Microbiology Flashcards
(368 cards)
1
Q
Mechanism of action of Antibiotics
A
Inhibit cell wall synthesis ------- β lactams(Penicillin, Cephlosporin, Carbapenems) ------- Glycopeptides (Vancoymycin, Teicoplanin) Inhibit protein synthesis ------- Aminoglycosides (Gentamicin) ------- Tetracycline (Doxycycline) ------- Macrolide (Erythromycin) ------- Chloramphenicol ------- Oxazolidinones (Linezolid) Inhibit DNA synthesis ------- Fluoquinolone (Ciprofloxacin) ------- Nitroimidazoles (Metronidazole) Inhibit RNA synthesis ------- Rifamycin (Rifampacin) Cell membrane toxin ------- Polymyxin (Colostin) ------- Cyclic lipopeptide (Daptomycin) Inhibit folate metabolism ------- Sulfonamide (Sulphamethoxazole) ------- Diaminopyramidines (Trimethoprim)
2
Q
Differences in cell structure in Gram +ve and Gram -ve
A
Gram +ve have thick peptidoglycan cell wall
Gram -ve have thin peptidoglycan cell wall + outer membrane
3
Q
Inhibit cell wall synthesis
A
- —– β lactams(Penicillin, Cephlosporin, Carbapenems)
- —– Glycopeptides (Vancoymycin, Teicoplanin)
4
Q
Examples of βlactams
A
Penicillin ---- Benzylpenicillin Cephalosporin ---- 3rd gen: Ceftriaxone, Cefotaxime, Ceftrazidime ---- 2nd gen: Cefuroxime ---- 1st gen: Cephalexin Carbapenams ---- Meropenam
5
Q
MOA of β lactams
A
Bind to penicillin-binding proteins –> ↓cell wall cross links –> weaker membrane –> lysed
6
Q
Risk of cross-reactivity between βlactams
A
10%
7
Q
Co-amoxiclav
A
Amoxicillin + Clavulanic acid
8
Q
Tazocin =
A
Piperacillin (β lactam) + Tazobactam (β lactamase inhibitor)
9
Q
With ↑generation of cephalosporin
A
↑Gram -ve cover, ↓Gram +ve cover
10
Q
Why is Cef (cephalosporin) often given with Metronidazole
A
Met provides anerobe cover
11
Q
ESBL stands for
A
Extended spectrum β-lactams
12
Q
ESBL Tx
A
Carbapenam-sensitive
Resistant to Penicillin and Cephalosporins)
13
Q
Carbapenemase
A
Resistant to Pencillin, Cephalosporin and Carbapenem
14
Q
Inhibit protein synthesis
A
Inhibit protein synthesis (cATOM)
- —— Aminoglycosides (Gentamicin)
- —— Tetracycline (Doxycycline)
- —— Macrolide (Erythromycin)
- —— Chloramphenicol
- —— Oxazolidinones (Linezolid)
15
Q
Example of Glycopeptides
A
Vancomycin, Teicoplanin
16
Q
MOA of Glycopeptides
A
Bind to enzymatic target (peptidoglycan precursors) –> weakened cell wall –> lyse
Similar MOA in β lactams bt bind to substrate (precursors)
17
Q
Nephrotoxic ABx
A
Gentamicin, Amikacin (aminoglycosides)
18
Q
Example of Aminoglycoside
A
Gentamicin, Amikacin, Tobramycin
19
Q
MOA of Aminoglycosides
A
Aminoglycoside binds to 30S ribosomal subunit to prevent causing misreading of dcodons along the mRNA–> inhibits protein synthesis
20
Q
Example of Tetracycline
A
Doxycycline
21
Q
MOA of Tetracycline
A
Binds to 30S ribosomal subunit to prevent aminoacyl-tRNA binding –> inhibits protein synthesis
22
Q
Example of Macrolide
A
Azithromycin, Clarithromycin
23
Q
MOA of Macrolide
A
Binds to 50S ribsomal subunit –> prevents binding of peptidyl-tRNA
24
Q
MOA of Chloramphenicol
A
Binds to 50S ribsomal subunit –> Prevents formation of peptide bonds
25
Example of Oxazolidinone
Linezolid
26
Inhibit DNA synthesis
Inhibit DNA synthesis
- ------ Fluoquinolone (Ciprofloxacin)
- ------ Nitroimidazoles (Metronidazole)
27
MOA of Oxazolidinone
Binds to 23S component of 50S subunit to prevent formation of functional 70S initial complex
28
Example of Quinolone
Ciprofloxacin
29
MOA of Fluroquinolone
Bind to DNA gyrase --> inhibit DNA synthesis
30
Example of Nitroimidazole
Metronidazole, Nitrofurantoin (related)
31
MOA of Nitroimidazole
Under anerobic conditions, active intermediated is produced which causes DNA strand breakage
32
Inhibit RNA synthesis
Inhibit RNA synthesis
| ------- Rifamycin (Rifampacin)
33
Example of Rifamycin
Rifampicin
34
MOA of Rifampicin
Binds to RNA polymerase --> inhibits initiation --> Inhibits RNA synthesis
S/E organse secretions, Liver enzyme inducer
35
Cell membrane toxin
Cell membrane toxin
- ------ Polymyxin (Colostin)
- ------ Cyclic lipopeptide (Daptomycin)
36
Examples of cell membrane toxins + MOA
Daptomycin - inserts into cell membranes --> leak ions
| Colistin --> unknown
37
Inhibit folate metabolism
Inhibit folate metabolism
- ------ Sulfonamide (Sulphamethoxazole)
- ------ Diaminopyramidines (Trimethoprim)
38
Example of Sulfonamide + MOA
Sulphmethoxazole --> interferes with folate metabolism
39
Example of Diaminopyrimidine + MOA
Trimethoprim --> interferes with folate metabolism
40
Co-trimoxazole =
Sulphamethoxazole + Trimethoprim
41
Mechanisms of ABx resistance
BEAT drug action
- Bypass ABx sensitive step in pathway (Trimethoprim)
- Enzymatic drug inactivation (β lactamase)
- ↓ Accumulation of drug (Tetracycline resistance) - ↓ uptake or efflux
- change drug Target (MRSA, Quinolone resistance)
42
β-lactamases - types, act against
Breaks down β lactams
- β-lactamase (against Penicillin)
- ESBL (against cephalosporins)
- AmpC (against cephalosporins, not inhibited by Clavulanic acid)
