Infectious Disease II - Bacterial Infections Flashcards
Bacterial Infections
When should you begin infusing antibiotics prior to surgery?
Most likely will be within 60 mins of the first incision (ex. cefazolin or cefuroxime)
If quinolone or vancomycin -> start infusion 120 mins before first incision
- longer infusion time
When may you need to redose antibiotics during surgery?
- Longer surgeries (lasting >4 hours)
- Major blood loss
What pathogens are we worried about for cardiac/orthopedic/vascular surgeries? What are the preferred antibiotics and what are alternatives, if needed?
Pathogens - skin flora (staph and strep)
Preferred abx - cefazolin OR cefuroxime
Alternatives - vancomycin OR clindamycin
What pathogens are we worried about for GI surgeries? What are the preferred antibiotics and what are alternatives, if needed?
Pathogens - skin flora (staph/strep) + GI flora (GNRs + gram neg anaerobes)
Preferred abx - amp/sulbactam OR cefoxitin OR cefotetan OR [cephalosproin + metronidazole]
Alternatives - [metronidazole OR clindamycin] + [fluoroquinolone OR aminoglycoside]
What are the hallmark symptoms of meningitis? How is the diagnosis of meningitis made?
Severe headache
Confusion
Fever
Stiff neck/nuchal rigidity
Others: Chills, vomiting, seizures, rash (2º to N. meningiditis)
Diagnosis: lumbar puncture to sample CSF, then gram stain/culture; high CSF pressure during lumbar puncture is also sign of possible infection
IV dexamethasone - start at same time as abx; d/c if bug is not strep pneumo (has not shown benefit with other pathogens)
IV abx - start ASAP, need higher doses
What pathogens and empiric treatment do we have for bacterial meningitis in neonates (<1 mo old)?
Pathogens:
- E. coli
- Group B strep (strep agalactiae)
- Listeria
Treatment:
- Ampicillin + cefotaxime or gentamicin
NO CEFTRIAXONE IN NEONATES DUE TO BILIARY SLUDGING & KERNICTERUS
What pathogens and empiric treatment do we have for bacterial meningitis in pts 1-23 months old?
Pathogens:
- S. pneumo
- N. meningitidis
- H. influenzae
- E. coli
- Group B strep
Treatment:
- ceftriaxone or cefotaxime + vancomycin (for additional strep coverage, NOT MRSA)
What pathogens and empiric treatment do we have for bacterial meningitis in pts 2-50 years old?
Pathogens:
- S. pneumo
- N. meningitidis
Treatment:
- ceftriaxone or cefotaxime + vancomycin (for additional strep coverage, NOT MRSA)
What pathogens and empiric treatment do we have for bacterial meningitis in pts > 50 yo or immunocompromised?
Pathogens:
- S. pneumo
- N. meningitidis
- Listeria
Treatment:
- Ampicillin + cefotaxime or gentamicin + vancomycin
What are the most common bacterial causes of acute otitis media? What are the preferred antibiotics?
Pathogens:
- S. pneumoniae
- H. influenzae
- M. catarrhalis
Treatment:
- amoxicillin or amox/clav at high-dose 90mg/kg/day; amox/clav preferred if pt received amoxicillin in past 30 days
- if non-severe penicillin allergy: cefpodoxime, cefuroxime, cefidinir, ceftriaxone IM
If treatment failure: no imporvement/worsening after 2-3 days of therapy
- amox/clav if amox was used originally
- ceftriaxone IM daily for 1-3 days
When do we consider observation vs. treatment for acute otitis media prior to antibiotics?
Treatment required:
- if < 6 mo old
- if severe symptoms in all ages (ill appearance, otorrhea, otalgia > 48 hrs, temp > 39 ºC/102.2 ºF)
- if bilateral infection in kids 6-23 months
Consider observation for 2-3 days:
- 6-23 months old and only unilateral
- ≥ 2 yo with unilateral OR bilateral, as long as no severe symptoms
What are the causes, presentation, and criteria or anti-infective treatment for the common cold?
Causes: respiratory viruses
Signs/sx: sneezing, runny nose, mild sore throat, cough
Criteria for treatment: antivirals/antibiotics not indicated
- symptomatic care OTCs
What are the causes, presentation, and criteria or anti-infective treatment for influenza?
