To describe the results of a simulation study of the spread of pandemic influenza, the effects of public health measures on the simulated pandemic, and the resultant adequacy of the surge capacity of the hospital infrastructure and to investigate the adequacy of key elements of the national pandemic influenza plan to reduce the overall attack rate so that surge capacity would not be overwhelmed.

We used 2 discrete-event simulation models: the first model simulates the contact and disease transmission process, as affected by public health interventions, to produce a stream of arriving patients, and the second model simulates the diagnosis and treatment process and determines patient outcomes.

Hypothetical scenarios were based on the response plans, infrastructure, and demographic data of the population of San Antonio, Texas.

Use of a mix of strategies, including social distancing, antiviral medications, and targeted vaccination, may limit the overall attack rate so that demand for care would not exceed the capacity of the infrastructure. Additional simulations to assess social distancing as a sole mitigation strategy suggest that a reduction of infectious community contacts to half of normal levels would have to occur within approximately 7 days.

Under ideal conditions, the mix of strategies may limit demand, which can then be met by community surge capacity. Given inadequate supplies of vaccines and antiviral medications, aggressive social distancing alone might allow for the control of a local epidemic without reliance on outside support.

To determine whether hydrogen peroxide vapor (HPV) decontamination can reduce environmental contamination with and nosocomial transmission of Clostridium difficile.

A prospective before-after intervention study.

A hospital affected by an epidemic strain of C. difficile.

Intensive HPV decontamination of 5 high-incidence wards followed by hospital-wide decontamination of rooms vacated by patients with C. difficile-associated disease (CDAD). The preintervention period was June 2004 through March 2005, and the intervention period was June 2005 through March 2006.

Eleven (25.6%) of 43 cultures of samples collected by sponge from surfaces before HPV decontamination yielded C. difficile, compared with 0 of 37 cultures of samples obtained after HPV decontamination (P < .001). On 5 high-incidence wards, the incidence of nosocomial CDAD was significantly lower during the intervention period than during the preintervention period (1.28 vs 2.28 cases per 1,000 patient-days; P = .047). The hospital-wide CDAD incidence was lower during the intervention period than during the preintervention period (0.84 vs 1.36 cases per 1,000 patient-days; P = .26). In an analysis limited to months in which the epidemic strain was present during both the preintervention and the intervention periods, CDAD incidence was significandy lower during the intervention period than during the preintervention period (0.88 vs 1.89 cases per 1,000 patient-days; P = .047).

HPV decontamination was efficacious in eradicating C. difficile from contaminated surfaces. Further studies of the impact of HPV decontamination on nosocomial transmission of C. difficile are warranted.

The risk of percutaneous blood and body fluid (BBF) exposures in operating rooms was analyzed with regard to various properties of surgical procedures.

Retrospective cohort study.

A single university hospital.

All surgical procedures performed during the period 2001–2002 (n = 60,583) were included in the analysis. Administrative data were linked to allow examination of 389 BBF exposures. Stratified exposure rates were calculated; Poisson regression was used to analyze risk factors. Risk of percutaneous BBF exposure was examined separately for events involving suture needles and events involving other device types.

Operating room personnel reported 6.4 BBF exposures per 1,000 surgical procedures (2.6 exposures per 1,000 surgical hours). Exposure rates increased with an increase in estimated blood loss (17.5 exposures per 1,000 procedures with 501–1,000 cc blood loss and 22.5 exposures per 1,000 procedures with >1,000 cc blood loss), increased number of personnel ever working in the surgical field (20.5 exposures per 1,000 procedures with 15 or more personnel ever in the field), and increased surgical procedure duration (13.7 exposures per 1,000 procedures that lasted 4–6 hours, 24.0 exposures per 1,000 procedures that lasted 6 hours or more). Associations were generally stronger for suture needle–related exposures.

Our results support the need for prevention programs that are targeted to mitigate the risks for BBF exposure posed by high blood loss during surgery (eg, use of blunt suture needles and a neutral zone for passing surgical equipment) and prolonged duration of surgery (eg, double gloving to defend against the risk of glove perforation associated with long surgery). Further investigation is needed to understand the risks posed by lengthy surgical procedures.

To determine which antibiotics increase or decrease the risk of Clostridium difficile-associated diarrhea (CDAD).

Retrospective case-control study.

Nonprofit, integrated healthcare delivery system in Northern California.