- Carbapenemase (against all β lactams)
43
MRSA - resistance mechanism
Altered target (mecA gene encodes novel PBP called PBP-2a)
44
Abx for ESBL
β-lactam + Aminglyocoside (Gentamicin, Amikasin)
45
ABx for MRSA
Vancomycin (or Linezolid)
46
Abx for C diff
Metronidazole (or Vancomycin)
47
Abx for Chlamydia
Doxycycline
48
ABx for bacterial conjunctivitis
Chloramphenicol
49
ABx for VRE
Linezolid
| Daptomycin
50
Cover for anerobes
Metronidazole
51
ABx fo PCP
Co-trimoxazole = Trimethoprim + Sulphamethoxazole
52
ABx for UTI
Trimethoprim or Nitrofurantoin
53
ABx for Hospital UTI
Augmentin (or Cephalexin)
54
ABx for pseudomonas
Gentamicin, or Tazocin
55
Main ABx for S aureus
Flucluoxacillin
56
Main ABx for Skin infections
Flucluoxacillin +/- Vancomycin (if MRSA)
57
Main ABx for meningitis
Ceftriaxone +/- Amoxicillin (listeria cover)
58
ABx for pharyngitis
Benzylpenicillin (cover Group A strep)
59
ABx for CAP (mild)
Amoxicillin (cover Strep pneumoniae + Hib)
60
ABx for CAP (severe)
Co-amoxiclav + Clarithromycin
61
ABx for HAP
Amoxicillin + Gentamicin OR Tazocin
62
Abx for E. coli
Gentamicin
63
Define minimum inhibitory concentration
Least amount of drug required to inhibit growth of organism in culture
Assessed using agara disc diffusion (calculate from boundary of growing + inhibited growth)
64
Empirical ABx therapy
Use BSABx which is likely to cover the likely organisms
| Then change based on culture sults to ↑ specific/narrow agent
65
Pharmacokinetic/Pharmacodynamic ideal for Gentamicin
Peak above MIC (Cmax)
66
Pharmacokinetic/Pharmacodynamic ideal for Penicillin
Time above MIC
67
Causes of secretory diarrhoea (profuse, watery diarrhoea)
```
Vibrio cholera
E coli (ETEC, ERPC, EHEC)
```
68
Causes of inflammatory diarrhoea (neutrophil in stools)
Campylobacter
Shigella
Salmonella (non-typhoidal)
EIEC
69
Causes of enteric fever (lymphocytes in stool)
Salmonella (typhoidal)
Yersinia spp
Brucella
70
Staphylococcus aureus
Aetiology: Pre-formed enterotoxin (exotoxin) --> superAg in GIT
Sx: Diarrhoea (non-bloody) and Vomiting
<6 hr incubation
Micro: Catalase +ve, Coagulase +ve, Gram +ve coccus, Clusters/Clonies, Protein A, β haemolytic on blood agar
Self-limiting
71
Bacillus cereus
```
Reheated rice --> spre germinate
Microscopy: spore-forming Gram +ve rod
Aetiology: Heat stable emetic toxin (remains after heating) + Heat labile diarrhoeal toxin (can be destroyed by heating)
Sx: Watery diarrhoea (non-bloody)
<6hr incubation
Self-limiting
```
72
Clostridia botulinum
Gram +ve anaerobe
Canned/Vacuum packed food
Preformed toxin INACTIVATED by cooking (blocks Ach release from nerves)
Tx: Antitoxin
73
Clostrdia perfringens
Gram +ve anaerobe
Reheated meat
Watery diarrhoea +/- Vomiting (24 hours)
Incubation 8-16 hours
74
Clostridia difficile
```
Gram +ve anaerobe
2 toxins (A, B)
Associated with ABx
Ix: Pseudomembranous colitis
Tx:
(1) Metronidazole, Infection control
(2) Vancomycin
```
75
Listeria monocytogenes
Outbreaks of febrile gastroneteritis
Refrigerated food, Unpasteruised diary, Vegetables
Microscopy: β-haemolytic, aesculin +ve, tumbling motility
Sx: Watery diarrhoea, Fever, Vomiting
Tx: Ampicillin or Ceftriaxone
76
Types of E coli
```
Diarrhoea +/- bloody (if haemorrhagic form)
Faecal-ortal route
Self limiting
- ETEC
- EIEC
- EHEC
- EPEC
```
77
ETEC
Toxigenic --> traveller's diarrhoea
78
EIEC
Invasive dysentery
79
EHEC
Haemorrhage (shiga-like verocytotoxin) (Haemorrhagic 0157)
80
EPEC
Infantile diarrhoea (Paeds)
81
Salmonella typhi / paratyphi (enteric fever)
```
Constipation (slow onset)
Rose spots
Splenomegaly
Anaemia, Leukopenia
Fever
Blood culture +ve
Multiples in Peyer's patches
Tx: Ceftriaxone
```
82
Salmonella enteritidis
Poultry, Eggs, Meat
Diarrhoea (non-bloody)
Self-limiting
83
Shigella
Shiga toxin --> affects distal ileum/colon
Fever
Bloody diarrhoea
Tx: avoid ABx
84
Vibrio cholerae
Rice water stool (with no inflammatory cells)
Enterotoxin A and B
Water contaminated with huan faeces
Tx: supportive
85
Vibrio parahaemolyticus
Raw undercooked seafood (in Japan)
Diarrhoea
Self-limiting
Tx: Doxycycline
86
Vibrio vulnificus
Water-bourne organism
Shellfish handler / Scuba diver
Fetal sepsis with D&V in HIV patients
Tx: Doxycycline
87
Campylobacter jejuni
```
Upasteurised milk, poultry
Prodrome of headache + fever
Bloody diarrhoea (foul smelling)
Cx
- GBS
- Reactive arthritis
Tx: Erythromycin
```
88
Yersinia enterocolitis
```
Food contaminated with animal faeces
Prefers cold environment (4o)
Enterocolitis
Mesenteric adenitis
Cx
- Reactive arthritis
- Erythema nodosum
```
89
Mycobacteria
HIV patients
| Diarrhoea
90
Entamoeba histolytica
```
Mobile trophozoite found in diarrhoea
MSM
Food, water, soil
Non-motile cyst in non-diarrhoea illness
Histology: flask shaped ulcer
Dysentery
Flatuence
Tenesmus
Chronic weight loss
Liver abscess
Tx: Metronidazole
```
91
Giardia lamblia
Pear shaped trophozoite
Traveller / Hiker / MSM / Mental hospital
