TABLE 2.

MDCs of antimicrobial drugs that disrupt colonization resistance in vitro compared with activity spectrum and molecular class of drugs

DrugSpectrum of activityaDrug classMDC (μg/ml)b
ApramycinG−Aminocyclitol0.5
BacitracinG+, Clostridium difficileDecapeptide0.5
CarbadoxG−Quinoxalines0.125
CephalothinG−, some G+, some OblCephalosporin1.0
ClindamycinG+, many OblLincosamide1.0
DihydrostreptomycinG−, FacAminoglycoside0.5
ErythromycinG+, some G−, some OblMacrolide0.5
LincomycinG+, G−, some OblLincosamide2-16
Nalidixic acidG−, FacQuinolone1.0
NeomycinG−, FacAminoglycoside2-16
NovobiocinG+, some OblNovobiocin0.125
Penicillin GG+, some OblPenicillin0.5
StreptomycinG−, FacAminoglycoside0.125
SulfamethoxazoleG−, some G+, FacSulfonamide2-16
TetracyclineG+, G−, FacTetracycline1.0
TylosinG+Macrolide2-16
VancomycinG+, Fac, C. difficileGlycopeptide2-16
VirginiamycinG+, some OblStreptogramin1.0
  • a Antibiotic drug class and spectrum of activity data are from references 23 and 41. Abbreviations: G+, gram-positive organism; G−, gram-negative organism; Fac, facultative anaerobe; Obl, obligate anaerobe.

  • b The MDC is the drug concentration that significantly reduces the colonization resistance of Caco-2 cell invasion from Salmonella by the model intestinal flora.