Causes: influenza virus
Signs/sx: suddent onset fever, chills, fatigue, myalgia
Criteria for treatment:
- suspected for confirmed infection
- Outpatient: symptoms <48hrs
- severe illness
- symptoms + risk factors for influenza complications
Options:
- Oseltamivir (tamiflu)
- Baloxavir marboxil (xofluza)
- symptomatic treatment
What are the causes, presentation, and criteria or anti-infective treatment for pharyngitis?
Causes: respiratory viruses, group A strep (strep pyogenes)
Signs/sx: severe sore throat, fever, swollen lymph nodes, white patches (exudates) on tonsils)
- no cough, runny nose, or congestion
Criteria for treatment: rapid antigen test or throat culture identifying strep pyogenes
Treatment:
- (oral) Penicillin VK
- Amoxicillin
- alternatives -> macrolide or clindamycin
What are the causes, presentation, and criteria or anti-infective treatment for acute sinusitis?
Causes: respiratory viruses, S. pneumoniae, H. influenzae, M. catarrhalis
Signs/sx: nasal congestion, purulent nasal discharge, facial/ear/dental pain, headache
Criteria for treatment:
- at least 10 days of persistent symptoms
- at least 3 days of severe symptoms, like face pain, purulent nasal discharge, temp > 102 ºF
- worsening after initial improvement
Treatment:
- amox/clav
- symptomatic care for up to 7 days
How do we manage acute bronchitis?
bronchitis is most likely caused by viruses, but some rare bacterial causes
symptoms:
- cough for 1-3 weeks
- +/- sputum production
- no systemic symptoms, normal CXR
- wheezing or rhonchi audible on auscultation
treatment:
- ONLY SYMPTOMATIC
- NO ABX
How is pertussis treated?
pertussis (causes by Bordetella pertussis) AKA whooping cough is highly contagious and associated with high morbidity and mortality in children
Treat with macrolides (azithromycin and clarithromycin)
What are the most common causes of a COPD exacerbation? How do we treat?
Respiratory viruses
Bacteria - H. influenzae, M. catarrhalis, S. pneumoniae
Environmental pollution
Unknown causes
Management:
- supportive treatment with oxygen, short-acting inhaled bronchodilators, and IV or PO steroids
- antibiotics if increased sputum purulence + at least 1 additional symptom (inc dyspnea or sputum volume) or if mechanically ventilated: amox/clav, azithromycin, doxycyline, respiratory fluoroquinolone for 5-7 days
What is the gold standard of diagnosis for pneumonia? What other symptoms are seen?
Diagnosis - infiltrates/opacities/consolidations on CXR
Symptoms - systemic (fever, increased WBC), cough, shortness of breath, purulent sputum, tachypnea
What pathogens are we worried about for CAP? How long is the duration of treatment likely to be for CAP?
Strep pneumoniae
Haemophilus influenzae
Atypicals (mycoplasma pneumoniae, chlamydia pneumoniae)
Duration of treatment: 5-7 days
Treatment for CAP if outpatient, healthy w/ no comorbidities?
Treatment for CAP if outpatient, but high-risk w/ comorbidities?
Healthy:
- high dose amoxicillin
- doxycycline
- macrolide
Comorbidities:
- beta-lactam (amox/clav or cefuroxime or cefpodoxime) + macrolide or doxycyline
- monotherapy with respiratory fluoroquinolone
What are some things/adverse effects we need to worry about in the common CAP treatment options?
Macrolides -
- QT prolongation
- Drug interactions (clarithromycin)
Doxycycline -
- Pregnancy
- Breastfeeding
Fluoroquinolones -
- Seizures
- QT prolongation
- Tendonitis/rupture (esp elderly)
- Cardiovascular risk
- Peripheral neuropathy
- Pregnancy
Treatment for CAP if inpatient and non-severe (non-ICU)?
Treatment for CAP if inpatient and severe?
Non-severe:
- beta-lactam (CRO, cefotaxime, unasyn, ceftaroline) + macrolide OR doxycyline
- monotherapy with respiratory fluoroquinolone
Severe:
- beta-lactam + macrolide
- beta-lactam + respiratory fluoroquinolone
What are risk factors for MRSA and pseudomonas in CAP patients? How does that change the treatment?
