Week 19 Flashcards
inhibition of bacterial growth (94 cards)
1
Q
What are some reasons for controlling bacterial growth?
A
Biofouling
Lab culture
Medical equipment
Water treatment
Food spoilage
In vivo treatments
2
Q
Define sterization
A
Process of removing all present microorganisms
3
Q
Define disinfection
A
Sterilizing a surface
4
Q
Define disinfectant
A
Antimicrobial on a non living surface
5
Q
Define antiseptic
A
anitmicrobial on linivg surface
6
Q
Define pasteurization
A
High temperature treatment to kill most microorganisms
7
Q
Describe the conditions of High temp short time pasteurization
A
72 degrees, 15s
8
Q
Describe the conditions of Ultra High temp short time pasteurization
A
138 degrees, 2s
9
Q
Give some examples of spoilage organisms
A
Lactococcus spp.
Lactobacillus spp.
Pseudonomonas
Proteus
Streptococcus
10
Q
What are mesophiles?
A
Organism grown best at 37 degrees
11
Q
What happens to protein stability at heat?
A
Post optimal temp cuases hydrophobic forces and hydrogen bonds to break
So proteins denature
12
Q
At what temperature are mesophiles killed?
A
55 degrees
13
Q
What kind of heat conditions are best at killing bacteria?
A
Moist heat (latent heat release)
Post evacuation
14
Q
What was Gruinard island infected by?
A
Anthrax
15
Q
Describe the properties of endospores
A
THermostable
Dehydrates
Resilient
Vegetative
16
Q
Give examples of bacteria that produce endospores
A
Anthrax
Bacillus
Clostridium difficile
17
Q
What is an autoclave and what does it do?
A
Pressure vessel with steam that eliminates spore forming organisms
18
Q
What are the conditions created by an autoclave?
A
121 degrees
15 psi
15s
19
Q
What could kill these:
Anthrax
Bacillus
Clostridium difficile
A
Autoclave
20
Q
What are the pros and cons of using heat for sterilization?
A
Pros= cheap and effective
Cons= not all materials are suitable
21
Q
What sort of rays are used in irradiation?
A
UV
Xray
gamma
22
Q
How does non ionising radiation work?
A
Radiation causes adjacent bases to bind, pyrimidine dimer formation
23
Q
In what scenario would non ionising radiation be used?
A
In UV lights above hood sin labs to remove contamination overnight
24
Q
How does ionisoing raditation work?
A
Causes direct damage to phosphate backbone and nucleic acids
Reactive O2 species made
25
Where would ionising radiation be used?
Industrially
Food, medicinal products, drugs, tissue grafts
26
What elements might be used for ionising radiation?
60 Co
137 Cs
27
What are some pros and cons for radiation as a sterilising technique?
Pros= suitable for wider range of materials
COns= Expensive, variable effectriveness, public resistance
28
Which is a better sterilisng technique: gamma rays or UV?
Gamma is more penetrative than UV
29
What is Bacteriophage therapy?
Using viruses to infect and kill becteria
30
Give some pros of bacteriophage therapy?
Highly specific
Bacteriacidal
Active agianst multi drug resistance
can combine wiht antibiotics
safe
self amplifying
self limiting
31
Give some cons of bacteriophage therapy?
Highly specific
Reseistance occurs
Lack of eukaryotic cell penetration (fungal)
Formulation challenges
Risk of immune clearance/ activation
Risk of endotoxin
32
What is wound debridement?
eg. maggot therapy
MAggots only eat necrotic flesh
MAggots are bred from sterile larvae
Can be biobag or free range
33
Why might pathogens reside in necrotic flesh?
LEss blood flow means anaerobic conditions
34
What group of biohazard are our first year labs? And what organisms fit this?
2
Can cause human disease but unlikely to spread to the community. Effective treatment is available
pseudonomas aeruginosa
staph aureus
35
What group of biohazard could cause severe disease that could spread, but there sis usually treatment? And what organisms fit this?
