Microbiology Flashcards
1
Q
what are the 5 types of infectious agents?
A
1, parasites
- fungi
- bacteria
- viruses
- prion proteins
2
Q
in relation to Staphylococcus aureus, what is the genus name?
A
Staphylococcus
3
Q
in relation to Staphylococcus aureus, what is the species name?
A
aureus
4
Q
what are prion proteins?
A
infectious proteins that have no DNA or RNA
5
Q
what incurable brain infection do prion proteins cause?
A
Creutzfeld-Jacobs Disease
‘Mad cow diease’
6
Q
why do surgical instruments used on patients with prion disease have do be destroyed?
A
prion proteins cannot be reliably removed by sterilisation or disinfection
7
Q
what is the another name for prion diseases?
A
transmissible spongiform encephalopathies (TSEs)
8
Q
What are viruses?
A
very small, obligate intracellular parasite
contain RNA or DNA, a protein coat +/- a lipid coat
9
Q
what are the diagnostic methods for viruses?
A
Serology
PCR
Cell culture
10
Q
what is serology?
A
antibody detection in blood
11
Q
what does PCR detect and replicate millions of times?
A
DNA or RNA
12
Q
how is DNA contained within a bacterial cell? (prokaryote)
A
within one tightly coile, double-stranded chromosome: nucleoid
plus extra circular rings of DNA in cytosol: plasmids
13
Q
what are the flagellae of a bacterial cell for?
A
tail-like structure, for movement
14
Q
what are the pili (fimbriae) of a bacterial cell for?
A
adhesion
15
Q
what shape is a coccus bacteria?
A
round
16
Q
what shape is a bacillus bacteria?
A
rod-shaped
17
Q
what shape is a spirochaetes?
A
spirals
18
Q
what does Gram stain actually stain?
A
bacterial cell wall
19
Q
what colour does the Gram stain go if the bacteria is Gram positive?
A
purple
20
Q
what colour does the Gram stain go if the bacteria is Gram negative?
A
pink
21
Q
explain the cell wall of a gram positive bacterium
A
gram positives have a thick layer of peptidoglycan (cell wall) and then just deep to that have a cytoplasmic membrane made of phosholipids.
22
Q
explain the cell wall of a gram negative bacterium
A
gram negatives have a outer cytoplasmic membrane, a middle thin layer peptidoglycan (cell wall) and an inner cytoplasmic membrane
23
Q
what 2 types of bactteria dont stain well with gram stain?
A
Mycobacterium Tuberculosis (atypical bacterium which causes TB) Treponema pallidum (a spirochaete that causes sphyilis)
24
Q
why does Mycobacterium tuberculosis not stain well with Gram stain?
A
has a waxy coat that doesn’t take up the stain
25
where are the 4 main places of normal bacterial flora?
upper respiratory tract
lower small intestine and large bowel
vagina
skin
26
what is a pathogen?
a harmful organism
27
what is a commensal?
an organism part of the normal flora
28
what is an opportunistic pathogen?
an organism that will usually only cause infection in an immunocompromised individual
29
what is a contaminant?
an organism that has got into a culture by accident
30
what is pathogenicity?
the ability of a microorganism to produce disease
31
what is virulence?
the degree of pathogenicity of an organism ie how easily can the organism cause disease
32
how do bacteria replicate?
binary fission
33
what 4 main factors do bacteria require for growth?
1. food (any organic material)
2. moisture
3. correct temperature
4. correct pH
34
for human pathogen what is generally the temperature and pH required for growth?
temperature- 37 degrees
| pH- 7.4
35
what are the 4 phase to a bacterial growth curve?
1. lag phase (BR slightly> DR)
2. log phase (BR greatly> DR)
3. stationary phase (BR = DR)
4, death phase (BR < DR)
36
what are the 3 types of atmosphere a bacterium might require for growth?
aerobic (growth in presence of oxygen, most aerobes will grow in anaerobic conditions too, just less well)
microaerophilic (growth in an atmosphere with a reduced conc of oxygen and enriched CO2 conc)
anaerobic (growth in absence of oxygen, anaerobes is a term reserves for strict anaerobes)
37
what is an exotoxin?
toxin produced inside a bacteria cell and then exported from it
38
what type of bacteria make exotoxins?
gram positive bacteria
39
what is an endotoxin?
a toxin which is part of bacterial cell wall
40
what type of bacteria make endotoxins?
gram negative bacteria
41
what are the 2 main affects of bacterial toxins?
