Microbiology Flashcards
(371 cards)
1
Q
What is a pathogen?
A
Organism that causes or is capable of causing disease
2
Q
What is a commensal?
A
Organism which colonises host but causes no disease in normal circumstances
3
Q
What is an opportunist pathogen?
A
Microbe that only causes disease if host defences are compromised
4
Q
What is virulence?
A
Degree to which a given organism is pathogenic
5
Q
What is asymptomatic carriage?
A
When a pathogen is carried harmlessly at a tissue site where it causes no disease
6
Q
What are round bacteria called?
A
Cocci
7
Q
What are rod shaped bacteria called?
A
Bacilli
8
Q
What is a purple Gram stain?
A
Positive
9
Q
What is a pink Gram stain?
A
Negative
10
Q
What specialised stain detects mycobacterium??
A
Ziehl-Neelsen stain
11
Q
What gives bacteria a hardened structure?
A
Spores
12
Q
What component of a bacterial outer membrane can give rise to toxic shock?
A
Endotoxin
13
Q
How big are typical bacterial chromosomes?
A
2-4x103 kb
14
Q
How can bacteria be mutated?
A
Base substitution
Deletion
Insertion
15
Q
How can genes be transferred in bacteria?
A
Transformation
Transduction
Conjugation
16
Q
What is coagulase?
A
An enzyme produced by bacteria that clots blood plasma to protect against phagocytosis
17
Q
What is an important coagulase positive bacteria?
A
Staphylococcus aureus
18
Q
What is the normal habitat for staphylococcus?
A
Nose and skin
19
Q
How is staph aureus spread?
A
Aerosol and touch
20
Q
What is MRSA resistant to?
A
B-lactams, gentamicin, erythromycin, tetracycline
21
Q
What are the virulence factors of Staph aureus?
A
- Pore-forming toxins
- Proteases (exfoliatin)
- Toxic shock syndrome toxin
- Protein A
22
Q
Give 3 pyogenic conditions associated with Staph aureus
A
- Wound infections
- Septicaemia
- Abscesses
23
Q
Give 2 toxin mediated conditions associated with staph aureus
A
- Toxic shock syndrome
2. Food poisoning
24
Q
Give 2 coagulase negative conditions associated with Staph aureus
A
- Infected implants
2. Endocarditis
25
What is the main virulence factor for S. epidermidis?
Ability to form persistent biofilms
26
What are the 3 types of haemolysis?
1. Alpha - partial lysis (greening)
2. Beta - complete lysis
3. Gamma (non) - no lysis
27
How can streptococci be classified?
1. Haemolysis
2. Lancefield typing
3. Biochemical properties
28
What is Lancefield grouping?
Method of grouping catalase negative, coagulase negative bacteria based on bacterial carbohydrate cell surface antigens
29
Give 3 infections caused by S. pyogenes
1. Cellulitis
2. Tonsillitis
3. Scarlet fever
30
What are the 2 complications of S. pyogenes infections?
1. Rheumatic fever
| 2. Glomerulonephritis
31
What are the virulence factors for S. pyogenes?
1. Enzymes
2. Toxins
3. Capsule
4. M protein
32
What are the causes of S. pneumoniae?
1. Pneumonia
2. Otitis media
3. Sinusitis
4. Meningitis
33
What are the predisposing factors for S. pneumoniae infection?
1. Impaired mucus trapping
2. Hypogammaglobulinaemia
3. Asplenia
34
Which streptococci are important in infective endocarditis?
1. S. sanguinis
| 2. S. oralis
35
What is the most virulent group of streptococci?
Milleri group
36
Why are there differences in staining with Gram?
Morphological differences in the bacteria
37
What is endotoxin comprised of?
Lipid A, core antigen, somatic antigen
38
How does lipid A trigger an innate immune response?
TLR4 signalling
39
What are the main colonisation factors?
1. Adhesins
2. Invasins
3. Nutrient acquisition
4. Defence against host
40
Why might antibodies against the same species of bacteria not be recognised in different patients?
There is structural variability amongst different strains of the same species
41
What is a serovar?
Strains of bacteria with variant cell surface antigens
42
What is a serogroup?
A group of strains with have a surface antigen in common, but differ in one or more other surface antigens
43
Name 6 principal infections caused by E. coli
1. Wound infections
2. UTIs
3. Gastroenteritis
4. Traveller's diarrhoea
5. Bacteraemia
6. Meningitis
44
What is the major complication of E. coli food poisoning?
Haemolytic ureic syndrome
45
How many patients with a EHEC infection develop haemolytic ureic syndrome?
10%
46
What are the 5 symptoms of a shigella infection?
1. Small volume
2. Pus and blood in stools
3. Prostrating cramps
4. Pain in straining
5. Fever
47
How is shigella spread?