Ingesting cysts from faceally contaminated water
Non-bloody diarrhoea (foul smelling)
Flatulence
ELISA string test: string attached to ingested capules --> fished out
Tx: Metronidazole
92
Cryptosporidium parvum
Swimming
Oocysts seen in stool by modified Kinyoun acid fast stain
Severe diarrhoea in immunocompromised
93
Norovirus
Outbreaks
D&V
Cruse ships
94
Rotavirus
< 6 years old
95
Adenovirus
Type 40+41 --> non-blood diarrhoea
< 2 year olds
Immunocompromised
96
DDx Bloody diarrhoea
Shigella
Campylobacter
E coli
97
Hepatitis A transmission
Faecal-oral route (infected water)
| RNA virus
98
Hepatitis A Serology
Anti-HAV IgM = recent infection
| Anti-HAV = previous infection or vaccine
99
Hepatitis A disease course
↑ ALT, ↑ IgM
| Later, ↑ IgG
100
Hepatitis A - Tx
Supportive only
101
Hepatitis B - route of infection
dsDNA virus
Sexual
Vertical
Blood / needlestick
102
Hepatitis B - Ix
↑ ↑ ALT, ↑ AST
HBsAG (infection or vaccine)
HbcAb (acute IgM, chronic IgG)
103
Hepatitis B - Tx
PegIFN- α2a (direct anti-viral effect, upregulates MHC)
Tenofovir (RT inhibitor)
Lamivudine (inhibits viral polymerase)
Entecavir (inhibits viral polymerase)
104
Hepatitis C - route of infection
RNA virus
| Blood products
105
Hepatitis C - Ix
ALT
| Anti-HCV
106
Hepatitis C - Tx
PEG-IFN- α2b
| Ribavirin
107
Hepatitis D
Only infect Hepatitis B +ve patients
| Ix: IgM anti-HDV
108
Hepatitis E
RNA virus
Faecal-oral transmission
India
Tx: Supportive
109
Complications of Hepatitis B / C
Hepatitis --> Fibrosis --> Cirrhosis --> Cancer
↑ risk of Hepatocellular carcinoma
Liver transplant
110
uncomplicated vs complicated UTI
Complicated UTI has functional or structural abnormality (including: male, pregnancy, children, hospitalised)
111
Most common cause of UTI
E coli
112
Non E coli organisms causing UTI
```
Proteus mirabilis
Klebsiella aerogenes
Enterococcus faecalis
Staphylococcus saprophyticus - only non-E-coli organism causing UTI in normal urinary stem
Staphylococcus epidermis
```
113
Routes of UTI
Ascending UTI or Haematogenous route (bacteraemia, endocarditis)
114
+ve nitrite indicates
Likely UTI
115
-ve nitrite AND +ve leukocyte
Urine culture
| Treat if symptomatic
116
Nitrites are specific for
Coliform bacteria (have a reducing enzyme converting nitrates --> nitrites)
117
Urine leucocytes indicate
Inflammation
118
Definition of UTI
> 10,000 CFU / ml + urinary symptoms
119
DDx sterile pyruia
Chlamydia, TB
120
Urine microscopy showing squamous cells
Perineal contamination
121
Treatment of UTI
Trimethoprim or Nitrofurantoin
122
Treatment of Pyelonephritis
Co-amoxiclav +/- Aminoglycoside (Gentamicin)
123
Tx of complicated UTI (pregnancy, male)
Cefalexin or Co-amoxiclav
124
Candida UTI is associated with
Indwelling catheter
| Tx: removal will cure
125
CSF: ↑ WBC polymorphs, ↑↑ protein, ↓ glucose, turbid CSF
Bacterial meningitis
126
CSF: ↑ WBC lmphocytes, ↑/ protein, glucose
Viral meningitis
127
CSF: ↑ WBC lymphocytes, ↑↑ Protein, ↓ Glucose
TB meningitis
128
Meningitis, Gram +ve diplococci, α-haemolysis
Streptococcus pneumoniae
129
Meningitis, Gram -ve diplococci
Neisseria meningitidis
130
Meningitis, Gram +ve rods
Listera monocytogenes
131
India ink stain, MSM
Cryptococcus
132
Meningitis organisms
Neisseria meningitidis (Gram -ve diplococci)
Streptococcus pneumoniae (Gram +ve diplococci)
In neonates
---- GBS
---- Listeria
---- E coli
TB
Viral: Coxsackie, Mumps, HSV2
Fungal: cryptococcus
133
Tx for meningitis
IV Ceftriaxone
134
Tx for encephalitis
IV Aciclovir
135
Define Hospital acquired infection
infection > 48 hr of admission, 3 days discharge of 30 days of surgery, not present on admission
136
How common are HAI?
8%
137
Most common HAI
Hospital-acquired pneumonia
138
C. difficile - Gram, RF, Ix, Tx
Gram +ve, spore-forming anerobe
Risk factors: ABx
Ix: Pseudomembranous colitis
Tx: Metronidazole
139
E. coli - Gram
Gram -ve rod
| Resistant to β-lactamases
140
Surgical site infection organisms
MRSA
| Coagulase -ve Staphylococcus
141
Water-associated organisms
Legionella
Pseudomonas
Mycobacteria
142
Most common pathogens involved in surgical site infections
S aureus (MSSA, MRSA)
Less common
- E coli
- Pseudomonas
143
Tx for surgical site infection
Flucluoxacillin
144
Septic arthritis - organisms
Staph aureus (46%)
Streptococci (22%)
Less common: E coli
145
Septic arthritis - Sx
Fever
Red, hot, swollen joint
Unable to weight bear
146
Septic arthritis risk factors
RhA | OA | IVDU | DM | Immunosupression | Trauma
| S aureus strain --> produces Panton-Valentine Leucocidin (PVL)
147
Septic arthritis - Ix
Blood culture
Joint aspirate > 50,000 WBC/mm3
ESR, CRP
Imaging: effusion
148
Osteomyelitis organisms
```
S aureus (48%)
Less common: Gram -ve rods, Streptococcus
```
149
Osteomyelitis - Ix for diagnosis
MRI - best imaging
| Bone biopsy for culture/histology
150
Osteomyelitis
ABx +/- debridement
151
Prosthetic joint infection - organisms
Coagulase -ve Staph = Staphylococcus epidermidis ( > Staph aureus)
Streptococci spp.