1, cause release of cytokines from immune cells
| 2. cause damage to red and white blood cells and make blood vessels 'leaky'
42
what results from damage to RBC and WBC as well as 'leaky blood' vessel?
reduced clottting ability, reduced blood pressure resulting in sepis and septic shock
43
what type of bacteria can form spores?
Gram positive bacilli
| eg Clostridium difficile and Bacillus anthracis
44
what are spores?
inactive, tough forms of bacteria which cannot replicate but can survive adverse conditions for many years and become active when conditions become more suitable
45
what 3 steps occur in spore formation?
1. chromosome condensation
2. septum formation
3. calcium dipicolinate accumulation in the core
46
what does the core of a spore consist of?
cytoplasm plus contents
| cytoplasmic membrane
47
what surrounds the core of a spore?
exosporium
48
what type of animals is anthrax usually a disease of?
cows and sheep
49
what are the 5 main diagnostic methods for bacteria?
1. microscopy (gram film)
2. culture
3. antigen detection (eg in urine)
4. serology (antibody detection in blood
5. PCR
50
how long does microscopy take?
same day
51
how long does PCR take?
same day
52
how long does culture with sensitivity testing take?
2 days, 24 hours for organism growth, 24 hours for sensitivity
53
how long does serology take?
same day
54
how long does TB culture take?
4-12 weeks
55
what are the 2 types of fungi?
moulds
| yeast
56
how do mould spores spread?
air currents
57
how do mould hyphae spread?
invade organic tissue
58
how do yeast reproduce?
budding
59
what type of treatment is used for fugnal infections?
anti-fungals
60
what is the most common cause of mould infection in humans?
Aspergillus spp
61
what type of people does Aspergillus sp usually target?
immunocomprimised
| opportunistic
62
what is the most common cause of fungal infection in humans?
Candida spp (a type of yeast)
63
how do yeasts gram stain?
large Gram positive oval structures
64
how do moulds gram stain?
they dont
65
what are single celled parasites called?
protozoa
66
what are the 4 steilisation methods used?
1. steam under pressure (autoclaves)
2. dry heat in oven at 160 degrees for 1 hour+
3. exposure to ethylene oxoid gas
4. gamma-irradiation
67
compare sterilisation to disinfectants.
sterilisation removes 99.9% of micro-organisms
| disinfection removes pathogenic microorganisms
68
what are the 2 ways of disinfection?
hot water
| chemicals eg bleach, handwash, skin antiseptic
69
what does sp mean?
1 species of the genus
70
what does spp mean?
more than 1 species of the genus
71
what are the genus's of the gram positive cocci?
```
Streptoccci spp (and Enterococci sp)
Staphylococcus spp
```
72
what type of bacteria are Streptococcus spp and Enterococcus sp (with respects to the environment the prefer to live in)?
aerobic organisms
faculative anaerobic
(grow best aeobically but can grow anaerobically too if they need to)
73
what type of colonies do Streptococcus spp and Enterococcus sp like to grow in?
chains (strips)
74
how do you differentiate between Streptococcus spp and Enterococcus sp?
by the type of haemolysis
| this is the only bacteria where it is important for classification
75
what types of haemolysis are there?
alpha- partial haemolysis
beta- complete haemolysis
gamma- no haemolysis
76
what does alpha haemolysis mean?
partial haemolysis that is caused by enzymes that denature the haemoglobin inside red blood cells causing greenish discolourisation round the colony
77
what does beta haemolysis mean?
complete haemolysis caused by enzymes (exotosins) that lyse the red blood cells completely clearing round the colony
78
what haemolytic class of Streptococci are the most pathogenic?
beta-haemolytic
79
what haemolytic class are Enterococcus sp?
non-haemolytic
80
what type of agar needs to be used for culturing bacteria when haemolysis is important?
blood agar
81
what 2 bacterial species are the alpha-haemolytic streptococci divided into?
Streptococcus pneumoniae
| Strptococcus "viridans" (a group of different species)
82
what is the other name for Strptococcus pneumoniae?
pneumococcus
83
Describe what you would see on gram film for Streptococcus pneumoniae?
