Micro Ch 10 – Flashcards

use of a drug to prevent imminent infection of a person at risk

any chemical used in the treatment, relief, or prophylaxis of a disease

the use of chemotherapeutic drugs to control infection

all inclusive term for any antimicrobial drug, regardless of its origin

substances produced by the natural metabolic processes of some microorganisms hat can inhibit or destroy other microorganisms

drugs that are chemically modified in the laboratory after being isolated from natural sources

drugs produced by chemical reaction

antimicrobials effective against a limited array of microbial types for example a drug effective mainly against gram positive bacteria

antimicrobials effective against a wide variety of microbial types for example a drug effective against both gram positive and gram negative bacteria

1. the nature of the microorganism 2. the degree of the microorganisms susceptibility to various drugs 3. the overall medical condition of the patient

the smallest concentration (highest dilution) of drug that visibly inhibits growth

the ratio of the dose of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose

drugs should inhibit microbial cells without simultaneously damaging host tissues

the production of new cell wall components, DNA, RNA, proteins and cytoplasmic membrane

useful in treating infections caused by some penicillinase producing bacteria

antagonism

1. the nature of the microorganism causing the infection 2. the overall medical condition of patients 3. sensitivity of microorganism to various drugs

any agent used in the treatment, relief, or prophylaxis of a disease

prophylaxis

antimicrobial

antimicrobial

natural agents used only against bacterial infections

if the pathogen commonly shows resistance to the antibiotic

selective toxicity

peptidoglycan

in cardiac or urinary catheters which are impregnated prior to insertion with antibiotics to prevent colonization, cannot be done with biofilm infections of natural tissues such as prostate or middle ear

extracts from the bark of a cinchona tree, was the principal treatment for malaria for hundreds of years, but has been replaced by the synthesized quinolone, mainly chloroquine and primaquine, which have less toxicity

interfere with sterol synthesis in fungi, ketoconazole- cutaneous mycoses, vaginal and oral candidiasis, systemic mycoses

we are dealing with an infectious agent that relies upon the host cell for the vast majority of its metabolic functions

resistance (r) factors

preparations of live microorganisms that are fed to animals and humans to improve the intestinal biota

are nutrients that encourage the growth of beneficial microbes in the intestine

transfer of feces from healthy patients via colonoscopy

-cell membrane -nucleic acids -cell wall -ribosomes

penicillinase

interfere with sterol synthesis

-protein coat -RNA or DNA core

persisters

-exploiting bacteriophages to kill bacteria - mimicking molecules called defense peptides -using RNA interference strategies -targeting iron-scavenging capabilities in bacteria

1. direct damage to tissues through toxicity 2. allergic reactions 3. disruption of the balance of normal microbial biota

most common drug reaction, occurs because the drug acts as an antigen (a foreign material capable of stimulating the immune system) and stimulates an allergic response

normal colonists, or residents; microbiota, consist of harmless or beneficial bacteria, but a small number can potentially be pathogens

agar diffusion test that provides useful data on antimicrobial susceptibility

surface of a plate of special medium is spread with test bacterium, and small discs containing a remeasured amount of antimicrobial are dispensed onto the bacterial lawn, after incubation the zone of inhibition surrounding the discs is measured and compared with the standard for each drug

- the inability of the drug to diffuse into that body compartment (brain joints skin) - resistant microbes in the infection that didn't make it into the sample collected for testing - an infection caused by more than one pathogen (mixed) some of which are resistant to the drug

most important natural forms used to treat gram positive cocci, some gram negative bacteria (meningococci, syphilis, spirochetes)

narrow spectrum used to treat gram negative aerobic bacilli causing pneumonia, septicemia, and ute's; effective for those allergic to penicillin

narrow spectrum; used to combat superficial skin infections caused by streptococci and staphylococci; main ingredient in neosporin

block the attachment of tRNA on the A acceptor site and stop further protein synthesis

anaphylaxis

biota

wall

penecillin

bacitracin

ribosomes

erythromycin

protein synthesis

broad spectrum

-physicians use a "shotgun" approach to treat minor infections -purchase of antibiotics without a prescription in latin america and asia -many prescriptions are given to control upper respiratory infections typically caused by viruses

amantadine

tetrahydofolate

phenotypes

-drug resistant staphylococcal infections -intestinal infections caused by anaerobes

