ABSTRACT
Objectives:
To study the molecular characteristics,
virulence gene and resistance profiles of
Staphylococcus aureus ( S. aureus, SA) isolates from
bloodstream infections (BSI), so as to further understand the molecular characteristics of S. aureus in pediatric
patients.
Methods:
A total of 53 S. aureus
strains in
bloodstream infections from Shanghai
Children′s
Hospital between 2016 and 2021 were collected. Antimicrobial susceptibility test were adopted by instrumental and disk
diffusion method. Thirty-two kinds of
virulence genes were detected by
PCR and underwent multi-locus sequence typing (MLST),
Staphylococcus protein A (spa) typing and staphylococcal
chromosome cassette (staphylococcal cassette
chromosome mec, SCCmec) typing characterizing
methicillin-resistant Staphylococcus aureus (
MRSA).
Statistical analysis was performed using χ 2 test or Fisher exact test.
Results:
MRSA isolates accounted for 50.94% of the total(27/53), with ST398-t034-SCCmecV (6/53, 11.32%) and ST59-t437-SCCmecIV (4/53, 7.55%) as the most common
MRSA clones.
Methicillin-sensitive
Staphylococcus aureus (MSSA) isolates occupied 49.06% (26/53), among which typing ST22-t309 (3/53, 5.66%) and ST7-t091/t1685 (2/53, 3.77% each) were prevalent. Of the 53
strains, all carried ≥6
virulence genes, 33
strains (62.26%) carried ≥10
virulence genes, including 18
strains of MSSA (69.23%) and 15
strains of
MRSA (55.56%). The carriage rate of pvl
gene in MSSA was higher than that of
MRSA isolates (12/26, 33.33% vs. 6/27, 22.22%), and sasX was only detected in
MRSA isolates (4/53, 7.55%). The resistant rates of BSI-SA isolates to
penicillin,
erythromycin and
clindamycin were 98.11%, 49.06% and 41.51%, respectively.
MRSA were more resistant to clinical
antimicrobial agents than MSSA.
Conclusions:
MRSA strains cover a high proportion in S. aureus
bloodstream infection of
children, with ST398-t034 and ST59-t437 being the most common
clones. The
virulence gene carrying rate for BSI-SA was high with a greater pvl
gene carrying rate in MSSA isolates while sasX was only detected in
MRSA isolates. More clinical
attention should be paid to the high resistance status and
virulence genes characteristics of BSI-SA.