Gram positive cocci in short chains or pairs (diplococci)
84
what is the bacterium responsible for the most commonest cause of pneumonia?
Streptococcus pneumoniae
85
Describe what you would see on gram film for Streptococcus "viridans"?
Gram positive coci in chains
86
What sites are Strep. "viridans" common comensals of?
resp tract
bowel
vagina
87
What type of sites does Strep "viridans" cause infection in?
sterile site
88
What is a heart infection that can be caused by Strep "viridans"?
```
infective endocarditis
(infection of the heart valves)
```
89
what 2 groups can the beta-haemolytic Streptococcus spp be divided into?
Group A strep (Strep. pyogenes)
| Group B strep
90
What is the most pathogenic of all the Streptococci?
Strep. pyrogenes
91
what infections can Strep pyrogenes cause?
- Streptococcal sore throat
- Skin and soft tissue infections
- Puerperal sepsis
92
what is the infection caused by Streptococcal sore throat?
tonsilitis
| or scarlet fever if rash also present
93
What is the most severe skin and soft tissue infection caused by Strep. pyogenes?
necrotising fasciitis
94
what is puerperal sepsis?
a severs life-threatening infection in pregnant and recently post-natal women
95
Give 2 examples of Enterococci? (non-haemolytic streptococci)
Enterococcus faecalis
| Enterococcus faecium
96
if Enterococcus faecalis and Enterococcus faecium are both part of normal bowel flora why can they sometimes cause problems? (eg UTI)
problematic if they get into sterile site
97
what are the very-antibiotic resistant strains of E. faecium which can cause outbreaks of infections in hospital?
VRE- vancomycin resistant enterococci
98
What type of bacteria are the Staphylococci spp (with regards to the environment they like to live in?)
aerobes
| faculative anaerobes
99
how do Staph. spp colonise?
clusters
100
how do we distinguish Staph. aureus from all the other staphylococci?
coagulase test
| Staph. aureus is coagulase positive
101
what is the collective name of staphylococci which are not Staph. aureus?
coagulase negative staphylococci
102
what colour on the gram culture shows coagulation for Staph. aureus?
golden
| coagulase negative is white
103
what sites are the coagulase negative staphylococci common commensals of?
skin
104
The coagulase negative staphylococci produce a surface polysaccharide slime. What is the function of this slime.
allows them to stick to plastic and other artificial material in the body
105
what infections can coagulase negative stapylococci commonly cause?
prosthetic joint, prosthetic heart valve infection, IV catheter infection
(due to slime allowing them to stick onto artificial material in the body)
106
what bacteria causes toxic shock syndrome?
Staph. aureus
107
what toxin can some strains of Staph aureus produce that damage white blood cells?
Panton-Valentine leukocidin
108
what is the collective name of toxins which act on the gut?
enterotoxins
109
what can enterotoxins cause?
food poinsoning
110
what antibiotic are MSSA (meticillin-sensitive Staph. aureus) sensitive to?
flucloxacillin
111
what antibiotic are MRSA (meticillin-resistant Staph. aureus) resistant to?
all penicillins and all cephalosporins (+ others antibiotics)
112
what bacteria is the commonest cause of skin, soft tissue and wound infections?
Staph aureus
113
what bacteria is the commonest cause of bone and joint infection?
Staph aureus
114
What types of Staph aureus cause food poisoning?
only enterotoxin-producing
115
what is the treatment of choice for Staph. aureus infection? (MSSA)
Flucloxacillin
116
what is the term for bacteria in the bloodstream?
bacteraemia
117
where may Staph. aureus bacteraemia spread to?
heart valves, joints, kidneys, brain
118
what is a common cause of Staph aureus bacteraemia in hospital?
infected IV catheters
119
what is the name for a raised temperature (fever)?
pyrexia
120
what is the name of a shivering attack as raised temperature drops? (a sign of pyrexia)
rigor
121
despite a fever being an adaptive response to infection, what harm can it cause in young children?
febrile convulsions
122
what specific prostaglandin, which is a response to cytokines and it released from the hypothalamus, causes an increase in the body's thermal set point?
Prostaglandin E
123
what does sepsis cause?
