Background: Methicillin-resistant Staphylococcus aureus (MRSA) belong to diverse genetic backgrounds that differ in antibiotic resistance. Knowledge of the local clonal composition of MRSA strains is important for patients' management and for designing effective control and eradication methods. The aim of this study was to compare the antibiotic resistance patterns and genotypic characteristics of MRSA isolates obtained in public hospitals in Kuwait in 2016 and 2017 for changes in their resistance patterns and clonal composition.
Methods: A total of 4726 MRSA isolates obtained in 2016-2017 from clinical specimens in Kuwait public hospitals were characterized using antibiogram, SCCmec typing, spa typing and DNA microarray.
Results: The isolates expressed resistance to fusidic acid (52.9%), kanamycin (41.6%), gentamicin (32.5%) and erythromycin (36.2%). The prevalence of high-level mupirocin resistance decreased from 3.7% in 2016 to 2.4% in 2017, while the proportion of resistance to other antibiotics remained relatively stable. A total of 382 spa types were detected with eight spa types, t688 (N = 547), t304 (N = 428), t860 (N = 394), t127 (N = 306), t044 (N = 230), t311 (N = 243), t223 (N = 184) and t002 (N = 181) constituting 53.1% of the MRSA isolates in 2016-2017. Of the 3004 MRSA isolates obtained in 2016 (N = 1327) and 2017 (N = 1677) selected for DNA microarray analysis, 26 clonal complexes (CCs) were identified. Most of the isolates belonged to CC1 (N = 248), CC5 (N = 833), CC6 (N = 241), CC8 (N = 292), CC22 (N = 421), CC30 (N = 177), CC80 (N = 177) and CC97 (N = 171). The prevalence of CC5 isolates has significantly (p ≤ 0.05) increased from 294 isolates in 2016 to 539 isolates in 2017. Although CC22 increased from 196 isolates in 2016 to 225 isolates in 2017, CC1 increased from 112 isolates in 2016 to 136 isolates in 2017, CC6 increased from 103 isolates in 2016 to 138 isolates in 2017, these changes were not significant (p ≥ 0.05).
Conclusion: These results revealed the diversity in the genetic backgrounds of MRSA isolates and the stable maintenance of the dominant MRSA clones in Kuwait hospitals in 2016 and 2017 suggesting an on-going transmission of these clones. Novel and creative infection prevention and control measures are required to curtail further transmission.
Keywords: Antibiotic resistance; Clonal complex; DNA microarray; Genotypes; MRSA.