Infectious Diseases Flashcards
Most common cause of bacterial cellulitis
Group A/C/G strep
Cause of nec fas
Group A strep, toxin mediated Clostridium perfringens Polymicrobial - e.g. fourniers gangrene
Role of clindamycin in necrotising fasciitis
stop protein synthesis and toxin production
Cellulitis infection associated with cat bites
Pasteurella multocida - resistant to fluclox and cephazol; sensitive to amoxil and 3rd generation ceflosplorins. Need plastics involvement due to deep wound
Cellulitis associated with fish/shellfish exposure
erysipelothrix - associated with endocarditis
Clinical distinguishing feature of erysipelas
Sharp border
incubation period for falciparum malaria
7-10 days (but can have delayed presentation; especially if there’s been prophylaxis)
Immunochromographic test
Paired with a thick and thin for detection of malaria antigen (best for falciparum)
Dengue incubation period
maximum 2 weeks
What test do you do in conjunction with TB PCR in diagnosis
genexpert testing for rifampicin resistance - rifampicin resistance would suggest multi-drug resistance TB
What diagnostic investigation for pleural TB
pleural biopsy
Strongylodiasis infection - how to acquire
Usually from walking barefoot in tropical regions
What happens to eosinophils in bacterial infections
Hypooesinophilia due to TH1 activation
What is streptococcus milleri associated with
Abscess formation
Treatment for giardia
Tinidazole (then metronidazole)
What kind of bacterial is salmonella typhi
gram negative bacillus
What is the rash pattern in measles and 5 ‘c’s
starts at neck and ears and spreads down the trunk cough coryzal koplik conjunctivitis crappy
NS1 antigen
part of the dengue virus
Dengue shock syndrome - suggestive feature on FBE
rise in haematocrit due to leaking capillaries
Most common cause of liver abscess in SE Asia
Klebsiella pneumoniae (hypervirulence strain in asia)
Melioidosis
Burkholderia pseudomallei (Northen Australia)
What do you need to do before giving tafenoquine
G6PD testing (for Malaria prophylaxis)
How does beta lactamases cause resistance and what organisms are they most commonly found
Enzymatic degradation Gram -ve> gram +ve
“non multi” MRSA vs “multi” MRSA
non multi is generally community acquired still sensitive to clindamycin, bactrim this is due to resistance genes being co-transmitted (e.g. through plasmids)
What gram negative rod has an intrinsic narrow spectrum beta-lactamases
Klebsiella (but wildtype should be susceptible to augmentin, ceftriaxone etc)
What gram negatives have chromosomal mediated (sometimes expressed) beta lactamases
ESCAPPM E: Enterobacter spp. S: Serratia spp. C: Citrobacter freundii. H: Hafnia spp. Cannot use 2rd gen cephalosporin for >48hr. The beta lactamase is inducible. The enzyme is called AmpC
What gram negatives have an intrinsic resistance to carbapenems
Stenotrophomonas But not very pathogenic
what is a common mutation for quinolone resistance?
fluoroquinolone gyrA mutation
Long term bug lines
gram positive, sticky gram negatives (pseudomonas), candida
Where does tigecycline distribute to
It is poorly protein bound so serum levels are low but can distribute well into tissues. Not good for bacteraemia.
What empirical therapy should be used in suspected CPE
Meropenem 2g TDS PLUS aminoglycoside (amikacin) OR colistin PLUS fosfomycin IV or tigecycline
What class of drug is colistin
polymixin
What bug implicated in severe mucositis
VRE/enterococcus
What enterococcus species is more likely to be resistant
Entercoccus faecium The other common enterococcus is faecalis
Linezolid side effects
myelosuppression peripheral neuropathy optic issues
Should beta lactams have peak concentrations or more time above MIC?
