591 - Sniffing Out Staph: Correlation between MRSA Nasal Surveillance and Wound Cultures in Pediatric Patients Admitted for Skin and Soft Tissue Infections and Musculoskeletal Infections

Publication Number: 2576.591

Kristin Natoli, K. Hovnanian Children's Hospital at Jersey Shore University Medical Center, Matawan, NJ, United States; Alexandra Altamura, Hassenfeld Children's Hospital at NYU Langone, Weehawken, NJ, United States; Mariawy Riollano Cruz, Maria Fareri Children's Hospital at Westchester Medical Center, Valhalla, NY, United States; Sarah Rawstron, K. Hovnanian Children's Hospital at Jersey Shore University Medical Center, Neptune, NJ, United States

Background: Empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage is often included in treating skin and soft tissue infections (SSTI) and musculoskeletal infections (MSKI). MRSA nasal surveillance (MNS) is a popular tool aiding in both antimicrobial selection and stewardship. In adults, current literature shows MNS yields a high negative predictive value in cases of both SSTI and pneumonia. Pediatric studies are limited, thus prompting us to evaluate the concordance between MNS and wound culture in inpatient pediatric admissions.

Objective: The purpose of this study is to determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MNS compared to subsequent wound cultures in pediatric patients admitted with SSTI/MSKI, to help guide future MNS use and understand its role in antimicrobial stewardship.

Design/Methods: Retrospective chart review included patients aged 0-18 years admitted from 8/2023-8/2024 with a diagnosis of SSTI and/or MSKI, with antibiotic use 48 hours or less before MNS collection. Patient demographics, infection type, MNS result, and wound culture result were recorded. Excluded were patients with respiratory or CNS infections, endocarditis, SIRS and/or sepsis, previous MRSA and/or MSSA infections, a history of immunodeficiency and/or immunosuppressive therapy, and surgery and/or hardware placement within the preceding year. Analysis was performed using a 2 x 2 contingency table comparing MNS (PCR-based) detection of Staph aureus (MRSA vs. non-MRSA/no S. aureus) against the reference standard (wound culture positive for MRSA vs. non-MRSA). Sensitivity, specificity, PPV, NPV, and respective 95% confidence intervals were calculated.

Results: Of the thirty-one specimens, PCR detected 1 of 9 culture-confirmed MRSA cases, yielding a sensitivity of 11.1% (95% CI: 2.0-43.5%). All of the 22 culture-negative specimens had a negative corresponding PCR, yielding a specificity of 100% (95% CI: 85.1-100%). The PPV was 100% (95% CI: 20.7-100%). However, the NPV was 73.3% (95% CI: 85.1-100%); one in three negative PCR results had MRSA-positive culture. While MNS PCR produced no false positives, the majority of true MRSA infections were missed. Of note, wider confidence intervals are likely secondary to a small sample size.

Conclusion(s): Our analysis showed that a positive MNS can be interpreted as definite evidence of MRSA, but a negative MNS cannot reliably exclude infection. Therefore, when clinicians choose antimicrobial coverage before definitive wound culture results, MRSA coverage should still be considered even in the setting of a negative PCR.

Table 1
Comparison of results between gold-standard (wound culture) and PCR (MRSA nasal surveillance test).

Table 2
Sensitivity, specificity, PPV, and NPV results for MRSA nasal surveillance PCR test.