Potentially pathogenic bacteria in shower water and air of a stem cell transplant unit.

Potential pathogens from shower water and aerosolized shower mist (i.e., shower aerosol) have been suggested as an environmental source of infection for immunocompromised patients. To quantify the microbial load in shower water and aerosol samples, we used culture, microscopic, and quantitative PCR methods to investigate four shower stalls in a stem cell transplant unit at Barnes-Jewish Hospital in St. Louis, MO. We also tested membrane-integrated showerheads as a possible mitigation strategy. In addition to quantification, a 16S rRNA gene sequencing survey was used to characterize the abundant bacterial populations within shower water and aerosols. The average total bacterial counts were 2.2 x 10(7) cells/liter in shower water and 3.4 x 10(4) cells/m(3) in shower aerosol, and these counts were reduced to 6.3 x 10(4) cells/liter (99.6% efficiency) and 8.9 x 10(3) cells/m(3) (82.4% efficiency), respectively, after membrane-integrated showerheads were installed. Potentially pathogenic organisms were found in both water and aerosol samples from the conventional showers. Most notable was the presence of Mycobacterium mucogenicum (99.5% identity) in the water and Pseudomonas aeruginosa (99.3% identity) in the aerosol samples. Membrane-integrated showerheads may protect immunocompromised patients from waterborne infections in a stem cell transplant unit because of efficient capture of vast numbers of potentially pathogenic bacteria from hospital water. However, an in-depth epidemiological study is necessary to investigate whether membrane-integrated showerheads reduce hospital-acquired infections. The microbial load in shower aerosols with conventional showerheads was elevated compared to the load in HEPA-filtered background air in the stem cell unit, but it was considerably lower than typical indoor air. Thus, in shower environments without HEPA filtration, the increase in microbial load due to shower water aerosolization would not have been distinguishable from anticipated variations in background levels.

Evaluation of Clostridium difficile-associated disease pressure as a risk factor for C difficile-associated disease.

BACKGROUND: Colonization pressure has been identified as an important risk factor in the transmission of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus species, but the role of colonization pressure in the transmission of Clostridium difficile-associated disease (CDAD) is unclear. The purpose of this study was to evaluate CDAD pressure, a modified form of colonization pressure based on symptomatic CDAD cases, as a risk factor for CDAD. METHODS: Retrospective cohort and nested case-control studies of patients admitted to Barnes-Jewish Hospital from January 1, 2003, through December 31, 2003. Univariate analysis and multivariate logistic regression models were used to evaluate the role of CDAD pressure as a risk factor for CDAD. RESULTS: A total of 36 275 patients were included in the cohort, of which 382 had CDAD. The median CDAD pressure was higher for case patients than noncase patients (1.4 vs 0.3; P<.001), and only 1 patient with CDAD had a CDAD pressure of 0. In the nested case-control study, CDAD pressure remained an independent risk factor for CDAD after adjustment for demographics, severity of illness, medications received (chemotherapy, gastric acid suppressors, antidiarrheals or narcotics, and antibiotics), and abdominal procedures or surgery performed. CONCLUSIONS: The results of this study suggest that CDAD pressure may be an independent risk factor for CDAD. Future studies that evaluate risk of CDAD should control for CDAD pressure.

Prevalence of Clostridium difficile environmental contamination and strain variability in multiple health care facilities.

BACKGROUND: Clostridium difficile spores can contaminate the hospital environment. Little is known about the prevalence and strain variability of C. difficile environmental contamination in health care facilities. The objective of this study was to assess C. difficile environmental contamination at various health care facilities in a metropolitan area and determine if the North American pulsed field gel electrophoresis type 1 (NAP1) strain was present. METHODS: A cross-sectional pilot survey was conducted. Forty-eight environmental samples were collected from six health care facilities. Samples were cultured for the presence of C. difficile, and positive samples underwent pulsed field gel electrophoresis, toxinotyping, and detection of binary toxin and/or tcdC deletion. RESULTS: C. difficile was cultured from 13 of 48 (27%) samples. Rooms housing a patient with C. difficile-associated disease (CDAD) were more likely to be culture positive than non-CDAD patient rooms (100% vs. 33%; P < 0.01); C. difficile was not isolated outside of patient rooms (0 of 12 samples). The NAP1 epidemic strain was found in 5 out of 6 facilities. CONCLUSION: C. difficile spores frequently contaminated the hospital environment. Rooms with a CDAD patient were more likely to be contaminated than rooms without a CDAD patient. The NAP1 strain was prevalent throughout the metropolitan area.

