Bacterial Infections
Sepsis and Septic Shock
Definition (Sepsis-3 Criteria, 2016)
Sepsis: Life-threatening organ dysfunction caused by dysregulated host response to infection (SOFA score ≥2 points)
Septic Shock: Sepsis with persisting hypotension requiring vasopressors (MAP ≥65 mmHg) and lactate >2 mmol/L despite adequate fluid resuscitation
qSOFA (Quick SOFA) for Screening
- Respiratory rate ≥22/min
- Altered mentation (GCS <15)
- Systolic BP ≤100 mmHg
≥2 criteria = High risk for poor outcomes
Management (Surviving Sepsis Campaign 2021)
Hour-1 Bundle:
- Measure lactate level (remeasure if >2 mmol/L)
- Obtain blood cultures before antibiotics
- Administer broad-spectrum antibiotics
- Begin rapid fluid resuscitation (30 mL/kg crystalloid for hypotension or lactate ≥4 mmol/L)
- Apply vasopressors if hypotensive during or after fluid resuscitation to maintain MAP ≥65 mmHg
Empiric Antibiotic Therapy
| Source |
First-Line Therapy |
Alternative |
| Unknown/Community-acquired |
Piperacillin-tazobactam 4.5g IV q6h + Vancomycin |
Cefepime + Vancomycin |
| Nosocomial/Healthcare-associated |
Meropenem 1g IV q8h + Vancomycin |
Cefepime + Linezolid |
| Intra-abdominal |
Piperacillin-tazobactam + Metronidazole |
Meropenem |
| Urinary |
Ceftriaxone 2g IV q24h |
Fluoroquinolone (if susceptible) |
Reference: Surviving Sepsis Campaign 2021 Guidelines (Critical Care Medicine)
Community-Acquired Pneumonia (CAP)
Severity Assessment (CURB-65)
- Confusion
- Urea >7 mmol/L (BUN >19 mg/dL)
- Respiratory rate ≥30/min
- Blood pressure: SBP <90 or DBP ≤60 mmHg
- Age ≥65 years
Score 0-1: Outpatient treatment
Score 2: Consider hospitalization
Score ≥3: Hospital admission, consider ICU
Empiric Antibiotic Therapy (ATS/IDSA 2019)
| Setting |
Recommended Treatment |
Duration |
| Outpatient (previously healthy) |
Amoxicillin 1g TID OR Doxycycline 100mg BID OR Macrolide (if local resistance <25%) |
5-7 days |
| Outpatient (comorbidities) |
Amoxicillin-clavulanate 875/125mg BID + Macrolide OR Respiratory fluoroquinolone |
5-7 days |
| Hospitalized (non-ICU) |
Beta-lactam (Ceftriaxone 1-2g IV q24h) + Macrolide OR Respiratory fluoroquinolone |
5-7 days |
| ICU |
Beta-lactam + Macrolide OR Beta-lactam + Respiratory fluoroquinolone |
7 days minimum |
Reference: ATS/IDSA 2019 Community-Acquired Pneumonia Guidelines
Treatment (IDSA 2011, Updated 2023)
| Type |
First-Line Therapy |
Duration |
| Uncomplicated Cystitis |
Nitrofurantoin 100mg BID OR Trimethoprim-sulfamethoxazole DS BID OR Fosfomycin 3g single dose |
5-7 days (3 days TMP-SMX) |
| Acute Pyelonephritis (outpatient) |
Ciprofloxacin 500mg BID OR Levofloxacin 750mg daily (if susceptible) |
7 days |
| Acute Pyelonephritis (inpatient) |
Ceftriaxone 1-2g IV q24h OR Fluoroquinolone OR Aminoglycoside |
10-14 days total |
Reference: IDSA 2011 Uncomplicated UTI Guidelines
Treatment (IDSA/SHEA 2021)
| Episode/Severity |
Preferred Treatment |
Duration |
| Initial episode (non-severe to severe) |
Fidaxomicin 200mg PO BID OR Vancomycin 125mg PO QID |
10 days |
| Initial episode (fulminant) |
Vancomycin 500mg PO/NG QID + Metronidazole 500mg IV q8h |
10 days minimum |
| First recurrence |
