To determine risk factors for Serratia marcescens infection or colonization, and to identify the source of the pathogen and factors facilitating its persistence in a neonatal intensive-care unit (NICU) during an outbreak.

Retrospective case-control study; review of NICU infection control policies, soap use, and hand-washing practices among healthcare workers (HCWs); and selected environmental cultures.

A university-affiliated tertiary-care hospital NICU.

All NICU infants with at least one positive culture for S marcescens during August 1994 to October 1995. Infants who did not develop S marcescens infection or colonization were selected randomly as controls.

Thirty-two patients met the case definition. On multivariate analysis, independent risk factors for S marcescens infection or colonization were having very low birth weight (<1,500 g), a patent ductus arteriosus, a mother with chorioamnionitis, or exposure to a single HCW. During January to July 1995, NICU HCWs carried their own bottles of 1% chlorxylenol soap, which often were left standing inverted in the NICU sink and work areas. Cultures of 16 (31%) of 52 samples of soap and 1 (8%) of 13 sinks yielded S marcescens. The 16 samples of soap all came from opened 4-oz bottles carried by HCWs. DNA banding patterns of case infant, HCW soap bottle, and sink isolates were identical.

Extrinsically contaminated soap contributed to an outbreak of S marcescens infection. Very-low-birth-weight infants with multiple invasive procedures and exposures to certain HCWs were at greatest risk of S marcescens infection or colonization.

To compare the epidemiology of vancomycin-resistant Enterococcus faecium (VRE) in a longterm–care unit and an acute-care hospital.

Point-prevalence surveys for VRE rectal colonization of patients were carried out over a 21-month period in patients in a long-term–care unit and an acutecare hospital (medical ward and intensive-care units). The environment and hands of healthcare workers also were sampled for VRE. Contour-clamped homogeneous electric field (CHEF) electrophoresis was used to evaluate possible transmission among roommates and the relatedness of patient strains to those in the environment and on the hands of healthcare workers.

A 200-bed Veterans Affairs Medical Center with an attached 90-bed long-term–care unit.

From December 1994 to January 1996, rectal VRE colonization of patients in the long-term–care unit increased significantly from 9% to 22%. In contrast, patients on the medical ward rarely were colonized after the first survey in December 1994, and only two intensivecare–unit patients were found to be colonized during the four surveys. The environment was contaminated persistently in the long-term–care unit. In the four surveys, carriage of VRE on hands of healthcare workers varied from 13% to 41%; 65% of healthcare workers with VRE found on their hands worked in the long-term–care unit.

Seven different strains were identified by CHEF typing. Although the initial survey found only vanA strains, subsequent surveys showed vanB strains also were present.

Residents of a long-term–care unit frequently were colonized with VRE, but infections were uncommon in this population. The environment of the long-term–care unit was contaminated with VRE, and VRE was found frequently on the hands of healthcare workers in this unit. Both vanA and vanB genotypes were found in this setting.

To describe control of endemic and outbreak-related methicillin-resistant Staphylococcus aureus (MRSA) at two affiliated hospitals.

Prospective surveillance of patients with MRSA. Disposable gloves were used by all staff having direct contact with the affected patient or his immediate environment, and patient isolates were typed by pulsedfield gel electrophoresis (PFGE) of genomic DNA. Surveillance and PFGE typing were used concurrently to identify possible nosocomial outbreaks, confirm or refute cross-infection, and support a need for additional outbreak control interventions.

A university hospital (Hospital A) and a university-affiliated public hospital (Hospital B).

Patients with MRSA colonization or infection over an 18-month interval (June 1993-November 1994).

Proper handwashing and gloving practices were reemphasized with staff following confirmation of outbreaks.

Hospital A had 60 community-acquired and 48 nosocomial cases of MRSA. Two small outbreaks (affecting a total of seven patients) and two pseudo-outbreaks were identified. Hospital B had 36 community-acquired and 22 nosocomial cases of MRSA. Only one outbreak affecting five patients occurred. All outbreaks ended shortly after staff meetings that emphasized ongoing and extremely careful handwashing and gloving when caring for identified patients. The majority of nosocomial cases at both hospitals were not related epidemiologically or had isolates with unique PFGE types. Pseudo-outbreaks were confirmed by demonstrating that isolates from epidemiologically related cases (by time and clinical service or hospital unit) had different PFGE types. Hospital A cases had 39 different PFGE types, and Hospital B cases had 31 different PFGE types.

