Infection Flashcards
1
Q
What different microorganisms can cause infection?
A
Bacteria Viruses Fungi Parasites Prions
2
Q
What are the two broad classes of sites for the collection of samples?
A
Sterile
Non-sterile
3
Q
Give examples of sterile sample sites (4)
A
Blood
CSF
Lung
Bladder
4
Q
Give examples of non-sterile sample sites (4)
A
Skin
Nasopharynx
Urethra
Gut
5
Q
What is the difference between sterile and non sterile sites and what meaning does this have clinically?
A
You would not normally find microorganisms in the sterile sites so this is usually clinically relevant.
Microorganisms can be found as part of the normal flora in non-sterile sites (eg E. coli in the gut) so identification of the infection is more difficult.
6
Q
What sample would you collect for bacterial culture for a UTI?
A
Mid-stream urine sample (MSU)
7
Q
What sample would you collect for bacterial culture for a chest infection?
A
Sputum sample
8
Q
What sample would you collect for bacterial culture for Tonsillitis/Pharyngitis?
A
Throat Swab
9
Q
What sample would you collect for bacterial culture for a wound? (2)
A
Swab
Pus
10
Q
What sample would you collect for bacterial culture for diarrhoea?
A
Stool sample
11
Q
What sample would you collect for bacterial culture for meningitis?
A
CSF
12
Q
What are the drawbacks of microscopy in microbiology?
A
Not very sensitive (magnification reduces the volume of the sample viewed)
Cannot view viruses
13
Q
What can be viewed under the microscope in an unstained sample?
A
Pus cells (eg in urine and CSF) Parasites (eg in stool sample)
14
Q
What is a gram stain used for?
A
Staining bacteria (and sometimes fungi)
15
Q
What are the drawbacks of a gram stain?
A
Not sensitive
Cannot normally identify a particular bacterial species
16
Q
What is a ZN/auramine stain used for?
A
Mycobacteria
17
Q
What are the different ways to identify different species (and strains) of microorganisms (general)?
A
Use observable characteristics
- Morphological
- Physiological
- Biochemical
Use DNA based testing
Use typing to distinguish between strains
18
Q
How would you detect and identify a viral infection?
A
Molecular testing
-PCR
Antigenic Testing
Serology to detect specific immunoglobulins and assess immunity
19
Q
Describe the differences between gram negative and gram positive organisms.
A
Gram positive
- Thick peptidoglycan layer
- No lipopolysaccharide layer
Gram Negative
- Thin peptidoglycan layer
- Lipopolysaccharide layer!
20
Q
Describe the process of gram staining
A
Specimen is heat fixed on a slide
Stained with the primary stain (crystal violet)
Gram’s iodine is added to form the crystal violet - iodine complex
Acetone or ethanol added to dissolve the lipopolysaccharide layer of Gram -ve bacteria (hence the lose colour)
Secondary stain (safranin) added - stains colourless cells pink/red.
21
Q
What colour do Gram positive bacteria appear in a Gram stain?
A
Purple
22
Q
What colour do Gram negative bacteria appear in a gram stain?
A
Red/Pink
23
Q
How do cocci appear?
A
Spherical
24
Q
How do bacilli appear?
A
Rod shaped
25
How to streptococci appear?
Chains of spherical bacteria
26
How do Staphylococci appear?
Bunch of spherical bacteria
| "Bunch of grapes"
27
What is the function of a bacteria spore?
Form in response to environmental stress and is resistant to it - allows bacteria to survive until conditions improve.
28
Which bacteria can form spores?
Gram POSITIVE only
29
What is peptidoglycan?
A polymer of disaccharides (glycan) cross linked with peptides.
A component of the cell wall of bacteria which is porous and has a high tensile strength.
30
What is lipopolysaccharide?
A polymer consisting of lipid and polysaccharide found in the cells wall of bacteria. Elicits a strong immune response in humans. Contains the lipid A molecule which is toxic to humans (and released when the bacteria is lysed by immune cells)
31
What is the function of a bacterial capsule?
Prevents phagocytosis of the bacteria and can assist with adherence.
32
What is the function of fimbrae?