Fidaxomicin 200mg PO BID (if not used for initial) OR Vancomycin taper/pulse |
Variable |
Reference: IDSA/SHEA 2021 Clostridioides difficile Infection Guidelines
Viral Infections
Influenza
Antiviral Treatment (CDC 2023-2024)
| Medication |
Dosing |
Notes |
| Oseltamivir (Tamiflu) |
75mg PO BID × 5 days |
First-line; effective against influenza A and B |
| Zanamivir (Relenza) |
10mg (2 inhalations) BID × 5 days |
Avoid in asthma/COPD |
| Peramivir (Rapivab) |
600mg IV × 1 dose |
For patients unable to take oral/inhaled |
| Baloxavir (Xofluza) |
40-80mg PO × 1 dose (weight-based) |
Single-dose option |
Treatment Indications
Treat ALL patients with:
- Hospitalized patients with influenza
- Severe, complicated, or progressive illness
- High-risk patients: age <2 or ≥65 years, pregnant/postpartum, immunocompromised, chronic medical conditions
Reference: CDC Influenza Antiviral Guidelines 2023-2024 Season
Antiviral Treatment (NIH Guidelines 2024)
| Medication |
Dosing |
Indications |
| Nirmatrelvir-ritonavir (Paxlovid) |
300mg/100mg PO BID × 5 days |
Mild-moderate COVID-19 with high risk for progression; start within 5 days |
| Remdesivir (Veklury) |
200mg IV day 1, then 100mg IV daily × 2-4 days |
Mild-moderate (high-risk outpatients) or severe COVID-19 |
| Molnupiravir (Lagevrio) |
800mg PO BID × 5 days |
Alternative when Paxlovid/Remdesivir unavailable |
Reference: NIH COVID-19 Treatment Guidelines 2024
Treatment by Clinical Presentation
| Condition |
Treatment |
Duration |
| Genital herpes (first episode) |
Acyclovir 400mg PO TID OR Valacyclovir 1g PO BID |
7-10 days |
| Genital herpes (recurrent) |
Acyclovir 800mg PO TID × 2 days OR Valacyclovir 500mg PO BID × 3 days |
As listed |
| HSV encephalitis |
Acyclovir 10 mg/kg IV q8h |
14-21 days |
Reference: CDC STI Treatment Guidelines 2021
Antiretroviral Therapy (ART) - Initial Regimens (DHHS 2024)
| Regimen |
Components |
Dosing |
| Biktarvy |
Bictegravir/Tenofovir alafenamide/Emtricitabine |
50/25/200mg PO daily |
| Dovato |
Dolutegravir/Lamivudine |
50/300mg PO daily |
Opportunistic Infection Prophylaxis
| Infection |
Indication |
Prophylaxis |
| Pneumocystis jirovecii pneumonia (PCP) |
CD4 <200 cells/mm³ |
TMP-SMX DS daily OR Dapsone 100mg daily |
| Toxoplasmosis |
CD4 <100 cells/mm³ and Toxoplasma IgG positive |
TMP-SMX DS daily (also covers PCP) |
Reference: DHHS Guidelines for Use of Antiretroviral Agents 2024
Fungal Infections
Candidiasis
Treatment by Site (IDSA 2016)
| Type |
Treatment |
Duration |
| Oropharyngeal (thrush) |
Fluconazole 100-200mg PO daily OR Nystatin suspension QID |
7-14 days |
| Esophageal |
Fluconazole 200-400mg PO/IV daily |
14-21 days |
| Candidemia (non-neutropenic) |
Echinocandin (Caspofungin 70mg IV × 1, then 50mg IV daily OR Micafungin 100mg IV daily) |
14 days after negative blood cultures |
Reference: IDSA 2016 Candidiasis Guidelines
Cryptococcal Meningitis Treatment
| Phase |
Treatment |
Duration |
| Induction |
Liposomal AmB 3-4 mg/kg IV daily + Flucytosine 100 mg/kg/day PO divided q6h |
≥2 weeks (HIV) or 4 weeks (non-HIV) |
| Consolidation |
Fluconazole 400mg PO/IV daily |
8 weeks |
| Maintenance |
Fluconazole 200mg PO daily |
≥12 months |