Person-to-person, contaminated food and water
48
How do shigella invade epithelial cells?
Through M cells
49
How does Shigella ensure survival in macrophages?
It rapidly induces apoptosis of macrophages
50
What are the 2 species of salmonella?
1. S. enterica
| 2. S. bongori
51
What are the 3 conditions caused by S. enterica?
1. Gastroenteritis/enterocolitis
2. Enteric fever
3. Bacteraemia
52
What can klebsiella pneumoniae cause?
1. UTI
2. Pneumonia
3. Surgical wound infections
4. Bacteraemia
5. Sepsis
53
How is cholera transmitted?
1. Shellfish ingestion
| 2. Contaminated drinking water
54
How much fluid a day can be lost in cholera?
20L/day
55
What is the mortality for untreated cholera?
50-60%
56
What is the leading cause of nosocomial pneumonia in ICU patients?
Pseudomonas aeruginosa
57
Name 5 opportunistic infections caused by haemophilus influenzae
1. Meningitis
2. Bronchopneumonia
3. Epiglottitis
4. Bacteraemia
5. Pneumonia
58
What is the main cause of meningitis
Type b strain of H. influenzae
59
What is the mortality of Legionnaires' disease?
15-20%
60
What causes Legionnaires' disease?
Legionella pneumophila
61
What does Legionnaires' disease cause?
Excessive influx of neutrophils into lungs causing severe inflammatory pneumonia
62
What does bordetella pertussis cause?
Whooping cough
63
How is B. pertussis transmitted?
Aerosol
64
What are the 2 clinically important species of neisseria?
1. N. meningitidis
| 2. N. gonorrhoeae
65
In what % of the population is N. meningitidis present in the nasopharynx?
5-10%
66
What is the mechanism of N. meningitidis?
Invasion of meninges, bacteria enter CSF of subarachnoid space from blood stream after crossing BBB
67
What serious complications can gonorrhoea cause in women?
Salpingitis
| Pelvic inflammatory disease
68
What is the most common cause of food poisoning in UK?
Campylobacter
69
What diseases does Helicobacter pylori play a role in?
Gastritis
| Peptic ulcer disease
70
What do bacteroides often cause?
Peritoneal cavity infections
71
How is chlamydia detected?
Serum antibodies or PCR
72
What are the 2 developmental stages of chlamydia?
1. Elementary bodies
| 2. Reticulate bodies
73
Describe the elementary body stage of chlamydia development
1. Infectious
2. Enter cell through endocytosis
3. Prevent phagosome-lysosome fusion
74
Describe the reticulate body stage of chlamydia development
1. Replicative
2. Non-infectious
3. Acquire nutrients from host cell
75
What C. trachomatis causes chlamydia in STI form?
Genital tract biovar
76
What are the symptoms of Weil's disease?
1. Jaundice
2. Acute renal failure
3. Acute hepatic failure
4. Pulmonary distress
5. Haemorrhage
77
What causes Weil's disease?
Leptospira interrogans
78
What is the primary stage of syphilis?
A localised infection, days-weeks post infection usually in the form of an ulcer
79
What is the secondary stage of syphilis?
A systemic infection, 1-3 months post-infection affecting skin, joints and muscles
80
What is the tertiary stage of syphilis?
Infection of bone and soft tissue, aorta and nervous system, several years post-infection
81
What are the 4 main groups of gram negative pathogens?
1. Proteobacteria
2. Bacteroides
3. Chlamydia
4. Spirochaetes
82
Give 3 characteristics of fungi
1. Eukaryotic
2. Chitinous cell wall
3. Heterotrophic
83
What forms can fungi exist in?
Yeast or mould
84
What are yeasts?
Small single celled organisms that divide by budding
85
What are moulds?
Fungi which form multicellular hyphae and spores
86
What are dimorphic fungi?
Fungi which exist as both yeasts and moulds switching between the two when conditions suit
87
Why do fungi often not cause human infection?
1. Inability to grow at 37C
| 2. Innate and adaptive immune response
88
What genera of fungi are most often implicated in human infection?
1. Ascomycota
2. Basidiomycota
3. Mucormycota
89
Name 3 common fungal infections
1. Vulvovaginal candidiasis
2. Otitis externa
3. Tinea pedis
90
What life-threatening fungal infections can affect immunocompromised hosts?
1. Candida spp. line infections
2. Invasive aspergillosis
3. Pneumocystis
4. Cryptococcosis
5. Mucormycosis
91
What ways are there of diagnosing fungal disease?
1. Microscopy and histology
2. Culture
3. Molecular methods and serology
92
Name 3 fungi in the DDx of onychomycosis
1. Trichophyton spp.
2. Epidemophyton spp.
3. Microsporum spp.
93
Name 3 non-fungal causes considered in the DDx of onychomycosis
1. Psoriasis
2. Trauma
3. Lichen planus
94
What is the diagnosis of onychomycosis?
