Phenotypic and Molecular Characteristics of Community-Associated Staphylococcus aureus Infection in Neonates

Figures & data

Table 1 Phenotypic and Molecular Characteristics of Invasive and Non-Invasive S. aureus Isolates

Characteristics	S. aureus (n=92)	Invasive Isolates (n=13)	Non-Invasive Isolates (n=79)	P value
Phenotype (resistance) ^a
penicillin	89(96.7)	13(100.0)	76(96.2)	0.999 ^c
cefoxitin	27(29.3)	9(69.2)	18(22.8)	0.001
erythromycin	37(40.2)	8(61.5)	29(36.7)	0.091
clindamycin	37(40.2)	7(53.8)	30(38.0)	0.279
tetracycline	26(28.3)	7(53.8)	19(24.1)	0.027
trimethoprim-sulfamethoxazole	8(8.7)	1(7.7)	7(8.9)	0.890
gentamicin	7(7.6)	0(0.0)	7(8.9)	0.331 ^c
rifampin	4(4.3)	2(15.4)	2(2.5)	0.094 ^c
ciprofloxacin	5(5.4)	0(0.0)	5(6.3)	0.999 ^c
chloramphenicol	1(1.1)	1(7.7)	0(0.0)	0.141 ^c
linezolid	1(1.1)	1(7.7)	0(0.0)	0.141 ^c
Immune evasion cluster genes (positive)
scn	13(14.1)	0(0.0)	13(16.5)	0.118 ^c
chp	20(21.7)	5(38.5)	15(19.0)	0.115
sak	88(95.7)	10(76.9)	78(98.7)	0.008 ^c
Enterotoxin genes (positive) ^b
sea	1(1.1)	1(7.7)	0(0.0)	0.141 ^c
seb	13(14.1)	2(15.4)	11(13.9)	0.889
sec	7(7.6)	1(7.7)	6(7.6)	0.999 ^c
sed	4(4.3)	1(7.7)	3(3.8)	0.462 ^c
seg	21(22.8)	0(0.0)	21(26.6)	0.034
seh	3(3.3)	0(0.0)	3(3.8)	0.630 ^c
sei	19(20.7)	0(0.0)	19(24.1)	0.047
sej	7(7.6)	0(0.0)	7(8.9)	0.264 ^c
sek	16(17.4)	6(46.2)	10(12.7)	0.003
sem	13(14.1)	1(7.7)	12(15.2)	0.472
sen	3(3.3)	1(7.7)	2(2.5)	0.370 ^c
seo	11(12.0)	1(7.7)	11(13.9)	0.609
sep	9(9.8)	0(0.0)	9(11.4)	0.200
seq	3(3.3)	2(15.4)	1(1.3)	0.051 ^c
seu	4(4.3)	0(0.0)	4(5.1)	0.538 ^c
Hemolysin genes (positive)
hla	90(97.8)	13(100.0)	77(97.5)	0.736 ^c
hlb	49(53.3)	8(61.5)	41(51.9)	0.519
hld	87(94.6)	12(92.3)	75(94.9)	0.542 ^c
pvl (positive)	16(17.4)	5(38.5)	11(13.9)	0.031
tsst1(positive)	24(26.1)	3(23.1)	21(26.6)	0.790
CC typing
CC59	14(15.2)	6(46.2)	8(10.1)	0.001
non-CC59	78(84.8)	7(53.8)	71(89.9)

Notes: ^aAll isolates were susceptible to vancomycin. ^bAll isolates were negative for some enterotoxin genes, including see, sel and ser. ^cEstimated by the Fisher’s exact test.

Figure 1 Clonal dendrogram and detailed molecular characteristics of 89 ST-typeable S. aureus isolates.

Abbreviations: ST, sequence type; CC, clonal complex; IEC, immune evasion cluster

Figure 2 Correspondence analysis for testing the relationship between CCs and resistance patterns (A) or the number of virulence genes (B) of S. aureus isolates.

Abbreviations: CCs, clonal complexes; MDR, multidrug-resistant.

Figure 3 Clonal dendrogram for describing the relationship between genotypes and detailed phenotype–genotype characteristics of 89 ST-typeable S. aureus isolates.

Table 2 Genotypic and Phenotypic Characteristics of 13 Invasive S. aureus Isolates

CCs	STs	MRSA	Antibiotics Resistance Pattern	Virulence Gene Profile
CC59	ST338	Yes	FOX-ERY-CLI-TET-LZD	chp-sak-sep-seb-sek-hla-hlb-hld-pvl
CC59	ST338	Yes	FOX-ERY-TET-RIF-CHL	chp-sak-hla-hlb-hld-pvl
CC59	ST338	Yes	FOX-CLI-TET	chp-sed-sek-seq-hla-hlb-hld-pvl
CC59	ST338	Yes	FOX-CLI-TET	chp-seb-sek-sen-seq hla-hlb-hld-pvl
CC59	ST338	Yes	FOX	sak-sek-hla-hlb-hld
CC59	ST537	Yes	FOX-ERY-CLI-TET	sak-hla-hlb-hld-pvl
CC45	ST617	Yes	FOX-ERY-CLI	sak-sec-sem-seo-hla-hld-tsst1
CC509	ST509	Yes	FOX-ERY-CLI-SXT-TET	sak-sek-hla-hld
CC6	ST6	Yes	FOX-ERY-CLI-TET	sak-sea-sea-hla-hlb-hld
CC188	ST188	No	Susceptible to all antibiotics	sak-hla-hld-tsst1
CC7	ST7	No	Susceptible to all antibiotics	chp-sak-sea-hla-hld-tsst1
CC1	ST1	No	Susceptible to all antibiotics	sak-sea-sek-hla-hlb-hld
NT	NT	No	TET	hla

Abbreviations: CCs, clonal complexes; STs, sequence types; MRSA, methicillin-resistant S. aureus; NT, non-typeable; FOX, cefoxitin; ERY, erythromycin; CLI, clindamycin; TET, tetracycline; SXT, trimethoprim-sulfamethoxazole; RIF, rifampin; CHL, chloramphenicol; LZD, linezolid.

Figure 4 Importance rank of phenotypic and molecular characteristics influencing invasive S. aureus isolates.

Abbreviations: FOX, cefoxitin; RIF, rifampin; TET, tetracycline; LZD, linezolid; CLI, clindamycin; ERY, erythromycin; CHL, chloramphenicol; GEN, gentamicin; CIP, ciprofloxacin; SXT, trimethoprim-sulfamethoxazole; PEN, penicillin; VAN, vancomycin.