Reference: IDSA 2010 Cryptococcosis Guidelines
Parasitic Infections
Malaria
Treatment of Uncomplicated Malaria (CDC 2024)
| Species/Resistance |
Treatment |
Notes |
| Chloroquine-resistant P. falciparum |
Artemether-lumefantrine (Coartem) 4 tablets PO BID × 3 days OR Atovaquone-proguanil (Malarone) 4 tabs PO daily × 3 days |
Take with fatty food |
| Severe Malaria |
IV Artesunate (preferred): 2.4 mg/kg IV at 0h, 12h, 24h, then daily |
ICU monitoring required |
Reference: CDC Malaria Treatment Guidelines 2024
Common Intestinal Parasites Treatment
| Parasite |
Treatment |
Alternative |
| Giardia lamblia |
Metronidazole 250mg PO TID × 5-7 days OR Tinidazole 2g PO × 1 |
Nitazoxanide 500mg PO BID × 3 days |
| Ascaris lumbricoides (roundworm) |
Albendazole 400mg PO × 1 OR Mebendazole 100mg PO BID × 3 days |
Ivermectin 150-200 mcg/kg × 1 |
| Enterobius vermicularis (pinworm) |
Albendazole 400mg PO × 1, repeat in 2 weeks |
Pyrantel pamoate 11 mg/kg × 1 |
Reference: CDC Yellow Book 2024, WHO Guidelines
Antimicrobial Stewardship
Core Principles of Antimicrobial Stewardship
Key Strategies (IDSA/SHEA 2016)
- Right drug: Select appropriate agent based on likely pathogen
- Right dose: Optimize dosing based on PK/PD principles
- Right duration: Use shortest effective duration
- Right route: Transition IV to PO when appropriate
- De-escalation: Narrow spectrum once pathogen identified
- Discontinuation: Stop when infection resolved
Optimal Antibiotic Duration for Common Infections
| Infection |
Recommended Duration |
Notes |
| Community-acquired pneumonia |
5-7 days |
If clinical improvement and afebrile >24h |
| Hospital/Ventilator-acquired pneumonia |
7 days |
Adequate source control achieved |
| Uncomplicated UTI |
3-5 days |
Depends on agent used |
| Pyelonephritis |
7-14 days |
Based on severity and response |
| Cellulitis |
5-6 days |
Continue until clinical improvement |
MRSA (Methicillin-Resistant Staphylococcus aureus)
| Infection Type |
Treatment Options |
| Bacteremia/Endocarditis |
Vancomycin (preferred) OR Daptomycin 6-10 mg/kg IV daily |
| Pneumonia |
Vancomycin 15-20 mg/kg q8-12h OR Linezolid 600mg q12h |
CRE (Carbapenem-Resistant Enterobacterales)
| Agent |
Dosing |
Coverage/Notes |
| Ceftazidime-avibactam |
2.5g IV q8h |
KPC producers; some OXA-48; NOT MBL |
| Meropenem-vaborbactam |
4g IV q8h |
KPC producers; NOT MBL or OXA-48 |
| Cefiderocol |
2g IV q8h (3h infusion) |
MBL, KPC, OXA-48; also covers MDR Pseudomonas |
Reference: IDSA Guidance on Treatment of MDR Gram-Negative Infections 2022
Infection Control and Prevention
Standard Precautions and Transmission-Based Precautions
Standard Precautions (Applied to ALL Patients)
- Hand hygiene before and after patient contact
- Use of PPE when anticipating contact with blood, body fluids
- Safe injection practices
- Respiratory hygiene/cough etiquette
Transmission-Based Precautions
| Type |
Indications |
PPE Required |
Examples |
| Contact |
Direct contact or contact with contaminated surfaces |
Gloves + Gown |
MRSA, VRE, C. difficile |
| Droplet |
Large droplet transmission (>5 microns) |
Surgical mask |
Influenza, Pertussis, Meningococcal disease |
| Airborne |