Study participants included patients with cases of hospital-acquired CDAD that occurred during the period from 1999 through 2005 (n = 1,142) and control patients (n = 3,351) matched for facility, calendar quarter during which hospitalization occurred, diagnosis related group for the index hospitalization, and length of hospital stay. All case and control patients had received antibiotics in the 60 days before the index date. For each antibiotic, the risk of CDAD was examined in relation to whether the patient received the antibiotic, after adjustment for use of other antibiotics, demographic characteristics, selected health conditions, and use of healthcare services.

The following antibiotics were associated with a significantly increased risk of acquiring CDAD: imipenem-cilastin (odds ratio [OR], 2.77), clindamycin (OR, 2.31), cefuroxime (OR, 2.16), moxifloxacin (OR, 1.88), ceftazidime (OR, 1.82), cefpodoxime (OR, 1.58), ceftizoxime (OR, 1.57), and ceftriaxone (OR, 1.49). Metronidazole and doxycycline were associated with a significantly reduced risk of CDAD (OR for metronidazole, 0.67; OR for doxycycline, 0.41). Other factors associated with an increased risk of CDAD were older age, longer hospital stays, use of proton pump inhibitors, prior gastrointestinal disease, and prior infection (not including C. difficile infection.)

Some antibiotics appear to increase the risk of acquiring CDAD, notably clindamycin, third-generation cephalosporins, and carbapenems, whereas metronidazole and doxycycline appear to be protective, compared with other antibiotics.

To describe an outbreak of extended-spectrum β-lactamase (ESBL)–producing Klebsiella pneumoniae in the intensive care units (ICUs) of a hospital and the impact of routine and reinforced infection control measures on interrupting nosocomial transmission.

Outbreak report.

A 31-bed intensive care department (composed of 4 ICUs) in a university hospital in Belgium.

After routine infection control measures (based on biweekly surveillance cultures and contact precautions) failed to interrupt a 2-month outbreak of ESBL-producing K. pneumoniae, reinforced infection control measures were implemented. The frequency of surveillance cultures was increased to daily sampling. Colonized patients were moved to a dedicated 6-bed ICU, where they received cohorted care with the support of additional nurses. Two beds were closed to new admissions in the intensive care department. Meetings between the ICU and infection control teams were held every day. Postdischarge disinfection of rooms was enforced. Broad-spectrum antibiotic use was discouraged.

Compared with a baseline rate of 0.44 cases per 1,000 patient-days for nosocomial transmission, the incidence peaked at 11.57 cases per 1,000 patient-days (October and November 2005; rate ratio for peak vs baseline, 25.46). The outbreak involved 30 patients, of whom 9 developed an infection. Bacterial genotyping disclosed that the outbreak was polyclonal, with 1 predominant genotype. Reinforced infection control measures lasted for 50 days. After the implementation of these measures, the incidence fell to 0.08 cases per 1,000 patient-days (rate ratio for after the outbreak vs during the outbreak, 0.11).

These data indicate that, in an intensive care department in which routine screening and contact precautions failed to prevent and interrupt an outbreak of ESBL-producing K. pneumoniae, reinforced infection control measures controlled the outbreak without major disruption of medical care.

To characterize infection control experience during a 6.5-year period in a cooperative care center for transplant patients.

Descriptive analysis.

A cooperative care center for transplanted patients, in which patients and care partners are housed in a homelike environment, and care partners assume responsibility for patient care duties.

Nine hundred ninety one transplant patients.

Infection control definitions from the Centers for Disease Control and Prevention were used to ascertain infection rates. Environmental cultures were used to detect methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), Clostridium difficile, and fungi during the first 18 months. Surveillance cultures were performed for a subset of patients and care partners.

From June 1999 through December 2005, there were 19,365 patient-days observed. The most common healthcare-associated infection encountered was intravascular catheter-related bloodstream infection, with infection rates of 5.74 and 4.94 cases per 1,000 patient-days for hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) patients, respectively. G difficile-associated diarrhea was observed more frequentiy in HSCT patients than in SOT patients (3.97 vs 0.57 cases per 1000 patient-days; P< .0001 ). There was no evidence of environmental contamination with MRSA, VRE, or C. difficile. Acquisition of MRSA was not observed. Acquisition of VRE was documented.

This study documented that cooperative care was associated with some risk of healthcare-associated infection, most notably intravascular catheter-associated bloodstream infection and C. difficile-associated diarrhea, it appears the incidences of these infections were roughly commensurate with those in other care settings.

To better define the pathogenesis of catheter-related bloodstream infection (BSI) in neonates with peripherally inserted central venous catheters (PICCs) to guide the development of more effective strategies for prevention.

Prospective nested cohort study.

