John B. Bass

The treatment of tuberculosis.

Short-course chemotherapy has made the treatment of TB easier and better than ever, but it works only when patients take the drugs regularly. Compliance is a must for therapy to be successful. Physicians treating patients with tuberculosis should be acutely aware of noncompliance, and every effort to ensure adequate treatment must be put forth. Directly supervised therapy is an excellent option when enough resources are available. Intermittent regimens markedly reduce the manpower required for observed therapy. New agents are being tested for in vitro activity against M. tuberculosis, and clinical studies of those found to be potentially effective are needed to formulate new regimens against the ever-increasing threat of multidrug-resistant TB.

Use of a bronchoscopic protected catheter technique in the clinical evaluation of a new antibiotic

We prospectively compared the usefulness of a bronchoscopic protected catheter technique with the results from sputum cultures in the evaluation of moxalactam, a new beta-lactam antibiotic. The significance of a given isolate on protected catheter culture was determined by quantitative bacteriology. 32 patients with community-acquired pneumonia were enrolled in the study and 31 grew common lower respiratory tract pathogens from their protected catheter specimen. The most common single pathogens recovered were Streptococcus pneumoniae (11 patients) and Haemophilus influenzae (2). Mixed flora, predominantly anaerobes, were isolated from 15 patients, and 3 patients had mixed aerobic infections. All seven bacteremic cases had the identical organism isolated from the protected catheter specimen, confirming the accuracy of the technique. Comparisons with sputum cultures showed that the predominant organism on sputum culture was the same as that obtained from the protected catheter culture in only 13% of the cases. Sputum cultures revealed either no pathogen or a different pathogen in 23 cases, and no sputum could be obtained in 4. Compared to cultures of expectorated sputum, we found the protected catheter bronchoscopic culture technique to have the following advantages in the bacteriologic evaluation of moxalactam: 1) greater accuracy and sensitivity in bacteremic patients; 2) accurate delineation of the bacteriology of infections; and 3) a higher percentage of patients with evaluable bacteriology leading to greater efficiency during the investigation.

How good is the tuberculin skin test

Purified protein derivative is a relatively crude material containing several different antigens. The results of a skin test with purified protein derivative are dependent on the immunologic reactivity of the recipient of the test, and the final interpretation is dependent on the individual interpreting the test. Despite these limitations, the tuberculin skin test (TST) is one of the most accurate medical tests available. Using conservative assumptions, I have estimated the sensitivity of the TST at approximately 95% and the specificity at approximately 99% to 99.5%.2 If these assumptions are correct, the TST is more accurate than most tests commonly used in clinical medicine. Despite this high degree of accuracy, the TST is not good enough to give valid results in serial skin testing programs in most hospitals and other medical facilities where the prevalence of new infection is low (including facilities ordinarily considered to be at “moderately high risk”). The table translates the conversion rate in a serial skin testing program to the actual transmission rate of tuberculosis infection assuming a sensitivity of 0.95 and a specificity of 0.99 to 0.995. If the annual conversion rate in a skin testing program is less than 1%, most conversions will be false positives and the predictive value of an individual conversion will be poor. Conversion rates above 2% increase the predictive value of the test to greater than 50%, and results in skin testing programs with annual conversions of greater that 2% probably represent mostly true transmission of tuberculous infection. Conversion rates between 1% and 2% probably represent equal numbers of false-positive and true-positive tuberculin reactions. This issue of Infection Control and Hospital Epidemiology presents four reports concerning the TST.3-6 These reports are welcome, as the results of most serial skin testing programs in medical environments go unreported. Cook et al.4 report TST results among healthcare workers in New York City. The conversion rate in their study was approximately 1.3% annually—a rate that suggests equal numbers of true-positive and false-positive conversions. The presence of some true-positive conversions is supported by the increased conversion rate in high-risk settings and among foreign-born individuals, who would be expected to have a higher than average risk in their community away from the workplace. Some of the increased conversion rate among high-risk workers was probably the result of semiannual testing in this group compared with annual testing for low-risk workers, as more frequent testing will increase the cumulative false-positive rate if such a rate is constant for each test.2 Garber et al.3 report results of skin testing programs in 19 microbiology laboratories in New York City. The incidence of TST conversion in their study of 1% probably slightly favors false conversions over true conversions,

The role of bacterial super infection in extensive pulmonary tuberculosis: Data from protected brush cultures in untreated patients from the University of South Alabama Medical Center, Mobile, Alabama, USA

Pulmonary tuberculosis (TB) and bacterial pneumonia are both characterized by fever, cough, and purulent sputum production. Although TB alone can cause these symptoms, the possibility of a concomitant bacterial pneumonia has led some clinicians to treat these patients empirically with antibacterial agents. Neither the benefit of such empiric antibiotic therapy nor transtracheal aspirate cultures from patients with pulmonary TB have yielded consistent results. Consequently, we performed a prospective study to obtain lower airway secretions via a bronchoscopic protected specimen brush (PSB) technique for quantitative aerobic and anaerobic cultures from untreated patients with extensive pulmonary TB (defined as cavitary disease or involvement of > or = 3 segments). We obtained bronchoscopic samples from 3 untreated men aged 21, 61, and 60 years with extensive pulmonary TB. There was no significant bacterial growth (aerobic or anaerobic) from the specimens obtained. These results, therefore, do not support the hypothesis that bacterial pneumonia is a common concomitant of extensive pulmonary TB.

Tuberculosis and Pregnancy

Tuberculosis (TB) is a common infectious disease causedbyMycobacterium tuberculosis, which commonly attacks the lungs (as pulmonary TB) but can also affect other organ systems. Over one third of the world’s population now carries the TB bacterium. Not everyone infected develops active TB, and latent (asymptomatic) infection is common. TB is a problem not only in the developing world and an increasing number of people in the developed world are contracting TB. The World Health Organization declared TB a global health emergency in 1993 (1, 2, 3). From the earliest recognition of TB, the scientific community has had widely differing beliefs about its implications for maternal and fetal health and well being. Two millennia ago, the ancient Greeks felt that women with TB who became pregnant had a much better disease course than their non-pregnant counterparts. In fact, they believed that pregnancy was so beneficial for women with active TB that these women were encouraged to become pregnant if they were not already so. This belief persisted through the Middle Ages and into the early nineteenth century. There was a drastic change in the nineteenth and twentieth centuries, when the prevailing sentiment was that women with TB did much worse after becoming pregnant. Therapeutic abortions were not only common, but were recommended and for a time were the standard of care (4, 5). We now have evidence that suggests that pregnancy does not alter the course of TB. Though the studies done to support this evidence are small, they nonetheless demonstrate that women with TB who become pregnant are not at increased risk for an adverse maternal or fetal outcome (6). However, with increasing rates of TB infection in this country, partially as a result of Human Immunodeficiency Virus (HIV) infection, and partially because of larger populations of immigrants from areas of the world with high prevalence of TB, screening for and treatment of TB during pregnancy are becoming more important. In disadvantaged populations with limited access to care, often the only contact with the health care system is during pregnancy (7, 8). Since screening