Case-control studies analyzing antibiotic exposure as a risk factor for antimicrobial resistance usually assume single-drug resistance in the bacteria under study, even though resistance to multiple antimicrobials may be present. Since antibiotic selection pressures differ depending on the susceptibility profile of the antimicrobial-resistant bacteria, an accurate assessment of whether exposure to an individual antimicrobial is a risk factor for the emergence of resistance should distinguish between single-drug–resistant and multidrug-resistant bacteria.

To determine whether the exposures to individual antibiotics that were identified as independent risk factors in case-control studies differed depending on whether single-drug–resistant or multidrug-resistant bacteria were evaluated.

Two retrospective case-control studies were performed with data on patients harboring Pseudomonas aeruginosa strains resistant only to ciprofloxacin (CRPA) and patients harboring P. aeruginosa strains resistant to ciprofloxacin and other antibiotics (multidrug-resistant P. aeruginosa [MDR-PA]). These 2 groups were compared with patients not harboring P. aeruginosa.

Two tertiary care hospitals.

A total of 41 patients harboring CRPA and 151 patients harboring MDR-PA were identified and matched to 192 control subjects. By conditional logistic regression, independent risk factors associated with presence of CRPA were nonambulatory status (OR, 5.6 [95% confidence interval {CI}, 1.4-23]; P = .02) and prior ciprofloxacin exposure (OR, 5.0 [95% CI, 1.2-21]; P = .03). Independent risk factors for presence of MDR-PA were a Charlson score greater than 2 (OR, 3.3 [95% CI 1.8-6.0]; P<.001) and exposure to quinolones (OR, 2.8 [95% CI, 1.2-5.0]; P = .001), third- and fourth-generation cephalosporins (OR, 3.5 [95% CI, 1.7-7.1]; P<.001), imipenem (OR, 3.8 [95% CI, 1.2-12.1]; P = .02), and/or aminoglycosides (OR, 2.3 [95% CI, 1.04-5.1]; P = .04).

There were substantial differences in exposure to individual antimicrobials between patients harboring CRPA and patients harboring MDR-PA. Future case-control studies addressing risk factors for single-drug–resistant bacteria should consider the complete susceptibility profile of the bacteria under investigation.

To determine the pathogens associated with surgical site infections (SSIs) and describe patterns of antimicrobial use and resistance in orthopedic and neurosurgical patients in a large university hospital in Vietnam.

Prospective cohort study.

Cho Ray Hospital, Ho Chi Minh City, Vietnam.

All patients who had operations during a 5-week study period.

Of 702 surgical patients, 80 (11.4%) developed an SSI. The incidence of SSI among orthopedic patients was 15.2% (48 of 315), and among neurosurgical patients it was 8.3% (32 of 387). Postoperative bacterial cultures of samples from the surgical sites were performed for 55 (68.8%) of the 80 patients with SSI; 68 wound swab specimens and 10 cerebrospinal fluid samples were cultured. Of these 78 cultures, 60 (76.9%) were positive for a pathogen, and 15 (25%) of those 60 cultures yielded multiple pathogens. The 3 most frequently isolated pathogens were Pseudomonas aeruginosa (29.5% of isolates), Staphylococcus aureus (11.5% of isolates), and Escherichia coli (10.3% of isolates). Ninety percent of S. aureus isolates were methicillin resistant, 91% of P. aeruginosa isolates were ceftazidime resistant, and 38% of E. coli isolates were cefotaxime resistant. All but 1 of the 702 patients received antimicrobial therapy after surgery, and the median duration of antimicrobial therapy was 11 days. Commonly used antimicrobials included aminopenicillins and second- and third-generation cephalosporins. Two or, more agents were given to 634 (90%) of the patients, and most combination drug regimens (86%) included an aminoglycoside.

Our data indicate that the incidence of SSI is high in our study population, that the main pathogens causing SSI are gram-negative bacteria and are often resistant to commonly used antimicrobials, that the use of broad-spectrum antimicrobials after surgery is widespread, and that implementation of interventions aimed at promoting appropriate and evidence-based use of antimicrobials are needed in Vietnam.

To examine the duration of methicillin-resistant Staphylococcus aureus (MRSA) carriage and its determinants and the influence of eradication regimens.

Retrospective cohort study.

