BCIDP key terms

The lowest concentration of an antimicrobial that visibly prevents growth of a standardized bacterial inoculum under defined laboratory conditions. It is the reference value used to categorize isolates as susceptible, intermediate, or resistant.

A validated MIC or zone-diameter threshold, set by a standards body, that separates organisms likely to respond to a drug from those likely to fail. Breakpoints incorporate pharmacokinetics, resistance mechanisms, and clinical outcome data.

The lowest antimicrobial concentration that reduces the starting inoculum by at least 99.9% (a three-log kill) in vitro. It distinguishes killing activity from mere growth inhibition.

A pharmacodynamic pattern in which bacterial killing depends mainly on how long free drug concentration stays above the MIC or a multiple of it, not on peak level. Beta-lactams are the classic example.

A pharmacodynamic pattern in which the extent of bacterial killing rises as the peak free drug concentration rises relative to the MIC. Aminoglycosides and daptomycin follow this pattern.

The percentage of a dosing interval during which free drug concentration exceeds the MIC. It is the pharmacodynamic index that best predicts beta-lactam efficacy.

A pharmacodynamic index dividing total drug exposure over 24 hours by the organism's MIC. It predicts efficacy for vancomycin, fluoroquinolones, and several antifungals.

Persistent suppression of bacterial regrowth after drug concentrations fall below the MIC. Agents with a long PAE, such as aminoglycosides, tolerate wider dosing intervals.

Measuring drug concentrations in blood at defined times to individualize dosing for agents with narrow therapeutic windows or unpredictable pharmacokinetics, such as vancomycin, aminoglycosides, and voriconazole.

A calculated apparent space relating the amount of drug in the body to its plasma concentration. Large values suggest extensive tissue distribution and influence loading dose selection.

An initial larger dose given to reach a target concentration quickly rather than waiting several half-lives for accumulation. It is determined mainly by volume of distribution, not clearance.

The time required for plasma concentration to fall by half during elimination. It guides dosing interval selection and the time needed to reach steady state, typically four to five half-lives.

The volume of plasma from which drug is completely removed per unit time. It determines the maintenance dose needed to sustain a target average concentration.

Enhanced kidney elimination of drugs, often seen in critically ill or younger patients with high cardiac output, that lowers serum concentrations of renally cleared antimicrobials and risks underdosing.

A strategy giving one large daily aminoglycoside dose to exploit concentration-dependent killing and a long post-antibiotic effect while limiting renal uptake. Monitoring uses a single level to estimate exposure.

Administering a beta-lactam over an extended period, often two to four hours, to raise the fraction of the dosing interval spent above the MIC. It is favored for resistant organisms and high-MIC infections.

A structured community of microorganisms attached to a surface and encased in self-produced matrix, which reduces antibiotic penetration and metabolic activity, producing tolerance to many agents.

Loss of apparent drug potency when a much larger bacterial burden is tested, often from enzymatic destruction of drug or binding to bacterial material. It can cause clinical failure despite susceptible MICs.

A species-wide, chromosomally encoded inability of a drug to act, such as lack of a target or an impermeable outer membrane. It is predictable and not acquired through selection pressure.

Resistance that develops in a previously susceptible strain through mutation or acquisition of resistance genes via plasmids, transposons, or bacteriophages. It drives the need for local antibiograms.

An enzyme, usually plasmid-encoded, that hydrolyzes penicillins and most cephalosporins while remaining inhibited by clavulanate. It typically spares carbapenems, which become drugs of choice.

A beta-lactamase capable of breaking down carbapenems, often leaving few treatment options. Examples include KPC, NDM, OXA-48, and VIM enzymes, each with different inhibitor susceptibility.

A cephalosporinase, often chromosomally encoded in Enterobacterales and Pseudomonas, that is inducible and can derepress during therapy, causing resistance to third-generation cephalosporins.

A membrane transporter that actively expels antimicrobials from the cell, lowering intracellular concentration. Overexpression produces multidrug resistance in gram-negative and gram-positive pathogens.

A periodic summary of the percentage of local isolates susceptible to each tested antimicrobial. It guides empiric therapy and stewardship interventions.

A coordinated set of interventions, such as prospective audit and feedback, formulary restriction, and de-escalation, designed to improve antimicrobial use, outcomes, and resistance containment.

Narrowing empiric antimicrobial therapy once culture and susceptibility results are known, reducing spectrum, duration, or number of agents without compromising efficacy.

A structured pause, often at 48 to 72 hours, to reassess whether empiric antibiotics remain indicated, can be narrowed, or should be stopped based on new data.

Cleaning hands with alcohol-based rub or soap and water at defined moments to interrupt transmission of pathogens. It is the single most effective infection prevention measure.

Use of gloves and gown plus dedicated equipment when entering the room of a patient colonized or infected with a transmissible organism, such as MRSA or C. difficile.

A microorganism resistant to at least one agent in three or more antimicrobial classes, limiting therapeutic options and requiring infection control measures to prevent spread.

A primary bloodstream infection in a patient with a central venous catheter that is not attributable to another source. Prevention relies on insertion bundles and daily line necessity review.

A stewardship activity in which trained reviewers examine active antimicrobial orders and give prescriber-specific recommendations to optimize drug, dose, duration, or need. It is a core program strategy.

Kidney injury caused by a drug, often through tubular damage or reduced renal blood flow. Vancomycin, aminoglycosides, and amphotericin B are common culprits requiring monitoring.

Adjusting renally cleared antimicrobial doses for a sudden drop in kidney function, typically by extending the interval or reducing the dose, with reassessment as function changes.

Lengthening of the heart rate-corrected QT interval on electrocardiogram, raising torsades de pointes risk. Fluoroquinolones, macrolides, and azoles are implicated, especially in combination.

A change in a drug's effect caused by another agent, through altered metabolism, absorption, or additive toxicity. Azole and rifamycin interactions are frequent stewardship concerns.

Diarrheal illness caused by toxin-producing C. difficile, usually after antibiotic exposure disrupts normal flora. Diagnosis requires testing plus compatible symptoms, and treatment depends on severity.

A blood biomarker that rises in bacterial infection and falls with recovery. It can support antibiotic initiation and stopping decisions but must be interpreted with clinical context.