Chapter 23. ID II: Bacterial Infections

How early should IV abx infusion be started prior to surgery if vancomycin or quinolones are used?

120 minutes

How long before surgery should cefazolin or cefuroxime be infused before surgery? Why one of these agents, especially cefazolin?

60 minutes

*usually cefazolin 1g

• preferred to PREVENT MSSA and Streptococcal infx

When would additional intra-operative abx doses be considered?

- Longer surgeries (>4 hrs)

- Major blood loss

What is the alternative perioperative abx of choice if patient has beta-lactam allergy?

Clindamycin or Vancomycin (vanco with MRSA, too)

Which abx is preferred for most surgeries to prevent MSSA and streptococcal infections?

Cefazolin

• Usually 1g IV

Which abx should be used for GI surgeries?

Cefazolin + one of the following:

- metronidazole

- cefotetan

- cefoxitin

- ampicillin/sulbactam

Covers: skin flora + gram negative + anaerobes

Which abx should be used for Cardiac/Vascular perioperative?

Cefazolin

Which abx should be used for Orthopedic (e.g. hip fracture repair, joint replacemnt)?

Cefazolin

How is meningitis diagnosed?

- lumbar puncture for a sample of CSF

- high CSF pressure detected during LP

• use a gram stain to also help guide abx choice

Symptoms of Meningitis?

Fever, Headache, nuchal rigidity (Stiff Neck), and altered mental status

What bacteria most commonly cause meningitis?

- Neisseria meningitidis

- Streptococcus pneumoniae

- Haemophilus influenzae

- Listeria monocytogenes in specific populations

Which populations commonly have meningitis d/t listeria monocytogenes?

- neonates

- >50 yrs

- immunocompromised

What should be given with an abx prior to or with the first dose for meningitis treatment and why?

dexamethasone IV to prevent neurological complications

• Give 15-20 minutes prior or with first abx dose (prevent neurological complications!)

• D/c if not S. pneumoniae

What treatment should be used for people ages 1 month to 50 years for meningitis?

ceftriaxone + vancomycin

What treatment should be used for neonates (<1 month old) for meningitis?

ampicillin (for listeria) +

ceftazidime or cefepime ±

gentamicin

Which drug do you avoid in neonates in meningitis and why?

Ceftriaxone

• Can cause biliary sludging (solids that precipitate from bile) and kernicterus (brain damage from high bilirubin) in neonates

What treatment should be used for >50 years or immunocompromised patients with meningitis?

ampicillin (for listeria coverage) + ceftriaxone + vancomycin

Signs/Sx of AOM?

Bulging tympanic (eardrum) membranes, otorrhea (middle ear effusion/fluid), otalgia (ear pain), tugging or rubbing of ears

What bacteria commonly cause acute otitis media?

- S. pneumoniae

- H. influenzae

- Moraxella catarrhalis

—> most AOM are caused by viruses though

If a patient is >6 months with non-severe AOM, what is a treatment option?

Observation for 48-72 hours

When can observation be considered for AOM?

for 2-3 days with non-severe symptoms, no otorrhea, and temp <102.2(39C):

- 6-23 months: sx in one ear only

- ≥ 2 years: sx in one or both ears

First-line treatment for AOM?

high-dose amox or amox/clav with lowest dose of clav to prevent diarrhea (90 mg/kg/day) IN 2 divided doses

Preferred brand for treating AOM?

Augmentin ES-600 (600mg/42.9mg per 5mL) in 2 divided doses

Alternative treatment for AOM in children with non-severe penicillin allergy?

second or third generation cephalosporin

PO AOM treatment duration?

Age < 2 y/o: 10 days

Age 2-5: 7 days

Age 6 and up: 5-7 days

Which medication is used for treatment failure (after 2-3 days) of the first-line drug for AOM?

Ceftriaxone 50 mg/kg IM daily x 3 days

What criteria is required to receive anti-infective treatment for pharyngitis (strep throat)?

rapid antigen test positive for s. pyogenes

Treatment for pharyngitis with s. pyogenes (strep throat)?

penicillin or amoxicillin

• Clinical presentation: sore throat, fever, swollen lymph nodes, white patches (Exudates) on tonsils

What bacteria commonly cause acute sinusitis?

