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W R Jarvis

Publications and source records attributed to W R Jarvis.

At least 55 records · Page 3Linked to original sources
PubMed2001

Comparison of serum and cell-specific cytokines in humans.

Cytokines function at the cellular, microenvironmental level, but human cytokine assessment is most commonly done at the macro level, by measuring serum cytokines. The relationships between serum and cellular cytokines, if there are any, are undefined. In a study of hospitalized patients in Malawi, we compared cytometrically assessed, cell-specific cytokine data to serum interleukin 2 (IL-2), IL-4, IL-6, IL-8, IL-10, gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) levels in 16 children and 71 (IL-2, -4, -6, -10) or 159 (IL-8, IFN-gamma, and TNF-alpha) adults, using Wilcoxon rank sum tests and Pearson's (r(p)) and Spearman's (r(s)) rank correlations. For the entire study group, correlations between identical serum and cellular cytokines mainly involved IL-8 and IFN-gamma, were few, and were weakly positive (r < 0.40). Blood culture-positive persons had the most and strongest correlations, including those between serum IL-2 levels and the percentages of lymphocytes spontaneously making IL-2 (r(s) = +0.74), serum IL-8 levels and the percentages of lymphocytes spontaneously making IL-8 (r(p) = +0.66), and serum IL-10 levels and the percentages of CD8(+) T cells making TNF-alpha (r(p) = +0.89). Human immunodeficiency virus (HIV)-positive persons had the next largest number of correlations, including several serum IL-8 level correlations, correlation of serum IL-10 levels with the percentages of lymphocytes producing induced IL-10 (r(s) = +0.36), and correlation of serum IFN-gamma levels and the percentages of lymphocytes spontaneously making both IL-6 and IFN-gamma in the same cell (r(p) = +0.59). HIV-negative, malaria smear-positive, and pediatric patients had few significant correlations; for the second and third of these subgroups, serum IL-8 level was correlated with the percentage of CD8(-) T cells producing induced IL-8 (r(s) = +0.40 and r(s) = +0.56, respectively). Thus, the strength of associations between serum and cellular cytokines varied with the presence or absence of bloodstream infection, HIV status, and perhaps other factors we did not assess. These results strongly suggest that serum cytokines at best only weakly reflect peripheral blood cell cytokine production and balances.

Adolescent↗
PubMed2001

Utility of paired BACTEC MYCO/F LYTIC blood culture vials for detection of bacteremia, mycobacteremia, and fungemia.

In previous bloodstream infection studies in Malawi, we inoculated blood from a single venesection into a single BACTEC MYCO/F LYTIC (MFL) vial. Inoculation of one vial, however, would be expected to reduce the sensitivity of bloodstream pathogen detection with MFL vials. To ascertain the degree of this loss of sensitivity, blood was drawn from each of 228 febrile, adult inpatients in Malawi and 5 ml of each blood sample was inoculated into each of two MFL vials. Of 228 paired vials, 51 (22%) were both positive, 172 (75%) were both negative, and 5 (3%) had discordant results. Bloodstream infection would have been detected in 11 (92%) of 12 patients with mycobacteremia and 38 (92%) of 41 patients with bacteremia had only one MFL vial been inoculated. Our study shows that a second MFL vial does not significantly increase diagnostic sensitivity.

Bacteremia↗
PubMed2000

Natural T, gammadelta, and NK cells in mycobacterial, Salmonella, and human immunodeficiency virus infections.

NK cells, gammadelta T cell antigen receptor chain-positive cells, and CD3(+)CD16/56(+) (natural T [NT]) cells are involved in innate immunity and immunoregulation; however, their role in clinical infection is not well defined. Cytofluorometric analysis was used to examine peripheral blood from bacteremic, nonbacteremic, and healthy human immunodeficiency virus (HIV)-positive and -negative persons in Malawi, Africa. Mycobacteremia was associated with a higher proportion of CD3(+)CD8(-) gammadelta cells (median, 16.6% vs. 0.7% for all other cells; P<.001), and Salmonella bacteremia was associated with a higher proportion of NT cells (4.3% vs. 2.2%; P=. 002). HIV plasma RNA levels were weakly positively correlated with NT cells (rs=.39; P=.002), NK cells (rs=.38; P=.003), and gammadelta cells (rs=.43; P<.001). Compared with patients who survived, patients who died had a higher percentage of NT cells (3.7% vs. 1. 9%; P=.017) and a higher percentage of NT cells that spontaneously produced interferon-gamma (2.4% vs. 1.2%; P=.035). The data support the clinical relevance of gammadelta and NT cells in mycobacterial, Salmonella, and HIV infections and of NT cells in mortality.

Adolescent↗
PubMed2000

Acute onset of decreased vision and hearing traced to hemodialysis treatment with aged dialyzers.

