Sonia M. Aguero

Outbreak of Acinetobacter spp. bloodstream infections in a nursery associated with contaminated aerosols and air conditioners.

BACKGROUND Acinetobacter spp. are multidrug-resistant bacteria that grow well in water and cause infections with unexplained, increased summer prevalence. In August, 1996, eight infants acquired Acinetobacter spp. bloodstream infection (A-BSI) while in a nursery in the Bahamas; three infants died and an investigation was initiated. METHODS A case patient was defined as any newborn in the nursery during August 6 to 13, 1996, with A-BSI. To identify risk factors for A-BSI we conducted a retrospective cohort study and performed environmental cultures and air sampling using settle plates. The genetic relatedness of environmental isolates was assessed by pulsed field gel electrophoresis. RESULTS Of 33 patients in the nursery 8 (24%) met the case definition. Patients with peripheral iv catheters were more likely to develop A-BSI (8 of 21 vs. O of 10, P < 0.05). Multivariate analysis among patients with iv catheters indicated that only exposure to one nurse was an independent risk factor for developing A-BSI (P < 0.005). Nursery settle plates were more likely to grow Acinetobacter spp. than were settle plates from other hospital areas (8 of 9 vs. 0 of 5, P < 0.005); cultures from nursery air conditioners also grew Acinetobacter spp. Environmental isolates were genetically diverse. After installation of a new air conditioner in May, 1995, A-BSIs occurred more frequently during months of increased absolute humidity or environmental dew point. CONCLUSIONS Acinetobacter spp. may cause nosocomial BSI and death among infants during periods of polyclonal airborne dissemination; breaks in aseptic technique during i.v. medication administration may facilitate transmission from the environment to the patient. Environmental conditions that increase air conditioner condensate may predispose to airborne dissemination via contaminated aerosols and increase the risk of nosocomial A-BSI.

Serratia marcescens outbreak associated with extrinsic contamination of 1% chlorxylenol soap.

OBJECTIVES 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. DESIGN Retrospective case-control study; review of NICU infection control policies, soap use, and handwashing practices among healthcare workers (HCWs); and selected environmental cultures. SETTING A university-affiliated tertiary-care hospital NICU. PATIENTS 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. RESULTS 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. CONCLUSIONS 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.

Candida parapsilosis bloodstream infections in neonatal intensive care unit patients : epidemiologic and laboratory confirmation of a common source outbreak

BACKGROUND Candida parapsilosis is a common cause of sporadic and epidemic infections in neonatal intensive care units (NICUs). When a cluster of C. parapsilosis bloodstream infections occurred in NICU patients in a hospital in Louisiana, it provided us with the opportunity to conduct an epidemiologic investigation and to apply newly developed molecular typing techniques. METHODS A case-patient was defined as any NICU patient at Louisiana State University Medical Center, University Hospital, with a blood culture positive for C. parapsilosis during July 20 to 27, 1991. To identify risk factors for C. parapsilosis bloodstream infection, a cohort study of all NICU infants admitted during July 17 to 27, 1991, was performed. Electrophoretic karyotyping was used to assess the relatedness of C. parapsilosis isolates. RESULTS The receipt of liquid glycerin given as a suppository was identified as a risk factor (relative risk, 31.2; 95% confidence intervals, 4.3 to 226.8). Glycerin was supplied to the NICU in a 16-oz multidose bottle. Bottles used at the time of the outbreak were not available for culture. All six available isolates from four case-patients had identical chromosomal banding patterns; six University Hospital non-outbreak isolates had different banding patterns. CONCLUSIONS This study demonstrates the utility of combined epidemiologic and laboratory techniques in identifying a novel common source for a C. parapsilosis bloodstream infection outbreak and illustrates that extreme caution should be exercised when using multidose medications in more than one patient.

Microbial Growth and Endotoxin Production in the Intravenous Anesthetic Propofol

OBJECTIVE In this study, we measured microbial growth and endotoxin production in the intravenous anesthetic propofol using 10 different microbial strains; 6 isolated from outbreak cases and 4 from laboratory stock cultures. DESIGN In each trial, endotoxin-free glass tubes containing 10 ml propofol were inoculated with 10(0)-10(3) CFU/ml of the test organism and incubated at 30 degrees C for 72 hours. SETTING In May and June 1990, the Centers for Disease Control received reports of 5 outbreaks in 5 states of postsurgical patient infections and/or pyrogenic reactions. Epidemiologic and laboratory investigations implicated extrinsic contamination of an intravenous anesthetic, propofol, as the probable source of these outbreaks. RESULTS After 24 hours, 9 of the 10 cultures increased in viable counts by 3 to 6 logs. At least 1 ng/ml of endotoxin was produced within 24 hours by Escherichia coli, Enterobacter cloacae, and Acinetobacter calcoaceticus subspecies anitratus. CONCLUSIONS Propofol can support rapid microbial growth and endotoxin production. To avoid infectious complications, scrupulous aseptic technique should be used when preparing or administering this anesthetic.

