Infectious Diseases Flashcards
High Yield Acronyms/Antibiotics
ESBL – eg E. coli, Klebsiella Rx: Carbapenem, TMP-SMX, FQ, AG (if sensitive)
CPE Rx: Colistin, AG, Tigecycline, Call ID (TMP-SMX or FQ if lucky)
MRSA Rx: Vancomycin, Doxycycline, TMP-SMX, Clindamycin, Linezolid, Daptomycin,
Ceftobiprole
Pseudomonas Rx: Pip/Tazo, Ceftazidime, Cefepime, Imipenem, Meropenem,
Ciprofloxacin, AG, Aztreonam, Colistin, Tigecycline, Ceftazidime-Avibactam,
Ceftolozane-tazobactam
Enterococcus Rx: Ampicillin (if S) or Vanco (not VRE), Linezolid, Daptomycin
Meningitis vs encephalitis ?
MEN:
Predominantly starts with headache,
neck stiffness and fever and can get
altered LOC later into course.
JAMA: Does this adult patient have acute meningitis?
– Meningitis ruled out (99%) if fever, neck stiffness and altered MS all absent
– Jolt accentuation – high sensitivity (97% in one study)
– Kernig’s and Brudzinski’s signs – high specificity, poor sensitivity
* Basal skull meningitis:
– + CN palsies, long-tract signs
– Think TB, Listeria, Cryptococcus, Syphilis, Lyme in correct host
Enceph:
Predominantly starts with altered
LOC/mental status and fever and can
get seizures, focal neurological
changes associated.
Meningitis – Pathogens + Rx
18-50 years -S. pneumoniae, N. meningitidis, H. influenzae
TX =
Vancomycin + Ceftriaxone
> 50 years or
immunocompromised
S. pneumo, N. meningitidis,
H. influenzae, L. monocytogenes
TX:
Vancomycin + Ceftriaxone
+ Ampicillin
***In case of PCN allergy, use Vancomycin + Moxifloxacin +/- TMP-SMX (if Listeria coverage needed)
Empiric VANCO = 15-20mg/kg IV q12h, consult pharmacy for dose adjustments
CSF Gram stains
Gram-positive diplococci → S. pneumoniae
Gram-negative diplococci → N. meningitidis
Gram-negative bacilli or coccobacilli à H. flu
Gram-positive bacilli → L. monocytogenes
Bug specific tx of meningitis
S. pneumoniae :Pen G 4MU IV q4h or
CTX 2g IV q12h 10-14 days Abx
DEX x 4 days
N.meningitidis
H. Flu -CTX 2g IV q12h 4-7 days
L.monocytogenes =Ampicillin 2g IV q4h 21 days
Meningitis - Steroids
Dexamethasone 10 mg IV q6h for 4 days PRIOR TO or WITH first dose of antibiotics ( only use in strep pneumonia)
General approach:
* Administer before or with first dose of empiric antibiotics for suspected
bacterial meningitis
* Stop if CSF is non-turbid OR low cell count OR non-pneumococcal by culture
* Do not start if antibiotics have already been given to patient
Neisseria meningitis – CHEMOprophylaxis
Who?
– Household contacts
– Persons sharing sleeping arrangements
– Persons who have direct nose/mouth contamination w oral/nasal secretions
– Children and staff in childcare or nursery
– HCWs who have had intensive unprotected contact (without wearing a mask) (eg. intubating, resuscitating, closely examining oropharynx)
– Airline passengers sitting immediately on either side of the case (but not across the
aisle) when total time on aircraft > 8 hours
* When?
– Within 10 days usually
* What?
– Ciprofloxacin 500mg PO X 1 dose (increasing resistance concern)
– OR ceftriaxone 250mg IM X 1 dose
– OR rifampin 600mg PO BID X 2d
N. meningitis – IMMUNOprophylaxis
Who?
– Household contacts of a case of invasive
meningococcal disease (IMD)
– Persons sharing sleeping arrangements with a case
of IMD
– Persons who have direct nose/mouth contamination
with oral/nasal secretions of a case with IMD
– Children and staff in contact with a case of IMD in
childcare or nursery school facilities
* What?
