Diagnosis of MRSA with neural networks and logistic regression approach.

Antibiotic-resistant pathogens are increasingly prevalent in the hospitals and community. A timely and accurate diagnosis of the infection would greatly help physicians effectively treat patients. In this research we investigate the potential of using neural networks (NN) and logistic regression (LR) approach in diagnosing methicillin-resistant Staphylococcus aureus (MRSA). Receiver-Operating Characteristic (ROC) curve and the cross-validation method are used to compare the performances of both systems. We found that NN is better than the logistic regression approach, in terms of both the discriminatory power and the robustness. With modeling flexibility inherent in its techniques, NN is effective in dealing with MRSA and other classification problems involving large numbers of variables and interaction complexity. On the other hand, logistic regression in our case is slightly inferior, offers more clarity and less perplexity. It could be a method of choice when fewer variables are involved and/or justification of the results is desired.

Feedback to nursing staff as an intervention to reduce catheter-associated urinary tract infections.

Because of high incidence of catheter-related urinary tract infections (UTIs) in our Veterans Affairs medical center, we began providing nursing staff with unit-specific UTI rates. In our preintervention period, the first quarter of 1995, 38 infections occurred in 1186 catheter-patient-days or 32/1000 catheter-patient-days (95% CI, 22.9-43.7). Thereafter, nursing staff members were provided with a quarterly report with catheter-related UTI rates depicted graphically by unit. In the 18 months after this intervention, the mean UTI rate decreased to 17.4/1000 catheter-patient-days (95% CI, 14.6-20.6, P =.002). We estimated a cost savings of $403,000. We conclude that unit-specific feedback of nosocomial UTI rates to nursing staff is a highly effective method of reducing infection rates and reducing costs associated with nosocomial UTI.

Risk of infection due to central venous catheters: effect of site of placement and catheter type.

OBJECTIVE: To determine the influence of catheter site and type (single- vs triple-lumen) on infection rates associated with central venous catheterization. DESIGN: Prospective observational study of all nontunneled central venous catheters over a 28-month period. Data collected included patient characteristics, insertion site, catheter type, and receipt of parenteral nutrition. End points were clinical infection (bacteremia or site infection) and catheter contamination (clinical infection or colonization with >15 colonies on semiquantitative culture). SETTING: Medical-surgical wards of Veterans' Affairs hospital. RESULTS: Three hundred catheters were inserted into 204 patients. Seventy percent were inserted into upper-body sites, and 30% were inserted into the femoral vein. Forty-five percent were triple-lumen catheters. Bacteremia occurred in 2.7% of catheter insertions; insertion-site infections developed in 1.3%, and catheter colonization developed in 12%. Catheter contamination was associated with emergent insertion (odds ratio [OR], 6.2; 95% confidence interval [CI95], 1.1-36.7; P=.04) by logistic regression and with femoral location (hazard, 4.2; CI95, 2.0-8.8; P=.0001) and history of transplantation (hazard, 2.8; CI95, 1.1-6.7; P=.024) by Cox regression. Clinical infection was not associated with any of the risk factors evaluated, although there was a trend for association with femoral location by Cox regression (hazard, 4.7; CI95, 0.82-26; P=.08). We did not identify an association between infection and use of triple-lumen catheters or parenteral nutrition. CONCLUSION: Our data support an association between intravenous catheter contamination and insertion at a femoral site.

Infection and colonization with vancomycin-resistant Enterococcus faecium in an acute care Veterans Affairs Medical Center: a 2-year survey.

BACKGROUND: After our first known patient with vancomycin-resistant enterococci (VRE) infection was admitted in 1993, we observed a gradual increase in infections and colonization caused by this organism. Thus we initiated a prospective study to quantitate the incidence of VRE infection versus colonization, to identify risk factors for VRE, and to define the natural history of VRE colonization among our patients. METHODS: Stool/rectal cultures were performed for patients admitted to the intensive care units at the time of admission and weekly thereafter. Patients found to be carrying VRE were followed with cultures every 2 weeks, and this protocol was continued after transfer to the medical-surgical wards. A surveillance form was initiated on each VRE patient and included demographics, underlying diseases, and risk factors. Environmental cultures in the intensive care units were randomly performed. Patients with positive cultures were isolated. RESULTS: During a 27-month period, 210 patients were found to be colonized or infected with VRE. Ages ranged from 35 to 97 years; the mean age was 65 years. Fourteen percent (29 of 210) of the patients were VRE positive on admission. Nosocomial colonization or infection occurred at an average of 28 days after admission. Seventeen percent (25 of 216) of patients cleared VRE during their hospital stay; 19% (40 of 210) developed 47 infections. One third of infections involved the urinary tract. Liver transplantation, chemotherapy, and total parenteral nutrition were each associated with infection. CONCLUSION: Routine measures as advocated by the Centers for Disease Control and Prevention were not effective in controlling VRE in our patient population.