A 1,033-bed tertiary care university hospital in Bern, Switzerland, in which the prevalence of methicillin resistance among S. aureus isolates is less than 5%.

A total of 116 patients with first-time MRSA detection identified at University Hospital Bern between January 1, 2000, and December 31, 2003, were followed up for a mean duration of 16.2 months.

Sixty-eight patients (58.6%) cleared colonization, with a median time to clearance of 7.4 months. Independent determinants for shorter carriage duration were the absence of any modifiable risk factor (receipt of antibiotics, use of an indwelling device, or presence of a skin lesion) (hazard ratio [HR], 0.20 [95% confidence interval {CI}, 0.09-0.42]), absence of immunosuppressive therapy (HR, 0.49 [95% CI, 0.23-1.02]), and hemodialysis (HR, 0.08 [95% CI, 0.01-0.66]) at the time MRSA was first MRSA detected and the administration of decolonization regimen in the absence of a modifiable risk factor (HR, 2.22 [95% CI, 1.36-3.64]). Failure of decolonization treatment was associated with the presence of risk factors at the time of treatment (P = .01). Intermittent screenings that were negative for MRSA were frequent (26% of patients), occurred early after first detection of MRSA (median, 31.5 days), and were associated with a lower probability of clearing colonization (HR, 0.34 [95% CI, 0.17-0.67]) and an increased risk of MRSA infection during follow-up.

Risk factors for MRSA acquisition should be carefully assessed in all MRSA carriers and should be included in infection control policies, such as the timing of decolonization treatment, the definition of MRSA clearance, and the decision of when to suspend isolation measures.

To assess the risk of environmental and healthcare worker (HCW) contamination with vancomycin-resistant enterococci (VRE) during outpatient procedures performed on fecally continent patients currently colonized with VRE (cVRE) or previously colonized with VRE (pVRE).

Observational study.

Outpatient consultation and radiology rooms and the hemodialysis unit in a university teaching hospital.

Fecally continent cVRE and pVRE patients.

Both cVRE and pVRE patients attended standardized mock outpatient consultations and routine hemodialysis sessions in an area that had been thoroughly cleaned and microbiologically confirmed to be free of VRE contamination. After each session, the patient, environment, and participating HCW were tested for VRE contamination.

Fourteen cVRE patients participated in 49 mock outpatient consultation sessions and radiology sessions or 26 actual hemodialysis sessions, and 7 pVRE patients participated in 28 outpatient consultation sessions. Sessions with cVRE patients had higher rates of contamination of the environment (chair cultures were positive for VRE in 36% of outpatient consultation sessions, 58% of hemodialysis sessions; couch cultures were positive in 48% of outpatient consultation sessions, 42% of radiology sessions, and 45% of hemodialysis sessions), contamination of HCW gowns (gown cultures were positive in 20% of outpatient consultation sessions, 4% of radiology sessions, and 30% of hemodialysis sessions), and contamination of patients' own hands (hand cultures were positive in 36% of outpatient consultation sessions, 25% of radiology sessions, and 54% of hemodialysis sessions). Overall, contamination rates associated with pVRE patients attendance at outpatient consultations were 12% of those noted for cVRE patients (odds ratio, 0.10; 95% confidence interval, 0.03-0.42; P = .001).

Given the nature of the contamination risk posed by fecally continent cVRE patients undergoing outpatient procedures, infection control measures should focus on effective HCW and patient hand hygiene and chair and couch cleaning, to minimize transmission of VRE.

To evaluate 2 active surveillance strategies for detection of enteric vancomycin-resistant enterococci (VRE) in an intensive care unit (ICU).

Thirty-month prospective observational study.

ICU at a university-affiliated referral center.

All patients with an ICU stay of 24 hours or more were eligible for the study.

Clinical active surveillance (CAS), involving culture of a rectal swab specimen for detection of VRE, was performed on admission, weekly while the patient was in the ICU, and at discharge. Laboratory-based active surveillance (LAS), involving culture of a stool specimen for detection of VRE, was performed on stool samples submitted for Clostridium difficile toxin detection.