Enterococci spp
152
Prosthetic joint infection - Sx
Pain
Joint was 'never right' since operation
Early failure of jiont
153
Prosthetic joint infection - Ix
X-ray: "Loosening"
| Joint aspirate
154
Prosthetic joint infection - Tx
Remove metalwork
| Joint replacement
155
Classical causes of Pneumonia
```
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Staphylococcus aureus
Klebsiella pneumoniae
```
156
Most common cause of CAP
Streptococcus pneumoniae
157
Streptococcus pneumoniae
Gram +ve diplococci (α haemolysis)
Rusty coloured sputum
Lobar pneumonia
158
Haemophilus influenzae
Gram -ve cocco-bacilli
Smoking
Pre-existing lung disaese (e.g. COPD)
Chocolate agar plate
159
Moraxella catarrhalis
Gram -ve coccus
| Smoking
160
Staphylococcus aureus
Gram +ve cocci - "grape-bunch clusters"
Recent viral infection
CXR: cavitation
161
Klebsiella pneumoniae
Gram -ve rod (enterobacter)
Alcoholics
Elderly
Haemoptysis
162
Classical vs Atypical pneumonia - presentation
Classical - signs on chest exam + CXR
Atypical has NO signs on chest exam and normal CXR +/- extrapulmonary features (e.g. ↓ Na+) + do not respond to β lactams
163
Causes of atypical pneumonia
```
Legionella pneumophila
Mycoplasma pneumonia
Chlamydia pneumonia
Coxiella burnetii (Q fever)
Chlamydia psittaci (Psittacosis)
Bordatella pertussis
TB
```
164
Legionella pneumophila
```
Water (air conditioning) / Travel
Hyponatraemia
Hepatitis
↓ WBC
Confusion
Diarrhoea
Ix: Urinary legionella antigens
Charcoal agar
```
165
Mycoplasma pneumonia
```
Epidemics (every 5 years)
Cold agglutinin test
Erythema multiforme
Risk of SJS
Autoimmune haemolytic anaemia
Joint pain
```
166
Chlamydia pneumonia
#NAME?
167
Coxiella burnetii (Q fever)
Farm animal: Goat / Sheep / Cattle --> aerollised / infected milk
168
Chlamydia psittaci (Psittacosis)
Birds
169
Bordatella pertussis
Whooping cough
| Unvaccinated (travelling community)
170
TB
Poor response to ABx
Auramine-Rhodamine stain
Ziehl-Neelson stain
171
Ix for pneumonia
```
CURB-65 score > 2 warrants admission
Confusion
Urea > 7
RR > 30
BP < 90
Age > 65 years old
```
172
Bronchitis vs Pneumonia
```
Bronchitis = inflammation of medium sized airways
Pneumonia = inflammation of alveoli
```
173
Bronchitis - organisms
Viruses
Streptococcus pneumoniae
H. influenzae
Moraxella catarrhalis
174
Bronchitis - Tx
Bronchodilation, Physiotherapy
175
Causes of cavitation on CXR
Staphylococcus aureus
Klebsiella pneumoniae
TB
Haemophilius influenzae
176
Hospital acquired pneumoniae organisms
```
Gram -ve
---- E coli
---- Klebsiella
---- Pseudomonas
Staph aureus
Fungi
Protozoa
---- Pneumocystis jirovecii
```
177
Pneumocystis jirovecii
```
Protozoan
Immunosupressed
Silver stain
Immunofluorescence
AIDS-defining illness
CXR: "bat's wing" or "bilateral ground glass shadowing"
Ix: Walkings sats test (definitive test for PCP)
Tx: Co-trimoxazole
```
178
Aspergillus fumigatus
```
MC+S: Hypae with flower heads
Allergic bronchopulmonary aspergillosis
--- Chronic wheeze
--- Eosinophilia
Aspergilloma
--- In pre-existing cavity
Invasive aspergillosis
--- Immunocompromised
```
179
HIV with LRTI
PCP, TB, atypical mycobacteria
180
Neutropenia with LRTI
Fungi (aspergillius)
181
Bone marrow transplant with LRTI
CMV
182
Splenectomy with LRTI
Encapsulated organisms (N meningitis, H influenzae, S pneumoniae)
183
Cystic fibrosis with LRTI
Pseudomonas aeruginosa, Burkholderia cepacia
184
Tx for CAP (mild)
Amoxicillin OR Macrolide (Clarithromycin / Erythromycin)
185
Tx for CAP (severe)
Co-amoxiclav AND Macrolide (Clarithromycin)
186
Tx for atypical pnemonia
Macrolide
187
Tx for HAP
Ciprofloxacin +/- Vancomycin
188
Tx for MRSA
Vancomycin
189
Tx for pseudomonas
Tazocin OR Ciprofloxacin +/- Gentamicin
190
Tx for aspiration pneumonia
Cefuroxime + Metronidazole (need Gram +ve, -ve and anaerobic cover)
191
Tx for Legionella
Macrolide + Rifampicin
192
Tx for S aureus
Flucloxacillin
193
Slow growing mycobacteria
```
MTB complex
---- M bovis (cows, BCG vaccine)
---- M tuberculosis
---- M africanum (West Africa)
---- M marinum (swimming pool granuloma), aquarium owners, plaques/papules
---- M ulcerans (chronic painless ulcer)
M avium complex
---- M avium
---- M avium intracellulare (invades bronchial tree in those with prexisting lung disease, children with pharyngitis)
```
194
Rapidly growing mycobacteria
M abscessus complex --> skin/soft tissue infection
195
Ungrouped mycobacteria
M leprae --> Leprosy (spectrum from few skin lesion to multiple skin lesions with profound disfigurement and nerve damage)
- Depigmentation, Macules, Plaques, Nodules, Ulcers
- Sensory neuropathy
- Keratitis
- Periositis aseptic necrosis
196
Stain for mycobacteria
Acid fast bacilli
Auramine-Rhodamine stain: fluorescent AFBs
Ziehl-Neelsen stain
197
Non-TB bacteria commonly found in
Water and Soil (in nature)
| No person to person transmission
198
Vaccination against TB
Bacille Calmette-Guerin (BCG) = live attenuated M. bovis strain
199
TB is associated with
```
Erythema nodosum
Pulmonary TB: Caseating granuloma
Lymphadenitis (scrofula)
GI TB
Peritoneal TB (ascites)
GU TB (sterile pyruia)
Spinal TB = Pott's disease (+/- Iliopsoas abscess)
Meningeal TB
Miliary TB (millet seeds on CXR)
```
200
Histology of TB
Caseating granuloma
201
Culture for TB
Lowenstein-Jense (LJ) medium (gold standard)
202
Ix for speciation / drug resistance of TB
NAAT / PCR
203
Tuberculin skin test +ve
Latent TB, Active TB or Vaccination
204
IGRA = interferon γ release assay = ELISpot = Quantiferon
+ve in Latent TB and aactive TB
205
S/E of TB treatment
Rifampicin - orange secretions, liver enzyme inducer
Isoniazid - peripheral neuropathy (Tx: Vitamin B6 / Pyridoxine)
Pyrazinamide - Hepatotoxic
Ethambutol - loss of colour vision, optic neuritis
Risk of immune reconstitution inflammatory syndrome (IRIS) in HIV patients
