Micro Flashcards
(296 cards)
1
Q
What is the name of the primary granulomatous lesion of TB (often subpleural)?
A
Ghon focus
2
Q
Presentation of TB, including 3 more serious complications
A
- Fever
- Night sweats
- Weight loss
- Haemoptysis
Subacute meningitis - confusion, personality change, meningism
Spinal (Pott’s disease) - back pain, discitis, iliopsoas abscess
Miliary TB - disseminated haemotgenous spread
3
Q
Investigations for TB
A
- CXR - upper lobe cavitation (post-primary)
- Sputum sample - microscopy on Ziehl-Neelson stain, culture on Lowenstein-Jensen medium for 6 weeks (gold standard) => acid fast bacilli (red rods) seen.
- Tuberculin skin test - shows exposure (including BCG)
- IGRA - shows exposure (not BCG)
4
Q
What is a more affordable and sensitive stain to Ziehl-Neelson?
A
Auramine-rhodamine
but less specific - more false positives. Specific = healthy patients getting correct diagnosis
5
Q
First line treatment for TB
A
RIPE
- Rifampicin - 6 months
- Isoniazid - 6 months
- Pyrazinamide - 2 months
- Ethambutol - 2 months
6
Q
Side effects of first line TB treatment
A
- Rifampicin - orange secretions
- Isoniazid - peripheral neuropathy
- Pyrazinamide - hepatotoxic
- Ethambutol - optic neuritis
7
Q
2nd line TB treatment and prophylaxis
A
2nd line
• Injectables (amikacin), quinolones, linezolid
(Resistance problem)
Prophylaxis
• Isoniazid monotherapy
8
Q
Clinical features of Leprosy (Mycobacterium leprae)
A
- Skin depigmentation
- Nodules
- Trophic ulcers
- Nerve thickening (irreversible)
Slow growing, lifelong illness
9
Q
Who does Mycobacterium Avium-Intracellular complex affect and what infection does it resemble?
A
- Disseminated infection in immunocompromised
* Resembles TB if underlying lung disease
10
Q
Who does Mycobacterium Marinarum (fish tank granuloma) affect and how does it present?
A
Aquarium owners
Papules/plaques
11
Q
Where is Mycobacterium ulcerans (Buruli ulcer) common and how does it present?
A
Tropics / Australia
Painless nodules => ulceration, scarring and contractures
12
Q
What is inflamed in pneumonia?
A
Alveoli
13
Q
Score system name for pneumonia
A
CURB-65
14
Q
3 common bacterial microorganisms that cause hospital-acquired pneumonia
A
- S. aureus
- Klebsiella
- Pseudomonas haemophilus
15
Q
What is the definition of hospital-acquried pneumonia?
A
Pneumonia after >48 hours of hospital admission
16
Q
How is atypical pneumonia different to typical?
A
Atypical
• No classic signs and symptoms
• Not in-keeping with CXR
• Don’t respond to penicillin ABx (no cell wall)
17
Q
3 common bacterial microorganisms that cause bronchitis
A
- S. pneumoniae
- H. influenzae
- Moraxella catarrhalis
18
Q
What is bronchitis?
A
- Inflammation of medium sized airways
* Cough with sputum for most days for 3 months, for 2 or more consecutive years
19
Q
Which pathogen causing penumonia typically causes rusty-coloured sputum and is usually lobar on CXR
A
S. pneumonia
20
Q
Which pathogen causing pneumonia is associated with recent viral infection (e.g. influenza) and shows cavitation on CXR?
A
S. aureus
21
Q
Which pathogen causing pneumonia is associated with alcoholism and haemoptysis?
A
Klebsiella
22
Q
What is seen on microscopy of • S. pneumonia • H. influenza • M. catarrhalis • S. aureus • K. pneumonia
A
- S. pneumonia: +ve diplococci
- H. influenza: -ve cocco-bacilli
- M. catarrhalis: -ve coccus
- S. aureus: +ve cocci “grape-bunch clusters”
- K. pneumonia: “-ve rod, enterobacter”
23
Q
How should you treat atypical pneumonia?
A
Macrolides (clarithromycin) + tetracyclines (doxycline)
24
Q
Name 4 causes of atypical pneumonia
A
- Legionella pneumophilia
- Mycoplasma pneumonia
- Chlamydia pneumonia
- Chlamydia psittaci
25
What can Legionella be grown on?
Buffered charcoal yeast extract
26
Cause of hyponatraemia in Legionella?
Diarrhoea
27
Risk population, presentation and test for Mycoplasma pneumonia?
Univeristy / boarding school students
• Dry cough
• Athralgia
• Erythema multiforme
(Risk SJS, AIHA)
Cold agglutinin test +ve
28
What can cause Chlamydia psittaci?
Birds
29
What are common causes of respiratory tract infections in HIV patients?
* P. jiroveci - fungus causing Pneumocystis pneumonia (desats on exercise)
* TB
* Cryptococcus neoformans
30
What is a common fungal cause of respiratory tract infection and its treatment in neutropenic patients?
Aspergillus spp.
Amphotericin B
31
What are common causes of respiratory tract infection in BM transplant patients?
Aspergillus + CMV
32
What type of organisms commonly cause respiratory tract infection in splenectomy patients?
Encapsulated organisms
33
What are common causes of respiratory tract infection in CF patients?
* Pseudomonas aeruginosa
| * Burkholderia cepacia (high mortality)
34
How can S. pneumoniae and Legionella be diagnosed in severe CAP?
Urine antigen tests
35
Which diagnostic tests are useful in difficult-to-culture causes of pneumonia such as Chlamydia?
Paired serum samples
At presentation, then 10-14 days - rise in Ab level
36
Boat-shaped organisms seen. What is the diagnosis and the stain that was used?
