Chapter 12 MICRO Flashcards
(117 cards)
1
Q
what does post antibiotic era mean?
A
the drugs we have are no longer effective
2
Q
what is the goal of antimicrobial chemotherapy
A
administer drug to infected person, which destroys the infective agent without harming the host’s cells
3
Q
what is the goal of the ideal drug?
A
reach infectious agent anywhere in body, be toxic to the infectious agent while not being toxic to the host, remain active in the body as long as needed yet be safely and easily broken down and excreted
4
Q
how are chemotherapeutic agents described?
A
based off their origin, range of effectiveness, and whether they are naturally produced or chemically synthesized
5
Q
antibiotics are common metabolic products of
A
bacteria and fungi, they inhibit growth of other organisms creating a less competitive environment
6
Q
Greatest number of antibiotics are derived from which bacteria?
A
streptomyces and bacillus
7
Q
Greatest number of antibiotics are derived from which molds?
A
penicillium and cephalosporium
8
Q
What is click chemistry?
A
this method takes a natural microbial product and joins it with various preselected molecules in order to create semisynthetic drugs
9
Q
Who was the first to create a new derivative from altering a parent molecule?
A
Paul Ehrlich
10
Q
Why were synthetic drugs created?
A
some natural compounds cant be obtained in limitless supply without the destruction of a habitat or an organismal population
11
Q
What must first be done before starting treatment of an antimicrobial
A
identifying the microorganism causing the problem,
12
Q
How can one identify a microorganism
A
take samples(culture or nonculture), compare the appearance with the symptoms of patient
13
Q
What types of bacteria are usually targeted when checking susceptibility?
A
staphylococcus, neisseria gonorrhoeae, streptococcus pneumoniae, enterococcus faecalis, and aerobic gramnegative enteric bacilli
14
Q
why is drug testing (susceptibility) not necessary for fungal or protozoan infections?
A
antimicrobial agents generally target all representatives of these groups
15
Q
How does in vitro susceptibility work?
A
expose a pure culture of bacterium to several different drugs and observing the effects of the drugs on growth
16
Q
what is the kirby bauer test?
A
agar diffusion test that provides useful data on antimicrobial susceptibility, zone of inhibition
17
Q
antibiogram
A
profile of antimicrobial sensitivity
18
Q
Kirby bauer test is less effective for….
A
bacteria that are anaerobic, high fastidious, or slow growing
19
Q
Etest
A
diffusion test that provides more info on drug effectiveness
20
Q
tube dilution test
A
antimicrobial is diluted serially in tubes of broth, then each tube is inoculated with small uniform sample of pure culture
incubated and examined for growth (turbidity)
21
Q
Minimum inhibitory concentration
A
the smallest concentration (highest dilution) of drug that visibly inhibits growth
useful in determining the smallest effective dosage of a drug and in providing a comparative index against other antimicrobials
22
Q
We observe the clinical patients response because
A
the in vitro effect is not always correlated with the in vivo effect
23
Q
what are the three factors before starting treatment?
A
- identify microorganism causing infection
- degree of microorganism susceptibility to various drugs
- overall medical condition of the patient
24
Q
The failure of an antimicrobial is due to
A
- the inability of the drug to diffuse into that body compartment
- resistant microbes in the infection that didnt make it into the sample collected for testing
- an infection caused by more than one pathogen, some are resistant to drug
25
what are other factors that influence choice of antimicrobial drug?
nature and spectrum of the drug, potential adverse effects, and the condition of the patient
26
Best choice to for choosing antimicrobial
the one with the fewest effect on microbes other than the on being targeted, this decreases the potential of a variety of adverse reactions
27
Therapeutic index (TI)
the ratio of the dose of the drug that is toxic to humans to its minimum effective dose
best to choose high selective toxicity for the infectious agent and low human toxicity
28
What ratio for TI is risky?