Microscopy and culture of nail clippings/scrapings
95
What are the most common treatments for onychomycosis?
Terbinafine or itraconazole
| Topical amorolfine
96
What is thrush?
White adherent plaques on oral or genital mucosa
97
Name 4 things commonly associated with thrush
1. Immunocompromised
2. Diabetes
3. Antibiotic use
4. Pregnancy
98
How is thrush treated?
Topical antifungals or oral fluconazole
99
What is invasive aspergillosis treated with?
Voriconazole
100
Who does invasive aspergillosis often affect?
Immunocompromised and post-influenza disease
101
What causes invasive aspergillosis?
Galactomannan
102
How is pneumocystis diagnosed?
PCR of induced sputum or BAL
103
How is pneumocystis pneumonia treated?
Co-trimoxazole
104
Why are fungi harder to treat than bacteria?
They are eukaryotic
105
What do fungal cell membranes contain?
Ergosterol
106
Where do allylamines tend to distribute extensively?
To poorly perfused sites e.g. skin and nail beds
107
What is used to treat dermatophytes?
Terbinafine
108
What are azoles?
Dose dependent inhibitors of 14a-sterol demethylase
109
Name 3 azoles
1. Fluconazole
2. Itraconazole
3. Voriconazole
110
What is voriconazole used to treat?
Invasive aspergillosis
111
Give 3 side effects of azoles
1. Transaminitis
2. Alopecia
3. Severe hepatitis
112
What class of drugs are used for severe or resistant fungal disease?
Echinocandins
113
Name 2 echinocandins
1. Caspofungin
| 2. Micafungin
114
What is the mechanism of action of echinocandins?
Inhib 1,3 beta glucan synthase
115
What is the most common fungal cause of onychomycosis?
Trichophyton tubrum
116
Who does pneumocystis pathogenesis often affect?
Moderate-severely immunocompromised
117
Give 3 treatments of pneumocystis pathogenesis
1. Co-trimoxazole
2. Clindamycin
3. Atovaquone
118
What is a virus?
An infectious, obligate intracellular parasite comprising genetic material surrounded by a protein coat and/or a membrane
119
What do viruses exist as when not in an infected cell?
Virions
120
Why are viruses not classed as living?
They don't feed, respire or reproduce independently
121
How do viruses replicate?
1. Migration of genome to host cell nucleus
2. Transcription to mRNA using host materials
3. Use cell materials for their replication
4. Translation of viral mRNA to produce structural proteins, viral genome and non-structural proteins
122
How are new virus particles released?
1. Cell lysis
2. Budding
3. Exocytosis
123
How can viruses cause disease?
1. Direct destruction of host cells
2. Modification of host cells
3. Over-reactivity of immune system
4. Damage through cell proliferation
5. Evasion of host defences
124
How does poliovirus cause disease?
Host cell neuron lysis and death
125
How does rotavirus cause disease?
Atrophies villi and flattens epithelial cells
126
What are 4 symptoms of hepatitis B?
1. Jaundice
2. Pale stool
3. Dark urine
4. RUQ pain
127
How does human papillomavirus cause cervical cancer?
Continuous expression of oncoprotein causing cellular DNA mutations
128
How can the host defence be evaded at a cellular level?
1. Latency
| 2. Cell-cell spread
129
How can the host defence be evaded at a molecular level?
1. Antigenic variability
| 2. Prevention of host cell apoptosis
130
What is antigenic variability?
Ability to change surface antigens in order to evade host's immune system
131
What does prevention of host cell apoptosis allow?
Allows virus to continue replicating within the cell so more virus is produced and then released
132
Name 2 ways viruses evade host defence
1. Downregulation of interferon and other intracellular host defence proteins
2. Interference with host cell antigen processing pathways
133
What are protozoa?
Microscopic unicellular eukaryotes
134
What are the major groups of protozoa?
1. Flagellates
2. Amoebae
3. Microsporidia
4. Sporozoan
5. Ciliates
135
What is African trypanosomiasis also called?
Sleeping sickness
136
What is the vector for African trypanosomiasis?
Tsetse fly bite
137
Where does African trypanosomiasis occur?
Remote areas of Africa
138
What are the symptoms of African trypanosomiasis?
```
Personality change
Drowsiness
Flu-like symptoms
Chancre
Coma and death
```
139
How is African trypanosomiasis diagnosed?
Blood film or CSF
140
What is American trypanosomiasis also called?
Chagas disease
141
What is the vector for American trypanosomiasis?
Triatomine bug
142
Where is American trypanosomiasis found?
Central and South America
143
What are 3 acute symptoms of American trypanosomiasis?
1. Fever
2. Headache
3. Romana's sign
144
What are 3 chronic symptoms of American trypanosomiasis?