PCP
| Silver stain
37
ABx treatment for mild / moderate classical CAP
Amoxicillin
OR
Clarithromycin / doxycycline
38
ABx treatment for severe classical CAP
Co-amoxiclav + Clarithromycin
OR
Erythromycin
39
Outline CURB-65
* Confusion
* Urea > 7
* RR ≥ 30
* SBP < 90, DBP ≤ 60
* ≥ 65 yo
40
ABx treatment for HAP
1. Ciprofloxacin +/- vancomycin
2. ITU: piptazobactam + vancomycin
Aspiration pneumonia - cefuroxime + metronidazole
41
Legionella and Chlamydia psittaci ABx
Macrolides
42
S. aureus pneumonia ABx
Flucloxacillin
43
MRSA pneumonia treatment
Vancomycin
44
What is infective endocarditis and the symptoms?
Infection of innermost layer of heart - usually valves
* Fever
* Anorexia
* Weight loss
* Night sweats
Acute - SOB, chest tightness, embolic complications
45
Why is it important to ask about dental history if infective endocarditis is suspected?
Important route of infection
46
2 risk factors for infective endocarditis
* Right heart failure
| * Valve replacement
47
What can be seen on examination in infective endocarditis?
* Changing heart murmurs
* Clubbing
* Splinter haemorrhages
* Osler's nodes (tender)
* Janeway lesions (non-tender)
* Roth spots (fundoscopy)
* Splenomegaly
48
Why is tricuspid valve endocarditis more common in intravenous drug abusers?
IV reaches right heart first
49
2 infective agents of subacute bacterial endocarditis
* Low virulence strep (S. viridians)
| * Staph. epidermis
50
What type of endocarditis do the following pathogens cause:
• S. aureus - IVDA
• S. pyogenes
• Coagulase negative staphylococci - prosthetics
Acute bacterial endocarditis
51
Empirical treatment of infective endocarditis
Native valve
• Acute: flucloxacillin
• Indolent: penicillin + gentamycin
Prosthetic valve
• Vancomycin + gentamycin + rifampicin
52
Which valves are most commonly involved in infective endocarditis?
Mitral + aortic valves
53
Outline Dukes criteria for infective endocarditis
2 major
1 major + 3 minor
5 minor
Major
• Positive blood cultures
• Echo findings - vegetations
Minor
• Predisposing heart condition or IVDA
• Fever >38 or high CRP
• Immunologic phenomena e.g. splinter haemorrages, haematuria
• Vascular phenomena
• Positive blood culture not typical of IE
54
Treatment for MSSA endocarditis
Flucloxacillin
55
What is important to note about taking blood cultures in infective endocarditis?
Take at least 3 from different sites (new guidelines suggest 6)
(Investigations are x3 BC and echo)
56
Why is 6 weeks of ABx treatment needed for infective endocarditis?
Valves have poor vascular supply
57
What are the 3 mechanisms of GI disease
* Secretory diarrhoea with no fever or white cells in stool
* Inflammatory diarrhoea with fever and white cells in stool
* Enteric fever with little stool change
58
Give an example of secretory diarrhoea and its mechanism
Cholera toxin
• cAMP normally opens chloride channels in apical membrane of enterocytes
• Toxin opens chloride channels - efflux into lumen - loss of water and electrolytes
59
Describe the mechanism where systemic toxicity occurs in secretory diarrhoea, with reference to superantigens
* Superantigens bind to T cell receptors outside the binding site
* Cytokine release by CD4+
60
How can Staph aureus food poisoning spread?
Unwashed hands or skin lesions on food handlers touching food
1/3 are chronic carriers, 1/3 are transient carriers
61
How do you diagnose staph aureus food poisoning?
* Catalase and coagulase positive gram positive coccus - tetrads or clusters
* Gold-yellow colonies with beta haemolysis on blood agar
62
Mechanism and effect of staph aureus food poisoning
* Produces enterotoxin (exotoxin)
* Superantigen in GIT
* Release of IL1 and IL2
* Vomiting & watery diarrhoea
63
Where can Bacillus cereus come from, how does it cause food poisoning, and how does it present?
* Spores germinate in reheated fried rice
* Heat stable emetic toxin not destroyed by reheating
* Heat labile diarrhoeal toxin if not heated high enough
* Watery, non-bloody diarrhoea
* Sudden vomiting
64
Food cause, mechanism and effects in clostridium botulinum (Gram positive anaerobe)
Gram positive anaerobe
* Canned / vaccum packed food, honey
* Blocks ACh release from peripheral nerves
* Descending paralysis
65
Food cause, mechanism and effects in clostridium perfringens (Gram positive anaerobe)
Gram positive anaerobe
* Reheated meat
* Superantigen in small intestine
* Watery diarrhoea and gas-gangrene
66
Causes and name of disease caused by clostridium difficile (Gram positive anaerobe)
* HAI from ABx therapy (cephalosporins, cipofloxacin, clindamycin)
* Pseudomembranous colitis
67
Who does Listeria monocytogenes affect, what causes it, how does it present and how is it treated?
* Pregnant women
* Refridgerated food, particularly unpasteurised dairy
* Presents with watery diarrhoea, fever (little vomiting)
* Tx ampicillin
68
Common name for E. coli effect and where is it found?
* Traveller's diarrhoea
| * Food and water contaminated with human faeces
69
2 types of enterotoxins in E. coli and what do they do?
* Heat labile - stimulates adenyl cylase and cAMP
| * Head stable - stimulates guanylyl cylase
70
Which parts of the GIT do E. coli toxins act?
Jejunum and ileum
71
What are the 4 types of E. coli? What do they do?
Enterotoxigenic (ETEC) - main cause of travellers diarrhoea
Enteropathogenic (EPEC) - infantile diarrhoea
Enteroinvasive (EIEC) - dysentery
Enterohaemorrhagic (EHEC) - caused by verotoxin producing 0157:H7 E. coli => HUS (anaemia, thrombocytopaenia, renal failure)
72
E. coli treatment
No specific treatment - self-limiting
73
Outline identification of Salmonella inc. antigens
TSI agar - red colonies with black centres (also produce hydrogen sulphide on XLD agar)
Non-lactose fermenting
Antigens:
• Cell wall - O
• Flagellar - H
• Capsular - Vi (virulence, anti-phagocytic)
74
Patient presents with slow onset fever, constipation and rose spots. What is the diagnosis, how is it transmitted, where does it multiply in the body and how is it treated?
