Week 14 Exam 4 Flashcards
(27 cards)
Goal of Antimicrobial chemotherapy
administer a drug to an infected person that destroys the infective agent without harming the hosts cell
a drug must be able to:
- be easy to administer and able to reach the infectious agent anywhere in the body
- be toxic to the infectious agent and nontoxic to the host
- remain active in the body as long as needed and be safe and easily broken down and excreted
prophylaxis
use of a drug to prevent infection of a person at risk
antimicrobials
all-inclusive term for any antimicrobial drug
antibiotics
inhibit or destroy bacteria
semisynthetic drugs
drugs that are chemically modified in the lab
synthetic drugs
drugs produced entirely in the lab
narrow-spectrum (limited spectrum)
antimicrobials effective against a limited array f microbial types
-a drug effective mainly against gram positive bacteria
broad-spectrum (extended spectrum)
antimicrobials effective against a wide variety of microbial types
-a drug effective against both gram positive and negative bacteria
what factors must be known before antimicrobial therapy can begin?
- the identity of the microorganism causing the infection
- the degree of the microorganisms susceptibility (or sensitivity) to various drugs
- disc-diffusion test: kirby bauer & E-test
- tube-diffusion test: MIC
Disk Diffusion Test
- surface of an agar plate is spread with test bacterium
- small discs containing a prepared amount of antibiotic are placed on the plate
- zone of inhibition surrounding the discs is measured and compared with a standard for each drug
Tube dilution test
- antimircobial is diluted serially in tubes of broth
- each tube is inoculated with a small uniform sample of pure culture, incubated and examined
- minimum inhibitory concentration MIC: smallest concentration (highest dilution) of drug that visibly inhibits growth
- broad-spectrum:
- narrow-spectrum:
- broad-spectrum: effective against more than one group of bacteria
- narrow-spectrum: target a specific group
how do bacteria in biofilms behave?
- often unaffected by antimicrobials
- antibiotics often cannot penetrate the sticky extracellular material surrounding biofilms
- bacteria in biofilms express a different phenotype and have different antibiotic susceptibility profiles than free living bacteria
treating fungal infections
fungal cells are eukaryotic, present special problems in chemotherapy:
- drugs designed to act on bacteria are ineffective against fungi
- similarities between fungal and human cells mean that drugs toxic to fungi will harm human tissues
- only a few agents with special anti fungal properties have been developed
treating protozoal infections
- anti-malarial drugs
- ameobicies
treating helminth infections
- flukes, tapeworms, and roundworms are larger parasites.
- theri physiology is much more similar to humans
- blocking reproduction doesn’t effect adult worms
- most effective drugs immobilize, disintegrate, or inhibit the metabolism of all stages of the life cycle
treating viral infections
- infectious agent relies on a host cell for the vast majority of its metabolic functions
- disrupting viral metabolism requires disruption of cellular metabolism of host
- inhibition of virus entry: receptor/fusion/uncoating
- inhibition of nucleic acid synthesis
- inhibition of viral assembly/release
antimicrobial resistance:
-adaptive response in which microorganisms begin to tolerate an amount of drug that would normally be inhibitory
due to genetic versatility & adaptability of microbial populations
microbes become newly resistant to a drug after one of the following occurs:
-spontaneous mutations in critical chromosomal genes
-acquisition of entire new genes or sets of genes via horizontal transfer from another species
replacing normal flora terms;
- probiotics:
- prebiotics:
- fecal transplants:
- probiotics: preparations of live microorganisms fed to animals and humans to improve intestinal biota
- prebiotics: nutrients that encourage the growth of beneficial microbes in intestine
- fecal transplants: transfer of feces from a healthy patient via colonoscopy
drugs can adversely affect the following organs:
- liver (hepatotoxic)
- kidneys (nephrotoxic)
- GI tract
- respiratory tract
- nervous system (neurotoxic)
- skin
- bones and teeth
- cardiovascular system and blood forming tissues (hemotoxic)
Allergic reactions to antimicrobials
- drugs act as an antigen that stimulates an allergic reation
- can be provoked by the intact molecule or by metabolic alteration of the drug
- allergies have been reported for every major drug
- penicillin is most common
- sensitization occurs during the first contact with the drug
- second exposure can lead to hives, respiratory inflammation, or anaphylaxis
what should every health care professional be critically aware of?
admirable & utilitarian nature of antimicrobials and of their limitations
flu virus
- segmented RNA genome
- orthomyxoviridge
- 3 types: A, B, C
- enveloped with hemagglutinin & neuraminidase glycoproteins