To gown or not to gown: the effect on acquisition of vancomycin-resistant enterococci.

Infection-control recommendations include the use of gowns and gloves to prevent horizontal transmission of vancomycin-resistant enterococci (VRE). This study sought to determine whether the use of a gown and gloves gives greater protection than glove use alone against VRE transmission in a medical intensive care unit (MICU). From 1 July 1997 through 30 June 1998 and from 1 July 1999 through 31 December 1999, health care personnel and visitors were required to don gloves and gowns upon entry into rooms where there were patients infected with nosocomial pathogens. From 1 July 1998 through 30 June 1999, only gloves were required under these same circumstances. During the gown period, 59 patients acquired VRE (9.1 cases per 1000 MICU-days), and 73 patients acquired VRE during the no-gown period (19.6 cases per 1000 MICU-days; P<.01). The adjusted risk estimate indicated that gowns were protective in reducing VRE acquisition in an MICU with high VRE colonization pressure.

Stenotrophomonas maltophilia intestinal colonization in hospitalized oncology patients with diarrhea.

A 6-week surveillance study was performed to determine the prevalence of Stenotrophomonas maltophilia intestinal colonization among patients hospitalized in an oncology unit who developed diarrhea. Ninety-two stool samples obtained from 41 patients were cultured, and 4 patients (4 [9.5%] of 41 patients) had cultures that were positive for S. maltophilia. After controlling for duration of diarrhea, patients colonized with S. maltophilia had received a greater number of different types of antibiotics than noncolonized patients (5 vs. 3 different drugs; P=.04).

Clinical utility of blood cultures drawn from central vein catheters and peripheral venipuncture in critically ill medical patients.

STUDY OBJECTIVE: To determine the sensitivity, specificity, and positive and negative predictive values of blood cultures obtained through a central vein catheter compared with peripheral venipuncture. DESIGN: Prospective cohort study. SETTING: A medical ICU (19 beds) from a university-affiliated urban teaching hospital. PATIENTS: Between February 2001 and October 2001, 300 paired blood culture specimens were obtained from 119 patients (2.52 paired cultures per patient). INTERVENTION: Prospective patient surveillance and data collection. MEASUREMENTS AND MAIN RESULTS: Thirty-four paired culture results (11.3%; 95% confidence interval, 7.8 to 14.8%) were accepted as true-positives representing a true bacteremia. The sensitivity of catheter-drawn and peripheral venipuncture samples was 82.4% and 64.7%, respectively, and specificity was 92.5% and 95.9%. The positive predictive value was 58.3% for catheter-drawn samples and 66.7% for peripheral venipuncture samples, and the respective negative predictive values were 97.6% and 95.5%. CONCLUSIONS: In critically ill medical patients, the negative predictive value of blood samples obtained by catheter draw or peripheral venipuncture for suspected bloodstream infection is good. However, the sensitivity of blood samples obtained by either catheter draw or peripheral venipuncture alone is not adequate to recommend the elimination of blood samples obtained from the other site. Clinicians should also be aware that additional blood samples may be necessary when interpreting positive blood culture results for common skin or central vein catheter contaminants.

The effect of an education program on the incidence of central venous catheter-associated bloodstream infection in a medical ICU.