Enteric colonization with VRE was detected in 309 (17%) of 1,872 patients. The CAS method initially detected 280 (91%) of the 309 patients colonized with VRE, compared with 25 patients (8%) detected by LAS; colonization in 4 patients (1%) was initially detected by analysis of other clinical specimens. Most patients with colonization (76%) would have gone undetected by LAS alone, whereas use of the CAS method exclusively would have missed only 3 patients (1%) who were colonized. CAS cost $1,913 per month, or $57,395 for the 30-month study period. Cost savings of CAS from preventing cases of VRE colonization and bacteremia were estimated to range from $56,258 to $303,334 per month.

A patient-based CAS strategy for detection of enteric colonization with VRE was superior to LAS. In this high-risk setting, CAS appeared to be the most efficient and cost-effective surveillance method. The modest costs of CAS were offset by the averted costs associated with the prevention of VRE colonization and bacteremia.

To assess the response of long-term care facilities (LTCFs) to the 2004-2005 influenza vaccine shortage and the impact on resident and healthcare worker (HCW) immunization rates.

A 12-item questionnaire was sent to 824 randomly selected LTCFs in December 2004. The following 2 open-ended questions were also asked: “How did you cope with the vaccine shortage?” and “Who helped you get your supply?” Immunization rates reported by LTCF administrators for 2003-2003 and 2003-2004 were compared with those for 2004-2005. Immunization rates were defined as the proportion of all eligible residents and HCWs who received influenza vaccine.

Responses were received from 380 LTCFs (46.3%), which had a total of 38,447 beds. Resident mean influenza immunization rates (±SD) decreased from 85% ± 15.3% in 2002-2003 and 85.1% ± 15.3% in 2003-2004 to 81.9% ± 19.4% in the 2004-2005 influenza season (P = .025). The immunization rates among HCWs also decreased from 51% in 2002-2003 and 2003-2004 to 38.4% in 2004-2005 (P<.001). In response to one of the open-ended questions, 96 facilities (25.3%) reported that they obtained vaccine from 2 or more sources. Eight percent commented on specific intensified infection control efforts, and only 2.3% commented on emergency preparedness.

The influenza vaccine shortage in 2004-2005 impacted immunization practices of LTCFs across the United States, leading to decreases in both resident and HCW vaccination rates. The significant decrease in vaccination rates in LTCFs is of concern and has broad implications for policy makers working on emergency preparedness for a possible pandemic of influenza.

To establish the occurrence, distribution, and secular time trend of nosocomial infections (NIs) in a surgical intensive care unit (ICU).

Follow-up study in a teaching hospital in Spain.

In May 1995 we established an nosocomial infection surveillance system in our surgical ICU. We collected information daily for all patients who were in the ICU for at least 48 hours (546 patients from 1996 through 2000). We used the Centers for Disease Control and Prevention definitions and criteria for infections. Monthly, we determined the site-specific incidence densities of NIs, the rates of medical device use, and the Poisson probability distribution, which determined whether the case count equalled the number of expected cases (the mean number of cases during the previous year, with extreme values excluded). We compared yearly and monthly infection rates by Poisson regression, using site-specific NIs as a dependent variable and year and month as dummy variables. We tested annual trends with an alternative Poisson regression model fitting a single linear trend.

The average rate of catheter-associated urinary tract infections was 8.4 per 1000 catheter-days; that of ventilator-associated pneumonia, 21 per 1000 ventilator-days; and that of central line–associated bloodstream infections, 30 per 1000 central line–days. The rate of urinary tract infections did not change over the study period, but there was a trend toward decreases in the rates of central line–associated bloodstream infections and ventilator-associated pneumonia.

An NI surveillance and control program contributed to a progressive decrease in NI rates.

To investigate a case of Creutzfeldt-Jakob disease (CJD) possibly acquired from contaminated neurosurgical instruments.

Retrospective review of medical records, hospital databases, service log books, and state vital statistics.

A tertiary care hospital (hospital A) in Missouri.

The case patient was a 38-year-old African American woman with a 9-month history of progressive memory loss, visual disturbances, and dementia. She underwent neurosurgery in November 1996. CJD was confirmed in April 2004 by immunodiagnostic testing of brain biopsy samples. All patients who underwent neurosurgery at the same hospital within 6 months before or after the case patient's procedure were identified and investigated for preoperative or postoperative evidence of CJD.

We reviewed data on 268 neurosurgical procedures, 84 pathology log entries, and 60 death certificates for neurosurgical patients at hospital A and identified 2 suspected cases of CJD. Clinical features and definitive prion testing of stored brain biopsy samples excluded a diagnosis of CJD. Standard operating room procedures were in place, but specific protocols for handling instruments potentially contaminated with prions were not used.