the closer the ratio is to the toxicity dose to toxicity of human over the minimum effective dose
1.1 is greater than a 10
29
The drug with the highest TI usually has
the widest margin of safety
30
Doctors also have to check what before starting treatment?
check medical history for an allergies, diseases
| also infants, elderly, and pregnant women have to take special precautions
31
what other factors are put in place when choosing antimicrobials?
what other drugs a patient is taking, genetic or metabolic abnormalities in patient, site of infection, the route of administration and cost of drug
32
the goal of antimicrobial drugs is
either to disrupt the cell processes or structures of pathogens, to inhibit their replication, or interfere with enzyme function
33
Selectively toxic
kill or inhibit microbial cells without simultaneously damaging host tissues
34
in order to disrupt the structure or function of an organism to the point of no survival, the first step is to..
identify the structural and metabolic needs of a living cell
35
The categories to of creating no survival for microorganisms is by
inhibition of cell wall synthesis
inhibition of nucleic acid structure and function
inhibition of protein synthesis
interference with cell membrane structure or function
inhibition of folic acid synthesis
36
Broad-spectrum drugs
effective against more than one group of bacteria
37
Narrow-spectrum drugs
generally target a specific group of bacteria
38
Penicillin
end in -cillin
can be synthesized in lab or obtained naturally through microbial fermentation
the natural product can be used in unmodified form or make semisynthetic derivatives
39
What are the three parts of penicillin
thiazolidine ring, a beta-lactam ring, and a variable side chain that dictates it microbicidal activity
40
What are most important natural forms of penicllin
Penicillins G and V
41
Penicillin is the drug of choice for infections by
gram positive cocci and some gram negative bacteria
42
What enzymes are capable of destroying the beta-lactam ring of penicillin?
penicillinases or beta-lactamases
| bacteria that possess them are resistant to many penicillin
43
What have scientists created to resist penicillinase producing bacteria
penicillinase resistant penicillins
| methicillin, nafcillin, and cloxacillin
44
Penicillin disrupts...
cell walls which has no effect on human cells
45
What is added to semisynthetic penicillins to augment their effectiveness
clavulanic acid
| inhibits beta-lactamase enzymes
46
Cephalosporins come from
the mold cephalosporium acremonium
47
What is the structure of cephalosporins
contain beta-lactam structure that can be synthetically altered
roots are cef, ceph, or kef
broad spectrum and resistant to most penicillinases
given orally
targets cell walls
48
Parenterally
drug inserted by injection into a muscle or vein
49
How many generations does cephalosporins have
5
50
first generation cephalosporins
most effective against gram positive cocci and a few gram negative bacteria
51
second generation cephalosporins
more effective that first in treating gram negative bacteria
52
third generation cephalosporins
broad spectrum with especially well developed against enteric bacteria that produce beta-lactamases
53
fourth generation cephalosporins
include cefpirome and cefepime
54
fifth generation cephalosporins
exhibits activity against methicillin-resistant staphylococcus aureus and also against penicillin resistant gram positive and gram negative bacteria
55
Carbapenems
powerful and dangerous drugs used by hospitals when other drugs arent working
dirsupt cell wall
56
Aztreonam
used when patient is allergic to penicillin, narrow spectrum drug, target cell wall
57
Bacitracin
narrow spectrum antibiotic produced by a strain of the bacterium bacillus subtilis
58
Neosporin is composed of
bacitracin and neomycin and polymyxin
59
Isoniazid
bactericidal to mycobacterium tuberculosis but only against growing cells
attack cell wall
combined with other drugs in tuberculosis cases
60
Vancomycin
narrow spectrum antibiotic most effective in treating staphylococcal infections when patient is allergic to penicillin
part of first generation of glycopeptides
attack cell wall
61
Aminoglycosides contain
one or more amino sugars and an aminocyclitol (6-carbon) ring
targets protein synthesis
end with suffix mycin
62
Aminoglycosides are derived from
actinomycetes in the genera streptomyces and micromonospora
63
Aminoglycosides are useful for
treating infections cause by aerobic gram negative rods and certain gram positive bacteria
64
Tetracyclines are derived from
aureomycin found from streptomyces in isolated soil
65
Function of tetracycline
binding to ribosomes and blocking protein synthesis accounts for the broad spectrum effects on gram positive and gram negative rods and cocci, aerobic and anerobic bacteria, mycoplasmas, rickettsias and spirochetes