Enterobacter cloacae and Pseudomonas aeruginosa polymicrobial bloodstream infections traced to extrinsic contamination of a dextrose multidose vial

OBJECTIVE To identify risk factors for polymicrobial bloodstream infections (BSIs) in neonatal intensive care unit (NICU) patients during an outbreak of BSIs. DESIGN During an outbreak of BSIs, we conducted a retrospective cohort study, assessed NICU infection control practices and patient exposure to NICU healthcare workers (HCWs), and obtained cultures of the environment and HCW hands. PATIENTS During the period May 3 to 7, 1996, 5 infants contracted BSIs caused by both Enterobacter cloacae and Pseudomonas aeruginosa, and one infant contracted a BSI caused by E cloacae only. For each pathogen, all isolates were identical on DNA typing. RESULTS Infants exposed to the following were more likely than nonexposed infants to have BSI: umbilical venous catheters (6/14 vs 0/7, P = .05), total parenteral nutrition given simultaneously with a dextrose/electrolyte solution (6/12 vs 0/9, P = .02), or one HCW (5/7 vs 1/13, P = .007). Neither environmental nor HCW hand cultures yielded the outbreak pathogens. Quality control cultures of intravenous solution bags were negative. CONCLUSIONS We speculate that a dextrose multidose vial became contaminated during manipulation or needle puncture and that successive use of this contaminated vial for multiple patients may have been responsible for BSIs. Aseptic techniques must be employed when multidose vial medications are used. Single-dose vials should be used for parenteral additives whenever possible to reduce the risk of extrinsic contamination and subsequent transmission of nosocomial pathogens.

Outbreak of Gram-Negative Bacteremia and Pyrogenic Reactions in a Hemodialysis Center

During the period from April 4, 1988, to April 20, 1988, nine pyrogenic reactions and five gram-negative bacteremias occurred in 11 patients undergoing dialysis. All pyrogenic reactions and gram-negative bacteremias occurred among patients in whom a reprocessed dialyzer was used. The rate of pyrogenic reactions or bacteremias per 100 sessions using a reprocessed dialyzer was higher than in sessions during which a new dialyzer was used (4.5 vs. 0; p = 0.03). Dialyzers were manually reprocessed with 2.5% Renalin germicide. The Renalin concentrations varied widely in 12 dialyzers stored after manual reprocessing during the epidemic period (0.9-4.2%); the median endotoxin concentrations varied from 0 to 246 ng/ml and were higher in dialyzers with Renalin concentrations less than or equal to 1.0% than in dialyzers with higher concentrations (p = 0.01). Experiments using a dilution technique described by a technician resulted in Renalin concentrations ranging from 1.4% at the surface to 3.5% at the bottom of the preparation container. These findings suggest that failure to adequately admix Renalin during dilution may be associated with low levels of disinfectant, high levels of bacteria and endotoxins in dialyzers, and outbreaks of pyrogenic reactions and gram-negative bacteremias in dialysis patients.

An Outbreak of Enterobacter hormaechei Infection and Colonization in an Intensive Care Nursery

Enterobacter hormaechei was first identified as a unique species in 1989. Between 29 November 1992 and 17 March 1993, an outbreak of E. hormaechei occurred among premature infants in the intensive care nursery (ICN) at The Hospital of the University of Pennsylvania. The 10 infants whose cultures were positive for E. hormaechei (six were infected and four were colonized) had a lower median estimated gestational age and birth weight than did other ICN infants; other risk factors for infection or colonization with E. hormaechei were not identified. Cultures from three isolettes and a doorknob in the ICN were positive for E. hormaechei. Pulsed-field gel electrophoresis of isolates from six patients and two isolettes were identical. Observations of health care workers revealed breaks in infection control techniques that may have allowed transmission of this organism. We found that E. hormaechei is a nosocomial pathogen that can infect vulnerable hospitalized patients and that can be transmitted from patient to patient when infection control techniques are inadequate.