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Table of Contents:
Taxonomy Information
  1. Species:
    1. Mycobacteria tuberculosis (Website 1):
      1. Common Name: TB
      2. GenBank Taxonomy No.: 1773
      3. Description: The Mycobacterium tuberculosis belongs to the genus Mycobacterium, which are aerobic, nonmotile, and rod-shaped bacteria with two distinguishing characteristics: acid-fastness and slow growth(Grange, 1998a). Mycobacterium tuberculosis is one of most successful pathogens of mankind, infecting one-third of the global population and claiming two million lives every year. The ability of the bacteria to persist in the form of a long-term asymptomatic infection, referred to as latent tuberculosis, is central to the biology of the disease(Stewart et al., 2003). Approximately eight million people develop active tuberculosis (TB) every year, with two million dying from the disease. In addition to this already huge burden of disease, it is estimated that up to two billion people have been infected with the causative agent, Mycobacterium tuberculosis. Most people control the initial infection by mounting a cell-mediated immune response that prevents disease but can leave a residual population of viable mycobacteria. Between 5 - 10% of individuals who become infected subsequently develop clinical disease. Primary TB develops within 1 or 2 years after an initial infection and, particularly in children, is often associated with disseminated disease. Post-primary TB develops later in life, and can be caused either by reactivation of bacteria remaining from the initial infection or by failure to control a subsequent reinfection. Post-primary TB is predominantly a pulmonary disease, involving extensive damage to the lungs and efficient aerosol transmission of bacteria. The risk of disease is highly dependent on the immune status of the host; coinfection with HIV markedly increases the incidence of both forms of disease(Stewart et al., 2003).
      4. Variant(s):
        • Mycobacterium tuberculosis H37Rv (Website 2):
          • Common Name: TB H37RV
          • GenBank Taxonomy No.: 83332
          • Parents: Mycobacteria tuberculosis
          • Description: Mycobacterium tuberculosis H37Rv was first isolated in 1905, has remained pathogenic and is the most widely used strain in tuberculosis research(Camus et al., 2002).
        • Mycobacterium tuberculosis CDC1551 (Website 3):
          • Common Name: TB CDC1551
          • GenBank Taxonomy No.: 83331
          • Parents: Mycobacteria tuberculosis
          • Description: CDC 1551 is a recent clinical isolate which was responsible for an outbreak of TB in a rural area of the USA in 1995. Due to the high rate of skin-test conversion that occurred and the large skin-test response to purified protein derivative of tuberculin (PPD) of those infected, CDC 1551 was considered to be unusually infectious in man. In addition, evaluation of the growth of CDC 1551 in lungs of mice 20 d after aerosol infection gave 100-fold higher numbers of bacilli compared to the numbers of bacilli isolated from the lungs of mice infected with the M. tuberculosis laboratory strain Erdman. As a result of these findings, CDC 1551 was assumed to be highly virulent and was selected for sequencing by the National Institutes of Health(Betts et al., 2000).
        • Mycobacterium tuberculosis 210 (Website 4):
          • Common Name: TB 210
          • GenBank Taxonomy No.: 164513
          • Parents: Mycobacteria tuberculosis
          • Description: A widely distributed strain, designated 210. The strain was characterized by a 21-band fingerprint pattern when probed with IS6110. Currently, the 210 strain has been shown to account for 215 cases of tuberculosis in five states. To determine whether the dissemination of this strain correlated with its capacity for replication, the intracellular growth rate of strain 210 in human macrophages was measured. Compared to isolates from other clusters or from non-clustered patients, strain 210 grew significantly faster. The data indicate that the 210 strain should also be considered a W variant(Beggs et al., 2000).
        • Mycobacterium tuberculosis subsp. tuberculosis (Website 5):
          • Common Name: TB tb
          • GenBank Taxonomy No.: 182785
          • Parents: Mycobacteria tuberculosis
          • Description: The Mycobacterium tuberculosis complex consists of a highly related group of acid-alcohol-fast bacilli which are human and animal pathogens. It comprises five classical species. M. tuberculosis (sensu stricto) infects human and non-human primates. Several authors have stated that members of the complex should be grouped as varieties or subspecies of M. tuberculosis and that the division of the tuberculosis complex into five species is an artifact of the great historical interest in this pathogen. However, to our knowledge, the reclassification of these species as a single species has not been proposed formally. Their significance in human and veterinary medicine, and the differences in their epidemiology, pathology and antibiotic response mean that the former classification is a useful one(Aranaz et al., 1999).
Lifecycle Information
    1. Stage Information:
      1. Bacilli:
        • Size: 0.3-0.6 to 1-4 um
        • Shape: Rods, straight or slightly curved, occurring singly or in occasional threads.