OBJECTIVE: To determine whether an education initiative could decrease the rate of catheter-associated bloodstream infection. DESIGN: Preintervention and postintervention observational study. SETTING: The 19-bed medical ICU in a 1,400-bed university-affiliated urban teaching hospital. PATIENTS: Between January 2000 and December 2003, all patients admitted to the medical ICU were surveyed prospectively for the development of catheter-associated bloodstream infection. INTERVENTION: A mandatory education program directed toward ICU nurses and physicians was developed by a multidisciplinary task force to highlight correct practices for the prevention of catheter-associated bloodstream infection. The program consisted of a 10-page self-study module on risk factors and practice modifications involved in catheter-related bloodstream infections and in-services at scheduled staff meetings. Each participant was required to complete a pretest before reviewing the study module and an identical test after completion of the study module. Fact sheets and posters reinforcing the information in the study module were also posted throughout the ICU. MEASUREMENTS AND MAIN RESULTS: Seventy-four episodes of catheter-associated bloodstream infection occurred in 7,879 catheter-days (9.4 per 1,000 catheter-days) in the 24 months before the introduction of the education program. Following implementation of the intervention, the rate of catheter-associated bloodstream infection decreased to 41 episodes in 7,455 catheter days (5.5 per 1,000 catheter-days) [p = 0.019]. The estimated cost savings secondary to the decreased rate of catheter-associated bloodstream infection for the 24 months following introduction of the education program was between $103,600 and $1,573,000. CONCLUSIONS: An intervention focused on the education of health-care providers on the prevention of catheter-associated bloodstream infections may lead to a dramatic decrease in the incidence of primary bloodstream infections. Education programs may lead to a substantial decrease in medical-care costs and patient morbidity attributed to central venous catheterization when implemented as part of mandatory training.

Risk factors for Stenotrophomonas maltophilia bacteremia in oncology patients: a case-control study.

OBJECTIVE: To characterize risk factors for Stenotrophomonas maltophilia bloodstream infection in oncology patients. DESIGN: A 3:1 case-control study. SETTING: Stem Cell Transplant and Leukemic Center at Barnes-Jewish Hospital (St. Louis), a 1,442-bed, tertiary-care teaching hospital with a 26-bed transplantation ward. METHOD: From, June 1999 to April 2001, 13 patients with S. maltophilia bacteremia were compared with 39 control-patients who were on the transplantation unit on the same day as the case-patients' positive blood cultures. Information collected included patient demographics, medical history, history of transplantation, transplantation type, graft versus host disease, neutropenia, antibiotic use, chemotherapy, mucositis, diarrhea, the presence of central venous catheter(s), cultures, and concomitant infections. RESULTS: Significant risk factors for S. maltophilia bacteremia included severe mucositis (7 [53.8%] of 13 vs 8 [20.5%] of 39; P = .034), diarrhea (7 [53.8%] of 13 vs 8 [20%] of 39; P = .034), and the use of metronidazole (9 [69.2%] of 13 vs 8 [20.5%] of 39; P = .002). In addition, the number of antibiotics used (median, 9 vs 5; P < .001), duration of mucositis (median, 29 vs 15 days; P = .032), and length of hospital stay (median, 34 vs 22 days; P = .017) were significantly different between case- and control-patients. Nine S. maltophilia isolates tested by pulsed-field gel electrophoresis were found to be distinctly different. CONCLUSION: Interventions to ameliorate the severity of mucositis, reduce antibiotic pressure, prevent diarrhea, and promote meticulous central venous catheter care may help prevent S. maltophilia bloodstream infection in oncology patients. The role of gastrointestinal tract colonization as a potential source of S. maltophilia bacteremia in oncology patients deserves further investigation.

Risk factors for surgical site infection in spinal surgery.

OBJECT: The objective of this study was to identify specific independent risk factors for surgical site infections (SSIs) occurring after laminectomy or spinal fusion. METHODS: The authors performed a retrospective case-control study of data obtained in patients between 1996 and 1999 who had undergone laminectomy and/or spinal fusion. Forty-one patients with SSI or meningitis were identified, and data were compared with those acquired in 178 uninfected control patients. Risk factors for SSI were determined using univariate analyses and multivariate logistic regression. The spinal surgery-related SSI rate (incisional and organ space) during the 4-year study period was 2.8%. Independent risk factors for SSI identified by multivariate analysis were postoperative incontinence (odds ratio [OR] 8.2, 95% confidence interval [CI] 2.9-22.8), posterior approach (OR 8.2, 95% CI 2-33.5), procedure for tumor resection (OR 6.2, 95% CI 1.7-22.3), and morbid obesity (OR 5.2, 95% CI 1.9-14.2). In patients with SSI the postoperative hospital length of stay was significantly longer than that in uninfected patients (median 6 and 3 days, respectively; p < 0.001) and were readmitted to the hospital for a median additional 6 days for treatment of their infection. Repeated surgery due to the infection was required in the majority (73%) of infected patients. CONCLUSIONS: Postoperative incontinence, posterior approach, surgery for tumor resection, and morbid obesity were independent risk factors predictive of SSI following spinal surgery. Interventions to reduce the risk for these potentially devastating infections need to be developed.

