Microbiology and Infection Control

A topic that Bugs us Both

Bruce Gamage, RN BSN BSc CIC

BC Centre for Disease Control

Outline

Definitions Nosocomial Infections Routine Practices and Transmission-

Based Precautions Antibiotic Resistant Organisms Microbiology Laboratory and Infection

Control

Definitions

Colonization: Presence of microorganisms in or on a host with growth and multiplication but without tissue/cell invasion and inflammation.

Infection: The entry and multiplication of a infectious agent in the tissues/cells of a host.

Definitions

Inflammation: The succession of changes that occur in living tissue when it is injured.

Symptoms are: Pain (dolar), heat (calor), redness (rubor), swelling (tumor), impaired function, general feeling of discomfort.

Definitions

Nosocomial infection: An infection that was not present or incubating at the time of admission to the facility. The infection becomes apparent 72 hours after admission.

Community infection: An infection apparent at the time of admission or during the first 72 hours of admission.

Definitions Normal flora: Consists of relatively fixed types

of microorganisms regularly found in a given area and when washed promptly reestablish themselves.

Transient flora: Consists of microorganisms that inhabit the skin or mucous membranes for hours, days, or weeks, derived from the environment, generally does not produce disease and does not establish itself permanently on the host. Transient flora may colonize, proliferate and produce disease.

Chain of InfectionCausative agent

Portal of entry Reservoir

Susceptible host Portal of exit

Mode of transmission

When the chain of infection is broken the infectious process is halted.

Nosocomial Infections

Risk Factors• Steroids, chemotherapy, Antibiotics

• Invasive devices, procedures

• Virulence of pathogens

• Prolonged hospital stay

Routine Practices

Routine infection control practices are the minimum level of precautions that should be used with all patients, at all times, regardless of presumed infectious status.

Hand Washing/Hand Antisepsis Hands must be cleaned: After any direct contact with a

patient, before contact with the next patient

Before performing invasive procedures

After contact with blood, body fluids, secretions and excretions and exudates from wounds

After contact with items known or likely to be contaminated

Immediately after removing gloves

Alcohol-based hand antiseptics

Alcohol-based hand antiseptics are superior to soap and water in reducing hand contamination and should be made available as an alternative to hand washing

Gloves

Gloves should be used as an additional measure, not as a substitute for hand washing

Not required for routine patient care activities in which contact is limited to a patient's intact skin

For contact with blood, body fluids, secretions and excretions, mucous membranes, draining wounds or non-intact skin.

Masks and Eye Protection

Masks and eye protection or face shields should be worn:

To protect the mucous membranes of the eyes, nose and mouth

During procedures likely to generate splashes or sprays of blood, body fluids, secretions or excretions.

Mask vs. Respirator

A fluid resistant surgical or procedural mask should be worn to protect mucous membranes from splashes of body fluids

Mask vs. Respirator

If protection is required from airborne or aerosolized pathogens then a NIOSH or equivalent approved, N95 respirator must be worn

Gowns

Gowns should be used to: Protect uncovered skin and

Prevent soiling of clothing

During procedures and patient care activities likely to generate splashes or sprays of blood, body fluids, secretions, or excretions

Sharps Safety

Handle sharps/equipment safely

Sharp items should be placed immediately in puncture-resistant containers located in the area where the items were used.

Transmission-based Precautions

Airborne Precautions

Droplet Precautions

Contact Precautions

Transmission Routes and Precautions

Airborne Pulmonary Tb

Rubeola

Varicella (Chicken Pox)

Hemorrhagic fevers

N95 particulate respirator Eye ProtectionClose door, NP Hand cleaning

Droplets Influenza

Meningococcal meningitis

Mumps, Pertussis, Rubella

Upper respiratory Infections

Surgical maskEye protection Hand cleaning

Direct Contact

Infectious diarrhea,

Major burn wound infection

Hepatitis A, E

Scabies, Zoster

Viral respiratory infection

ARO

GlovesFluid resistant gown Hand cleaning

Antimicrobial-Resistant Organism

Definition:

“An organism that is resistant to two or more unrelated antibiotics to which the organism is normally considered susceptible.”

Bennett and Brachman, 4th edition.

Emergence of AROs

Factors That Promote Resistance

Resistance genes are prevalent in nature Rapid multiplication of organisms favors

genetic mutations Selective pressure from antimicrobial

use in humans and animals allows resistant organisms to predominate

Biofilms?