        • Picture(s):
        • Description: In natural circumstances, M. tuberculosis, the causative agent of TB, is transmitted by expulsion of nasal droplets from an infected human individual to an uninfected one. Nasal droplets, which contain tubercle bacilli and are no larger than 2 um in diameter, are able to penetrate to the alveoli of the respiratory tract of the uninfected individual. Alveolar macrophages, which sample the alveolar mucosa for foreign organisms, ingest the M. tuberculosis bacilli and enclose them in phagosomes. If these macrophages are activated, the mycobacteria containing phagosomes fuse with lysosomes, and the bacteria are killed. If, on the other hand, the alveolar macrophages are not activated, the bacilli survive and grow within the phagosomes by altering these intracellular compartments in some way to preclude normal maturation to phagolysosomes or to prevent fusions of the phagosomes to lysosomes. The bacilli multiply within the phagosomes until the macrophages lyse, probably because of bacillary burden, and the mycobacteria are released into the surrounding lung tissue, where they are phagocytized by tissue macrophages. Again, if the macrophages are activated, the bacteria are killed. However, if these tissue macrophages are not activated, the mycobacteria continue to multiply within the phagosomes and, upon release, are phagocytized by additional tissue macrophages(Clark-Curtiss and Haydel, 2003).
Genome Summary
  1. Genome of Mycobacteria tuberculosis
    1. Mycobacterium tuberculosis(Website 8)
      1. GenBank Accession Number: NC_000962,NC_002755
      2. Size: 4411532 bp(Camus et al., 2002). 4403837 bp(Website 6).
      3. Gene Count: 4056(Camus et al., 2002).
      4. Description: The original sequence and annotation of Mycobacterium tuberculosis strain H37Rv identified 3974 genes (Cole et al., 1998). This included 3924 genes thought to encode proteins and 50 encoding stable RNA. Following the re-annotation, we have included 82 additional genes. All of the new genes are believed to encode polypeptides and no change has been detected in the number of RNA molecules(Camus et al., 2002). The current nucleotide sequence now contains 4411532 nt(Camus et al., 2002).
      5. Picture(s):
Biosafety Information
  1. Biosafety information for Mycobacteria tuberculosis
    1. Level: 2 and 3(CDC - Guidelines for safely working with M. tb).
    2. Precautions: Prevention of aerosols -- In most cases, the "laboratory accident" that results in an exposure and thus a tuberculin skin-test conversion is not as overt as the breakage of a bottle; more often, lapses in technique allow droplet nuclei to be released from culture-amplified materials. Therefore, all laboratory equipment and procedures should be evaluated when put into use and periodically thereafter to ensure that opportunities for generation of aerosols are minimized. Spill avoidance -- A spill can occur at any time during the processing of specimens. If a culture containing M. tuberculosis complex, whether in liquid or on solid medium, is dropped and broken, an aerosol is generated. Laboratory personnel should avoid practices that can result in spills (e.g., hand-carrying tubes, vials, and bottles, or improperly stacking racks or baskets). All tubes, plates, and other containers should be transported on carts in protected racks or baskets(CDC - Guidelines for safely working with M. tb).
    3. Disposal: When a spill occurs, all persons should leave the room immediately so that an assessment of the spill and exposure can be made without further personnel exposure. Two hours or more later, depending on the number of air changes in the laboratory, the degree of convectional mixing in the room air and the turbulence resulting from furniture and equipment placement, a person wearing a HEPA or N100 respirator (National Institute for Occupational Safety and Health, Occupational Safety and Health Administration) and protective clothing should reenter the room to cover the spill with towels soaked with a tuberculocidal disinfectant. After soaking for at least 2 hours, the spill should be cleaned up by a person wearing a respirator and protective clothing. When more intensive aerosolization of culture-amplified fluids occurs, the room should be sealed and decontaminated with formaldehyde gas(CDC - Guidelines for safely working with M. tb).
Culturing Information
  1. Solid Media (Woods, 2002):
    1. Description: Conventional culture of mycobacteria with solid media (egg-based, such as Lowenstein-Jensen or agar such as Middlebrook 7H11) requires incubation for 3 to 6 weeks and sometimes longer before there is sufficient growth for identification testing. Additionally, in most studies, solid media are less sensitive than liquid media for growth of mycobacteria, but neither type of medium recovers all isolates. Therefore, use of solid media alone for recovery of mycobacteria from clinical specimens not only delays diagnosis but also could potentially result in missed diagnoses. For these reasons, the 1993 CDC recommendations indicate that a broth system be used for primary mycobacterial culture and that a solid medium also be inoculated(Woods, 2002).
    2. Medium: Lowenstein-Jensen(American Thoracic Society, 2000). Middlebrook 7H10(American Thoracic Society, 2000). Middlebrook 7H11(American Thoracic Society, 2000).
