Infectious Diseases Flashcards
(158 cards)
1
Q
What vaccinations do splenectomy patients require?
A
Pneumovax (13PPV then 23PPV 8 weeks later, then 23PPV 5y later), HiB, meningococcal ACWY + B + annual influenza
2
Q
When are live vaccinations contraindicated?
A
Pred > 20mg daily
CD4 < 200
Primary immunodeficiency
Pregnancy
3
Q
What are the live vaccines?
A
MMR, VZV, oral polio, BCG, oral typhoid, yellow fever, JEV
4
Q
What vaccinations are contraindicated in egg anaphylaxis?
A
Q fever and yellow fever
5
Q
What organism are hyposplenic sickle cell patients predisposed to?
A
Salmonella
6
Q
What organism causes infection following dog bite?
A
Capnocytophagia
7
Q
What antibiotic for prophylaxis post-splenectomy, and for how long?
A
Phenoxymethyl penicillin or amoxicillin, at least 2 years if healthy or lifelong if previous OPSI
8
Q
Incubation period for Dengue
A
3-14 but usually 4-7 (short)
9
Q
Incubation period for Zika
A
2-14 days (short)
10
Q
Incubation period for Typhoid
A
5-21 days
11
Q
Incubation period for malaria
A
1-6 weeks (can be much longer)
12
Q
Incubation period for Ebola
A
6-12 days
13
Q
What infections cause eschar?
A
Rickettsia, plague, trypanosomiasis
14
Q
Treatment for severe falciparum malaria
A
IV artesunate, add IV quinine if from greater mekong
15
Q
What gene confers resistance to artemesinin? Where found?
A
Kolch 13, SE Asia
16
Q
What test must you do before treating vivax/ovale, and what treatment?
A
G6PD, primaquine for 7-14 days
17
Q
Mosquito species for malaria
A
Anopheles
18
Q
Treatment of non-severe malaria
A
Artemether + lumefantrine
19
Q
List 4 flaviviruses
A
Dengue, Zika, Yellow fever, JEV
20
Q
Mosquito for Dengue
A
Aedes aegypti - same as for Zika, Chikungunya
21
Q
What is ADE with regards to Dengue?
A
Antibody dependent enhancement, meaning second infection with another Dengue serotype being a risk factor for severe Dengue
22
Q
Viral protein that causes Dengue shock
A
NS1Ag
23
Q
Test for diagnosis when < 5 days of illness in Dengue
A
NS1Ag
24
Q
Diagnosis > 5 days of illness in Dengue
A
Serology
25
Who do you vaccinate against Dengue?
Seropositive individuals in endemic areas
26
What is clinical course of Dengue?
Biphasic, with defervescence of fevers after 5 days then get sick again
27
What is main complication of Zika in adults?
GBS
28
How do you diagnose Zika?
< 7 days = PCR
| > 7 days = serology
29
Name three alphaviruses
Chikungunya, Ross River Virus, BF
30
Organism causing Typhoid
Salmonella enterica, serotypes typhi, paratyphi A/B/C
31
Key skin finding for Typhoid
Rose spots
32
Empiric treatment of typhoid
Ceftriaxone or azithromycin
33
Mechanism of action of triazoles
Inhibit C14alpha demethylase which is required for ergosterol synthesis in cell membrane. Fungistatic.
34
Mechanism of action of polyenes (amphotericin)
Bind to sterol ergosterol, forming pores in membrane
35
Echinocandins MOA
Inhibit B-1,3-D glucan synthase, inhibiting cell wall synthesis. Fungicidal.
36
Griseofulvin MOA
Inhibits nuclear division
37
First line antifungal for invasive aspergillus?
Voriconazole. Second line amphotericin/echinocandins
38
What is the vector for cutaneous leishmaniasis?
Sandflies
39
What are key words for biopsy of cutaneous leish lesion?
Rod-shaped kinetoplasts
40
How does HIV attach to CD4?
Via Gp120
41
What are HIV attachment coreceptors?
CCR5 early, CXCR4 late
42
What cells are CD4 positive and susceptible to HIV
Lymphocytes, macrophages, DCs
43
Mutation that confers immunity to HIV infection
CCR5delta32
44
HLA type with slowest progression to AIDS in HIV
HLAB5701
45
What are side effects of tenofovir?
Osteoporosis and RTA. TAF less toxic than TDF due to longer plasma half-life.
46
What drug classes are used to treat HIV in general?
2x NRTI + integrase inhibitor (ends in -tegravir)
47
When should you give PEP?
