Related Experiment Video
Updated: Dec 1, 2025
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Correlation Between Patients With Methicillin-Resistant Staphylococcus aureus (MRSA) Nares Colonization and MRSA
Jacquelyn Brondo1, Kathleen Morneau1, Teri Hopkins1
1South Texas Veterans Health Care System, San Antonio, TX, USA.
Abstract:
Infectious Diseases Society of America diabetic foot infection (DFI) guidelines indicate empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage for patients with a history of MRSA infection, when local prevalence of MRSA is high, or infection is clinically severe. These recommendations may lead to overutilization of empiric MRSA coverage, which can result in serious consequences. A strong negative predictive value (NPV) has been reported in literature for pneumonia, and recently, for all anatomical sites of infection. While these findings are promising, further validation is needed before clinicians may confidently use MRSA nares to guide empiric therapy for DFIs. A retrospective electronic medical record review was completed between October 1, 2013 and October 1, 2019. Patients met inclusion criteria if they were at least 18, admitted with a DFI, had MRSA nares test results, and DFI cultures. Patients were excluded if pregnant or MRSA infection within 1 year prior to index admission for DFI. A total of 200 patients met inclusion criteria. The majority of study participants were male with a mean age of 63. NPV of MRSA nares for MRSA DFIs was determined to be 94% and positive predictive value 58%. Sensitivity and specificity were 56% and 94%, respectively. Results of this study are consistent with prior literature supporting strong correlation of NPV for MRSA nares. The DFIs evaluated suggest a strong NPV of MRSA nares for MRSA DFIs, which may allow for faster de-escalation of empiric anti-MRSA antibiotic therapy and lower risk of adverse events associated with anti-MRSA therapy.
Insights
A negative nasal swab for methicillin-resistant Staphylococcus aureus (MRSA) effectively rules out MRSA diabetic foot infections (DFIs), allowing for quicker de-escalation of antibiotic therapy.
Area of Science:
- Infectious Diseases
- Clinical Microbiology
- Dermatology
Background:
- Current guidelines recommend empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage for diabetic foot infections (DFIs) in certain situations.
- Overutilization of empiric MRSA coverage can lead to adverse events and increased healthcare costs.
- Nasal MRSA testing has shown a high negative predictive value (NPV) for other infections, but requires validation for DFIs.
Purpose of the Study:
- To evaluate the negative predictive value (NPV) of methicillin-resistant Staphylococcus aureus (MRSA) nasal swab results for guiding empiric antibiotic therapy in patients with diabetic foot infections (DFIs).
Main Methods:
- Retrospective electronic medical record review of 200 patients admitted with DFIs between October 2013 and October 2019.
- Inclusion criteria: age ≥18, DFI diagnosis, available MRSA nares test, and DFI cultures. Exclusion criteria: pregnancy or prior MRSA infection within one year.
- Analysis of MRSA nares test results against DFI culture results to determine NPV, PPV, sensitivity, and specificity.
Main Results:
- The study included 200 patients, predominantly male, with a mean age of 63.
- The negative predictive value (NPV) of MRSA nares for MRSA DFIs was 94%.
- The positive predictive value (PPV) was 58%, with sensitivity at 56% and specificity at 94%.
Conclusions:
- The findings support a strong negative predictive value (NPV) of MRSA nasal screening for methicillin-resistant Staphylococcus aureus diabetic foot infections.
- A negative MRSA nares test may allow for timely de-escalation of empiric anti-MRSA antibiotic therapy.
- This approach could potentially reduce the risk of adverse events associated with prolonged MRSA treatment.