1. leaky blood vessels- loss of fluid into issues- hypotension and tachycardia- poor tissue oxygen perfusion
2. activated clotting system- blood clotting in tiny blood vessels which uses up all the clotting factors- increased risk of haemorrhage
124
What are the 5 ways any infection can spread?
```
the 5I's
Inhalation
Ingestion
Inoculation (direct and indirect)
mother to Infant
Intercourse
```
125
what are the most frequently missed areas of hand washing?
back of the thumb
back of the fingertips
medially in between fingers
fingertips of 3/4
126
what are the 5 momends for hand hygiene?
1. before patient contact
2. before aseptic task
3. after body fluid exposure risk
4. after patient contact
5. after contact with patient surroundings
127
what are the black bags for?
domestic waste
128
what are the orange bags for?
clinical waste (no sharps)
129
what is a FFP3 mask?
filter mask- airborne precautions
130
some viruses also have a lipid envelope that surrounds their protein coat, where is this lipid envelope derived from?
derived from the membrane of the host cell that the virus grew in
131
how many subunits are needed for a protein coat of a virus with icosahedral symmetry?
3 subunits
1 for apex
1 for centre of face
1 for edges
132
what type of symmetry does the adenovirus have?
icosahedral symmetry
133
how many subunits are needed for a protein coat of a virus with helical symmetry?
1 repeated subunit
134
what main 4 infections can adenoviruses cause?
sore throats
conjunctivitis
gastroenteritis
pneumonia (v rare)
135
what 6 steps are involved in the replication cycle of a virus?
```
attachment to cell
entry into cell
uncoating of viral nucleic acid
nucleic acid and protein synthesis
assembly
release
```
136
what are the 2 ways viruses can be released from host cells?
budding (providing cell with lipid envelope)
| cell lysis
137
what does selective toxicity of antibiotics mean?
more toxic for microbe than host cell
138
what virus can have a role to play in cervical cancer?
HPV
139
what viruses can have a role to play in primary hepatocellular carcinoma?
Hep B and Hep C
140
what bacteria can have a role to play in gastric cancer?
Helicobacter pylori
141
what does latency mean?
virus that can become inactive (no replication) but then reactivate later
142
where in the body does varicella-zoster virus remain latent before reactivating? (shingles)
dorsal root ganglia
143
what 3 ways indicate recent viral infection?
detection of virus specific IgM antibodies
detection of rising titre of virus specific IgG antibodies
detection of very high titre of virus specific IgG antibodies
144
what are the genus are aerobic, Gram negative cocci?
Neisseria spp
145
how do Neisseria spp appear on gram film?
Gram negative cocci in pairs (diplococci)
146
what are the 2 important types of Neisseria?
Neisseria meningitidis
| Neisseria gonorrhoeae
147
what is Neisseria meningitidis the commonest cause of?
bacterial meningitis
148
what does Neisseria gonorrhoeae cause?
gonorrhoea
149
what is the collective name of aerobic, Gram negative, large bacilli?
coliforms
150
with respect to their environmental conditions, what type of bacteria are coliforms?
aerobes
| faculative anaerobes
151
how are coliforms differentiated?
1. biochemical reactions
| 2. antigenic structure (serotyping)
152
what 2 types of serotyping are used for Coliforms?
O antigens- cell wall
| H antigens- flagella
153
are most strains of E.coli gut commensal coliforms or gut pathogens?
gut commensal coliforms
154
are Klebsiella spp. gut commensal coliforms or gut pathogens?
gut commensal coliforms
155
are Enterobacter spp gut commensal coliforms or gut pathogens?
gut commensal coliforms
156
are Proteus spp. gut commensals or gut pathogens?
gut commensal coliforms
157
are Salmonella spp. gut commensals or gut pathogens?
gut pathogens
158
are Shigella spp. gut commensals or gut pathogens?
gut pathogens
159
what type of Escherichia coli are gut pathogens?
Verotoxin procuding Escherichia coli (VTEC)
160
what are 2 important types of verotoxin producing E. coli?
