To identify risk factors for infection with imipenem-resistant Pseudomonas aeruginosa and determine the impact of imipenem resistance on clinical and economic outcomes among patients infected with P. aeruginosa.

An ecologic study, a case-control study, and a retrospective cohort study.

A 625-bed tertiary care medical center.

All patients who had an inpatient clinical culture positive for P. aeruginosa between January 1, 1999, and December 31, 2000.

From 1991 through 2000, the annual prevalence of imipenem resistance among P. aeruginosa isolates increased significantly (P<.001 by the χ2 test for trend). Among 879 patients infected with P. aeruginosa during 1999-2000, a total of 142 had imipenem-resistant P. aeruginosa infection (the case group), whereas 737 had imipenem-susceptible P. aeruginosa infection (the control group). The only independent risk factor for imipenem-resistant P. aeruginosa infection was prior fluoroquinolone use (adjusted odds ratio, 2.52 [95% confidence interval {CI}, 1.61-3.92]; P<.001). Compared with patients infected with imipenem-susceptible P. aeruginosa, patients infected with imipenem-resistant P. aeruginosa had longer subsequent hospitalization durations (15.5 days vs 9 days; P = .02) and greater hospital costs ($81,330 vs $48,381; P<.001). The mortality rate among patients infected with imipenem-resistant P. aeruginosa was 31.1%, compared with 16.7% for patients infected with imipenem-susceptible P. aeruginosa (relative risk, 1.86 [95% CI, 1.38-2.51]; P<.001). In multivariable analyses, there remained an independent association between infection with imipenem-resistant P. aeruginosa and mortality.

The prevalence of imipenem resistance among P. aeruginosa strains has increased markedly in recent years and has had a significant impact on both clinical and economic outcomes. Our results suggest that curtailing use of other antibiotics (particularly fluoroquinolones) may be important in attempts to curb further emergence of imipenem resistance.

The prevalence of resistance to imipenem and ceftazidime among Pseudomonas aeruginosa isolates is increasing worldwide.

Risk factors for nosocomial recovery (defined as the finding of culture-positive isolates after hospital admission) of imipenem-resistant P. aeruginosa (IRPA) and ceftazidime-resistant P. aeruginosa (CRPA) were determined.

Two separate case-control studies were conducted. Control subjects were matched to case patients (ratio, 2:1) on the basis of admission to the same ward at the same time as the case patient. Variables investigated included demographic characteristics, comorbid conditions, and the classes of antimicrobials used.

The study was conducted in a 400-bed general teaching hospital in Campinas, Brazil that has 14,500 admissions per year. Case patients and control subjects were selected from persons who were admitted to the hospital during 1992–2002.

IRPA and CRPA isolates were obtained from 108 and 55 patients, respectively. Statistically significant risk factors for acquisition of IRPA were previous admission to another hospital (odds ratio [OR],4.21 [95% confidence interval {CI}, 1.40-12.66];P = .01), hemodialysis (OR, 7.79 [95% CI, 1.59-38.16]; P = .01), and therapy with imipenem (OR, 18.51 [95% CI, 6.30-54.43]; P<.001), amikacin (OR, 3.22 [95% CI, 1.40-7.41]; P = .005), and/or vancomycin (OR, 2.48 [95% CI, 1.08-5.64]; P = .03). Risk factors for recovery of CRPA were previous admission to another hospital (OR, 18.69 [95% CI, 2.00-174.28]; P = .01) and amikacin use (OR, 3.69 [95% CI, 1.32-10.35]; P = .01).

Our study suggests a definite role for several classes of antimicrobials as risk factors for recovery of IRPA but not for recovery of CRPA. Limiting the use of only imipenem and ceftazidime may not be a wise strategy to contain the spread of resistant P. aeruginosa strains.

To evaluate whether resistance to third-generation cephalosporins and/or aztreonam was associated with a higher mortality rate among patients with nosocomial Klebsiella pneumoniae infections.

Retrospective cohort study.

