Antibiotic therapy for severe bacterial infections: correlation between the inhibitory quotient and outcome

• Published in: International journal of antimicrobial agents Vol. 23; no. 2; pp. 120 - 128
• Main Authors: Spanu, Teresa, Santangelo, Rosaria, Andreotti, Felicita, Cascio, Giuliana Lo, Velardi, Giuseppe, Fadda, Giovanni
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 01.02.2004; Amsterdam Elsevier; New York, NY
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Anti-Bacterial Agents - administration & dosage; Anti-Bacterial Agents - pharmacokinetics; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antimicrobial therapy; Bacteria - drug effects; Bacterial Infections - drug therapy; Bacterial Infections - physiopathology; Biological and medical sciences; Female; Humans; Inhibitory quotient; Male; Medical sciences; Microbial Sensitivity Tests; Middle Aged; Pharmacology. Drug treatments; Therapeutic outcome; Treatment Outcome; Inhibitory quotient; Antimicrobial therapy; Therapeutic outcome; Correlation; Prognosis; Critically ill; In vitro; Antimicrobial agent; Infection; Antibiotic; Chemotherapy; Sensitivity resistance; Treatment; Minimum inhibitory concentration; Bacteriosis; Antibacterial agent; Severe
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2003.06.006

In severe bacterial infections, treatment failure can occur even when the infecting organism has displayed in vitro susceptibility to the antibiotics used. Several pharmacokinetic–pharmacodynamic parameters show better correlation with therapeutic outcome than susceptibility results. This study was devised to assess the relation between the inhibitory quotient (IQ), i.e., the ratio of achievable antibiotic concentration at the infection site to the minimum inhibitory concentration for the infecting organism, and both clinical and bacteriological outcomes in 290 severe bacterial infections. Multivariate analysis showed that the IQ was a strong predictor of therapeutic outcome ( P<0.001–0.002): values <4 predicted failure, and those ≥6 cure. This simple parameter could be routinely used to guide effective antibiotic therapy.