Infection and Drug Resistance (Apr 2021)
Molecular Characterization of Staphylococcus aureus Obtained from Blood Cultures of Paediatric Patients Treated in a Tertiary Care Hospital in Mexico
Abstract
Guillermo Jose Vazquez-Rosas,1,2 Jocelin Merida-Vieyra,1 Gerardo Aparicio-Ozores,2 Antonino Lara-Hernandez,3 Agustin De Colsa,1,4 Alejandra Aquino-Andrade1 1Molecular Microbiology Laboratory, Instituto Nacional de Pediatria, Mexico City, Mexico; 2Medical Bacteriology Laboratory, Instituto Politecnico Nacional, Mexico City, Mexico; 3Bacteriology Laboratory, Instituto Nacional de Pediatria, Mexico City, Mexico; 4Department of Paediatric Infectious Diseases, Instituto Nacional de Pediatria, Mexico City, MexicoCorrespondence: Alejandra Aquino-AndradeMolecular Microbiology Laboratory, Instituto Nacional de Pediatria, Insurgentes Sur 3700-C, Col. Insurgentes Cuicuilco, Alcaldia Coyoacan, C.P. 04530, Mexico City, MexicoTel +52 55 1084-0900 Ext. 1859Email [email protected]: Staphylococcus aureus is one of the main causative agents of hospital-acquired (HA) infections. In Mexico, information about the characteristics of clinical S. aureus isolates is limited. Our aim was to characterize S. aureus strains obtained from blood cultures of paediatric patients treated in a tertiary care hospital.Materials and Methods: We analysed 249 S. aureus isolates over the period from 2006 to 2019, and their resistance profiles were determined. The isolates were classified into methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA). Staphylococcal cassettes chromosome mec (SCCmec) were detected. Virulence genes (cna, clfA, clfB, eta, etb, fnbA, fnbB, hla, pvl, sec, and tsst) 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. SCCmec-II was the most frequent element (86.3%). Eight virulence factors were detected in MSSA and six in MRSA. The pvl gene was detected in four MRSA-SCCmec-IV isolates (P≤ 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%, P≤ 0.0001), and in MSSA, it was CC30 (30%, P≤ 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 SCCmec-II, while two CA-MRSA isolates had SCCmec-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 SCCmec-IV expressed a greater variety of virulence factors. Most S. aureus isolates belonged to CC5.Keywords: MSSA, MRSA, virulence factors, clonal complex, SCCmec-II, CC5