Best if < 24h, no longer than 72h
48
What drugs do you give for PEP? How long?
Tenofovir, emtricitabine, integrase (dolutegravir, raltegravir). 28 days
49
What drugs for PrEP?
Tenofovir and emtricitabine
50
What are the AIDS defining illnesses?
PJP, toxoplasmosis, CMV, TB/MAC, oesophageal candidiasis, Cryptosporidium/microsporidium, Kaposi's
51
When should you start HIV treatment assuming no infection?
ASAP
52
What prophylaxis needs to be given at what CD4 counts for HIV?
< 200 PJP -> Bactrim
< 100 Toxo -> Bactrim
< 50 MAC, Crypto - Azith
53
What are RFs for IRIS?
High VL, high pathogen burden, low CD4 count
54
Top causes of IRIS?
TB, Crypto, MAC, CMV, PML
55
When to start ART with OI?
If TB and CD4 > 50, delay until 4-8 weeks of TB treatment
If TB and CD4 < 50, delay 2-4 weeks
Crypto - Delay until 4-6 weeks post amphotericin, sooner if mild and CD4 < 50
If crypto meningitis or other neurological OI - optimum time to start unclear
56
When do you treat a pregnant woman with HIV?
ASAP - risk to baby is 25% if untreated
57
WHen do you give zidovudine to pregnant woman?
If VL > 1000 at birth give IV zidovudine and deliver via C-section
58
What is ecthyma gangrenosum?
Ecthymatous skin lesions associated with Pseudomonas bacteraemia
59
Risk factors for invasive moulds?
AML, neutrophils < 0.1 for 2-3/52, neutropaenic + steroids, ALL, HSCT, cytarabine/fludarabine
60
What is Nocardia?
Gram positive rod, long chains of acid fast bacilli, branching like a mould. Causes lung and brain abscesses.
61
What is PTLD?
Post transplant lymphoproliferative disorder. High risk if EBV D+/R-, lymphoid rich transplant, ATG use.
62
What organism causes PML?
Progressive multifocal leucoencephalopathy- JC Virus (John Cunningham)
63
What drugs are highest risk for PML?
Natalizumab, TNFa inhibitors, rituximab
64
What is treatment for Stronglyoides stercoralis?
Ivermectin and repeat in 14 days
65
What are examples of yeasts?
Candida (no capsule), Cryptococcus (polysaccharide)
66
What are examples of moulds?
Aspergillus (septated hyphae), Rhizo, Mucor (non-septated)
67
How do aminoglycosides (Gentamicin, tobramycin, neomycin, kanamycin, plazomycin) and tetracyclines (doxy, minocycline, tigecycline) work?
Protein synthesis inhibitors (bind 30s)
68
How do macrolides (erythro, oxithro, azithro, clarithromycin) and chloramphenicol work?
Protein synthesis inhibitors (binds 50s)
69
How do oxazolidinones (linezolid, tedizolid) and lincosamides (clindamycin) work?
Binds to 23S portion of 50S subunit of bacterial ribosomes, inhibiting protein synthesis
70
How do colistin (Classified as polymyxin antibiotic), glycopeptides (Vancomycin, teicoplanin) and daptomycin (Lipopeptide class) work?
Cell membrane synthesis inhibitor
71
How does fusidic acid work?
Protein synthesis inhibitor, blocks factor G
72
How do quinolones work? (ciprofloxacin, moxifloxacin, levofloxacin, norfloxacin)
DNA gyrase, replication inhibitors
73
How do rifamycins work? (rifabutin, rifampin, rifapentine)
Inhibit DNA-dependent RNA synthesis by inhibiting RNA polymerase
74
How do nitrofurantoin, sulphonamides and trimethoprim work?
DNA synthesis inhibitor
75
How do beta lactams work?
Inhibit cell wall synthesis - binds to penicillin binding proteins, which are bacterial transpeptidases required for cell wall peptidoglycan assembly
76
How does metronidazole work? (Nitroimidazole class)
Free radicals fragment DNA
77
What is the only antibiotics in class monobactam?
Aztreonam - useful against gram negatives, cross-reactive allergy with ceftazidime
78
What is a new cephalosporin with MRSA cover?
Ceftaroline
79
Which 3rd generation cephalosporin has Pseudomonas cover?
Ceftazidime (like tazocin)
80
What classes of drugs are cell membrane inhibitors?
Colistin (polymyxin class), beta lactams, daptomycin, glycopeptides (vanc, teico),
81
Side effects of daptomycin?