Facilitate attachment to other cells
33
Describe the process of horizontal gene transfer (conjugation)
Pilus formed between two bacteria
Plasmid DNA copied to receiving bacterium by rolling circle mechanism
○ Endonuclease cleaves one strand of plasmid at the origin of transfer
○ One strand of the plasmid separates from the plasmid and a new strand is synthesised in its place (hence rolling circle)
○ Complementary strand to single strand is synthesised in recipient cell
34
What are the four causes of genetic variation in bacteria?
Spontaneous mutation
Transformation (uptake of DNA from outside the cell)
Conjugation (gene transfer from another bacterium)
Transduction (DNA incorporated from a phage in lysogenic cycle)
35
What is a fungus?
a eukaryote that lacks chlorophyll and forms spores.
36
What is a hypha?
A long branching filament of the fungus
37
What are septa (fungus)?
Internal cross walls dividing hypha into cells
38
What are conidia?
A spore produced asexually
39
What is a conidiophore?
A region bearing conidia
40
What are the characteristics of basidiomycetes?
Basidiospores formed externally on a pedestal (basidium)
41
What are the characteristics of ascomycetes?
Ascopores formed inside a sac (ascus)
42
What are the characteristics of Zygomycetes?
Haploid cells fuse to form a single zygospore
| Rough walled Zygote contains Zygospore(s)
43
What is the sexual spore of Basidiomycetes?
Basidiospore
44
What is the asexual spore of Basidiomycetes?
Conidium
45
What is the sexual spore of Ascomycetes?
Ascospore
46
What is the asexual spore of Ascomycetes?
Conidium
47
What is the sexual spore of Zygomycetes?
Zygospore
48
What is the asexual spore of Zygomycetes?
Sporangiospore
49
What are yeasts?
Fungi that favour a unicellular habitat
50
What are dermatophytes?
Moulds which prefer keratin as a nutrient source
51
What types of infections do dermatophytes cause?
Tinea (ringworm) infections
52
What is Tinea capitis?
Ringworm infection of the head
53
What is Tinea pedis
Athletes foot
54
What is Tinea cruris
Dermatophyte infection of groin
55
When are serious systemic fungal infections more likely?
In immunosuppressed patients
56
Name three iatrogenic causes of immunosuppression
Steroid therapy
Anticancer chemotherapy
Status post organ transplant
57
Name three disease processes which immunosuppress the patient
AIDs
Leukaemia
Endocrinopathies
58
What are the main species of Candida fungi? (and mention any considerations regards drug therapy)
Candida albicans
Candida tropicalis
Candida glabrata
-C. glabrata usually has resistance to -azole antifungals
59
Name human diseases which can be caused by Candida species (7)
```
Oral candidiasis
Vaginal cadidiasis
Skin infections
Nail infections
Oesophageal infections
UTIs
Disseminated infections (in very immunocomprimised pts)
```
60
Name the main Aspergillus species
Aspergillus fumigatus
| Aspergillus flavus
61
Name human diseases which can be causes by Aspergillus species (5)
Simple asthma
Asthma with eosinophilia
Aspergilloma (forms a hollow in lung tissue in which to grow)
Invasive bronchopulmonary aspergillosis
62
Name the main Cryptococcus species
Cryptococcus neoformans
| Cryptocuccus gattii
63
Name human diseases which can be caused by Cryptococcus species (3)
Pulmonary cyrptococcosis
Meningitis (particularly in AIDs pts)
Disseminated infection (in very immunocomprimised pts)
64
Describe methods for diagnosing fungal infections
Direct detection
- Histopathology
- High-res CT
- Culture using selective media (ChromAgar)
Detection of circulating fungal antigens
Detection of circulating antibodies to fungal antigens
PCR of fungal DNA
Culture of fungus from sterile site
65
What is a latent viral infection?
Virus lays dormant after initial infection and becomes active again some time later due to a stimulus (eg cold weather and HSV cold sores)
66
How can a whole virus be detected?
Microscopy (see infected cells)
| Culture (comparison of infected vs uninfected cells)
67
How can part of a virus be detected?
```
Antigen testing (same principle as pregnancy testing)
PCR of nucleic acid
```
68
How can viral infection be prevented?
