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HCV infection in health care workers and methodic approaches to identify HCV contamination. Tamara Amvrosieva , Natallia Paklonskaya, Olga Kazinethz Republican Research and Practical Center for Epidemiology and Microbiology, Minsk, Belarus. - PowerPoint PPT Presentation
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HCV infection in health care workers and methodic
approaches to identify HCV contamination
Tamara Amvrosieva,
Natallia Paklonskaya, Olga Kazinethz
Republican Research and Practical Center for Epidemiology and Microbiology,
Minsk, Belarus
Potential Modes of HCV Transmission in Health Care Settings
Direct contact with blood Needle stick or sharps injury Splash to eye Non-intact skin Blood transfusion/organ transplant
Indirect contact with blood
Hemodialysis HCW hands Re-used equipment (e.g., glucose monitoring,
syringes, needles) Injectable medication, infusion, flush solution
HCV Transmission in the health care setting
Patient to Health Care Workes percutaneous exposure to infected patients’ blood: multiple case reports
- splashes of blood onto health care workers’ (HCW) mucous membranes: few case reports
Health Care Workes to Patient
Patient to patient
Patient to Health Care Workes
Conflicting results on the risk of HCV transmission
The number of health care workers who have acquired HCV occupationally is not known. However, of the total acute HCV infections that have occurred annually 1% to 10% have been in health care workers exposed to blood in the workplace
Risk of Health Care Workers HCV infection following needlestick/cut from a positive (infected) source:
1.8% (range 0%-7%)
Frequency of Percutaneous Injury in Health care Personnel
Frequency of percutaneous injury varies by occupational group and healthcare setting
Prevalence of HCV Infection in health care workers United States
Group % Infection Hospital-based (pre-1980) 1-2Oral surgeons (1992) 2General surgeons (1991-1992) 1Orthopedic surgeons (1991) 1General dentists (1992) 1Emergency response (1991-2000) 1-3General population of adults 1.8
Factors Influencing OccupationalRisk of HCV Infection
Prevalence of infection among patients
Immune status of the worker and specific immune response of the infected individual
The type/route of exposure
The amount of virus in the infected blood at the time of exposure
The amount of infected blood involved in the exposure
Nature and frequency of blood exposures (for example splash to mucous membranes, cut,
needlestick, skin contamination, quantity of blood involved and concentration of HCV in the blood)
Whether post-exposure treatment was taken
Health Care Workes to Patient
Orthopaedic Surgery (Ross 2002)Cardiothoracic Surgery (Esteban1996)Gynaecology (PHLS 1999, Ross 2002)Anaesthesiology (Ross 2000)
Transmission mechanism:Percutaneous injury
Injection material shared with patients
HCV transmission: HCWs to patient(Gunson et al. J. Clin. Virol. 2003)
Nosocomial infection
Infection acquired in the hospital
due to exposure to the pathogen
in the hospital
Problematic aspects
of the HCV Transmission in Healthcare Settings
Risk factors for Healthcare Settings transmission not well definedHowever, HCV environmental transmission is a proven and documented fact, although HCV rapidly degrades at room temperatureAlthough some factors (e.g. virus titer) might be related to transmission of HCV, no methods exist currently that can reliably determine infectivity, nor do data exist to determine threshold concentration of virus required for transmission.
The investigetion includes two stages:
1. Detection and identification of
environmental HCV contamination (Laboratory Environmental Control)
2. Establishment of a connection between HCV contamination of health care setting and nosocomial transmission.
Determine whether transmission took place
1. Lanoratory Environmental Control
Main objective: envinronmental and virological investigations of health care settings to catch HCV particles and concentrate them in a small volume
The development of effective methods to identify HCV contamination in health care
settings (equipment, surfaces, clothing, bedding, body of medical personnel, etc.)
is an actual and poorly understood problem of environmental virology today.
Health care setting - a very broad term and wide range of….
Equipment
Devices
Surfaces
Medical procedures
Bedding
Clothes
Medical personnel
Patients
Etc........
Two main types of envinronmental samples from health care setting
Swabs Extracts
Equipment Devices
Surfaces
Etc........
Clothes
Bedding
Bandages, cotton wool
Etc........
Sample preparationSwabs processing:
1. Specific extracting buffers should be used to moisten swabs.
2. Moistened swabs should be employed for all sampling of surfaces.
3. Wherever possible the size of the area sampled should be greater than 100cm2
Extraction:
1. Place blood-contaminated fragments of bedding, clothes etc. into a sterile flask with appropriate volume (1: 5 w/v) of extracting solution
2. Shake the flask for 20-40 min, press out.
3. Transfer the liquid phase into a new flask.
Detection of HCV-positive environmental extracts
Obtaining of environmental extracts
Ultracentrifugation
Elution of viral particles from adsorbent
Viral particle adsorption on powder or fiber adsorbents
Eluate
PEG-precipitaion
HCV Detection in PCR
Highly effective virus adsorbent: Highly effective virus adsorbent:
mineral fiber “Fiban”mineral fiber “Fiban”
1818
0 20 40 60 80 100
10
20
30
10
20
30
10
20
30
Adsorbtion efficacy, %
Ads
orbe
nt q
uant
ity,
g
А7
А6
АК22-Э
АК22-В
А5
Material Name
Characteristics
Functional group
Ion typesIon-
exchange behaviour
A-5 fiban
–N=, =NH, –COOH
CompositeCl-, HSO4
-, HCO3
-,
Anionite
A-6 fiban
–N=, –N≡ Carbonate(CO3
2-, HCO3-)
Anionite
AK-22 fiban
–NH2, =NH, –COOH
CompositeCl-, HSO4
-, HCO3
-,
Anionite
Our experimental data showed almost 100% efficacy of enterovirus adsorbtion-elution from water with anion-exchanged mineral fiber “Fiban”
Detection of HCV-positive environmental swabs
Obtaining of environmental swabs with extracting buffer solutions
Ultracentrifugation PEG-precipitaion
HCV Detection in PCR
or
2. Detection algorithm to confirm a link between environmental HCV
contamination and nosocomial infectionDetection of hemoglobin-contaminated environmental samples
Detection of HCV-positive environmental samples
Amplification and sequencing of a part of HCV genome
Phylogenetic reconstruction
Molecular-epidemiology analysis
Detection of HCV-positive samples from patients
Close phylogenetic relationship between RNA sequences from environmental samples and those isolated from patient or health care workers points out at nosocomial HCV transmission.
Assessment of the results
Role of Environmental Contamination in the Risk of Hepatitis C Virus Transmissionin a Hemodialysis Unit
E. Girou, et al. //Clinical Infectious Diseases 2008; 47:627–33
Blood-contaminated surfaces may be a source of HCV cross-transmission in a hemodialysis unit.
Figure. Phylogenetic tree plotted with hypervariable region (HVR) 1sequences from patients known to be infected with HCV and regularly treated in hemodialysis unit and the 5 environment surfaces that tested positive for HCV RNA
ConclusionThere are many issues connected with various aspects of health care setting related HCV infections:
Long incubation period of HCV makes revealing of environmental source of infection extremely difficult or even impossible
Specific approaches to detection of environmental HCV contamination are not developed
no methods currently exist that can reliably determine infectivity and threshold concentration of virus required for transmission
Requires further investigation to develop methods for risk assessment of nosocomial infection based on evidence of infectious properties of HCV.
Republican Research and Practical Center for Epidemiology and
Microbiology, Minsk, Belarus
Laboratory of environment virology
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