic accuracy of testing for C trachomatis and N gonorrhoeae. METHODS: Data were analyzed from January 2021 to December 2021. Manufacturer guidelines define results as positive if the RLU value is above 100 for C trachomatis only, above 150 for N gonorrhoeae only, and above 250 for dual C trachomatis and N gonorrhoeae detection; equivocal if the RLU value is 25 to 99 for C trachomatis, 60 to 149 for N gonorrhoeae, and 85 to 249 for both; and negative if the RLU value is below 25 for C trachomatis, below 60 for N gonorrhoeae, and below 85 for both. Manufacturer guidance recommends repeat testing only for equivocal results. In contrast, the University of Wisconsin University Hospital adopted a modified criterion, classifying all results with an RLU value at or below 900 as equivocal and requiring repeat testing. RESULTS: In this retrospective review of 20 875 Aptima Combo 2 assays performed from January to December 2021, 7 patients had initial positive results, with RLU values at or below 900. Of these, 5 were ultimately determined to be false positives. CONCLUSIONS: These findings demonstrate that expanding the definition of equivocal results to include low positive RLU values (≤900) increases identification of false positives with minimal additional repeat testing. This modified approach may improve diagnostic specificity and reduce unnecessary treatment and patient anxiety.
SSRN Electronic Journal · 2025-01-01
preprintOpen accessSenior authorJournal of Clinical Microbiology · 2025-03-25 · 3 citations
articleOpen accessSenior authorABSTRACT Malaria and babesiosis are significant parasitic infections, requiring timely diagnosis to avoid severe complications. This study retrospectively compared hematology thin smears (HS) with parasitology thick and thin blood smears (PS), the gold standard for diagnosis, to evaluate HS’s performance in detecting Plasmodium and Babesia infections. Of 529 cases with paired HS and PS testing, HS demonstrated 93.3% sensitivity and 99.8% specificity, with 97.7% positive and 99.4% negative predictive values. When only considering new diagnoses, HS and PS were 100% concordant. No significant difference was found in percent parasitemia between HS and PS, highlighting HS as a reliable diagnostic tool in settings where PS or other diagnostic modalities may not be readily available. IMPORTANCE This study demonstrates that hematology thin smears—often available in laboratories that may not have other means of diagnosing blood parasite infections such as parasitology thick and thin smears, rapid diagnostics tests, or polymerase chain reaction—are an accurate and reliable way to diagnose Plasmodium and Babesia infections in a low prevalence setting.
Diagnostic Microbiology and Infectious Disease · 2025-10-18
articleSenior authorReviewer response for version 1
2023-06-05
peer-reviewOpen accessA patient suffered a non-fatal wet drowning in a freshwater lake and developed bacteremia several days later. Blood culture grew a Gram-negative rod that could not be identified by MALDI-TOF MS. 16S ribosomal RNA sequencing of the isolate identified the microbe as Hydrogenophaga laconesensis––an environmental microbe commonly found in freshwater. The recovery of multiple pathogenic microorganisms (although not Hydrogenophaga laconesensis) from culture of respiratory specimens prompted the initiation of antibiotic therapy with cefepime and, later, vancomycin. The patient's clinical course gradually improved over the course of two weeks and she was ultimately discharged home with minimal sequelae. To our knowledge, this is the first evidence of human infection with bacteria in the Hydrogenophaga genus. Hydrogenophaga may be considered in cases of freshwater near-drowning, and MALDI-TOF MS databases should be updated to include Hydrogenophaga laconesensis.
2023
- Medicine
- Intensive care medicine
- Microbiology
A patient suffered a non-fatal wet drowning in a freshwater lake and developed bacteremia several days later. Blood culture grew a Gram-negative rod that could not be identified by MALDI-TOF MS. 16S ribosomal RNA sequencing of the isolate identified the microbe as Hydrogenophaga laconesensis––an environmental microbe commonly found in freshwater. The recovery of multiple pathogenic microorganisms (although not Hydrogenophaga laconesensis) from culture of respiratory specimens prompted the initiation of antibiotic therapy with cefepime and, later, vancomycin. The patient’s clinical course gradually improved over the course of two weeks and she was ultimately discharged home with minimal sequelae. To our knowledge, this is the first evidence of human infection with bacteria in the Hydrogenophaga genus. Hydrogenophaga may be considered in cases of freshwater near-drowning, and MALDI-TOF MS databases should be updated to include Hydrogenophaga laconesensis.
2023-08-11
preprintOpen accessA patient suffered a non-fatal wet drowning in a freshwater lake and developed bacteremia several days later. Blood culture grew a Gram-negative rod that could not be identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). 16S ribosomal RNA sequencing of the isolate identified the microbe as Hydrogenophaga laconesensis––an environmental microbe commonly found in freshwater. The recovery of multiple pathogenic microorganisms (although not H. laconesensis) from culture of respiratory specimens prompted the initiation of antibiotic therapy with cefepime and, later, vancomycin. The patient’s clinical course gradually improved over the course of two weeks and she was ultimately discharged home with minimal sequelae. To our knowledge, this is the first evidence of human infection with bacteria in the Hydrogenophaga genus. Hydrogenophaga may be considered in cases of freshwater near-drowning, and MALDI-TOF MS databases should be updated to include H.laconesensis.
Access Microbiology · 2023 · 3 citations
- Microbiology
- Medicine
- Anesthesia
.
Clinical Significance of BD Bactec FX Blood Culture Incubation Beyond 96 Hours (4 Days)
Journal of Clinical Microbiology · 2022-06-27 · 8 citations
articleOpen accessSenior authorCorresponding= 13) resulted in antibiotic adjustments based on the +BC; 4 of these had previous positive cultures. Of the remaining 37 clinically significant +BC >96 h for which no antibiotic changes were made, 32 patients had previous positive cultures. The majority (98%) of BC bottles were positive before 96 h. For isolates that required >96 h, most (56%) were considered clinically significant, including S. aureus and E. coli cultures. Changes to antibiotic therapy were made in a minority (26%) of clinically significant cases. Based on these findings, under routine conditions, laboratories using BD Bactec FX should maintain a 120 h incubation period.
Frequent coauthors
- 18 shared
William M. Rehrauer
University of Wisconsin–Madison
- 17 shared
Brittney Jung‐Hynes
UW Health University Hospital
- 16 shared
Adam L. Bailey
- 8 shared
Jeannina A. Smith
- 8 shared
Alexander J. Lepak
- 8 shared
Patti J. Anderson
UW Health University Hospital
- 8 shared
Kelly M. Koglin
UW Health University Hospital
- 8 shared
Megan A. Luebbe
UW Health University Hospital
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