Immunisation
-Vaccination
-Passive immunisation with Immunoglobulins
Prophylactic immunisation/prophylactic antivrial therapy post exposure
Infection prevention and control measures
Blood/Tissue/Organ screenning
Antenatal screening
69
What are some of the clinical signs of an infection? (7)
```
Inflammation
Pain
Pyrexia
Tachycardia
Rigors
Increased White Cell Count
Increased C Reactive Protein (CRP)
```
70
What is a pathogen?
An organism that can cause disease
71
What is a commensal?
An organism that is part of the normal flora (eg E coli in the gut)
72
What is pathogenicity?
The ability of a microorganism to cause an infection
73
What two factors contribute to overall pathogenicity?
Infectivity
| Virulence
74
What is infectivity?
The ability of a microorganism to become established
75
What is virulence?
The ability of a microorganism to cause harmful effects once established
76
Give two factors which can increase infectivity
Attachment (via fimbrae)
| Acid resistance
77
Name three virulence factors
Invasiveness (rapidly producing or not)
Toxin production
Evasion of immune system
78
What is an exotoxin?
A toxin released extracellularly
79
Give an example of an exotoxin producing organism
Clostridium tetani releases toxin which binds to nerve synapses and inhibits release of inhibitory neurotransmitters (tetanus)
80
What is an enterotoxin?
A toxin that acts in the GI tract
81
What is an endotoxin?
A toxin which is structurally part of the Gram negative cell wall
82
Name a specific endotoxin component
Lipid A molecule of the Lipopolysaccharide layer of the Gram negative cell wall.
83
Describe three viral pathogenic mechanisms
```
Cell destruction following viral infection (eg Death of CD4+ T cells by HIV)
Virus-induced changes to cellular gene expression (cellular transformation by tumour viruses)
Immunopathogenic disease (Influenza A, Coxsackievirus-induced myocarditis)
```
84
What is an acute viral infection?
Virus infects host and multiply to cause symptoms. Infection is then cleared from the body.
85
What is a latent viral infection?
Host infected acutely and lies dormant in the lysogenic cycle after initial infection with no symptoms in host. Due to some stimulus the virus is reactivated some time later.
86
What is a chronic viral infection?
After initial infection virus achieves steady state patient is symptomatic long term
87
What is antigenic drift in viruses?
The gradual evolution of viruses to generate antigenic variants
88
What is antigenic shift in viruses?
The sudden significant changes in virus antigenic structure
89
Why is antigenic shift concerning?
There is a much lower change of a person having immunity to a virus which has undergone antigenic shift. This leads to the possibility of a pandemic.
90
What are enteroviruses?
Viruses which pass through the GI tract
91
What kind of symptoms can enteroviruses present with?
```
A variety (respiratory, neurological, etc)
NB: do not necessarily present with GI symptoms!
```
92
What is innate immunity?
Non-specific immunity
93
What is active immunity?
Body mounts its own immune response to a foreign antigen
94
What is passive immunity?
Body does not mount its own immune response to foreign antigens. Antibodies are given passively.
95
What is natural active immunity?
Body mounts immune response to a pathogen it is seeing for the first time and then has immunity to it conferred by memory cells.
96
What is artificial active immunity?
Immune response to a vaccine which gives immunity to the real pathogen
97
What is passive natural immunity?
Antibodies passed to infant from mother (eg via breast milk)
98
What is artificial passive immunity?
Immunisation of antibodies given (eg Rabies immunisation)
99
What are the advantages of passive immunity?
Gives immediate protection
100
What are the disadvantages of passive immunity?
Short term effect (no immunological memory)
| Serum sickness may occur - incoming antibody is recognised as foreign by recipient resulting in anaphylaxis
101
What is a live attenuated vaccine?
A live pathogen that has been repeatedly cultured in a non-human host and has become adapted to the foreign host and has lost its virulence to humans.
102
What are the advantages of live attenuated vaccines?
They elicit strong cellular and antibody responses and often confer lifelong immunity
103
What are the disadvantages of live attenuated vaccines?
Remote possibility that the attenuated pathogen could revert to a virulent form and cause disease.