1. Cardiomyopathy
2. Megaoesophagus
3. Megacolon
145
What causes Leishmaniasis?
Leishmania spp.
146
What is the vector for Leishmaniasis?
Female sandfly
147
Where is Leishmaniasis found?
Africa, Asia, South America
148
What are the 3 clinical manifestations of Leishmaniasis?
1. Cutaneous
2. Mucocutaneous
3. Visceral Kala Azar
149
What is seen in cutaneous and mucocutaneous Leishmaniasis?
Ulceration and destruction, scarring
150
How quickly do cutaneous and mucocutaneous Leishmaniasis usually resolve?
8 weeks
151
Give 5 symptoms of visceral Leishmaniasis
1. Fever
2. Bone marrow suppression
3. Weight loss
4. Hepato-splenomegaly
5. Anaemia
152
How is trichomoniasis vaginalis spread?
Sexually transmitted
153
How does trichomoniasis vaginalis present in men?
1. Often asymptomatic
2. Urethritis
3. Prostatitis
154
How does trichomoniasis vaginalis present in women
1. Purulent discharge
2. Abdo pain
3. Dysuria
4. Vulvar/cervical lesions
155
How are most protozoa treated?
Metronidazole
156
How is giardiasis spread?
Faeco-oral spread
157
Give 4 symptoms of giardiasis
1. Diarrhoea
2. Cramps
3. Bloating
4. Flatulence
158
What are the risk factors for giardiasis?
1. Recent travel
2. Close contacts
3. Childcare
159
How is giardiasis diagnosed?
Stool microscopy looking for cysts and trophozoites
160
What causes amoebiasis?
Entaemoeba histolytica
161
How is amoebiasis spread?
Faeco-oral spread, contaminated food and water
162
What are the symptoms of amoebiasis?
1. Dysentery
2. Colitis
3. Liver and lung abscesses
163
How is cryptosporidiosis spread?
Contaminated food and water
164
What are 4 symptoms for cryptosporidiosis?
1. Diarrhoea
2. Vomiting
3. Fever
4. Weight loss
165
How is cryptosporidiosis diagnosed?
Pink in acid fast staining
166
Who is cryptosporidiosis often seen in?
Immunocompromised patients
167
How is toxoplasmosis spread?
Contaminated food and water, contact with feline faeces
168
Give 3 conditions toxoplasmosis can cause?
1. Disseminated disease
2. Chorioretinitis
3. Toxoplasma encephalitis
169
How is toxoplasmosis diagnosed?
Ring enhancing lesion on brain CT
170
What is the vector for malaria?
Female anopheles mosquito
171
How is malaria diagnosed?
Blood film
172
Give 5 symptoms of malaria
1. Fever
2. Headache
3. Abdo pain
4. Fatigue
5. Vomiting
173
What are 4 signs of malaria?
1. Anaemia
2. Jaundice
3. Hepatosplenomegaly
4. Black water fever
174
What are the stages of the malaria lifecycle?
1. Liver stage
2. Blood stage
3. Vector stage
175
What happens in the liver stage of the malaria lifecycle?
1. Mosquito takes a blood meal and injects sporozoites
2. These travel to liver and infect liver cells
3. Mature into shizonts
4. Shizont rupture releases merozoites into blood
176
In what types of malaria can a dormant stage persist in the liver?
P. vivax and P. ovale
177
What happens in the blood stage of the malaria lifecycle?
1. Merozoites enter circulation and inject RBCs
2. Enter ring stage trophozoites which mature into schizonts
3. Schizonts rupture releasing more merozoites
4. Some immature trophozoites differentiate into sexual stage gametocytes
178
What stage of the malarial lifecycle gives rise to symptoms?
Blood stage
179
What happens in the vector stage of the malaria lifecycle?
1. Mosquito takes a blood meal ingesting gametocytes
2. These mature into an oocyst which ruptures releasing sporozoites
3. Sporozoites are injected into host during next blood meal
180
How long is the process of development in the malaria lifecycle?
9 days
181
What causes the severe form of malaria?
P. falciparum
182
Why does P. falciparum cause more severe malaria?
1. Obstructed microcirculation
2. Rosetting
3. Cytoadherence
4. Sequestration of parasites in major organs
183
Why does haemolysis occur in malaria?
Infected cell lysis and immune mediated killing
184
Give 3 symptoms of cerebral malaria
1. Vascular occlusion
2. Seizures
3. Raised ICP
185
Give 3 symptoms of ARDS
1. Anaemia
2. SOB
3. Pulmonary oedema
186
Give 3 symptoms of renal failure caused by malaria
1. Dehydration
2. Lowered BP
3. Haemoglobinuria
187
Give 3 symptoms of bleeding caused by malaria
1. Thrombocytopenia
2. Epistaxis
3. Abnormal bleeding
188
Give 3 symptoms of shock caused by malaria
1. Bleeding
2. Hypotension
3. Pale
189
What are the 5 types of complicated malaria?
