Infectious Diseases Flashcards
Parameters for SIRS?
Temperature above 38 or below 36. Pulse above 90 bpm RR above 20 WCC <4 or >12 Altered mental state Known/suspected neutropenia
NEWS score of what plus infection = sepsis
more than or equal to 5
Standard oral/IV dose of amoxicillin?
Oral: 1g TDS
IV: 1g TDS
Standard oral/IV dose of co-trimoxazole?
Oral + IV: 960mg BD
Standard oral/IV dose of co-amoxiclav?
Oral: 625 mg TDs
IV: 1g TDS
Clarithromycin - interactions/biggest risk?
Interactions: statins
Biggest risk: ?prolongs QT
Standard oral/IV dose of clarithromycin?
Oral + IV: 500mg BD
Standard oral/IV dose of metronidazole?
Oral: 400mg TDS
IV: 500mg TDS
Standard oral/IV dose of flucoxacillin?
Oral: 1g QDS
IV: 1-2g QDS
Treatment for meningitis?
IV ceftriaxone 2g BD + IV dexamethasone 10mg QDS for four days
Treatment for encephalitis?
IV ceftriaxone 2g BD + IV dexamethasone 10mg QDS for four days plus aciclovir (IV 10mg/kg tads)
Treatment for meningitis if over 60 or immunocompromised?
IV ceftriaxone 2g BD + IV amoxicillin 2g/4 hours + IV dexamethasone 10mg QDS for four days
Treatment for epiglottitis/supraglottitis?
IV ceftriaxone 2g OD
Treatment for CAP 0-2?
IV/PO amoxicillin 1g TDS for 5 days
Treatment for CAP 0-2 if penicillin allergic?
PO Doxycyline 200mg day one then 100mg OD
or IV clarity if NBM
Treatment for CAP 3-5?
IV co-amoxiclav 1.2g TDS _ PO doxycyline 100mg BD for 7 days
Treatment for CAP 3-5 if penicillin allergic?
IV levofloxacin 500mg BD for 7 days
IF severe CAP and in HDU/ICU? or if NBM?
Swap the doxycycline for IV clarithromycin 500mg BD.
Treatment for severe hospital acquired pneumonia or aspiration pneumonia?
IV amoxicillin + metronidazole + gentamicin -> PO co-trimoxazole + met (7 days)
Treatment for severe hospital acquired pneumonia or aspiration pneumonia if penicillin allergic?
IV co-trimoxazole and metronidazole +/- gent.
Not severe HAP or aspiration pneumonia?
PO amoxicillin and metronidazole (5 days)
If penicillin allergic - swap for co-trimoxazole
Acute COPD exacerbation?
Only if increase in sputum purulence give abx. Amoxicillin 500mg TDS or Doxycyline 200mg then 100mg OD (5 days)
Acute bronchitis?
Only real in frail elderly - same as acute COPD
Tx for severe native valve endocarditis (acute)?
IV flucloxacillin 2g 6 hourly (4 hourly if >85 kg)
Tx for indolent native valve endocarditis (subacute)?
IV amoxicillin 2g 4 hourly _ Gentamicin 1mg/kg BD
Tx for prosthetic valve endocarditis or MRSA?
IV vancomycin + PO rifampicin 600mg BD + IV Gentamicin 1mg/kg BD
Tx for non-severe C diff?
PO metronidazole 400mg TDS (10 days)
Tx for severe C diff?
PO/NG vancomycin 125mg QDS
+/- IV metronidazole (10 days)
Tx for peritonitis/acute biliary tract infection/intra-abdominal infection?
IV amox + met + gent
7-10 days
Mild proven spontaneous bacterial peritonitis?
PO co-trimoxazole
no symptoms
Severe proven spontaneous bacterial peritonitis?
IV piperacillin/tazobactam 4.5gTDS
Tx for uncomplicated female lower UTI?
PO nitrofurantoin 500mg QDS OR MR 100mg BD
OR Trimethoprim 200mg BD for three days (3)
Tx for uncatheterised male UTI
PO nitrofurantoin 500mg QDS OR MR 100mg BD
OR Trimethoprim 200mg BD for seven days (7)
Tx for complicated UTI/pyelonephritis/urosepsis
IV amox + gent (if p allergic - IC co-trimoxazole + gent) with step down as improving. Total: 7 days
Tx for cellulitis?
