Antimicrobial Agents Flashcards
antibiotic
chemical produced by one microbe and has the ability to harm other microbes
antimicrobial drug
any agent, natural or synthetic, that has the ability to kill or suppress microorganisms
bacteriocidal
directly lethal to bacteria at clinically achievable concentrations
bacteriostatic drugs
slow bacterial growth but do not cause cell death
Selective toxicity
ability of a drug to injure a target cell or target organism without injuring other cells or organisms that are in the intimate contact with the target
narrow-spectrum antibiotics
active against only a few species of microorganisms
broad-spectrum antibiotics
active against a wide variety of microbes
Four basic mechanisms for drug resistance from microbes
- decrease concentration of a drug at its site location.
- alter the structure of drug target molecules.
- produce a drug antagonist.
- cause drug inactivation.
causes random changes in a microbe’s DNA
spontaneous mutations
process by which extrachromosomal DNA is transferred from one bacterium to another.
conjugation
R factor (resistance factor)
- code for mechanism of drug resistance.
- cod for sexual apparatus for DNA transfer.
Conjugation takes place in primarily what bacteria?
Gram-negative
multiple drug resistance
transferring DNA that codes for several different drug-metabolizing enzymes to a single bacterium
which antibiotic agents promore the emergence of resistance
broad-spectrum agents
Superinfection
new infection that appears during the course of treatment for a primary infection, ridding inhibitory nature of normal flora, allowing infectious agent to flourish
superinfections are more likely in which type of patients
those receiving broad-spectrum agents
therapeutic objective when treating an infection
produce maximal antimicrobial effects, while causing minimal harm to the host
factors considered when prescribing a new antibiotic
- identity of the infecting organism.
- drug sensitivity of the infecting organism.
- host factors, site of the infection and the status of host defenses.
why will one drug of first choice be chosen over another one
greater efficacy, lower toxicity, more narrow spectrum
conditions ruling out first choice drug of choice
- allergies to drug.
- inability of drug of choice to penetrate to the side of infection.
- heightened susceptibility of the patient to toxicity of the first-choice drug.
two host factors that influence the selection of antibiotics
host defense and infection site.
Also: age, pregnancy, previous drug reactions.
host defenses
primarily of the immune system and phagocytic cells - antimicrobial therapy would be rare without it (concert).
minimum inhibitory concentration (MIC)
amount of bacteriocide at the site of infection
Antimicrobial concerns in infants
vulnerable to drug toxicity. Eliminate drugs slowly. No sulfonamides, kernicterus.