To compare the ability of the Study of the Efficacy of Nosocomial Infection Control (SENIC) and the National Nosocomial Infection Surveillance (NNIS) indices to predict the development of nosocomial sepsis in subjects undergoing surgery.

1-year prospective case-control study.

A tertiary-care center in Spain.

Cases were surgical patients with nosocomial sepsis defined using the criteria of the Consensus Conference on Sepsis, identified by daily prospective surveillance.

Controls were randomly selected from the daily list of surgical inpatients. Data were prospectively collected. To determine whether either index added explanatory information to the other, two methods were used. The first method involved computing a set of residuals for both variables. Residuals and primary variables were introduced in logistic regression models. The second method evaluated both indices with the Goodman-Kruskal (G) nonparametric coefficient.

99 cases and 97 controls were included. After controlling for confounders, both the SENIC index (P<.001) and the NNIS index (P=.04) showed a significant trend. Residuals of the SENIC index added discriminating ability to the NNIS index, whereas residuals of the NNIS index did not improve the prediction ability of the SENIC index. Similar results were yielded by the G statistic: the SENIC index showed higher predictive power than the NNIS index (G=0.56 vs G=0.41).

Both indices performed about equally well for discriminating risk of nosocomial sepsis. The SENIC index had a somewhat better ability than the NNIS index only when the number of discharge diagnoses (not truly a predictive factor) were involved in the calculation of the SENIC index.

To determine the role of nonmedicated soap as a source of Serratia marcescens nosocomial infections (NIs) in hospital units with endemic S marcescens NI and to examine the mechanisms of soap colonization.

University-affiliated tertiary-care hospitals.

A prospective case-control study and an environmental investigation were performed to assess the relationship between S marcescens NIs in hospital units and S marcescens-contaminated soap. Soap-bottle use and handwashing practices were reviewed. Cultures of healthcare workers’ (HCWs) hands were obtained before and after hand washing with soap.

5 of 7 hospital units with S marcescens NIs had soap bottles contaminated with S marcescens, compared to 1 of 14 other units (P =.006). After hand washing with an S marcescens-contaminated soap pump, HCWs' hands were 54 times more likely to be contaminated with S marcescens (P<.001).

Extrinsic contamination of a non-medicated liquid soap by S marcescens resulted in handborne transmission of S marcescens NIs by HCWs in our setting. This finding led to the application of strict guidelines for nonmedicated soap use and to the reinforcement of alcoholic hand disinfection.

To identify risk factors associated with an unexpected outbreak of pyrogenic reactions (PR) following intravenous gentamicin.

We conducted two cohort studies. PRs were defined as chills, rigors, or shaking within 3 hours after initiating the gentamicin infusion during the preepidemic (December 1, 1997-January 15,1998) or epidemic (May 1-June 15,1998) periods. We tested gentamicin vials for endotoxin using the limulus amebocyte lysate assay.

Inpatient services of a large community hospital in Los Angeles, California.

During the epidemic period, 22 (15%) of 152 patients developed documented PRs following intravenous gentamicin. PRs were more likely among patients receiving single daily dosing (SDD) than multiple daily dosing gentamicin (20/73 [27%] vs 2/79 [3%]; relative risk, 10.8; 95% confidence interval, 2.644.7). Laboratory analysis of gentamicin vials found endotoxin levels that were higher among Fujisawa-brand gentamicin (implicated brand) than gentamicin used after the outbreak terminated (non-implicated brand). Although endotoxin levels in the vials did not exceed US Pharmacopeia limits (1.7 endotoxin units/mg gentamicin), the use of SDD gentamicin may place patients at greater risk of receiving doses of endotoxin above the threshold for PRs in humans.

Reassessment of the acceptable amounts of endotoxin in gentamicin and other parenteral products should be considered when dosing intervals used in clinical practice change.

To study the association of antibiotic-utilization measures and control of multidrug-resistant (MDR) Klebsiella pneumoniae after emergence in two hospitals in our medical center.