Level III neonatal intensive care unit in a community hospital.

During a randomized trial to assess the safety and efficacy of a prophylactic vancomycin-heparin catheter-lock solution for the prevention of catheter-related BSI in neonates with PICCs, we performed cultures of peripheral and catheter-drawn blood samples, and quantitative cultures of catheter hub samples if BSI was suspected clinically. We performed semiquantitative cultures of the catheter tip and the catheter hub and the skin at the insertion site when the catheter was removed. Molecular subtyping by pulsed-field electrophoresis was used to determine the probable pathogenesis of all BSIs due to coagulase-negative staphylococci (CoNS); for BSIs caused by other microorganisms, epidemiologic concordance was based on speciation and antibiograms. Catheter-related BSI was considered extraluminally acquired if concordance was demonstrable solely between isolates recovered from the catheter tip and the blood, independent of concordance with isolates recovered from the insertion site. Catheter-related BSI was considered intraluminally acquired if concordance was demonstrated only between isolates recovered from the catheter hub and the blood. The source of the infection was considered indeterminate if both concordance patterns were present.

Nosocomial BSI was identified in 23 of the 82 neonates in the cohort. Fifteen of these infections, 14 of which were caused by CoNS, were considered definite or probable catheter-related BSIs. Catheter-related BSI was intraluminally acquired in 10 (67%) of 15 patients, extraluminally acquired in 3 (20%), and indeterminate in 2 (13%).

Most catheter-related BSIs in neonates with PICCs are caused by CoNS and derive from intraluminal contamination. Strategies for prevention of catheter-related BSI directed at this predominant mechanism of infection are most likely to be effective.

To quantify the economic burden of in-hospital surgical site infections (SSIs) at a European university hospital.

Matched case-control study nested in a prospective observational cohort study.

Basel University Hospital in Switzerland, where an average of 28,000 surgical procedures are performed per year.

All in-hospital occurrences of SSI associated with surgeries performed between January 1, 2000, and December 31, 2001, by the visceral, vascular, and traumatology divisions at Basel University Hospital were prospectively recorded. Each case patient was matched to a control patient by age, procedure code, and National Nosocomial Infection Surveillance System risk index. The case-control pairs were analyzed for differences in cost of hospital care and in provision of specialized care.

A total of 6,283 procedures were performed:187 SSIs were detected in inpatients, 168 of whom were successfully matched with a control patient. For case patients, the mean additional hospital cost was SwF19,638 (95% confidence interval [CI], SwF8,492–SwF30,784); the mean additional postoperative length of hospital stay was 16.8 days (95% CI, 13–20.6 days); and the mean additional in-hospital duration of antibiotic therapy was 7.4 days (95% CI, 5.1–9.6 days). Differences were primarily attributable to organ space SSIs (n = 76).

Ina European university hospital setting, SSIs are costly and constitute a heavy and potentially preventable burden on both patients and healthcare providers.

Severity of illness is an important confounder in outcome studies involving infectious diseases. However, it is unclear whether the time at which severity of illness is measured is important.

We performed a retrospective study of 328 episodes of gram-negative bacteremia in adult patients to assess the impact of the time of measurement of severity of illness on the association between empirical antimicrobial therapy received and in-hospital mortality. Using a modified Acute Physiology Score (APS), severity of illness was measured at 2 time points: (1) hospital admission and (2) 24 hours before the first culture-positive blood sample was collected. Multivariate logistic regression was used to estimate the impact of adjusting for the APS on the relationship between empirical therapy received (ie, the exposure) and in-hospital mortality (ie, the outcome).

The mean APS ( ± standard deviation) of patients with bacteremia increased during their hospital stay (from 19.2 ± 11.6 at admission to 24.2 ± 13.6 at the second time point; P < .01). When examining the association between empirical antimicrobial therapy received and in-hospital mortality, and controlling for the APS, there was a trend toward a decreased impact of appropriate therapy received on in-hospital mortality. The unadjusted odds ratio (OR) for the association between appropriate therapy received and in-hospital mortality was 0.83 (95% confidence interval [CI], 0.51-1.34). After controlling for the APS at admission, this association was attenuated (OR, 0.94 [95% CI, 0.57-1.55]), and when a change in the APS was also included in the multivariate logistic regression model, the association was further attenuated (OR, 0.99 [95% CI, 0.58-1.69]).

The magnitude of the association between appropriate antimicrobial therapy received and in-hospital mortality among patients with gram-negative bacteremia was sensitive to the timing of adjustment for severity of illness.

