Investigation of biofilm formation ability, antimicrobial resistance and the staphylococcal cassette chromosome mec patterns of methicillin resistant Staphylococcus epidermidis with different sequence types isolated from children

• The majority of isolates showed intermediate resistance to vancomycin (MIC9016 μg/ml).
• 17.5% and 22.5% of isolates had strong and intermediate biofilm respectively.
• ica operon was identified in 41.2% of methicillin resistant Staphylococcus epidermidis isolates.
• SCCmec types V, III, IV and II were detected.
• The ST580, ST581, and ST588 were detected for the first time.

This study investigated the molecular characterizations of 80 methicillin resistant Staphylococcus epidermidis (MRSE) collected during 2012–2013 in Tehran Children's Medical Center, Iran. About 90% of MRSE isolates were multi-drug resistant (MDR) and the highest resistance was observed to cotrimoxazole and they were quite sensitive to quinupristin-dalfopristin and linezolid. Though vanA gene was not detected, the majority of isolates showed intermediate resistance to vancomycin (MIC90 16 μg/ml). Resistance to mupirocin was observed in 18 isolates. Staphylococcal cassette chromosome mec (SCCmec) types V, III, IV and II were detected in 23.75%, 7.5%, 6.25% and 5% of isolates respectively, in some of which the additional parts of mec or ccr complexes were observed. In 57.5% MRSE isolates SCCmec types were not classified. 41.2% of MRSE isolates were carrying intercellular adhesion (ica) operon and 40% had strong or intermediate biofilm. The types of arginine catabolic mobile element (ACME) were limited to type I and II. Nine sequence types (STs) were seen in mupirocin resistant MRSE isolates. The common STs were ST2, ST5 and ST22 with 27.7% (5/18), 22.2% (4/18) and 16.6% (3/18) frequencies, respectively. ST23, ST54 and ST179 plus three novels STs 580, 581,588 were also observed. The majority of STs, 83.3% (15/18) belonged to clonal complex 2 (CC2). The spread of antibiotic resistance and virulence factors among MRSE species is an alarming sign in Children's Hospitals. The combination of these two issues leads to increase the chance of successfully establishing of common STs in hospital environments, and promotes the device-related infections and bacteremia.