Prior respiratory isolation of MRSA or Positive MRSA nasal swab -> add MRSA activity (vancomycin or linezolid)
Prior respiratory isolation of Pseudomonas -> use b-lactam with pseudomonas activity (cefepime, mero, zosyn, ceftazidime, imipenem/cilastatin)
Recent hospitalization in last 90 days AND IV antibiotic exposure -> use a regimen with abx active against MRSA and Pseudomonas
How long must a patient be hospitalized or ventilated to qualify for nosocomial pneumonia? What are the common pathogens that cause HAP and VAP? How long is the treatment duration?
HAP - 48 hours in hospital
VAP - 48 hours ventilated
Pathogens:
- MRSA, MSSA, Pseudomonas aeruginosa, other gram negatives (ex. E. coli, acinetobacter, enterobacter)
Duration of treatment: 7 days
How do we treat HAP/VAP?
Need at least 1 antibiotic that is active against both psuedomonas AND MSSA (cefepime, piperacillin/tazobactam, meropenem, or levofloxacin)
- If risk factors for MRSA -> add vancomycin or linezolid
- If risk factors for MDR gram-negs and MRSA -> add a 2nd antipseudomonal antibiotic (ex. fluoroquinolone or aminoglycoside) AND vanc or linezolid
Pseudomonas agents:
b-lactams
- piperacillin/tazobactam
- cefepime, ceftazidime
- meropenem, imipenem/cilastatin
- aztreonam
- ceftolaozane/tazobactam, ceftazidime/acibactam (reserve for MDR)
fluoroquinolones
- cipro
- levo
aminoglycosides
- gentamicin
- tobramycin
- amikacin)
What are the risk factors for MRSA or MDR gram-negative pathogens for HAP/VAP?
MRSA only:
- IV abx in past 90 days
- MRSA prevalence > 20% or unknown
- Prior MRSA infection or positive MRSA nasal swab
MDRs:
- IV abx in past 90 days
- Gram-neg resistance >10%
- Hospitalization ≥ 5 days prior to VAP onset
What are the testing options for latent TB? When is the diagnosis made?
Perferred: interferon gamma release assay (IGRA)
Tuberculin skin test (TST)
- ≥ 5mm: positive if close contacts of active TB, HIV, or immunosuppressed
- ≥ 10mm: positive if high-risk setting employees or residents, IV drug use
- ≥15mm: positive if no risk factors
Diagnosis: positive TST or IGRA
- rule out active disease through negative chest ray and no symptoms
What are the treatment options for latent TB? (4)
isoniazid (INH) + rifapentine weekly for 12 weeks
- directly observed therapy
- NOT for pregnant patients
isoniazid (INH) + rifampin daily for 2 months
rifampin daily for 4 months
isoniazid daily for 6 or 9 months
- may be preferred in HIV positive patients taking ART due to less drug interactions compared to the others. Do regimen for 9 months in this case
*shorter regimens (3-4 months) preferred due to less hepatotoxicity and better adherence
How do you diagnose active TB?
Symptoms (cough >2-3 weeks, hemoptysis, fever, night sweats, unintentional weight loss)
Diagnostic tests
- positive TST or IGRA
- CXR
- Sputum culture with acid fast bacilli (AFB)
- M. tuberculosis identified on sputum culture
What is the treatment for active TB?
Initial phase with RIPE for 2 months
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol
Continuation phase with RI for ≥4 months (if no evidence of resistance and repeat sputum cultures are neg)
- Rifampin
- Isoniazid
Rifampin - contraindications, side effects, important notes about drug interactions
Contraindications:
- with protease inhibitors
Side effects:
- increased LFTs, hemolytic anemia (detected with positive Coombs test), flu-like syndrome
- orange-red discoloration of body secretions
significant drug interactions
- potent CYP450 INDUCER and pgp
- rifabutin has fewer drug interactions and can replace rifampin in some cases
- notable interactions: protease inhibitors, warfarin and DOACs, oral contraceptives
Isoniazid (INH) - boxed warning, contraindications, warnings, side effects, important notes
Boxed warning:
- severe (and fatal) hepatitis
Contraindications:
- active liver disease
- previous severe adverse reaction to INH
Warnings:
- peripheral neuropathy
pyridoxine (vitamin B6) supplementation is recommended
Side effects:
- increased LFTs
- drug-induced lupus erythematosus (DILE)
- hemolytic anemia (identified with positive Coombs test)
Notes:
- Pyridoxine (vitamin B6) 25-50mg PO daily should be used to reduce the risk of peripheral neuropathy!!