E. coli O157
| E. coli O104
161
what is the 1st line antibiotic used for treatment of infections caused by coliforms? (ie if they get into a normaly sterile site)
gentamicin
162
why does Gram negative sepsis make patients very unwell very quickly? (generally slightly worse than Gram positive sepsis)
because gram negatives can release endotoxins from the Gram negative cell walls when they die
163
what do Gram negative bacteria release from cell walls when they die which forms a ligand:receptor communication with Toll-like receptor 4? (Toll-like receptor 4 is found on the surface of macrophages)
Lipopolysaccharide
164
what 2 types bacteria are strict aerobes?
Psudomonas aeruginois
Legionella pneumophila
(both gram negative bacilli)
165
what type of bacteria is Haemophilus influenzae?
small Gram negative (cocco)bacillus aerobes
166
what 2 important organisms are microaerophilic?
```
Helicobacter pylori (Gram negative small curved bacilli)
Campylobacter spp (Gram negative spiral bacilli)
```
167
what organism causes cholera?
Vibrio cholerae
168
What 2 types of bacteria are strick anaerobes?
Clostridium spp
| Bacteroides spp
169
Describe Clostridium spp.
Gram positive anaerobic bacilli
170
What can Clostridium difficile cause?
antibiotic-associated diarrhoea
171
What can Clostridium perfringens cause?
"gas" gangrene- a severe soft tissue infection following contamination of a wound
172
What can Clostridium tetani cause?
Tetanus- a fatal paralytic illness
173
Describe Bacteroides spp.
Gram negative anaerobic bacili
174
what is the 1st line treatment for infections caused by anaerobes?
metronidazole
175
how are Mycobacteria stained?
Acid-alcohol fast bacilli
176
what are 2 spirochates bacteria that do not stain with Gram stain?
```
Treponema pallidum (causes syphilis)
Borrelia burgdorferi (Lyme disease, spread by sheep ticks)
```
177
what 2 ways does genetic variation occur in bacteria?
mutation
| gene transfer
178
what are the 3 ways of gene transfer within micro-organisms?
1. transformation
2. conjugation
2. transduction
179
What is transformation?
| a way of gene transfer
when DNA released from dead bacteria is taken up by living bacteria and incorporated into plasmids of nucleoid
180
what is conjugation?
| a way of gene transfer?
bacterial sex
| a sex pilus is produced by one bacteria through withich plasmid DNA can be transferred
181
what is transduction?
| a way of gene transfer?
when viruses infect bacteria and transfer bits of DNA from one bacterium to another
182
what are the 4 mechanisms of antibiotiv resistance?
1. production of enxymes that destroy antibiotics
2. altered antibiotic binding sites
3. alteration of cell wall porins
4. up-regulation of efflux pumps
183
what do efflux pumps do?
pump out unwanted toxins
184
which antibiotics are bacteria which produce beta-lactamase resistant to?
early penicillins (eg amoxicillin)
185
which antibiotics are bacteria which produce extended spectrum beta-lactamase resistant to?
all penicillins and cephlasporins
186
wich antibiotics are bacteria which produce carbapenemase resistant to?
all penicillns, all cephlasporins and carbapenems
187
alteration of what antibiotic binding site resulted in Staph aureus becoming resistant to flucloxacillin? (MRSA)
PBP 2
| penicillin binding protein 2
188
if an antibiotic is given PO how long will it take to reach peak serum levels?
1 hour
189
if an antibiotic is given IV how long will it take to reach peak serum levels/
15 minutes
190
what does synergy mean?
effect of combination is better than the combined effect of each drug alone
191
what are the 3 reasons antibiotics are sometimes given in combinations?
1. to cover broad range of possible infecting organisms
2. to prevent the development of resistance
3. for synergistic effect
192
which antibiotics act on the bacterial cell wall?
penicillins
cephlasporins
glycopeptides
193
what group of antibiotic do penicillin, flucloxacillin, amoxicillin, temocillin, co-amoxiclav and piperacillin belong to?
penicillins
194
what group of antibiotic does ceftriaxone belong to?
cephlasporin
195
what group of antibiotic do vancomycin and teicoplanin belong to?
glycopeptides
196
what do penicillins do to the bacterial cell wall?
inhibit cell wall synthesis by preventing cross-linking of peptidoglycan subunits
197
what are the 2 draw backs of penicillin?
