Figure 4. Penicillin and tetracycline resistance of strains containing wild type, pilQ2, and pilQ::Ω alleles.
FA19 harboring various combinations of the penA (mutations in PBP 2), mtrR (increased expression of the MtrC-MtrD-MtrE efflux pump) and penB (mutations in porin; see Table 1 for more information) resistance determinants was transformed with plasmids encoding mutant (pilQ2) and inactivated pilQ (pilQ::Ω) alleles and the MICs of penicillin G and tetracycline for the resulting strains were determined as described in Materials and Methods. pilQ2 and pilQ::Ω were also introduced into FA6140, a chromosomally mediated penicillin-resistant clinical isolate (Danielsson et al., 1986). *P<0.01 relative to the parental strain.