MRSA in hospitals, including outbreaks identified by prospective surveillance and confirmed by PFGE typing, can be controlled by minimal special precautions and interventions. This is possible despite the continuous admission of patients with MRSA from the community. PFGE typing is useful to confirm outbreaks and pseudo-outbreaks, demonstrate differences among epidemiologically unrelated isolates, and substantiate the efficacy of MRSA control programs within hospitals.

To assess the efficacy of an infection control program as measured by tuberculin skin-test (TST) conversion rates in medical house staff.

Observational study.

University-based hospital in New York City serving a large indigent population.

Medical house staff.

TST conversions were measured every 6 months in medical house staff from June 1992 to June 1994. Compliance with the isolation policy was measured by identifying room locations 24 hours after admission of patients who had Mycobacterium tuberculosis recovered from respiratory specimens.

The TST conversion rate decreased from 5.8 to 0, 2.3, and 0 per 100 person years of exposure in successive 6-month periods. The estimated annual TST conversion rate among interns fell from 7 per 100 person years in June 1992 to 0 per 100 person years in June 1993 and 0 per 100 person years in June 1994 (P=.029). The proportion of patients with pulmonary tuberculosis who were isolated in negative-pressure rooms increased from 38% to 75% over the study period (P=.01).

Development of a multifaceted infection control program can decrease the risk of nosocomial tuberculosis infection in medical house staff.

To evaluate the efficacy of the AbTox Plazlyte Sterilization System against selected microbial species using inoculated carriers and surgical instruments.

The microbiology laboratory of a 700-bed adult tertiary-care hospital.

The study was conducted in two phases. In phase 1, microorganisms were inoculated to various metal, paper, plastic, and glass carriers, as well as surgical equipment, and processed in cycle II of the AbTox sterilizer. Phase 2 compared AbTox cycle III with ethylene oxide sterilization using stainless steel washers, penicylinders, and surgical equipment. In both phases, cultures of equipment and carriers were obtained after processing. The phenotypic profiles and antibiograms of positive cultures were compared to the original inoculate to rule out the possibility of contamination.

Of a total of 350 paper carriers, 375 metal washers, and 234 pieces of equipment processed in cycle II and using trypticase soy broth as the inoculating medium, 123 metal washers (32%) and 8 instruments (3%) failed to be sterilized. Similar failures were noted with cycle III. The presence of either salt or protein adversely affected the system's ability to sterilize in either cycle.

Further studies are needed to evaluate the extent to which salt or organic material compromise low-temperature gas-plasma sterilization. Meanwhile, users should exercise caution and use care in the cleaning of instruments that will be processed in the plasma-based sterilization technologies

To determine the susceptibilities of vancomycin-resistant and -sensitive enterococci (VRE and VSE) to various concentrations of commonly used, commercial, hospital-grade disinfectants.

A microbial suspension test using inocula of 108 cells per mL in a disinfectant test dilution was used to determine inactivation kinetics of the test strains. In each test, 1-mL aliquots were removed from the cell-disinfectant mixtures at 15 and 30 seconds and then at 1-minute intervals for 5 minutes and neutralized. Appropriate serial dilutions were plated on agar medium for enumeration of survivors.

VRE and VSE challenge inocula (in the absence of any additional protein or serum challenge) were below the limit of detection (5 colony-forming units/mL) after 15 seconds' exposure to the manufacturers' suggested use-dilutions of quaternary ammonium, phenolic, or iodophor germicidal detergents. In subsequent tests, when the disinfectants were diluted far beyond the recommended use-dilutions (extended dilution), no differences were demonstrated between the susceptibilities of VRE and VSE.

VRE and VSE are sensitive to a spectrum of commonly used environmental disinfectants and have parallel inactivation rates when challenged with extended dilutions of these products. Our findings did not demonstrate a relationship between antibiotic and germicide resistance. Routine disinfection and housekeeping protocols presently used in hospitals need not be altered due to concerns about the potential for environmentally mediated transmission of antibiotic-resistant microorganisms.