The microbiological characteristics of Staphylococcus aureus isolated from patients with native valve infective endocarditis

Figures & data

Figure 1. Flow of case selection.

† Matching criteria were i) central-line-associated bloodstream infection, ii) community-onset infection, iii) methicillin susceptibility, and iv) primary site of infection.

Note. IE, infective endocarditis.

Table 1. Baseline characteristics and demographics of matched* cases with Staphylococcus aureus bacteremia.

Variables	Native valve Endocarditis group (n = 37)	Non-endocarditis group (n = 37)
Methicillin-resistant S. aureus	17 (45.9%)	17 (45.9%)
Community-acquired infection	9 (24.3%)	9 (24.3%)
Cardiac prosthesis	0	0
SOFA score ≥ 6	18 (48.6%)	10 (27.0%)
Prolonged bacteremia	13 (35.1%)	13 (35.1%)
Primary site of infection
Primary bacteremia	0	11 (29.7%)
Central line-associated infection	5 (13.5%)	5 (13.5%)
Endovascular other than endocarditis	6 (16.2%)	0
Infective endocarditis	12 (32.4%)	0
Vertebral osteomyelitis	2 (5.4%)	6 (16.2%)
Bone or joint infection other than vertebral osteomyelitis	6 (16.2%)	4 (10.8%)
Skin and soft tissue infection	3 (8.1%)	7 (18.9%)
Lung	0	1 (2.7%)
Others	3 (8.1%)	3 (8.1%)

SOFA, sequential organ failure assessment

* matching criteria: i) central line associated infection, ii) community-acquired infection, iii) methicillin susceptibility, and iv) if possible, primary site of infection.

Table 2. Distribution of virulence factor genes in Staphylococcus aureus isolates from patients with and without endocarditis.

Virulence factor gene	S. aureus from Endocarditis group (n = 37)	S. aureus from Non endocarditis group (n = 37)	P-value
clfA	37 (100%)	37 (100%)	N/A
clfB	37 (100%)	37 (100%)	N/A
fnbpA	34 (91.9%)	37 (100%)	0.240*
fnbpB	4 (10.8%)	5 (13.5%)	1.000*
sdrC	34 (91.9%)	33 (89.2%)	1.000*
sdrD	26 (70.3%)	26 (70.3%)	1.000
sdrE	31 (83.8%)	32 (86.5%)	0.844
bbp	36 (97.3%)	37 (100%)	1.000*
cna	10 (27.0%)	15 (40.5%)	0.219
ebpS	28 (75.7%)	27 (73.0%)	0.790
map	2 (5.4%)	2 (5.4%)	1.000*
sea	2 (5.4%)	8 (21.6%)	0.041
seb	1 (2.7%)	1 (2.7%)	1.000*
sec	9 (24.3%)	7 (18.9%)	0.572
sed	0	1 (2.7%)	1.000*
see	0	0	N/A
seg	26 (70.7%)	21 (56.8%)	0.227
seh	1 (2.7%)	3 (8.1%)	0.615*
sei	26 (70.3%)	21 (56.8%)	0.227
sej	0	1 (2.7%)	1.000*
tst	11 (29.7%)	10 (27.0%)	0.797
eta	1 (2.7%)	0	1.000*
etb	0	0	N/A
sarA	37 (100%)	37 (100%)	N/A

N/A, Not applicable.

* Statistical analyses were performed with Fisher’s exact test.

Table 3. Physiological properties of Staphylococcus aureus isolated from patients with or without infective endocarditis.

Physiological property	Endocarditis group (n = 37)	Non endocarditis group (n = 37)	P-value
Fibrinogen binding ratio	1.07 (± 0.33)	1.08 (± 0.26)	0.885
Fibronectin binding ratio	1.31 (± 0.42)	1.06 (± 0.31)	0.007
Internalization (×10^6 CFU/mL)	7.0 (± 9.4)	6.8 (± 7.7)	0.665

CFU, colony forming unit.

Table 4. Distribution of genetic polymorphisms in fnbpA gene of Staphylococcus aureus isolated from patients with or without endocarditis.

Amino acid change in FnbpA	S. aureus isolated from Endocarditis patients (n = 37)	S. aureus isolated from Non endocarditis patients (n = 37)	P-value
Single amino acid variation
E652D ^a	1 (2.9%)	1 (2.7%)	1.000
H782Q ^b	21 (65.6%)	20 (60.6%)	0.675
K786N/I ^b	21 (65.6%)	24 (72.7%)	0.535
H818Q ^b	15 (46.9%)	14 (42.4%)	0.718
T826N ^b	16 (50.0%)	14 (42.4%)	0.540
S839N ^b	25 (78.1%)	28 (84.8%)	0.485
V668I ^a	5 (14.3%)	4 (10.8%)	0.723
S678I ^a	10 (28.6%)	9 (24.3%)	0.683
V698I ^a	33 (94.3%)	33 (89.2%)	0.434
N750D ^b	4 (12.5%)	3 (9.1%)	0.708
P779T ^b	0	1 (4.2%)	0.462
N788D ^b	24 (75.0%)	27 (81.8%)	0.504
K797E ^b	2 (6.2%)	1 (3.0%)	0.613
H804Q ^b	29 (90.6%)	29 (87.9%)	1.000
N846S ^b	18 (56.2%)	14 (42.4%)	0.265
A5941 ^a	10 (28.6%)	9 (24.3%)	0.683
V647L ^a	9 (25.7%)	5 (13.5%)	0.191
G656D ^a	10 (28.6%)	9 (24.3%)	0.683
V662I ^a	5 (14.3%)	4 (10.8%)	0.732
H706Q ^a	5 (14.3%)	4 (10.8%)	0.732
I808L ^b	5 (16.1%)	4 (12.1%)	0.729
Combinations of single amino acid variations
E652D + H782Q + K786N	1 (3.0%)	1 (3.0%)	1.000
H782Q + K786N	16 (48.5%)	14 (42.4%)	0.621
K786N + N788D	17 (51.5%)	19 (57.6%)	0.621
H782Q + N788D	20 (60.6%)	18 (54.5%)	0.619
H782Q + K786N + N788D	14 (42.4%)	12 (36.4%)	0.614
H782Q + K786N + N788D + H818Q	5 (15.2%)	4 (12.1%)	1.000
H782Q + K786N + H818Q	7 (21.2%)	5 (15.2%)	0.751

^a Number of isolates: 35 in the endocarditis group and 37 in the without endocarditis group.

^b Number of isolates: 33 in the endocarditis group and 33 in the without endocarditis group.

Figure 2. Correlations of the (a) number of genetic polymorphisms in the fnbpA gene and physical properties and (b) fibronectin-binding ratio of 37 Staphylococcus aureus isolates from native valve infective endocarditis cases and 37 S. aureus isolates from matched non-infective endocarditis bacteremia controls.