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NOSOCOMIAL INFECTION
Nosocomial infections (NCI)
"nosus" = disease
"komeion" = to take care of
Infections that occur during hospitalization but are not present nor incubating upon hospital admission
History of Nosocomial Infection
• Ignaz Semmelweis, (1840s) demonstrated importance of hand hygiene
• No progress for next century• 1976, the Joint Commission on
Accreditation of Healthcare Organizations - standards for infection control
• Nosocomial infection still on the increase - emerging infection
Nosocomial Infections
• 5-10% of patients admitted to acute care hospitals acquire infections– 2 million patients/year– ¼ of nosocomial infections occur in ICUs– 90,000 deaths/year– Attributable annual cost: $4.5 – $5.7 billion
• Cost is largely borne by the healthcare facility not 3rd party payors
Weinstein RA. Emerg Infect Dis 1998;4:416-420.Jarvis WR. Emerg Infect Dis 2001;7:170-173.Weinstein RA. Emerg Infect Dis 1998;4:416-420.
Jarvis WR. Emerg Infect Dis 2001;7:170-173.
Nosocomial Infections
• 70% are due to antibiotic-resistant organisms
• Invasive devices are more important than underlying diseases in determining susceptibility to nosocomial infection
Burke JP. New Engl J Med 2003;348:651-656.Safdar N et al. Current Infect Dis Reports 2001;3:487-495.
Major Sites of Nosocomial Infections
• Urinary tract infection
• Bloodstream infection
• Pneumonia (ventilator-associated)
• Surgical site infection
• Virtually all microorganisms can cause nosocomial infections
• Viruses
• Bacteria
• Fungi
• Parasites
CAUSES OF HCAI
• BacteriaBacteria
• Gram +Gram +– Staphylococcus aureus– Staphylococcus epidermidis
• Gram -Gram -– Enterobacteriaceae – Pseudomonas aeruginosa– Acinetobacter baumanni
• Mycobacterium tuberculosisMycobacterium tuberculosis
BACTERIABACTERIA
• VirusesViruses– Blood borne
infections : HBV, HCV, HIV
– Others: CMV, rubella,
varicella, SARS
• FungiFungi– Candida – Aspergillus
NOSOCOMIAL PATHOGENSNOSOCOMIAL PATHOGENS
SOURCES OF INFECTIONSOURCES OF INFECTION
EndogenousEndogenoussource is the normal flora or source is the normal flora or
colonisers of skin and other colonisers of skin and other epithelial surfacesepithelial surfaces
ExogenousExogenousother persons (cross-infection)other persons (cross-infection)
inanimate objects (fomites)inanimate objects (fomites)
TYPES BY ORIGIN
1.Endogenous: Caused by the organisms that are present as
part of normal flora of the patient
2. Exogenous: caused by organisms acquiring by exposure to hospital personnel, medical devices or hospital environment
Downloaded from: Principles and Practice of Infectious Diseases
© 2004 Elsevier
Up to 20% of skin-associated bacteria in skin appendages (hair follicles, sebaceous glands) & are not eliminated by topical antisepsis. Transection of these skin structures by surgical incision may carry the patient's resident bacteria deep into the wound and set the stage for subsequent infection.
The inanimate environment is a reservoir of pathogens
~ Contaminated surfaces increase cross-transmission ~
Abstract: The Risk of Hand and Glove Contamination after Contact with a VRE (+) Patient Environment. Hayden M, ICAAC, 2001, Chicago, IL.
X represents a positive Enterococcus culture
The pathogens are ubiquitous
The inanimate environment is a reservoir of pathogens
Recovery of MRSA, VRE, C.diff CNS and GNR
Devine et al. Journal of Hospital Infection. 2001;43;72-75
Lemmen et al Journal of Hospital Infection. 2004; 56:191-197
Trick et al. Arch Phy Med Rehabil Vol 83, July 2002
Walther et al. Biol Review, 2004:849-869
The inanimate environment is a reservoir of pathogens
Recovery of MRSA, VRE, CNS. C.diff and GNR
Devine et al. Journal of Hospital Infection. 2001;43;72-75
Lemmen et al Journal of Hospital Infection. 2004; 56:191-197
Trick et al. Arch Phy Med Rehabil Vol 83, July 2002
Walther et al. Biol Review, 2004:849-869
The inanimate environment is a reservoir of pathogens
Recovery of MRSA, VRE, CNS. C.diff and GNR
Devine et al. Journal of Hospital Infection. 2001;43;72-75
Lemmen et al Journal of Hospital Infection. 2004; 56:191-197
Trick et al. Arch Phy Med Rehabil Vol 83, July 2002
Walther et al. Biol Review, 2004:849-869
SPREAD OF INFECTONSSPREAD OF INFECTONS
Air-borneAir-borneSkin scales, droplet nuclei
ContactContactDirect
HandsHands & clothing
Droplet contact followed by autoinoculation
Clinical equipment
Indirect
Bedpans, bowls, jugs, etc
SPREAD OF INFECTONSSPREAD OF INFECTONS
The hands are the most importantvehicle of transmission of HCAI
Nos
ocom
ial I
nfec
tions
Com
prom
ised
Hos
ts
Com
prom
ised
Hos
ts
Nos
ocom
ial I
nfec
tions
Exogenous Infections
Exogenous Infections
Endogenous Infections
Nos
ocom
ial I
nfec
tions
Chain of Transmission
Universal Precautions
Universal Precautions
PRACTISE STANDARD PRECAUTIONS
CONTROL OF HCAI
Hand hygiene is thesingle most importantmeasure for controlof nosocomial infections
TYPES OF HAND HYGIENE PROCEDURES
• Hand washing– Hand washing is usually limited to hands and wrists– Hands are washed for a minimum of 10 – 15 seconds with soap
(plain or antimicrobial) and water– Transient micro-organisms are mechanically removed by rinsing.