1. allergies to penicillin (allergy to one means allergy to them all)
2. rapid excretion via the kidneys so frequent dosing is needed (4-6 times per day)
198
what are the 3 types of penicillin? (different routes of administration)
1. benzylpenicillin (penicillin G): IV
2. phenoxymethyl penicillin (penicillin V): oral
3. benzathine penicillin (IM)
199
what is the advantage of benzathine penicillin (IM)?
long acting
200
what is the functional group of penicillins?
beta-lactam ring
201
what type of bacteria does flucloxacillin cover? (IV, oral)
Gram positive
| useful for Staph and Strep only
202
what type of bacteria does amoxicillin cover? (IV, oral)
Gram positive and Gram negative
203
what is co-amoxiclav? (IV, oral)
amoxicillin plus clavulanic acid
204
what type of bacteria does temocillin cover?
Gram negative organisms
| useful for coliforms only
205
what does clavulanic acid do?
inhibits the action of beta-lactamase enzyme, no antibiotic properties of its own
206
are penicillins bactericidal or bacteriostatic?
bactericidal
207
are cephlasporins bactericidal or bacteriostatic?
bactericidal
208
why are cephalosporins avoided in tayside?
so broad spectrum that they affect normal bowel flora and allow over growth of C dif
209
as the generations of cephlasporins increase what happens to the spectrum of activity?
increases as well
| ie 3rd > 2nd > 1st
210
how are vancomycin and teicoplanin administered?
IV
211
what do cephlasporins do to the bacterial cell wall?
inhibit cell wall synthesis
212
are glycopeptides bactericidal or bacteriostatic?
bactericidal
213
what do glycopeptides do to the bacterial cell wall?
bind to the end of the growing pentapeptid chain, preventing cross linking and thus weakening the bacterial cell wall
214
when should you avoid use of vancomycin?
in patients with kidney failure (toxic levels will build up in the blood and cause further kidney damage)
215
what type of cell wall does the bacteria need to have for glycopeptides to be effective?
Gram positive
| therefore no Gram negative effect
216
what antibiotics inhibit protein synthesis?
macrolides
tetracyclines
aminoglycosides
217
which antibiotic group do erythromycin, clarithromycin and azithromycin belong to?
macrolides
218
which antibiotic group do tetracycline, doxycycline, minocycline belong to?
tetracyclines
219
which antibiotic group does gentamicin belong to?
aminoglycosides
220
are macrolides bactericidal or bacteriostatic?
bacteriostatic
| proteins synthesis can resume once antibiotic is removed
221
are tetracyclines bactericidal or bacteriostatic?
bacteriostatic
| protein synthesis can resume once antibiotic is removed
222
are aminoglycosides bactericidal or bacteriostatic?
bactericidal
| unlike other protein synthesis inhibitors, binding of these antibiotics to the ribosome is lethal
223
how are macrolides excreted?
via liver, biliary tract and into faeces
| not in urine
224
how must gentamicin be administered?
IV (occasionally IM)
225
what is gentamicin used for?
gram negative aerobic organisms such as coliforms and pseudomonas
226
how is gentamycin excreted?
urine
227
why do you need to monitor blood levels of gentamicin?
toxicity- causes damage to the kidneys and the vestibulocochlear cranial nerve (deafness and dizziness)
228
what antibiotics act on bacterial DNA?
metronidazole
trimethoprim
co-trimoxazole
fluoroquinolones
229
how is metronidazole administered?
oral, IV
230
how does metronidazole work?
acts by causing strand breakage of bacterial DNA
231
what is metronidazole used for?
anaerobic infections
| some protozoal
232
how is trimethoprim administered?
PO
233
how does trimethoprim work?
inhibits bacterial folic acid synthesis
234
what is co-timoxazole?
trimethoprim + sulphamethoxazole
235
what does trimethoprim work on?
Gram negative and some Gram positive bacteria
236
how is trimethoprim excreted?
via the urine
237
how do fluoroquinolones work?
by preventing supercoiling of bacterial DNA
238
are fluoroquinolones bactericidal or bacteriostatic?
bactericidal
239
why is the use of fluoroquinolones severely restricted in Tayside?
C diff risk
240
What are the 4 "C£ antibiotics highly associated with C. diff?
Cephalosporins
Co-amoxiclav
Ciprofloxacin
Clindamycin
