Mycobacterium Tuberculosis Agent Information Sheet

Boston University
Research Occupational Health Program (ROHP)
617-358-7647

Agent

Mycobacterium tuberculosis is an acid fast gram positive rods that are non-spore forming, non-motile, slightly curved, aerobic and slow-growing.

Disease/Infection

Latent tuberculosis, pulmonary and extrapulmonary tuberculosis, Potts disease.

Pathogenicity

Approximately 3% to 4% of infected individuals acquire active tuberculosis during the first year after tuberculin conversion, and an additional 5% do so thereafter. Elderly and immunocompromised individuals are at risk factors for progressing to active disease. In patients with active disease, presence of cavitation of CXR, positive AFB smear, invasive, respiratory procedure being performed and presence of cough/not covering cough may impact risk of transmission.

• Special Populations at Risk
  Immunocompromised

Biosafety Information

Risk Group/BSL
Risk Group 3
Biosafety Level 3 Practices

Modes of Transmission
Tuberculosis is transmitted through the air by droplet nuclei inhaled by a susceptible host. Infected particles are propelled from the source by coughing, speaking, singing, and stay in the air until dispersed, diluted, dried, or inhaled by a host. Half-life is 6 hours; therefore, improper ventilation can greatly increase and enhance transmission.

Host Range/Reservoir
Primarily humans, cattle, primates, other animals (rodents).

Symptoms
Similar to M. bovis, the initial infection is usually unnoticed; tuberculin sensitivity appears in a 4-12 weeks. Latent infection may progress to pulmonary tuberculosis (fatigue, fever, cough, chest pain, hemoptysis fibrosis, and cavitation) or extrapulmonary involvement (miliary, meningeal) by lymphohematogenous dissemination. Drug resistant strains can cause irreversible damage in the lungs. 

The general symptoms of TB disease: include feelings of weakness, weight loss, fever, and night sweats. The symptoms of TB disease of the lungs also include coughing, chest pain, and the coughing up of blood. Symptoms of TB disease in other parts of the body depend on the area affected. The wound infection can cause a tuberculoma or a broader systemic infection.

Incubation Period
From infection to primary lesion or significant tuberculin reaction – 4 to 12 weeks; risk of progressive pulmonary or extrapulmonary tuberculosis is greatest within 1 to 2 years after infection; may persist for lifetime as latent infection.

Viability
M. Tuberculosis has greater resistant to disinfectants and requires longer contact times for disinfectants to be effective; 5% phenol, 1% sodium hypochlorite (only if low organic matter and longer contact times), iodine solutions (high concentration of available iodine required), glutaraldehyde and formaldehyde (longer contact time) are effective.

Survival Outside Host
Guinea pig carcasses – 49 days; carpet – up to 70 days; dust – 90 to 120 days; cockroaches – 40 days; manure 45 days; paper book – 105 days; sputum (cool, dark location) – 6 to 8 months; clothing – 45 days.

Information for Lab Workers

Laboratory PPE

Personal protective equipment includes but is not limited to gowns with tight wrists and ties in back, disposable gloves, combination safety glass and mask or a face shield. Facilities for washing and changing clothing after work should be available.  Use of respirators – PAPR or N95.

Containment

Research should be conducted using Biosafety Level 3 practices, equipment, and facility design. Gloves and gowns should be worn when handling infected laboratory animals and when there is the likelihood of direct skin contact with infectious materials. Animal studies may be performed at ABSL-3. BSL-3 practices, containment equipment, and facilities are recommended for activities using clinical materials and diagnostic quantities of infectious cultures. There should be use of a slide-warming tray, rather than a flame for fixation of slides. Liquefaction and concentration of sputa for acid-fast staining may be conducted safely on the open bench by first treating the specimen in a BSC with an equal volume of 5% sodium hypochlorite solution (undiluted household bleach) and waiting 15 minutes before processing. M. tuberculosis complex and for animal studies using experimentally or naturally infected NHP. Animal studies using guinea pigs or mice can be conducted at ABSL-2. BSL-3 practices should include the use of respiratory protection and the implementation of specific procedures and use of specialized equipment to prevent and contain aerosols. Disinfectants proven to be tuberculocidal should be used

In Case of Exposure/Disease

• For injuries in the lab which are major medical emergencies (heart attacks, seizures, etc…):
  • Medical Campus: call or have a coworker call the Control Center at 617-414–4144.
  • Charles River Campus: call or have a coworker call campus security at 617-353-2121.
    You will be referred to or transported to the appropriate health care location by the emergency response team.
• For lab exposures (needle sticks, bite, cut, scratch, splash, etc…) involving animals or infectious agents, or for unexplained symptoms or illness call the ROHP 24/7 hour number (1-617-358-ROHP (7647); or, 8-ROHP (7647) if calling from an on-campus location) to be connected with the BU Research Occupational Health Program (ROHP) medical officer. ROHP will refer you to the appropriate health care location.
• Under any of these scenarios, always inform the physician of your work in the laboratory and the agent(s) that you work with.
• Provide the wallet-size agent ID card to the physician.

Vaccination

Licensed attenuated live vaccine (BCG) is available, but not routinely used in US.

Information for First Responders/Medical Personnel

Public Health Issues

Latent tuberculosis infection is not transmitted person to person without active symptoms. After exposure, patient can be cared for in standard precautions.

Person to person transmission occurs through exposure to patient with pulmonary symptoms and care of these patients should be performed with N95 mask or PAPR. Medical personnel are at risk when performing autopsies, intubation, bronchoscopies or by dermal inoculation procedures. Patients with suspected pulmonary tuberculosis should be placed in airborne isolation.

Diagnosis/Surveillance

Surveillance of latent infection is done with a two annual tuberculin skin test or an interferon gamma release assay (IGRA). In patients with possibility of active disease, diagnosis is made by AFB smear and culture as well as PCR based methods on sputum or tissue in question.

First Aid/Post Exposure Prophylaxis

Perform one of the following actions:

Preventative treatment with INH (risk of hepatitis for those over 35 years old) for 9 months.

Treatment

Combination antibiotic therapy consisting of isoniazid, rifampin, ethambutol, pyrazinamide. Treatment regimen may be adjusted based on culture susceptibility results with the aid of an infectious diseases expert.

Treatment for latent infection includes Rifamycin daily 4 months, or INH + Rifamycin or INH + Rifapentine.

References

Mandell, G. L., J. E. Bennett, et al. (2010). Mandell, Douglas, and Bennett’s Principles and Rractice of Infectious Diseases. Philadelphia, PA, Churchill Livingstone/Elsevier.

http://www.cdc.gov/tb/publications/factsheets/general/tb.htm

NIOSH Emergency Response Safety and Health Database: https://www.cdc.gov/niosh/ershdb/

http://consolidatedsafety.com/

First Aid for the Basic Sciences General Principles by Tao Lee, Kendall; Copyright 2009 the McGraw-Hill Companies.

Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities, 1994; http://www.cdc.gov/mmwr/preview/mmwrhtml/00035909.htm 

Biosafety in Microbiological and Biomedical Laboratories; Deborah E. Wilson, DrPH, CBSP Director Division of Occupational Health and Safety National Institutes of Health Bethesda, Maryland L. Casey Chosewood, M.D. Director Office of Health and Safety Centers for Disease Control and Prevention Atlanta, Georgia; US Government Printing Office, Washington DC. 5^th Edition; 2007

http://www.cdc.gov/tb/topic/basics/default.htm

UpToDate, Treatment of TB infection (latent tuberculosis) in adults, 9/23

Revised: 12/20/23