Small particle transmission (<5 microns) |
N95 respirator + Negative pressure room |
Tuberculosis, Measles, Varicella |
Reference: CDC/HICPAC Guideline for Isolation Precautions 2017
Insertion Bundle
- Hand hygiene before insertion
- Maximal sterile barrier precautions
- Chlorhexidine skin antisepsis
- Optimal catheter site selection
- Daily review of line necessity
Reference: CDC Guidelines for Prevention of Intravascular Catheter-Related Infections 2011
Infections in Special Populations
Immunocompromised Patients
Febrile Neutropenia
Definition: Single temperature ≥38.3°C OR ≥38°C for ≥1 hour AND absolute neutrophil count <500 cells/mm³
Empiric Antibiotic Therapy (IDSA/ASCO 2018)
| Risk Category |
Recommended Regimen |
| High-risk (inpatient) |
Monotherapy: Cefepime 2g IV q8h OR Piperacillin-tazobactam 4.5g IV q6h OR Meropenem 1g IV q8h |
| Low-risk (outpatient) |
Ciprofloxacin 750mg PO BID + Amoxicillin-clavulanate 875/125mg PO BID |
Reference: IDSA/ASCO Guidelines for Febrile Neutropenia 2018
Management of Key Infections in Pregnancy
| Infection |
Maternal Treatment |
| UTI/Pyelonephritis |
Cephalexin, Amoxicillin-clavulanate, Ceftriaxone (avoid fluoroquinolones) |
| Group B Streptococcus (GBS) |
Intrapartum penicillin G 5 million units IV, then 2.5 million q4h |
Reference: ACOG Practice Bulletins, CDC STI Treatment Guidelines 2021
Emerging and Re-emerging Infectious Diseases
Mpox (Monkeypox)
Clinical Presentation
- Incubation: 3-17 days (average 7-14 days)
- Prodrome: Fever, headache, myalgias, lymphadenopathy
- Rash: Evolves from macules → papules → vesicles → pustules → scabs
Treatment (CDC 2023)
| Therapy |
Indication |
Dosing |
| Supportive care |
Most patients (immunocompetent with mild disease) |
Symptomatic treatment, isolation |
| Tecovirimat (TPOXX) |
Severe disease OR immunocompromised |
600mg PO BID × 14 days (with fatty meal) |
Reference: CDC Mpox Clinical Considerations 2023
CDC Urgent Threats (2019)
| Organism |
Key Points |
| Carbapenem-resistant Acinetobacter |
Limited treatment options; high mortality in ICU patients |
| Candida auris |
Multi-drug resistant; difficult to identify; outbreak potential |
| Carbapenem-resistant Enterobacterales (CRE) |
Resistant to nearly all antibiotics; new agents available |
Strategies to Combat Resistance
Individual Healthcare Provider Actions:
- Prescribe antibiotics only when necessary
- Use narrow-spectrum agents when possible
- Optimize dosing based on PK/PD principles
- Implement infection prevention measures
Reference: CDC Antibiotic Resistance Threats Report 2019
Clinical Classification (WHO 2009)
| Category |
Features |
Management |
| Dengue without warning signs |
Fever + nausea, rash, aches/pains |
Outpatient: oral rehydration |
| Dengue with warning signs |
Abdominal pain, persistent vomiting, mucosal bleeding |
Hospital admission: IV fluids |
| Severe dengue |
Severe plasma leakage, severe bleeding, organ impairment |
ICU admission: aggressive fluid resuscitation |
Treatment
No specific antiviral therapy
- Supportive care: IV fluid therapy is cornerstone
- Fever/pain: Acetaminophen (AVOID aspirin and NSAIDs)
Reference: WHO Dengue Guidelines 2009