- s. pneumoniae

- h. influenzae

- m. catarrhalis

What is the criteria for using anti-infectives in acute sinusitis?

≥ 10 days of persistent symptoms

or

≥ 3 days of severe symptoms (temp >102)

Acute sinusitis symptoms

Nasal congestion, purulent nasal discharge, facial/ear/dental pain, or headache

What is the treatment of choice for acute sinusitis?

amox/clav

What are key defining features of acute bronchitis?

- cough (productive or non-productive) lasting 1-3 weeks

- preceded by upper respiratory tract virus

- chest xray normal

- Abx typically not recommended! MANAGE WITH SUPPORTIVE CARE

Treatment for acute bronchitis?

abx not recommended; supportive care

What is another name for pertussis and what is it caused by?

Whooping cough

• Caused by Bordetella pertussis

• This is highly contagious!

What is the treatment of choice for pertussis?

Macrolides (azithromycin, clarithromycin)

Acute Bacterial Exacerbation of COPD Definition

GOLD guidelines define COPD exacerbation as increase in sx that worsen over 14 days

What are the cardinal symptoms of COPD exacerbation?

1. increased dyspnea

2. increased sputum volume

3. increased sputum purulence

What bacteria commonly trigger COPD exacerbations?

h. influenzae, m. catarrhalis, s. pneumoniae

When should abx be given to those experiencing a COPD exacerbation

Abx for 5-7 days IF any of the following are met:

- all 3 cardinal sx

- increased sputum purulence + 1 other sx

- mechanically ventilated

• Note: only 1 additional cardinal sx needed IF seeing increase sputum purulence

What is the preferred abx for COPD exacerbation?

- Amoxicillin/Clavulanate (Augmentin)

- Azithromycin

- Doxy

- Respiratory quinolone (levofloxacin, moxifloxacin)

What is the gold-standard for diagnosing CAP?

Chest X-RAY: will have infiltrates, opacities, or consolidations to indicate pna

Common pna sx inclued:

SOB, fever, cough WITH purulent sputum, RALES (crackling noises in the lungs), tachypnea (increased respiratory rate)

• Mild CAP: not hospitalized —> called “Walking Pneumonia”

What are typical bacterial infections that cause CAP?

S. pneumoniae

H. influenzae

Atypicals - Mycoplasma pneumoniae

What is the typical duration of tx for CAP?

5-7 days

Outpatient CAP treatment - Healthy (no comorbidities)

- Amoxicillin high dose (1g TID)

- Doxycycline

- Macrolide (azithromycin or clarithromycin if local pneumococcal resistance <25%)

Outpatient CAP treatment - High Risk (comorbidities)

- BL (Augmentin or cefpodoxime, cefuroxime) + macrolide or doxycycline

- Respiratory quinolone monotherapy (Levofloxacin or Moxifloxacin)

Inpatient CAP treatment - NONSEVERE (general medicine unit admission)

- BL (Unasyn or ceftriaxone) + macrolide or doxycycline

- respiratory quinolone monotherapy

Inpatient CAP treatment - severe (ICU)

BL + quinolone OR BL + macrolide -> DO NOT USE quinolone monotherapy

• These both must include BL

What drugs should be added on for inpatient CAP treatment if there is a risk for MRSA?

Vancomycin or Linezolid

What drugs should be added on for inpatient CAP treatment if there is a risk for Pseudomonas?

- Pip/tazo

- cefepime

- meropenem

When should a CAP regimen cover both MRSA and pseudomonas?

Hospitalization and use of parenteral abx in past 90 days

How long do HAP and VAP occur after admission?