More time above MIC. Aim for >50% (but more is better). Beta lactams do better w more frequent dosing
Micro associated w ethmoid surgery
Pneumococcal
What antibotics can cause prolonged INR
erythromycin
What does bactrim do to the kidneys
inhibits tubular secretion of potassium and creatinine
What kind of HIV drug is ritonavir
Booster drug (often used w/ protease inhibitors)
What does ritonavir do to methadone
Decrease plasma methadone concentration
What is panton-valentine Leucocidin toxin most associated with
pyogenic skin infections community acquired MRSA
group D strep (strep gallolyticus/bovis) - what malignancy is it associated with
colon cancer
most common organism associated with IVDU IE
staph aureus
what heart disease does streptococcus pyogenes
rheumatic heart disease - M protein
What are HACEK organisms susceptible to
ceftriaxone
When is the best time to take blood cultures
before the febrile episode
What is the most common valvular lesion predisposing to infective endocarditis
mitral valve prolapse (but mitral stenosis in places w rheumatic fever)
what kind of valves should get antibiotic prophylaxis for dental procedures
prosthetic valves
what is the main risk factor for C. Diff infection
advancing age
c. diff binary toxin
very virulent c. diff toxin more likely to cause toxic megacolon
what causes a pandemic flu in influenzae A
Antigenic shift in H and N proteins of influenzae A
what is a neuraminidase
osteltamivir
wht is the greatest risk factor for severe respiratory disease asosicated with the 2009 H1N1 swine flu
BMI >35 second biggest is pregnancy
what haematological condition is mycoplasma pneumonia associated with
cold agglutinin haemolysis
what is the most treatment option most likely to improve chronic fatigue
material explaining chronic fatigue supervised graded exercise program is next
prevention of rheumatic fever recurrence in young patients with rheumatic heart disease
secondary prophylaxis with benzathine penicillin G 3 weekly
the most common cause of viral meningitis
enterovirus
what is the most common cause of recurrent meningitis
HSV2
the most common cause of viral meningitis
enterovirus
what is the most common cause of recurrent meningitis
HSV2
What opportunistic infections are likely to occur in a HIV patient with CD4 200-500
Herpes zoster, pneumococcal pneumonia, oral candidiasis, tuberculosis
What and when should primary prophylaxis be initiated in HIV
CD4 <200 PJP and CNS toxoplasmosis - cotrimoxazole
CD4 <50 MAC - azithromycin
When to start ART in the symptomatic HIV patient or CD4 <200 (OI, TB)
- Investigate and commence treatment for OI
- Commence ART 2-4 weeks later (or earlier)
- TB and CD4 >50 - do not start ART until 4-8 weeks of TB treatment
- TB and CD <50 - initiate ART at 2-4 weeks
- If cryptococcal meningitis or other neurological OP - unclear evidence
Steps in HIV viral life cycle
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Adverse effects of tenofovir
Renal fx; Osteopenia
MOA of tenofovir
nucleotide analogue
what is the renal function cut off in tenofovir
CrCl <30 mL/min
What HIV medications are used as boosters?
Ritonavir (PI) and colbistat (CYP3A4 inhibitor)
What HIV ARTs cause dyslipidaemia?
Protease inhibitors
Atazanavir (ATZ)
Darunavir (DRV)
Lopinavir/ritonavir (LPV/rtv)
Recommended initial regimens for most people with HIV (2)
BIC/TAF/FTC - two NRTIs and an INSTI (Bictegravir, tenofivir, Emtricitabine)
DTG/ABC/3TC (if HLA-B*5701 negative) - abacavir (ABC)/lamivudine (3TC)/dolutegravir
What HIV mediations are metabolised by CYP4503A4
Protease inhibitors (inhibits P450 3A4) and NNRTI (induces CYP P4504A4)
What is virologic failure in HIV?
Inability to maintain suppression of viral replication (to an HIV RNA level <200 copies/mL)
When should testing for drug resistane be done in HIV patients
All at baseline and for all pregnant women
At virologic failure
what HIV ARTs leads to lipoatrophy
stavudine or zidovudine (Old NRTIs)
what HIV ARTs cause visceral fat accumulation and buffalo hump ?
Protease inhibitor use
PBS listed PrEP
Tenofovir + emtricitabine (TDF + FTC)
What respiratory OI is a HIV patient at risk of if CD4 <50
MAC, CMV pneumonitis (and all the other stuff at higher CD4 counts)
Typical PJP CXR findings
diffuse bilateral, symmetrical interstitial infiltrates
CT - diffuse groundglass changes
Cryptococcis treatment
liposomal amphotericin B 3 mg/kg IV daily + flucytosine 25 mg/kg QID (flucytosine rarely tolerated, levels must be monitored) – 2-3 weeks
Need repeat LP to check clearance
What is the most common cause of death in AIDS patients worldwide
TB
Treatment of disseminated MAC
Clarithromycin + ethambutol
CMV in HIV most common clinical manifestation of CMV end organ disease
retinitis
Kaposi sarcoma viral aetiology
HHV 8
Which HIV strain is more predominent
HIV 1 by far
Differences between HIV 1 and 2
- Distribution
- Viral load
- CD4+ counts in undetectable viral load
- Coreceptor use
- Ineffective HRT
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What is the MOA of maraviroc?