Needs to be refridgerated
104
What is an inactivated vaccine?
A vaccine produced by killing the pathogen with: chemicals (formaldehyde), heat, or radiation.
105
What are the advantages of inactivated vaccines?
More stable and safer than live vaccines
| Usually don't require refridgeration - can be freeze-dried hence more accessible to developing countries.
106
What are the disadvantages of inactivated vaccines?
Stimulate a weaker immune response than live attenuated vaccines.
Usually require several boosters to maintain immunity.
107
What is an acellular vaccine?
A vaccine which uses only the antigenic part of the pathogen
108
What is the main advantage of acellular vaccines?
Cannot cause disease so safe in immunocomprimised patients
109
What is a toxoid vaccine?
A vaccine made with inactivated toxin.
110
How are toxoid vaccines made?
Toxin is inactivated by treatment with formalin.
111
What is a conjugate vaccine?
A vaccine which links polysaccharides which are difficult for the immune system to recognised to strong antigens which elicit a stronger immune response. This allows the immune system to respond to the polysaccharide.
112
What is a parasite?
An organism that lives in another organism (host) and gets its food at the expense of the host.
113
Give three examples of protozoa
Malaria
Amoebae
Flagellates
114
Give three examples of helminths
Roundworms (Nematodes)
Flatworms (Platyhelminths)
Flukes
115
Give three examples of arthropods
Lice
Ticks
Mites
116
How are protozoa that live in the human intestine transmitted?
Via the faecal-oral route
117
How are protozoa living in human blood or tissue transmitted?
Via an arthropod vector
118
What is Malaria?
A mosquito-borne disease caused by the parasitic Plasmodium species.
119
How does malaria present?
Flu like symptoms
120
Which Plasmodium species causes the highest mortality from Malaria?
Plasmodium falciparum
121
What is the vector for Malaria?
The female Anopheles mosquito
122
Describe the life cycle of Malaria
Sporozoites injected under skin by mosquito
Travel to liver through blood
Mature in liver
Re-enters circulation as merozoites
Invades erythrocytes, multiplies and lyse cells. Go on to infect more cells.
Sexual forms taken up by biting mosquito
123
How is Malaria diagnosed?
Using thick and thin blood smears
| Giemsa stained films show parasitaemia
124
Discuss methods for controlling malaria
Use of insecticide treated nets
Prophylactic treatment
There is research into a vaccine
125
What is amoebic dysentery caused by?
Entamoeba histolytica
126
What are the symptoms of amoebic dysentery?
Diarrhoea with blood/pus
127
What are the signs of amoebic dysentery?
```
Cysts in formed stools
Intestinal and extraintestinal infection
Liver abscess (in late stage)
```
128
What is Leishmaniases caused by?
Leishmania species
129
What are the three types of Leishmaniases and their associated signs and symptoms?
Cutaneous Leishmaniasis
-Skin ulceration
Mucocutaneous Leishmaniasis
-Mucosal ulceration
Visceral Leishmaniasis
- Fever
- Weightloss
- Hepatosplenomegaly (swelling of liver and spleen)
130
How is Leishmaniases contracted?
Through sandfly bites
131
How is Leishmaniases diagnosed?
Histology of biopsy
132
What are nematodes?
Roundworms
133
How are nematode infections diagnosed?
Adhesive tape placed against perianal region mane
| Ova seen on microscopy
134
Give an example of a parasitic nematode
Ascaris lumbricoides
135
Describe the life cycle of Ascaris lumbricoides
```
Ingested eggs hatch in intestine
Larvae carried by circulation to lungs
Swallowed again
Adult worms develop in and inhabit small intestine
Ova in faeces
```
136
Note possible symptoms associated with Ascaris lumbricoides
Transient pulmonary symptoms
| A mass of worms may occlude small intestine or common bile duct
137
What are cestodes?
Tapeworms
138
Discuss Taenia species
Cestode
Two species
-Taenia saginata (in beef)
Taenia solium (in pork)
Larval cysts are ingested in meat (the intermedate host)
Adult tapeworm develops in humans
Ova in stools on microscopy
139
Discuss Echnococcus species
```
Cestode
Carried by dogs, wolves, and foxes
Humans ingest eggs (from dog faeces)
Eggs hatch and enter circulation
Hydatid cyst forms in liver
Surgical resection of whole cyst required
```
140
What are trematodes?
