Following a surge in the prevalence of chloramphenicol-resistant methicillin-resistant (MRSA) in Kuwait hospitals, this study investigated the genotypes and antibiotic resistance of the chloramphenicol-resistant isolates to ascertain whether they represented new or a resurgence of sporadic endemic clones. Fifty-four chloramphenicol-resistant MRSA isolates obtained in 2014-2015 were investigated. Antibiotic resistance was tested by disk diffusion and MIC determination. Molecular typing was performed using typing, multilocus sequence typing, and DNA microarray. Curing and transfer experiments were used to determine the genetic location of resistance determinants. All 54 isolates were resistant to chloramphenicol (MIC: 32-56 mg/L) but susceptible to florfenicol. Two chloramphenicol-resistance determinants, florfenicol exporter () and chloramphenicol acetyl transferase (), were detected. The -positive isolates belonged to CC5-ST627-VI-t688/t450/t954 ( = 45), CC5-ST5-V-t688 ( = 6), whereas the -positives isolates were CC8-ST239-III-t037/t860 ( = 3). While was carried on 3.5-4.4 kb plasmids, the location of could not be established. DNA sequencing of revealed 100% sequence similarity to a previously reported variant that confers chloramphenicol but not florfenicol resistance. The resurgence of chloramphenicol resistance was due to the introduction and spread of closely related -positive CC5-ST5-V and CC5-ST627-VI clones.