206
% of world infected with TB
30%
207
Risk of reactivation of latnet TB
10% lifetime risk
| If HIV +ve --> this increases to 10% yearly risk
208
Road to pandemic
Acquire mutations to break down species barrier / cross-over into humans
---- PB2 switch
---- Reassortment = ANTIGENIC SHIFT (co-infection between Bird flu and human flu --> viral proteins recombine --> allow infection of humans)
---- ANTIGENIC DRIFT = mutation in HA/NA to give new strains
Survive longer in environment (remain airbounr in mildly acidic resp droplets
Overcome barriers to infection (physical, chemical, receptor)
209
Natural reservoir for Influenza A
Ducks
210
Respiratory tropism is the result of
Influenza virus requires activation by host cell proteases only expressed in respiratory tract
211
Infection by influenza
Attachment to sialic acid cell surface receptor --> endosome --> release viral DNA
HA must be cleaved for viral fusion to occur (airway tryptase only found in the lung)
Viral DNA to nucleus --> mRNA synthesis --> viral proteins --> virus buds off
212
Most common cause of death from pandemics
Cytokine storm (hypercytokinaemia) --> acute respiratory distress syndrome --> pulmonary oedema --> death
213
Influenza virus - number of genetic segments
8 RNA segments
Encodes for
- Neuraminidase (NA): cleaves sialic acid residues --> exposures receptors on host cell, disrupts mucus barrier
- Haemogglutinin (HA): binds sialic acid receptors --> viral entry (named for causing agglutination fo RBCs)
214
Anti-virals for Influenza
Amantadine: targets M2 ion channel, most viruses already resistant
Oseltamavir (Tamiflu): neuraminidase inhibitor
Zanamivir (Relenxa)
(Favipiravir, Baloxavir): polymerase inhibitors [NEW]
Sialic acid
215
Recent change in vaccination strategy since 2009 pandemic
Vaccinate children (intranasal flu vaccine) with live attenuated virus
Vaccinate healthcare works
Vaccinate elderly
216
Link between Pandemic and Seasonal flu
Pandemics may drift and transform into seasonal influenza
217
3 seasonal flus
```
Influenza A (H1) - peaks in Jan
Influenza A (H1N1) - peaks in Dec
Influenza B (peaks in March)
```
218
Most common cause of meningococcal disease in the UK
MenB
| MenC / Hib / Pneumococcus now rare as vaccainated against
219
TORCH screen
```
Toxoplasmosis
Other - Syphilis, HIV, Hepatitis B/C
Rubella
CMV
Herpes
```
220
TORCH infection - Sx
```
Thrombocytopaenia
Other (cataracts, choroidoretinitis)
Rash
Cerebral abnormality (microcephaly)
Hepatosplenomegaly
```
221
Toxmoplasmosis
```
Cats --> Mice/Birds
Cat litter
Asympatomatic at birth (60%)
40% symptomatic
- Choroidoretinitis
- Microcephaly
Long term: deafness, ↓ IQ
```
222
Congenital Rubella syndrome
Only risk if < 20 weeks' gestation
| Triad of cataracts, sensorineural deafness, congenital heart defects
223
HSV
Lies in mother's genital tracts
| Congenital HSV - blistering rash, disseminated HSV, meningoencephalitis
224
Early vs Late onset neonatal infection =
Early < 48 hours since birth
| Late > 48 hours since birth
225
Group B strep
Gram +ve coccus
Catalase -ve
β-haemolytic
226
E coli
Gram -ve rod
227
Listeria monocytogenes
Gram +ve rod
228
Risk factors for early onset neonatal sepsis
PROM | PPROM | Chorioamniotis | Meconium staining | Acidosis | Hypoglycaemia | Jaundice
229
Early onset neonatal sepsis - organisms
GBS - most common
E coli
Listeria monocytogenes
230
Early onset neonatal sepsis - Tx
benzylpenicillin (covers GBS + Listeria) + Gentamicin (covers E coli)
231
Late onset neonatal sepsis - organisms
Coagulase -ve Staphylococci
GBS | E coli | Listeria
S aureus
Gram -ve (Klebsiella, Enterobactera | Pseudomonas)
232
Late onset neonatal sepsis - Tx
Cefotaxime + Vancomycin
233
Neisseria meningitidis
Gram -ve diplococci
234
Streptococcus pneumoniae
Gram +ve diplococus, α-haemolytic, optochin sensitive
235
Haemophlius influenzae
Gram -ve rod, Chocolate agar (grows on haemolysed blood)/
236
Meningitis organisms based on age
< 3 months: GBS, E coli, Listeria, N meningitis, S pneumoniae, Hib if unvaccinated
> 3 months: N meningitis, S pneumoniae, Hib if unvaccinated
> 6 years: N meningitis, S pneumoniae
237
Respiratory infection organisms in children
Viruses
Then, S pneumoniae
Then, Mycoplasma (>4yr)
238
Ix for ? Rubella infection in mothers
```
Look for evidence of seroconveresion
Rubella IgM as marker of infection
PCR - gold standard (respiratory seretions, blood, urine)
Tx: < 20 weeks --> TOP
No documented risk > 20 weeks' gestation
```
239
Congenital CMV - Ix
Prenatal Ix: amniocentesis
PCR, cell culture, DEAFF (cell culture), Serology (IgM, IgG)
Post-natal: urine + saliva swabs (CMV is shed in urine and saliva)
240
Congenital CMV - Tx
Valganciclovir or Ganciclovir
241
Congenital CMV - SX
90% asympatomatic at birth (10% will become symptomatic)
| 10% symptomatic at birth - hearing loss, microcephaly, choroidoretinitis, jaundice
242
HSV infection has highest risk when
In 6 weeks before EDD ∴C-section is recommended
243
Congenital HSV infection - Sx
Skin, Eye, Mouth disease - scarring, hypopigmentation
CNS disease - microcephaly
Disseminated infection
244
Congenital HSV - Tx
IV Aciclovir
245
VZV in early gestation cause
Congenital varicella syndrome
246
VZV in late gestation lcauses
Neonatal varicella syndrome
247
Tx for VZV exposure
VZIG within 10 days of exposure
| Aciclovir if > 10 days post-exposure
248
Measles infection in pregnancy
↑ risk of miscarriage
| No congenital measles syndrome
249
Parvovirus in pregnancy - Sx
```
Slapped cheek syndrome
Aplastic crisis
Hydrops foetalis
Tx: intrauterine transfusion
No risk > 20 weeks gestation
```
250
Congenital Zika syndrome
Microcephaly
Seizures
Retinopathy, Deafness
251
Tx for HSV and VZV
(1) Aciclovir
(2) Valaciclovir (prodrug of AC)
(3) Famciclovir
Act Very Fast!