inhibits CCR5 binding (entry)
What is the MOA of enfuviritide
HIV drug - inhibits fusion of the HIV onto the host cell
MOA of abacavir
NRTI
MOA of lamivudine
NRTI
MOA of emtricitabine
NRTI
MOA of zidovudine
NRTI
MOA of raltegravir
Integrase inhibitor
MOA dolutegravir
InSTIs
HIV entry co-receptors
CCR5 co-receptor; CXCR4 co-receptor]
CCR5 is present on many types of cells
What is immune activation associated with in HIV
Increased mortality and morbidity
Increased atherosclerosis
Poor CD4 recovery
What mutation is assocaited with HIV protection
Delta32 mutation in CCR5
What is control of MTB dependent on?
T-cell immunity, IFNgamma, TNFalpha
What is the second most common manifestation of active TB?
Tuberculosis lymphadenitiis
Treatment of TB meningitis
isoniazid (H), rifampicin (R), pyrazinamide (Z) + moxifloxacin
Standard course therapy for TB
RIPE for 2 months
RI for 4 months
What component of the RIPE therapy is best at killing rapidly multiplying bacteria
isoniazid
What TB medication is most likely to cause hepatitis
pyrazinamide
what TB drug is most likely to cause neuropathy
isoniazid
What TB drug is associated with optic neuropathy?
Ethambutol
Management of TB therapy induced hepatitis
If 2-5x normal, asymptomatic, monitor closely
If >5x normal, or >3x and symptoms, cease
What is the most common non-drug resistance in TB?
Isonaizid
rifampicin and CYP3A4
induces CYP3A4
What is contraindicated with rifamycin?
tenofivir alafenamide (tenofivir disproxil fumarate ok)
bictegraivir
elvitegravir
protease inhibitors are contraindicated with rifampicin but can be taken with a dose reduced rifabutin
What is the MOA of echinocandins and what are examples of them
Cell wall beta (1, 3) - glucan synthesis inhibitors
e.g. Caspofungin, anidulafungin, micafungin
What is the MOA of triazoles? (and examples)
endoplasmic reticulum ergosterol biosynthesis inhibitors:
- Inhibits C-14alpha demethylase required for ergosterol synthesis
e. g. fluconazole, itraconazole, voriconazole, posaconazole, ravuconazole
What is the MOA of amphotericine
plasmalemma ergosterol plasma membrane integrity
pharmacokinetics of conventional amphotericin B
Unknown - not affected by the hepatic or renal system and haemodialysis does not alter blood concentrations
BUT can cause nephrotoxocity
What is the clinical use of conventional amphotericin B
Not widely available in Australia:
- Selected cases of invasive candidiasis
- Cryptococcal meningitis (now L-AMB is first line)
- Empiric therapy in selected cases
Pros: broad spectrum of activity and resistance is slow to develop
Cons: drug toxicities limit efficacy/response
What is the general preferred polyene (antifungal)
Liposomal amphotericin B (compared with conventional amphotericin B):
- Less nephrotoxic
- Less infusion related side effects
- Similar efficacy
What is the indication for inhaled amphotericin B?
- Prophylaxis in lung transplant patients
- Occasionally in the haematology population if oral antifungals are contra-indicated and cannot have IV ampotericin B
Which anti-fungal has increased affinity for aspergillus?
Voriconazole - because it has the addition of a methyl group to propyl backbond of fluconazole and the substitution of a triazole moiety with a fluoropyrimidine group.
This results in an increased afinity for the 14-alpha-sterol demethylase enzyme in Aspergillus
Voriconazole toxicities
Elevation of LFTs
Photosensitive rash
Transient dose related visual disturbance in 8-10%
1st line therapy for definite or probably invasive aspergillosis
1st line - Voriconazole IV
2nd line - LAB
Initial therapy for candidaemia
- Candida albicans
- Other candida species
- Critically ill candidaemia
- fluconazole
- anidulafungin
- anidulafungin
subacute endocarditis most common organisms
viridans streptococci (17% of all IE)
Enterococcus faecalis (11 of all IE)
IVDU with pneumonia differential
infective endocarditis
(75% of R) IE have pneumonia/infective pulmnonary emboli)
what is a key cause of culture negative infective endocarditis and what is the next investigation to do?
