chapter  20
12 Pages

Mycobacterium tuberculosis and the Atypicals Introduction

Tuberculosis, the insidious killer that seemed to be fading from view, is again on the rise. Worldwide, there arc 30 million eases . 1Y Even in developed countries mycobacterial infections have resurged, due to their proclivity to thrive in the immunosuppressed, whether immunosuppression results from cancer therapy, drug abuse, or AIDS .34.46 With multiple antimicrobials available, the major problem is diagnosis . B iopsy of lung tissue is frequently resorted to. 66 The diagnosis may be made only at autopsy.76 It is apparent that in any tissue the tubercle bacillus grows minimally as an acid-fast rod, the predominant growth consists of pleomorphic structures , acid-fast. only with slightly modified stains (Figure 20-1 ) .83 In a long series of cases , employing the sensitive auramine­ rhodamine fluorescent stain, only 50% of the specimens eventually yielding positive cultures showed bacilli in direct smear.69 Even in AIDS patients ' sputum smears are frequently negative. 20 Diagnosis also is difficult because with decades, x-ray findings have changed, as have clinical symptoms.62 For the Mycobacterium avium complex (MAC), sputum smears may be positive only in 1 6% of cases .58