    3. Optimal Temperature: 37C(Wayne et al., 1984).
    4. Lower Temperature: 30-34C(Wayne et al., 1984).
    5. Optimal pH: 6.8(Heifets and Sanchez , 2000).
    6. Upper pH: 7.0(Wayne et al., 1984).
    7. Lower pH: 6.4(Wayne et al., 1984).
    8. Doubling Time: 14-15 hours(Wayne et al., 1984).
    9. Picture(s):
  2. Liquid broth (Woods, 2002):
    1. Description: Broth-based culture systems typically user 7H-12 liquid medium and are much more rapid in providing results. When combined with DNA probes for rapid species identification, are capable of producing positive results in 2 weeks or less for the vast majority of sputum smear-positive specimens, and within 3 weeks for smear-negative specimens(Schluger et al., 2003).
    2. Medium: Middlebrook 7H12(Woods, 2002). Middlebrook 7H9(Woods, 2002). Kirchner(Woods, 2002).
  3. BACTEC 460TB (Siddiqi et al., 1981):
    1. Description: For many years, the only culture system with the potential to meet the CDC target for growth and detection of mycobacteria was the semi-automated radiometric BACTEC 460 TB (BD Biosciences, Spars, MD), which not only decreases time to detection of growth but also increases rate of recovery, compared with solid media. This system, however , is labor-intensive, and because the broth medium contains C14, laboratories must comply with the various safety and regulatory issues associated with the use of radioisotopes. Additionally, cross-contamination of battles by the instrument is a potential problem(Woods, 2002).
    2. Medium: Middlebrook 7H12(Siddiqi et al., 1981).
    3. Optimal Temperature: 37C(Siddiqi et al., 1981).
    4. Upper Temperature: 38C(Siddiqi et al., 1981).
    5. Picture(s):
      • BD BACTEC 460TB Automated Mycobacterial Detection and Susceptibility Testing System (Becton, Dickinson and Company)



        Description: The BACTEC 460TB was the first automated system for mycobacteria testing. Today, the BACTEC 460TB System still serves as the benchmark of quality and reliability for laboratories that require detection, differentiation and susceptibility from a single instrument. Used with permission of Becton, Dickinson and Company(Becton, Dickinson and Company).
  4. MB/BacT (Manterola et al., 1998):
    1. Description: The MB/BacT system (MB/BacT; Organon Teknika, USA) is a fully automated, rapid, nonradiometric system for the culture of mycobacteria from clinical specimens other than blood. The MB/BacT system employs a colorimetric sensor and reflected light to monitor the presence and production of carbon dioxide (CO2) dissolved in the culture medium. If mycobacteria are present in the test sample, CO2 is produced as the organisms metabolize the substrates in the culture medium. When growth of the microorganisms produces CO2, the color of the gas-permeable sensor at the bottom of each culture bottle changes from dark green to bright yellow. The lighter color results in an increase of reflectance units monitored by the system(Manterola et al., 1998).
    2. Medium: The MB/BacT system consists of a bottle containing basic broth (Middlebrook 7H9; Organon Teknika), casein, bovine serum albumin, and catalase. Bottles contain 10 ml of media and are prepared with an atmosphere of CO2 in oxygen under vacuum. They are designed for use with the MB/BacT antibiotic supplement (amphotericin B 0.018% w/v, azlocillin 0.0034% w/v, nalidixic acid 0.04% w/v, polymyxin B 10000 U, and trimethoprim 0.0105% w/v)(Manterola et al., 1998).
    3. Optimal Temperature: 37C(Manterola et al., 1998).
  5. ESP II system (Woods et al., 1997):
    1. Description: The ESP Culture System II (ESP II; Difco Laboratories, Detroit, Mich.) is a fully automated, continuously monitoring system for growth and detection of microorganisms, including mycobacteria, that has recently received clearance by the Food and Drug Administration for mycobacterial culture. ESP II is an adaptation of the ESP blood culture system that has been available for clinical use for over 3 years. The technology is based on detection of pressure changes within the headspace above the broth culture medium in a sealed bottle, i.e., either gas production or gas consumption due to microbial growth. A special detection algorithm has been developed for the very slowly growing mycobacteria, in addition to the current ESP detection algorithm(Woods et al., 1997).
    2. Medium: Difco ESP II bottle, with antibiotic supplement (polymyxin B, vancomycin, nalidixicacid, and amphotericin B [PVNA]) and a growth supplement (Middlebrook OADC enrichment)(Woods et al., 1997).
    3. Optimal Temperature: 35C(Woods et al., 1997).
    4. Picture(s):
      • ESP Culture System II (TREK Diagnostic Systems)



        Description: ESP is the first fully automated culture system FDA-cleared for routine blood culture, mycobacteria detection, and M. tuberculosis susceptibility testing on a single instrument platform(TREK Diagnostic Systems).
  6. BACTEC 9000MB (Zanetti et al., 1997):
    1. Description: A new, fully automated, nonradiometric method, fluorescent BACTEC 9000 MB (Becton Dickinson), which uses an oxygen-quenched fluorescence indicator for the rapid detection of Mycobacterium spp., has been introduced. The fluorescence of the sensor is a function of the oxygen depletion that results during microbial metabolism. The presence of fluorescence indicates growth of microorganisms(Zanetti et al., 1997).