Rates of MDR K pneumoniae at two hospitals were compared before and after acute interventions, including emphasis on Contact Precautions and education in antibiotic utilization. Antipseudomonal β-lactam antibiotic use was measured before and after the interventions at both hospitals. Pulsed-field gel electrophoresis of whole cell DNA was used as a marker of strain identity.

Clonal strain dissemination was the major mechanism of emergence at hospital A; emergence was polyclonal at hospital B. Antibiotic-utilization interventions at both institutions included physician education regarding the association of ceftazidime use and MDR K pneumoniae. At hospital A, ceftazidime use decreased from 4,301 g in the preintervention period, to 1,248 g in the postintervention period. Piperacillin-tazobactam use increased from 12,455 g to 17,464 g. Ceftazidime resistance in Kpneumoniae decreased from 110 (22%) of 503 isolates to 61 (15%) of 407 isolates (P<.05); piperacillin-tazobactam resistance decreased from 181 (36%) of 503 to 77 (19%) of 407 isolates (P<.05). At hospital B, ceftazidime use decreased from 6,533 g in the preintervention period to 4,792 g in the postintervention period. Piperacillin-tazobactam use increased from 58,691 g to 67,027 g. Ceftazidime resistance in K pneumoniae decreased from 42 (10%) of 415 isolates to 19 (5%) of 383 isolates (P<.05). Piperacillin-tazobactam resistance decreased from 91 (22%) of 415 isolates to 54 (14%) of 383 isolates (P<.05). Follow-up data showed continued decrease in piperacillin-tazobactam resistance despite increased use at both hospitals.

Antibiotic-use measures may be particularly important for control of MDR K pneumoniae, whether emergence is clonal or polyclonal.

To determine the roles of “colonization pressure,” work load or patient severity in patient acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in intensive care units (ICUs).

Prospectively collected data from October 1996 through December 1998.

A 12-bed medical ICU in a university-affiliated general hospital.

Patients with risk factors for MRSA admitted to the ICU were screened within 72 hours of admission and weekly thereafter. MRSA was considered imported if detected during the first 72 hours of admission and nosocomial if detected only thereafter. Three screening strategies were used on admission during three consecutive periods.

The unit of time chosen for measurements was the week. Weekly colonization pressure (WCP) was defined as the number of MRSA-carrier patient-days/total number of patient-days. Patient severity (number of deaths, Simplified Acute Physiologic Score [SAPS] II), work load (number of admissions. Omega score), and colonization pressure (number of MRSA carriers at the time of admission, WCP) were compared with the number of MRSA-nosocomial cases during the following week.

Of the 1,016 patients admitted over 116 weeks, 691 (68%) were screened. MRSA was imported in 91 (8.9%) admitted patients (13.1% of screened patients) and nosocomial in 46 (4.5%). The number of MRSA-nosocomial cases was correlated to the SAPS II (P=.007), the Omega 3 score (P=.007), the number of MRSA-imported cases (P=.01), WCP (P<.0001), and the screening period (P<.0001). In multivariate analysis, WCP was the only independent predictive factor for MRSA acquisition (P=.0002). Above 30% of WCP, the risk of acquisition of MRSA was approximately fivefold times higher (relative risk, 4.9;95% confidence interval, 1.2-19.9; P<.0001).

Acquisition of MRSA in ICU patients is strongly and independently influenced by colonization pressure.

To evaluate the efficacy of a multistep cleaning method using a cleaner and a chemical disinfectant on blood-contaminated angiographic catheters and spinal needles intended to be sterilized by hydrogen peroxide gas plasma.

A mixture of radiopaque iodine contrast, bovine blood (plus ethylenediaminetetraacetic acid), and a suspension of Bacillus subtilis spores was used to simulate catheterization and needle use. The mixture was a 1:1 proportion of contrast and blood, inoculated so that there was a final concentration of B subtilis spores of 1.0×106 colony-forming units (CFU)/mL. The inoculated devices were cleaned using a hydrogen peroxide solution at a concentration of 1.5±0.5 percent by weight, followed by distilled water with enzymatic detergent. After drying, the devices were sterilized with hydrogen peroxide gas plasma.

