To investigate a cluster of cases of legionnaires' disease among patients at a hospital.

A university hospital that is a regional transplant center.

Retrospective review of microbiology and serology data from the hospital laboratories and prospective surveillance via the radiology department; a case-control study and environmental sampling within the hospital and from nearby cooling towers.

Diagnosis of seven cases of legionnaires' disease in the first 9 months of 1996 led to recognition of a nosocomial outbreak that may have begun as early as 1979. Review of charts from 1987 through September 1996 identified 25 culture-confirmed cases of nosocomial or possibly nosocomial legionnaires' disease, including 18 in bone marrow and heart transplant patients. Twelve patients (48%) died. During the first 9 months of 1996, the attack rate was 6% among cardiac and bone marrow transplant patients. For cases that occurred before 1996, intubation was associated with increased risk for disease. High-dose corticosteroid medication was strongly associated with the risk for disease, but other immunosuppressive therapy or cancer chemotherapy was not. Several species and serogroups of Legionella were isolated from numerous sites in the hospital's potable water system. Six of seven available clinical isolates were identical and were indistinguishable from environmental isolates by pulsed-field gel electrophoresis. Initial infection control measures failed to interrupt nosocomial acquisition of infection. After extensive modifications to the water system, closely monitored repeated hyperchlorinations, and reduction of patient exposures to aerosols, transmission was interrupted. No cases have been identified since September 1996.

Legionella can colonize hospital potable water systems for long periods of time, resulting in an ongoing risk for patients, especially those who are immunocompromised. In this hospital, nosocomial transmission possibly occurred for more than 17 years and was interrupted in 1996, after a sudden increase in incidence led to its recognition. Hospitals specializing in the care of immunocompromised patients (eg, transplant centers) should prioritize surveillance for cases of legionnaires' disease. Aggressive control measures can interrupt transmission of this disease successfully.

To determine the influence of catheter site and type (single- vs triple-lumen) on infection rates associated with central venous catheterization.

Prospective observational study of all nontunneled central venous catheters over a 28-month period. Data collected included patient characteristics, insertion site, catheter type, and receipt of parenteral nutrition. End points were clinical infection (bacteremia or site infection) and catheter contamination (clinical infection or colonization with >15 colonies on semiquantitative culture).

Medical-surgical wards of Veterans' Affairs hospital.

Three hundred catheters were inserted into 204 patients. Seventy percent were inserted into upper-body sites, and 30% were inserted into the femoral vein. Forty-five percent were triple-lumen catheters. Bacteremia occurred in 2.7% of catheter insertions; insertion-site infections developed in 1.3%, and catheter colonization developed in 12%. Catheter contamination was associated with emergent insertion (odds ratio [OR], 6.2; 95% confidence interval [CI95], 1.1-36.7; P=.04) by logistic regression and with femoral location (hazard, 4.2; CI95, 2.0-8.8; P=.0001) and history of transplantation (hazard, 2.8; CI95, 1.1-6.7; P=.024) by Cox regression. Clinical infection was not associated with any of the risk factors evaluated, although there was a trend for association with femoral location by Cox regression (hazard, 4.7; CI95, 0.82-26; P=.08). We did not identify an association between infection and use of triple-lumen catheters or parenteral nutrition.

Our data support an association between intravenous catheter contamination and insertion at a femoral site.

To analyze possible risk factors for death among patients with nosocomial candidemia. To identify risk factors for death in patients with candidemia, we analyzed demographic, clinical, and microbiological data.

Six tertiary hospitals in Brazil.

A cohort of 145 patients with candidemia.

26 possible risk factors for death, including age, underlying disease, signs of deep-seated infection, neutropenia, number of positive blood cultures, removal of a central venous catheter, etiologic agent of the candidemia, susceptibility pattern of the isolate to amphotericin B, and antifungal treatment were evaluated by univariate stepwise logistic regression analysis.

Non-albicans species accounted for 63.4% of the candidemias. Risk factors for death in univariate analysis were older age, catheter retention, poor performance status, candidemia due to species other than Candida parapsilosis, hypotension, candidemia due to species other than Candida parapsilosis, and no antifungal treatment. In multivariate analysis, older age and non-removal of a central venous catheter were the only factors associated with an increased risk for death.

These data suggest that patients with candidemia and a central venous catheter should have the catheter removed.

To investigate suspected pseudo-outbreaks of Mycobacterium tuberculosis (MTB) during August 1994 and July 1995 among patients who did not have clinical findings consistent with tuberculosis.