Salmonella typhi / paratyphi
• Transmitted via water and food contaminated by human faeces
• Multiplies in Peyers patches
• Treatment with iv fluids, iv ceftriaxone, then PO azithromycin
75
Patient falls ill after eating undercooked poultry and eggs. What is the pathogen responsible, how do you expect them to present, which tissue is invaded and how is it treated?
Salmonella enteritidis
* No fever
* Diarrhoea
* Invasion of epithelial and subepithelial tissue of bowels
* Self-limiting, no tx
76
Is shigella lactose fermenting and does it produce hydrogen sulphide? Furthermore, what are the cell wall and polysaccharide antigens?
* Non-lactose fermenting
* Doesn't produce hydrogen sulphide
Antigens:
• Cell wall- O
• Polysaccharide - A-D, indentifies species
77
Which part of the GIT does shigella invade, how does it present, what treatment should be avoided, and which group of people are at higher risk of contracting the infection?
Invasion of mucosa of distal ileum and colon
Fever and severe bloody diarrhoea
Avoid abx
Increased MSM risk
78
Patient has rice water stool with no inflammatory cells. What is the pathogen responsible, how it transmitted, what leads to the watery stool, how it treated, and what is the epidemic subset?
Vibrio cholerae
• Food and water contaminated with human faeces e.g. shellfish
• A + B subunits - increased cAMP opens Cl- channel at apical membrane, efflux of Cl- to lumen
• Supportive tx
O1 group - epidemic subset
79
Patient in Japan presents with diarrhoea. He has been eating raw seafood (oysters) recently. Treated successfully with doxycycline. What is the pathogen responsible?
Vibrio parahaemolyticus
80
A HIV-positive shellfish handler was eating shellfish for dinner. He cut himself by accident at dinner, cleaned it up and went for a swim in the sea. He presented with cellulitis, diarrhoea, and vomiting, and has become septic. What is the responsible pathogen and what abx could be considered?
Vibrio vulnificus
| • Treatment with doxycline
81
Which genus of gram-negative bacteria are comma shaped and late lactose fermenters? Are they oxidase positive?
Vibriosis
| • Oxidase positive
82
Which genus of gram-negative bacteria are comma or S shaped? Are they oxidase positive?
Campylobacter
| • Oxidase positive
83
Patient presents with a headache and fever, followed by abdominal cramps and bloody, foul-smelling diarrhoea. He admits to drinking unpasteurised milk and having a BBQ with chicken the other day. The BBQ from the garden may not have been cleaned either. What is the responsible pathogen and how should this be treated?
Campylobacter jejuni
| • If immunocompromised or >5 days: macrolides e.g. erythromycin
84
How is Yersinia enterolitica transmitted, what temperature does it prefer, how does it present, and what other manifestations is it associated with?
* Food contaminated with domestic animals faeces
* Prefers 4 degrees (cold enrichment)
* Enterocolitis, mesenteric adenitis with necrotising granulomas
* Associated with reactive arthritis and erythema nodosum
85
Patient (MSM) has returned from camping where he cooked food over a fire and drank water from the stream. He has no fever, but foul-smelling non-bloody diarrhoea. He also has RUQ pain. What is the pathogen responsible, what is the cause of the RUQ pain, and how would this be treated? How could aquiring this infection through the contaminated water be prevented?
```
Entamoeba histolytica
• Foul-smelling non-bloody diarrhoea (motile trophozoite in diarrhoeal, non-motile cyst in non-diarrhoeal)
• RUQ pain - liver abscess
• Treat with metronidazole
• Boiling water and water filters
```
86
Flask-shaped ulcer seen on histology. Pathogen also detected in ELISA string test, stool microbiology and serology (invasive disease).
What is the pathogen responsible?
Entamoeba histolytica
87
Which part of GIT does Cryptosporidium parvum infect, how does it present, and how is it treated in aduts/kids?
* Infects jejunum
* Severe diarrhoea in immunocompromised
* Treat with paromomycin, or nitazoxanide in kids
88
Oocysts seen in stool by modified Kinyoun acid fast stain. Pathogen responsible?
Cryptosporidium parvum
89
Pear shaped trophozoite seen in traveller/hiker/mental hospital. Pathogen responsible and infection it is similar to.
Giardia lamblia, similar to Entamoeba histolytica
90
How does rotavirus present and how much exposure is needed for lifelong immunity
* Watery diarrhoea
| * 2x exposure - immunity
91
How are UTI symptoms in children <2 years different to >2 years?
Non-specific i.e. failure to thrive, vomiting, fever
rather than frequency, dysuria, flank pain
92
Diagnosis of UTI
Differentiate between coliforms / non-coliform UTI
• Urine dipstick - positive nitrites = coliform, -ve nitrites +ve leucotyes = non-coliform
93
Why are urine samples often contaminated?
Urethral areas aren't sterile, even though bladder urine is sterile
94
Which cells seen on microscopy are indicative of contamination of urine sample? And which are indicative of infection?
Contamination - squamous epithelial cells
Infection - white cells (sterile pyuria) - consider STI, TB, bladder neoplasm, prior abx treatment
95
Treatment for UTI in women andn men
Women
Nitrfurantoin
or Trimethoprim if low risk of resistance and EGFR >45
Men
Levofloxacin or ciprofloxacin
96
Treatment for pyelonephritis
Co-amoxiclav +/- gentamicin
97
Treatment for candida UTI (caused by indwelling catheter)
No benefit of treating asymptomatic infection
98
3 pathogens causing surgical site infections and presentation
* S. aureus
* E. coli
* P. aeruginosa
• Failure to heal
99
Which layers does a deep incisional surgical site infection reach?
