Rapid Test to Detect Staphylococcus Aureus in Blood and Wound Infections

GeneXpert in Studying Staphylococcus Aureus Infections at the Michael E. DeBakey Medical Center, Houston, Texas

The purpose of this study is to determine whether the Cepheid GeneXpert system accurately detects Methicillin-Resistant and -Susceptible Staphylococcus aureus in blood cultures and wound swabs.

Study Overview

• Status: Completed
• Conditions: Bacteremia; Staphylococcus Aureus; Staphylococcal Skin Infections

Detailed Description

Staphylococcus aureus (SA) remains a major pathogen for human beings, causing infections of skin, soft tissue, bone, and other organs. Bacteremia due to this organism is common, and often occurs in association with medical interventions such as intravenous lines and implantable devices. With the increase in methicillin-resistant S. aureus (MRSA), there has been increasing dependence upon vancomycin, a drug that is inferior to the beta-lactams in its activity against methicillin-susceptible S. aureus (MSSA). If the microbiology laboratory had the ability to identify S. aureus (SA) and its drug susceptibility within hours rather than days, focused therapy would be possible earlier in the course of illness. Clinicians would be able to discontinue antibiotics when SA is not present, to discontinue other broad-spectrum antibiotics when SA is present, or to replace empiric vancomycin with nafcillin when MSSA is identified.

The GeneXpert system (Cepheid) uses real-time PCR to detect genes that encode Staphylococcus aureus protein A (SPA), the staphylococcal cassette chromosome (SCC) and methicillin resistance (mecA). All blood cultures with Gram stain revealing Gram positive cocci in clusters will be tested by PCR the day they became positive. Wound swabs submitted for routine bacteriologic culture will be tested within 48 hr of collection. Results will be compared with those of standard bacteriologic culture. In addition, discrepancies between the GeneXpert and wound culture results will be reviewed in the medical record to ascertain whether antibiotic use at the time of specimen collection is associated with false positive results in which the wound culture yields no S. aureus but PCR detects staphylococcal DNA components.

In the second phase of the study, PCR results for wound swabs and blood cultures will be reported to physicians immediately upon completion of the reaction. The clinical impact of early identification of S. aureus will be determined by comparing antibiotic treatment and clinical outcome of patients for whom early identification was available with those of patients for whom conventional bacteriological culture was the sole diagnostic test.

• Study Type: Observational
• Enrollment (Actual): 260

Contacts and Locations

Study Locations

• United States
  • Texas
    • Houston, Texas, United States, 77030
      • Michael E. DeBakey VA Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Probability Sample

Study Population

The study population includes adult and geriatric patients at the Michael E. DeBakey VA Medical Center for have suspected blood and wound infections.

Description

Inclusion Criteria:

• Positive blood culture with Gram stain revealing Gram positive cocci in clusters
• All wound swabs submitted to the microbiology lab for standard bacteriologic culture may be included.

Exclusion Criteria:

• Blood cultures that became positive more than 24 hours previously
• Wound swabs for which over 48 hours have passed from the time of collection

Study Plan

How is the study designed?

Design Details

• Time Perspectives: Retrospective

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
concordance between PCR results and those of standard bacteriologic culture	1 year

Secondary Outcome Measures

Outcome Measure	Time Frame
Impact of early identification of S. aureus on the antibiotics prescribed by physicians and subsequent clinical outcome.	1 year

Collaborators and Investigators

• Sponsor: Michael E. DeBakey VA Medical Center
• Collaborators: Baylor College of Medicine; Cepheid
• Investigators: Principal Investigator: Daniel M Musher, MD, Michael E. DeBakey VA Medical Center; Study Chair: Mark Parta, MD, Michael E. DeBakey VA Medical Center

Study record dates

Study Major Dates

• Study Start: April 1, 2008
• Primary Completion (Actual): August 1, 2009
• Study Completion (Actual): August 1, 2010

Study Registration Dates

• First Submitted: September 9, 2010
• First Submitted That Met QC Criteria: September 9, 2010
• First Posted (Estimate): September 10, 2010

Study Record Updates

• Last Update Posted (Estimate): September 10, 2010
• Last Update Submitted That Met QC Criteria: September 9, 2010
• Last Verified: October 1, 2008

More Information

Terms related to this study

• Keywords: polymerase chain reaction
• Additional Relevant MeSH Terms: Pathologic Processes; Skin Diseases; Systemic Inflammatory Response Syndrome; Inflammation; Disease Attributes; Connective Tissue Diseases; Bacterial Infections; Bacterial Infections and Mycoses; Gram-Positive Bacterial Infections; Sepsis; Suppuration; Skin Diseases, Bacterial; Infections; Communicable Diseases; Cellulitis; Skin Diseases, Infectious; Staphylococcal Skin Infections; Bacteremia; Staphylococcal Infections
• Other Study ID Numbers: H-23059