Myopathy (check CK), eosinophilic pneumonia
82
What is the mechanism of MRSA resistance?
mecA gene producing PBP2a, low affinity for beta lactams. Must acquire this mutation from other bacteria (conjugation), isn't a sporadic mutation produced under long-term beta lactam pressure.
83
What is the Panton-Valentine Leucocidin toxin?
Exotoxin produced by particular MRSA strains, causes leucocyte destruction and tissue necrosis, and associated with skin boils, necrotising pneumonia and increasing virulence.
84
What is mechanism of resistance for VRSA?
VanA plasmid from VRE. Mutations of genes encoding for vancomycin binding site, changes from D-ala-D-ala to D-ala-D-lac
85
What is mechanism of resistance for VRE?
VanA/VanB/VanC genes, transferrable via plasmid (conjugation). More common in E. faecium than E. faecalis
86
What are the ESCAPPM organisms?
Enterobacter, Serratia, Citrobacter koseri, Acinetobacter and Aeromonas, Proteus vulgaris, Providencia, Morganella morganii
87
What is the NDM-1 enzyme with regards to Enterobacteriaceae?
New Delhi Metallo-beta-lactamase-1, a beta lactamase that hydrolyses carbapenems, rendering Enterobacteriaceae resistant to carbapenems. Produced by gene blaNDM-1, transferred via plasmids.
88
What are ESBLs?
Gram neg organisms (E. coli, Kleb) with extended spectrum beta lactamase enzymes that hydrolyses later generation cephalosporins. Treat with carbapenems. CTX-M most common gene, present on plasmids
89
How can the genes encoding for ESBLs be transferred?
Via plasmids
90
What is the mechanism of ESCAPPM organism resistance?
ampC gene, present on chromosome, encodes for beta-lactamase enzyme. Beta-lactamase production inducible in presence of beta lactams.
91
What is most common organism causing cellulitis?
Strep pyogenes or dysgalactiae, then Staph (particularly if purulent)
92
Prophylaxis for recurrent cellulitis?
Penicillin VK 250mg BD
93
Empirical treatment for nec fasc
Mero/vanc/clinda
94
Most common organisms causing meningitis over 60yo?
Pneumococcus, Listeria
95
Most common organisms causing meningitis < 60 years old?
Pneumococcus, Neisseria
96
Risk factors for Listeria meningitis?
> 50 years old, pregnant, impaired cell-mediated immunity (T2DM)
97
What organism causes recurrent aseptic/lymphocytic meningitis?
HSV-2, Mollaret's meningitis
98
Empiric therapy for meningitis?
Ceftriaxone 2g BD, dex 10mg QID. If gram pos diplococci/RF for S. pneumo, add vanc. If old/immunocompromised, add benpen.
99
When are steroids used in meningitis?
Pneumococcal meningitis
100
Most common causes of viral meningitis?
Enteroviruses, HSV1, HSV2
101
What species of Cryptococci affects immunocompromised and immunocompetent?
HIV - C. neoformans
| Immunocompetent - C. gattii
102
What serotype of N. meningitidis causes most severe infection?
B (for BAD)
| We vaccinate against ACWY
103
Who can we give meningococcal B vaccination to?
Asplenics, complement deficiencies
104
When to treat asymptomatic bacteriuria?
Pregnant, prior to procedures. NOT renal transplant
105
Most common predisposing cardiac condition for IE?
MVP with regurgitation, if no regurg then not a RF
106
Most common organism for prosthetic valve IE?
S. aureus
107
Most common organisms for IE?
S. aureus, viridans Strep, coag-negative Staph, Enterococci
108
What are HACEK organisms and their significance?
Cause IE. Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella corrodens, Kingella
109
Empiric therapy for IE?
Benpen, fluclox, gent
110
Treatment for E. faecalis IE?
Amox + ceftriaxone
111
Prophylactic antibiotics for IE, which patients? Which procedures?
Prosthetic valves, RHD, previous IE, unrepaired congenital heart disease.
Procedures - Dental/oral surgery, respiratory mucosal breaks, surgery at site of established infection.
112
Antibiotics used for IE prophylaxis?
Amoxicillin 2g or clindamycin 600mg
113
Most common organisms causing culture negative IE?
Q fever, Bartonella hensellae
114
Organisms causing pneumonia in tropical regions
Mellioidosis and acinetobacter
115
Define MDR TB
Resistance to isoniazide + rifampicin
116
Define XDR TB
Resistance to fluoroquinolone + aminoglycisides
117
Standard treatment regime for TB?
RIPE (other letters for drugs in same order = RHZE) for 2 months then RI for 4 months (rifampicin, isoniazide, ethambutol, pyrazinamide)
118
What are issues/side effects from rifampicin?