    2. Medium: The medium used in BACTEC 9000 MB is a modified Middlebrook broth formulation (Myco/F sputa; Becton Dickinson Microbiology Systems, Sparks, Md.). Each Myco/F vial was supplemented with 2 ml of supplement F enrichment (lactic acid [3.5 mg/ml], polyoxyethylene stearate [2.3 mg/ml], bovine serum albumin [116.0 mg/ml], dextrose [23.0 mg/ml], biotin [0.012 mg/ml] [Becton Dickinson]) and with an antimicrobial mixture of PANTA (polymyxin B [1,000 U/ml], amphotericin B [100 mg/ml], nalidixic acid [400 mg/ml], trimethoprim [100 mg/ml], azlocillin [200 mg/ml] [Becton Dickinson])(Zanetti et al., 1997).
    3. Optimal Temperature: 37C(Zanetti et al., 1997).
    4. Picture(s):
  7. BACTEC MGIT 960 (Hanna et al., 1999):
    1. Description: The BACTEC MGIT 960 system is a fully automated, high capacity, nonradiometric, noninvasive instrument which requires neither needles nor other sharp implements to simultaneously incubate and monitor 960 7-ml culture tubes. To monitor microbial growth, the BACTEC MGIT 960 uses the same oxygen-quenching fluorescent sensor technology as both the manual Mycobacteria Growth Indicator Tube (BBL MGIT) and the BACTEC 9000MB system, in conjunction with unique on-board algorithms to determine the positivity of the culture tubes(Hanna et al., 1999).
    2. Medium: Middlebrook 7H9 broth base, to which was added an enrichment supplement containing oleic acid, albumin, dextrose, and catalase (BBL MGIT OADC) and an antibiotic mixture of polymyxin B, amphotericin B, nalidixic acid, trimethoprim, and azlocillin (BBL MGIT PANTA)(Hanna et al., 1999).
    3. Optimal Temperature: 37C(Hanna et al., 1999).
    4. Picture(s):
      • BD BACTEC MGIT 960 System for Mycobacteria Testing (Becton, Dickinson and Company)



        Description: The BACTEC MGIT 960 System builds on the legacy of simplicity, efficiency, performance and safety of the BACTEC 460TB and 9000MB instruments. Used with permission of Becton, Dickinson and Company(Becton, Dickinson and Company).
Epidemiology Information:
  1. Outbreak Locations:
    1. Tuberculosis in Africa has reached epidemic proportions, with an estimated 2 million new cases occurring annually, increasing at a rate of 10% each year, largely as a result of HIV co-infection. Consequently, the numbers of TB cases in Africa are projected to double in the next decade because of the HIV epidemic and under-funding of effective strategies against TB. TB is the world's leading killer among infectious diseases, with one person dying of it every 15 s across the globe. In Africa, it is responsible for 600 000 deaths each year, mainly occurring among the young and economically productive age group. The situation is compounded by the fact that on average, 30-40% of the TB cases in Africa are HIV positive, this figure reaching 70% in some countries. On a global level, 80% of the 8 million TB cases occurring annually are in only 22 countries. Of the 10 countries with the highest incidence, nine are in Africa. Africa bears the additional burden of high levels of poverty and some of the lowest health indicators in the world. Natural calamities and man-made conflicts have worsened the situation in many countries, resulting in a large number of displaced persons. In addition, the AIDS epidemic has caused a reversal of the gains in development and has resulted in a decline in life expectancy in many countries(Mwinga and Fourie, 2004).
    2. The incidence of tuberculosis (TB) in Latvia, as in the rest of the world, has followed the same increasing trend. From 1991 to 1998, the incidence of TB in Latvia increased, reaching a rate of 74 per 100,000 inhabitants. Since then, it has remained at about this level. At the same time, drug resistance among TB patients in Latvia seems to be the highest in the world, with primary multidrug resistance found in 8.6% of new cases and in 34.5% of all TB patients in the year 2000(Tracevska et al., 2002).
    3. Tuberculosis is an emerging problem in penitentiary systems all over the world. Russia is not an exception; it has an enormous prison system with nearly 1 million inmates (0.7% of the current population). The high number of imprisoned persons, overcrowded conditions, inadequate ventilation, and poor general health of inmates facilitate the spread of tuberculosis. In 2000, the incidence and mortality associated with tuberculosis in Russian prisons were 3174 cases and 171 deaths per 100,000 prisoners, respectively. The situation becomes worse if the disease is caused by drug-resistant Mycobacterium tuberculosis isolates. In prisons in some regions of Russia, the prevalence of resistance to 1 drug among new cases was 35% to 44%, and the prevalence of multidrug resistance (MDR; i.e., resistance to at least rifampin and isoniazid) among new cases varied from 15% to 22%(Toungoussova et al., 2003). In the Archangel prison, Russia, isolates recovered from 34.0% and 55.0% of prisoners with new and previously treated cases of tuberculosis, respectively, had MDR. Comparison of the situation with that in the community revealed that MDR among new cases was 2.5 times higher in the prison settings; the rates of MDR among previously treated cases in the prison (55.0%) and the community (60.0%) were similar. The high rate of MDR and the identical RFLP patterns, spoligotypes, and rpoB mutations among new cases indicate active transmission of isolates with MDR between prisoners(Toungoussova et al., 2003). Patients with infectious tuberculosis who are imprisoned and those who are released from prison before treatment completion may play an important role in the disease epidemiology. Close coordination of tuberculosis programs in the prison and the community is important(Toungoussova et al., 2003).