(2nd line) = Foscarnet or Cidofovir
252
MOA of Aciclovir
Guanosine analogue --> activated by viral thymidine kinase --> ACP-PPP --> binds to viral DNA polymerase
253
CMV - Histology
Owl's eye inclusions
254
CMV - Sx
Bone marrow suppression
Retinitis
Pneumonitis
255
CMV - Tx
(1) Ganciclovir
(2) Foscarnet
(3) Cidofovir
Different as CMV does not have same enzymes
256
MOA of Gancliclovir
Requires activation by viral UL97 kinase
Inhibits viral DNA synthesis
S/E: BM supression
257
MOA of Foscarnet
Non-competitive inhibitor of viral DNA polymerase (does not require activation)
258
MOA of Cidofovir
Nucleoside analogue -> competitive inhibitor of viral DNA synthesis
259
MOA of Miribavir
Inhibits viral kinase
260
MOA of Letermovir
CMV DNA terminase inhibitor
261
EBV infects
B cells (lifelong low grade viral replcication)
262
EBV is associated with
Post-transplant lymphoproliferative disease --> classical HL, Burkitt's lymphoma
- Latently infected B cells --> polyclonal activation
Tx: ↓ immunosuppression, Rituximab (Anti-CD20 Ab)"
263
Tx for Bronchiolitis (RSV)
Ribavirn (Guanosine analogue --> inhibit viral RNA synthesis)
IVIG
264
Prophylaxis for Bronchiolitis (RSV)
Palivizumab (mAb against RSV)
265
BK virus - Sx
Only sympatomtic in immunocompromised
- In bone marrow transplant --> Haemorrhagic cystitis (Tx: Cidofovir)
- In renal transplant --> BK nephritis (Tx: IVIG)
266
Most common cause of HSV drug resistance to ACV
Mutation in viral thymidine kinase
| Tx: Foscarnet
267
Most common cause of CMV drug resistance to GCV
Mutation in protein kinase gene (UL97)
| Tx: Foscarnet
268
Indications for treating chickenpox
Immunocompromised, Pregnant, Adults with pneumonitis
269
Basic reproductive rate (R0)
Average number of individuals infected by infectious case during their infectious period
If R0 < 1 --> transmission is stopped
270
Herd immunity threshold (HIT)
= 1 - (1/R0)
| Percentage required to stop the spread of disease
271
Inactivated vaccine
Pathogen destroyed by heat, chemicals, radiation or ABx
Unable to cause infection
e.g. Influenza, Polio
272
Attenuated vaccine
Live organisms grow in un-natural host --> less virulent
Risk of reversion to virulence
Contraindicated in pregnancy and immunosuppressed patients
e.g. MMR
273
Toxoid vaccines
Inactivated toxic component
| e.g. Tetanus, Diphtheria
274
Subunit vaccine
Protein component of pathogen
| e.g. Hepatitis B, HPV
275
Conjugate vaccine
Poorly immunogenic antigen with adjuvant
| e.g. Hib
276
Heterotypic vaccines
Pathogens that infect other animals but only cause mild disease in humans
e.g. BCG
277
Contraindications for influenza vaccine
Anaphylactic hypersensitivity to egg
278
Contraindications for MMR
Immunocompromised, Pregnant, Anaphylactic reaction to egg
279
HIV fusion inhibitor
Enfuvirtide
280
CCR5 co-receptor antagonist
Maraviroc
281
NRTI
Zidovudine, Tenofovir
282
NNRTI
Efavirenz
283
Integrase inhibitor
Raltegravir
284
Protease inhibitor
Ritonavir
285
Yeast vs Mould
Yeast = individual cells (divide by budding from one another)
---- Candida
---- Cryptococcus
Mould = filamentous fungi
---- Aspergillus
---- Dermatophytes
N.B. Dimorphism (yest during infection, mould in nature)
286
Fungal - superficial vs deep (definition, Ix)
Superficial (skin, hair, nails) vs Deep (systemic)
Ix for superficial - Woods Lamp for diagnosis (Tinea, Pityriasis)
Ix for deep - clinical Hx, Ix, Imaging for diagnosis (Candida, Aspergillus)
287
Types of Candida
Candida albicans
Candida glabrata - resistant to 1st line azoles
Candida krusei - resistant to 1st line azoles
Candida tropicalis
Candida dubliniensis
288
Candida microscopy
```
Discrete colonies
Germ tubes (indicates likely C albicans)
```
289
Candida culture
Chromogenic agar
MALDI-TOF technique
Sabouraud's dextrose agar
290
Candida - Ix
Microscopy
Blood cultures - candidaemia
Serology - β-D-Glucan assay
291
Candida - Tx
Echinocandin (anidulafungin) - covers C albicans + non-albicans
+/- Fluconazole - covers C albicans
292
Cryptococcus types
Cryptococcus neoformans
Cryptococcus gattii
Cryptococcus life cycle between Bird excrement and Eucalyptus trees
Often affects immunocompromised (esp HIV)
293
Cryptococcus - Ix
India Ink staining --> Halo appearance
---- capsule protects cryptotoccus from being stained black
Enzyme immunoassay for Cryptoccocal antigen (gold standard)
CXR: pulmonary cryptococcoma
294
Cryptococcus - Tx
Amphotericin B
295
Aspergillus - microscopy
Filaments
Hyphae
Spores
296
Aspergillus types
```
Aspergillus fumigatus
Aspergillus flavus
Aspergillus niger
Aspergillus nidulans
Aspergillus terreus