Neurosurgical instruments were not implicated as the source exposure for CJD in the case patient. The 2 patients with suspected CJD were identified from different data sources, suggesting good internal consistency in data collection. The key elements of this investigation are suggested for use in future investigations into potential cases of iatrogenic CJD.

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.

Reliable data on the costs attributable to nosocomial infection (NI) are crucial to demonstrating the real cost-effectiveness of infection control measures. Several studies investigating this issue with regard to intensive care unit (ICU) patients have probably overestimated, as a result of inappropriate study methods, the part played by NIs in prolonging the length of stay.

Data from a prospective study of the incidence of NI in 5 ICUs over a period of 18 months formed the basis of this analysis. For describing the temporal dynamics of the data, a multistate model was used. Thus, ICU patients were counted as case patients as soon as an NI was ascertained on any particular day. All patients were then regarded as control subjects as long as they remained free of NI (time-to-event data analysis technique).

Admitted patients (n = 1,876) were observed for the development of NI over a period of 28,498 patient-days. In total, 431 NIs were ascertained during the study period (incidence density, 15.1 NIs per 1,000 patient-days). The influence of NI as a time-dependent covariate in a proportional hazards model was highly significant (P< .0001, Wald test). NI significantly reduced the discharge hazard (hazard ratio, 0.72 [95% confidence interval, 0.63-0.82])—that is, it prolonged the ICU stay. The mean prolongation of ICU length of stay due to NI ( ± standard error) was estimated to be 5.3 ± 1.6 days.

Further studies are required to enable comparison of data on prolongation of ICU length of stay with the results of various study methods.

To assess whether patients hospitalized in beds physically adjacent to critically ill patients are at increased risk to acquire multidrug-resistant pathogens.

Cohort study.

Shaare Zedek Medical Center, a 550-bed medical referral center.

From April to September 2004, we enrolled consecutive newly admitted patients who were hospitalized in beds adjacent to either mechanically ventilated patients or patients designated as “do not resuscitate” (DNR). For each of these patients, we also enrolled a control patient who was not hospitalized in a bed adjacent to a critically ill patient. We collected specimens from the anterior nares, the oral cavity, and the perianal zone at the time of admission and subsequently at 3-day intervals until discharge or death. Specimens were cultured on selective media to detect growth of antibiotic-resistant pathogens, including Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β lactamase (ESBL)–producing Enterobacteriaceae, and vancomycin-resistant enterococci (VRE).

We enrolled 46 neighbor-control pairs. Among neighbors and controls, respectively, the incidence rates for isolation of A. baumannii was 8.3 and 4 isolations per 100 patient-days (relative risk [RR], 2.1 [95% confidence interval {CI}, 0.8-5.2]; P = .12), the incidence rates for MRSA were 1.4 and 2.6 isolations per 100 patient-days (RR, 0.6 [95% CI, 0.1-2.3]; P = .45), the incidence rates for ESBL-producing Enterobacteriaceae were 10.5 and 9 isolations per 100 patient-days (RR, 1.2 [95% CI, 0.6-2.4]; P = .84), the incidence rates for VRE were 4.3 and 4.8 isolations per 100 patient-days (RR, 0.9 [95% CI, 0.3-2.4]; P = 1), and the composite incidence rate was 21.7 and 16.2 isolations per 100 patient-days (RR, 1.3 [95% CI, 0.8-2.3]; P = 0.3).

In this pilot study, we did not detect an increased incidence rate of isolation of multidrug-resistant pathogens among patients hospitalized in beds adjacent to critically ill patients. Further studies with larger samples should be conducted in order to generate valid data and provide patients, physicians, and policy makers with a sufficient knowledge base from which decisions can be made.

To evaluate the impact of an infection control program in an intensive care unit (ICU).

Prospective before-after study. Two 6-month study periods were compared; between these periods, an infection control program based on isolation was implemented.

Polyvalent ICU of Montpellier Teaching Hospital.

Any patient who was hospitalized in the ICU for >48 hours and was discharged during 1 of the 2 periods.

