To evaluate trends in the occurrence and diagnosis of mycobacterial disease.

Prospective surveillance study using a central tuberculosis registry at a 611-bed teaching community hospital.

Data pertaining to 715 patients were entered into the registry between 1976 and 1991 on the basis of positive smears or cultures for acid-fast bacilli (AFB). Over time, the ratio of isolates of Mycobacterium tuberculosis to isolates of nontuberculous mycobacteria reversed (from 3.2 to 1 between 1976 and 1981 to 1 to 1.6 between 1986 and 1991). The sensitivity of the sputum AFB smear for diagnosis of pulmonary tuberculosis increased (from 0.73 to 0.96), but the positive predictive value of the sputum AFB smear declined (from 0.72 to 0.59). The acquired immunodeficiency syndrome epidemic accounted for these changes only to a small extent.

The increasing occurrence of non-tuberculous mycobacterial disease and the declining positive predictive value of the sputum AFB smear at this hospital imply that respiratory isolation and antituberculous therapy will be used inappropriately for many patients. The development and use of newer tests for early isolation and specific identification of M tuberculosis should be accelerated.

To evaluate tuberculin skin test (TST) conversions among a group of medical students.

Questionnaire sent to a medical school class in whom a cluster of TST conversions was noted, and interview and repeat TST of students with conversion.

County hospital and associated medical school.

Medical students, after their third year in medical school.

Of 165 students in the class, 115 (70%) responded; 10 reported TST conversions between the beginning of the third and the fourth year. Seven of 10 were interviewed, and all 10 were retested. Five students, all in a cohort who tested each other during a clinical clerkship with a tuberculin material previously reported to be associated with a high rate of false-positive TSTs, were TST negative on repeat. Five had persistently positive TSTs. One was exposed during a psychiatry clerkship to a resident with pulmonary tuberculosis. Four students appeared to have converted their TST during their third year in medical school. All four did their medicine clerkship at a large county hospital (P<0.02; odds ratio = 16.4) that had few infection control measures in place for tuberculosis isolation during the time of their exposure.

We recommend that medical students, as well as other healthcare professions students, be educated about infection control practices and skin tested at least annually during clinical training years.

To study the epidemiological, microbiological, and clinical features of infections due to Acinetobacter baumannii in a complex endemic situation over an 18-month period and to determine the clinical usefulness of plasmid DNA analysis of A baumannii in epidemiological investigations.

Review of medical and laboratory records. Antibiotic resistance patterns, biotyping, and plasmid profile analysis were used to characterize clinical and environmental isolates. Pulsed-field gel electrophoresis (PFGE) of chromosomal DNA was performed to verify results obtained with the other typing methods.

Four different intensive care units of an 800-bed tertiary care center in Cologne, Germany.

240 patients were colonized or infected with A baumannii during the study period. No seasonal variations were observed. The majority of isolates (53%) were recovered from the respiratory tract. Major infections occurred in 61 patients; these included 48 bacteremias and eight pulmonary infections. Five different epidemic strains were identified: one each was A baumannii biotype 2 and 6, and three were biotype 9. A baumannii biotype 9 accounted for the vast majority of isolates (88%), which were clustered into three epidemic strains demonstrating distinct plasmid profiles. Two of these were considered genetically related as shown by PFGE. Epidemic strains were multidrug resistant, being uniformly susceptible to imipenem only. An epidemiological investigation failed to identify any point source of infection. Barrier precautions and improved handwashing were instituted in three of the four units and significantly reduced the incidence of colonization and infection in these units. Attack rates remained unchanged, however, in the burn unit where control measures were not implemented.

Acinetobacter strains representing multiple biotypes and plasmid types were present in this endemic setting. Multidrug resistance in A baumannii is an important concern. Plasmid DNA analysis proved to be useful in epidemiological typing of A baumannii strains and may serve as a complementary typing system to traditional epidemiological methods.

Two cases of nosocomial legionellosis due to Legionella pneumophila serogroup 6 (Lp6) were identified in the intensive care unit. Both patients had a history of aspiration of nasogastric tube feedings, developed pulmonary infiltrates, had positive cultures for Lp6, had serological titer rises to Legionella, were treated, and recovered.

Isolates of Lp6 from the potable water system and patients were characterized by DNA restriction enzyme analyses using pulsed-field gel electrophoresis (PFGE).

Water samples grew >1O4 CFU/L of Lp6, and the same PFGE pattern was observed with the patient and water isolates. Potable water was used only for delivering medications and diluting feeding solutions given through the nasogastric tubes of the patients. Heat shock of the hot water system (140° to 160°F or 60° to 7O°C, 4 hours) was performed and the temperature was maintained between 131° to 140°F (55° to 60°C). Surveillance over 18 months revealed a reduction in Legionella to <102 CFU/L.

We speculate that nosocomial Legionella pneumonia occurred due to aspiration of nasogastric tube solutions diluted with tap water. A nursing practice change to use only sterile water to dilute feedings and flush medications for nasogastric administration was instituted. The hot water temperature at the faucet was increased to ≥131°F (≥60°C) to control Legionella. No further nosocomial cases have occurred.