Complications related to intravenous midline catheter usage. A 2-year study.

The introduction of the Landmark midline catheter (Menlo, Co., CA) brought an alternative to central line catheter placement for prolonged intravenous access. The study was initiated in 1993 to observe for complications, including hypersensitivity-like reactions. The authors hypothesized this i.v. modality would decrease the need for central i.v. lines and accompanying complications. At the time of catheter insertion, the i.v. team nurses completed a survey form that included demographics, underlying disease, and risk factors for infection. The catheter tip was cultured at the time of removal. In the second phase of the study, the authors focused specifically on hypersensitivity-like reactions. During a 2-year period, 248 patients had 334 midline catheters. Patient ages ranged from 23 to 98 years (mean age, 65 years). The bacteremia rate was 0.3%; the colonization rate was 0.9%. Factors associated with infection/ colonization included: length of time in place, chemotherapy, and lack of antibiotic administration. In the second phase of the study, during which an additional 170 catheters were placed in 131 patients, no hypersensitivity-like reactions were noted. The midline catheter appears to be a safe method of i.v. fluid administration for patients with limited peripheral vein access who need extended i.v. therapy.

Nosocomial legionnaires' disease discovered in community hospitals following cultures of the water system: seek and ye shall find.

BACKGROUND: The reservoir for hospital-acquired legionnaires' disease is the water distribution system. The Allegheny County (Pa.) Health Department recommended environmental cultures for all health care facilities for the prevention of hospital-acquired Legionella infection including facilities with no known cases of legionnaires' disease. METHODS: Environmental cultures of hot water tanks, faucets, and showerheads were performed in six health care facilities according to health department guidelines. If hot water tanks, faucets, or showerheads yielded Legionella, monitoring with Legionella culture and urinary antigen was performed for all cases of nosocomial pneumonia. RESULTS: Legionella was isolated from the water distribution system in 83% (five of six) of facilities. Three facilities dropped out of the study; two decided to disinfect the water and one had no Legionella in the water system. The other three facilities all discovered cases of legionnaires' disease during the 1-year study period after introduction of Legionella testing. L. pneumophilia, serogroups 1, 3, and 5, caused 12 cases of hospital-acquired legionnaires' disease. Positive diagnostic tests included: 10 of 12 (83%) urinary antigen, 6 of 8 (75%) respiratory cultures, and 2 of 5 (40%) serology. Molecular typing confirmed that the source of infection was the water supply in two hospitals. CONCLUSION: Routine environmental cultures for Legionella in the water distribution system are recommended even if the hospital had not previously recognized cases of hospital acquired legionnaires' disease. The Allegheny County Health Department guidelines were inexpensive to implement and resulted in the discovery of cases that would have otherwise been undiagnosed.

Controlling Legionella in hospital water systems: experience with the superheat-and-flush method and copper-silver ionization.

OBJECTIVE: To evaluate the effect of copper-silver ionization on Legionella colonization and nosocomial legionnaires' disease and to compare the efficacy of metal ions versus the superheat-and-flush method of disinfection. DESIGN: Prospective determination over a 36-month period of copper and silver ion concentrations in the recirculating hot-water system, Legionella colonization of the hospital water distribution system, and cases of nosocomial legionnaires' disease. Retrospective comparison of results with the previous 13 years, during which the superheat-and-flush method was used. SETTING: The Pittsburgh Veterans' Affairs Health Care System (University Drive Division) acute-care hospital. INTERVENTION: Three copper-silver ionization systems were installed on the hot-water distribution system in November 1994. RESULTS: The average number of cases of legionnaires' disease per year and the percentage of distal sites positive for Legionella pneumophila for the superheat-and-flush method versus the copper-silver ionization method was six cases with 15% positivity versus two cases with 4% positivity, respectively. The reduction in Legionella colonization after copper-silver ionization was significant (P<.05) compared to the superheat and flush. Mean copper and silver ion concentrations (mg/L) were 0.29 and 0.054 from hot-water tanks, and 0.17 and 0.04 from distal outlets, respectively. CONCLUSIONS: We conclude that a properly maintained and monitored copper-silver ionization system was more effective than the superheat-and-flush method for reducing the recovery of Legionella from the hospital water distribution system.

Managing organisational change: the "gendered" organisation of space and time.