```
297
Aspergillus - Sx
Mycotoxicosis - ingestion
ABPA
Aspergilloma
Invasive aspergillosis
298
Aspergillus - risk factor
Building work
299
Aspergillus - Ix
Microscopy - mainstay of Dx
Culture
Galactomannan Ag
Aspergillus PCR
300
Aspergillus - Tx
Amphotericin
301
Dermatophtes
```
Tinea pedia
Tinea cruris (groin area)
Tinea corporis (ringworm)
Tinea capitis (scalp)
Onychomycosis
Pityriasis versicolour - discolouration of skin (malassezia furfur)
```
302
Mucormycosis - Sx + Tx
Black eschar (black pus)
Due to Rhizopus spp, Rhizomucar spp, Mucor spp
Tx: Surgical debridement + Amphotericin
303
Types of anti-fungals
```
Cell membrane anti-fungals
---- Azoles (Ketoconazole)
---- Polyene (Amphotericin B)
DNA synthesis anti-fungals
---- Flucytosine
Cell wall antifungals
---- Echinocandin (caspofungin)
```
304
MOA of Azoles
Affects cell membrane synthesis
Bind to lanosterol 14 α demethylase --> prevents conversion of lanosterol to ergosterol --> build up of toxic sterol --> cell death
305
MOA of Polyenes
Affects cell membrane integrity
| Forms transmembrane channels in fungal cell wall --> electrolyte leaks --> cell death
306
MOA of Flucytosine (DNA synthesis antifungal)
Inhibits DNA synthesis in fungal cells
307
MOA of Echinocandin (Caspofungin)
Affects cell WALL
| Inhibits β (1,3) D-glucan synthase --> loss of cell wall glucan --> osmotic fragility --> lysis
308
Pyrexia of unknown origin
Fever > 38.3 lasting > 3 weeks without diagnosis OR uncertain diagnosis after 7 days in hospital OR after sensible set of Ix
309
Durack and Street criteria for PUO
```
Classical PUO: PUO after > 3 days in hospital
- Infection
- Malignancy
- Connective tissue disorders
Healthcare-associated PUO: PUO after 24 hours in hospital
- Surgery
- Drugs
- Medical devices
- LRTI
Neutropenic PUO: Fever with neutropenia (medical emergency)
- Chemotherapy
- Haematology malignancy
HIV-associated PUO: HIV +ve patient with PUO
- Seroconversion
- TB
- Kaposi's sarcoma
```
310
Routine Ix for PUO
```
FBC, U&E, Protein, LFTs, CRP
HIV test
Blood culture x3
Urine culture
CXR
```
311
Criteria for bacterial endocarditis
Duke's criteria
312
Macrophage activation syndrome
Associated with systemic-onset juvenile idiopathic arthritis
Sx: Fever, hepatosplenomegaly, pancytopenia, ↑ IFN-γ, GM-CSF
↓ Hb, ↓ Plt, ↓ Neutrophils
313
DDx Fever with Rash
```
Dengue
Chikungunya
Rickettsial
Enteric fever (rose spots)
Measles
```
314
DDx Fever with haemorrhage
Viral haemorrhagic fever (Dengue)
| Meningococcaemia
315
DDx with Eosinophlia
Acute schistosomiasis, Drug hypersensitivity
316
DDx Fever with onset > 6 weeks after travel
Malarix vivax
Acute hepatitis
Amoebic liver abscess
317
Types of malaria
Protozoa, Anopheles mosquito
- P falciparum
- P vivax
- P ovale
- P malariae
- P knowlesi
318
Malaria Sx
```
Cyclical fever
Severe when parasitaemia > 2%
- Altered consciousness
- Metabolic acidosis
- Haemoglobinuria --> black water fever
- Anaemia
- Jaundice
- Coagulopathy
```
319
Malaria - Ix
Thick blood film --> screen for parasites
Thin blood film --> identification of species
---- Falciparum is typically headphone shaped (cresent shaped) and RBCs have >1 intracellular parasite
Giemsa stain
320
Malaria - Tx
Non-falciparum malaria --> Chloroquine, Primaquine (if G6PD normal)
Falciparum malaria
- Mild --> Atovaquone, Proguanil, Riamet (Artemisinin + Lumefantrine), Quinine
- Severe --> IV Artesunate
321
Dengue fever - Sx
Fever
Sunburn-appearing rash - blanching
Tourniquet test +ve (mark left where skin was squeezed)
Retro-orbital headache
322
Dengue fever - Ix
Dengue PCR
| Serology IgM +ve
323
Chikungunya virus
↑arthralgia (c.w. dengue)
324
Enteric fever = Typhoid fever
```
Salmonella typhi / paratyphi
High, prolonged fever
Rose spots
Constipation
Tx: IV Ceftriaxone + Azithromycin
```
325
Infectiuos mononucleosis
EBV or CMV
Fever
Tonsillitis
Ix: atypical lymphocytosis, monospot test
326
Campylobacter jejuni
Gram -ve rod
Chicken
Sx: Diarrhoea
Ix: Stool MC&S
327
Salmonella
Gram -ve rod
Chicken, contaminated food, poor hand hygiene
India
Salmonella typhi/paratyphi --> enteric fever (rose spots, constipation)
Other strains --> enteritis
328
Bartonella henselae
Gram -ve rod
Cat scratches
Cat scratch disease (immunocompetent) --> Macule, Fever, Night sweats,Weight loss
Bacilliary angiomatosis (immunocompromised) --> Skin papules, disseminated multi-organ involvement (hepatitis)
329
Toxoplasmosis
```
Toxoplasma gondii (parasiteº
Cats, Faecal contamination
Fever
Pregnant women --> fetal abnormalities
Immunocompromised --> CNS --> Seizures
```
330
Brucellosis