    4. Strains of the Beijing/W genotype family of Mycobacterium tuberculosis have caused large outbreaks of tuberculosis, sometimes involving multidrug resistance. This genetically highly conserved family of M. tuberculosis strains predominates in some geographic areas(Glynn et al., 2002). Beijing strains were most prevalent in Asia but were found worldwide. Associations with drug resistance varied: in New York, Cuba, Estonia, and Vietnam, Beijing strains were strongly associated with drug resistance, but elsewhere the association was weak or absent. Although few reports have measured trends in prevalence, the ubiquity of the Beijing strains and their frequent association with outbreaks and drug resistance underline their importance(Glynn et al., 2002).
    5. Trend analysis has also confirmed that MDR-TB is not a major problem in countries implementing tuberculosis control according to international guidelines for several years. Botswana, Chile, Cuba, the Czech Republic, and Uruguay have all showed very low prevalence of MDR-TB confirming that efficient tuberculosis control prevents the outset and spread of MDR-TB throughout the years. Likewise, in developed countries with long history of tuberculosis control such as Australia, Canada, Denmark, France, the Netherlands, the United States, and the United Kingdom trends suggest that MDR-TB is not a major public health issue but problem limited to specific groups including immigrants, refugees, and homeless(Espinal et al., 2003).
    6. This outbreak demonstrates that tuberculosis can spread in a neighborhood bar if one of the regular patrons is highly infectious. The index patient had a progressively worsening cough, and over a period of six months his weight declined from 80 to 49 kg. There was no intervention, however, even though he was eligible for health care under government programs. There was a public clinic within six blocks of the bar and a public hospital within three miles, yet he did not seek health care, nor did any of the bars employees or customers intervene. Instead, the patient went untreated until he could barely stand unassisted, had extensive destruction of lung tissue, and had infected numerous others. His alcoholism and mental health problems were a highly effective barrier to health care. Though it would have been difficult, early intervention would probably have reduced the extent of the outbreak. The index patient proved highly infectious. Forty-one of 97 contacts (42 percent) interviewed at the bar were infected. Active tuberculosis developed in 14 of 97 (14 percent). These numbers are higher than expected. In a typical contact investigation, approximately 20 to 30 percent of the close contacts have positive tuberculin skin tests and in only 1 or 2 percent does active tuberculosis develop. Also higher than expected was the proportion of the people we surveyed who were infected but without disease initially (i.e., they had positive tuberculin skin tests, normal chest films, and no symptoms), yet who later progressed to active disease. Nineteen such people were offered isoniazid prophylaxis. Six completed therapy and remained well, but 13 refused preventive therapy or were noncompliant. In 3 of these 13 (23 percent), active tuberculosis developed within two years. Typically, in approximately 5 percent of the people who convert to positive tuberculin skin tests, active tuberculosis develops in one year, and in an additional 5 percent it develops at some time during their lives(Kline et al., 1995).
    7. There is great potential for extensive transmission of TB in a high school setting by an adolescent index patient. Schools are the most common site reported for community-based outbreaks. Contributing factorsinclude delay in diagnosis, sustained contact, and inadequate ventilation or overcrowding(Phillips et al., 2004). In May 2001, a case of highly infectious TB was diagnosed in a 15-year-old high school student in rural Missouri(Phillips et al., 2004). The transmission of TB followed a predictable pattern at the high school. Students with the most exposure, those in <=3 classes with the patient, were most at risk (Relative Risk: 5.7)(Phillips et al., 2004). Of the 5 household contacts, all were infected and 3 (60%) had developed active TB disease. Of the 781 high school students sought for TB screening, 559 (72%) completed testing, and 58 (10%) were PPD-positive. Sixty-seven bus riders were sought for testing and 7 (19%) were purified protein derivative (PPD)-positive, with 1 bus rider subsequently diagnosed with active disease(Phillips et al., 2004).
