Tuberculosis Infection Control

Dr AW DreyerClinical Microbiologist

Centre for tuberculosis (incorporating NTBRL)National Institute for Communicable Diseases

South Africa

TB infection control?

A. Protecting myself with a maskB. Isolation of patients who are coughingC. Installing UV lights in patient care areasD. Combination of measures to minimize

the risk of TB transmission within populations

Clinical area

M.tuberculosis - organism

• Cough

Clinical settingCan susceptible M. tuberculosis be classified as a “superbug”?

MTB virulence factors

1. Cell surface components – LAM – immune modulator– Other proteins involved in

cell wall synthesis

2. Secreted factors– Culture filtrate proteins

(CFP) e.g. Esat6/CFP-10– Kinase G – inhibit

phagolysosome maturation

3. Enzymes involved in cellular metabolism (fatty acid and lipid metabolism)

4. Transcriptional regulators e.g. sigma factors

XDR and high mortality in rural KZN

• 221 cases of MDR and 53 cases of XDR• 44 tested for HIV – all co-infected• 52/53 patients died• Median survival of 16 days from time of

diagnosis• Genotyping confirmed similar strains

Ghandi NR et al. Extensively drug-resistant tuberculosis as a cause of death in patients co-infected with tuberculosis and HIV in a rural area of South Africa. Lancet 2006:4(368)

Transmission

• Via droplet nuclei (<5um) and contains 1 - 5 bacilli (coughing 3000, sneezing 1 million, aerosolizing procedures >>>)

• Can survive (remain airborne) on currents for 4 – 8 hours

• 1 bacillus needed to establish infection

Picture

Compensatory mutations associated with ongoing transmission

• Investigated the epidemiological relevance of compensatory mutations outside rpoB

• Analyzed 286 drug-resistant and 54 drug-susceptible clinical M. tuberculosis isolates from the Western Cape, South Africa (high MDR setting)

• Sequencing of a portion of the rpoA-rpoC interaction region of the rpoC gene revealed that 23.5% of all rifampin-resistant isolates tested carried a non-synonymous mutation

• These compensatory mutations in rpoC were associated with transmission• 30.8% in the RFLP cluster, 9.4% with unique patterns (P < 0.01)

• Their study supports a role for rpoC mutations in the transmission of multidrug-resistant tuberculosis and that different strain genetic backgrounds might influence compensatory evolution in drug-resistant M. tuberculosisDe Vos M et al. Putative compensatory mutations in the rpoC gene of rifampicin-resistant Mycobacterium

tuberculosis are associated with ongoing transmission. Antimicrob Agents Chemother 2013 Feb; 57(2) :827-32

M.tuberculosis – burden of disease

• 2012: 8.6 million new cases (450 000 MDR), 1.2 million associated deaths (170 000 MDR deaths)

TB burden?

South Africa is different than the rest of the world

Who is at risk?

Community

Healthcare workers

Laboratories

Corner stone of TBICEarly, rapid diagnosis and appropriate management

National responsibilities

1. Strengthen the co-ordinating body– National policy– Planning and budgeting– Human resource development and training

2. Facility design (construction and renovation)– High risk areas (TB and medical wards, emergency rooms,

waiting areas, sputum collection areas)

3. Healthcare worker (HCW) surveillance4. Advocacy, communication and social mobilization (ACSM)5. Establish a system for monitoring and evaluation6. Operational research

Healthcare facilities

Facility level measures

• Management– IPC committee, facility plan and budget etc– Rethink space (renovation or new construction) to

implement controls– Onsite HCW surveillance and assessment– ACSM– Monitor IPC measures– Participate in research

Administrative controls

• Triage – identify people with TB symptoms• Separate infectious patients• Control the spread (promote cough etiquette)• Minimize time spent in healthcare• HCW: Access to HIV testing, ART and IPT

Environmental controls

• Use ventilations systems• Use ultra violet germicidal irradiation (UVGI)

fixtures

Ventilation

• Ventilation is the movement of air in a building and replacement of inside air with air from the outside.