The main patient-related variables were sex, age at admission, type of patient (surgical, medical, or trauma), Simplified Acute Physiology Score II, length of ICU stay, need for intubation, duration of exposure to invasive devices, onset of nosocomial infection and pathogens responsible, and death. We compared the 2 study periods with respect to the incidence of 4 nosocomial infections (pneumonia, urinary tract infection, bacteremia, and catheter-associated infection), the frequency of infection with the main multidrug-resistant pathogens, and patient survival.

Patients in periods 1 and 2 were similar with regard to sex, age, physiology score, and exposure to invasive devices. The rates of infection with multidrug-resistant pathogens were significandy lower during period 2 than during period 1 (infection rate: 28.1% of patients in period 1 and 9.6% of patients in period 2 [P = .01]; pneumonia rate: 32.6% of patients in period 1 and 4.2% of patients in period 2 [P = .008]). The mortality rate among patients with nosocomial pneumonia was 38.2% in period 1 and 4.3% in period 2 (P = .009).

After implementation of an infection control program, the rate of infection with multidrug-resistant pathogens decreased, as did the mortality rate among patients with nosocomial pneumonia.

To identify nursing home resident and facility characteristics associated with patients not receiving influenza immunization and having unknown immunization status.

Secondary data analysis using multinomial logistic regression of data from the National Nursing Home Survey, a nationally representative establishment-based survey.

A total of 1,423 nursing facilities of all ownerships and certifications systematically sampled with probability proportional to number of beds.

A total of 7,350 randomly sampled people aged 65 years or older residing in nursing homes between July and December 1999 (approximately 6 per facility).

Immunization status of residents.

Fifteen percent of residents were not immunized and 19% had unknown immunization status. In multivariate analysis, lack of immunization and unknown immunization status were each separately associated with being newly admitted, with no or unknown pneumococcal immunization, and with facility failures to screen for immunization and to record inoculation in the medical record. High-risk status and staff immunization requirements had no effect. Separate analyses showed that residents with unknown immunization status are statistically significantly different from both those vaccinated and those not vaccinated.

This study indicates that both resident and facility characteristics are associated with failure to be immunized for influenza. Facilities should consider targeting younger, newly admitted, and residential care residents for influenza immunization, since they are more likely to be missed. Further research into the barriers to immunization specific to nursing home resident choice or opportunity may be warranted.

To validate an automated system for the detection of patients with nosocomial infection (NI) in an intensive care unit (ICU).

Retrospective analysis of data from the hospital information system. We applied 3 different NI suspicion criteria (positive microbiology reports, antibiotic administration, and diagnosis of clinical infection) and compared the results to those of a prospective NI incidence study done in the ICU during the same period (1999-2002).

A 250-bed general hospital in Barcelona, Spain.

From April 15, 1999, through June 30, 2002, 1380 patients were admitted to the ICU. Of these, 1043 had an ICU stay of more than 24 hours and were included in the study.

At least one NI suspicion criterion was present for 242 patients (23.2%); 2 criteria were present for 184 patients (17.6%); and all 3 criteria were present for 112 (11.7%). Comparison of hospital information system data to the results of the prospective study indicated that the combination of 2 criteria demonstrated the most satisfactory sensitivity (94.3%; 95% confidence interval [CI], 79.5%-99.0%) and specificity (83.6%; 95% CI, 76.8%-88.9%). The positive predictive value was 55.9% (95% CI, 42.5%-68.6%); the negative predictive value was 98.5% (95% CI, 94.2%-99.7%). The system could assign a site of infection for 90.4% of the NIs detected.

The hospital information system was a useful tool for retrospectively detecting patients with an NI during the ICU stay. Given its high sensitivity, it may be useful as an alert for the NI team.

Newborns in a hospital nursery were exposed to a mother whose sputum was direct-smear negative for acid-fast bacilli but culture positive for Mycobacterium tuberculosis. Given the low risk for exposure, the high susceptibility of infants to M. tuberculosis infection, and the possibility of hepatotoxicity due to isoniazid therapy, a decision analysis model was used to determine whether administration of isoniazid prophylaxis against tuberculosis is preferable to no administration of prophylaxis.

A decision analysis tree was constructed with software, using probabilities from the literature and costs from local health facilities. The expected values for each strategy were obtained, and sensitivity analyses were performed.

