Changes in the Antimicrobial Resistance and Bacterial Epidemiology of Moraxella catarrhalis from Pediatric Community-Acquired Pneumonia Patients During the COVID-19 Pandemic: A 5-Year Study at a Tertiary Hospital of Southwest China.

This study aimed to assess the impact of the COVID-19 pandemic on Moraxella catarrhalis infections in pediatric patients hospitalized with community-acquired pneumonia (CAP). The epidemiological features and antimicrobial resistance (AMR) patterns of M. catarrhalis were compared between the pre-pandemic period (2018-2019) and during the pandemic (2020-2022). The results revealed a marked increase in the positivity rate of M. catarrhalis in 2020 and 2021 compared with the pre-pandemic years. The median age of the patients increased significantly in 2021 and 2022, while the proportion of male patients decreased substantially from 2019 to 2021. In addition, there were notable changes in the co-infections of Haemophilus influenzae, parainfluenza virus, and respiratory syncytial virus during the COVID-19 pandemic. The AMR profile of M. catarrhalis also changed significantly, showing increased resistance to ampicillin, but decreased resistance to trimethoprim-sulfamethoxazole and ofloxacin, and a lower proportion of multidrug-resistant isolates. Notably, ampicillin resistance increased among β-lactamase-producing isolates. Before the pandemic, the number and detection rate of isolates, along with resistance to ampicillin and trimethoprim-sulfamethoxazole, were seasonally distributed, peaking in autumn and winter. However, coinciding with local COVID-19 outbreaks, these indices sharply fell in February 2020, and the number of isolates did not recover during the autumn and winter of 2022. These findings indicate that the COVID-19 pandemic has significantly altered the infection landscape of M. catarrhalis in pediatric CAP patients, as evidenced by shifts in the detection rate, demographic characteristics, respiratory co-infections, AMR profiles, and seasonal patterns.