• Hand antisepsis/decontamination– Hand antisepsis removes or destroys transient micro-organisms and
confers a prolonged effect. – Two ways:
• Wash hands and forearms with antimicrobial soap and water, for 15-30 seconds
• Decontaminate hands with a waterless, alcohol-based hand gel or hand rub for 15-30 seconds. Appropriate for hands that are not soiled with protein matter or fat.
TYPES OF HAND HYGIENE PROCEDURES
• Surgical hand antisepsis– Removes or destroys transient micro-organisms and
confers a prolonged effect. – Hands and forearms are washed thoroughly with an
antiseptic soap for a minimum of 2-3 minutes. – Hands are dried using a sterile towel.– Required before performing invasive procedures.
Alcohol based hand hygiene solutionsQuick Easy to use
Very effective antisepsis due to bactericidal properties of alcohol
Hand Hygiene
• Single most important method to limit cross transmission of nosocomial pathogens
• Multiple opportunities exist for HCW hand contamination– Direct patient care– Inanimate environment
• Alcohol based hand sanitizers are ubiquitous– USE THEM BEFORE AND AFTER PATIENT
CARE ACTIVITIES
HAND WASHING TECHNIQUE
Source: World Health Organization. Regional Office for Western Pacific.
PROTECT YOURSELF PROTECT YOURSELF THROUGH IMMUNISATIONTHROUGH IMMUNISATION
ImmunisationImmunisationBCGBCG
Hepatitis BHepatitis B
TetanusTetanus
RubellaRubella
VaricellaVaricella
InfluenzaInfluenza
Che
mic
al
Ant
imic
robi
als
Agent Mechanisms of Action Comments
Surfactants Membrane Disruption; increased penetration
Soaps; detergents
Quats (cationic detergent)
Denature proteins; Disrupts lipids
Antiseptic - benzalconium chloride, Cepacol; Disinfectant
Organic acids and bases
High/low pH Mold and Fungi inhibitors; e.g., benzoate of soda
Heavy Metals Denature protein Antiseptic & Disinfectant; Silver Nitrate
Halogens Oxidizing agent Disrupts cell membrane
Antiseptic - Iodine (Betadine) Disinfectant - Chlorine (Chlorox)
Alcohols Denatures proteins; Disrupts lipids
Antiseptic & Disinfectant Ethanol and isopropyl
Phenolics Disrupts cell membrane
Disinfectant Irritating odor
Aldehydes Denature proteins Gluteraldehyde - disinfectant (Cidex); Formaldehyde - disinfectant
Ethylene Oxide Denaturing proteins Used in a closed chamber to sterilize
Oxidizing agents Denature proteins Hydrogen peroxide – antiseptic; Hydrogen peroxide – disinfectan; Benzoyl peroxide – antiseptic
Phy
sica
l A
ntim
icro
bial
s
Agent Mechanisms of Action Comments
Moist Heat, boiling Denatures proteins Kills vegetative bacterial cells and viruses Endospores survive
Moist Heat, Autoclaving
Denatures proteins 121°C at 15 p.s.i. for 30 min kills everything
Moist Heat, Pasteurization
Denatures proteins Kills pathogens in food products
Dry Heat, Flaming Incineration of contaminants
Used for inoculating loop
Dry Heat, Hot air oven
Oxidation & Denatures proteins
170°C for 2 hours; Used for glassware & instrument sterilization
Filtration Separation of bacteria from liquid (HEPA: from air)
Used for heat sensitive liquids
Cold, Lyophilization (also desiccation)
Desiccation and low temperature
Used for food & drug preservation; Does not necessarily kill so used for Long-term storage of bacterial cultures
Cold, Refrigeration Decreased chemical reaction rate
Bacteriostatic
Osmotic Pressure, Addition of salt or sugar
Plasmolysis of contaminants
Used in food preservation (less effective against fungi)
Radiation, UV DNA damage (thymine dimers)
Limited penetration
Radiation, X-rays DNA damage Used for sterilizing medical supplies
Strong vis. Light Line-drying laundry
Conclusion
Hospital Pathogen Unhappypatients
Unhappydirector
Hospital Surveillance HappyPatients
Happydirector
Hands Spread Disease
Why disinfection and sterilization?