PIP: Although the Bangladesh Rural Advancement Committee (BRAC) maintains a strong commitment to gender equity in its anti-poverty programs, a conservative external environment often impedes efforts to make its organizational structure consistent with this commitment. For example, BRAC's approach to organizing its field operations has been to abolish the distinction between home and office. BRAC's female employees live with male colleagues in their rural offices, travel long distances on bicycles and motorcycles, and reject the sari--practices that are antithetical to the prevailing culture and place tremendous pressure on these field workers. The high work intensity, need to work beyond normal business hours, and lack of on-site child care subjects married female employees to hostility from their husbands and relatives. Single female employees are often regarded as unmarriagable because of their divergent life-styles. Although BRAC makes provisions for employees to take leave for family responsibilities, staff who access this benefit are viewed as more committed to family than their work. The sexual activities of female--but not male--employees are scrutinized. Despite these contradictions, BRAC's innovative arrangements model a new form of gender relations in rural areas. BRAC is enabling its young women employees to postpone marriage and demonstrate a nontraditional role. The extent to which BRAC should take responsibility for compensating for the constraints imposed on women by patriarchy remains problematic. Working conditions could be improved, however, by allowing women to be near their families, domesticating the work environment, and respecting women's personal lives.^ieng

Reduction in nosocomial intravenous device-related bacteremias after institution of an intravenous therapy team.

In November 1991, an intravenous therapy team was instituted on the medical/surgical wards of a 330-bed acute care Veteran's Affairs Medical Center. Before this, IV insertions/care were performed by house officers and registered nurses. Intravenous-related bacteremias decreased from 4.6/1000 patient discharges to 1.5/1000 patient discharges (P < 0.005) after institution of the IV team. There was no significant difference in the IV-related bacteremia rate in critical care areas where housestaff and nurses continued to care for lines (7.9 versus 6.2 per 1000 patient discharges). The expertise of an IV therapy team is effective in decreasing morbidity and mortality related to IV insertions. The authors estimated a savings of $124,906 when considering reduction of bacteremias.

An outbreak of infusion-related Klebsiella pneumoniae bacteremia in a liver transplantation unit.

Over a 1-month period, there were five episodes of infusion-related Klebsiella pneumoniae bacteremia in four liver transplantation patients housed in the same ward. Investigation of nursing practices revealed that a common normal-saline bag, to which intravenous (iv) tubing and a stopcock were attached, was used to flush iv catheters. The iv tubing and stopcock were changed at sporadic intervals. Cultures of the normal saline and iv equipment yielded K. pneumoniae, which had the same susceptibility pattern as the patients' isolates. Isolates recovered during the outbreak from the patients and from the iv saline/equipment were of the same strain, as determined by pulsed-field electrophoresis of Xba I-digested genomic DNA. Termination of the practice of flushing iv catheters with a common normal-saline bag halted the outbreak.

Prevalence of hepatitis C infection in health care workers affiliated with a liver transplant center.

The risk of hepatitis C to liver transplantation health care workers has not been identified. We compared the occupational risk of hepatitis C in health care workers associated with liver transplantation with risk of health care workers affiliated with the same institutions but not involved in transplantations. Health care workers were recruited from 2 transplant centers. Participation was voluntary; results were confidential. An occupational and health history questionnaire was completed and blood was donated for testing. Health care workers were categorized into 3 groups according to risk for hepatitis C infection: very high, high, and low risk. A total of 241 health care workers were recruited from 2 transplant centers. Fifty-nine percent (142/241) were female; mean age was 38.7 years. Health care workers included: 48.5% (117/241) nurses, 24.9% (60/241) physicians, and 17% (42/241) laboratory personnel. The mean number of years in their occupation was 13.5 years (range < 1 year to 38 years). Twenty-four percent (57/241) were categorized in a very high risk occupation for hepatitis C, 66% (158/241) in a high risk occupation, and 10.8% (26/241) in a low risk occupation. A total of 2.1% (5/241) of health care workers were reactive to hepatitis C by enzyme immunosorbent assay; three of these were positive by polymerase chain reaction testing. Of the 3, none had a history of hepatitis or transfusion. However, 5.3% (3/57) of health care workers involved with liver transplantation were infected, as compared with 0% (0/184) who were not (P = 0.013). We conclude that health care workers associated with liver transplantation may be at a higher risk for hepatitis C when compared with health care workers not associated with transplantation.

Nosocomial infections in the human immunodeficiency virus-infected patient: a two-year survey.

BACKGROUND: Because HIV-infected patients are often hospitalized and have major defects in host defenses, we surveyed all HIV-infected patients admitted to our institution to determine incidence of infections and to risk factors for nosocomial infections. METHODS: All patients admitted during a 2-year period were monitored for nosocomial infections until their discharge, death, or transfer. Categoric data were evaluated with the Fisher Exact Test or chi 2 test. Continuous variables were compared with the t test or Mann-Whitney test. RESULTS: Ten percent of patient admissions (22/210) resulted in 32 nosocomial infections. Risk factors included longer hospitalization (29.8 vs 10.8 days), urinary catheters (35% vs 11%), gastrointestinal procedures (23% vs 3%), and vascular access (41% vs 19%). The most frequent etiologic agents were gram-positive organisms, primarily Staphylococcus species (44% [14/32]). CONCLUSION: Nosocomial infection rates for the HIV-infected patient were higher than the overall infection rate. Agents with broad-spectrum activity against gram-positive organisms, such as vancomycin, should be considered during the wait for culture results.