MRSA: Epidemiology

In the US MRSA is endemic in majority of hospitals (36% of all S. aureus isolates)

In Canada (CNISP)1995 0.9% of S. aureus isolates and 0.3

cases per 1000 admissions

1999 6% of S. aureus isolates and 4.12 cases per 1000 admissions

BCCAMM Surveillance ProjectTime

period Total new

MRSA patients

Total S.aureus

isolates

Approx %MRSA

Total

Approx %MRSA

Range

Approx %MRSA

Median

Total 2002 2504 27641 9.1% 1.3% - 62.7%

6.8%

Total 2003 3122 29991 10.4% 2 - 51% 10.7%

Total 2004 3122 33019 14.4% 6 - 33% 12.3%

World-Wide Prevalence of MRSA

Canada (6%)

USA (36%)

UK (42%) Denmark (<1%) Europe (24%)

Japan (74%)

China (39%)

Hong Kong (80%)

Australia (30%)India (34%)South Africa (49%)

Latin America (29%)

VRE: Epidemiology

In US: 1995 > 10% of enterococcal strains VRE

In Canada:First VRE reported in 1993

411 cases reported in 23 hospitals between October 1998-September 2000

95% are colonization picked up on screening

BCCAMM Surveillance Project

Time period Total new VRE patients Estimate of VRE as % of all enterococci

Total 2002 43 <1%

Total 2003 45 <1%

Total 150 Probably no more than 1%

VISA and VRSA

VISA first recognized in 1996 in Japan Additional cases reported from Europe, Asia,

and the US

Resistance has not been caused by the vanA, vanB, or vanC genes

VRSA seen in US in 2002Resistance gene vanA was detected in the

isolate

No detected transmission to others

Control of ARO

Screening Cultures Contact Precautions Environmental Disinfection Antibiotic Controls HCW/Public Education

Role of the Microbiology Laboratory

Organism ID and susceptibility Monitor antibiotic resistant organisms Notifying IC of significant findings Outbreak Investigations Strain typing Reportable organisms

Typing Methods

• Phenotypic – observable characteristic

(genes and environment interacting)

• Genotypic – genetic constitution –

examination of DNA

Phenotypic Typing Methods Widely available for several decades

May be quicker and more readily available (but not

always)

Examples

Antibiotic resistance typing – many bacteria

Serotyping – eg Salmonella, Neisseria meningitidis

Antibiotic Resistance Typing(Antibiogram)

MRSA (+ urease tube)

Serotyping Well established method – often being superseded by

genotyping

Antibodies to variable antigens (often cell wall or cell

membrane) prepared and, with a choice of methods (e.g.

latex agglutination, ELISA) used to assign an isolate to a

group or type.

Still used for Salmonella ‘speciation’, also Legionella.

Genotypic Typing Methods

More recently developed and often more expensive

Less readily available (usually at reference lab) and slower

even if ‘on site’

Examples

PCR (ribotyping)

Restriction enzyme based typing e.g. Pulsed Field Gel Electrophoresis

Sequence based methods

PCR based Typing

Use PCR to produce multiple amplicons whose size distribution

varies from strain to strain and which can be separated by gel

electrophoresis

Can be used in Staph. aureus – initial investigation to show that isolates

are not closely related or need further investigation (PFGE)

Relatively quick but quite difficult to standardize between

laboratories

Pulsed Field Gel Electrophoresis

Extract DNA and cut with specific restriction enzyme to give

characteristic pattern of fragment sizes

Choice of enzymes – large or small fragments

Small fragments – easier to separate but less standardized

Large fragments – need special equipment to separate (PFGE)

Still fairly slow (2-3 days) but standard for many organisms now

e.g. E .coli O157, Staphylococcus aureus

PFGE (MRSA)

Sequence-Based Typing

Automatable process (computer analysis

necessary)

‘Digital’ results - easier comparison

between labs

More expensive (at present)

Can choose level of discrimination

Coarse – multiple stable genes – look at long

term evolutionary trends

Finer – fewer, variable gene(s) - outbreak

investigation / local surveillance

Reportable Diseases

List of diseases reportable by all sources/laboratories

http://www.bccdc.org/content.php?item=7 Liason between IC and public health

Summary

Follow Routine Practices Read the signs on the door Work with infection control Reportable diseases

Special thanks to:• Mary McNaughton RN, MSA, CIC

• Jim Curtin RN, BScN, CIC

Resources Health Canada: Routine practices and transmission-

based precautions in health care http://www.hc-sc.gc.ca/pphb-dgspsp/publicat/ccdr-rmtc/99vol25/25s4/index.html

Mayhall, C.G. Hospital Epidemiology and Infection Control. 2nd Edition. Lippincott, Williams & Wilkins. 1999.

Pfeiffer, J. A. APIC Text of Infection Control and Epidemiology. Association for Professionals in Infection Control and Epidemiology. Inc. 2005.