Flatworms
141
Give an example of a parasitic trematode
Schistosomiasis (bilharzia)
142
What are the three major species of schistosomiasis and where do the infections present in the body?
S. haematobium - bladder
S. mansoni - intestine
S japonicum - intestine
143
Describe the life cycle of Schistosomiasis
```
§ Ova (eggs) excreted in urine or faeces
§ Miracidia released in fresh water
§ Penetrate body of snail (intermediate host)
§ Cercaria emerge from snails
§ Penetrate human skin
§ Migrate through lungs to liver
§ Mature in liver to worms (schistosomes) that migrate to mesenteric or bladder venules
Lay eggs that cause inflammation
```
144
What are the different techniques which can be used in the diagnosis of parasitic infections?
(Identification in host tissue or excreta)
Microscopy of different stages (PCO)
Thick and thin blood films for malaria
Serology for antibodies
145
Which of the following answers is correct?
Reverse transcriptase inhibitors:
a) Levels should be monitored
b) Used to treat HIV infection
c) Used to treat Herpes Simplex Virus infection
d) Acts only on Gram negative bacteria
e) Acts only on the yeast form of fungi
f) Acts on protein synthesis
g) Macrolide
h) Cephalosporin
i) Tetracycline
j) Used in the treatment of athletes foot
B
146
Which of the following answers is correct?
Vancomycin:
a) Levels should be monitored
b) Used to treat HIV infection
c) Used to treat Herpes Simplex Virus infection
d) Acts only on Gram negative bacteria
e) Acts only on the yeast form of fungi
f) Acts on protein synthesis
g) Macrolide
h) Cephalosporin
i) Tetracycline
j) Used in the treatment of athletes foot
A
147
Which of the following answers is correct?
Classified as a beta-lactam antibiotic:
a) Levels should be monitored
b) Used to treat HIV infection
c) Used to treat Herpes Simplex Virus infection
d) Acts only on Gram negative bacteria
e) Acts only on the yeast form of fungi
f) Acts on protein synthesis
g) Macrolide
h) Cephalosporin
i) Tetracycline
j) Used in the treatment of athletes foot
H
148
Vancomycin and teicoplanin
Which term or description below matches the above?
a) prophylaxis
b) synergy
c) Antagonism
d) A very high MIC
e) Inhibitors of beta-lactamase activity
f) Suitable for topical treatment of fungal infection
g) suitable antibiotics to treat MRSA
h) Aminoglycosides
i) Activity against RSV (respiratory syncytial virus)
j) A very low MIC
G
149
Ribavarin
Which term or description below matches the above?
a) prophylaxis
b) synergy
c) Antagonism
d) A very high MIC
e) Inhibitors of beta-lactamase activity
f) Suitable for topical treatment of fungal infection
g) suitable antibiotics to treat MRSA
h) Aminoglycosides
i) Activity against RSV (respiratory syncytial virus)
j) A very low MIC
I
150
Desirable in order for an antibiotic to be effective against a specific organism
Which term or description below matches the above?
a) prophylaxis
b) synergy
c) Antagonism
d) A very high MIC
e) Inhibitors of beta-lactamase activity
f) Suitable for topical treatment of fungal infection
g) suitable antibiotics to treat MRSA
h) Aminoglycosides
i) Activity against RSV (respiratory syncytial virus)
j) A very low MIC
J
151
Active against Herpes Simplex Virus
Which antimicrobial agent below fits with the statement above?
a) Vancomycin
b) Gentamicin
c) Aciclovir
d) Amoxicillin
e) Flucloxacillin
f) Nystatin
g) Nitrofurantoin
h) Amphotericin
i) Benzylpenicillin
j) Zidovudine
C
152
Used in combined preparation with clavulanic acid
Which antimicrobial agent below fits with the statement above?
a) Vancomycin
b) Gentamicin
c) Aciclovir
d) Amoxicillin
e) Flucloxacillin
f) Nystatin
g) Nitrofurantoin
h) Amphotericin
i) Benzylpenicillin
j) Zidovudine
D
153
An antifungal for topical use only
Which antimicrobial agent below fits with the statement above?
a) Vancomycin
b) Gentamicin
c) Aciclovir
d) Amoxicillin
e) Flucloxacillin
f) Nystatin
g) Nitrofurantoin
h) Amphotericin
i) Benzylpenicillin
j) Zidovudine
F
154
```
True or False:
Penicillin G (benzylpenicillin) interferes with peptidoglycan synthesis in the bacterial cell wall.
