Open Access Research article

Comparison of PCR/Electron spray Ionization-Time-of-Flight-Mass Spectrometry versus Traditional Clinical Microbiology for active surveillance of organisms contaminating high-use surfaces in a burn intensive care unit, an orthopedic ward and healthcare workers

Heather C Yun12*, Rachael E Kreft3, Mayra A Castillo1, Garth D Ehrlich34*, Charles H Guymon5, Helen K Crouch1, Kevin K Chung25, Joseph C Wenke5, Joseph R Hsu5, Tracy L Spirk3, J William Costerton3, Katrin Mende16 and Clinton K Murray12

Author Affiliations

1 San Antonio Military Medical Center, San Antonio, TX, USA

2 Uniformed Services University, Bethesda, MD, USA

3 Center for Genomic Sciences, Allegheny Singer Research Institute, Pittsburgh, PA, USA

4 Departments of Microbiology and Immunology, and Otolaryngology Head and Neck Surgery, Drexel University College of Medicine, Pittsburgh, PA, USA

5 US Army Institute of Surgical Research, San Antonio, TX, USA

6 Infectious Disease Clinical Research Program, Uniformed Services University, Bethesda, MD, USA

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BMC Infectious Diseases 2012, 12:252  doi:10.1186/1471-2334-12-252

Published: 10 October 2012



Understanding nosocomial pathogen transmission is restricted by culture limitations. Novel platforms, such as PCR-based electron spray ionization-time-of-flight-mass spectrometry (ESI-TOF-MS), may be useful as investigational tools.


Traditional clinical microbiology (TCM) and PCR/ESI-TOF-MS were used to recover and detect microorganisms from the hands and personal protective equipment of 10 burn intensive care unit (ICU) healthcare workers providing clinical care at a tertiary care military referral hospital. High-use environmental surfaces were assessed in 9 burn ICU and 10 orthopedic patient rooms. Clinical cultures during the study period were reviewed for pathogen comparison with investigational molecular diagnostic methods.


From 158 samples, 142 organisms were identified by TCM and 718 by PCR/ESI-TOF-MS. The molecular diagnostic method detected more organisms (4.5 ± 2.1 vs. 0.9 ± 0.8, p < 0.01) from 99% vs. 67% of samples (p < 0.01). TCM detected S. aureus in 13 samples vs. 21 by PCR/ESI-TOF-MS. Gram-negative organisms were less commonly identified than gram-positive by both methods; especially by TCM. Among all detected bacterial species, similar percentages were typical nosocomial pathogens (18-19%) for TCM vs. PCR/ESI-TOF-MS. PCR/ESI-TOF-MS also detected mecA in 112 samples, vanA in 13, and KPC-3 in 2. MecA was associated (p < 0.01) with codetection of coagulase negative staphylococci but not S. aureus. No vanA was codetected with enterococci; one KPC-3 was detected without Klebsiella spp.


In this pilot study, PCR/ESI-TOF-MS detected more organisms, especially gram-negatives, compared to TCM, but the current assay format is limited by the number of antibiotic resistance determinants it covers. Further large-scale assessments of PCR/ESI-TOF-MS for hospital surveillance are warranted.

PCR/ESI-TOF-MS; Ibis; Microbiology; Contamination; Environment