CONTEXT: A recent event in which 7 patients at 1 hospital developed decreased vision and hearing, conjunctivitis, headache, and other severe neurologic symptoms 7 to 24 hours after hemodialysis drew attention to the issue of the long-term integrity of dialysis machines and materials. OBJECTIVE: To determine the cause of the adverse reactions that occurred during this event. DESIGN, PATIENTS, AND SETTING: Retrospective cohort study of all 9 patients who received hemodialysis at hospital A on September 18, 1996, the day of the outbreak. A case-patient was defined as any hospital A patient with acute onset of decreased vision and hearing and conjunctivitis after dialysis on that day. Non-case-patients were all others who underwent dialysis at hospital A on that day but did not develop adverse reactions. In an attempt to reproduce the conditions of the event, cellulose acetate dialysis membranes of various ages were retrieved from other sources and tested for physical and chemical degradation, and degradation products were identified, characterized, and injected intravenously into rabbits. MAIN OUTCOME MEASURES: Clinical signs and symptoms, time to resolution of symptoms, mortality, and dialyzer type and age, for case- vs non-case-patients. RESULTS: Seven of the 9 patients met the case definition. In addition to diminished vision and hearing, conjunctivitis, and headache, some case-patients had blood leak alarm activation (n=6), confusion/lethargy (n=5), corneal opacification (n=4), cardiac arrest (n=2), or other neurologic signs and symptoms. One case-patient died during hospitalization after the event; 5 of 7 case-patients died within 13 months. Resolution of signs and symptoms varied but persisted more than 3 years or until death in 3 of the 6 patients who survived hospitalization. All case-patients but no non-case-patients were exposed to 11.5-year-old cellulose acetate dialyzers (all of these dialyzers were discarded by the hospital before our investigation). Laboratory investigation of field-retrieved 0- to 13.6-year-old dialyzers of similar type indicated significant chemical degradation in the older membranes. In vivo injection of extracts of membrane degradation products produced iritis and hemorrhages in rabbits' eyes. CONCLUSIONS: Severe patient injury was associated with exposure to aged cellulose acetate membranes of dialyzers, allowing cellulose acetate degradation products to enter the blood. Clinicians should be aware that aged cellulose acetate membranes may cause severe adverse reactions.

Acute Disease↗
PubMed2000

A hospital-based prevalence survey of bloodstream infections in febrile patients in Malawi: implications for diagnosis and therapy.

The etiology of bloodstream infections (BSIs) in febrile (> or =37.5 degrees C) adults (> or =18 years old) in one Malawi hospital were determined during August and September 1997. After clinical evaluation, blood was drawn for comprehensive culture, human immunodeficiency virus (HIV) type 1 testing, and malaria smear. Of 233 patients, 173 (74%) were HIV-1 infected, and 70 (30%) had BSI. BSI pathogens included 25 (33%) Streptococcus pneumoniae and 21 (28%) Mycobacterium tuberculosis. Nine patients (4%) had malaria parasitemia. BSIs were more likely in HIV-1-positive than in -negative patients (62/173 vs. 8/60, P<.01). Clinical predictors of BSI included HIV-1 infection and altered mental status. Mortality among inpatients with BSI was higher than among those without BSI (P<.001). In conclusion, S. pneumoniae and M. tuberculosis are frequent causes of BSI in febrile adults. Similar surveys, performed periodically in developing countries, may assist in the identification of clinical predictors of BSI and in planning appropriate therapy.

Adolescent↗
PubMed2000

An epidemic of corneal destruction caused by plasma gas sterilization. The Toxic Cell Destruction Syndrome Investigative Team.

BACKGROUND: Toxic endothelial cell destruction (TECD) syndrome after intraocular ophthalmic surgery is rare and can result from exposure to a variety of toxins. During January 8 to 14, 1998, 6 patients developed TECD with corneal edema associated with unreactive or dilated pupils at Hospital A. METHODS: A case patient was any Hospital A patient with TECD within 24 hours after surgery during January 5 to 14, 1998 (epidemic period). A control was any hospital A ophthalmic surgery patient without TECD during the epidemic period. The medical records of hospital A ophthalmology surgery patients during the pre-epidemic (ie, September 1, 1997-January 4, 1998) and epidemic periods were reviewed. Inductively coupled plasma atomic emission spectrometry was used to detect trace inorganic elements on sterilized surgical instruments. Cannulated surgical instruments and laboratory rinsates were perfused directly to the corneal endothelium of isolated rabbit and human corneas. Corneal endothelial ultrastructure and swelling were assessed. RESULTS: The rate of TECD at hospital A was higher during the epidemic than pre-epidemic period (6/12 vs 0/118, P<.001). The only change during the periods was the introduction, on November 5, 1997, of a new sterilization method, AbTox Plazlyte, for sterilization of ophthalmic surgery instruments. Findings from spectrometry revealed that copper and zinc residues were higher in instruments sterilized with Plazlyte than in those sterilized with ethylene oxide (median copper value, 7.64 mg/L vs 0.14 mg/L, respectively, P =.02; median zinc value, 5.90 mg/L vs 1.35 mg/L, respectively, P =.2). Corneal endothelial perfusion of Plazlyte sterilized-instrument rinsates or laboratory solution with copper and zinc produced irreversible damage, similar to toxic corneal endothelial destruction, to rabbit and human corneas. CONCLUSION: A new sterilization method degraded brass to copper and zinc on cannulated surgical instruments resulting in TECD of the cornea. Arch Ophthalmol. 2000;118:1167-1176