3 Separate facility, sealed rooms and airlock. -ve pressure
MTB, Anthrax
Yersinia pestis
36
What group of biohazard causes severe diesease and no effective treatment? And what organisms fit this?
4 Decontamination shpwers and hzmat suits
Ebola
Variola
Marburg
37
What are the methods of chemical killing of bacteria?
Non specific
Membrane disruption (surfactants/ soap)
Oxidising agents (bleach)
Protein modification (alkylation, heavy metals)
38
Why can't antiseptics be too harsh?
Decontaminating a biological surface such as skin, so has to be tolerable
39
What percentage of alcohol is needed to kill bacteria?
60-85%
40
What antiseptic is used to clean a surgeon's hands post op? Describe some of its properties?
Chlorhexidine
Nonspecific
Interacts with bacterial envelope
Doesn't last very long
41
What are some other commonly used antiseptics?
Quarternary ammonium chloride
Benzalkoniumchloride
Iodine
Hydrogen peroxide
42
What are disinfectants too harsh for?
SKin
43
Why might disinfectants contain chlorine?
CHlorine alkylates surface proteins on bacteria
44
How does formaldehyde disinfect?
ALkalating agent
Attaches to proteins to stop bacteria function
45
What disinfectant is used to clean animal hooves?
HEavy metals
COpper and Hg
46
What are biocides?
More specific and toxic if ingested method of killing bacteria
Phenolic, membrane disrupting, fatty acid synthesis inhibitor
47
What are biocides are commonly found in socks and lunchboxes?
Triclosan
48
How do bacteria resist Triclosan?
Involves envelope being made smaller on the membrane
49
What kind of bacteria are chemical agents generally good at killing?
Gram -ve
50
What is the only way to kill c difficile?
bleach
51
What are chemical agents effictiveness affected by?
Envrionment
eg. pH, temp, dirt, moisture
52
Define antibiotic
Chemical produced by one living organism to kill another organism
53
What order where antibiotics made? Give a generalised list?
1930s Sulfamids
1940s Penicilin
1950s Tetracycline, eryhtromycin
200s Linezoid then Daptomycin
54
Why would we use a narrow spectrum antibiotic and why would you use broad spectrum antibiotic?
Broad= when unsure of bacteria causing infection
Narrow= these don't kill useful nacteria on skin or gut
55
What's the difference between bacteriocidial, bacteriostatic, bacterolytic?
bacteriocidial= supress growth to give immune system a chance to fight
bacteriostatic= kills bacteria (can make patient worse if it makes toxins)
bacterolytic= explodes bacteiral cells
56
What was the first beta lactam antibiotic?
How does it work?
Penicilin
Binds to trans peptidase to target bacterial cell wall
57
How does Fosfomycin work?
Inhibits MurA, then this interferes with peptidoglycan synthesis
58
How does vancomycin work?
Binds to D alanine D alanine, so stops trans peptidase from binding
59
What does Peniciln, Fosfomycin and vancomycin all have in common?
All cause bacterial lyse
60
What antibiotic cuases mistakes in translation, causing a stress response and bacterial cell suicide?
Aminoglycoside
61
What is the target of fluoroquinolones?
DNA gyrase (super coiling and de super coiling of DNA)
62
How does fluoroquinolones work?
Target DNA gyrase, breaking DNA strand, passing another strand between the strands stopping them from rejoining
63
How do anti folate drugs work?
Static antimicrobial as stops bacterial formation of folic acid
64
Give examples of anti folate drugs?
Trimethoprim (inhibits dihydrofolate reductase)
Sulfamethoxazole (inhibits dihydrofolate synthase)
65
Are radical forming drugs narrow or broad spectrum?
How do they work?
Narrow spectrum as speciifc enzymes needed
The drug gets broken down cuasing release of free radicals (H2O2) dmaages DNA
66
Give some examples of Radical forming drugs?