Tertiary care university hospital.

A total of 143 patients with nosocomial infections due to K. pneumoniae were evaluated. Death within 21 days after diagnosis of infection was the outcome. Demographic data, invasive procedures, presence and severity of underlying conditions, infection diagnosis, anatomic site of isolation, and treatment of infection, as well as resistance to third-generation cephalosporins and/or aztreonam, were evaluated for association with the outcome.

The mortality associated with nosocomial K. pneumoniae infections was 22% in our study. Drug resistance was found in isolates from 48% of case patients. Multivariate analysis demonstrated that the severity of the patient's underlying condition (odds ratio, 12.50; P<.01) and isolation of the microorganism from the blood or from another usually sterile site (odds ratio, 2.94; P = .03) were associated with death. On the other hand, the presence of resistance to cephalosporins and/or aztreonam did not affect mortality, and the use of inadequate treatment was not significantly associated with increased mortality. When only the severe cases of infection were analyzed, the results were unchanged.

Resistance to cephalosporins and/or aztreonam did not affect mortality, and the use of inadequate treatment was not significantly associated with increased mortality. The reasons for this are not clear. It is possible that the severity of the underlying disease and the patient's condition have a larger role than the K. pneumoniae infection in determining the outcome, and initially inadequate treatment may not have an impact sufficient to cause irreversible damage, allowing treatment to be changed to an effective drug.

Patients colonized or infected with vancomycin-resistant enterococcus and methicillin-resistant Staphylococcus aureus may be at risk of acquiring vancomycin-resistant S. aureus if the vanA gene is transferred from vancomycin-resistant enterococcus to methicillin-resistant S. aureus..

Our goal was to identify risk factors for cocolonization or coinfection (CC/CI) with vancomycin-resistant enterococcus and methicillin-resistant S. aureus.

We conducted a descriptive, epidemiologic study of all patients with CC/CI identified from January 1998 to May 2003 and a nested case-control study of a cohort of patients hospitalized in the burn and wound unit.

We conducted our study in a 813-bed tertiary care university teaching hospital.

The study population consisted of patients found to have CC/CI during the study period.

Descriptive epidemiologic data were collected from hospital records of all patients identified as having CC/CI. A subset of patients hospitalized in the burn and wound unit were included in a case-control study.

CC/CI was detected in 71% of the patients during a single hospital stay. The burn and wound unit, which does active surveillance for both organisms, and the general medicine unit, which does not do active surveillance for either organism, cared for more than one-half of these patients. Among patients being cared for in the burn and wound unit, having exposure to 2 or more invasive devices (central venous catheters, indwelling urinary catheters, and enteral feeding tubes) and renal insufficiency were independent risk factors for CC/CI.

Patients with CC/CI are the population at greatest risk for vancomycin-resistant S. aureus colonization or infection. The number of invasive devices to which patients are exposed and, thus, possibly the patients' underlying severity of illness, as well as renal insufficiency, appear to be risk factors for CC/CI.

To examine bacterial antibiotic resistance and antibiotic use patterns in long-term acute care hospitals (LTACHs) and to evaluate effects of antibiotic use and other hospital-level variables on the prevalence of antibiotic resistance.

Multihospital ecologic study.

Antibiograms, antibiotic purchasing data, and demographic variables from 2002 and 2003 were obtained from 45 LTACHs. Multivariable regression models were constructed, controlling for other hospital-level variables, to evaluate the effects of antibiotic use on resistance for selected pathogens. Results of active surveillance in 2003 at one LTACH were available.

Among LTACHs, median prevalences of resistance for several antimicrobial-organism pairs were greater than the 90th percentile value for National Nosocomial Infections Surveillance system (NNIS) medical intensive care units (ICUs). The median prevalence of methicillin resistance among Staphylococcus aureus isolates was 84%. More than 60% of patients in one LTACH were infected or colonized with methicillin-resistant S. aureus and/or vancomycin-resistant Enterococcus at the time of admission. Antibiotic consumption in LTACHs was comparable to consumption in NNIS medical ICUs. In multivariable logistic regression modeling, the only significant association between antibiotic use and the prevalence of antibiotic resistance was for carbapenems and imipenem resistance among Pseudomonas aeruginosa isolates (odds ratio, 11.88 [95% confidence interval, 1.42-99.13]; P = .02).