Assessing colectomies due to Clostridium difficile infection: increases in the community, but not in the referral center.

To investigate an increase in CDI-related colectomies, electronically available data were used to identify patients who underwent colectomy and were diagnosed with Clostridium difficile infection (CDI), with chart review to determine whether the colectomy was for CDI. The investigation found an increase in CDI-related colectomies for CDI not associated with the study institution. Electronically available data facilitated surveillance for severe CDI.

Hospital-onset Clostridium difficile infection rates in persons with cancer or hematopoietic stem cell transplant: a C3IC network report.

A multicenter survey of 11 cancer centers was performed to determine the rate of hospital-onset Clostridium difficile infection (HO-CDI) and surveillance practices. Pooled rates of HO-CDI in patients with cancer were twice the rates reported for all US patients (15.8 vs 7.4 per 10,000 patient-days). Rates were elevated regardless of diagnostic test used.

Risk factors associated with methicillin-resistant Staphylococcus aureus colonization on hospital admission among oncology patients.

A nested case-control study at a tertiary care facility was conducted to assess potential risk factors for colonization with methicillin-resistant Staphylococcus aureus (MRSA) on admission among oncology patients. Risk factors for any S aureus and MRSA colonization on admission in oncology patients are consistent with previous studies in general populations. In addition, recent chemotherapy as a risk factor is a unique finding in this population.

Hospital-associated Clostridium difficile infection: is it necessary to track community-onset disease?

OBJECTIVES: To compare Clostridium difficile infection (CDI) rates determined with use of a traditional definition (ie, with healthcare-onset CDI defined as diagnosis of CDI more than 48 hours after hospital admission) with rates determined with use of expanded definitions, including both healthcare-onset CDI and community-onset CDI, diagnosed within 48 hours after hospital admission in patients who were hospitalized in the previous 30 or 60 days, and to determine whether differences exist between patients with CDI onset in the community and those with CDI onset in a healthcare setting. DESIGN: Prospective cohort. SETTING: Tertiary acute care facility. PATIENTS: General medicine patients who received a diagnosis of CDI during the period January 1, 2004, through December 31, 2005. METHODS: CDI was classified as healthcare-onset CDI, healthcare facility-associated CDI after hospitalization within the previous 30 days, and/or healthcare facility-associated CDI after hospitalization within the previous 60 days. Patient demographic characteristics and medication exposures were obtained. The CDI incidence with use of each definition, CDI rate variability, patient demographic characteristics, and medication exposures were compared. RESULTS: The healthcare-onset CDI rate (1.6 cases per 1,000 patient-days) was significantly lower than the 30-day healthcare facility-associated CDI rate (2.4 cases per 1,000 patient-days; P< .01) and the 60-day healthcare facility-associated CDI rate (2.6 cases per 1,000 patient-days; P< .01). There was good correlation between the healthcare-onset CDI rate and both the 30-day (correlation, 0.69; P< .01) and 60-day (correlation, 0.70; P< .01) healthcare facility-associated CDI rates. There were no months in which the CDI rate was more than 3 standard deviations from the mean. Compared with patients with healthcare-onset CDI, patients with community-onset CDI were less likely to have received a fourth-generation cephalosporin (P= .02) or intravenous vancomycin (P+ .01) during hospitalization. CONCLUSIONS: Compared with the traditional definition, expanded definitions identify more patients with CDI. There is good correlation between traditional and expanded CDI definitions; therefore, it is unclear whether expanded surveillance is necessary to identify an abnormal change in CDI rates. Cases that met the expanded definitions were less likely to have occurred in patients with fourth-generation cephalosporin and vancomycin exposure.