Pyrazinamide - contraindications and side effects
Contraindications:
- acute gout, severe hepatic damage
Side effects
- increased LFTs, hyperuricemia/gout
Ethambutol - contraindications and side effects
Contraindications:
- optic neuritis
Side effects
- increased LFTs, optic neuritis (dose-related), confusion, hallucinations
Requires visual exam at baseline and monthly
What are the three most common causes of infective endocarditis? How is it diagnosed?
Staphylococci
Streptococci
Enterococci
Diagnosis: using Modified Duke Criteria
- echocardiogram
- positive blood cultures
- symptoms
How do we treat infective endocarditis based on the organism?
treatment duration likely 4-6 weeks
viridans strep
- penicillin or CRO (+/- gentamicin)
- allergy -> vanc
staph
- MSSA -> nafcillin or cefazolin
- MRSA -> vanc or dapto
- prosthetic valve -> add gentamicin AND rifampin to the above regimen
- b-lactam allergy -> vancomycin
enterococci
- native or prosthetic valve -> penicillin or ampicillin + gentamicin or high dose CRO
- vanc resistant -> linezolid or dapto
- b-lactam allergy -> vanc + gentamicin
When do we give endocarditis antibiotic prophylaxis prior to dental procedures?
If the patient is at high risk (cardiac conditions) + dental work needed (ex. root canal)
- artificial valve, hx of endocarditis, heart tx with abnormal heart valve function, some congenital heart defects
Agents: take as single dose 30-60mins prior to procedure
- 1st line - amoxicillin 2g PO
- Unable to take PO -> ampicillin 2g IV/IM or cefazolin 1g IV/IM
- Penicillin allergy -> azithromycin or clarithromycin 500mg PO or doxycycline 100mg PO
Common pathogens of SBP?
How is spontaneous bacterial peritonitis (SBP) diagnosed/when do we suspect it?
What is the empiric treatment?
Common pathogens: Streptococci, Proteus, E. coli, Klebsiella
Diagnosis: sx of infection (fever, inc. WBCs, AMS), ascites, abdominal pain/tenderness, ascitic fluid has > 250 cells/mm^3 PMNs (polymorphonuclear leukocytes)
Empiric tx: duration of 5-7 days
- 1st line: ceftriaxone or cefotaxime
- if critically ill or risk of MDRs -> zosyn or meropenem
When should we do secondary ppx for SBP and what agent do we use?
Criteria: prior episode of SBP or ascitic fluid protein <1.5 g/dL + impaired renal or hepatic function
Therapy options: SMX/TMP or fluoroquinolone (cipro)
Duration: indefinite or until liver transplant
What are the different classifications of severity of SSTIs?
Mild - local symptoms only
Moderate - local and systemic signs (temp > 100.4ºF, HR >90, WBC > 12k or < 4k
Severe - systemic signs + skin sloughing, fluid-filled blisters, hypotension, organ dysfunction, immunocompromised patients, or failed oral abx and/or I&D
Impetigo - common bugs, presentation, treatment
Pathogens - S. pyogenes, S. aureus (likely MSSA)
Presentation
- honey-colored crusts
Treatment
- topical if limited/localized lesions: mupirocin
- numerous, extensive lesions: cephalexin 250-500mg PO QID (or dicloxacillin)
Folliculitis/furuncle/carbuncle - common bugs, presentation, treatment
Pathogens - S. aureus, including CA-MRSA
Presentation - inflamed hairs
Treatment
- incision and drainage for large furuncles and carbuncles +/- antibiotics
- SMX/TMP or doxycyline
Cellulitis (non-purulent) - common bugs, presentation, treatment
Pathogens - strep (s. pyogenes), staph aureus
Presentation
- unilateral
Treatment: duration ~5 days
- cephalexin 500mg PO QID
- or dicloxacillin
- allergy -> clindamycin
Treatment if severe: duration 7-14 days
target MRSA
- vancomycin, dapto, or linezolid
- can transition to PO once stable
Cellulitis (purulent) - common bugs, presentation, treatment
Pathogens - MSSA, CA-MRSA
Presentation
- draining fluid
- tend to be more localized
Treatment if mild-mod: duration ~5 days
- incision and drainage
- PLUS SMX/TMP or doxycycline
Treatment if severe: duration 7-14 days
target MRSA
- vancomycin, dapto, or linezolid
- can transition to PO once stable
Necrotizing fasciitis - common bugs, presentation, treatment
Pathogens - monomicrobial or polymicrobial
- strep, staph, anaerobes, gram negatives
Presentation
- commonly affects extremities or perineal area
- Often preceded by minor trauma
Treatment
- surgical debridement
- clindamycin (anti-toxin)
PLUS vancomycin or dapto
PLUS beta-lactam (zosyn or meropenem)
Diabetic foot infections - common bugs, presentation, treatment/duration
Pathogens - polymicrobial
- gram-pos: staph, strep, enterococci
- gram-neg: E. coli, kleb, proteus
- anaerobes: bacteroides spp.
