TABLE 1.
MICs of erythromycin, clindamycin, and pristinamycin IA for different S. aureus and S. fleurettii strains as determined by broth microdilution
| Strain | Origin and characteristic(s) | Reference(s) | Antibiotic resistance gene(s)a | MIC (μg/ml) for:b |
||||
|---|---|---|---|---|---|---|---|---|
| ERY | CLI | iCLI | PIA | iPIA | ||||
| S. aureus | ||||||||
| 80CR5 | Recipient strain for conjugation, plasmid free, Rifr Fusr | 26 | ≤0.5 | ≤0.5 | NAc | 4 | NA | |
| RN4220 | Recipient strain for electrotransformation, plasmid free | 27 | ≤0.5 | ≤0.5 | NA | 4 | NA | |
| RN4220/pBUS1-HCd | RN4220 with S. aureus-E. coli shuttle vector pBUS1-HC | 28 | tet(L) | ≤0.5 | ≤0.5 | NA | 4 | NA |
| RN4220/pBUS1-Pcap-HCd | RN4220 with S. aureus-E. coli shuttle vector pBUS1-Pcap-HC | 28 | tet(L) | ≤0.5 | ≤0.5 | NA | 4 | NA |
| RN4220/pBJW15 | RN4220 with erm(45) and its regulatory region cloned into pBUS1-HC | This study | tet(L), erm(45) | 32 | ≤0.5 | 256 | 4 | 8 |
| RN4220/pBJW16 | RN4220 with erm(45) cloned into pBUS1-Pcap-HC | This study | tet(L), erm(45) | >256 | >256 | >256 | 64 | 64 |
| S. fleurettii | ||||||||
| JW205 | Bovine milk | 3, this study | erm(45), mecA, tet(K) | 16 | 1 | 64 | 4 | 8 |
| JW404 | Bovine mastitis milk | 3, this study | mecA | ≤0.5 | ≤0.5 | NA | 2 | NA |
a
Antibiotic resistance genes and functions: tet(L) and tet(K), tetracycline efflux genes; mecA, penicillin binding protein 2A gene; erm(45), 23S rRNA methylase gene.
b
ERY, erythromycin; CLI, clindamycin; PIA, pristinamycin IA; iCLI and iPIA, 2 μg/ml erythromycin added to the broth for the detection of inducible resistance to clindamycin (iCLI) and pristinamycin IA (iPIA).
c
NA, not applicable.
d
pBUS1-HC is a promoterless cloning vector and pBUS1-Pcap-HC is an expression vector that harbors the strong cap 1A promoter of the S. aureus type 1 capsular polysaccharide biosynthesis gene cluster.