Identification of a pseudo-outbreak of Clostridium difficile infection (CDI) and the effect of repeated testing, sensitivity, and specificity on perceived prevalence of CDI.

OBJECTIVE: To describe a pseudo-outbreak of Clostridium difficile infection (CDI) caused by a faulty toxin assay lot and to determine the effect of sensitivity, specificity, and repeated testing for C. difficile on perceived CDI burden, positive predictive value, and false-positive results. DESIGN: Outbreak investigation and criterion standard. PATIENTS: Patients hospitalized at a tertiary care hospital who had at least 1 toxin assay for detection of C. difficile performed during the period from July 1, 2004, through June 30, 2006. METHODS: The run control chart method and the chi(2) test were used to compare CDI rates and the proportion of positive test results before, during, and after the pseudo-outbreak. The effect of repeated testing was evaluated by using 3 hypothetical models with a sample of 10,000 patients and various assay sensitivity and specificity estimates. RESULTS: In November of 2005, the CDI rate at the hospital increased from 1.5 to 2.6 cases per 1,000 patient-days (P < .01), and the proportion of positive test results increased from 13.6% to 22.1% (P < .01). An investigation revealed a pseudo-outbreak caused by a faulty toxin assay lot. A decrease of only 1.2% in the specificity of the toxin assay would result in a 32% increase in perceived incidence of CDI at this institution. When calculated by use of the manufacturer's stated specificity and sensitivity and this institution's testing practices, the positive predictive value of the test decreased from 80.6% to 4.1% for patients who received 3 tests. CONCLUSION: Specificity is as important as sensitivity when testing for CDI. False-positive CDI cases can drain hospital resources and adversely affect patients. Repeated testing for C. difficile should be performed with caution.

Hospital-associated costs due to surgical site infection after breast surgery.

OBJECTIVE: To determine the attributable costs associated with surgical site infection (SSI) following breast surgery. DESIGN AND SETTING: Cost analysis of a retrospective cohort in a tertiary care university hospital. PATIENTS: All persons who underwent breast surgery other than breast-conserving surgery from July 1, 1999, through June 30, 2002. MAIN OUTCOME MEASURES: Surgical site infection and hospital costs. Costs included all those incurred in the original surgical admission and any readmission(s) within 1 year of surgery, inflation adjusted to US dollars in 2004. RESULTS: Surgical site infection was identified in 50 women during the original surgical admission or at readmission to the hospital within 1 year of surgery (N = 949). The incidence of SSI was 12.4% following mastectomy with immediate implant reconstruction, 6.2% following mastectomy with immediate reconstruction using a transverse rectus abdominis myocutaneous flap, 4.4% following mastectomy only, and 1.1% following breast reduction surgery. Of the SSI cases, 96.0% were identified at readmission to the hospital. Patients with SSI had crude median costs of $16 882 compared with $6123 for uninfected patients. After adjusting for the type of surgical procedure(s), breast cancer stage, and other variables associated with significantly increased costs using feasible generalized least squares, the attributable cost of SSI after breast surgery was $4091 (95% confidence interval, $2839-$5533). CONCLUSIONS: Surgical site infection after breast cancer surgical procedures was more common than expected for clean surgery and more common than SSI after non-cancer-related breast surgical procedures. Knowledge of the attributable costs of SSI in this patient population can be used to justify infection control interventions to reduce the risk of infection.

Risk factors for surgical site infection after major breast operation.