For the strategy in which prophylaxis was administered under direct observation (DO), the probability for survival was 0.999980. For the strategy in which no prophylaxis was administered, the probability of survival was 0.999950, which corresponds to 3 more deaths per 100,000 patients than with the DO prophylaxis strategy. The incremental cost-effectiveness of the DO prophylaxis strategy was $21,710,000 per death prevented. Sensitivity analysis for survival showed that the DO prophylaxis strategy was preferable to the strategy in which no prophylaxis is given if the probability of infection was >0.0002, the probability of tuberculous disease in an infected infant who did not receive prophylaxis was greater than 0.12, the probability of dying from tuberculosis was greater than 0.025, the probability of hepatotoxicity was less than 0.004, and the probability of dying from hepatotoxicity was less than 0.04. For the strategy in which prophylaxis was administered under non-DO conditions (ie, by parents), the incremental cost-effectiveness was $929,500 per death prevented, which is approximately 5% of the incremental cost-effectiveness of the DO prophylaxis strategy.

This model provides a structure for determining the preferable prophylaxis strategies for different risks of exposure to tuberculosis in a nursery. Administration of prophylaxis is preferable to no administration of prophylaxis, unless the probability of infection is extremely low.

To evaluate the effectiveness of an intervention based on training and the use of a protocol with an automatic stop of antimicrobial prophylaxis to improve hospital compliance with surgical antibiotic prophylaxis guidelines.

An interventional study with a before-after trial was conducted in 3 stages: a 3-year initial stage (January 1999 to December 2001), during which a descriptive-prospective survey was performed to evaluate surgical antimicrobial prophylaxis and surgical site infections; a 6-month second stage (January to June 2002), during which an educational intervention was performed regarding the routine use of a surgical antimicrobial prophylaxis request form that included an automatic stop of prophylaxis (the “automatic-stop prophylaxis form”); and a 3-year final stage (July 2002 to June 2005), during which a descriptive-prospective survey of surgical antimicrobial prophylaxis and surgical site infections was again performed.

An 88-bed teaching hospital in Entre Ríos, Argentina.

A total of 3,496 patients who underwent surgery were included in the first stage of the study and 3,982 were included in the final stage.

Comparison of the first stage of the study with the final stage revealed that antimicrobial prophylaxis was given at the appropriate time to 55% and 88% of patients, respectively (relative risk [RR], 0.27 [95% confidence interval {CI}, 0.25-0.30]; P < .01); the antimicrobial regimen was adequate in 74% and 87% of patients, respectively (RR, 0.50 [95% CI, 0.45-0.55]; P < .01); duration of the prophylaxis was adequate in 44% and 55% of patients, respectively (RR, 0.80 [95% CI, 0.77-0.84]; P < .01); and the surgical site infection rates were 3.2% and 1.9%, respectively (RR, 0.59 [95% CI, 0.44-0.79]; P < .01). Antimicrobial expenditure was US$10,678.66 per 1,000 patient-days during the first stage and US$7,686.05 per 1,000 patient-days during the final stage (RR, 0.87 [95% CI, 0.86-0.89]; P<.01).

The intervention based on training and application of a protocol with an automatic stop of prophylaxis favored compliance with the hospital's current surgical antibiotic prophylaxis guidelines before the intervention, achieving significant reductions of surgical site infection rates and substantial savings for the healthcare system.

To compare the molecular characteristics of infection-derived (ID) isolates and intestinal colonization–derived (ICD) isolates of vancomycin-resistant enterococci (VRE) recovered from hospitalized patients.

A 12-month prospective cohort study.

A 1,000-bed teaching facility.

From January through December 2004, a total of 30 pairs of vanA-containing enterococcal isolates were collected from patients admitted to a teaching hospital in South Korea. Each pair comprised an ID and an ICD VRE isolate from the same patient. All VRE isolates were investigated on the basis of SmaI-restricted pulsed-field gel electrophoresis (PFGE) pattern, Tn1546type, and presence of the esp gene, including A and C repeat number variation.

Members of 19 pairs (63%) of VRE isolates were genetically indistinguishable from each other. The 11 patients for whom the molecular characteristics of the ID isolates differed from those of the ICD isolates had longer durations of hospitalization and intensive care unit (ICU) stay, compared with the other 19 patients.

These findings suggest the longer durations of hospitalization and ICU stay may be possible risk factors for colonization with multiple clones of VRE.