The Risk of Emerging Resistance to Trimethoprim/Sulfamethoxazole in Staphylococcus aureus

Figures & data

Figure 1 Experimental design. Allow indicated days of incubation with or without trimethoprim/sulfamethoxazole.

Table 1 MIC and DfrB Mutation Point in 18 Isolates of Trimethoprim/Sulfamethoxazole-Resistant S. aureus

Strain	MIC (μg/mL) of SXT				Mutation Point of DfrB
	Day 0	Day 14	Day 28	Day 35	Day 14	Day 28	Day 35
MS-8	0.063	16	4	16	F98Y	F98Y	F98Y
MS-15	0.125	8	4	8	F98Y	F98Y	F98Y
MS-17	0.125	8	4	8	F98Y	F98Y	F98Y
MS18	0.125	16	4	16	F98Y	F98Y	F98Y
MS-19	0.125	8	4	8	F98Y	F98Y	F98Y
MR-9	0.063	32	8	32	F98Y	F98Y	F98Y
MR-10	0.125	4	4	4	F98Y	F98Y	F98Y
MR-11	0.063	16	4	16	F98Y	F98Y	F98Y
MR-14	0.063	8	4	8	F98Y	F98Y	F98Y
MR-17	0.125	4	4	4	F98Y	F98Y	F98Y
MR-18	0.125	8	4	8	F98Y	F98Y	F98Y
MS-3	0.063	4	2	4	F92L	-	F92L
MS-4	0.063	4	2	4	T96I	-	T96I
MS-7	0.125	4	1	4	L141P	-	L141P
MS-9	0.063	16	1	16	T96I, F98L	-	T96I, F98L
MR-2	0.125	8	2	8	L40I	-	L40I
MR-8	0.063	4	2	4	H149R	-	H149R
MR-12	0.063	4	2	4	H149R	-	H149R

Abbreviations: SXT, trimethoprim/sulfamethoxazole; MS, methicillin-susceptible; MR, methicillin-resistant.

Figure 2 MIC values of trimethoprim/sulfamethoxazole and accumulative percentage of resistant Staphylococcus aureus strain. The left vertical axis indicates MIC of trimethoprim/sulfamethoxazole. The dot pattern box indicates the MIC range (n=40), the open triangle indicates MIC₅₀, and the open circle indicates MIC₉₀ by the day. The right vertical axis indicates the cumulative resistance rate (solid line and open square).

Figure 3 The comparison of the growth curve of Staphylococcus aureus strains. The vertical axis indicates the bacterial counts (log₁₀CFU/mL) of parental strains that have acquired resistance (n=18) (open square) and parental strains that have not acquired resistance (n=22) (closed circle). *P <0.05.

Figure 4 The change of the growth curve with the acquisition of SXT-resistance. The growth curve of Staphylococcus aureus strains that sustained resistance (n=11) (A) or that returned to susceptible (n=7) (B). The vertical axis indicates the optical density of wild type strains (WTs; closed square) and DfrB mutants (open circle). *P <0.05.