BACKGROUND: Understanding surgical site infection (SSI) risk factors after breast operation is essential to develop infection-prevention strategies and improve surgical outcomes. METHODS: We performed a retrospective case-control study with subjects selected from a cohort of mastectomy, breast reconstruction, and reduction surgical patients between January 1998 and June 2002 at a university-affiliated hospital. SSI cases within 1 year after operation were identified using ICD-9-CM diagnosis codes for wound infection and complication or positive wound cultures, or both. Medical records of 57 patients with breast SSI and 268 randomly selected uninfected control patients were reviewed. Multivariate logistic regression was used to identify independent risk factors for SSI. RESULTS: Significant independent risk factors for breast incisional SSI included insertion of a breast implant or tissue expander (odds ratio [OR] = 5.3; 95% CI, 2.5 to 11.1), suboptimal prophylactic antibiotic dosing (OR = 5.1; 95% CI, 2.5 to 10.2), transfusion (OR = 3.4; 95% CI, 1.3 to 9.0), mastectomy (OR = 3.3; 95% CI, 1.4 to 7.7), previous chest irradiation (OR = 2.8; 95% CI, 1.2 to 6.5), and current or recent smoking (OR = 2.1; 95% CI, 0.9 to 4.9). Local infiltration of an anesthetic agent was associated with substantially reduced odds of SSI (OR = 0.4; 95% CI, 0.1 to 0.9). CONCLUSIONS: Suboptimal prophylactic antibiotic dosing is a potentially modifiable risk factor for SSI after breast operation. SSI risk was increased in patients undergoing mastectomy and in patients who had an implant or tissue expander placed during operation. This information can be used to develop a specific risk stratification index to predict SSI and infection-preventive strategies tailored for breast surgery patients.

Risk factors for surgical site infection following orthopaedic spinal operations.

BACKGROUND: Surgical site infections are not uncommon following spinal operations, and they can be associated with serious morbidity, mortality, and increased resource utilization. The accurate identification of risk factors is essential to develop strategies to prevent these potentially devastating infections. We conducted a case-control study to determine independent risk factors for surgical site infection following orthopaedic spinal operations. METHODS: We performed a retrospective case-control study of patients who had had an orthopaedic spinal operation performed at a university-affiliated tertiary-care hospital from 1998 to 2002. Forty-six patients with a superficial, deep, or organ-space surgical site infection were identified and compared with 227 uninfected control patients. Risk factors for surgical site infection were determined with univariate analyses and multivariate logistic regression. RESULTS: The overall rate of spinal surgical site infection during the five years of the study was 2.0% (forty-six of 2316). Univariate analyses showed serum glucose levels, preoperatively and within five days after the operation, to be significantly higher in patients in whom surgical site infection developed than in uninfected control patients. Independent risk factors for surgical site infection that were identified by multivariate analysis were diabetes (odds ratio = 3.5, 95% confidence interval = 1.2, 10.0), suboptimal timing of prophylactic antibiotic therapy (odds ratio = 3.4, 95% confidence interval = 1.5, 7.9), a preoperative serum glucose level of >125 mg/dL (>6.9 mmol/L) or a postoperative serum glucose level of >200 mg/dL (>11.1 mmol/L) (odds ratio = 3.3, 95% confidence interval = 1.4, 7.5), obesity (odds ratio = 2.2, 95% confidence interval = 1.1, 4.7), and two or more surgical residents participating in the operative procedure (odds ratio = 2.2, 95% confidence interval = 1.0, 4.7). A decreased risk of surgical site infection was associated with operations involving the cervical spine (odds ratio = 0.3, 95% confidence interval = 0.1, 0.6). CONCLUSIONS: Diabetes was associated with the highest independent risk of spinal surgical site infection, and an elevated preoperative or postoperative serum glucose level was also independently associated with an increased risk of surgical site infection. The role of hyperglycemia as a risk factor for surgical site infection in patients not previously diagnosed with diabetes should be investigated further. Administration of prophylactic antibiotics within one hour before the operation and increasing the antibiotic dosage to adjust for obesity are also important strategies to decrease the risk of surgical site infection after spinal operations.

A technology-assisted approach for discontinuing contact isolation.

While contact isolation can be an effective tool in reducing the transmission of nosocomial methicillin-resistant Staphylococcus aureus (MRSA), it can increase costs and may decrease the quality of patient care. Therefore, it is important to insure that only patients who need contact precautions are isolated. We describe a simple automated report to help infection control practitioners pro-actively identify patients that may no longer need isolation.