Changes in molecular characteristics and antimicrobial resistance of invasive Staphylococcus aureus infection strains isolated from children in Kunming, China during the COVID-19 epidemic

Abstract

Invasive <i>Staphylococcus aureus</i> (<i>S. aureus</i>) infection is associated with high rates of mortality in children. No studies have been reported on invasive <i>S. aureus</i> infection among children in Kunming, China, and it remains unknown whether the COVID-19 epidemic has affected <i>S. aureus</i> prevalence in this region. Thus, this study investigated the changes in molecular characteristics and antimicrobial resistance of invasive <i>S. aureus</i> strains isolated from children in Kunming during 2019-2021. In total, 66 invasive <i>S. aureus</i> strains isolated from children were typed by multilocus sequence typing (MLST), <i>spa</i>, and Staphylococcal cassette chromosome mec (SCC<i>mec</i>), and antimicrobial resistance and virulence genes were analyzed. A total of 19 ST types, 31 <i>spa</i> types and 3 SCC<i>mec</i> types were identified. Thirty nine (59.09%) strains were methicillin-sensitive <i>S. aureus</i> (MSSA) and 27 (40.91%) strains were methicillin-resistant <i>S. aureus</i> (MRSA). The most common molecular type was ST22-t309 (22.73%, 15/66), followed by ST59-t437 (13.64%, 9/66). In 2019 and 2021, the dominant molecular type was ST22-t309, while in 2020, it was ST59-t437. After 2019, the dominant molecular type of MRSA changed from ST338-t437 to ST59-t437. All strains were susceptible to tigecycline, ciprofloxacin, moxifloxacin, vancomycin, quinopudine-dafoputin, linezolid, levofloxacin, and rifampicin. From 2019 to 2021, the resistance to penicillin and sulfamethoxazole initially decreased and then increased, a trend that contrasted with the observed resistance to oxacillin, cefoxitin, erythromycin, clindamycin, and tetracycline. Sixteen antimicrobial resistance profiles were identified, with penicillin-tetracycline-erythromycin-clindamycin-oxacillin-cefoxitin being the most common, and the antimicrobial resistance profiles varied by year. The carrier rates of virulence genes, <i>ica</i>A, <i>ica</i>D, <i>hla</i>, <i>fnb</i>A, <i>fnb</i>B, <i>clf</i>A, <i>clf</i>B, and <i>cna</i> were 100.00%. Furthermore, <i>sak</i>, <i>pvl</i>, <i>ica</i>C, <i>ica</i>R, <i>fib</i>, <i>lip</i>, <i>hlb</i>, <i>hysA</i>, <i>sea</i>, <i>seb</i>, and <i>tsst</i>-1 had carrier rates of 96.97, 92.42, 87.88, 69.70, 84.85, 62.12, 56.06, 50, 37.87, 30.30, and 7.58%, respectively. Since COVID-19 epidemic, the annual number of invasive <i>S. aureus</i> strains isolated from children in Kunming remained stable, but the molecular characteristics and antimicrobial resistance profiles of prevalent <i>S. aureus</i> strains have changed significantly. Thus, COVID-19 prevention and control should be supplemented by surveillance of common clinical pathogens, particularly vigilance against the prevalence of multidrug-resistant and high-virulence strains.