Retrospective and prospective surveys of all clinical and laboratory data using standard epidemiological tools and DNA fingerprinting.

A university-affiliated community hospital.

Those with positive MTB cultures during periods when we noted that the number of MTB positive cultures greatly outnumbered the usual monthly average (retrospective analysis, 1994) and patients with positive MTB cultures without clinical findings consistent with tuberculosis (prospective survey, 1995).

Epidemiological and molecular studies revealed specimen cross-contamination in the laboratory due to a faulty exhaust hood. Improvement in laboratory ventilation and change of the implicated hood prevented further specimen contamination.

The identification of positive MTB cultures from patients without clinical evidence of tuberculosis should be a signal to suspect laboratory contamination and implement control measures. These should include a thorough epidemiological investigation, DNA fingerprint analysis, and an environmental inspection.

To describe investigations into an increase in hemodialysis-related bacteremia that occurred in our hospital in the first 6 months of 1996.

Hemodialysis unit in a tertiary-care medical center.

Prospective surveillance for hemodialysis bacteremia has been performed for several years. Cases that occurred in 1995 were compared to cases in the first 6 months of 1996. Unit data on dialysis runs and method of dialysis access were used to calculate rates. Nested polymerase chain reaction (PCR) was used to type 18 Staphylococcus aureus isolates from 1996. A case-control study comparing 80 randomly selected hemodialysis patients from 1995 and 1996 was performed to examine infection risk factors.

The hemodialysis bacteremia rate was 1.2 per 1,000 runs in 1995 and 2.8 per 1,000 in the first 6 months of 1996 (P=.0009). The 25 cases in 1995 and 32 in the first half of 1996 were similar in age, gender, means of vascular access, and micro-bial etiology. Central venous catheter (CVC) access accounted for >90% of cases in both time periods. S aureus was the most common microbial etiology (53% of the 1996 cases). PCR typing of S aureus isolates from 1996 demonstrated five different strains, the most common having six isolates. The use of CVCs as a means of vascular access abruptly increased in the unit in January 1996, from <30% of dialysis runs in 1995 to >40% in 1996 (P<.001), associated with structural changes in healthcare delivery in the region resulting in delays in performing surgical procedures, such as creation of vascular grafts and fistulae.

A marked increase in hemodialysis bacteremia occurred in 1996, associated with increased reliance on CVCs for vascular access in hemodialysis patients during a period of healthcare restructuring.

To compare resource use by diagnostic outcome among hospital admissions during which tuberculosis (TB) was suspected.

Retrospective study based on chart review and microbiology laboratory data.

The department of medicine in a municipal hospital serving central Brooklyn, New York.

We identified all adult admissions in 1993 during which TB was suspected. We assigned each admission to one of four mutually exclusive groups defined by the results of microbiological tests (acid-fast bacilli [AFB] smear and culture): culture-positive and smear-positive (C + S +); culture-positive and smear-negative (C + S−); culture-negative and smear-positive (C−S+); or culture-negative and smear-negative (C−S−). Each admission was divided into two separate periods to which the utilization of medical resources was assigned: the diagnostic and the postdiagnostic periods, which were separated by the date of receipt of the first definitive culture report.

Data on 519 admissions (93 C+S+; 57 C+S−; 30 C−S+; and 339 C−S−) were analyzed. Although C+S+ were more likely than other groups to have an admitting diagnosis of TB, approximately one quarter of the admissions without TB (C−S+, C−S−) were admitted with the principal diagnosis of TB. For the four groups, C+S+, C+S−, C−S+, and C−S−, the respective rates of TB isolation and anti-TB treatment, and median lengths of isolation were 98%, 87%, and 34 days; 74%, 74%, and 7 days; 83%, 83%, and 15 days; and 44%, 29%, and 0 days. During the diagnostic period, the rate and length of isolation were similar in the AFB-smear—positive groups (C+S+ and C−S+). We estimated that admissions without culture-proven TB (C−S+ and C−S−) accounted for 3,174 (36%) of the 8,712 days of TB isolation expended and for 65% of the 16,671 days of anti-TB treatment. The vast majority of this resource consumption (2,737 [86%] of 3,174 days of isolation) occurred during the diagnostic period before a definitive culture result was known.

Our results suggest that prolonged diagnostic uncertainty and misclassification of cases due to false-positive and false-negative smears are associated with substantial medical-resource consumption. New diagnostic modalities that reduce the period of diagnostic uncertainty could reduce the utilization of resources later found to be unnecessary

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.