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. 2019 Jun 20;87(7):e00194-19. doi: 10.1128/IAI.00194-19

TABLE 4.

Growth of S. aureus on LB agar supplemented with 0.08% (wt/vol) Congo red

S. aureusa CFUb of bacteria on LB plate at indicated dilution
 CFUb of bacteria on LB + Congo red plate at indicated dilution
10 102 103 104 105 106 10 102 103 104 105 106
RN6390 25 200 TNTC TNTC TNTC TNTC 0 0 0 20 150 TNTC
QT7 20 195 TNTC TNTC TNTC TNTC 0 0 0 0 1 9
RN6390(pLI50) 20 220 TNTC TNTC TNTC TNTC 0 0 0 12 130 TNTC
RN6390(pLI50-tet38) 22 220 TNTC TNTC TNTC TNTC 0 2 13 110 210 TNTC
QT7(pLI50) 22 190 TNTC TNTC TNTC TNTC 0 0 0 0 2 7
QT7(pLI50-tet38) 20 200 TNTC TNTC TNTC TNTC 0 1 10 100 195 TNTC
a

All strains harboring plasmid pLI50 were grown in the presence of chloramphenicol (20 μg/ml) and at 37°C. QT7, tet38 mutant.

b

All values represent the means from three independent experiments. Statistical differences between S. aureus strains on Congo red plates are significant (shown in bold) and were determined by the Student’s t test (P < 0.05). TNTC, too numerous to count. The starting CFU for all strains is 106/μl of bacteria.