Drug interactions, hepatotoxicity
119
What are side effects of isoniazid?
Hepatotoxicity, peripheral neuropathy
120
Key side effect of ethambutol
Optic neuropathy
121
Key side effects of pyrazinamide
Hepatotoxicity, arthralgia/gout
122
Most hepatotoxic TB treatment drugs? (in order)
Pyrazinamide, isoniazid, rifampicin (RIPE backwards without the E)
123
When do you treat latent TB?
<35 years old, healthcare workers, HIV, immunosuppressed, recent acquisition
124
Options for latent TB treatment?
9H (9 months isoniazid)
4R (4 months rifampicin)
3RH (weekly rifapentine/isoniazid for 3 months)
All equally efficacious, 3RH less hepatotoxic but more hypersensitivity
125
Characteristic pathology finding for CMV infection
Owl eyes inclusions
126
Greatest risk of CMV in SOT
D+/R-
127
Greatest risk of CMV in BMT
D-/R+
128
Mechanism of CMV resistance to valgan/gan
UL97 mutation
129
Mechanism of CMV resistance to most antivirals
UL54 (alters DNA polymerase causing pan-resistance)
130
Mechanism of action of ganciclovir/valgan
Guanosine analogue, inhibit CMV DNA polymerase - utilises UL97 to be phosphorylated and activated
131
Mechanism of action of foscarnet
Pyrophosphate analogue binds directly to UL54 site on CMV DNA polymerase
132
Mechanism of action of marabavir
Inhibits UL97
133
Mechanism of action of cidofovir
Cytosine analogue
134
VZV PEP in pregnant/immunocompromised/non-immune
VZVIg if < 4/7, PO valaciclovir if > 4/7
135
Which influenza type has pandemic potential and why?
Influenza A- has 16H/9N possibilities and can undergo antigenic shift, whereas fluB only has 1H/1N and can only undergo antigenic drift
136
What type of diarrhoea does cholera cause?
Secretory
137
What is a bacterial cause of aortitis?
Salmonella; syphilis
138
What infection is most commonly associated with GBS?
Campylobacter
139
Most common STEC organism?
E. coli 0157:H7
140
Two most significant RFs for C. diff
Antibiotics and hospitalisation
141
How does C. diff cause disease?
Via toxins (Tcd A, Tcd B). A severe strain B1/NAP1/027 also produces binary toxin.
142
What is C. diff B1/NAP1/027 strain and significance?
Produces binary toxin in addition to Tcd A/B, more severe, fluoroquinolone resistant, more toxic megacolon, associated with outbreaks
143
What drugs are used to treat HBV?
Tenofovir and entecavir
144
How to prevent maternal-foetal transmission of HBV?
Treat mother with tenofovir, give baby HBVIg and vaccine
145
Why does HCV not clear while HBV does (in adults)?
HCV more error prone, mutates rapidly, evades immune system
146
Genotypes of HCV common in Aus?
1 and 3
147
Standard classes of drugs for treament of HCV?
NS5A + NS3/4 inhibitors, add ribavirin if cirrhotic
148
Neurological manifestations of HSV?
Mollaret's, encephalitis, transverse myelitis
149
Indications for HSV prophylaxis/suppression?
>6 episodes/y, Mollaret's, MSM at risk
150
What are the stages of syphillis infection?
Primary = chancre
Secondary = skin lesions (mostly generalised maculopapular rash), maybe non-tender lymphadenopathy and fever. May have meningitis, hepatitis, osteitis, arthritis, iritis
Latent
Tertiary = gummatous, CV, or neurosyphilis
151
What are manifestations of neurosyphillis?
GPI (General Paresis of the Insane)
Tabes dorsalis
CN palsies
152
How do you diagnose syphillis?
Serology - EIA positive first, then confirm with TPPA. These stay positive for life. Then use RPR (rapid plasma reagent) which is not positive for life, therefore used to track treatment response/recurrence.
153
What is successful treatment of syphillis defined as on RPR?
4 fold (2 titre) reduction in 6 months
154
Most common HPV types to cause warts?
6, 11
155
Most common HPV types to cause SCC?
16, 18
156
Treatment of Chlamydia?
Azithromycin 1g PO or doxy 100mg BD for a week
157
Treatment of gonorrhoea?
IM ceftriaxone 500mg
| + give azith 1g PO
158
What causes chancroid, and are the ulcers painful or not?
Haemophilus ducreyi, very painful ulcers. Treat azith or cef
