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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Utility of Methicillin-Resistant Staphylococcus aureus Nares Screening for Patients with a Diabetic Foot Infection
Kari A Mergenhagen1, Michael Croix2, Kaitlyn E Starr3
1Veterans Affairs Western New York Healthcare System, Department of Pharmacy, Buffalo, New York, USA Kari.Mergenhagen@va.gov Jsellick@buffalo.edu.
Abstract:
Treatment of suspected methicillin-resistant Staphylococcus aureus (MRSA) is a cornerstone of severe diabetic foot infections; however, antibiotics can be associated with toxicity. The objective of this study was to determine the negative predictive value (NPV) of MRSA nares screening in the determination of subsequent MRSA in patients with a diabetic foot infection. This was a retrospective cohort study across Veterans Affairs (VA) medical centers from 1 January 2007 to 1 January 2018. Data from patients with an International Classification of Diseases (ICD) code for a diabetic foot infection with MRSA nares screening, and subsequent cultures were evaluated for the presence of MRSA. NPVs were calculated for the entire cohort, as well as for a subgroup representing deep cultures. Additionally, the distribution of all pathogens isolated from diabetic foot infections was determined. A total of 8,163 episodes were included in the analysis for NPV. The NPV of MRSA nares screening for MRSA diabetic foot infection was 89.6%. For the deep cultures, the NPV was 89.2%. The NPV for cultures originating from the foot was 89.7%, and the NPV for those originating from the toe was 89.4%. There were 17,822 pathogens isolated from the diabetic foot cultures. MRSA was isolated in 7.5% of cultures, and methicillin-susceptible S. aureus was isolated in 24.8%. Enterococcus was identified in 14.7% of cultures, Proteus in 7.3%, and Pseudomonas in 6.8% of cultures. Given the high NPVs, the use of MRSA nares screening may be appropriate as a stewardship tool for deescalation and avoidance of empirical anti-MRSA therapy in patients who are not nasal carries of MRSA.
Insights
Nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) effectively rules out MRSA diabetic foot infections, with a negative predictive value around 89%. This finding supports using nasal screening to guide antibiotic therapy and reduce unnecessary MRSA treatment.
Area of Science:
- Infectious Diseases
- Dermatology
- Clinical Microbiology
Background:
- Diabetic foot infections (DFIs) often require treatment for methicillin-resistant Staphylococcus aureus (MRSA).
- Antibiotic use for MRSA can lead to toxicity, necessitating careful patient selection.
- Nasal carriage screening is a common method to identify MRSA carriers.
Purpose of the Study:
- To evaluate the negative predictive value (NPV) of MRSA nares screening in patients with diabetic foot infections.
- To determine if MRSA nares screening can reliably predict the absence of MRSA in DFIs.
- To assess the utility of MRSA nares screening as a tool for antibiotic stewardship in DFIs.
Main Methods:
- Retrospective cohort study of Veterans Affairs medical centers (2007-2018).
- Included patients with diabetic foot infections, MRSA nares screening, and subsequent cultures.
- Calculated NPV for MRSA detection in DFIs based on nasal screening results.
Main Results:
- The overall NPV of MRSA nares screening for MRSA DFI was 89.6%.
- NPVs were similar for deep tissue cultures (89.2%), foot cultures (89.7%), and toe cultures (89.4%).
- Methicillin-susceptible S. aureus was the most common S. aureus isolate (24.8%), followed by MRSA (7.5%).
Conclusions:
- MRSA nares screening demonstrates a high NPV for ruling out MRSA in diabetic foot infections.
- These findings suggest MRSA nares screening can be a valuable tool for deescalating antibiotic therapy.
- Utilizing nasal screening may help avoid unnecessary empirical anti-MRSA treatment in non-carriers.