```
True
155
True or False
| An organism which is sensitive to an antibiotic will always be killed by it.
False
156
True or False:
| An infection should ideally be treated with an antibiotic with high MIC for the causative organism.
False
157
True or False:
| Amphotericin B acts against a wide range of bacteria.
False
158
True or False:
| Vancomycin and penicillin act on a different stage of cell wall synthesis.
True
159
True or False:
| Aminoglycosides act on DNA synthesis.
False
160
True or False:
| Trimethoprim interferes with protein synthesis at the ribosomal level.
False
161
True or False:
| The differing ribosomes of mammalian and bacterial cells allow selective toxicity.
True
162
True or False:
| Resistance of a known bacterial species to a known antibiotic can always be predicted on theoretical grounds.
False
163
True or False:
| All antibiotic resistance is caused by genes carried on plasmids.
False
164
True or False:
| All penicillins are inactivated by β-lactamase.
False
165
True or False:
| All Staph aureus strains are sensitive to flucloxacillin.
False
166
True or False:
| Amoxicillin is a good choice for ‘blind’ treatment of severe infection with Gram negative coliforms.
False
167
True or false:
| Piperacillin has an extended spectrum and is active against Pseudomonas species.
True
168
True or False:
| Penicillin allergic patients may also be allergic to cephalosporins.
True
169
True or False:
| Vancomycin is only active against anaerobes
False
170
True or False:
| Vancomycin is only active against Gram +ve organisms
True
171
True or False:
Third generation cephalosporins (eg, ceftazidime) have better anti-staphylococcal activity than the earlier cephalosporins
False
172
True or False:
| All antibiotic resistance is caused by β-lactamases
False
173
Metronidazole is widely used to treat anaerobic infection
True
174
True or False:
| Gentamicin is associated with nephrotoxicity
True
175
True or false:
| Gentamicin is associated with otoxicity.
True
176
True or false:
| Pseudomembranous colitis usually results from vancomycin treatment.
False
177
True or false:
| Thrush is due to overgrowth of anaerobic bacteria during broad spectrum antibiotic therapy.
False
178
True or False:
| Serum levels of gentamicin and vancomycin can be monitored in the laboratory to minimise the risk of toxicity.
True
179
True or False:
| In antiobiotic therapy prophylaxis should be given before every operation
False
180
True or False:
| The use of two antibiotics is always more effective than monotherapy.
False
181
True or False:
| MIC and MBC determination is the most accurate way of determining an organism’s antibiotic susceptibility.
True
182
True or False:
| All infections can be adequately treated by seven days of the appropriate antibiotic therapy
False
183
True or false:
| Antibiotic therapy should never be started before the results of laboratory sensitivity tests are available
False
184
True or False:
| Amphotericin B is the treatment of choice for all fungal infections.
False
185
True or False:
| Amphotericin B treatment should not be started until laboratory sensitivity results are available
False
186
True or False:
Intravenous nystatin is indicated for the treatment of serious fungal infection. Topical antifungal preparations can be used to treat fungal skin infections
False
187
True or false:
| Fluconazole is active against yeasts but not against filamentous fungi such as Aspergillus.
True
188
True or false:
| Aciclovir is used to treat infection with all herpes viruses
False
189
True or false: All antiviral drugs act by inhibiting viral nucleic acid synthesi
False
190
True or False:
| Zidovudine (ZDV) alone is the best treatment for AIDS
False
191
True or False:
| Oseltamivir is widely used to treat hepatitis B infection
False
192
True or False:
| Aciclovir treatment abolishes carriage of herpes simplex virus.
False