Q fever - serology
others: bartonella, tropheryma whipplei, psittacosis, brucellosis
Viridans strep subacute endocarditis treatment
2 weeks IV penicillin + 2 weeks IV gentamicin or 4 weeks IV penicillin
Use vanc if MIC >2mg/L
Treatment of enterococcal infective endocarditis
4-6 weeks of IV penicillin or amoxil/amp + gent
Treatment of staph IE
MSSA: 4-6 weeks of IV fluclox/1st gen cephalosporin
MRSA: Vanc 4-6 weeks
Uncomplicated tricuspid valve endocarditis treatment
2 weeks IV fluclox + gent
4 weeks if complicated (e.g. lung lesions, prosthesis, L side involvement)
Treatment of culture negative endocarditis
ceftriaxone 3-4 weeks + gentamicin 2 weeks
Indications for surgery in infective endocarditis
- Heart failure
- Paravalvular exdension
- Uncontrolled infection/difficult organism (persistent bacteraenia >10 days despite appropriate antibiotics; fungal/brucella/pseudomonas)
- Recurrent embolic events despite appropriate antibiotics
Mean time to PJP after transplant
~20 weeks
Incubation period typhoid fever
up to 21 days
First line uncomplicated malasia
artemether-lumefantrine (po)
send line atovaquone-proguanil
adverse effects of artesunate
cerebellar ataxia, abdo pain/diarrhoea, increased ALT, delayed haemolysis
SE quinine
hypoglycaemia, hearing loss, increased QT, diarrhoea
Severe malaria treatment
IV artesunate
mutation assocaited with artesunate resistance
single point mutation in propellar region of P falciparum kelch protein on chromosome 13
Treatment for travellers’ diarrhoea
mild diarrhoea - symptom management alone
blood, mucus, unwell, profuse diarrhoea then use antibiotics:
- azithromycin 1g stat or 500mg daily for 2 days
- Cipro 500mg bd for 2 days
Treatment of giardia lamblia
tinidazole 2g orally stat
zika and timing of conception/pregnancy
3 months for men, 8 weeks for women
what fetal deformity does zika cause and which trimester is associated with the highest risk?
microcephaly, trimester 1
4 criteria for dengue haemorrhagic fever
fever/recent history of acute fever
haemorrhagic anifestations
low platelet count <100
objective evidence of leaky capillaries
What classes of drug inhibit the 30S ribosomal sub-unit?
aminoglycosides and tetracyclines
What is the mechanism of resistance for MSSA
alteration to the penicillin binding site
second gen cephalosporins examples and coverage
cefoxitin, cefotetan, cefuroxime
gram +ve, enterbacter, klebsiella, H. influenzae
what aminoglycoside is the worst for hearing?
amikacin
what antibiotic causes orange-pink discolouration of the urine?
rifamycins
what antibiotic can cause irreversibe aplastic anaemia with toxicity
chloramphenicol
MOA of linezolid
23S ribosomal RNA of the 50S subunit of the bacterial ribosome and prevents the formation of a functional 70S initiation complex which is an essential component of the bacterial translation process
MOA daptomycin
binds to bacterial membranes and causes a rapid depolarisation of membrane potential in both growing and stationary phase cells. This loss of membrane potential causes inhibition of protein, DNA and RNA synthesis. This results in bacterial cell death with negligible cell lysis
what are enterococci intrinsicly resistant to?
cephalosplorins
what’s the difference in cover for meropenem vs ertapenem
ertapenem has no pseudomonal cover
how are beta lactams excreted
renally excreted (except ceftriaxone)
what kind of VRE can teicoplanin treat
van B
what site of infection should daptomycin not be used?
lung - due to surfactant
linezolid SE
marrow suppression
peripheral neuropathy
dose and duration dependent - so try to keep duration <2 weeks and monitor for SE
clinda spectrum of activity
gram positives and anaerobes
difference in spectrum of activity between ciprofloxacin and moxifloxacin
cipro has pseudomonas
moxi has strep and anaerobes
what broad spectrum antibiotic has poor protein carriage and what are the clinical indications
tigecyclines - not good for bacteraemias
what gram positive directed antibiotic is effective at managing biofilms and what are the clinical indications
rifampicin - good for prosthetic joints