Adult respiratory distress syndrome associated with epidural fentanyl infusion.

OBJECTIVE: To determine the cause of unexplained postoperative adult respiratory distress syndrome (ARDS). DESIGN: Case-control study of postoperative ARDS. SETTING: Intensive care unit (ICU) of a Veterans Affairs hospital. PATIENTS: Six postoperative patients recovering from uncomplicated vascular or cardiothoracic surgery developed unexplained ARDS. Controls were 17 patients having similar procedures without the development of ARDS. INTERVENTION: Infusion of fentanyl with a tamper-proof device. MEASUREMENTS AND MAIN RESULTS: Development of ARDS. ARDS began 1 to 4 days after surgery, was characterized by maximum alveolar-arterial oxygen gradient that ranged from 232 to 544 torr (30.9 to 72.5 kPa), and was associated with death of two patients. We observed no association with patient location before ARDS onset, nonanalgesic medication administered, staff assignment, or mode of respiratory therapy. All six patients who developed unexplained ARDS had received epidural fentanyl compared with none of 17 control patients without ARDS (p = .0002). We instituted a tamper-proof mode of parenteral fentanyl administration, and subsequently observed one case of ARDS in 26 consecutive surgical patients (p = .000014). CONCLUSIONS: Based on these findings, as well as a prior history of fentanyl theft at our institution, we conclude that tampering with fentanyl infusate was responsible for the ARDS epidemic that we observed.

Infection with methicillin-resistant Staphylococcus aureus among hospital employees.

OBJECTIVE: To describe the spectrum of clinical infection caused by methicillin-resistant Staphylococcus aureus (MRSA) in healthcare workers. DESIGN: Case series. SETTING: Two Veterans Affairs hospitals in which methicillin-resistant S aureus (MRSA) is endemic. PATIENTS: Five employees presenting to employee health or infectious disease clinic. RESULTS: All employees had had direct exposure to patients colonized with MRSA. Employee infections included cellulitis, impetigo, folliculitis, paronychia, and conjunctivitis. MRSA was isolated from all clinically infected sites and from the anterior nares of two employees. Three employees received a variety of ineffective oral antimicrobials before MRSA was recognized as the causative agent. All infections responded to appropriate therapy. CONCLUSIONS: Employees of hospitals with endemic MRSA may acquire MRSA infection. Presentation in our employees was that of relatively uncomplicated soft tissue infection, but several employees received inappropriate therapy before bacteriologic diagnosis. We recommend that culture and susceptibility testing be obtained prior to institution of therapy when hospital employees present with soft tissue infection.

Bacteremia in a long-term-care facility: a five-year prospective study of 163 consecutive episodes.

The clinical features, microbiological characteristics, and outcomes of 163 episodes of bacteremia occurring at a long-term-care facility were evaluated. The rate of nosocomial bacteremia increased from 0.20 to 0.36 cases/1,000 patient-days from 1985 to 1989; there was a parallel increase in the rate of all nosocomial infections combined. Bacteremia was documented in 6.5% of all hospital-acquired infections. The majority of isolates were gram-negative, and Providencia stuartii was the most common gram-negative species. Staphylococcus aureus was the most frequent isolate; one-third of S. aureus strains were resistant to methicillin. Bacteremia was polymicrobial in 36 episodes (22%), 14 of which involved an enterococcal species. Portals of entry included the urinary tract (55%), the respiratory tract (11%), and soft tissue (9%). Overall mortality was 21.5%. Death was significantly associated with residence on the intermediate-care unit, the presence of a respiratory infection, a change in mental status, and relatively recent admission. Optimal management of bacterial infection in a long-term-care setting requires the availability of blood culture results. Initial decisions about antibiotic therapy should be made in light of the likelihood of infection with multiresistant organisms and of polymicrobial infection.

Association with prior fluoroquinolone therapy of widespread ciprofloxacin resistance among gram-negative isolates in a Veterans Affairs medical center.

We performed a case-control study of risk factors for the acquisition of ciprofloxacin-resistant gram-negative isolates in a Veterans Affairs medical center. Sixty-five patients with resistant isolates and 50 control patients were identified. Prior fluoroquinolone use was significantly more frequent among patients with resistant isolates than it was among controls (58 versus 20%; P = 0.0001). The association with prior quinolone use was stronger in the long-term-care division (81 versus 32%; P = 0.0005) than it was in the acute-care division (29 versus 0%; P = 0.015). On multivariate analysis, prior receipt of a fluoroquinolone was the single most significant risk factor for isolation of a ciprofloxacin-resistant gram-negative organism (P = 0.0001).