Adult↗
PubMed2000

Modifiable risk factors associated with deep sternal site infection after coronary artery bypass grafting.

OBJECTIVE: Our objective was to identify risk factors for deep sternal site infection after coronary artery bypass grafting at a community hospital. METHODS: We compared the prevalence of deep sternal site infection among patients having coronary artery bypass grafting during the study (January 1995-March 1998) and pre-study (January 1992-December 1994) periods. We compared any patient having a deep sternal site infection after coronary artery bypass graft surgery during the study period (case-patients) with randomly selected patients who had coronary artery bypass graft surgery but no deep sternal site infection during the same period (control-patients). RESULTS: Deep sternal site infections were significantly more common during the study than during the pre-study period (30/1796 [1.7%] vs 9/1232 [0.7%]; P =.04). Among 30 case-patients, 29 (97%) returned to the operating room for sternal debridement or rewiring, and 2 (7%) died. In multivariable analyses, cefuroxime receipt 2 hours or more before incision (odds ratio = 5.0), diabetes mellitus with a preoperative blood glucose level of 200 mg/dL or more (odds ratio = 10.2), and staple use for skin closure (odds ratio = 4.0) were independent risk factors for deep sternal site infection. Staple use was a risk factor only for patients with a normal body mass index. CONCLUSIONS: Appropriate timing of antimicrobial prophylaxis, control of preoperative blood glucose levels, and avoidance of staple use in patients with a normal body mass index should prevent deep sternal site infection after coronary artery bypass graft operations.

Aged↗
PubMed2000

Transfusion-related sepsis due to Serratia liquefaciens in the United States.

BACKGROUND: Severe, often fatal, transfusion reactions due to bacterial contamination of blood components continue to occur. Serratia liquefaciens, an unusual human pathogen, is a recently recognized potential cause of transfusion-related sepsis. CASE REPORTS: Five episodes of transfusion-related sepsis and endotoxic shock due to S. liquefaciens were reported to the CDC from July 1992 through January 1999. One episode has been described. The remaining four, all fatal, are described here: three associated with RBC transfusion and one associated with transfusion of platelets. In each instance, the source of contamination could not be found. The implicated units tended to be older (mean RBC age 28 days), and visual discoloration was noted in each RBC unit, although usually in retrospect. CONCLUSION: S. liquefaciens is an increasingly recognized cause of transfusion-related sepsis and is associated with a high mortality rate. S. liquefaciens can contaminate both RBCs and platelets, but the mechanism(s) of contamination remain unknown. Increased attention to pretransfusion visual inspection may avert the transfusion of some S. liquefaciens-contaminated RBC units. However, more sensitive rapid diagnostic tests are needed to further reduce the risk of transfusion-related sepsis and endotoxic shock.

Aged↗
PubMed2000

Risk factors for acquisition of vancomycin-resistant enterococci among patients on a renal ward during a community hospital outbreak.

BACKGROUND: During an outbreak of vancomycin-resistant enterococcal (VRE) infection and colonization at a community hospital in Indianapolis, Indiana, we performed a case-control study of patients on the hospital's renal unit to determine risk factors for acquisition of VRE among this potentially high-risk patient population. METHODS: Twenty-four renal patients with VRE colonization/infection (ie, case-patients) were compared by univariate and multivariate analyses with 29 renal patients with nosocomially acquired vancomycin-susceptible enterococcal infection and colonization (ie, controls). RESULTS: Age and length of hospitalization were similar between the VRE case-patients and the vancomycin-susceptible enterococcal control-patients, but case-patients had higher Acute Physiology and Chronic Health Evaluation II scores and received significantly greater numbers of antimicrobials and significantly more days of antimicrobials during the 60 days preceding the first positive enterococcal culture. In an assessment of the appropriateness of vancomycin use, one third of vancomycin orders were found to be inappropriate in both patient groups. CONCLUSIONS: Our data show that among renal patients, those who are severely ill and receive multiple and prolonged courses of antimicrobials are at greatest risk for acquiring VRE infection or colonization. The Centers for Disease Control and Prevention recommends that hospitals develop a comprehensive plan to prevent and control infection and colonization of patients with VRE. This plan should include prompt identification of affected patients, initiation of isolation precautions to prevent patient-to-patient transmission of VRE, and prudent use of antimicrobials, including vancomycin.