Fascial and muscle layers
100
What number of microorganisms increases risk of surgical site infection?
>10^5
101
Most common microorganism in osteomyelitis
S. aureus
102
General treatment for osteomyelitis
1. IV ABx for at least 6 weeks
| 2. Debridement
103
Pathophysiology of septic arthritis
* Bacterial proliferation in synovial fluid
* Inflammatory response
* Joint damage - exposure of fibronectin
* Bacteria (most common S. aureus) adhere to fibronectin
104
Diagnosis and treatment for septic arthritis
* Synovial fluid aspiration (WBC >50,000)
* Blood culture
* ESR and CRP
* ABx: 2 weeks IV, 4 weeks oral
* Joint drainage
105
3 features of prosthetic joint infection
* Joint never right after operation
* Early failure
* Sinus tract
106
Common microorganism in prosthetic join infection
Coagulase negative staphylococci (more common than S. aureus)
107
Diagnosis and treatment for prosthetic joint infection
* X-ray - loosening (bone loss)
* Joint aspiration - higher WCC in hip vs knee
* Intraoperative 5x tissue specimens - >3 identical organisms = PJI
* Remove prosthesis and dead bone
* Re-implant with antibiotic impregnated cement
108
Treatment for MRSA surgical site infection
IV linezolid
109
Cause of C. diff
Gut flora disturbed by Abx, particularly
• Clindamycin
• Cephalosporins
• Ciprofloxacin
Spore ingestion
-> pseudomembranous colitis etc.
110
Treatment for C. diff
ORAL metronidazole
111
3 main causative organisms of acute meningitis (hours-days)
* N. meningitis
* Strep pneumoniae
* H. influenzae B
112
3 causative organisms of meningitis in neonates
* Group B Strep
* Listeria
* E. coli
113
2 causes of chronic meningitis. What does CT show?
TB or Cryptococcus
Leptomeningeal enhancement on CT
114
2 risk factors of meningitis (N. men and S. pneu)
* Complement deficiency
| * Hyposplenism
115
Treatment for bacterial meningitis. What would you consider if consciousness was reduced?
Resus
Ceftriaxone and corticosteroids
Cover listeria with ampicillin
Don't use corticosteroids under 3 months
Consider IV acyclovir if consciousness affected to cover encephalitis
116
Cause of bacterial and amoebic encephalitis
Bacterial - Listeria
| Amoebic - Naegleria fowleri (lives in warm water)
117
Imaginging of spinal infections
MRI > CT
118
What's the most common infection of the CNS, organisms implicated and age group affected?
Aseptic meningitis
Cocksackie group B and echovirus
< 1 year
119
What conditions should you consider if there are painless/painful genital ulcers?
Painless - Syphilis
| Painful - herpes
120
What can develop in a neonate if gonorrhoea is untreated and transferred to the child from the birth canal?
Opthalmia neonatorum (neonatal conjunctivitis)
121
Diagnosis and treatment of gonorrhoea
Urethral smear (most sensitive) and culture from this (gold standard)
Ceftriaxone or cefixime, single dose
122
How does chlamydia present in most people
Asymptomatic
123
What can the different serovars of Chlamydia cause?
A, B, C - trachoma -> infection of eyes -> blindness
D-K - genital chlamydia, ophthalmia neonatorum
124
Diagnosis and treatment of chlamydia
NAAT
Azithromycin stat or doxycyline 7/7
125
What are the side effects of doxycycline and when is it contraindicated?
N&V, photosensitivity
C/I pregnancy
126
What is lympho-granuloma venereum caused by?
Lymphatic infection with Chlamydia trachomatis
Serovars L1, L2, L3
127
Outline the stages of lympho-granuloma venereum
Early, primary (3-12 days): painless gentical ulcer, balanitis, proctitis, cervicitis
Early, secondary (2-25 weeks) - painful inguinal buboes, may rupture, fever
Late - abscess formation, genital elephantiasis
128
How is lympho-granuloma venereum currently commonly presenting in patients?
MSM
| Rectal pain, tenesmus, bleeding, mucous discharge
129
Diagnosis and treatment for lympho-granuloma venereum
NAAT
Doxycycline 3 weeks
130
What is syphilis caused by and what does the organism look like?
Treponema pallidum - obligate gram-negative spirochaete
131
What type of micoscopy can treponemes be seen under in primary lesions?
Dark-ground microscopy
132
What is the VDRL and RPR test?
Useful for primary syphilis
Non-treponemal test (detects non-specific antigens)
VDRL - detects lipoidal antibody on host and treponemal cells
RPR - modified VDRL
Titre falls in response to treatment - can be used to monitor response
133
What do treponemal tests do, and which can be used for syphilis diagnosis? How long do they remain positive for?
Detect antibodies against specific antigens from T. pallidum
EIA, T. pallidum particle agglutination test (TP-PA) etc.
More specific than non-treponemal but remains positive for years
134
In which stages of syphillis is a 'snail track' oral ulcer, condyloma acuminate (genital warts), and Argyll-Robertson pupil (not very responsive to light) seen? What is the most common tertiary sign in HIV+ve patients? When is early and late syphilis? And how does latent syphilis present?
Secondary (1-6 months) - 'snail track' oral ulcer, condyloma acuminate (genital warts)
Tertiary (2-40 years) - neurosyphilis (most common in HIV +ve), Argyll-Robertson pupil (not very responsive to light but accomodates)
```
Early = <12 months
Late = >12 months
```
Latent - asymptomatic, serological infection
135
Treatment for primary syphilis
Single IM benzathine penicillin
136
What is the Jarisch-Heimer reaction?
Common reaction to syphilis treatment
Fever, headache, syphilis symptom exacerbation
Develops within hours and clears within 24 hours.
137
What does Haemophilus ducreyi (gram-negative) cause, where in the world it is found, presentation and diagnosis
Chancroid
Tropical disease mainly in Africa, rare in UK
Multiple, painful ulcers
Culture chocolate agar, PCR
138
Patient from PNG presents with expanding ulcers from papule, which break down and are beefy red. Klebsiella granulomatis, gram-negative detected. What is the name of the condition and what stain is used?