The initial B subtilis spore concentration inoculated into catheters and needles varied from 2.12×104 to 2.74×107 CFU/mL. The residual load of B subtilis spores after cleaning varied from zero (no count) to a maximum of 200 CFU/device. The multistep cleaning procedure was responsible for an average 5-log10 reduction of B subtilis spores in the catheter and needle lumens.

The hydrogen peroxide and enzymatic detergent aqueous solutions were shown to be efficacious when used as part of a multistep cleaning method. The low level of microbial contamination prior to sterilization with hydrogen peroxide gas plasma assured that the intended sterility assurance level was reached.

To describe the clinical and molecular epidemiology of mupirocin-resistant (MR) and mupirocin-susceptible (MS) methicillin-resistant Staphylococcus aureus (MRSA) at a Veterans' Affairs hospital and to assess risk factors associated with the acquisition of MR MRSA.

All clinical MRSA isolates for the period October 1990 through March 1995 underwent susceptibility testing to mupirocin. Mupirocin resistance trends were measured, and MS MRSA and MR MRSA isolates underwent typing by pulsed-field gel electrophoresis (PFGE). A retrospective case-control study was conducted to evaluate risk factors for having MR versus MS MRSA.

The James H. Quillen Veterans' Affairs Medical Center in Mountain Home, Tennessee, included a 324-bed acute-care hospital, a 120-bed nursing home, and a 525-bed domiciliary. Colonizations and infections with MRSA were endemic, and mupirocin ointment was commonly used.

Inpatients and outpatients at the facility.

MS MRSA was recovered from 506 patients and MR MRSA from 126. Among MR MRSA isolates, 58% showed low-level mupirocin resistance (minimum inhibitory concentration [MIC] ≥4 to 256 μg/mL), and 42% showed high-level mupirocin resistance (MIC ≥512 μg/mL). A significant increase (P=.002) in the number of high-level MR isolates occurred during the 1993 to 1995 period. A case-control study showed that presence of a decubitus ulcer correlated with high-level resistant isolates (P<.05). The distribution of PFGE patterns did not differ for MR and MS MRSA.

Use of mupirocin ointment in a program aimed at managing endemic MRSA infection or colonization resulted in a significant increase in the recovery of high-level MR MRSA isolates. These isolates appeared to emerge from our existing MRSA pool. A case-control study provided few clues concerning patients likely to harbor MR MRSA We confirmed the position that the extended use of mupirocin ointment should be avoided in settings where MRSA is endemic.

To establish an efficient and sensitive technique for recovering vancomycin-resistant enterococci (VRE) from perianal and environmental samples collected during implementation of control measures for an outbreak of VRE.

Perianal and environmental samples were collected in triplicate on sterile swabs. One swab was used to inoculate a selective broth medium containing 6 μg of vancomycin and 8 μg of ciprofloxacin per mL, one to inoculate Campylobacter agar containing 10 μg/mL of vancomycin, and one to inoculate Enterococcosel agar containing 8 μg/mL of vancomycin.

Samples were collected in the intensive care units of a 600-bed university hospital over a period of 2 months.

Patients and their immediate environment were sampled if they resided in a ward with a patient known to be colonized or infected with VRE.

Of the 88 perianal samples obtained from 63 patients, 37 were positive for VRE by broth culture, with 36 also recovered on both types of solid media (sensitivity, 97.3%; negative predictive value, 98.1%). Of the initial samples collected from each of the 63 patients, 20 were positive for VRE by all methods. Of the 500 environmental samples cultured, 139 were positive for VRE in broth, with only 33 recovered on Campylobacter agar (sensitivity, 23.7%; negative predictive value, 77.2%) and 22 on Enterococcosel agar (sensitivity, 15.8%; negative predictive value, 75.2%).

Our data indicate that, when performing surveillance cultures during an outbreak of VRE, use of an enrichment broth medium is required to recover VRE contaminating environmental surfaces; however, direct inoculation to selective solid medium is adequate to recover VRE in patient perianal specimens.