The prevalence of antibiotic resistance among bacteria recovered from patients in LTACHs is extremely high. Although antibiotic use in LTACHs likely contributes to resistance prevalence for some antimicrobial-organism pairs, for the majority of such pairs, other variables, such as prior colonization with and horizontal transmission of antimicrobial-resistant pathogens, may be more important determinants. Further research on antibiotic resistance in LTACHs is needed, particularly with respect to determining optimal infection control practices in this environment.

In 2004, the Commonwealth of Pennsylvania mandated hospitals to report healthcare-associated infections (HAIs). The increased workload led our Infection Control staff to collaborate with Atlas, a group of chart abstractors.

The objective of this study was to assess our first year of experience with mandatory reporting of HAIs—specifically, to assess Atlas' contribution to surveillance.

Cases were selected if they had 1 or more of the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes designated by Pennsylvania as a possible HAI. After training by the Infection Control staff, Atlas applied National Nosocomial Infection Surveillance (NNIS) system case definitions for catheter-associated urinary tract infections (UTIs) and surgical site infections (SSIs), and they applied NNIS chest imaging criteria to eliminate cases that were not ventilator-associated pneumonia (VAP). To assess Atlas' performance, Infection Control staff conducted a parallel review.

For discharges from the hospital during the fourth quarter of 2004, a total of 410 UTIs, 59 SSIs, and 56 VAPs were identified on the basis of state-designated ICD-9-CM codes; review by Atlas/Infection Control determined that 15%, 15%, and 16% of cases met case definitions, respectively. Of cases reviewed by both Infection Control and Atlas, 87% of the assessments made by Atlas were correct for UTI, and 96% were correct for SSI. For VAP, Infection Control concluded that 39% of cases could be ruled out on the basis of chest imaging criteria; Atlas correctly dismissed these 12 cases but incorrectly dismissed an additional 6 (error, 19%). Surveillance was not timely: 1-2 months elapsed between the time of HAI onset and the earliest case review.

With ongoing training by Infection Control, Atlas successfully demonstrated a role in retrospective HAI surveillance. However, despite a major effort to comply with mandates, time lags and other design limitations rendered the data of low utility for Infection Control. States that are planning HAI-reporting programs should standardize an efficient surveillance methodology that yields data capable of guiding interventions to prevent HAI.

To determine the influence the Hawthorne effect has on compliance with antiseptic hand rub (AHR) use among healthcare personnel.

Observational study.

Five intensive care units of a university hospital in Berlin, Germany.

Medical personnel were monitored in 2 periods regarding compliance with AHR use when there were indications for AHR use. In the first period, the personnel had no knowledge of being observed. The second observation period was announced to the staff of the intensive care units in advance and information about what the observer would be monitoring was provided. Potential confounders of compliance with AHR use included occupational groups (nurses, physicians, and other healthcare workers), intensive care units, and indications for AHR use before or after any procedure.

Data were collected from 2,808 indications for AHR use. The overall rate of compliance was 29% (95% confidence interval, 26%–32%) in the first period and 45% (95% confidence interval, 43%–47%) in the second period. A logistic regression analysis with potential confounders revealed a significant odds ratio for the comparison between period 2 and period 1. The differences in compliance with AHR use were statistically significant (P<.001) between the occupational groups (nurses had the highest compliance and physicians had middle compliance) and between indication for AHR use before procedures and indication for AHR use after procedures.

The Hawthorne effect has a marked influence on compliance with AHR use, with a 55% increase of compliance with overt observation. This result is consistent throughout subgroups. The rate of compliance with AHR use may in fact be lower than we thought because of results from studies that did not take the Hawthorne effect into account. The results of this study underline the necessity for infection control teams to be on wards as often as possible.