Donovanosis
Giema stain, Donovan bodies
139
Trichomoniasis pathogen type, presentation, diagnosis and treatment
Flagellated protozoan
Asymptmatic/urethritis in men, abnormal discharge in women
Wet prep microscopy, PCR
Metronidazole
140
Microscopy shows clue cells, pH is raised, and whiff test is positive. What is the condition and its cause?
Bacterial vaginosis
Abnormal vaginal flora, polymicrobial, low lactobacilli, sexually associated not transmitted, hygiene practices
141
Candidiasis (candida albicans) presentation and treatment
White thick discharge, itching, soreness, redness, vulvovaginitis (women), balanitis (men)
Not sexually transmitted
Oral antifungals e.g. clotrimazole, fluconazole
142
Molluscum contagiosum cause, presentation in children, adults, PWHIV, and generally immunocompromised. Treatment.
Pox virus
Hands + face in children
Genital lesions in adults
Facial - adults with HIV (until proven otherwise)
Giant lesions - immunocompromised
Cryotherapy if required
143
Genital warts cause and treatment
HPV: visible genital warts - 6 or 11
Home - podophyllotoxin solution/cream
Clinic - 1. cryotherapy 2. imiquimod
Oncogenic (16, 18) associated with cervial, anal etc. cancers
144
Which abx classes inhibit cell wall synthesis (give examples)?
Beta lactams e.g. penicillins (benzylpenicillin), cephalosporins (ceftriaxone), carbapenems (meropenem)
145
How do beta lactams work, are they bactericidal or bacteriostatic, and when are they ineffective?
Inactivate transpeptidases involved in terminal stages of cell wall synthesis - weaken cell wall
Bactericidal
Ineffective if in stationary phase of cell cycle or don't have peptidoglycan wall e.g. mycoplasma and chlamydia
146
Penicillin vs amoxicillin targets
Penicillin - gram +ve
| Amoxicillin - more broad-spectrum
147
How do cephalosporins change in activity with increasing generation?
Increased activity against gram -ve and decreased against gram +ve
148
Do beta lactams cross the BBB?
Not if intact
Yes if inflamed meninges e.g. meningitis
149
How do glycopeptides work?
Inhibit cell wall synthesis: instead of binding to enzymes like beta lactams, they bind to binding sites of enzymes on cell wall component precursors
Bactericidal
Large molecules so can't pass gram -ve outer membrane
Active against gram +ve
150
Which classes of abx inhibit protein synthesis (and give examples)?
Aminoglycosides e.g. gentamicin
Tetracyclines e.g. doxycycline
Macrolides e.g. erythromycin
Chloramphenicol
Oxazolidinones e.g. linezolid
151
How do aminoglycosides work?
Bind to amino-acyl site of 30S ribosomal subunit
Misreading of codons along mRNA
Prevent elongation of polypeptide chain
Bactericidal
152
What toxicity do aminoglycosides have?
Ototoxic and nephrotoxic
153
Why are aminoglycosides not effective in abscesses?
Inhibited by low pH
154
What are aminoglycosides useful in treating?
Gram -ve sepsis
155
How do tetracyclines work and what do they target?
Broad-spectrum but most gram -ve are resistant
Bind to ribosomal 30S subunit, preventing binding of tRNA to acceptor site
Bacteriostatic
Activity against intracellular pathogens
156
Where can tetracyclines deposit in the body?
Bone, causing discolouration of growing teeth
157
How do macrolides work?
Gram +ve
Bind to ribosomal 50S subunit, interfering with translation
Bacteriostatic
158
How does chloramphenicol work?
Binds to peptidyl transferase of 50S ribosomal subunit
Bacteriostatic
Broad spectrum
159
What risks are there with taking chloramphenicol?
Aplastic anaemia
Grey Baby Syndrome in neonates - reduced ability to metabolise
160
How do oxazolidinones work?
Bind to 23S of 50S to prevent 70S formation, for translation
Gram +ve e.g. MRSA and vanc. resistant E
161
What are the problems with oxazolidinones?
Expensive
May cause thrombocytopaenia and optic neuritis
162
Which abx classes inhibit DNA synthesis (give examples)?
Fluoroquinolones e.g. ciprofloxacin
Nitroimidazoles e.g. metronidazole
163
How do fluoroquinolones work?
Act on DNA gyrase
Bactericidal
Better with gram negative
164
How do nitroimidazoles work and which abx are related?
Active intermediated formed under anaerobic conditions - DNA strand breakage
Bactericidal
Nitrofurans are related compounds - concentrate in the bladder
165
Which abx classes inhibit RNA synthesis (give examples)?
Rifamycin e.g. rifampicin
166
How does rifampicin work?
Binds to DNA-dependent RNA polymerase, inhibiting initiation
Bactericidal
167
What should and shouldn't rifampicin be used to treat?
Active against Mycobacteria and Chlamydiae
Not used for short-term prophylaxis due to rapid chromosomal mutation resistance in beta-subunit of RNA polymerase
- exception is meningococcal infection
168
What is important to monitor whilst taking rifampicin?
LFTs
Beware of interactions with other drugs metabolised by the liver
169
Which abx are cell membrane toxins (give examples)?
Polymyxin e.g. colistin
Cyclic lipopeptide e.g. daptomycin
170
What do the cell membrane toxins treat?
Polymyxin - gram -ve (P. aeruginosa etc.)
Cyclic lipopeptide - gram +ve (MRSA, VRE)
171
Which abx inhibit folate metabolism (give examples)?
Sulfonamides e.g. sulphamethoxazole
Diaminopyrimidines e.g. trimethoprim
172
When can combination of different folate metabolism inhibitors be useful?
PCP - sulphonamide resistance is common
173
What stranded type of virus is influenza?