To determine the range and the mode of germicidal activity of sterilants generated by a nonthermal plasma sterilization system for microorganisms.

Representative bacteria, spores, viruses, bacteriophages, and fungi were exposed to the plasma cycle and the residual viability was measured in vitro. To assess the mode of lethal injury, Escherichia coli, Staphylococcus aureus, Bacillus atrophaeus, and bacteriophages were exposed to the plasma cycle, and the effects of the plasma-generated sterilants on the biological parameters were determined.

There were at least 4-6 log reductions in viability for all microorganisms after 10 minutes of exposure to the plasma cycle. Electron micrographs and studies of the inhibition of bacteriophage infectivity suggested that the primary injury is to the organisms' cell envelopes. The plasma cycle also denatured isolated bacterial proteins and inactivated bacteriophages, but it had no effect on isolated DNA and bacterial proteins within exposed bacteria.

Nonthermal plasma, which is produced at atmospheric temperature and pressure, generates sterilants that kill high concentrations of microorganisms and inactivate viruses during a 10-minute exposure. The primary injury appears to be at the surface structures of the organisms. This suggests that nonthermal plasma has utility for sterilization of heat-sensitive medical materials and devices.

To develop and evaluate computer algorithms with high negative predictive values that augment traditional surveillance for central line–associated bloodstream infection (CLABSI).

Barnes-Jewish Hospital, a 1,250-bed tertiary care academic hospital in Saint Louis, Missouri.

We evaluated all adult patients in intensive care units who had blood samples collected during the period from July 1, 2005, to June 30,2006, that were positive for a recognized pathogen on culture. Each isolate recovered from culture was evaluated using the definitions for nosocomial CLABSI provided by the National Healthcare Safety Network of the Centers for Disease Control and Prevention. Using manual surveillance by infection prevention specialists as the gold standard, we assessed the ability of various combinations of dichotomous rules to determine whether an isolate was associated with a CLABSI. Sensitivity, specificity, and predictive values were calculated.

Infection prevention specialists identified 67 cases of CLABSI associated with 771 isolates recovered from blood samples. The algorithms excluded approximately 40%-62% of the isolates from consideration as possible causes of CLABSI. The simplest algorithm, with 2 dichotomous rules (ie, the collection of blood samples more than 48 hours after admission and the presence of a central venous catheter within 48 hours before collection of blood samples), had the highest negative predictive value (99.4%) and the lowest specificity (44.2%) for CLABSI. Augmentation of this algorithm with rules for common skin contaminants confirmed by another positive blood culture result yielded in a negative predictive value of 99.2% and a specificity of 68.0%.

An automated approach to surveillance for CLABSI that is characterized by a high negative predictive value can accurately identify and exclude positive culture results not representing CLABSI from further manual surveillance.

To investigate the epidemiology of multidrug-resistant Enterobacteriaceae (MDRE) in hospitalized infants.

From 2000 through 2005, active surveillance cultures for MDRE were performed for patients admitted to a 40-bed neonatal intensive care unit (NICU) that provides care for critically ill infants 6 months of age or younger. MDRE epidemiology and the genetic relatedness of MDRE strains determined by repetitive-sequence polymerase chain reaction were analyzed.

Active surveillance cultures revealed that 759 (23%) of 3,370 NICU infants (or approximately 1 in 5) developed MDRE colonization or infection and that 613 (72%) of the 853 isolates with epidemiologic data available were healthcare acquired. MDRE colonization occurred more frequently (in 653 infants [86%]) than did MDRE infection (in 106 [14%]). Of the 653 infants with MDRE colonization, 119 (18%) eventually became infected, with 29 (4%) acquiring sterile site infections. The most commonly isolated organisms were the Enterobacter species, accounting for 612 (71%) of the 862 isolates. Molecular epidemiologic analysis revealed that genetic-relatedness clustering (related clusters defined as having a genetic similarity coefficient greater than 95%) varied depending on microbial species. Clustering was detected for 36 (78%) of the 46 Enterobacter aerogenes isolates, 22 (45%) of the 49 Enterobacter cloacae isolates, and 13 (59%) of the 22 Klebsiella pneumoniae isolates.

Hospitalized infants are at significant risk of acquiring MDRE, specifically Enterobacter species, at the study institution. Active surveillance cultures identified colonized patients who likely contributed to the institutional reservoir of MDRE. Molecular epidemiologic studies suggest that both patient-to-patient transmission and de novo acquisition of resistance play a role in the acquisition of these organisms, and that the clinical significance of such acquisition varies by species. The high percentage of E. aerogenes isolates that demonstrated genetic clustering suggests that monitoring the prevalence of this organism could serve as a useful measure of compliance with infection control procedures.

