The Changing Landscape of Molecular Epidemiology of Staphylococcus Aureus Infections in Children.

Abstract

\n Background: Staphylococcus aureus infections cause significant morbidity and mortality in children and adolescents. Aim of this study was to investigate the molecular epidemiology and antibiotic resistance of Staphylococcus aureus clinical isolates from children and adolescents.Methods: All S. aureus isolates recovered from patients aged < 18 years, admitted to a referral hospital, with culture-proven invasive or non-invasive, community-associated or community-onset healthcare-associated or hospital-associated infections during the 4-year period from January 2015 to December 2018 were analyzed for antimicrobial resistance, virulence genes, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).Results: Among 139 S. aureus clinical isolates, 16 (11.5%) were methicillin-resistant (MRSA) and 123 (88.5%) methicillin-susceptible (MSSA). MSSA infections increased significantly over time (2017-2018 vs. 2015-2016, 0R 3.32; 95%CI 1.18-8.96; p 0.03) along with increasing resistance to fusidic acid (OR 2.38; 95%CI 1.14-5.12; p 0.02) and in staphylococcal scalded skin syndrome prevalence (OR 3.24; 95% CI 1.10-8.36; p 0.03). A total of five sequence types (ST) were identified among 58 isolates that were analyzed by MLST. By PFGE typing, 22 pulsotypes were identified, whereas, PFGE type 1 classified as ST121 clone was the predominant (40/58,68.9%). MRSA were distributed into four pulsotypes and PFGE type C- ST80 was the most frequent. ST121 strains carried fnbA (40/40), eta/etb genes (29/40) and lukF/S-PVL genes in 3/40 cases. All ST121 exhibited high resistance percentage to fusidic acid and were increasingly resistant to mupirocin. Conclusion: In our population, a CA-MSSA clone emerged, resistant to fusidic acid and increasingly resistant to mupirocin which belonged to the PFGE type 1, ST121 clone, harbored exfoliative toxins genes and was associated with rising trends of SSSS.