Negative-sense RNA
174
What 3 characteristics do pandemic viruses need?
* Novel antigenicity
* Replicate efficiently in human airway
* Transmit efficiently between people
175
Which 3 flus tend to affect humans each year and when?
* Influenza A (H1) - beginning of January
* Influenza A (H1N1) - end of December
* Influenza B - March
176
What is the natural animal reservoir of Influenza A?
Ducks
177
How do influenza viruses enter a cell?
1) Influenza HA (haemagglutinin) binds to exterior cell surface sialic acid receptors
2) Influenza NA (neuraminidase/sialidase) cleaves sialic acid (also needed for virus release)
3) Virus enters cell
178
What is the difference between antigenic drift and antigenic shift?
Antigenic drift - mutation to HA/NA, new strains
| Antigenic shift - complete change of HA/NA, random reassortment, only influenza A
179
Where is tryptase found and what is it responsible for in influenza?
* Found in bronchiolar cells
* Cleave HA of influenza A
* Activates the virus
180
Antivirals for influenza
Amantadine
• Influenza A
• Targets M2 ion channel
Neuraminidase inhibitors e.g. oseltamivir (tamiflu)
• Stops virion exit
• Effective <48 hours after infection
181
What strand type of viruses are coronaviruses?
Positive-sense single-stranded RNA
182
Treatment for COVID-19
* Dexamethasone
| * Remdesivir (RNA polymerase inhibitor)
183
HSV in immunocompromised effects
* Cutaneous dissemination
* Oesophagitis
* Hepatitis
184
How does acyclovir work?
* Activated by thymidine kinase
* Aciclovir triphophate incorporated into DNA, instead of deoxyguanosine triphosphate (dGTP)
* Chain termination
* No 3' hydroxyl group - additional nucleosides prevented from attaching
185
Effects of congenital HSV infection
* Microcephaly
* Scarring
* Microphthalmia
186
Effects of congenital VZV infection
* Microcephaly
* Scarring
* Limb hypoplasia
* Chorioretinitis, cataracts - no red reflex
187
• Purpura fulminans
• Visceral infection
• Pneumonitis
Neonatal effects of which virus?
VZV
188
Scrapings of a rash shows multinucleated giant cells (Tzanck cells). Which pathogen is responsible?
VZV
189
Where does CMV lie latent?
Monocytes and dendritic cells
190
```
• Encephalitis
• Retinitis
• Pneumonitis
• Colitis
• Marrow suppression
Effects in immunocompromised patients infected with which pathogen?
```
CMV
191
How can CMV infected cells be described to look like?
Owl's eye inclusions
192
CMV main congenital effect
Sensorineural deafness - primary cause
193
CMV treatment
1) Ganciclovir
(IV) / valganciclovir (oral) - guanosine analogue chain terminator
2) Foscarnet (IV) - pyrophosphate analogue DNA polymerase inhibitor. Nephrotoxic.
3) Cidofovir (IV) - nucleotide analogue chain terminator
194
EBV immunocompromised effects
Post-transplant lymphoproliferative disease - predisposes to lymphoma. Treat with rituximab
195
EBV treatment
Supportive
Penicillin causes wide-spread maculopapular rash
196
Most common cause of febrile convulsions
HHV6 => Roseola
197
Where does HHV6 lie latent?
Monocytes / lymphocytes
198
HHV8 immunocompromised effects
* Kaposi's sarcoma (HIV assoc)
* Primary effusion lymphoma (EBV assoc)
* Castleman's disease
199
Immunocompromised patient has progressive multifocal leukoencephalopathy and rapidly demyelinating disease, and so is treated with ART. What is the diagnosis?
JC virus
200
Immunocompromised patient has haemorrhagic cystitis and nephropathy. What is the cause and treatment?
BK virus
Cidofovir
IVIG for nephropathy
201
Who does BK virus commonly affect?
Patients post HSCT or kidney transplant
202
Adenovirus treatment
Supportive
Cidofovir, IVIG if multi-organ involvement
203
Hep A transmission, incubation time
Faeco-oral transmission
2-6 weeks incubation
204
Hep A treatment
Supportive
Havrix vaccine
205
What does high IgG and moderate IgM in hep A suggest?
Past infection
206
Can hepatitis B be cleared?
90% clearance >5 y.o.
207
Hep B treatment
Acute - supportive
1. Inferferon alpha (don't use in liver transplant)
2-4. Nucleoside analogues (lamivudine, entecavir, telbivudine)
5. Nucleotide analogue (tenofovir)
208
Hep B antibodies seen in:
1. Current infection
2. Past infection
3. Vaccinated
1. HB surface antigen, HB core antibody
2. HB surface antibody, HB core antibody
3. HB surface antibody
Acute infection will have IgM anti-HBc, which chronic won't
209
Can hepatitis C be cleared?
60-80% chronicity
210
How is hepatitis C spread?
Blood products
211
Hep C treatment
1. Vaccine
2. Interferon
3. NS3/4 protease inhibitors -previrs
4. NS5A inhibitors, -asvirs
5. Direct polymerase inhibitors, -buvirs
212
When can someone only be infected with hep D?
With Hep B
Superinfection (catching hep D after hep B) more common than coinfection (catching both at the same time)
213
Hep D treatment
Peginterferon-alpha
214
How is hep E transmitted?
Faeco-oral
| Shellfish, uncooked pork
215
Hep E incubation range
2-10 weeks (6-8 week avg)
216
When is the Hep E vaccine, which is being trialled, dangerous?
3rd trimester of pregnancy
217
Patient has postauricular, occipital, and posterior cervical lymphadenopathy, maculopapular rash, fever, and red lesions on soft palate (Forchheimer sign). What is the diagnosis?