To establish whether antibiotic prophylaxis against group B streptococcal infection may be a confounding factor in comparisons of rates of endometritis and urinary tract infection after vaginal delivery.

Prospective study.

Maternity units at 48 hospitals in a regional surveillance network in France during 2001-2004.

The maternity units used a common protocol to establish whether antibiotic prophylaxis was indicated. Risk factors for endometritis and urinary tract infections were evaluated using multiple logistic regression.

We analyzed 49,786 vaginal deliveries. The percentage of women receiving antibiotic prophylaxis varied widely and significantly among the maternity units (range, 4.4%-26.0%; median, 15.8%; 25th percentile, 12.1%; 75th percentile, 19.0%) (P < .001, by Mantel-Haenszel χ2 test). The incidence rate of endometritis was significantly reduced from 0.25% to 0.11% by antibiotic prophylaxis (P = .001). There was a decrease in the incidence of urinary tract infection from 0.37% to 0.32%, but it was not statistically significant (P = .251).

A reduction in the incidence of endometritis was observed when intrapartum antibiotic prophylaxis against group B streptococcal infection was used. However, the proportion of women considered to be at risk of infection varied widely among institutions. Comparisons of rates of endometritis among maternity units, but not urinary tract infection rates, should take into account antibiotic prophylaxis as a significant confounding factor.

Respiratory protection programs, including fit testing of respirators, have been inconsistently implemented; evidence of their long-term efficacy is lacking. We undertook a study to determine the short- and long-term efficacy of training for fit testing of N95 respirators in both untrained and trained healthcare workers (HCWs).

Prospective observational cohort study.

A group of at-risk, consenting HCWs not previously fit-tested for a respirator were provided with a standard fit-test protocol. Participants were evaluated after each of 3 phases, and 3 and 14 months afterward. A second group of previously fit-tested nurses was studied to assess the impact of regular respirator use on performance.

Of 43 untrained fit-tested HCWs followed for 14 months, 19 (44.2%) passed the initial fit test without having any specific instruction on respirator donning technique. After the initial test, subsequent instruction led to a pass for another 13 (30.2%) of the 43 HCWs, using their original respirators. The remainder required trying other types of respirators to acheive a proper fit. At 3 and 14 months' follow-up, failure rates of 53.5% (23 of 43 HCWs) and 34.9% (15 of 43 HCWs), respectively, were observed. Pass rates of 87.5%-100.0% were observed among regular users.

Without any instruction, nearly 50% of the HCWs achieved an adequate facial seal with the most commonly used N95 respirator. Formal fit testing does not predict future adequacy of fit, unless frequent, routine use is made of the respirator. The utility of fit testing among infrequent users of N95 respirators is questionable.

To evaluate hand hygiene compliance in 2 adult step-down units (SDUs).

A 6-month (from March to September 2007), controlled trial comparing 2 SDUs, one with a feedback intervention program (ie, the intervention unit) and one without (ie, the control unit).

Two 20-bed SDUs at a tertiary care private hospital.

Hand hygiene episodes were measured by electronic recording devices and periodic observational surveys. In the intervention unit, feedback was provided by the SDU nurse manager, who explained twice a week to the healthcare workers the goals and targets for the process measures.

A total of 117,579 hand hygiene episodes were recorded in the intervention unit, and a total of 110,718 were recorded in the control unit (P = .63). There was no significant difference in the amount of chlorhexidine used in the intervention and control units (34.0 vs 26.7 L per 1,000 patient-days; P = .36) or the amount of alcohol gel used (72.5 vs 70.7 L per 1,000 patient-days; P = .93). However, in both units, healthcare workers used alcohol gel more frequently than chlorhexidine (143.2 vs 60.7 L per 1,000 patient-days; P < .001). Nosocomial infection rates in the intervention and control units, respectively, were as follows: for bloodstream infection, 3.5 and 0.79 infections per 1,000 catheter-days (P = .18); for urinary tract infection, 15.8 and 15.7 infections per 1,000 catheter-days (P = .99); and for tracheostomy-associated pneumonia, 10.7 and 5.1 infections per 1,000 device-days (P = . 13). There were no cases of infection with vancomycin-resistant enterococci and only a single case of infection with methicillin-resistant Staphylococcus aureus (in the control unit).

The feedback intervention regarding hand hygiene had no significant effect on the rate of compliance. Other measures must be used to increase and sustain the rate of hand hygiene compliance.