66
Glycylcyclines
derivative of tetracycline
| bind to 30s ribosomal subunit and block the entry of the tRNA bearing an amino acid into the A site of the ribosome
67
Erythromycin
conatins macrolide ring with sugars attached, isolated from strain of streptomyces
relatively broad spectrum and of fairly low toxicity
block protein synthesis by attaching to the ribosome
68
Clindamycin
broad spectrum antibiotic derived from lincomycin
69
Ketolides
exhibit different ring structure, targets protein syntheis
| telithromycin
70
Oxazolidinones
linezolid, inhibits initiation of protein synthesis
| not found in nature so hoping resistance to drug would be slow
71
Synercid
effective against staphylococcus and enterococcus species that cause endocarditis and surgical infections
works by binding to sites on the 50s ribosome, inhibiting translation
72
Sulfonamides
synthetic and do not originate from bacteria or fungi
| inhibits folic acid synthesis
73
fluoroquinolones
high potency and broad spectrum
gram positive and gram negative bacterial species
absorbed in intestine
target RNA and DNA
74
4th generation Fluprpquinolones
effective against anaerobic organisms
75
Rifamycin
altered chemically into rifampin
cannot pass through cell envelope of many gram negative bacilli
used to treat infections y several gram positive rods and cocci and few gram negative bacteria
76
Polymyxins
bacillis ploymyxa is the source
narrow spectrum peptide antibiotics with a unique fatty acids component that contributes to their detergent activity
B and E
target cell membrane
77
Daptomycin
lipopeptide made by streptomyces
| most active against gram positive bacteria acting to disrupt multiple aspects of membrane function
78
Why are biofilms bad??
they are 1000 times less sensitive to antibiotics
79
What helps with biofilm resistance?
different phenotype expressed by biofilm bacteria
80
Ways to help against biofilms?
interrupting the quorum sensing pathways that mediate communication between cells and may change phenotypic expression
Daptomycin (lipopeptide)
Adding Dnase to antibiotic can help with penetration of the antibiotic through extracellular debris
81
why is hard to treat fungal infections
so similar to human cells
| polyene antibiotics, azoles, echinocandins and they allylamines are the four main drugs
82
Quinine
extracted from bark on a tree
| synthesized to help fight different strains of plasmodium
83
Drugs use for helminths
immobolize, disintegrate, or inhibit the metabolism of all stages of the life cycle
mebendazole and albendazole (broad spectrum)
theses drugs inhibit function of microtubules and they cannot receive glucose
84
What method is used to inhibit virus
disrupting viral metabolism by disrupting the metabolism of the host cell
have to be careful with host toxicity
85
Three modes of action for antiviral drugs
1. barring penetration of the virus into the host cell
2blocking the transcription and translation of viral molecules
3. preventing the maturation of viral particles
86
What is one downfall from antiviral drugs
unable to destroy extracellular viruses or those in a latent state
plus they virus' can become resistant very fast
87
How do antiviral drugs work
they mimic the structure of nucleotides and compete for sites on replicating DNA, inhibiting DNA synthesis
88
How do antiviral work in retroviruses
interferes with the synthesis of the new DNA strand using nucleoside reverse transcriptase inhibitors
or interfering with the action of the enzyme responsible for the synthesis using nonnucleoside reverse transcriptase inhibitors
89
Interferon
glycoprotein produced primarily by fibroblasts and leukocytes in response to various immune stimuli
90
DRACO
detects the presence of long dsRNA strands in host cells and causes the cell to self destruct
used against viruses
91
Drug resistance
an adaptive response in which microorganisms begin to tolerate an amount of drug that would ordinarily be inhibitory
92
Why are microorganisms able to become drug resistant
genetic versatility and adaptability of microbial populations
93
bacteria that produce a certain drug are
resistant to the drug they produce
94
Microbes become newly resistant to a drug after one of the following two events
1. spontaneous mutations in critical chromosomal genes
2. acquisition of entire new genes or sets of genes via horizontal transfer from another species
usually happen from the first option
95
Resistance factors
horizontal transfer of plasmids through conjugation, transformation, and transduction
plasmids are encoded with drug resistance
96
Bacteria also contain what that ar duplicated and inserted from one plasmid to another or chromosome
transposable drug resistance sequence
97
totally unrelated bacteria, viruses and other organisms living in the bodys normal biota and environment can transfer...