Rubella
218
Rubella potential complications if infected between 13-18 weeks
Hearing defects and retinopathy
219
Human parvovirus B19 signs/complications and alternative name
Slapped cheek syndrome (fifth disease)
• Erythema infectiosum
• Transient aplastic crisis
• Arthralgia
Viral myocarditis
220
Human parvovirus B19 congenital infection complications
Hydrops foetalis
221
Morbillivirus (measles) 2 specific signs
* Koplik's spots (white, buccal mucosa)
| * Maculopapular rash - starts behind ears
222
Zika virus congenital complications
* Microcephaly
* Talipes (feet turned in like club foot)
* Hypertonia
223
What does Hepatitis B e-antigen suggest?
Very infectious
224
What are the common congenital infections?
```
TORCH
• Toxoplasmosis
• Other (HIV, HBV)
• Rubella
• CMV
• HSV
```
225
Diagnosis of congenital infection?
Maternal blood serology
| Amniocentesis
226
Cause of late-onset sepsis (>48 hrs)
Coagulase negative staph + GBS
227
1st line treatment for late-onset sepsis
Benzylpenicillin + gent
228
Late-onset sepsis from community treatment
Amoxicillin + cefotaxime
e.g. for listeria + community meningitis
Benzylpenicllin given in GP
229
How is pyrexia of unknown origin (PUO) defined?
* >38.3°C on several occasions
* > 3 weeks
* Despite 1 week of intesive investigation
230
```
Outline the following different types of PUO:
• Classical
• Healthcare-associated
• Neutropaenic
• HIV-associated
```
Classical
• >3 days in hospital or >3 O/P visits
• e.g. infections, neoplasms, connective tisseue diseases
Healthcare-associated
• Develops following >24 hours in hospital
• Surgery, drugs (e.g. serotonergics), medical devices
```
Neutropaenic (<500)
• Medical emergency
• Chemotherapy
• Haem malignancies
• Conditions that require neutrophils e.g. fungal, bacterial sepsis
```
HIV-associated
• Seroconversion
• TB
• Kaposi's sarcoma
231
Dengue platelet levels and diagnostic test
Low platelets
| PCR blood
232
* Blancing maculopapular rash
* Severe myalgia
* Retroorbital headache
Disease?
Dengue
233
What is sphygmo thermal dissociation and where is it seen?
aka Faget sign
High temperature with bradycardia
Typhoid, yellow fever, brucellosis
234
P. falciparum blood film
* Young trophozoites in abscence of mature trophozoites
* Crescent-shaped gametocytes
* Double dotted ring
* Maurer's clefts
235
P. falciparum treatment
1. Artemether/lumefantrine. IV artesunate if severe.
| 2. Quinine and doxycycline
236
Outline approach to severe falciparum malaria
* ABC
* Correct hypoglycaemia
* Cautious rehydration
* Organ support
* IV artesunate
237
Seen on blood film:
Schüffner's dots
>20 merozoites/schizonts
What is the diagnosis, where is this species common and what is the treatment?
P. vivax
Central America / India
Chloroquine then primaquine (check G6PD deficiency first)
238
Where is P. ovale common, what is seen on blood film, what is the treatment?
Africa
Schüffner's dots
Chloroquine then primaquine (check G6PD deficiency first)
239
P. malariae treatment
Chloroquine
240
Which parasite stage can lie dormant in the liver in malaria?
Hypnozoites
241
What do schizonts look like and what do they release?
Daisy head
Release merzoites, which rupture from infected cell
242
Difference between use of thick and thin film
Thick - find parasitaemia
| Thin - distinguish species
243
Common blood test findigns in malaria
WCC rarely raised
Low platelets
Deranged LFTs
Anaemia
244
Features of severe malaria
* Impaired consciousness or seizures (vaso-occlusive crisis)
* Acidosis
* Hypoglycaemia
* Pulmonary oedema
* Parasitaemia >2
245
Which infection results after a cat scratch and how is it treated?
Bartonellosis
Most resolve without treatment but erythromycin can be used
246
What complication is characterised by neovascular proliferation of bartonella in the skin or the internal organs?
Bacilliary angiomatosis
247
Infection is detected with sabin feldman dye and treated with pyrimethamine + sulfadiazine + calcium folinate. What is the diagnosis and what treatment would be used in pregnant patients?
Toxoplasmosis
Spiramycin
248
Outline bacterial infection associated with water-sports, acute form, and treatment
Leptospirosis
Excreted in dog/rat urine
Penetrates broken skin
Weil's disease (acute form) - jaundice, kidney failure, bleeding
Tx - amoxicillin
249
Complications of brucellosis
Endocarditis, osteomyelitis
250
Investigation and treatment for brucellosis
Serology: anti-O-polysaccharide antibody
Tetracycline or doxycycline + streptomycin
251
What is the histopathological feature found in the cytoplasm of nerve cells containing rabies virus (rhabdovirus) called?
Negri bodies
252
Treatment for rabies
Post-exposure rabies IgG
253
Patient working with cattle and small ruminants has painless round black lesions with a rim of oedema, lymphadenopathy, and mediastinal haemorrhage. What is the diagnosis, and what is is the name of the pulmonary manifestations?
Anthrax
Woolsorters disease
254
Lyme disease transmission, signs, diagnosis and treatment
Tick bite
Cyclical fever, erythema chronicum migrans (ECM) - bullseye rash
Late persistent - arthritis, neuropsychiatric disturbance
Ix - Biopsy edge of ECM + ELISA for antibodies
Tx - Doxycycline
255
Patient has inhaled barn dust contaminated by infected sheep, goats, cattle, and presented with signs of atypical pneumonia. What is the diagnosis?
Q fever
256
How is Leishmaniasis transmitted?
Bite of sandfly
257
Outline the 4 typs of leishmania
Cutaenous - ulcer, 1 year heal, scar, type IV
Diffuse cutaneous - nodules, immunodeficient
Muco-cutaenous - ulcers in nose/mouth/skin, months-years
Visceral = Kala Azar - young malonourished child, skin pigmentation, abdo discomfort, Leishmania donovani - invasion of reticuloendothelial system -> hepatosplenomegaly
258
Outline trypanosomiasis infection
• T. brucei
• T. rhodesiense
• T. cruzi
Bite of tsetse fly generally in sub-Saharan Africa
* T. brucei - most common, gradual infection
* T. rhodesiense - rapid infection
* T. cruzi (Chagas disease) - transmitted by Reduviidae insects only in Americas (Brazil). Initially purple eyelids. Later achalasia (difficulty for food to pass down oesophagus)
259
What can be used to examine superficial fungal infections?
