Cytoskeletal Tropomyosin as a Biomarker in Infection.

Background: Current diagnostics of infection (CDI) heavily relies on detection of the disease-causing organism. The objective of this study was to investigate a cytoskeletal protein, tropomyosin (Tpm), as a CDI biomarker.

Methods: Fecal Tpm was tested by monoclonal antibodies (mAbs) in a 12-month prospective study. Remnant diarrheal clinical specimens and relevant clinical data were collected. The CDI positive (CDI, n = 230) and CDI negative (CDI, n = 228) groups were composed of samples testing positive or negative by polymerase chain reaction (PCR) (Xpert /Epi, Cepheid), respectively. The other enteric pathogen (OEP) group (n = 52) was composed of specimens tested for the presence of other enteric pathogens or parasites by routine testing methods. Extracted fecal Tpm was detected by Western blot and the results were correlated with CDI based on clinical and microbiology laboratory data.

Results: A total of 510 stool specimens were tested. Tpm is not stable in stool, suggesting the utility of fresh specimens. In the CDI group, specificity and sensitivity of Tpm detection in correlation with a CDI were 93.2% and 53.7%, respectively, when only "true CDI" and "not CDI" were analyzed (110 samples). For CDI samples, 23% did not satisfy CDI clinical signs. Tpm positives in the CDI group (8.3%) had inflammatory bowel diseases.

Conclusion: Tpm has a potential role as a CDI biomarker in combination with PCR and an appropriate clinical evaluation. However, non-muscle Tpm, as a biomarker for CDI, suffers from a low sensitivity in our study. Therefore further investigation using larger cohorts is needed.