If You Had Tb Can You Get It Again
Background and epidemiology : First exposure to tuberculosis (TB) usually results in a clinically silent infection. Often the only sign is a positive reaction to a skin examination with purified protein derivative. Most clinically relevant TB is thought to be a postprimary infection acquired past the reactivation of a previously dormant chief (endogenous) infection. There have been some reports of exogenous reinfection with multiple-drug–resistant strains of Mycobacterium tuberculosis, but these were restricted to HIV-positive patients who were immunocompromised.1
Yet, findings from a written report conducted in 2 poor suburban communities in Cape Town, South Africa, propose that reinfection may be more mutual than previously idea.ii Participants had had an episode of postprimary TB treated and cured between 1992 and 1998 that was followed by a 2d, new episode of postprimary disease. The study is unique for its careful attention to documenting the beginning cure and the fact that sputum samples were bachelor for Deoxyribonucleic acid fingerprinting of tuberculosis organisms by means of brake fragment length polymorphism (RFLP) analysis.
Although the rates of TB infection were high in these communities and many patients had at least two episodes of postprimary infection, only 16 patients had their M. tuberculosis organisms genotyped by ways of RFLP. For 12 of the 16 patients the banding patterns of the organisms in the two episodes were different: they had been reinfected with an exogenous (new) organism. The authors were able to confirm that 15 of the 16 participants did non accept HIV antibodies. In this region of S Africa, TB reinfection later an initial infection has been cured appears to be an important crusade of postprimary infection and may be responsible for up to 75% of cases of postprimary illness (95% confidence interval 50%–94%).
Clinical management : Currently in Northward America, elderly people in whom clinical TB develops are assumed to have a reactivated earlier infection. The findings from the South Africa study strongly suggest that at least some of the cases that are identified equally existence endogenous reactivation may in fact be exogenous reinfection. These results may accept implications for TB command in North America. For example, a clinician who has an elderly patient with TB may be less certain that the offending strain was caused by the patient decades before and is, therefore, sensitive to standard drug therapy. If the infection is indeed new, the organism is more likely to exist resistant to therapy. Also, it may be prudent to provide chemoprophylaxis for people exposed to a patient with agile TB, even if the patient has a history of previous infection.2
Nonetheless, the master direction strategy must still be the treatment of clinical infection, regardless of whether it was acquired endogenously or exogenously. Directly observed short-course treatment (DOTS) and the associated strategies for isolating the patient and identifying contacts remain the current mainstay of mod TB command and treatment.iii
Control and prevention : The findings from South Africa, especially if confirmed in other populations (a study from the Netherlands4 suggests that exogenous reinfection may be very rare, possibly related to the probability of exposure5), have implications for public health. Get-go, public health physicians should no longer presume that TB in an elderly person is simply due to reactivation of a previous infection. The possibility that the patient has a newly acquired infection will require a diligent search in the community for the source of the infection. Second, if main infection does non convey immunity to subsequent infection with an organism of a different genotype, then there are implications for efforts to develop a vaccine against TB. A vaccine confronting a single genotype may not be effective. To improve their investigation of new cases, public health epidemiologists in North America should consider the need to genotype TB strains in all cases.
John Hoey CMAJ
Figure. Recurrent turberculosis due to reinfection in South Africa: Implications for Canada? Photo past: Art Explosion
References
ane. Fine PEM, Modest PM. Exogenous reinfection in tuberculosis. Northward Engl J Med 1999;341:1226-7. [PubMed]
2. Van Rie A, Warren R, Richardson G, Victor TC, Gie RP, Enarson DA, et al. Exogenous reinfection as a crusade of recurrent tuberculosis later curative treatment. North Engl J Med 1999;341: 1174-9. [PubMed]
three. Hershfield Eastward. Tuberculosis: 9. Treatment. CMAJ 1999;161(four):405-xi. Available: www .cma .ca /cmaj/vol-161/effect-4/0405.htm [PMC free commodity] [PubMed]
4. De Boer Every bit, van Soolingen D, Borgdorff MW. Recurrent tuberculosis due to exogenous reinfection [letter]. N Engl J Med 2000;342:1050-one. [PubMed]
5. Van Rie V, Warren R, van Helden R. Recurrent tuberculosis due to exogenous reinfection [response]. Northward Engl J Med 2000;342:1051.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC99361/
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