    8. The Public Health Seattle and King County (PH-SKC) Tuberculosis Control Program, with assistance from the Washington State Department of Health and CDC, is continuing to investigate an ongoing outbreak(MMWR, 2003). As of September 30, 2003, PH-SKC had identified 44 outbreak-associated TB patients with dates of diagnosis during May 2002-September 2003(MMWR, 2003). All but three of the outbreak-associated patients were homeless at the time of diagnosis; 43 (98%) were born in the United States, 34 (77%) were male, 21 (48%) were American Indian/Alaska Native, and 17 (39%) were black. Of the 38 (86%) patients with pulmonary disease, 23 (61%) had acid-fast bacilli identified on sputum smear at diagnosis. Seven (16%) outbreak-associated patients also were infected with human immunodeficiency virus (HIV)(MMWR, 2003). Focused, intensified screening efforts for early detection and treatment of both TB disease and LTBI are under way to control transmission in the King County community. TB controllers, particularly those from western states, should consider the possibility of unrecognized TB outbreaks involving homeless persons in their communities(MMWR, 2003).
    9. The transient nature of a homeless persons life often interferes with the timely diagnosis and successful treatment of TB(McElroy et al., 2003). We describe an outbreak investigation of a cluster of TB cases at a large homeless shelter in Raleigh, North Carolina, and how the frequency of stays at the shelterincreased the risk of M. tuberculosis infection. Overcoming the challenge of finding additional undiagnosed cases and the many contacts in need of treatment for LTBI required novel approaches(McElroy et al., 2003). In addition to the initial index cluster of 9 patients, another 16 patients were identified. Isolates of M. tuberculosis from all 25 patients shared a matching DNA fingerprint pattern. All but 1 patient was male, 22 (88%) were African American, and 14 (56%) were human immunodeficiency virusinfected. An epidemiological link to a single shelter was identified for all but 1 patient. Earlier recognition of this shelter as a site of M. tuberculosis transmission could have been facilitated through innovative approaches to contact investigation and through genetic typing of isolates(McElroy et al., 2003).
    10. In January 2001, the US Centers for Disease Control and Prevention (CDC) assisted the Wichita-Sedgwick County Department of Health and the Kansas Department of Health and Environment in investigating a cluster of 22 TB patients diagnosed between 1994 and 2001. Patients included 10 men, nine women, and three children. Seven of the nine female patients had sputum acid-fast bacilli (AFB) smear-positive cavitary pulmonary TB at the time of diagnosis and worked as exotic dancers in the Wichita area. (Exotic dancers are usually women employed by clubs to dance nude or near-nude for the entertainment of men, although either sex can be the dancer or the observer.) All three pediatric patients had household contact with at least one exotic dancer with TB. Epidemiologic links to female patients had previously been established for the majority of male patients through routine contact investigation procedures(McElroy et al., 2003). In consultation with state and local health authorities, all adult outbreak-associated cases and selected named and unnamed contacts were reinterviewed using a network analysis questionnaire(McElroy et al., 2003). Network-based methods may provide evidence for direct connections among cases and persons with LTBI, as well as indirect evidence, such as overlap in attendance at places of social aggregation and drug using behaviors(McElroy et al., 2003). Network analysis can help discern behavior or relationship differences among various members of a seemingly similar group, and show the variation in behaviors that may explain transmission(McElroy et al., 2003).
    11. In May and June of 1994, four cases of TB caused by M. tuberculosis isolates resistant to isoniazid (H) and rifampin (R) were reported among clients of the same methadone treatment program (MTP). The MTP servers approximately 300 clients, and provides individual and group counseling, detoxification, and methadone maintenance services(Conover et al., 2001). Thirteen cases of MDR-TB were diagnosed among MTP clients during the outbreak period(Conover et al., 2001). Two cases were HIV negative and 11 were coinfected with HIV (median CD4 count 146 cells/ml |range 25-326|). All cases had isolates resistant to isoniazid and rifampin only, and 12 isolates available for RFLP analysis had matching4-band patterns by IS6110 typing and were also identical by pTBN12 typing. Overall mortality among cases during the outbreak period was 69.2% (9 / 13); five cases had received less than 2 weeks of treatment for MDR-TB at the time of death(Conover et al., 2001). Although some transmission of M. tuberculosis among MTP clients may have occurred outside the MTP, there is strong evidence that most transmission took place in the MTP setting. Evidence for transmission at the MTP includes conversions among staff without other known exposures during the outbreak period, no other identified site of exposure for sever cases despite extensive investigation, clustering of cases in a counseling group, and higher rates of skin test conversion during periods when an infectious case with sever cavitary disease was also in attendance(Conover et al., 2001).
    12. We recently investigated an outbreak of tuberculosis that affected four unrelated children who attended a family day care home (DCH). The source case was identified as the 40-year-old daughter of the DCH provider who assisted in the children's care. Our findings illustrate the significant risk of infection among children that can result from an unidentified case of active pulmonary tuberculosis in a DCH provider(Leggiadro et al., 1989).
