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?