Hospital-Acquired Infections

HAIs Intro - Hospital's Sneaky Germs

• Definition: Infections acquired during hospital stay; not present/incubating at admission. Also called Nosocomial Infections.
• Onset Criteria:
  • Develops ≥ 48 hours after hospital admission.
  • Within 3 days of discharge.
  • Within 30 days after an operation (or up to 1 year if implant present).
• Sources:
  • Endogenous: Patient's own flora (e.g., skin, gut).
  • Exogenous: External sources (e.g., healthcare staff, contaminated equipment, environment).
• Major Types & Common Pathogens:
  • CAUTI (Catheter-Associated UTI): E. coli, Klebsiella, Pseudomonas, Enterococcus, Candida.
  • SSI (Surgical Site Infection): S. aureus, Coagulase-negative Staphylococci, Enterococcus.
  • VAP (Ventilator-Associated Pneumonia): Pseudomonas, Acinetobacter, S. aureus (MRSA), Enterobacteriaceae.
  • CLABSI (Central Line-Associated Bloodstream Infection): Coagulase-negative Staphylococci, S. aureus, Candida.
• Impact: ↑ Morbidity, mortality, hospital stay, & healthcare costs.

⭐ The most common healthcare-associated infection worldwide is Catheter-Associated Urinary Tract Infection (CAUTI).

📌 Mnemonic (Common HAIs - "SCUM Vets"): SSI, CAUTI, Upper respiratory (like VAP), Meningitis (rare), Vascular access (CLABSI), ets (others like GIT infections).

CAUTI & CLABSI - Pipe Problems

Catheter-Associated Urinary Tract Infection (CAUTI)

• UTI with indwelling urinary catheter (IUC) >2 days.
• Pathogens: E. coli (most common), Klebsiella, Pseudomonas, Enterococcus, Candida.
• Prevention (📌 HANDS):
  • Hand hygiene.
  • Aseptic insertion, proper maintenance.
  • Necessity review daily.
  • Drainage bag below bladder, off floor.
  • Secure catheter.
• Diagnosis: Urine culture ≥$10^3$ CFU/mL.

Central Line-Associated Bloodstream Infection (CLABSI)

• Lab-confirmed BSI with central line >2 days.
• Pathogens: CoNS, S. aureus, Enterococcus, Gram-negatives, Candida.
• Prevention (📌 CLABSI BUNDLE):
  • Hand hygiene.
  • Maximal barrier precautions (insertion).
  • Chlorhexidine skin antisepsis.
  • Optimal site selection (subclavian > jugular > femoral).
  • Daily review of line necessity & prompt removal.
  • Hub disinfection ("Scrub the Hub").

⭐ Differential Time to Positivity (DTP): Blood culture from CVC positive ≥2 hours before peripheral culture strongly suggests CLABSI.

VAP & SSI - Breath & Breach Bugs

Ventilator-Associated Pneumonia (VAP):

• Pneumonia developing >48 hours after endotracheal intubation.
• Early-onset (<5 days): S. pneumoniae, H. influenzae, MSSA.
• Late-onset (>5 days): Pseudomonas aeruginosa, Acinetobacter spp., MRSA.
• Prevention: Head elevation (30-45°), oral chlorhexidine, daily sedation interruption, early weaning, subglottic suctioning.

Surgical Site Infection (SSI):

• Infection at/near surgical incision within 30 days (or 1 year if implant present).
• Types: Superficial incisional, Deep incisional, Organ/space.
• Common bugs: Staphylococcus aureus (most common), CoNS, Enterococcus spp., E. coli.
• Prevention: Prophylactic antibiotics (~60 min pre-incision), clippers (not razor), aseptic technique, post-op wound care.

⭐ Most SSIs are caused by the patient's endogenous flora, particularly skin flora like Staphylococcus aureus.

AMR & Surveillance - Resistance Watch

• Antimicrobial Resistance (AMR): Major threat in HAIs, increasing morbidity, mortality, and costs.
  • Driven by antibiotic overuse and misuse.
  • Key pathogens (📌 ESKAPE): E. faecium (VRE), MRSA, CRE (K. pneumo), A. baumannii, P. aeruginosa, Enterobacter.
• Surveillance Systems: Essential for tracking AMR patterns and informing interventions.
  • National: NCDC (National Programme on AMR Containment), ICMR AMR Network.
  • Global: WHO GLASS, WHONET software.
• Antimicrobial Stewardship (AMS): Programs to promote appropriate antibiotic prescribing.
  • Aims: Improve patient outcomes, reduce toxicity, and ↓selective pressure for AMR.
  • Core strategies: Prospective audit & feedback, formulary restriction, education.

⭐ Carbapenem-Resistant Enterobacteriaceae (CRE) are a critical priority in HAIs due to extensive drug resistance and associated high mortality rates.

High‑Yield Points - ⚡ Biggest Takeaways

• Most common HAI: Catheter-Associated UTI (CAUTI).
• Common ICU pathogens: S. aureus (MRSA), P. aeruginosa.
• Ventilator-Associated Pneumonia (VAP): Develops >48 hrs post-intubation. Prevention: head elevation.
• CLABSI prevention: Strict aseptic technique for central line insertion and care.
• Surgical Site Infection (SSI): Within 30 days (or 1 year with implant). Prophylaxis: antibiotics ~60 mins pre-op.
• Hand hygiene: Most crucial HAI prevention; alcohol-based rubs preferred.
• Standard precautions: Apply to all patients to prevent transmission.