Infection Control
Friday 1/11/08
Spread of resistance
Antibiotic pressure
Human to human transmission
Modes of transmission of ID
• Contact– Most important & frequent route of transmission for NI
• Droplet – Droplets > 5m containing microorganisms
• Airborne– Droplet nuclei <5 µm containing microorganisms
• Common Vehicle– Transmitted by contaminated items
• Other:– Fecal-Oral– Sexual– Vectorborne
Nosocomial vs. Community spread
Infection control - preventing transmission of pathogens
(focus on resistant ones)
• Surveillance
• Barrier precautions (= standard + contact precautions)– Isolation / cohorting– Gown– Gloves– Hand washing/alcohol
The need for active surveillance (Harris et al.):
• Undetected ratio =
patients undetected by clinical cultures all patients colonized or infected
• Higher ratio - more effective will active surveillance be
(estimates: VRE ~90%, MRSA ~90%, GNR-MDR - lower).
Infection control - preventing transmission of pathogens
(focus on resistant ones)
• Surveillance
• Barrier precautions (= standard + contact precautions)– Isolation / cohorting– Gown– Gloves– Hand washing/alcohol
Standard precautions
• Wash hands with plain soap after touching blood, body fluids, excretions, or contaminated items whether or not gloves are worn.
• Wear gloves when touching blood, body fluids, excretions, and contaminated items.
• Put on clean gloves before touching non-intact skin or mucous membranes.
• Change gloves between procedures on the same patient involving contact with high concentration of organisms.
• Remove gloves and wash hands before touching the environment or other patients.
• Wear mask and eye protection and gown during procedures causing splashes of blood or body fluid.
Contact precautionsAs standard precautions, plus:
• Patient placed in single room or in a room with patients who have active infection with the same microorganism but no other infection (cohorting).
• Wear gloves when entering the room.
• Change gloves after contact with high concentration of microorganisms.
• Remove gloves and wash hands with antiseptic agent when leaving patient’s environment.
• Wear gown in the room if in contact with patient, environment, or if patient incontinent.
• Remove gown before leaving room.
• Avoid sharing of patient equipment.
Search & Destroy strategy
• Selective screening of high risk groups– Defining high risk groups– Defining methods of screening
• Subsequent isolation of colonized persons
• Decolonization
S&D in highly endemic settings –is it feasible?
• Bootsma et al – Math model – supports
• Clancy et al. and Huang et al. – support
Bootsma et al. PNAS 2006
Studies that test effectiveness of IC interventions
• Descriptions of interventions to control outbreaks – defining a causal relation.
• Quasi-experimental designs (before-after studies)
• Randomized controlled intervention trials (None to date – why??)
• Mathematical models
Klebsiela pneumoniae with carbapenemase in Israel
(true story but hypothetical data)
0
2
4
6
8
10
12
14
16
18
1 2 3 4 5 6 7 8 9 10 11 12
Kpc
Causal relationship
• Cause precedes effect
• Cause covary with effect
• Alternative explanations for the causal relationship are implausible
Types of Quasi-experimental designs
• Quasi-experimental designs without control groups
• Quasi-experimental designs with control groups
• Interrupted time-series designs (with/wo controls)
MRSA bacteremia / Huang et al. CID 2006
Screening is effective (MRSA infections in SICU) / Clancy et al. Infect cont & Hosp Epidemiol
Can IC interventions prevent antibiotic resistance??
Quasi-experimental designs
• What can we learn from them?
• What are the limitation of these studies?