    13. In March 1992, a 39-year-old HIV-infected male was admitted to San Mateo County General Hospital with a 3-month history of productive cough. Abundant acid-fast bacilli on initial sputum smears indicated pulmonary tuberculosis. Three days later, a 73-year-old male with tuberculosis, presenting with fevers and chills was admitted to the same hospital. The patient with the initial index case was a transient resident in two houses, in one of which the second person admitted also lived, in an economically depressed neighborhood known for its high crime rate and drug use. Public health workers discovered, on interview with the two affected individuals, that both houses provided lodging for several extended families with children and initiated an investigation(Leonhardt et al., 1994). Public health workers conducted interviews at the two residences in which the source patient resided and in the neighborhood. Children and adults indicated they lived in different residences in the neighborhood for various lengths of time, often with friends or relatives. Drug use, particularly use of crack cocaine, was disclosed by several individuals(Leonhardt et al., 1994). Fifty-seven percent (17 of 30) of the highly exposed contacts were 18 years of age or less(Leonhardt et al., 1994). Thirteen active cases (class III) were diagnosed, 11 involving children 18 years of age or less. Symptoms of active tuberculosis were present in four of the class III patients(Leonhardt et al., 1994).
  2. Transmission Information:
    1. From: Humans, Homo sapiens (at lifecycle stage: Bacilli) , To: Humans, Homo sapiens (at lifecycle stage: Bacilli)
      Mechanism: Tuberculosis is spread from person to person through the air by droplet nuclei, particles 1 to 5 um in diameter that contain M. tuberculosis complex. Droplet nuclei are produced when persons with pulmonary or laryngeal tuberculosis cough, sneeze, speak, or sing. They also may be produced by aerosol treatments, sputum induction, aerosolization during bronchoscopy, and through manipulation of lesions or processing of tissue or secretions in the hospital or laboratory. Droplet nuclei, containing two to three M. tuberculosis organisms, are so small that air currents normally present in any indoor space can keep them airborne for long periods of time. Droplet nuclei are small enough to reach the alveoli within the lungs, where the organisms replicate(American Thoracic Society, 2000).
    2. From: Humans, Homo sapiens (at lifecycle stage: Bacilli) , To: Mammals (non-human), Callithrix jacchus (at lifecycle stage: Bacilli)
      Mechanism: We believe the direction of transmission in this case to have been from human to monkey (anthropozoonosis). The fact that the animal had lived in the owners household from a very young age minimizes the possibility of infection through other sources and thus the possibility of passing on the infection to the owner(Michel and Huchzermeyer, 1998). Genomic typing of M. tuberculosis by the RFLP method is a powerful tool in epidemiological studies to trace common sources of infection. In our investigation this genomic typing method was successfully used to demonstrate the identity of the 2 isolates and at the same time the zoonotic character of tuberculosis(Michel and Huchzermeyer, 1998).
    3. From: Humans, Homo sapiens (at lifecycle stage: Bacilli) , To: Birds, Ara chloropterus (at lifecycle stage: Bacilli)
      Mechanism: This report describes a macaw with active tuberculosis caused by M. tuberculosis. Epidemiologic investigation revealed that two people who lived in the same house with the pet bird and who had close respiratory contact with it had active tuberculosis 3 to 4 years before diagnosis of tuberculosis in the bird. One patient did not adhere to antituberculosis treatment for more than 1 year. The bird probably contracted the disease from its human housemates(Washko et al., 2002).
    4. From: Mammals (non-human), Elephas maximus (at lifecycle stage: Bacilli) , To: Humans, Homo sapiens (at lifecycle stage: Bacilli)
      Mechanism: This report describes the first case of zoonotic M. tuberculosis transmission(Michalak et al., 1998). The possible mechanisms of transmission include close contact while handling and training elephants, cleaning the barn, participating in elephant necropsies, and living in close proximity to the elephant barn(Michalak et al., 1998).
    5. From: Mammals (non-human), Saimiri sciureus (at lifecycle stage: Bacilli) , To: Mammals (non-human), Macaca mulatta (at lifecycle stage: Bacilli)
      Mechanism: Six weeks after the death of monkey 1, an adult female rhesus monkey in the room that formerly housed monkey 1 was coughing and had an abscess in the right inguinal region. It had been in the colony for 21 months, and had been tuberculin-test negative when tested at 6-month intervals(Leathers and Hamm, 1976). A strong circumstantial case exists for transmission of infective material from one of the infected monkeys to others in the same room(Leathers and Hamm, 1976).
  3. Environmental Reservoir:
    1. Human population:
      1. Description: An estimated 2 billion people worldwide are infected with M. tuberculosis an enormous reservoir of potential tuberculosis cases(Tufariello et al., 2003).
  4. Intentional Releases:
    1. Currently no intentional releases information is available.
Diagnostic Tests Information
  1. Organism Detection Test:
    1. Acid Fast Bacilli (AFB) stain for light microscopy (Woods, 2002):
      1. Time to Perform: 1-hour-to-1-day
      2. Description: The first step in the diagnosis of mycobacterial infection is microscopic examination of a smear prepared from a concentrated specimen and stained for acid-fast bacilli (AFB)(Woods, 2002). The carbolfuchin stains (Ziehl-Neelsen and Kinyoun methods), viewed with a light microscope under oil immersion(Woods, 2002). AFB smear does not allow identification of the infecting mycobacterium to the species level(Woods, 2002).
