TB Infection Control: Principles, Pitfalls, and Priorities - PowerPoint PPT Presentation

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TB Infection Control: Principles, Pitfalls, and Priorities

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To review the recent history of TB Infection Control. ... HCW Deaths due to. Nosocomial Transmission of DR-TB. MDR outbreaks U.S. 1980s-1990s ... – PowerPoint PPT presentation

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Title: TB Infection Control: Principles, Pitfalls, and Priorities


1
TB Infection ControlPrinciples, Pitfalls, and
Priorities
  • Kevin P. Fennelly, MD, MPH
  • Interim Director
  • Division of Pulmonary Critical Care Medicine
  • Center for Emerging Re-emerging Pathogens
  • UMDNJ-New Jersey Medical School
  • fennelkp_at_umdnj.edu

2
Objectives
  • To review basic principles underlying TB
    transmission and TB Infection Control policies.
  • To review the recent history of TB Infection
    Control.
  • 3. To discuss personal observations and offer
    practical solutions to common problems in TB
    Infection Control.

3
Is TB an Occupational Disease of HCWs?
Low- middle-income countries High-income countries
LTBI (prevalence) 63 (33-79) 24 (4-46)
TB disease (annual incidence) 5.8 (0-11) 1.1 (0.2-12)
TB mortality (inpt) (PMR) (outpt) ?? 1.18 (1.04-1.35) 3.04 (1.62-5.19)
- Menzies D et al. IJTLD 2007 11593
4
HCW Deaths due to Nosocomial Transmission of
DR-TB
  • MDR outbreaks U.S. 1980s-1990s
  • 9 HCWs died
  • All immunocompromised, 8 with HIV
  • Sepkowitz KA, EID 2005
  • XDR-TB outbreak, So Africa, 2006
  • 52/53 died of unrecognized XDR-TB
  • 44/44 tested were HIV
  • Median survival from sputa collection16 days
  • 2 HCWs died 4 others sought care elsewhere
  • Gandhi N, Lancet 2006

5
Personal Respiratory Protection Against M.
tuberculosis Contentious Controversy
6
from Sol Permutt, 2004
7
Wells-Riley Equation Mathematical model of
airborne infection
PrinfectionC/S1-e(-Iqpt/Q) Where C S
infected S susceptibles exposed I infectors
( active pulm TB cases) q infectious units
produced/hr/Infector p pulm ventilation
rate/hr/S t hours of exposure Q room
ventilation rate with fresh air
8
Control Measures are Synergistic Complementary
Assumptions Homogenous distribution of
infectious aerosol over 10 hours uniform
susceptibility.
- Fennelly KP Nardell EA. Infect Control Hosp
Epidemiol 1998 19754
9
Wells-Riley Mathematical Model of Airborne
Infection
10
TB is Spread by Aerosols, NOT sputum
11
Particle size suspension in air( NOT size of
bacilli)
  • Particle size deposition site
  • 100 ?
  • 20 ?
  • 10 ? upper airway
  • 1 - 5 ? alveolar deposition
  • Time to fall the height of a room
  • 10 sec
  • 4 min
  • 17 min
  • Suspended indefinitely by room air currents

- Courtesy of Sol Permutt, 2004
12
Six-stage Andersen cascade impactor
Andersen AA. J Bacteriol 195876471.
13
Cough Aerosol Sampling System
- Fennelly KP et al. Am J Resp Crit Care Med
2004 169 604-9
14
Cough-generated aerosols of MtbInitial Report
from Denver, CO4 of 16 (25) of SS subjects
- Fennelly KP et al. Am J Resp Crit Care Med
2004 169 604-9
15
Variability of Infectiousness in TBEpidemiology
  • Rotterdam, 1967-69 Only 28 of smear positive
    patients transmitted infections.
  • Van Geuns et al. Bull Int Union Tuberc 1975
    50107
  • Case control study 796 U.S. TB cases
  • Index cases tended to infect most (or all) or few
    (or none) of their contacts
  • Snider DE et al. Am Rev Respir Dis 1985 132125
  • Ability to publish outbreaks suggests that they
    are episodic.

