A cluster of cerebrospinal fluid Gram's stains showing gram-positive bacilli and of cerebrospinal fluid cultures growing Bacillus species in a large community teaching hospital prompted an epidemiologic and microbiologic investigation. Pseudomeningitis was suspected and confirmed when cultures of uninoculated commercial trypticase soy broth with 5% Fildes enrichment grew Bacillus species. Secondary contamination of the pipettes used for inoculation accounted for the positive cerebrospinal fluid Gram's stains. The costs of this pseudo-outbreak included unnecessary antibiotic therapy, lumbar punctures, and hospitalization. Such adverse effects can be minimized by increased physician awareness of pseudoinfections and by prompt investigation of such occurrences.

An epidemic of adenovirus 7a in our neonatal intensive care nursery and intermediate care nursery in July and August 1987 caused the death of two patients. Significant symptomatic infection possibly due to the virus occurred in nine patients, ten staff, and three parents, of whom three patients, three staff, and one parent were positive by culture. As a direct consequence of the outbreak, 58 staff days of work were lost; the intensive care nursery had to be closed to admissions for 19 days and the intermediate care nursery for 14 days. Seventeen newborns were transferred to other hospitals and four mothers were sent elsewhere for delivery. Control measures, which included cohorting of patients, use of gloves, gowns and goggles, and exclusion of symptomatic staff from the unit, appeared effective. Rapid immunofluorescence testing of virological specimens was of little use in monitoring the outbreak, largely because of poor specimen quality. This outbreak further underlines the ease of transmission and high morbidity of neonatal adenovirus infection.

Although the vulnerability of patients with sickle cell disease to infection with encapsulated organisms is well recognized, nosocomial transmission of infection has not been studied in this population. We describe eight serious, nosocomially transmitted infections in four adult patients hospitalized for complications of sickle cell disease, which led to death in one patient and prolonged hospital stays in three others. Although we have not surveyed all patients with sickle cell disease for rates of nosocomial infection, the cases presented suggest that these patients may be at increased risk. Risk can be reduced if health care workers are especially vigilant in adhering to handwashing and other infection control measures when caring for these patients. Additionally, we recommend that a patient with sickle cell disease not share a room with a patient known to have or suspected of having a nosocomial or community-acquired infectious disease.

The CDC category I recommendation for high-level disinfection of pressure-monitoring transducers between uses imposes substantial costs. This practice has not been shown to be useful when disposable transducer domes are used. A prospective, randomized, double-blind study assessed the consequences of wiping transducers with alcohol between uses rather than sterilizing with ethylene oxide. We studied 5,197 transducer courses with disposable domes involving 2,202 patients in intensive care units during 15 months. There was no significant difference between the two treatment regimens in the risk of positive cultures of fluids from monitored lines, of cultures of cannula tips or of a positive blood culture. We conclude that under normal conditions, ie, in the absence of a cluster of transducer-related bacteremias, wiping transducers with alcohol between uses is sufficient when disposable domes are used.

Antibiotic combinations are often used in the therapy of infectious diseases to broaden the antibacterial spectrum and to enhance antimicrobial activity. Another potential reason for combination therapy is to reduce or prevent the emergence of resistant organisms during therapy. Antituberculous chemotherapy provides a classic example in which drug combinations have successfully prevented the emergence of drug-resistant organisms and improved clinical outcome. The purpose of this brief report is to review the success of combination therapy in preventing resistance in more common bacterial infections.

The emergence of resistance during single-drug therapy is a well-documented clinical phenomenon, especially with the broad-spectrum ß-lactams against gram-negative bacilli. As with Mycobacterium tuberculosis, the resistant organisms are generally thought to be naturally occurring mutants selected by drug exposure. Because mutation frequencies appear to vary from 10-6 to 10-8, it is not surprising that emergence of resistant organisms observed clinically occurs primarily at sites of high organism density, such as the respiratory and urinary tracts.

Clinical epidemiologic studies often focus on the identification of risk factors associated with hospital-acquired infections and the subsequent effects of preventive measures. Two study designs commonly used are the prospective design and the retrospective design. Both of these designs and the associated data collection issues were defined and discussed in the first article of this series. This article reviews the statistical analysis for a dichotomous risk factor and the presence or absence of a given disease for unmatched data. We focus our attention primarily on the unmatched prospective study, although we present formulae for the retrospective study as well.