Wood's lamp
260
2 types of superficial fungal infections
Tinea (dermatophyte)
Pityriasis
261
• Periodic acid-Schiff stain
• Sabouraud agar
• Beta-d-glucan assay
These are all used to diagnose what disease?
Candida (deep seated fungal infection)
262
Treatment of Candida and invasive disease
Fluconazole for C. albicans
Amphotericin-B for invasive disease
263
How does Aspergillus (deep seated fungal infection) present?
Pneumonia
264
B-Glucan test
Grows on Czapek dox agar
Galactomannan antigen for invasive disease
Diagnosis for which diseases?
Aspergillus
265
Treatment for Aspergillus
Voriconazole
266
How does Cryptococcus (deep seated fungal infection) present?
Meningitis with insidious onset in immunocompromised
Hydrocephalus
267
Which animal is Cryptococcus associated with?
Birds (pigeons)
268
Serum is positive for the antigen of this microorganism and CSF india ink stain shows black staining for it except the capsule of the microorganism. What is the diagnosis?
Cryptococcus
269
Cryptococcus treatment
Amphotericin B +/- flucytosine
270
Stain for PCP
Methenamine Silver
271
Outline mucormycosis
aka Black Fungus
* Immunocompromised
* Infects sinuses and brain
* DM is a risk factor
* Tx - amphotericin B and surgical debridement
272
What is Sporotothrix schenckii also known as and how does it infect?
Rose Gardener's disease
Present in live and decomposing plant material
Infects through cut or puncture wound in skin
273
Which chromosome is prion protein gene on and what is the codon polymorphism?
Chr20 - predominantly expressed in CNS
Codon 129 polymorphism
274
In prion disease:
What configuration does abnormal PrP(sc) fold?
What is it resistant to?
What does promote the coversion of?
```
Abnormal PrP(sc) folds a beta-sheet configuration
...which is protease/radiation resistant
```
PrP(sc) acts as a template - promotes irreversible conversion of PrP to insoluble PrP(sc)
275
Symptomatic and delaying prion 'conversion' treatment
For myoclonus - clonazepam
| Delaying conversion - quinacrine, pentosan, tetracycline
276
EEG in sporadic CJD (Creutzfeldt-Jakob disease) and variant CJD
Sporadic - periodic triphasic changes
| Variant - non-specific slow waves
277
CSF analysis in sporadic and variant CJD
14-3-3, marker of neurodegeneration
| can be normal in variant
278
Western blot PrP(sc) types in sporadic, variant, and iatrogenic CJD
Sporadic - types 1-3
Variant - type 4t (from tonsillar biopsy)
Iatrogenic - types 1-3
279
CJD type if MRI shows basal ganglia highlighted or posterior thalamus highlighted on MRI-T2 (pulvinar sign)
Sporadic - normal / basal ganglia highlighted
Variant - posterior thalamus highlighted on MRI-T2 (pulvinar sign)
Inherited prion disease - sometimes basal ganglia highlighted
280
Post-mortem findings in sporadic and variant CJD
Sporadic - spongiform vacuolation, PrP amyloid plaques
Variant - PrP(sc)4t detectable in CNS + lymphoreticular tissue, florid plaques
281
Cause and presentation of sporadic CJD (sCJD)
Cause - somatic PRNP mutation or spontaneous conversion
Presentation - rapid, progressive demention with myoclonus, cortical blindness, akinetic mutism and LMN signs
282
Mean onset age and survival time of sporadic CJD
Onset - 25-75 years
| Survival - <6 months of symptom onset
283
Variant CJD (acquired) cause and presentation
Cause - exposure to bovine spongiform encephalopathy (BSE)
Presentation
• Psychiatric symptoms (anxiety, paranoia, hallucinations)
• Followed by development of neurological symptoms
• Late - chorea, ataxia, dementia
284
Mean onset age and survival time of vCJD
Onset - 30 years
| Survival - 14 months
285
Iatrogenic CJD (acquired) cause and presentation
Cause - inoculation with human prions, most commonly from surgery
Presentation - progressive ataxia, then dementia and myoclonus. Faster if CNS inoculation.
286
Kuru CJD (acquired) cause and presentation
Cause - cannibalism
Presentation - progressive cerebellar syndrome (2 year survival) following 45 year incubation. Late or absent dementia.
287
What type of prion disease is Gerstmann-Straussler-Scheinker syndrome?
Inherited
PRNP mutations
Autosomal dominant
288
How does fatal familial insomnia present
Prion disease
Insomnia and paranoia
Progresses to hallucinations and weight loss, then a mute period
289
How long is survival in fatal familial insomnia?
1-18 months following symptom onset
290
Cheat sheet examples of gram positive cocci (3)
Staph
Strep
Enterococcus
291
Cheat sheet examples of gram positive rods (5)
ABCDL
* Actinomyces
* Bacillus
* Clostridium
* Diphtheria
* Listeria
(in the gut)
292
Cheat sheet examples of gram negative cocci (2)
Neisseria
| Moraxella
293
Cheat sheet examples of gram negative rods (6)
```
Enterobacteriaceae
E. coli
Salmonella
Shigella
Klebsiella
Yersinia
```
294
Cheat sheet examples of gram negative coccobacilli (4)
H. influenzae
B. pertussis
P. aeruginosa
C. trachomatis
295
Cheat sheet examples of gram negative spriochaetes (2)
Treponema pallidum e.g. syphilis
Leptospirosis borrelia e.g. Lyme disease
296
Leading cause of adult onset seizures
Tapeworm