1. Cerebral
2. ARDS
3. Renal failure
4. Sepsis
5. Bleeding/anaemia
190
How is malaria diagnosed?
Thick and thin blood films looking for black dots
191
What is the emergency malaria treatment?
IV artesunate
192
What is used to prevent relapses in P. ovale and P. vivax malaria?
Primaquine
193
What is the microbiome?
The totality of microorganisms, their genetic elements and their environmental interactions in an environment
194
What eliminates virus infected cells?
Cytotoxic C lymphocytes
195
How can viruses cause cell damage?
Direct cell toxicity, innate and adaptive immune responses
196
How can toxins be classified?
1. Tissue target
2. Molecular action
3. Biological effect
4. Contribution to disease process
197
What do the changes in coat antigens in influenza result in?
Antigen shift and antigen drift
198
What is antigen drift?
Spontaneous mutations which occur gradually giving minor changes in haemagglutinin and neuraminidase
199
What is antigenic shift?
Sudden emergence of a new subtype different to that of preceding virus
200
What is seen in epidemics?
Antigen drift
201
What is seen in pandemics?
Antigen shift
202
Describe influenza
Spherical particles surrounded by lipid bilayer acquired from infected host cell
203
What determines the defence mechanism employed to a bacterial infection?
Number of organisms and virulence
204
What response is given to extracellular bacteria?
Antibody response
205
What response is given to intracellular bacteria?
Cellular response
206
How do bacteria compete with host cells?
1. Sequestering nutrients
2. Using novel metabolic pathways
3. Out-competing other micro-organisms
207
What is the function of adhesins?
Help bacteria bind to mucosal surfaces
208
How can bacteria stick together on a cell surface?
Secrete an extracellular polymeric substance of protein, polysaccharides and DNA
209
What is the function of a biofilm?
Helps protect against antimicrobials
210
How do macrophages kill infected cells?
Lytic enzyme release
211
What is the function of pattern recognition receptors?
Recognise pathogen associated molecular patterns but also damage associated molecular patterns from host cells
212
What can cause tissue damage?
1. Trauma
2. Necrosis
3. Neoplasia
4. Infection
213
What is an antibiotic?
Agent produced by microorganisms that kill or inhibit the growth of other microorganisms in high dilution
214
How do antibiotics work?
Bind to a target site on a bacteria defined as a point of the biochemical reaction crucial to the survival of the bacterium
215
What determines the binding site bound?
Antibiotic class
216
What methods do antibiotics use to kill bacteria?
1. Binding to cell wall and inhibition of cell wall synthesis
2. interference with nucleic acid synthesis or function
3. Inhibition of DNA gyrase
4. Inhibition of ribosomal activity and protein synthesis
5. Inhibition of folate synthesis and carbon unit metabolism
217
What class of antibiotics inhibit cell wall synthesis?
Penicillins
218
How are bacteria pathogenic?
Bacterial raison d'être and damage
219
What is bacterial raison d'etre?
Bacteria attach and enter, spread locally and multiply and evade host defences
220
How do bacteria cause damage?
1. Direct
2. Exotoxin
3. Endotoxin
4. Inflammation
5. Immune-pathology
6. Diarrhoea
221
What is the mechanism of action of beta lactam?
Disrupt peptidoglycan production by covalently and irreversibly binding to PBPs causing cell wall lysis
222
What must happen for beta lactam to bind to PBPs?
They must diffuse through the bacterial cell wall
223
What is bacteriostatic?
Prevents growth go bacteria - prevent them multiplying
224
How is bacteriostatic defined?
Minimum bactericidal conc. to minimum inhibitory conc. of >4
225
How to bacteriostatic antibiotics function?
Inhibit protein synthesis, DNA replication or metabolism
226
What is bactericidal?
The agent kills the bacteria
227
How do bactericidal antibiotics function?
Inhibit cell wall synthesis
228
When are bactericidal antibiotics used?
1. Poor tissue penetration
2. Difficult to treat infections
3. Need to eradicate infection quickly
229
What makes a good antibiotic?
It remains at the binding site for a sufficient period of time in order for the metabolic processes of the bacteria to be sufficiently inhibited
230
What are the 2 major determinants of antibacterial effects?
Concentration and time antibiotic remains on binding sites
231
What determines the interval antibiotics are given at?
Half-life
232
Why might antibiotics not work?
1. Change antibiotic target
2. Prevent antibiotic access
3. Remove antibiotic from bacteria
4. Destroy antibiotic
233
How do bacteria acquire resistance?