16
Variability of Infectiousness in TB
Experimental
  • All infections attributed to 8 of 61 (13)
    patients. 50 of infections due to one
    patient with TB laryngitis.
  • Riley RL et al. Am Rev Respir Dis 1962 85511.
  • 3 (4) of 77 patients produced gt 73 of the
    infections in the guinea pigs.
  • Sultan L. Am Rev Respir Dis 1967 95435.
  • Recent replication of this model in Peru
  • 118 hospital admissions of 97 HIV-TB coinfected
    patients
  • 8.5 caused 98 of secondary GP infections
  • 90 due to inadequately treated MDR-TB
  • Escombe AR et al. PLoS Medicine 2008 5e188

17
Occupational TB in Sub-Saharan Africa
  • Malawi
  • 25 mortality
  • Harries AD, Tran R Soc Trop Med Hyg 1999 93 32
  • Ethiopia
  • South Africa
  • Nigeria
  • 32 of 2,173 HCWs
  • 15 (47) as HIV-TB
  • Salami AK, Nigerian J Clin Prac 2008 11 32

18
What is the magnitude and variability of
infectious aerosols of M. tuberculosis?(Can we
better identify the most infectious?)
Hypothesis 1 Cough-generated aerosols of Mtb
can be measured in resource-limited
settings. Hypothesis 2 Cough-generated aerosols
will be detected in approximately 25-30 of
patients with PTB.
19
Cough Aerosol Sampling Systemv.2
20
Frequency Distribution of Cough-generated
Aerosols of M. tuberculosis and Relation to
Sputum Smear Status31/112 (28) SS subjects
21
Cough-generated Aerosols of M.
tuberculosisNormalized Particle Sizes
Lower limit of size range(µ) 7.0 4.7 3.3
2.1 1.1 0.65 Anatomical deposition
Upper airway -- bronchi -- alveoli
Abstract, ATS International Conference, 2004.
22
Pitfalls in Administrative Controls
  • TB Mortality not prioritized or under
    surveillance (i.e., no data collection)
  • HIV screening of HCWs not prioritized
  • major risk factor for TB disease death
  • HAART now feasible in much of world
  • HIV screening advocated for admt patients in US
  • TB laboratory personnel often not involved in TB
    infection control efforts
  • Botswana 1st AFB smear STAT
  • Decisions re infectiousness falls onto
    clinicians with variable expertise

23
Pitfalls in Environmental Controls
  • Little or no engineering expertise and support
    for hospitals HCFs
  • No systems of communication / interaction
  • Different cultures and mind-sets
  • TB nurses or administrators subject to sales
    pitches from commercial vendors
  • UVGI lamps in SANTA facilities
  • Mobile air filters in Newark, NJ
  • Lack of appreciation of natural ventilationand
    its limitations!
  • Low rate of nosocomial infection in Uganda
    project
  • High rate in Tugela Ferry

24
Pitfalls in Personal Respiratory Protection
  • Too much attention paid to masks at expense of
    administrative and environmental measures
  • Rizdon R et al Renal unit with poor ventilation
  • Inappropriate use on patients
  • Focus on fit-testing and regulation rather than
    on follow up on use in field
  • Lack of appreciation that not all respirators
    provide the same level of protection
  • Need for more protection in high-risk
    aerosol-inducing procedures, e.g., bronchoscopies

25
TB-IC Practices for Community Programs
  • Best administrative control
  • Suspect and separate until diagnosed
  • Surveillance of HCWs with TST (and/or IGRAs) and
    rapid treatment of LTBI if conversions occur
  • Best environmental control Ventilation
  • Do as much as possible outdoors
  • Use directional airflow when possible
  • Natural breeze or fans HCW upwind patient
    downwind
  • Personal respiratory protection
  • N95 respirators when indoors or very close
    (procedures)
  • Surgical masks on patients to control source

26
Summary TB-IC
  • Administrative controls most important component
    of TB-IC
  • Suspect and separate!
  • Prioritize screening HIV in HCWs
  • Prioritize good ventilation in all areas
  • Back-up in areas with poor ventilation
  • Fans, mechanical ventilation, UVGI
  • Prioritize personal respiratory protection for
    high risk settings, esp where admin and environ
    controls limited
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