• Two general types– Natural ventilation (which relies on open doors and

windows to bring in air from the outside). Fans may also assist in this process and distribute the air.

– Mechanical ventilation (which usually refers to the use of air-moving equipment that circulates air in a building and may also involve heating and/or cooling. (HVAC)

Natural ventilation

Tuberculosis Infection Control, Francis J Curry National Tuberculosis Centre

Mechanical ventilation

Tuberculosis Infection Control, Francis J Curry National Tuberculosis Centre

UVGI

• Shown to kill or inactivate M. tuberculosis• Used to supplement ventilation• Short term health effects on skin and eyes• 2 applications:– In-duct UVGI– Upper-air UVGI

In-duct UVGI

Upper-air UVGI

Effectiveness of UVGI

• Mounted high on walls or suspended from ceiling• Metal baffles to direct radiation• Safety: Positioned not to reflect from the ceiling• Measurements of exposure must be performed during

installation in all areas where staff or patients could be exposed

• Recommended exposure limit (REL): – 0.2 microwatt per square centimet for a maximum of 8

hours• Fixtures must be cleaned• Lamp must be monitored and replaced if necessary

Personal protective equipment

• Use particulate respirators• Specific indications:– During high risk aerosol generating procedures

e.g. bronchoscopy, intubation, sputum induction– Care for MDR/XDR patients

Study

Community

Guidelines for households

• Close contact is a major risk factor• TB contact investigation• Behavioral campaigns• Households:– Adequately ventilated– Adhere to cough etiquette and respiratory hygiene– Smear positive (spend a s much time outdoors,

separate room and avoid congregate settings or public transport)

– Access to HIV testing

Laboratory biosafety

Risk assessment

• “…is an approach that promotes the consideration of risk and the development of appropriate biosafety practices in laboratories based on the unique combination of test procedures, staff expertise and facilities present in each laboratory…” WHO 2013

EquipmentPractices/

procedures

Risk group (1 – 4)

Biosafety level (1 – 4)

Facillity design

• MTB is generally regarded as Risk group 3• Is this really true?• What about MDR-TB,XDR-TB and TDR-TB?

– No preventative measures– Limited therapeutic options– High community risk

What is new? • No longer to establish a specific risk group

• Now – consider the type of activities/procedures performed at the individual laboratory

• Establish Low, Moderate and High risk

• Big improvement towards preventing laboratory associated infections with MTB

• Xpert MTB/Rif assay using the GXP instrument

• Any comments with regard to risk assessment?

Classification of TB laboratories

Skill and expertise

• Level of skill can directly influence the biosafety level designation

• E.g. newly employed technician working with a risk group 3 organism may require BSL-4 environment (vica versa)

• Biggest form of protection is knowledge and the ability to perform a risk assessment for your own working environment

New TB testing algorithm in SA

• Use Xpert MTB/Rif assay as firstline testing on all suspected patients (sputum)

• If Rif is R, follow-up sample for TB MCS• Our culture facilities are now “bombarded” with

potential drug resistant samples• Limpopo: Limited space, MGITs in the same room as

general bacteriology• Did we anticipate this and are we informing our

staff of the potential added risks?

• MTB culture laboratory• Following BSL-3 recommendations (TB

containment lab)

N95 respirator fit testing

• Different types of masks!• Different sizes!

Recommendations for laboratories

• Ongoing risk assessment and training of staff• Aim to maintain BSL-3 practices and

equipment with BSL-2 facility design• Ensure that BSCs are well maintained and

tested daily• Use N95 respirators but ensure fit testing and

availability• Ongoing health education and screening,

encourage staff to know there HIV status

Conclusion

• Tuberculosis infection control applies to both healthcare and community settings

• Efforts should be focused at improving case detection and initiating appropriate management to decrease the overall risk

• Laboratory workers are at increased risk, all specimens should be treated as potentially infectious

• National efforts towards strengthening TBIC should be prioritized

Thank you