• Contagious diseases• Hospital infection (e.g., OR, ID ward)
or other opportunistic infection • Lab contamination, etc. • Microbes:
- usually easy to grow in environment; - but also can be inhibited or killed by certain
environmental (physical or chemical) factors/conditions.
Terminology
• Disinfection
• Sterilization
• Bacteriostasis
• Antisepsis
• Asepsis
Disinfection
• Process of reducing or eliminating living pathogenic microorganisms in or on materials, so they are no longer a health hazard.
For example: use of alcohol before drug injection.
Sterilization
• Process of destroying all microbial forms. A sterile object is one free of all microbial forms, including bacterial spores.
• More thorough than disinfection
Bacteriostasis
• Process of inhibiting the growth of microorganisms, in vivo (mostly) or in vitro
For example: bacteriostatic antibiotics
Antisepsis
• Process of inhibiting or preventing growth of microbes, mostly in vitro and not bactericidal or sporicidal
For example: use of chemical agents on skin, other living tissues or food/beverage.
Asepsis
• A state where no living microorganism exists.
For example: OR (Operating Room)
Controlling Microorganisms with Physical Conditions
• High Temperature (heat)
• Radiation
• Ultrasound
• Filtration
• Low Temperature
• Desiccation
High Temperature ——Dry heat and Moist heat protein denaturation
and clotting; DNA strand breakdown
static action cidal action .
Dry heat : protein oxidation
• Incineration– most thorough (>500 )℃– disposals and corpes
• Flaming (burner) – test tube opening, transferring loop
• Hot air sterilization/Baking– 160-170 , 2h℃– Glassware, syringes, needles, etc
• Infrared heat: similar to baking
Moist heat : denaturing proteins and melt lipids• Autoclaving
– Most commonly used and effective– 121 (103℃ .4kPa), 15-20min– killing both vegetative organisms and
endospores
• Boiling– 100 (105 with 2% Na℃ ℃ 2CO2) , 15-20min– cidal for vegetative cells but not necessarily spores
• Regular Steam (Arnold Sterilizer)– 100 , 15-20min℃– cidal for vegetative cells but not necessarily spores
• Pasteurization– to kill pathogens in readily perishable objects (milk,
wine)– flash method : 71.6 , 15s ℃– holding method : 62.9 , 30 min℃
• Fractional sterilization– alternating exposure and cooling time for a
consecutive period:Steam heating (100 , 30 min) ℃ 30 for ℃
endospores to germinate 100 , 30 min to kill ℃germinated endospores 30-37 overnight for ℃remaining endospores to germinate 100 , 60 min to ℃kill last remaining germinated endospores
– for sugar- or milk-containing culture media
Moist Heat vs Dry Heat
Moist heat Dry heat
Penetrating potency higher lower
Temp for protein clotting lower higher
Extra heat released yes no
from condensation
Sterilizing potency: Moist heat >> Dry heatSterilizing potency: Moist heat >> Dry heat
Radiation • Ultraviolet (UV) radiation
– mechanism: blockage of DNA replication by forming thymidine dimmers
– microbicidal activity of UV depends on:• length of exposure • wavelength: 200-300 nm, with the best effect of 265-266nm• bulb life (4000hr)
– very poor penetrating power– for air or surface disinfection
(OR, ID ward, labs) – causing eye damage, burns
and mutation in skin cells
• Ionizing Radiation– X-rays, gamma rays and high-speed electrons – generating more energy and penetrating power
than UV– to sterilize pharmaceuticals, disposable medical
supplies (e.g., syringes, gloves, catheters, sutures) and foods
• Microwave – penetrating non-metal materials (glass, plastics)
• Ultrasound– more effective for gram-negative bacteria– Lack of thoroughness —— survivors remain
• Filtration – sterilize heat- or chemical-sensitive solutions– not effective for virus, ricketia, mycoplasma
Seitz filter
• Desiccation– static effect by inhibiting microbial enzymes– not effective against endospores– mainly for food reservation
• Low Temperature (-20 ℃ ~ -70 )℃– inhibits microbial growth by slowing down
microbial metabolism– a special form: lyophalization (freeze-drying),
used for long-term (years) reservation of bacteria stocks
• fast freezing + drying• protecting agents (glycerol, serum)
Control Microorganisms with Chemical Agents
(Disinfectants and Antiseptics)