genes
98
What are the specific mechanisms of drug resistance
1. new enzymes are synthesized, the inactivate the drug
2. permeability or uptake of drug into bacterium is decreased
3. drug is immediately eliminated
4. binding sites for drug are decreased in number or affinity
5. an affected metabolic pathway is shut down or an alternative pathway is used
99
some bacteria can become resistant just by simply
lapsing into dormancy or by converting to a cell wall deficient form
100
Cell walls such as... can be natural blockade for some penicillin drugs
gram negative bacteria
101
What are multidrug resistant pumps
pumps in bacteria that actively transport drugs and other chemical out of cells
pumps are proteins encoded by plasmids or chromosomes
stationed in membrane, lack selectivity
102
since most drugs act on a specific target such as protein, RNA, DNA or membrane structure, microbes can get around that by
altering the nature of the target
103
if a drug is present in a habitat that microbes are growing in
some microbes will die and some will become resistant to the drug, during population growth off spring will inherit resistance
104
what type of drug do doctors usually prescribe known as shotgun antimicrobial therapy
broad spectrum drug
this led to superinfections and other adverse reactions
this also led to development of resistance in bystander microbes
105
antibiotics fed to livestock "jump" to
humans creating a resistance to certain drugs
106
what type of proposal have been made to help with long term strategies for drug resistance
restrict the use of first line antibiotics or those that are most powerful in the treatment of the most resistant microbes
107
What is a new strategy for antimicrobials
disabling host molecules that the invaders use to enhance their position
targeting a host cell protein that bacteria use to move from one cell compartment to another
108
Eastern european countries use what strategy
mixing bacteriophages as medicines for bacterial infections
| creates extreme specificity of the phage
109
Probiotics
are preparations of live microorganisms that are fed to animals and humans to improve the intestinal biota
110
Prebiotics
nutrients that encourage the growth of beneficial microbes in the intestine
111
fecal transplants
transfer of feces from healthy patients, containing beneficial normal biota, to affected patients via colonoscopy
112
what are the major side effects of drugs
1. direct damage to tissues through toxicity
2. allergic reactions
3. disruption in the balance of normal microbial biota
113
Drugs adversely affect what organs
liver, kidneys, gastrointestinal tract, cardiovascular system and blood forming tissue, nervous system, respiratory tract, skin, bones and teeth
114
how do allergies occur
drug acts as an antigen and stimulates an allergic response
response can be provoked by the intact drug molecule or by substances that develop from the bodys metabolic alteration of the drug
115
when a person is allergic to a drug how does this reaction happen
1. become sensitized to it during the first contact without symptoms
2. second exposure to drug can lead to a reaction such as skin rash, respiratory inflammation and possibly anaphylaxis
116
Biota
harmless or beneficial bacteria that are normal colonists or residents
low numbers can be pathogens
117
What happens to biota when a broad spectrum drug is introduced
kills microbes including biota
allowing other microbes that were once in small numbers can begin to overgrow and cause disease creating a superinfection
