Paenibacillus macerans pseudobacteremia resulting from contaminated blood culture bottles in a neonatal intensive care unit.

Paenibacillus species are gram-positive, rod-shaped, spore-forming aerobes that are abundant in nature and closely related to Bacillus. Between June 24 and June 30, 1999, 8 neonates in our neonatal intensive care unit had positive blood cultures for Paenibacillus macerans. This cluster of positive blood cultures with an unusual pathogen suggested a pseudoepidemic. Investigation revealed that the most likely etiology of the pseudobacteremia was environmental contamination of the rubber stoppers in blood culture bottles. This was confirmed by environmental sampling and simulated inoculation studies. This pseudobacteremia outbreak highlights the importance of adhering to well-established methods for blood culture collection and ongoing infection control surveillance.

Persistent contamination of fabric-covered furniture by vancomycin-resistant enterococci: implications for upholstery selection in hospitals.

Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens in hospitals throughout the United States. An increasing concern with respect to VRE dissemination is survival on, and potential transmission from, environmental surfaces within health care institutions. Therefore, we assessed survival of VRE on fabric chairs in an attempt to determine the optimal upholstery for the health care setting. VRE was identified on 3 of 10 seat cushions sampled, including 2 chairs in a room of a patient with known VRE. After performing simulated contamination experiments, all samples were positive at 72 hours and 1 week after inoculation. Contamination of the upholstery could be prevented by placing a sheet folded 4 times or a bath blanket folded in half on the seat cushion. In conclusion, VRE are capable of prolonged survival on fabric seat cushions and can be transferred to hands. Environmental surfaces such as chairs may serve as a potential reservoir for nosocomial transmission of VRE, and an easily cleanable, nonporous material is the preferred upholstery in hospitals.

Molecular epidemiology of vancomycin-resistant enterococci: a 2-year perspective.

OBJECTIVE: To determine the molecular epidemiology of vancomycin-resistant enterococci (VRE) at our medical center in order to identify the extent of strain clonality and possible transmission patterns of this pathogen. DESIGN: An important facet of our infection control program includes molecular typing of all clinical and surveillance isolates of VRE to determine transmission patterns in the hospital. Molecular strain typing is performed by restriction endonuclease analysis (REA) of genomic DNA. REA patterns are visually compared to categorize VRE strains into type and subtype designations. SETTING: A 588-bed, university-affiliated, tertiary-care hospital and a neighboring 155-bed rehabilitation facility. RESULTS: From January 1995 through December 1996, 379 VRE isolates were collected from 197 patients. Thirty-three genotypes were determined by REA typing; 15 genotypes were implicated in 29 instances of potential nosocomial transmission. Three major clusters of VRE involving patients on multiple nursing units and two adjacent hospitals were identified. The remaining instances of nosocomial transmission occurred in small patient clusters. CONCLUSIONS: In conclusion, the VRE epidemic at this medical center is polyclonal. VRE transmission patterns are complex, and, while large clusters do occur, the usual pattern of nosocomial acquisition of this pathogen occurs in the setting of "mini-clusters".

Medical and economic benefit of a comprehensive infection control program that includes routine determination of microbial clonality.

Nosocomial infections are a major part of the problem of reemerging pathogens causing infectious diseases, affecting 5% of patients hospitalized in the United States during 1995. We assessed the medical and economic effects on the overall nosocomial infection rate of an intervention that provided an enhanced, integrated infection control program, including an in-house molecular typing laboratory capability to rapidly assess microbial clonality. Data on nosocomial infections for 24 months prior to the change in approach to infection control were compared with data from the 24 months immediately following implementation of the new program. Infections per 1,000 patient-days and percentage of hospitalized patients in whom nosocomial infection developed were assessed. Overall, nosocomial infections per 1,000 patient-days decreased more than 10% (P = .027), and percentage of patients with nosocomial infection decreased 23% during the post-intervention period compared with the previous control 24 months. This translated to a mean reduction of some 270 patients per year with nosocomial infection, and lowering of actual health care costs for our institution by $4,368,100 over the 2 years of the intervention.

Thirteen-year evolution of azole resistance in yeast isolates and prevalence of resistant strains carried by cancer patients at a large medical center.

Drug resistance is emerging in many important microbial pathogens, including Candida albicans. We performed fungal susceptibility tests with archived isolates obtained from 1984 through 1993 and fresh clinical isolates obtained from 1994 through 1997 by testing their susceptibilities to fluconazole, ketoconazole, and miconazole and compared the results to the rate of fluconazole use. All isolates recovered prior to 1993 were susceptible to fluconazole. Within 3 years of widespread azole use, we detected resistance to all agents in this class. In order to assess the current prevalence of resistant isolates in our hematologic malignancy and transplant patients, we obtained rectal swabs from hospitalized, non-AIDS, immunocompromised patients between June 1995 and January 1996. The swabs were inoculated onto sheep's blood agar plates containing 10 microg of vancomycin and 20 microg of gentamicin/ml of agar. One hundred one yeasts were recovered from 97 patients and were tested for their susceptibilities to amphotericin B, fluconazole, flucytosine, ketoconazole, and miconazole. The susceptibility pattern was then compared to those for all clinical isolates obtained throughout the medical center. The antifungal drug histories for each patient were also assessed. The yeasts from this surveillance study were at least as susceptible as the overall hospital strains. There did not appear to be a direct linkage between prior receipt of antifungal agent therapy and carriage of a new, drug-resistant isolate. Increased resistance to newer antifungal agents has occurred at our medical center, but it is not focal to any high-risk patient population that we studied. Monitoring of susceptibility to antifungal agents appears to be necessary for optimizing clinical therapeutic decision making.

Use of in-house studies of molecular epidemiology and full species identification for controlling spread of vancomycin-resistant Enterococcus faecalis isolates.

Infection with multidrug-resistant (MDR) organisms is a major clinical challenge, and few, if any, therapeutic options remain available. Increasingly, infection control measures have taken on greater importance in preventing the nosocomial transmission of MDR organisms. During December 1994 and January 1995, we identified a cluster of vancomycin-resistant Enterococcus faecalis isolates involving 16 patients situated in different areas of our university-affiliated teaching hospital. Initial review of laboratory requisition forms for the patients' locations revealed no common association, suggesting that the occurrence was not due to horizontal spread. However, using genomic DNA extraction, restriction enzyme analysis, and gel electrophoresis, we found that 12 patients were infected with isolates originating from a single clone, 2 other patients were infected with isolates from a different clone, and the remaining 2 patients were infected with unique strains. Because the typing data suggested nosocomial spread, chart review was undertaken to determine a possible common exposure source. With three exceptions, clonal isolates were linked to patient movement between surgical floors, intensive care units, and a rehabilitation unit. A detailed review of patient records revealing the association would not have been performed without realization of clonality. Thus, the data demonstrate the utility of genomic typing for epidemiological purposes. In turn, targeted infection control measures that halted the spread of the potentially lethal MDR pathogen were instituted.