- may be at risk of rMRSA or pseudomonas
Mild - treat like cellulitis
Moderate to Severe
- no concern for MRSA/pseudomonas: unasyn, ertapenem, moxifloxacin, or metronidazole + ceftriaxone
- concern for pseudomonas: zosyn, meropenem, or metronidazole + cefepime, cipro, or levofloxacin
- add MRSA coverage if needed as well
duration:
- 2-4 weeks if no bone involvement
- 4-6 weeks for osteomyelitis
- 2-5 days if amputation with no residual infection
What is the significance of WBCs, bacteria, and leukocyte esterase for UTI diagnosis?
WBCs - pyruia (WBCs > 10 cells/mm^3) indicates UTI
RBCs - not specific to infection, but often present in UTIs
Bacteria - contamination, colonization, or infection
Leukocyte esterase - marker of WBCs and pyuria
Nitrites - marker of nitrate reductase producing bacteria
pH - marker of urease-producing bacteria
What pathogens most commonly cause acute cystitis? What is the treatment?
Pathogens
- E. coli (most common)
- Proteus, Klebsiella, staphylococcus saprophyticus
Presentation
- no systemic
- pain, frequency urinating
Treatment
- nitrofurantoin 100mg PO BID x5 days (contraindicated if CrCL <60 mL/min)
- fosfomycin 3g x1 dose
- sulfamethoxazole/trimethoprim DS 1 tab PO BID x3 days (contraindicated in sulfa allergy)
What pathogens most commonly cause acute pyelonephritis? What is the treatment?
Pathogens
- E. coli (most common)
- Proteus, Klebsiella, Enterobacter, Serratia, Pseudomonas, Enterococci
Presentation
- Systemic symptoms
- Flank pain
Outpatient treatment: PO
- ciprofloxacin or levofloxacin
- bactrim
Inpatient treatment: IV
- ceftriaxone
- cipro or levo
- zosyn or carbapenem if concerns for resistance (urinary instrumentation, prior isolation or culture, received broad spectrum abx in past)
What urinary analgesic can be used to help with pain/burning with urination? What are some administration counseling points and notes?
Phenazopyridine (Rx: Pyridium, OTC: Azo Urinary Pain Relief)
**only helps with symptoms, NOT the infection
Adminstration
- Max duration: 2 days
- Take with 8oz of water with or immediately following food to minimize upset stomach
Notes
- Can cause red-orange coloring of the urine and other body fluids
How do we treat asymptomatic bacteriuria in pregnancy?
beta-lactams are preferred
- cephalexin
- amox/clav
alternatives if allergy
- fosfomycin
- nitrofurantoin (not preferred, potential fetal risk)
- bactrim (not preferred, potential fetal risk)
AVOID fluoroquinolones!! - fetal risk
What are the signs and symptoms of C. diff? What is the classification criteria for nonsevere, severe, and fulminant?
