TABLE 1

MICs of erythromycin, clindamycin, and pristinamycin IA for different S. aureus and S. fleurettii strains as determined by broth microdilution

StrainOrigin and characteristic(s)Reference(s)Antibiotic resistance gene(s)aMIC (μg/ml) for:b
ERYCLIiCLIPIAiPIA
S. aureus
    80CR5Recipient strain for conjugation, plasmid free, Rifr Fusr26≤0.5≤0.5NAc4NA
    RN4220Recipient strain for electrotransformation, plasmid free27≤0.5≤0.5NA4NA
    RN4220/pBUS1-HCdRN4220 with S. aureus-E. coli shuttle vector pBUS1-HC28tet(L)≤0.5≤0.5NA4NA
    RN4220/pBUS1-Pcap-HCdRN4220 with S. aureus-E. coli shuttle vector pBUS1-Pcap-HC28tet(L)≤0.5≤0.5NA4NA
    RN4220/pBJW15RN4220 with erm(45) and its regulatory region cloned into pBUS1-HCThis studytet(L), erm(45)32≤0.525648
    RN4220/pBJW16RN4220 with erm(45) cloned into pBUS1-Pcap-HCThis studytet(L), erm(45)>256>256>2566464
S. fleurettii
    JW205Bovine milk3, this studyerm(45), mecA, tet(K)1616448
    JW404Bovine mastitis milk3, this studymecA≤0.5≤0.5NA2NA
  • 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.