Microbiology and Infection Control A topic that Bugs us Both Bruce Gamage, RN BSN BSc CIC BC Centre...
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Transcript of Microbiology and Infection Control A topic that Bugs us Both Bruce Gamage, RN BSN BSc CIC BC Centre...
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.