To evaluate the reproducibility and workability of the in vivo test model of the European test standard EN 12791 regarding the effectiveness of surgical hand antiseptics and, as a secondary objective, to evaluate the power of the model to discriminate between the effectiveness of various formulations of surgical hand antiseptics.

Prospective, randomized, multicenter study with a Latin square design.

Five laboratories at 2 universities, 2 disinfectant manufacturers, and 1 private testing institution.

Twenty healthy adults in each laboratory.

Surgical hand antisepsis was performed by scrubbing with chlorhexidine gluconate 4% detergent (CHG) or by rubbing the hands with propan-2-OL (70% by volume; Iso 70) or ethanol 85% (E 85); rubbing the hands and forearms for 3 minutes with propan-1-OL (N 60) was used as the reference disinfection procedure. We deliberately chose to use these antiseptics at the given concentrations because they were intended to cover the range of typical antiseptics submitted for approval according to EN 12791.

In once-weekly tests, the immediate effects of the 4 antiseptics were established according to the method laid down in EN 12791 by assessing the release of skin flora from the fingertips as viable bacteria counts per milliliter of sampling fluids before treatment and viable bacteria counts immediately after treatment, separately for both hands, such that after 4 weeks each volunteer had used every formulation once.

The mean log reduction factor (RF) for the release of bacterial skin flora (the log RF was calculated as the log count before treatment minus the log count after treatment) and corresponding standard deviations for the 4 hand antisepsis formulations were as follows: for CHG, 1.1 ± 0.3 colony-forming units (cfu) per milliliter of sampled fluid; for Iso 70, 1.7 ± 0.3 cfu/mL; for E 85, 2.1 ± 0.3 cfu/mL; and for N 60, 2.4 ± 0.4 cfu/mL. The differences between these values proved significant (P<.001) by analysis of variance and in Tukey's “honestly significantly different” (HSD) post hoc test. Although, with regard to their immediate antibacterial activity, the same ranking of these antiseptics was found at all laboratories, the levels of efficacy were significantly different across laboratories (P<.001); no statistical difference was found between left and right hands (P>.01). Relating the log RF values of the other 3 formulations to those of the reference formulation (N 60) abolished differences between laboratories (P = .16); in addition, the interclass correlation coefficient decreased from 9.1% to 4.5%. With 20 volunteers, a minimum difference of 0.47 log between the mean log RFs of the reference formulation and an inferior test formulation will be detected as significant at an α of .05 (1-sided) and a 1 — β value of .8.

The test method described in EN 12791 yielded the same conclusion on the effectiveness of the tested formulations in every laboratory and proved, therefore, reproducible and workable.

To investigate the potential role of blood pressure (BP) cuffs in the spread of bacterial infections in hospitals.

A comprehensive, prospective study quantitatively and qualitatively evaluating the bacterial contamination on BP cuffs of 203 sphygmomanometers in use in 18 hospital units from January through March 2003.

A university hospital with surgical, medical, and pediatric units.

A level of contamination reaching 100 or more colony-forming units per 25 cm2 was observed on 92 (45%) of inner sides and 46 (23%) of outer sides of 203 cuffs. The highest rates of contamination occurred on the inner side of BP cuffs kept in intensive care units (ICUs) (20 [83%] of 24) or on nurses' trolleys (27 [77%] of 35). None of the 18 BP cuffs presumed to be clean (ie, those that had not been used since the last decontamination procedure) had a high level of contamination. Potentially pathogenic microorganisms were isolated from 27 (13%) of the 203 BP cuffs: 20 of these microorganisms were Staphylococcus aureus, including 9 methicillin-resistant strains. The highest rates of contamination with potentially pathogenic microorganisms were observed on cuffs used in ICUs and those kept on nurses' trolleys. For 4 patients with a personal sphygmomanometer, a genetic link was found between the strains isolated from the BP cuffs and the strains isolated from the patients.