IV/PO flucloxacillin 1g QDS
If p allergic - doxycyline 100mg BD PO
Tx for mild diabetic foot infection?
Fluclox 1g QDS or Doxycyline 100mg BD (7 days)
Tx for severe diabetic foot infection?
Fluclox 1g QDS + metronidazole 400mg TDS (7 days)
OR replace fluclox with doxyxcyline 100mg BD if PA
Tx for acute septic arthritis or osteomyelitis?
Seek ID advice but 2g IV fluclox
Tx for open fracture prophylaxis?
IV co-amoxiclav 1.2g TDS
Start within 3 hours for max 72 hours.
If PA - IV co-trimoxazole 960mg BD + metronidazole 500mg TDS
Empirical treatment for unknown source of infection?
IV amox + met + gent (add in fluclox/vanc if worried re staph)
If PA - IV vancomycin + met + gent
Which groups of antibiotics act on the bacterial cell wall?
Penicillins
Cephalosporins
Glycopeptides
MoA of penicillins?
Bactericidal, inhibits cell wall synthesis through: preventing cross linking
of peptidoglycans and autolysins -> which degrade the cell wall.
Excreted via kidneys.
Safe in pregnancy.
MoA of cephalosporins?
Bactericidal, inhibits cell wall synthesis through: preventing cross linking
of peptidoglycans and autolysins -> which degrade the cell wall.
Excreted via kidneys.
Safe in pregnancy.
(ceph/cef)
MoA of glycopeptides
Bacteriacidal, binds to end of growing pentapeptide chain during peptidoglycan synthesis - preventing cross-linking.
NB - only absorbed via IV
Examples of glycopeptides?
Vancomycin, teicoplanin.
Cover from glycopeptides?
ONLY gram positive
When is only case of giving oral vancomycin?
C diff - acts locally within gut.
Which antibiotics are bacteriostatic/act on protein synthesis?
Macrolides (ycins), aminoglycosides (gentamicin) and others - clindamycin, chloramphenicol, tetracylcines
Examples of macrolides?
Erythromycin, clarithromycin and azithromycin
How are macrolides excreted? When useful?
Liver, biliary tract and into the gut. Lipophilic - good for hiding bacteria within cells.
Which of the antibiotics that inhibit protein synthesis are bactericidal?
Gentamicin - aminoglycoside.
What is gentamicin active against?
Gram negative aerobics - cloakrooms and pseudomonas aeruginosa
What is clindamycin active against/used for?
Active against: True anaerobes and staph/strep
Used for penicillin allergic patients with serious staph/strep infections
Example of tetracyclines?
Doxycyline
How are tetracyclines excreted?
Liver/biliary system
Which antibiotics act on bacterial DNA?
Metronidazole
Trimethoprim/sulphamethoxazole
Fluoroquinolones
How does metronidazole work? What is it useful for?
Causes strand breakage of bacterial DNA
Useful for true anaerobes and protozoal infections
How does trimethoprim work?
Inhibits bacterial folic acid by enzyme inhibition
Folic acid required for DNA replication
What is co-trimoxazole? Why is it useful?
Trimethoprim and sulphamethoxazole
Inhibits folic acid synthesis using 2 pathways
At what point in pregnancy is trimethoprim safe after?
4th month onwards
Cover of trimethoprim?
Gram negative and positive
MoA of fluoroquinolones?
Bacteriacidal: interact with topoisomerases (supercoil/uncoil bacterial DNA) which inhibits replication
Example of fluoroquinolone and why not used anymore
Ciprofloxacin - wide spectrum c diff risk
What used to tx pseudomonas (oral route)?
Ciprofloxacin
What is levofloxacin used of?
Severe CAP in penicillin allergic patients
Side effects of aminoglycosides?
Gentamicin damages kidneys and causes deafness/dizziness
Side effects of glycopeptides?
Vancomycin - damages kidneys/red man syndrome
Side effects of tetracyclines?
Teeth/bone staining in children under 12 (permanent)
Side effects of quinolones?
Weakens tendons - rupture
May damage joints in children
Seizures?
True penicillin allergy incidence?
<0.05%
Rashes to penicillin
1-10%
Which antibiotics safe in pregnancy?
Penicillin/cephalosporins
Which antibiotics are to be avoided in the first three months of pregnancy?
Trimethoprim
Metronidazole
Which antibiotics are not given to pregnant women?
Gentamicin
Tetracyclines
Fluoroquinolones
Two mechanisms of bacterial resistance?
Genetic mutation or
Three ways of DNA coding for resistance transferal from one bacterium to another”
Transformation/conjugation/transduction
Transformation?
From dead bacteria
Conjugation?
From plasmid replication
Transduction?
Bacterial DNA transfer via a virus (phage or bacteriophage)
Three common mechanisms of antibiotic resistance?
Altered binding site (MRSA)
Antibiotic destruction (beta-lactamases/cephalosporinases - target beta-lactam ring)
Increased efflux
Primary care management of suspected meningitis
If time permits - IV/IM benxypenicillin 1.2g or 2g cefotaxime
Primary care management of conjunctivitis
Chloramphenicol
Dose for shingles?
Oral aciclovir 800mg 5 times daily
Primary care management of bacterial source tonsil/pharyngitits?
- Penicillin V 1g BD 7 days
Doxycycline 200mg, then 100mg OD 7 days
Primary care management of sinusitis of >7/10 days?
- Penicillin V 1g BD 7 days
2. Doxycycline 200mg, then 100mg OD 7 days
Primary care management of otitis media with ottorrhoea?
- Amoxicillin 500mg TDS
- Clarithromycin 5000mg BD
(Both 5 days)
Primary care management of otitis external?
Acetic acid
Primary care management of oral thrush?
- Miconazole gel QDS (avoid with warfarin)
2. Fluconazole 50mg OD
CRB65 criteria?
Confusion
Resp rate > 30
BP <90 SBP or <60 DBP
Age over 65
Primary care management of CAP?
Amoxicillin 1g TDS
Doxycyline 200mg-100mg 5 days
Primary care management of severe CAP pre-transfer to hospital?
Amoxicillin 1g oral or benzypenicillin 1.2g IV
Primary care management of diverticulitis which indicates antibiotics?
Metranidazole 400mg TDS + Co-trimoxazole 960mg BD
5 days
Primary care management of UTI in catheterised pts?
- Co-trimoxazole 960mg BD
- Co-amoxiclav 625mg TDS
(7 days)
Primary care management of uncomplicated lower female UTI?
Nitrofurantoin 50mg QDS or 100mg MRBD
OR
Trimethoprim 200mg BD (3 days)
Primary care management of pyelonephritis?
Send MSSU
Co-trimoxazole 960mg BD
OR
Co-amoxiclav 625mg TDS
Primary care management of uncatheterised male UTI?
Send MSSU
Nitrofurantoin MR 100mg BD etc
OR
Trimethoprim 200mg BD (7 days)
Primary care management of UTI or bacteriuria in pregnancy?
Send MSSU
- 1st or 2nd trimester: nitrofurantoin MR 100mg BD 3rd trimester: trimethoprim 200mg BD
- Any trimester: cefalexin 500mg TDS
Primary care management of prostatitis?
Ofloxacin 200mg BD or Ciprofloxacin 500mg BD
Primary care management of uncomplicated chlamydia?
Azithromycin 1g stat OR doxycyline 100mg BD
Primary care management of pelvic inflammatory disease?
Metronidazole 400mg BD + ofloxacin 400mg BD (14 days)
Primary care management of trichomoniasis/BV?
Metronidazole 400mg BD
Dose of flucloxacillin for cellulitis?
1g QDS (7 days)
Alternative to flucloxacillin for cellulitis?
100mg BD (7 days)
Primary care management of athletes foot?
Topical 1% terbinafine OD-BD
Primary care management of impetigo - localised/generalised?
Topical fusidic acid or:
- Flucloxacillin 500mg QDS
- Clarithromycin 500mg BD (7 days)
Primary care management of bites?
- Co-amoxiclav 625mg TDS
2. Metronidazole 400mg TDS + Doxycycline 100mg BD (7 days)
What kind of pathogen is C difficile?
Gram positive
Anaerobic
Forms spores
Motile/abx resistant
Where are the spores of C diff found?
Soils, fresh and salt water, GI tract of young animals inc humans
Which strains of C diff cause disease?
Only toxin-producing ones
Spectrum of disease with C diff?
Asymptomatic carriage
Diarrhoea/simple colitis
Pseudomembraneous colitis
Fulimant colitis
What percentage of patients suffer a relapse of symptoms following initial treatment/cure of 1 c diff infection?
20%
Hypervirulent strain of c diff?
027/NAP1/B1
30% relapse rate
Risk factors for C diff?
Antimicrobial use Increased age Prolonged hospital stay Serious underlying diseases Surgical procedures - esp bowel ops Immunocompromising conditions PPI use
Additional risk factors?
- Non-surgical gastrointestinal procedures
- Presence of a naso-gastric tube
- Stay on intensive care unit
- Long duration of antibiotic course
- Receiving multiple antibiotics
- Specific antibiotics, in particular, clindamycin, cephalosporins and penicillins
What groups of patients are we more aware of contracting C diff?
Paeds, younger adults and peripartum women
What percentage of healthy adults carry C diff?
0-4%
What percentage of hospital patients may be caring C diff asymptomatically?
50%
Healthcare associated CDI defined as:
Onset of symptoms at least 48 hours after admission or up to 4 weeks post-discharge
Community associated CDI defined as:
Onset of symptoms within 48 hours of admission or if no previous stay in hospital in past 12 weeks
What do C diff spores do in colon to prevent elimination by gut motility?
Attach!
Penetration of the mucus by flagellar movement
Role of bile and C diff spores?
Can germinate in anaerobic conditions
Role of immunoglobulins in defence against C diff?
IgA - neutralise toxins and ?prevent adhesion
Virulence factors for C diff?
- Toxins A and B
- Attachment /penetration of mucus
(flagella,
adhesions,
capsule and
extracellular enzyme) - Binary toxin CDT
- Spore production and survival
Host defences against C diff?
- Intact normal flora in the colon
- Gastric acid
- GI motility
- Innate immunity: pathogen recognition mechanisms
- Humoral immunity:
secretory immunoglobulins and
systemic immunoglobulins - Cellular immunity in gut wall.
What forms the pseudomembranes in c diff infection?
Fibrin
What do toxins A and B do?
Kill cells - B is stronger - this leads to damage of GI tract
What kind of damage to GI tract in c diff infection?
Loss of fluid by leakage through damaged mucosa
Reduced absorption across gut wall
Pseudomembranes
Gut inflam/toxic megacolon/risk of perforation
How can C diff be diagnosed?
Signs and symptoms and microbio shows no other source
OR
pseudomembraneous colitis during endoscopy/colectomy/post mortem
Rough outline of mild CDI?
Mild diarrhoea
No systemic symptoms
No raised WCC
Rough outline of moderate CDI?
Moderate diarrhoea
Raised WCC <15
Some systemic symptoms
Severe CDI?
As for moderate plus: two or more severity markers e.g. temperature >38.5 °C,
WBC>15 cell/mm3; creatinine > 1.5x baseline
Life-threatening CDI?
Hypotension
Partial/complete ileus
Toxic megacolon
CT shows severe disease
Who should be tested for C diff?
All patients over 15 with diarrhoea
Gold standard for c diff?
toxigenic culture - use antiserum?
CytoToxin Assay for detecting Toxin B
When to culture C diff?
epidemiological purposes, either during a possible outbreak or if there are apparent changes in virulence or an increase in treatment failures.
Also monitoring antibiotic resistance
famous hyper virulent cdi strain?
ribotype 027
NB higher toxin levels/resistant to flouroquinolones
Other than abx tx - what else for CDI?
Avoid opiates/antiperistaltic
Reduce/stop antimicrobials
When to operate in severe CDI?
Before lactate exceeds 5mmol/l