1. Spontaneous gene mutation
| 2. Horizontal gene transfer
234
What types of horizontal gene transfer are there?
1. Conjugation
2. Transduction
3. Transformation
235
What is acquired resistance?
A bacterium which was previously susceptible obtains the ability to resist the activity of a particular antibiotic
236
What is a spontaneous gene mutation?
New nucleotide base pair change in amino acid sequence change to enzyme or cell structure reduced affinity or activity of antibiotic
237
What is conjugation?
Sharing of extra-chromosomal DNA plasmids
238
What is transduction?
Insertion of DNA by bacteriophages
239
What is transformation?
Picking up naked DNA
240
What is MRSA?
Methicillin resistant staphylococcus aureus
241
What is MRSA resistant to?
All beta-lactam antibiotics and methicillin
242
What are carbapenems resistant to?
Degradation by beta-lactamases or cephalosporinases
243
How can drug resistance be tested for in bacteria?
1. Minimum inhibitory concentration
2. Antibiotic sensitivity testing
3. Breakpoint plates
4. Chromogenic plates
5. Mechanism-specific tests
6. Genotypic methods
244
What is breakpoint?
A discriminating concentration used to define isolates as susceptible, intermediate or resistant
245
What data sources set breakpoints?
1. MIC distributions
2. Phamacokinetics and pharmacodynamics
3. Clinical and bacteriological response rates
4. Phenotypic and genotypic resistance markers
246
What is the formula for breakpoint concentration?
(Cmax/et) x f x s
247
Give 4 factors to take into account for patient safety with antibiotics
1. Side effects
2. Age
3. Liver and renal function
4. Pregnancy
248
What do beta lactams act on?
Cell wall of bacteria
249
Name 4 beta lactams
1. Amoxicillin
2. Penicillin
3. Cefuroxime
4. Meropenem
250
What are the benefits of cephalosporins?
1. Good for people with penicillin allergy
2. Better for more resistant bugs
3. Get into different parts of body
251
Name 2 glycopeptides
1. Vancomycin
| 2. Teicoplanin
252
Why are glycopeptides given with caution?
Can cause renal impairment
253
What are the 5 functional groups of antibiotic?
1. Cell wall synthesis inhibitors
2. Protein synthesis inhibitors
3. Nucleic acid synthesis inhibitors
4. Anti-metabolites
5. Membrane function inhibitors
254
What can be used to treat necrotising fasciitis?
Clindamycin
255
What are risk factors for Buruli ulcer?
Warm environment and barefoot
256
What are mycobacteria?
Aerobic, non-spore forming, non-motile bacillus
257
Why do mycobacteria give a slow disease development?
They grow slowly
258
What stain is used for acid fast bacilli?
Ziehl-Neelsen
259
What is nucleic acid detection recommended for?
Rapid diagnosis of TB in endemic countries
260
How do hosts kill acid fast bacilli?
Using microbicidal molecules and acidification which aids digestion and degradation by proteases which results in generation of antigens for presentation to T cells
261
What are granulomas?
Lesions that arise in a response that tries to contain mycobacteria
262
What does the immune response to M. tuberculosis focus on?
Th1
263
What is the lifetime risk for TB reactivation?
10%
264
Who is at increased risk of TB reactivation?
1. Age
2. Malnutrition
3. Intensity of exposure
4. Immunosuppression
265
How is the reactivity to M. tuberculosis measured?
Tuberculin skin test and interferon gamma release assays
266
What is seen in a positive tuberculin skin test?
Skin swelling and redness
267
What does interferon gamma release assay distinguish?
If infection is M. tuberculosis or BCG tuberculosis
268
What is seen in tuberculoid leprosy?
1. Tissue hypersensitivity and granulomata
2. Paucibacillary lesions with low numbers of mycobacteria
3. Tissue damage
4. Th1 responses
269
What is seen in lepromatous leprosy?
1. Lesions full of bacilli
2. Little or poorly formed granulomata
3. Extensive skin lesions
4. Th2 responses
270
Why is leprosy associated with deformities?
Causes skin and nerve supply damage so don't notice damage and pain occurring
271
Why do mycobacterial infections need prolonged treatment?
It replicates slowly
272
Name 3 common tuberculosis drugs
1. Isoniazid
2. Rifampicin
3. Pyrazinamide
273
Why do mycobacteria have unique staining patterns?
They have unique lipid rich cell walls
274
What bacilli distribution is seen in primary TB?
Granuloma, lymphatics and lymph nodes
275
What are the phases of HIV infection?
1. Acute primary infection
2. Asymptomatic phase
3. Early symptomatic HIV
4. AIDS
276
What is the CD4 level seen in AIDS?
<200
277
What is seen in the acute primary infection of HIV?
1. Fall in CD4 levels
| 2. Acute rise in viral load
278
What is seen in the asymptomatic phase of HIV?