      3. False Positive: 43%(American Thoracic Society, 1997).
      4. False Negative: 1%(American Thoracic Society, 1997).
      5. Picture(s):
    2. Acid Fast Bacilli (AFB) stain for fluorescence microscopy (Woods, 2002):
      1. Time to Perform: 1-hour-to-1-day
      2. Description: The first step in the diagnosis of mycobacterial infection is microscopic examination of a smear prepared from a concentrated specimen and stained for acid-fast bacilli (AFB)(Woods, 2002). The stains most commonly used are the fluorochrome stains (auramine-rhodamine or auramine O), examined by fluorescence microscopy under lower magnifications (x150 and x450). Mycobacteria are most easily detected by fluorochrome stains, with which the bacilli fluoresce a bright yellow-green or range-yellow (depending on the stain) against a black background. Because of the increased sensitivity and shorter time required for screening, fluorochrome stains, recommended by the CDC, are preferred(Woods, 2002). AFB smear does not allow identification of the infecting mycobacterium to the species level(Woods, 2002).
  2. Immunoassay Test:
    1. Tuberculin skin test (American Thoracic Society, 2000):
      1. Time to Perform: 1-to-2-days
      2. Description: The tuberculin skin test is currently the only widely used method for identifying infection with M. tuberculosis in persons who do not have tuberculosis disease. Although currently the tuberculin skin test antigens that are available are substantially less than 100% sensitive and specific for detection of infection with M. tuberculosis, no better diagnostic method is widely available. Proper use of the tuberculin skin test requires a knowledge of the antigen used (tuberculin), the immunologic basis for the reaction to this antigen, the technique(s) of administering and reading the test, and the results of epidemiologic and clinical experience with the test(American Thoracic Society, 2000). In the general U.S. population, the test's sensitivity is 0.59 to 1.0, the specificity is 0.95 to 1.0(Rose et al., 1995).
      3. False Positive: 0% - 5%(Rose et al., 1995).
      4. False Negative: 0% - 41%(Rose et al., 1995).
      5. Antigen:
      6. Antibody:
      7. Picture(s):
        • TST for TB - administer the TST (Core Curriculum on Tuberculosis (2000))



          Description: Administering the Tuberculin Skin Test: (1) Inject intradermally 0.1 ml of 5 TU PPD tuberculin. (2) Produce wheal 6 mm to 10 mm in diameter. (3) Do not recap, bend, or break needles, or remove needles from syringes. Follow universal precautions for infection control(Core Curriculum on Tuberculosis (2000)).
        • TST for TB - Interpret the TST (Core Curriculum on Tuberculosis (2000))



          Description: Administering the Tuberculin Skin Test: (1) Inject intradermally 0.1 ml of 5 TU PPD tuberculin. (2) Produce wheal 6 mm to 10 mm in diameter. (3) Do not recap, bend, or break needles, or remove needles from syringes. Follow universal precautions for infection control(Core Curriculum on Tuberculosis (2000)).
    2. QuantiFERON (CDC - Guidelines for safely working with M. tb):
      1. Time to Perform: 1-to-2-days
      2. Description: In 2001, the QuantiFERON-TB test (QFT) (manufactured by Cellestis Limited, Carnegie, Victoria, Australia) was approved by the Food and Drug Administration (FDA) as an aid for detecting latent Mycobacterium tuberculosis infection. This test is an in vitro diagnostic aid that measures a component of cell-mediated immune reactivity to M. tuberculosis. The test is based on the quantification of interferon-gamma (IFN-) released from sensitized lymphocytes in whole blood incubated overnight with purified protein derivative (PPD) from M. tuberculosis and control antigens(CDC - Guidelines for safely working with M. tb). Evaluation of diagnostic tests for LTBI in humans is hampered by the lack of a "gold standard." As a result, new tests are commonly compared with the TST, despite its well-documented limitations. Owing to the lack of a definitive standard, the IFN- assay was evaluated on the basis of its agreement with the TST in persons with varying degrees of risk for M. tuberculosis infection and in persons with documented and suspected active TB. Overall agreement between the TST and IFN- assay was good (83.1%, K= 0.60) as was agreement when the analysis was limited to persons for whom the test is intended, those subjects being screened for LTBI, groups 1 and 2 combined (84.7%, K= 0.55). Test concordance was 65% for persons with a positive TST and 90% for those with a negative TST(Mazurek et al., 2001).
      3. False Positive: Compared to TST: 10%(Mazurek et al., 2001).
      4. False Negative: Compared to TST: 32%(Mazurek et al., 2001).
      5. Antigen:
  3. Nucleic Acid Detection Test: