569 - Mycoplasma pneumoniae Testing, Diagnosis, and Treatment in Hospitalized Children Across the US: A 10-year Retrospective Analysis

Publication Number: 2554.569

Hannah K. Bassett, Stanford University School of Medicine, Redwood City, CA, United States; Nymisha Chilukuri, Stanford University School of Medicine, San Francisco, CA, United States; Christine Cunningham, Stanford University School of Medicine, Palo Alto, CA, United States; Jessica M. Allan, Palo Alto Medical Foundation/ Lucile Packard Children's Hospital at Stanford, San Mateo, CA, United States; Prachi M. Keni-McCray, Lucile Packard Children's Hospital Stanford, Menlo Park, CA, United States; Nicholas P. Marshall, Stanford Medicine | Children’s Health, Palo Alto, CA, United States; Natalie M. Pageler, Stanford University School of Medicine, Sunnyvale, CA, United States; Hayden T.. Schwenk, Stanford University School of Medicine, Stanford, CA, United States; Victor Ritter, Stanford University School of Medicine, Palo Alto, CA, United States; Alan Schroeder, Stanford University School of Medicine, Palo Alto, CA, United States

Background: Respiratory illnesses are the most common and costly reasons children are hospitalized in the US. Recent reports have noted increases in Mycoplasma pneumoniae (M. pneumoniae), an infection that is not susceptible to the empiric antibiotics recommended to treat typical community acquired pneumonia (CAP) in children. An understanding of M. pneumoniae testing and treatment patterns is needed to contextualize these reported increases in diagnoses, support diagnostic and antimicrobial stewardship, and inform patient care.

Objective: To describe temporal trends in testing, diagnosis, and treatment of M. pneumoniae in children hospitalized for respiratory illnesses in the US.

Design/Methods: We conducted a retrospective cohort study using Epic Cosmos, a dataset created in collaboration with health systems using Epic. We identified inpatient encounters between 1/1/2016-10/13/2025 for children < 18 years with a diagnosis code for CAP, asthma, or bronchiolitis. Our outcomes were the annual proportion of these encounters with: 1) at least one M. pneumoniae test (PCR or antibody) obtained between 5 days prior to admission and discharge (test results are less available due to data privacy protections); 2) a diagnosis code for M. pneumoniae; and 3) at least one dose of an antibiotic targeted against M. pneumoniae. We also assessed annual testing variability (interquartile range [IQR], median) across institutions with >/=50 encounters.

Results: In 1,371,992 encounters (982,017 patients from 255 hospitals), 26.5% (n=363,673) had at least one M. pneumoniae test, increasing from 7.8% (n=8070; 2016) to 39.5% (n=55,438; 2025). In total, 1.7% (n=23,010) had an M. pneumoniae diagnosis code, increasing from 1.1% (n=1128; 2016) to a peak of 5.3% (n=10,130; 2024)(Figure 1), with proportional increases across CAP, asthma, and bronchiolitis (Table 1). Encounters with M. pneumoniae targeted antibiotics were variable over time, but peaked at 14.4% (n=27,758; 2024). Testing frequency varied widely across institutions every year (Figure 2), with a median of 47.1% (IQR 15.5%-61.5%) in 2025.

Conclusion(s): We found a 5-fold increase in testing for M. pneumoniae in children hospitalized for respiratory illnesses, with striking variability in testing frequency across hospitals. Diagnoses increased notably over the past two years. Antibiotic use followed a similar recent trend, but has been considerably higher than diagnosis frequency over time. A better understanding of drivers of testing and treatment, as well as the relationship between testing, treatment, and outcomes, is needed to define best practices and ensure resource stewardship.

Figure 1. Temporal trends in the proportion of pediatric hospitalizations for respiratory illnesses with a test, diagnosis, or antibiotic for M. pneumoniae
M. pneumoniae ICD-10 diagnosis codes included: A49.3, B96.0, J15.7, J20.2
M. pneumoniae antibiotics included: azithromycin (excluding ophthalmic), clarithromycin, doxycycline (excluding topical), ciprofloxacin (excluding otic and ophthalmic), levofloxacin (excluding inhalational and ophthalmic), and moxifloxacin (excluding ophthalmic)

Table 1. Temporal trends in M. pneumoniae diagnoses as a proportion of pediatric hospitalizations with a diagnosis code for community acquired pneumonia, asthma, or bronchiolitis
*Through October 13, 2025

Figure 2. Temporal trends in the institutional variability of testing for M. pneumoniae in children hospitalized for respiratory illnesses*
*Analysis limited to institutions that had at least 50 encounters meeting inclusion criteria each year