> 48 hours after hospitalization or mechical vent

HAP/VAP empiric regimen

Nosocomial pathogens (hospital) common in HAP/VAP and inc risk of MRSA and MDR Gram (-) including Pseudomonas

• Need antibiotic for pseudomonas and MSSA (Cefepime or Zosyn)

• If MRSA add Vanco or linezolid

How many abx should be used for pseudomonas if there is a risk for MDR gram-negative pathogens in HAP/VAP?

two - (three drugs total)

Risk Factors: IV Abx use within 90 days, hospitalized 5 days or more prior to onset of VAP

Example regiemens: [usually MRSA risk is present]

1. Pip/Tazo + Ciproflox + Vanc

2. Cefepime + gentamicin + linezolid

HAP/VAP drug options for Pseudomonas and MSSA

All patients need an abx that covers pseudomonas + MSSA:

• Cefepime

• Pip/Tazo

• Levofloxacn

Abx for Pseudomonas in HAP/VAP

• Beta-lactams (do NOT use 2 beta-lactams together): piperacillin/tazobactam, cefepime, ceftazidime, imipenem/cilastatin, meropenem

• Levofloxacin or ciprofloxacin

• Aztreonam

• Aminoglycosides (typically tobramycin) - used in combo w/other antipseudomonal

What causes tuberculosis?

Mycobacterium tuberculosis

How does active TB transmission occur?

aerosolized droplets; highly contagious

How does latent TB present?

lacks symptoms

Active TB presentation

- cough/hemoptysis (Cough up blood)

- fever/night sweats

Isolation requirements for TB

- isolation in a single negative-pressure room

- healthcare workers wear respirator mask

How is latent TB diagnosed?

- tuberculin skin test (TST)/PPD

- interferon-gamma release assay (IGRA) blood test

How does the PPD test work for TB?

Solution injected intradermally and inspected for induration (raised area) 48-72 hrs later

What TB test is preferred in patients who have received the bacille Calmette-Guerin (BCG) vaccination?

IGRA blood test (false positive TST occur in these patients)

Criteria for a positive TB latent test (Skin)

≥ 5 mm induration

- HIV

- immunosuppression

—

≥ 10 mm induration

- residents/employees of "high risk congregate" settings (e.g. prison, healthcare facilities, shelters)

—

≥ 15 mm induration

- Patients w/ no risk factors

What is the preferred length of time for treatment of latent TB in adults and why?

3 to 4 months

Why? —> Shorter regimens for higher completion rates and less risk of hepatotoxicity

Latent Tuberculosis Regimens

• INH and rifapentine once weekly x 12 weeks via direct observation (DO NOT USE IN PREGNANCY b/c rifapentine fetal risk is unknown)

• INH + rifampin daily x 3 months

• Rifampin 600 mg daily x 4 months

• INH 300 mg daily for 6 or 9 months

What latent TB regimen might be preferred in HIV patients taking ART and why?

INH for 9 months

Why? d/t lower risk of drug interactions with ART

How can active TB be confirmed? [not latent]

Based on several findings:

• Chest XR: showing consolidation or cavitation (empty space) suggestive of TB

• Acid-fast bacilli smear of sputum sample: slow growing organism; sputum culture may take up to six weeks

Active TB treatment regimens

Divided into 2 phases:

1. Intensive Phase: [preferred due to avoiding resistance]

• RIPE x 2 months (rifampin, isoniazid, pyrazinamide, ethambutol)

2. Continuation Phase:

• Rifampin + isoniazid x 4 months

Daily TX or DOT 5x weekly recommended to increase medication adherence

Side Effects associated with Rifampin

- increased LFTS

- hemolytic anemia (detect w/ positive Coombs test)

- flu-like syndrome

- orange-red discoloration of body secretions that may stain (saliva, sweat, urine, tears); can stain contact lenses and clothing

- Many DDIs

Which drug may have fewer DDIs than rifampin and can potentially replace it in RIPE therapy?

Rifabutin

Boxed Warning for isoniazid

severe and fatal hepatitis

How to decrease the risk of peripheral neuropathy associated with isoniazid?

Pyridoxine (vitamin B6) 25-50 mg PO QD

Side effects associated with Isoniazid

- increased LFTs

- DILE

- hemolytic anemia (detect w/ positive Coombs test)

• Warnings: Peripheral Neuropathy (hence counter with Pyridoxine [Vitamin B6])

Contraindications to pyrazinamide for RIPE therapy?

Acute gout

Side effects of pyrazinamide for RIPE therapy?

