Molecular Characterization of Obtained from Blood Cultures of Paediatric Patients Treated in a Tertiary Care Hospital in Mexico.

PURPOSE

is one of the main causative agents of hospital-acquired (HA) infections. In Mexico, information about the characteristics of clinical isolates is limited. Our aim was to characterize strains obtained from blood cultures of paediatric patients treated in a tertiary care hospital.

MATERIALS AND METHODS

We analysed 249 isolates over the period from 2006 to 2019, and their resistance profiles were determined. The isolates were classified into methicillin-resistant (MRSA) or methicillin-sensitive (MSSA). Staphylococcal cassettes chromosome (SCC) were detected. Virulence genes ( and ) were amplified, and their clonal relationships were established by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and clonal complex (CC) typing. We reviewed one hundred medical files to collect clinical information.

RESULTS

Thirty-eight percent of the isolates were MRSA and showed an expanded profile of resistance to other non-beta-lactam antibiotics, while MSSA strains presented a reduced resistance profile. SCCII was the most frequent element (86.3%). Eight virulence factors were detected in MSSA and six in MRSA. The gene was detected in four MRSA-SCCIV isolates (≤0.0001). MRSA isolates were distributed among 14 clones and were classified into 15 sequence types (ST); the most frequent was ST1011 (17%). The most common CC in MRSA was CC5 (69%, ≤0.0001), and in MSSA, it was CC30 (30%, ≤0.0001). Eighty-seven percent of MRSA isolates were HA-MRSA, and 13% were community-acquired MRSA (CA-MRSA). Of 21 HA-MRSA isolates, 17 had SCC-II, while two CA-MRSA isolates had SCC-IV. Of MSSA isolates, 77% were derived from HA infections and 23% from CA infections.

CONCLUSION

MSSA isolates had more virulence factors. MRSA isolates were resistant to more non-beta-lactam antibiotics, and those with SCC-IV expressed a greater variety of virulence factors. Most isolates belonged to CC5.