Antimicrobial modes of action of disinfectants and antiseptics
• Denaturation of bacterial proteins by disrupting hydrogen and disulfide bonds—— phenol (high conc.), alcohol, heavy-metal (high conc.),
acids, alkalies, aldehydes)
• Damage to bacterial membrane (lipids and/or proteins), causing leakage of intracellular molecules—— phenol (low conc.), surfactants, dyes
• Interference of bacterial enzyme and metabolism—— oxidants, heavy-metals (low conc.), alkylating agents
• Phenol and phenol derivatives —— altering membrane permeability and
denaturing proteins
• 0.01% - 0.05% Chlorhexidine —— vaginal wash, OR hand-wash
• 3% - 5% carbonic acid or 2% Lysol —— floor or surface disinfection
• Alcohols —— denaturing bacterial proteins and
membranes
• 70% - 75% ethyl or isopropyl alcohol —— skin and thermometer disinfection
– ineffective against endospores and non-enveloped viruses
• Heavy metals (Hg2+ 、 Ag+)
—— denaturing proteins and inactivating enzymes
• 2% mercurochrome or 0.1% merthiolate —— skin, mucosa and wound
– bacteriostatic, ineffective against endospores
• 1% silver nitrate —— eye drops for newborns to prevent gonococcal ophthalmia
• Oxidants
—— oxidation, protein precipitation
• 0.1% potassium permanganate —— skin, fruits/vegetables
• 3% peroxiden —— small trauma wound, skin, mucosa
• 0.2% - 1% peroxyacetic acid —— plastics, glassware
• 0.2 – 0.5 ppm cholorines —— water and swimming pool
• Surfactants
—— damaging bacterial membranes, inactivating enzymes, protein precipitation
• 0.05-0.1% bromogeramine —— OR hand-wash, skin, surgical instruments
• Alkylating agent
—— alkylating proteins and nucleic acids
• formalin (formaldehyde) —— surface disinfection, air, surgical instruments
• glutaric dialdehyde —— high-precision instruments, endoscopes
• 50mg/L epoxy ethane —— surgical instruments and dressing
• Dyes
—— inhibiting bacterial growth by interfering with oxidation
• 2% - 4% methyl violet —— wound disinfection
• Acids and alkalies
—— destroying cell membrane and cell wall, denaturing proteins
• 5-10ml/m3 acetic acid evaporation —— air disinfection
• quicklime [Ca(OH)2] —— floor and excretion (feces, urine, sputum, pus) disinfection
Effectiveness of antimicrobial agents are affected by :
• The concentration/intensity and nature of the disinfectant;
• Length of exposure;• Species and number of the microbe(s); • Temperature and humidity;• Acidity (pH);• Presence of organic substances;• Presence of chemical antagonists• The nature of the material bearing the microbes
Summary 1. Application of chemical disinfectants
Patient excretion Chlorines, 5% carbonic acid, 2% Lysol
Skin (hands) 2% Lysol, 0.2-0.4% peroxyacetic acid for HBV, 70% ethyl alcohol, 2% mercurochrome
Mucosa oral - 3% peroxide; uri-reproductive - 0.01-
0.05%Chlorhexidine, 0.1% potassium permanganate ;
newborn eyes - 1% silver nitrate
Drinking water Chlorines
Toilets, sewage quicklime [Ca(OH)2]
Air (OR, ID ward) formalin steam (12.5-25ml/m3,12-24h),formalin 40ml + potassium permanganate
30g/m3;HBV ward- peroxyacetic acid 3g/m3 90min
Glassware, china, 0.5% iodophores, 0.2-0.4% peroxyacetic Rubber, metal aciddevices
Potency Definition Examples
High Killing all microbes including glutaric dialdehyde, endospores and TB formaldehyde peroxyacetic acid,
epoxy ethane
Medium Killing all non-spore microbes alcohol, chlorines, including TB iodophores
Low Killing vegetative bacteria chlorhexidine, and lipophilic (enveloped) bromogeramine
viruses, but resisted by endospores, TB and hydrophilic (non-enveloped) viruses
Summary 2. Potency levels of chemical disinfectants
Spore-killing disinfectants
– glutaric dialdehyde, formaldehyde, Iodines,
H2O2, epoxy ethane
Non spore-killing disinfectants
– alcohols, phenols, chlorhexidine,
bromogeramine
Summary 3. Spore-killing effects of chemical disinfectants
Disinfection and Disinfection and SterilizationSterilization
——For the course of Medical Microbiology for MBBS foreign students, Class 2006/2011, SYSU
September 18, 2007
Mengfeng Li (黎孟枫) , M.D. Department of Microbiology, Zhongshan School of
Medicine, SYSU, Guangzhou, China
limf@mail.sysu.edu.cn
Medical Microbiology Medical Microbiology
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