Background Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent worldwide and can cause severe diseases. MRSA is associated with other antibiotic resistance. COVID-19 pandemic increased antimicrobial resistance in adult patients. Only a few data report the antimicrobial susceptibility of S. aureus in the Italian pediatric population, before and during the COVID-19 pandemic. Methods We included all the S. aureus positive samples with an available antibiogram isolated from pediatric patients (< 18 years old) in a tertiary care hospital in Milan, Italy, from January 2017 to December 2021. We collected data on demographics, antimicrobial susceptibility, and clinical history. We compared methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA strains. We calculated the frequency of isolation by year. The incidence of isolates during 2020 was compared with the average year isolation frequency using the univariate Poisson test. We compared the proportion of MRSA isolates during 2020 to the average proportion of other years with the Chi-squared test. Results Our dataset included a total of 255 S. aureus isolated from 226 patients, 120 (53%) males, and 106 (47%) females, with a median age of 3.4 years (IQR 0.8 – 10.5). The mean isolation frequency per year was 51. We observed a significant decrease of isolations during 2020 (p = 0.02), but after adjusting for the total number of hospitalization per year there was no evidence that the incidence changed. Seventy-six (30%) S. aureus were MRSA. Twenty (26%) MRSA vs 23 (13%) MSSA (p = 0.02) were hospital-acquired. MRSA strains showed higher resistance to cotrimoxazole, clindamycin, macrolides, levofloxacin, gentamicin, and tetracyclin than MSSA strains. None of MRSA were resistant to linezolid and vancomycin, one was resistant to daptomycin. The proportion of MRSA did not change during the COVID-19 pandemic. The overall clindamycin resistance was high (17%). Recent antibiotic therapy was related to MRSA infection. Conclusion The proportion of MRSA did not change during the COVID-19 pandemic and remained high. Clindamycin should not be used as an empirical MRSA treatment due to its high resistance.

The novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection has milder presentation in children than in adults, mostly requiring only supportive therapy. The immunopathogenic course of COVID-19 can be divided in two distinct but overlapping phases: the first triggered by the virus itself and the second one by the host immune response (cytokine storm). Respiratory failure or systemic involvement as Multisystem Inflammatory Syndrome in Children (MIS-C) requiring intensive care are described only in a small portion of infected children. Less severe lung injury in children could be explained by qualitative and quantitative differences in age-related immune response. Evidence on the best therapeutic approach for COVID-19 lung disease in children is lacking. Currently, the approach is mainly conservative and based on supportive therapy. However, in hospitalized children with critical illness and worsening lung function, antiviral therapy with remdesivir and immunomodulant treatment could be considered the “therapeutic pillars.”

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The novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection has milder presentation in children than adults, mostly requiring only supportive therapy. The immunopathogenic course of COVID-19 can be divided in two distinct but overlapping phases: the first triggered by the virus itself and the second one by the host immune response. Cytokine storm induces Acute Respiratory Distress Syndrome (ARDS) in 20-30% of adults while less than 1% of children develops severe pulmonary or systemic involvement as Multisystem Inflammatory Syndrome in Children (MIS-C), requiring intensive care. Less severe lung injury in children could be explained by qualitative and quantitative differences in age-related immune response. Evidence on the best therapeutic approach for COVID-19 lung disease in children is lacking. Currently, the approach is mainly conservative and based on supportive therapy. However, in hospitalized children with critical illness and worsening lung function, antiviral therapy with remdesivir and immunomodulant treatment with systemic steroids could be considered the “therapeutic pillars”. In addition, optimal disease control of allergic and asthmatic children and, in the near future, vaccinations are expected to be important as preventive strategies to reduce the COVID-19 burden.