Signs/sx:
- at least 3 loose, watery stools in 24 hours
- fever, abdominal pain, elevated WBC or impaired renal function
- positive stool test (nucleic acid amplification test [NAAT], enzyme immunoassays)
Nonsevere: WBC < 15k and SCr < 1.5
Severe: WBC ≥ 15k or SCr > 1.5
Fulminant: hypotension, shock, ileus, or toxic megacolon
What are the treatment options for C. diff? When do we consider bezlotuxumab
Initial episode:
- stop causative agents
- fidaxomicin 200mg PO BID OR vancomycin 125mg PO QID
- IF ABOVE UNAVAILABLE -> metronidazole 500mg PO TID
- duration: 10 days
Recurrence:
- fidaxomicin 200mg PO BID x10 days
- vancomycin PO + prolonged taper
- 2+ recurrences: vanc PO + rifaximin x20 days
- fecal microbiota transplantation
Fulminant:
- vancomycin 500mg PO/NG Q6H PLUS IV metronidazole
- surgical evaluation for colectomy
*adjunct bezlotoxumab (neutralizes toxin B) can be considered for high-risk patients (age ≥ 65, immuocompromised, severe, 2+ episodes in last 6 months), but CAUTION for heart failure
What are the signs and symptoms of these common STIs: chlamydia, gonorrhea, genital warts, latent syphilis, primary syphilis, bacterial vaginosis, and trichomoniasis
chlamydia - genital discharge or no symptoms
gonorrhea - genital discharge or no symptoms
genital warts - single or multiple pink/skin-tones lesions
latent syphilis - asymptomatic
primary syphilis - painless, smooth genital sores (chancre)
bacterial vaginosis - vaginal discharge that has a fishy odor and pH > 4.5, little or no pain
trichomoniasis - yellow/green, frothy vaginal discharge with pH > 4.5, foul odor pain with intercourse
What diagnostic tests are used to identify syphilis? How do we treat syphilis (primary, secondary, or early latent)?
diagnositic tests - nontreponemal test (VDRL, RPR) + treponemal assay
Primary: chancre
Secondary: rash, lymphadenopathy
Early latent, acquired ≤ 1 year ago: asymptomatic
Treatment the same for all!!!
- penicillin G benzathine (Bicillin L-A) 2.4 million units IM x1 dose
(this is for pregnant patients too)
- alternative -> doxycycline 100mg PO BID x14 days
- alternative if pregnant -> desensitization protocol followed by penicillin G
How do we treat syphilis (late latent or tertiary)?
Late latent, acquired > 1 year ago: asymptomatic
Tertiary: cardiovascular, CNS manifestations
Treatment is the same for both!!
- penicillin G benzathine (Bicillin L-A) 2.4 million units IM weekly x 3 doses
(this is for pregnant patients too)
- alternative -> doxycycline 100mg PO BID x28 days
- alternative if pregnant -> desensitization protocol followed by penicillin G
How do we treat neurosyphilis?
neurosyphilis: altered mentation, motor/sensory dysfunction, symptoms of meningitis, abnormal CSF
Treatment:
- penicillin G aqueous 3-4 million units IV Q4H x10-14 days
- allergy -> desensitization protocol followed by penicillin G
How do we treat gonorrhea?
Treatment
1st line - ceftriaxone 500mg IM x1 (if <150kg)
- ≥ 150 kg, 1g IM x1
Treatment the same for pregnant patients
If chlamydia not excluded, add doxycycline
How do we treat chlamydia?
Treatment
Doxycycline 100mg PO BID x7 days
- pregnancy -> azithromycin 1g PO x1
How do we treat bacterial vaginosis?
Treatment
- metronidazole 500mg PO x7 days
- metronidazole 0.75% gel x5 days
- clindamycin 2% cream x7 days
How do we treat trichomoniasis? (females vs. males)
Females: metronidazole 500mg PO x7 days
Males: metronidazole 2g PO x1
What causes genital warts? How do we treat genital warts?
Human papillomavirus (HPV) strains 6 and 11
Treatment
- imiquimod cream (immune activator)
- podofilox solution or gel (causes wart necrosis)
What is the most common and fatal tickborne illness? What are the symptoms? What is the drug of choice?
Rocky Mountain spotted fever
Symptoms
- erythematous petechial rash that follows 3-5 days after fever/headache/pain
Treatment
- Doxycycline (even for pediatrics)
What is the difference between lyme disease and ringworm? What is the treatment of choice for each?
Lyme: bacterial
- Erythema migrans: bull’s eye rash
- diagnosis: enzyme immunoassay (EIA)
- treatment: doxycycline
Ringworm: fungal
- reddish, raised rings, can be itchy
- treatment: clotrimazole or another topical antifungal
