Tetracycline resistance determinants in Mycobacterium and Streptomyces species.
Two of seven tetracycline-resistant (Tcr) Mycobacterium fortuitum group isolates and six Tcr clinical Streptomyces
isolates carried gram-positive Tcr determinants (Tet K and Tet L) and Streptomyces resistance determinants (Otr A, Otr
B, and Otr C). This represents the first documentation of the acquisition by mycobacteria of determinants coding for
antibiotic resistance and suggests the potential for the spread of antibiotic resistance determinants within mycobacterial
Antimicrob Agents Chemother. 1994 June; 38(6): 1408-1412.
Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. It includes many pathogens
known to cause serious diseases in mammals, including tuberculosis and leprosy.
Mycobacteria can colonize their hosts without the hosts showing any adverse signs. For example, billions of people
around the world are infected with M. tuberculosis but will never know it because they will not develop symptoms.
Mycobacterial infections are notoriously difficult to treat. The organisms are hardy and due to their cell wall, which is
neither truly gram negative nor positive and unique to the family, they are naturally resistant to a number of antibiotics
that utilize the destruction of cell walls, such as penicillin. Also, because of this cell wall, they can survive long exposure
to acids, alkalis, detergents, oxidative bursts, lysis by complement and antibiotics which naturally leads to antibiotic
Most mycobacteria are classified into two categories, the fast-growing kind and the slow-growing kind, based on
laboratory growth characteristics. All mycobacteria are aerobic and acid fast.
All Mycobacteria share a characteristic cell wall, thicker than in many other bacteria, which is hydrophobic, waxy and
rich in mycolic acids/mycolates. The mycobacterial cell wall makes a substantial contribution to the hardiness of this
Mycobacteria tend to be fastidious (difficult to culture), sometimes taking over two years to develop in culture. As well as
being fastidious, some species also have extremely long reproductive cycles (M. leprae, for example, may take more
than 20 days to proceed through one division cycle; E. coli, for comparison, takes only 20 minutes), making laboratory
culture a slow process.
Mycobacteria are widespread organisms, typically living in water (including tap water treated with chlorine) and food
sources. Some, however, including the tuberculosis and the leprosy organisms, appear to be obligate parasites and are
not found as free-living members of the genus.
Mycobacteria can be classified into several major groups for purpose of diagnosis and treatment: M. tuberculosis
complex which can cause tuberculosis: M. tuberculosis, M. bovis, M. africanum, and M. microti; M. leprae which causes
Hansen's disease or leprosy; Nontuberculous mycobacteria (NTM) are all the other mycobacteria which can cause
pulmonary disease resembling tuberculosis, lymphadenitis, skin disease, or disseminated disease.
Emergence of a Unique Group of Necrotizing Mycobacterial Diseases ...Emergence of a Unique Group of Necrotizing
Mycobacterial Diseases from Emerging ... Many NTM diseases, such as those caused by Mycobacterium avium
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JAMA, 2000 Oct 4, 284(13), 1683 - 8
Transmission of Mycobacterium tuberculosis from medical waste; Johnson KR et al.; CONTEXT: Washington State has
a relatively low incidence rate of tuberculosis (TB) infection . However, from May to September 1997, 3 cases of
pulmonary TB were reported among medical waste treatment workers at 1 facility in Washington . There is no previous
documentation of Mycobacterium tuberculosis transmission as a result of processing medical waste . OBJECTIVE: To
identify the source(s) of these 3 TB infections . DESIGN, SETTING, AND PARTICIPANTS: Interviews of the 3 infected
patient-workers and their contacts, review of patient-worker medical records and the state TB registry, and collection of
all multidrug-resistant TB (MDR-TB) isolates identified after January 1, 1995, from the facility's catchment area; DNA
fingerprinting of all isolates; polymerase chain reaction and automated DNA sequencing to determine genetic mutations
associated with drug resistance; and occupational safety and environmental evaluations of the facility . MAIN
OUTCOME MEASURES: Previous exposures of patient-workers to TB; verification of patient-worker tuberculin skin test
histories; identification of other cases of TB in the community and at the facility; drug susceptibility of patient-worker
isolates; and potential for worker exposure to live M tuberculosis cultures . RESULTS: All 3 patient-workers were
younger than 55 years, were born in the United States, and reported no known exposures to TB . We did not identify
other TB cases . The 3 patient-workers' isolates had different DNA fingerprints . One of 10 MDR-TB catchment-area
isolates matched an MDR-TB patient-worker isolate by DNA fingerprint pattern . DNA sequencing demonstrated the
same rare mutation in these isolates . There was no evidence of personal contact between these 2 individuals . The
laboratory that initially processed the matching isolate sent contaminated waste to the treatment facility . The facility
accepted contaminated medical waste where it was shredded, blown, compacted, and finally deactivated . Equipment
failures, insufficient employee training, and respiratory protective equipment inadequacies were identified at the facility .
CONCLUSION: Processing contaminated medical waste resulted in transmission of M tuberculosis to at least 1 medical
waste treatment facility worker . JAMA . 2000;284:1683-1688.