– Depends on serotype of index case and
age/underlying conditions of contact
– Men-C-ACYW or 4CMenB can be considered
Healthcare–Associated
Ventriculitis & Meningitis
Signs and Symptoms
* New headache, nausea, lethargy, altered LOC
* Erythema and pain over SC shunt tubing
Investigations
* Blood cultures, CSF culture including fungal culture (hold for 10 days)
Management
1. Complete removal of infected CSF shunt / hardware, replaced with external drain
2. Empiric Treatment: Vancomycin PLUS Ceftazidime OR Meropenem
– +/- Rifampin (if staphylococcal isolate)
– +/- intraventricular Abx if no response to systemic Abx
3. Repeat CSF cultures to confirm negative growth
– Duration of therapy 10-14 (gram positives) up to 21 days (gram negatives) from last positive culture
4. Reimplantation of new shunt once repeat CSF culture have been negative for 7-10 days
Infective Endocarditis- diagnostic work-up
Diagnostic workup
– at least 2 sets of blood cultures prior to antibiotics (3 in 2015 IE statement)
– Initial TTE for everyone.
* TEE Class I indications: TTE nondiagnostic or IE complications suspected or intracardiac
leads (TEE widely used these are just the Class I – eg consider if staphylococcal,
enterococcal, fungal infections)
In patients being considered for an early change to oral antibiotic therapy
for treatment of stable IE, baseline TEE before switching to Oral and repeat
TEE 1-3 days before completing antibiotic regimen should be performed
IE – Diagnosis (Duke Criteria)
MAJOR (M)
Microbiological Evidence
A) Microbiologic Criteria (≥1 of):
- ≥2 BCx with typical organisms:
- S. aureus/lugdunensis, Streptococci (except GAS or pneumo), E.
Faecalis, HACEK, Granulicatella, Abiotrophia, Gemella in Native Valve
- ≥3 BCx with occasional/rare organisms
- Blood PCR for Coxiella, Bartonella, T. whipplei
- Coxiella burnetii in 1 BCx or IgG > 1:800
- Bartonella henselae or quintana IgG > 1:800
B) Imaging Criteria
- Echo or Cardiac CT: vegetation, valve/leaflet perforation or
aneurysm, abscess, pseudoaneurysm, fistula, prosthetic valve
dehiscence or New significant valvular regurgitation
- PET: Abnormal activity of valve, aortic graft, or intracardiac leads
C) Surgical Criteria
- Evidence of IE by direct inspection during surgery
Minior:
Predisposition: Prior IE, Prosthetic Valve, Prior Valve Repair, Congenital
heart disease, Regurgitation/Stenosis, Pacemaker/ICD, HOCM, IDU
Fever: Documented temp >38
Vascular Phenomena: Arterial emboli, septic pulmonary infarcts,
cerebral or splenic abscess, mycotic aneurysm, ICH, conjunctival
hemorrhage, Janeway lesion, purulent purpura
Immunologic Phenomena: Rheumatoid Factor, Osler Nodes, Roth
Spots, immune-complex GN
Microbiologic Evidence: BCx for organism consistent with IE not
meeting major criteria, BCx/PCR with organism consistent with IE from
sterile body site, PCR for skin bacteria on valve/wire
Imaging Criteria: Abnormal activity on PET within 3m of implant of
prosthetic valve, aortic graft, intracardiac leads, prosthetic material
Physical Exam Criteria: New Valve regurgitation on auscultation
DEFINITE IE
- Microorganism identified on vegetation/valve
- 2M OR 1M+3m OR 5m criteria
POSSIBLE IE
- 1M+1m OR 3m criteria
REJECTED IE
- Alternative Diagnosis
- Lack of recurrence with <4d Abx
- Negative pathology with <4d Abx
- Does not meet Possible IE criteria
IE – Treatment New Class IIb recommendation in 2021
In patients with left sided IE caused by Streptococcus, E. faecalis, S. aureus or CNST
deemed stable by the multi-D team. Team after initial IV antibiotics, a change to
oral abx therapy may be considered if:
– TEE before the switch to oral therapy shows no paravalvular infection AND
– Frequent and appropriate follow-up can be assured by the care team, AND
– If a follow-up TEE can be performed 1-3 days before the completion of the abx course.
IE - Prophylaxis
Patient population :
Prosthetic cardiac valve (including TAVI,
devices e.g. annuloplasty ring, clips, LVAD)
*Not indicated for PPM/ICD, coronary stent
Previous IE
Congenital Heart Disease
Cyanotic CHD, unrepaired
- CHD repair with patch/prosthetic within 6
months
- CHD with residual defect near
patch/prosthetic
Cardiac transplantation recipients who
develop cardiac valvulopathy
Dental procedures involving gingival manipulation,
manipulation of the periapical tissue and perforation of oral mucosa
Respiratory tract procedures WITH transection of resp mucosa eg tonsillectomy , adeniodectomy
Any piercing of infected skin (e.g. biopsy of rash)
Regimen (give 30-60 min before dental or respiratory procedures procedure):
- Amoxicillin 2g PO x1, NPO → Ampicillin 2g IV/IM OR cefazolin/ceftriaxone 1 g IV/IM
- PCN allergy → Cephalexin 2g PO OR azithro 500mg PO OR doxycycline 100mg PO
- NPO + PCN allergy → Cefazolin/ceftriaxone 1g IV/IM - For skin and respiratory tract procedures, consider which what organism may be causing specific
Community Acquired
Pneumonia (CAP)- Pathogens
Common pathogens:
– S. pneumoniae (most common)
– M. pneumoniae
– C. pneumoniae
– H. influenzae
– Respiratory viruses (Influenza,
RSV, parainfluenza, rhinovirus,
adenovirus, coronaviruses…)
- Severe disease
– Legionella pneumophila
In patients with increasing comorbidities,
antibiotic and hospital exposures:
– Increasing gram negatives e.g. K. pneumoniae,
Pseudomonas (PsA)
– S. aureus (including MRSA)
* post-influenza pneumonia
CAP – Diagnostics
Do not obtain sputum or blood C&S on outpatients (yield low)
- Consider for inpatients if severe CAP / intubated/ being treated empirically for MRSA or
Pseudomonas
- Consider urine pneumococcal + legionella Ag +/- lower tract Legionella NAAT in severe
CAP or when indicated by epidemiological factors (e.g. outbreak)
- Send rapid influenza molecular assay (NAAT) when influenza virus is circulating in
community
- In severe CAP or immunocompromised patients, can also send NAAT for non-influenza viruses
CAP – Outpatient Treatment
Healthy outpatients without comorbidities or risk factors
– Amoxicillin 1 g TID (strong, moderate)
– Doxycycline 100 mg BID (conditional, low)
– Azithromycin 500 mg and then 250 mg (or Clarithromycin) - only in areas with pneumococcal
resistance < 25% (conditional, moderate)
* Not appropriate for majority of Canada
Outpatients with comorbidities (chronic heart, lung, liver, renal, diabetes, alcoholism, malignancy, or asplenia)
– Amox-clav OR Cephalosporin (Cefpodoxime, cefuroxime) PLUS macrolide (strong, moderate)
OR Doxy (conditional, low)
– Resp FQ ie. levofloxacin/moxifloxacin(strong, moderate)
CAP – Inpatient Treatment
Inpatients, non-severe, without risk factors for MRSA or PsA
– Beta-lactam (CTX, amp-sulbactam, cefotaxime, or ceftaroline) PLUS Macrolide (strong, high).
* Beta-lactam + Doxy is a third line option as alternative if unable to macrolide or FQ (conditional, low), but this is not first line because legionella has higher rates of resistance to doxycycline than Macrolide or FQ
– Resp FQ (levofloxacin, moxifloxacin)
Inpatients, severe CAP, without risk factors for MRSA or PsA
– Beta-lactam PLUS Macrolide (strong, moderate)
– Beta-lactam PLUS Resp FQ (strong, low)
* Evidence that macrolide containing combination had lower risk of death, and evidence that combination
of beta-lactam and Resp FQ had higher mortality (but poor quality evidence/small number of
observational trials)
- Aspiration Pneumonia – recommend AGAINST adding empiric anaerobic coverage
unless empyema or abscess present (conditional, low quality)
CAP – Other
Consider MRSA coverage based upon local risk factors
– Vancomycin 15 mg/kg IV q12h or linezolid 600 mg q12h
– Consider severe post-influenza pneumonia, mechanical ventilation/ICU, significant recent antibiotic
Consider Pseudomonas coverage based upon locally validated risk factors
– Pip-Tazo or Cefepime 2g q8h or Ceftaz 2g q8h or Aztreonam or Meropenem 1g q8h
– Usually recent mechanical ventilation OR prior isolation of organism.
Transition to PO
– Hemodynamically stable, improving, tolerated PO/absorbing from GI
Duration of Treatment – 5 days if afebrile x 48 hrs with ≤ 1 sign of CAP clinical instability (HR>100, RR>24, SBP<90, paO2<90%,
can take PO, normal mental status)
Steroids? – No longer recommended unless refractory shock
HAP/VAP- pathogens
Microbiology
* Core pathogens = S. pneumoniae,
MSSA, H. influenzae, GNB including
Pseudomonas
Diagnosis
* Diagnosis based on clinical criteria alone
* Obtain non-invasive respiratory samples
* CPIS score and inflammatory markers
NOT recommended by IDSA
* Tracheobronchitis v. VAP
HAP/VAP- Empiric Treatment
Empiric Treatment: One of Column A +/- Column B +/- Column C
Column A:
Base –
Pseudomonas +
MSSA coverage
- PipTazo
- Cefepime
- Imipenem/Meropenem
- Levofloxacin*
Column B:
MRSA coverage
If risk factors for MRSA (>20%
prevalence) or mortality
- Vancomycin
- Linezolid
Column C:
2nd Anti-pseudomonal agent
(use different class than base)
If >10% resistance to base drug, or if risk factor for
Pseudomonas resistance
- Ceftazidime/Cefepime/PipTazo/Mero/Imipenem
- Ciprofloxacin/Levofloxacin
- Aminoglycoside (less preferred)
- Colistin (less preferred)
duration= 7 days
Influenza- who to test, who to treat , how to treat
When Influenza is circulating in community:
– Symptomatic outpatients if will influence
treatment
– All inpatients with acute respiratory illness
* When influenza is not circulating:
– Symptomatic inpatients with epidemiologic link to
influenza case
– Consider in high-risk patients with acute
respiratory symptoms
Who to Treat?
* Any patient hospitalized with influenza
* Any Outpatients with severe/progressive illness or risk
factors
– >65, pregnant or 2 weeks post-partum,
immunocompromise, comorbidities
* Consider in other outpatients <2 days onset or with
high-risk household members
How to treat?
* Start Neuraminidase inhibitor as soon as possible
– E.g. Oseltamivir 75mg BID for 5 days
* Benefit: Resolution of symptoms ~1 day sooner
* Harms: Nausea/vomiting
– Can treat for longer in immunocompromise or severe disease
* No steroids or immunomodulators
When to consider bacterial co-infection?
* Initial Severe disease (extensive pneumonia, respiratory failure,
hypotension)
* Deterioration after initial improvement with antivirals
* Consider if not improving with 3-5 days of antivirals
Prophylaxis:
* In institutional outbreaks, daily oseltamivir for all patients (+/- unvaccinated staff) on impacted wards until 7 days from last case
* Post-exposure prophylaxis (Oseltamivir daily x 7d) can be considered in
high-risk household contacts within 48hrs
Diarrhea: Diagnosis
Stool cultures for Salmonella, Shigella,
Campylobacter, Yersinia, STEC in patients
with diarrhea AND:
– Fever
– Bloody or mucoid stools
– Severe abdominal pain
– Sepsis
– Immunocompromise or outbreak exposure
– (V. Cholerae in large volume rice water stools)
C. difficile testing in patients with:
– Recent antibiotics
– Work in healthcare/LTC or prison
– Compatible syndrome
– IBD flare
Blood cultures in patients with:
– Immunocompromise
– Sepsis
– Suspicion of enteric fever
* Stool for Ova and Parasites in patients with:
– Diarrhea ≥ 14 days
– Immunocompromise e.g. HIV
– Travel
– Increased yield if ordered daily x 3 days
– Repeat up to 3x to increase yield if high suspicion
Diarrhea - Treatment
Empiric therapy in adults with bloody
diarrhea not recommended UNLESS:
1. Sick immunocompetent patients with
bacillary dysentery (frequent scant
bloody stools, abdominal pain, tenesmus,
fevers), suggestive of Shigella
2. Recent travel with high fever (≥ 38.5)
and/or sepsis
3. Sick immunocompromised patients
* Empiric antibiotic choice: ciprofloxacin
or azithromycin
* May use loperamide; caution if bloody
stool, fever
C. difficile Infection (CDI) Diagnosis
Testing:
– Stool toxin test - combinations
* EIA for GDH, toxin
* NAAT PCR for toxin
– Pseudomembranes on colonoscopy
- Clinical Syndrome:
– Unexplained new-onset ≥3
unformed stools in 24 hours - C. difficile colonization: Positive C.
diff stool test in absence of clinical
syndrome - Criteria for severe C. difficile:
– WBC > 15 OR serum Cr 1.5 x pre-
morbid level
– Other risk factors: Age > 65,
immunosuppression, T > 38,
Albumin < 30
- Fulminant C. difficile:
– Sepsis, Shock, Ileus, perforation,
toxic megacolon (colon dilation
>6cm)
