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

Abstract

Purpose 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 (SCC mec ) 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. SCC mec- 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-SCC mec- 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 SCC mec -II, while two CA-MRSA isolates had SCC mec -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 mec -IV expressed a greater variety of virulence factors. Most S. aureus isolates belonged to CC5.

Surveillance of osteoarticular infections caused by Staphylococcus aureus in a paediatric hospital in Mexico City

“…In our study, CC5 followed by CC30 and CC8 were the main CC detected which coincides with the isolates reported in the epidemiology of S. aureus infections, in Mexico (Vazquez-Rosas et al, 2021). Also, this is consistent with other authors who point out the diversity of origins of strains causing paediatric OAIs, particularly in MSSA (Kechrid et al, 2011;Yu et al, 2020;Pimentel de Araujo et al, 2022).…”

“…According to the Network for the Research and Surveillance of Drug Resistance, the frequency of methicillin-resistant S. aureus (MRSA) in Mexico has decreased from 44.5% in 2009 to 26.2% in 2018. It was more common in respiratory (21.4%), blood (16.7%) and urine (9.1%) samples ( Garza-González et al., 2019 ); however, information about S. aureus from bone samples or joint fluid in paediatric patients is limited ( Vazquez-Rosas et al., 2021 ).…”

Antibiotic Susceptibility, Biofilm Production, and Detection of mecA Gene among Staphylococcus aureus Isolates from Different Clinical Specimens

“…Community-acquired MRSA strains often express lower levels of resistance to oxacillin and multiply faster than hospital-acquired MRSA strains with significantly shorter times which help community-acquired MRSA achieve successful colonization by enabling it to compete with the commensal bacterial flora [ 8 ]. Based on SCC mec typing, community-acquired MRSA strains are typically SCCmec IV, V, and VI, while hospital-acquired MRSA are usually SCC mec I, II, and III [ 9 ].…”

Genetic Characteristics of Multiple Copies of Tn1546-Like Elements in ermB-Positive Methicillin-Resistant Staphylococcus aureus From Mainland China

“…ST965 is a single-locus variant of ST5 that belongs to clonal complex 5 (CC5). CC5-MRSA is the most common and widespread MRSA lineage and has increasingly been isolated from China and abroad ( Chen et al, 2018 ; Perez-Montarelo et al, 2018 ; Wu et al, 2018 ; Vazquez-Rosas et al, 2021 ). Meanwhile, most VRSA isolates with typing data are categorized into the CC5 lineage, which independently acquires vanA-positive Tn1546 from enterococci ( Limbago et al, 2014 ; Challagundla et al, 2018 ).…”