Metronidazole
Nitrofurnatioin
67
Why would Nitrofurantoin be chosen to treat a UTI?
No 1 (narrow spectrum, hi conc in bladder)
if glomerular filtration rate is >45ml/min
To treat women with severe or more than 3 symptoms
68
Why would Trimethoprim be chosen to treat a UTI?
If low risk of resistance, eg younger women, acute UTI, low risk cases
69
Why would Pivmecillinam be chosen to treat a UTI?
If first line unsuitable and GFR<45ml/min
70
Why would AMoxicillin be chosen to treat a UTI?
If patient is susceptible to UTIs
71
Why would Fosfomycin be chosen to treat a UTI?
If high risk of resistance
72
What are some risk factors for increased resistance in UTIs?
Care home resident
Recurrent UTI
hospitalization
unresolving symptoms
recent travel
previous UTI resistance
73
How do bacteria become resistant to antibiotics?
Intrinsic (whole species is resistant)
Acquired (mutation or gene acquired)
74
What are some gene acquisition mechanisms?
Bacteriophages (transduction)
COnjugation (plasmid passed between bacterium via protein bridge called pillus)
Transposons (plasmid to chromosomes and vice and versa)
75
Give an example of a resistant gene clustering on a multi drug resistant plasmid
Beta lactamase
Beta lactam (penicilin) resistant
76
What are some resistance mechanisms?
-change antibiotic target (eg biochemical pathway)
-Inactivation of antibiotic (degradation)
-removal of antibiotic (efflux)
-disruption of antibiotic activation
77
What antibiotics target cell wall?
Beta lactam
vancomycins
78
What antibiotics target DNA/RNA synthesis?
FLuoroquinolones and rifaamycins
79
What antibiotics target cell membrane?
daptomycin
80
What antibiotics target protein synthesis?
Linezolid
Tertacycline
81
What antibiotics are resisted through bacterial efflux?
Fluoroquinolones
tetracycline
beta lactam
82
What antibiotics are resisted through immunity bypass?
Tetracycline
trimethorpin
Sulfanomide
Vancomycin
83
What antibiotics are resisted through Target modification?
FLuoroquinolones
Rifamycin
VAncomycin
Penicilin
84
What antibiotics are resisted through inactivating enzymes?
Beta lactams
MAcrolides
Rifamycins
85
How does mutation for N.gonorrhea PBPs work?
Target modification
acquisition of new resistant genes
86
Explain target modification through gene acquistion in MRSA PBP2
Penicilin Bnding Protein is essential for cell wall synthesis (peptidoglycan cross linking)
It acquires mec A gene that codes for new PBP
PBP2 has a low affinity for beta lactam antibiotics
usually through horizontal gene transfer
87
How does Sulfamethoxazole Resistnace come about?
Target alterations in Trimethoprim
No DNA synthesis
Sulf. inhibits dihydrofolate synthase
trimeth. inhibts dihydrofolate reductase
88
What kind of bacteria are antibiotic resistant via metabolic bypass?
Gram +ve
vancomycin resistnace (glycopeptide bacteria)
89
How would bacteria inactivate penicilin?
Break down penicilin
It;s no longer to bind
no antibiotic properties anymore
90
What bacteria would efflux antibiotic via active transport?
AcrATolC (e coli)
Fluoroguinolone (icpprofloxacin)
91
What is the most common form of resistance to Nitrofurantonins?
Administered in an inactive form and activated by bacterial enzymes
Bacterial enzymes stop being produced
92
What antibiotic are often used in agriculture that promote antibiotic resistance?
Avoparcin
vancomycin
93
What gram +ve bacteria pathogens are the ones to worry about?
enterococci and MRSA (glycopeptide resistant)
94
What gram -ve bacteria pathogens are the ones to worry about?
opportunistic pathogens and health related at risk