The results of this survey highlight the importance of recognizing BP cuffs as potential vectors of pathogenic bacteria among patients and as a source of reinfection when dedicated to a single patient, emphasizing the urgent need for validated procedures for their use and maintenance.

To estimate the transmission efficiency of human immunodeficiency virus (HIV) through medical injections and other invasive procedures.

We searched our own files and Medline (from 1966-2004, using the keywords [“iatrogenic” or “nosocomial” or “injections”] and “HIV”) for reports of iatrogenic outbreaks worldwide, except outbreaks traced to receipt of contaminated blood or blood products. We also analyzed information from a case-control study of percutaneous exposures to healthcare workers.

Worldwide healthcare settings.

We identified 8 iatrogenic outbreaks that met our study criteria; published information from 4 outbreaks was sufficient to estimate transmission efficiency.

From the 4 documented iatrogenic outbreaks, we estimated that 1 iatrogenic infection occurred after 8-52 procedures involving HIV-infected persons. Although only 0.3% of healthcare workers seroconvert after percutaneous exposure, a case-control study reported that deep injuries and other risk factors collectively increased seroconversion risk by as much as 50 times. Laboratory investigations demonstrate HIV survival through time and various rinsing regimens. We estimate that the transmission efficiency in medical settings with no or grossly insufficient efforts to clean equipment ranges from 0.5% to 3% for lower risk procedures (eg, intramuscular injections) and from 10% to 20% or more for high-risk procedures. Efforts to clean equipment, short of sterilization, may cut the transmission efficiency by 0%-100%. Procedures that contaminate multidose vials may accelerate transmission efficiency.

To achieve better estimates of the transmission efficiency for a range of medical procedures and settings, investigations of iatrogenic outbreaks should be accorded high priority.

In 1998, a study in the intensive care unit (ICU) of our institution suggested possible transmission of Pseudomonas aeruginosa from faucet to patient and from patient to patient. Infection-control measures were implemented to reduce the degree of P. aeruginosa colonization in faucets, to reduce the use of faucet water in certain patient care procedures, and to reduce the rate of transmission from patient to patient.

To evaluate the effect of the control measures instituted in 1999 to prevent P. aeruginosa infection and colonization in ICU patients.

Prospective, molecular, epidemiological investigation.

A 870-bed, university-affiliated, tertiary care teaching hospital.

The investigation was performed in a manner identical to the 1998 investigation. ICU patients with a clinical specimen positive for P. aeruginosa were identified prospectively. Swab specimens from the inner part of the ICU faucets were obtained for the culture on 9 occasions between September 1997 and December 2000. All patients and environmental isolates were typed by pulsed-field gel electrophoresis (PFGE).

Compared with the 1998 study, in 2000 we found that the annual incidence of ICU patients colonized or infected with P. aeruginosa had decreased by half (26.6 patients per 1,000 admissions in 2000 vs 59.0 patients per 1,000 admissions in 1998), although the populations of patients were comparable. This decrease was the result of the decreased incidence of cases in which an isolate had a PFGE pattern identical to that of an isolate from a faucet (7.0 cases per 1,000 admissions in 2000, vs 23.6 per 1,000 admissions in 1998) or from another patient (6.5 cases per 1,000 admissions in 2000 vs 16.5 cases per 1,000 admissions in 1998), whereas the incidence of cases in which the isolate had a unique PFGE pattern remained nearly unchanged (13.1 cases per 1,000 admissions in 2000 vs 15.6 cases per 1,000 admissions in 1998).

These results suggest that infection control measures were effective in decreasing the rate of P. aeruginosa colonization and infection in ICU patients, confirming that P. aeruginosa strains were of exogenous origin in a substantial proportion of patients during the preintervention period.

To determine the incidence of and identify risk factors for sternal surgical site infection (SSI).