Progressive loss of CD4 T cells resulting in poor immunity
279
What are the 2 key markers of HIV infection?
1. CD4 T cell count
| 2. HIV viral load
280
Name 3 infections often seen in AIDS
1. Candidiasis
2. Mycobacterium TB
3. Toxoplasmosis of internal organs
281
Name 3 non-infectious conditions seen in AIDS
1. Kaposi's carcinoma
2. HIV dementia
3. Non-Hodgkin's lymphoma
282
How long do symptoms typically last in primary HIV infection?
2-4 weeks
283
Name 3 symptoms seen in primary HIV infection
1. Severe weight loss
2. Fever
3. Rash
284
What should be done in a patient with fever, rash and non-specific features?
1. Take a sexual history
2. Think of HIV
3. Tell lab to check for antigen
285
How long does it typically take for HIV antibody to be positive?
4-10 weeks
286
When is the viral load typically at a steady state by?
3-6 months post-infection
287
What findings are seen in the clinically latent phase of HIV?
Persistent generalised lymphadenopathy
288
Why are HIV+ women given annual smear tests rather than 3 yearly?
They are at increased risk of HPV infection and cervical intra-epithelial neoplasia
289
What is the commonest opportunistic infection in HIV?
Pneumocystis pneumonia (PCP)
290
Name 3 respiratory diseases common in HIV
1. Bacterial pneumonia
2. Tuberculosis
3. PCP
291
What is the Tx for cerebral toxoplasmosis?
Sulphadiazine + pyrimethamine
292
Name 3 CNS conditions seen in HIV
1. Tuberculoma
2. Pneumococcal meningitis
3. Toxoplasmosis
293
What CD4 count is often seen in HIV patients with lymphoma?
<100/ul
294
What is the Tx for Kaposi's sarcoma?
1. HAART
2. Local radiotherapy
3. Systemic chemotherapy
295
What are the mechanisms of HIV medications?
1. Reverse transcriptase inhibitors (nucleoside and non-nucleoside)
2. Protease inhibitors
3. Fusion inhibitors
296
What is HAART?
Highly active anti-retroviral therapy
297
What combinations can be given on HAART?
1. 2 NRTI + 1 NNRTI
| 1. 2 NRTI + PI
298
Wait is the goal of HAART?
Reduce viral load to <50 copies/ml and increase CD4 count
299
What proportion of HIV cases are in Sub-Saharan Africa?
61%
300
What is classed as a late HIV diagnosis?
CD4 <350
301
How many deaths from AIDS are there annually?
~770,000
302
What are the UNAIDS 90/90/90 goals?
1. 90% of people living with HIV being diagnosed
2. 90% diagnosed on antiretroviral therapy
3. 90% viral suppression for those on ART by 2020
303
How many people in the Uk are living with HIV?
~104,000
304
What groups are at risk of being diagnosed late with HIV?
1. Women
2. >65s
3. Black African
4. Heterosexual
5. Outside of London
305
What are the transmission routes for HIV?
1. Blood
2. Sexual
3. Vertical
306
Name 4 HIV prevention treatments
1. ART
2. PEP (within 72hr)
3. Circumcision
4. PreP
307
What is the reduction in HIV transmission with circumcision?
50%
308
What is PEP?
Post-exposure prophylaxis
309
What is involved in PEP?
28 days Combination Antiretroviral Therapy within 72 hours
310
What is the risk reduction of HIV when using pre-exposure prophylaxis?
86%
311
Name 3 behavioural preventative measures against HIV
1. Appropriate sex education
2. Reduce frequency of partner change
3. Consistent condom usage
312
What are the guidelines for HIV testing?
1. Unexplained blood dysplasia
2. Oral candida
3. Unexplained lymphadenopathy
4. Ongoing diarrhoea
5. Unexplained weight loss
313
Give 4 risk factors for HIV
1. PWID
2. MSM
3. Multiple sexual partners
4. Rape
314
Give 3 advantages to point of care testing for HIV
1. Outreach into community settings
2. Increase patient choice
3. Earlier diagnosis
315
Give 3 disadvantages of self-testing
1. Anxiety
2. Misdiagnoses
3. Inadequate partner notification
316
What are the stages of of viral replication?
1. Attachment
2. Cell entry
3. Interaction with host cells
4. Replication
5. Assembly
6. Release
317
What happens in cell entry?
Central viral core caring nucleic acid and some associated proteins enter host cell
318
Why do viruses interact with host cells?
To use cell materials for their replication and to subvert host cell defence mechanisms
319
Where does viral assembly occur in viruses?
1. Nucleus
2. Cytoplasm
3. Cell membrane
320
What are the stages of HIV replication?