```
Gram -ve cocco-bacilli
Cattle, Unpasteurised milk
Fever, Sweats, Weight loss
Back pain,
Orchitis
```
331
Coxiella burnetii (Q fever)
Goats, Unpasteurised milk/Aerolisation
Atypical pneumonia
NO RASH
332
Rabies (LYSSA VIRUS)
```
Dogs, Cats, Bats
Bites, Scratches, Infected fluid
Fever
Headache
Salivation
Agitation
Negri bodies (pathognomonic)
```
333
Rat bite fever
```
Streptobacillus moniliformis (Gram -ve rod)
Spirillum minus (Gram -ve rod)
Fever
Polyarthralgia
Maculopapular rash
```
334
Hantavirus pulmonary syndrome
Deer mouse - Sin Nombre virus
Infected urine/droppings
Acute respiratory distress syndrome
335
Viral haemorrhagic fever
```
Includes
- Ebola (bats)
- Marburg (bats)
- Lassa (rats)
- CCHF (Ticks)
Thrombocytopaenia --> bleeding
Fever
```
336
sCJD - Ix
Brain biopsy
337
vCJD - Ix
MRI: Pulvinar sign
| Tonsillar biopsy - only done for vCJG (NOT for sCJD)
338
CJD - Tx
Symptomatic only
- Clonazepam - for myoclonus
- Quinacrine (anti-malarial) - delay prion conversion
- Pentosan
- Tetracycline
- Anti-prion Ab
339
vCJD vs sCJD
vCJD has younger age of onset + Psychiatry symptoms first (before neuro Sx)
340
Sx of CJD
```
Rapid progress dementia
Myoclonus
Cortical blindness
Akinetic mutism
LMN signs
```
341
Sx of Kuru
Progressive cerebellar syndrome
342
Sx of GSS
Dysarthria --> Cerebellar ataxia --> Dementia
343
Sx of FFI
Insomnia --> Hallucinations
344
Epidermodysplasia verruciformis
EVER1/2 mutation --> ↑ risk of HPV infection
345
AIDS defining conditions
```
Oesophageal candidiasis
Cervical cancer (invasive)
CMV retinitis
Kaposi sarcoma (HHV8)
Burkitt's lymhoma
PCP
PML (JC virus)
```
346
HIGH to LOW risk of opportunistic viral infections
```
Allogenic stem cell transplant
Advanced HIV
Solid organ transplant
monoclonal antibody therapy
Cytotoxic chemotherapy
Steroids
```
347
Progressive multifocal leukoencephalopathy
JC virus
Demyelination of white matter tracts
Focal neurological signs
Cognitive disturbance
348
BK virus - Sx
Post-stem cell transplant --> BK cystitis
Post-renal transplant --> BK nephropathy
Tx: Cidofovir
349
Types of helminths
```
Cestodes = tapeworms
Trematodes = Flukes = no body cavity, gut
Nematodes = Roundworms = earthworm-like, body tubes ends in anus
```
350
Pork tapeworm
Taenia solium
- Eggs seen in faeces
- Risk of cystericerosis (headache, seizures, confusion, major changes)
- ------ Faecal-oral transmission, not from uncooked meat
351
Beef tapeworm
Taenia sagina
| - Segments fall out of rectum
352
Poor and Beef tapeworm - Sx
Onset after 2-3 months
D&V
White rice grains in stools
353
Hyatid lifecycle
Normally Dog Sheep
Humans eat dogshit contaminated food
Tx: praziquantel +/- aspiration of cysts
354
Schistosomiasis types
```
S mansoni (Africa, S America) --> GI
S haematoium (Africa) --> Bladder (haematuria)
S mekongi
S japonicum (China, Philippines) --> GI
```
355
Schistosomiasis life cycle
Contaminated freshwater
Snails
Release into water
Infect through skin --> bladder or GI tract
Ix: Stool/urine microscopy (look fro eggs), Biopsy (bladder, rectum) granulomatous lesions with eggs
Tx: Praziquantel
356
Ascaris
Contaminated soil
357
Strongyloides
Contaminated mud --> foot --> lungs --> cough and swallowed --> SI --> eggs --> perianal skin
Walking barefoot
358
Filariasis
```
Blackflies vector
Lymphatics --> elephantiasis
SC tissues
Serous cavity
USS: Dance sign
```
359
Myiasis
```
Bot fly OR Tumbu fly
Non-healing skin lesion
Itchiness
Discharge from central punctum
Fly larve lies in skin and bursts out and flies away
NOT a worm
```
360
Most common cause of adult-onset seizures
Cystericerosis
361
Mechanism of cysticerosis
Contaminated pork eaten by Human 1 (asympatomatic, GI tapeworm, eggs excrete in faeces)
Faecal-oral transmission to Human 2 --> CYSTICERCOSIS (eggs mature, invade tissue --> form cysts)
Cysts may form in Brain, Muscles , Tongue
362
Gram +ve rod (branches)
Alcoholics
Lung abscess
Microscopy: Basophilic granules, Grocott stain
Actinomyces
363
Leishmania
Cutaneous - Sandy fly bite, skin ulcer
Diffuse cutaneous - nodular skin lesions
Muco-cutaneous - dermal ulcer
Visceral - Kala Azar, malnourished child, abdo discomfort, BM invasion, splenomegaly
364
Leptospirosis
Dog/Rat urine, Swimming, Fever, Jaundice, Meningism, Carditis, Haemolytic anaemia
365
Incubation period (1-6 hours)
S aureus, Bacillus cereus
366
Incubation period (12-48 hours)
Salmonella, Escherichia coli (watery)
367
Incubation period (48-72 hours)
Shigella (bloody), Campylobacter (flu prodrome)
368
Incubation period (7 days hours)
Amoebiasis (bloody), Giardiasis (non-bloody)