- increased LFTs

- hyperuricemia, gout [b/c increases uric acid]

• Contraindicated in GOUT

Side effects associated with ethambutol from RIPE therapy?

- increased LFTs

Visual damage - requires baseline and monthly vision exams:

- optic neuritis (dose-related)

- confusion, hallucinations

Rifampin DDIs

Rifampin is potent INDUCER of CYP450 (1A2, 2C8, 2C9, 2C19, 3A4) and P-Glycoprotein

• Will significantly decrease concentration/effect of other drugs:

  • Protease inhibitors (sub rifabutin)

  • Warfarin (large dec. in INR)

  • Oral contraceptives (requires backup contraceptives)

• Do not use rifampin with Apixaban, Rivaroxaban (All DOACs)

What are the most common organisms that cause infective endocarditis?

Infective Endocarditis: infx of inner tissue of <3, typically heart valves

- staphylococci

- streptococci

- enterococci

What is used to diagnose Infective Endocarditis?

Modified Duke Criteria which includes:

• Use echocardiogram to visualize vegetation AND

• Positive blood cultures

What antibiotic is often added on or synergy in infective endocarditis?

gentamicin

infective endocarditis treatment duration

Required IV Treatment for 4-6 weeks

What are peak and trough goals when gentamicin is used for synergy in infective endocarditis?

Peak: 3-4 mcg/mL

Trough: < 1 mcg/mL

Infective Endocarditis Treatment for Viridans group streptococci

Penicillin or ceftriaxone (± gentamicin)

• If beta-lactam allergy, use vancomycin monotherapy

Infective Endocarditis Treatment for Staphylococci (MSSA)

Naficillin or cefazolin (+ gentamicin and rifampin if prosthetic valve)

(or daptomycin monotherapy if beta-allergy is present and no prosthetic valve)

Infective Endocarditis Treatment for Staphylococci (MRSA)

Vancomycin (or daptomycin if beta-lactam allergy monotherapy if BL allergy and no prosthetic valve) (+ gentamicin and rifampin if prosthetic valve)

Infective Endocarditis Treatment for enterococci

For both native and prosthetic valve IE: penicillin or ampicillin + gentamicin, or ampicillin + high-dose ceftriaxone

• If beta-lactam allergy, use vancomycin + gentamicin

• If VRE, use daptomycin or linezolid

What medication is given to high risk adults prior to dental work to prevent IE? (must also have cardiac conditions such as prosthetic heart valve, hx of endocarditis, heart transplant, certain congenital heart defects)

First line: Amoxicillin 2 grams PO 30 to 60 minutes prior dental procedure x 1

Alternatives to prophylactic IE medication for adults with penicillin allergy prior to dental procedures?

- azithromycin or clarithromycin 500 mg

- doxycycline 100 mg

- unable to take oral: cefazolin 1g im/iv, ampicillin 2g im/iv

When is an SBP infection suspected?

Ascitic fluid sample collected via paracentesis reveals > 250 cells/mm^3 PMNS (along w/ cirrhosis and ascites)

Empiric treatment for SBP

ceftriaxone x 5-7 days (target PEK and strep)

Secondary prophylaxis medications for SBP

- SMX/TMP

- Ciprofloxacin

Typical intra-abdominal infections have cultures of....

polymicrobial

- streptococci

- enteric gram negatives

- anaerobes (i.e. bacteroides fragilis)

What treatment for IAIs is typically added on if the original abx of choice does not have anaerobic activity?

Metronidazole x 4-5 days if source control established

what are examples of common IAI?

Appendicitis, cholecystitis (inflammation of gallbladder), cholangitis (infx of common bile duct), secondary peritonitis, and diverticulitis

What are systemic signs that one might see w/ a moderate to severe SSTI, but are absent in a mild SSTI?

- Temperature >100.4

- Heart rate >90 BPM

- WBC >12,000 or <4000 cells/mm^3

How does the superficial infection, impetigo, present?

honey-colored crusts over ruptured pustules

• caused by s. pyogenes, s. aureus (most often MSSA)

Impetigo treatment

- for limited, localized lesions: topical abx (i.e. mupirocin)

- numerous/extensive lesions: cephalexin 250-500 mg PO QID