1. Attachment
2. Entry
3. Uncoating
4. Reverse transcription
5. Genome integration
6. Transcription of viral RNA
7. Splicing of mRNA and translation into proteins
8. Assembly of new virions
9. Budding
321
What does HIV release to chop up the host genome?
Reverse transcriptase and integrase
322
What is the function of viral protease?
Helps chop up amino acid chains to restructure proteins into new capsid so it can be infective again
323
How do HIV get genomic variability?
Reverse transcription step of replication is error prone
324
The interaction between what is conserved in all primate lentiviruses?
CD4 and gp120
325
What is the antigen against which we raise antibodies when doing a HIV test?
Glycoprotein 120 (gp120)
326
What is the effect of genome mutations in HIV infection?
It makes it hard to respond with the immune system and makes treatment tricky
327
What does Pol encode?
HIV enzymes
328
What gene increases infectivity in HIV?
Nef
329
What gene contributes to viral replication in HIV?
Tat
330
What cells are often infected with HIV?
1. CD4 T cells
2. Macrophages
3. Dendritic cells
331
What is a major barrier to a vaccine against HIV-1?
Lack of identification of protective immune responses
332
What is seen in long-term non-progressors?
No symptoms of infection or signs of AIDS after at least 7 years infection with CD4 count >600 cells/ml in the absence of treatment
333
What immune system consequences characterises HIV?
Progressive decline in number and function of CD4 T-lymphocytes
334
What are the mechanisms of CD4 depletion?
1. Direct cytotoxicity of infected cells
2. Activation induced death
3. Decreased production
4. Redistribution
5. Bystander cell killing
335
What is the primary infection of varicella zoster virus (VZV)?
Varicella chickenpox
336
What is the secondary reactivation of VZV?
Herpes zoster shingles
337
What is the incubation period for chickenpox?
7 to 21 days
338
How long do the symptoms usually last in chickenpox?
10 days
339
When is the period of highest infectivity seen in chickenpox?
2 days before rash to 2 days after rash
340
What groups is chickenpox serious in?
1. Immunocompromised
2. Adults
3. Pregnant women
4. Smokers
5. Infants
341
What are the stages of rash evolution in chickenpox?
1. Macule (red blotch, flat)
2. Papule (lumpy)
3. Vesicle (viral replication, blisters)
4. Pustule (inflammatory response)
5. Crust
342
What is the hallmark feature of chickenpox?
Centrifugal distribution of rash
343
How is a chickenpox infection diagnosed?
VZV/HSV PCR
344
Give 3 complications of chickenpox
1. Dehydration
2. Cerebellar ataxia
3. Chickenpox pneumonitis
345
What is the mortality for chickenpox pneumonitis?
6% with treatment, 30% without
346
What is the prevalence of foetal varicella syndrome?
10-15%
347
What happens in foetal varicella syndrome?
Shingles in first year of life
348
How many people in the UK get shingles each year?
250,000
349
Where is shingles reactivation most often localised to?
Thoracic region
350
What is a complication of shingles?
Post-herpetic neuralgia
351
What are the 3 types of worm?
1. Nematodes
2. Trematodes
3. Cestodes
352
What do adult worms require to replicate?
A period of development outside the body
353
What is the pre-patient period?
Interval between acquiring infection and appearance of eggs in stool/urine
354
What is ascariasis lumbricoides?
Large roundworm
355
What are the treatments for roundworm?
Peperazine, pyrantel, mebendazole, levamisole
356
What is the diagnosis for worms?
Stool microscopy
357
What worm is very common in the UK?
Enteriobius vermicularis (pinworm or threadworm)
358
How is pinworm ingested?
Contaminated hands
359
What is the pre-patient period for pinworm?
40 days
360
Give 3 effects of pinworm
1. Appendicitis
2. Endometritis
3. Pruritis ani
361
What is the treatment for pinworm?
1. Mebendazole
2. Piperazine
3. Pyrantel
362
What are 3 symptoms of trichuriasis?
1. Anaemia
2. Bloody diarrhoea
3. Rectal prolapse
363
Wha causes heated disease?
Taenia sodium (pork tapeworm)
364
What is the effect of pork tapeworm on the brain?
Fills it up, makes it look soapy
365
What is the intermediate host for flukes?
Snail
366
What causes schistosomiasis?
Schistosoma haematobium
367
How many Schistosoma haematobium infected patients present with Katayama fever?
50%
368
Give 3 clinical features of Katayama fever?
1. Fever
2. Eosinophilia
3. Diarrhoea
369
Give 3 clinical features of S. haematobium
1. Granulomatous lesions
2. Uropathy
3. Calcified bladder
370
How is schistosomiasis diagnosed?
1. Serology
2. Urine
3. Stool sample
4. Rectal biopsy
5. USS
371
Give 3 ways of treating schistosomiasis
1. Praziquantel
2. Isoquinoline
3. Metriphonate