1930s introduction of modern drugs to control infections

administer a drug to an infected person that destroys the infective agent without harming host cells

aerobic bacteria and fungi

-bacteria in the genera Streptomycin and Bacillus -molds in the genera Penicillium and cephalosporium

specimens from the patients such as body fluids, sputum, stool

penicilline wil be prescribed

-streptococcus pneuoniae -neisseria meningitidis

-staphylococcus species -neisseria gonorrhoeae -streptococcus pneuoniae -enterococcus faecalis -aeorbic gram-negative enteric bacilli

provides data for drug selection

-more sensitive and quantitative than Kiby-bauer -antimicrobial solution is diluted serially (different concentrations) in tubes of broth

is not always correlated with the in vivo effect

highest therapeutic index

-preexisting conditions -history of allergy -underlying liver or kidney disease -infants, elderly, pregnant women -genetic or metabolic abnormalities -cost

-disrupt cell processes or structures of bacteria, fungi,or protozoa -inhibit virus replication -interfere with the function of enzymes required to synthesize -destroy structures already formed in cell -selectively toxic

-block the synthesis of the bacterial cell wall (penicillins) -human cells lack the chemical peptidoglycan and are unaffected by the drug

-drugs that act upon a structure common to both the ineffective agent and the host cell (cell membrane) -as characteristics of the infectious agent are more and more similar to the host cell, selective toxicity becomes more difficult to achieve

identifying structural and metabolic needs of a living cell and removing, disrupting, or interfering with these requirements

-inhibition of cell wall synthesis -inhibition of nucleic acid structure and function -inhibition of protein synthesis -interfere with cell membrane structure and function -inhibition of folic acid (vitamin B) synthesis for several metabolic functions in the body

narrow spectrum

-original penicillin was narrow spectrum and susceptible to microbial counterattacks -molecule has been altered and improved -later penicillins overcome the limitations of the original

(extracellular polymeric substance containing DNA, proteins, and polysaccharides) are unaffected by the same antimicrobials that work against them when they are free living

helps with penetration

is the use of antibiotic-impregnated catheters or sutures with antibiotics

-disrupting viral metabolism requires disruption of cellular metabolism

-an adaptive response in which microorganisms begin to tolerate an amount of drug that would normally be inhibitory -genetic versatility and adaptability -can be intrinsic as well as acquired

1940

1980s and 1990s

-spontaneous mutations in critical chromosomal genes -acquisition of entire new genes or sets of genes via horizontal transfer from another species

phenotypic rather than genotypic change

-can be transferred through conjugation, transformation -plasmids encoded with drug resistance are naturally present in microbes before they have been exposed to an antibiotic -sharing of resistance genes accounts fir the rapid proliferation of drug resistant species

but can use the antibiotics as fuel

can also harbor antibiotic drug resistance genes that can jump into pathogenic bacteria with which they share a space

-any large population of microbes will contain a few cells harboring resistance -drug resistant population will have a selective advantage -offspring inherit -dominant species

encourage the growth of bifidobacterium in the large intestine and discourage the growth of pathogens

experience adverse side effects

-liver -kidneys -gi tract -cardiovascular system -nervous system -respiratory tract -skin -bones and teeth

substances that develop from the metabolic alteration of the drug

microbes that were once small in number overgrow when normal resident biota are destroyed by broad spectrum antimicrobials

-uti caused by E coli -lactobacilli in the female vagina are killed by the broad spectrum cephalosporin used to treat uti -overgrowth of candida albicans occurs causing yeast infection or oral thrush

-oral therapy with tetracyclines and broad spectrum penicillins kills off normal biota of the colon -overgrowth of clostridium evades the intestinal lining and releases toxins

sulfonamides and trimethoprim

aminoglycosides

-drug resistant pseudomonas aerginosa -severe uti's

antibiotics bind to the 70S bacterial ribosomes but not to the 80S eukaryotic ribosomes

antimicrobials that inhibit cell wall synthesis

generally most effective against gram-positive bacteria

effective against penicillinase-producing bacteria

broad spectrum drug, active against gram positive bacteria and some gram negative enteric bacteria

most extended spectrum of "-cillins"

an infection that occurs due to the overgrowth of other potentially pathogenic microbes during or after initial antimicrobial therapy

azoles

-treating with quinine and its semisynthetic derivatives -increasing the dosage of penicillins and tetracyclines

-clindamycin -cephalosporin -tetracycline