Prospective cohort study. Data on potential risk factors, including the type of operating theater and infection data, were collected prospectively and analyzed by multivariate analysis.

Siyami Ersek Thoracic and Cardiovascular Surgery Hospital, a 700-bed teaching hospital and the largest center for cardiac surgery in Turkey. The cardiothoracic unit performs approximately 3,000 cardiac operations per year.

All adult patients who underwent cardiac surgery with sternotomy between January 14, 2002, and July 1, 2002, and who survived at least 4 days after surgery were included in the study.

Potential risk factor data were complete for 991 patients. There was sternal SSI in 41 patients (4.1%). Female sex, diabetes mellitus, operation performed in the older operating theaters, and duration of procedure exceeding 5 hours were identified as independent risk factors for sternal SSI.

Female and diabetic patients are at higher risk for sternal SSI and should be followed up carefully after cardiac surgery to prevent the development of sternal SSI. Reducing the duration of surgery could reduce the rate of postoperative sternal SSI. The operating theater environment may have an important role in the pathogenesis of sternal SSI, and appropriate ventilation of the operating theaters would be critical in the prevention of sternal SSI.

To examine whether intervention by infectious diseases physicians (IDPs) in the treatment decisions that emphasize adequate antifungal treatment and early removal of central venous catheter for patients with Candida bloodstream infection (BSI) improves prognosis.

Retrospective cohort study of patients with Candida BSI, comparing the prognosis of patients before and after the start of the intervention.

A 1,240-bed, tertiary care university hospital.

Forty patients with Candida BSI during a 2-year period, from January 2001 to December 2002, were included in the study Twenty-three patients in the first year after the start of intervention by IDPs (intervention group) were compared with 17 patients in the first year before the start of the IDP intervention (baseline group).

In January 2002, a total of 5 IDPs at Kyoto University Hospital gave unsolicited recommendations on antifungal treatment and advised all physicians treating inpatients who had Candida BSI to remove the central venous catheter.

No significant difference was seen between the 2 groups in patients' clinical background, species, and fluconazole susceptibility of the causative organisms. The 30-day survival rate was significantly better in the intervention group (18 [78%] of 23 patients) than in the baseline group (7 [44%] of 16 patients; P = .04 by Fisher's exact test). More patients in the intervention group than in the baseline group received appropriate antifungal therapy (81% vs 50%) and had their central venous catheter removed at an appropriate time (95% vs 81%)

The introduction of an active system of IDP consultation for every case of Candida BSI in our hospital substantially improved patient outcomes.

To compare the incidence rates of catheter-related bloodstream infection associated with different vascular access methods in patients receiving hemodialysis.

Tertiary care public hospital in Western Australia.

Retrospective analysis of surveillance data collected by the hospital's infection control department.

The number of confirmed bloodstream infections for each type of vascular access was identified for the period from July 2002 through June 2003. The corresponding number of patient-days was determined to calculate the infection incidence rates. The serially correlated data were then analyzed using Poisson generalized estimating equations.

A total of 32 confirmed bloodstream infections were identified. Infection rates, in number of infections per 1,000 patient-days, were as follows: 0.4 for native arteriovenous fistulae; 2.86 for synthetic arteriovenous grafts; 4.02 for permanent, tunneled, cuffed central venous catheters; and 20.2 for temporary, nontunneled, noncuffed central venous catheters. Compared with permanent catheters, the monthly infection rate associated with the temporary catheters was significantly higher (incident rate ratio [IRR], 5.025 [95% confidence interval {CI}, 1.532-16.484]; P = .008) and that of arteriovenous fistulae was significantly lower (IRR, 0.099 [95% CI, 0.030-0.324]; P = .001). The monthly infection rate for arteriovenous grafts was not significantly different from that for permanent central venous catheters (IRR, 0.702 [95% CI, 0.246-2.008]; P = .510).

A hierarchy of infection risk associated with vascular access type is evident. Native arteriovenous fistulae should be recommended for all patients receiving chronic hemodialysis, to minimize infection.