To evaluate adherence to components of the Centers for Disease Control and Prevention (CDC) guidelines for preventing the transmission of Mycobacterium tuberculosis in healthcare facilities.

Multihospital study using direct observation and a standardized questionnaire.

Three urban hospitals (two county hospitals and one private community hospital) in counties in California with a high number and incidence rate of tuberculosis (TB) cases.

The ventilation performance of treatment and TB-patient isolation rooms was assessed. Questionnaire data regarding TB control policy and procedures were obtained through interviews with the person(s) responsible for each program component; review of written TB control plans, training, and educational materials; and attendance at hospital TB control meetings and trainings.

Twenty-eight percent of isolation rooms tested (7/25) were under positive pressure; 83% of rooms tested (20/24) had six or more nominal air changes per hour (ACH), but supply air did not mix rapidly with room air. Therefore, the nominal ACH likely overestimated the effective ACH and the subsequent protection provided. In virtually all rooms tested (26/27), air potentially containing M tuberculosis aerosol moved toward, rather than away from likely worker locations. None of the hospitals regularly checked the performance of engineering controls. Only one hospital adhered to the CDC minimum requirements for respiratory protection. Training of healthcare workers generally was underutilized as a TB prevention measure. Hospitals did not provide comprehensive counseling regarding the need for healthcare workers to know their immune status and the risks associated with M tuberculosis infection in an immunocompromised individual. Employee representatives did not have a voice in TB-related decision making.

Important aspects of day-to-day TB control practice did not conform to the written TB control policy. Subsequent to the identification of TB patients, healthcare workers at all three hospitals were potentially exposed to M tuberculosis aerosol due to breaches in negative-pressure isolation, the limitations of dilution ventilation, and the failure to maintain engineering controls and to implement respiratory protection controls fully These findings lend support to the Occupational Safety and Health Administration's policy presumption that, absent clear evidence to the contrary, newly acquired healthcare-worker M tuberculosis infections are work-related.

To test the hypothesis that use of disposable thermometers would result in lower rates of nosocomial Clostridium difficile diarrhea and of total nosocomial infections, compared with electronic thermometers.

Prospective randomized crossover trial.

A 700-bed university hospital providing primary and tertiary care.

All patients admitted to a group of 20 inpatient nursing units.

20 nursing units were randomized into two groups. One group randomly was assigned exclusive use of single-use disposable thermometers for patient temperature measurement, and the other group was assigned exclusive use of electronic thermometers. After 6 months, the assignments were reversed.

Rates of C difficile infections, total nosocomial diarrheal episodes, and total nosocomial infections were prospectively followed in each study unit over 11 months.

26,350 patients were admitted to the study units and hospitalized for 120,529 patient days. There were 947 nosocomial infections (7.86 per 1,000 patient days). Nosocomial C difficile- associated diarrhea defined by positivity to both toxin B (titer ≥1:10) and toxin A was detected in 32 patients (3.4% of all nosocomial infections). A significantly lower rate of nosocomial C difficile-associated diarrhea was observed with disposable thermometer use (0.16 per 1,000 patient days) compared with electronic thermometer use (0.37 per 1,000 patient days, relative risk [RR]=0.44; 95% confidence interval [CI95], 0.21-0.93, P=.026). There was no difference in overall rates of nosocomial infection between the disposable and electronic groups (8.03 and 7.68 infections per 1,000 patient days, respectively; RR, 1.04; CI95, 0.92-1.19; P=.52) or in the overall rate of nosocomial diarrhea (3.34 and 3.40 per 1,000 patient days, respectively; RR, .98; CI95, 0.81-1.19; P=.87).

The incidence of nosocomial C difficile diarrhea was reduced significantly by using single-use, disposable thermometers as compared with electronic thermometers, but there was no effect on either the overall rate of nosocomial diarrhea or the rate of total nosocomial infections.

To investigate possible cross-contamination of laboratory specimens, as suggested by an increased incidence of newly diagnosed patients with tuberculosis, many of whom had all negative smears for acid-fast bacilli and only one positive Mycobacterium tuberculosis culture referred to as “negative smears, one positive” or NSOP.

Medical-record reviews were performed for all patients with NSOP results diagnosed at this facility within a 9-month period. Laboratory logbooks were reviewed for all isolates processed; DNA fingerprinting was performed on available isolates.

Of 80 patients with NSOP results, 45 (56%) were found to have false-positive cultures resulting from laboratory contamination with H37Ra, an avirulent stock strain of Mycobacterium tuberculosis.

Laboratory cross-contamination resulted in the false diagnosis of tuberculosis in at least 45 individuals. Use of the Mycobacteria Growth Indicator Tube may have contributed to these contamination incidents by detecting small numbers of contaminating mycobacteria that may not have been detected with less sensitive media.