APACHE↗
PubMed2000

Association between implementation of CDC recommendations and ventilator-associated pneumonia at selected US hospitals.

BACKGROUND: To assess whether selected recommendations in the Centers for Disease Control and Prevention "Guideline for Prevention of Nosocomial Pneumonia" were being implemented and having an impact on the occurrence of ventilator-associated pneumonia (VAP) at US hospitals, we surveyed hospitals participating in the National Nosocomial Infections Surveillance (NNIS) system. METHODS: We mailed a questionnaire to the infection control practitioner of each NNIS hospital in 1995 and used data from the NNIS system to calculate annual rates of VAP. RESULTS: Of the 188 hospitals surveyed, 179 (95%) returned completed questionnaires. Of these, 175 (98%) had implemented the recommended change of mechanical-ventilator breathing circuits at 48-hour or greater intervals. Of 110 hospitals using the hygroscopic condenser-humidifiers or heat-moisture exchangers with ventilators, 102 (93%) changed the hygroscopic condenser-humidifiers or heat-moisture exchangers routinely, and of 98 hospitals using bubbling humidifiers, 96 (98%) used sterile water to fill these humidifiers. Other practices for which the guideline provides no recommendation and their frequency of use by NNIS hospitals include use of hygroscopic condenser-humidifiers or heat-moisture exchangers (110/179 [61%]) and use of bacterial filters in anesthesia machines (128/171 [61%]). There was a significant decrease in the VAP rate from 1987 to 1998. CONCLUSION: Most NNIS hospitals had implemented selected recommendations in the Centers for Disease Control and Prevention "Guideline for Prevention of Nosocomial Pneumonia" before the final publication of the revised guideline. Further studies are needed to assess the impact of these recommendations on the occurrence of VAP.

Anesthesiology↗
PubMed2000

Status of infection surveillance and control programs in the United States, 1992-1996. Association for Professionals in Infection Control and Epidemiology, Inc.

BACKGROUND: Nosocomial infections have been recognized as a source of morbidity and mortality throughout the world for several decades. In the United States, an estimated 2.1 million nosocomial infections occur annually in acute care hospitals alone. Infection surveillance and control programs (ISCPs) play a vital role in addressing this problem, but no national studies have described the status and composition of these programs since the 1970s. METHODS: In January 1997, a voluntary survey was sent by mail to members of the Association for Professionals in Infection Control and Epidemiology, Inc. Only one response per facility was requested. The survey asked for information for the years 1992 to 1996 (study period), and questions pertained to characteristics of the health care facility in which the respondent worked, characteristics of the ISCP and its personnel, and the overall level of administration support for infection control activities. RESULTS: Completed questionnaires were received from personnel at 187 health care facilities located in 40 states and the District of Columbia. The majority (76.5%) of responding facilities were nongovernment owned, and 57.2% were classified as general acute care facilities. The number of licensed beds at these facilities remained stable throughout the study period, but all other measures of facility size and activity (eg, number of patient days and number of nurses) decreased by as much as 28.9%. In 1992, ISCPs were most likely to be organizationally located in the Nursing Department, but by 1996, many had been transferred to departments of Medical Records, Quality Assurance, or Risk Management. Throughout the course of the study period, the number of facilities performing surveillance for health care-associated infections in outpatient settings increased by 44.0%, from 100 to 144. In 1996, only 47.6% of facilities had a hospital epidemiologist (HE), and HEs devoted a median of 15% or less of their time to infection control activities. For the most part, HEs were trained in infectious diseases, and few had certification in infection control. Infection control professionals (ICPs) were much more common than were HEs (ICPs were reported at 97.9% of respondents' facilities in 1996), and they spent the majority (80% in 1996) of their time on infection control activities. During the course of the study period, increasing numbers of facilities had ICPs who had certification in infection control. Furthermore, most respondents did not report a change over time in the level of administration support for infection control activities. CONCLUSIONS: Health care delivery has changed dramatically during the past 20 years. This study presents an updated description of ISCPs in the United States. Our results illustrate several changing parameters, such as departmental shifts and increased outpatient surveillance, that reflect adjustments in health care priorities during the study period. As the transformation of the health care system continues, continued evaluation of the status of ISCPs on a national level will be necessary. Diligent monitoring, proactive measures, and collaboration between infection control organizations and government agencies will be vital for the prevention and control of health care-associated infections in the future.

Ambulatory Care↗
PubMed2000

The Internet: a practical example of the use of new technology in the assessment of vancomycin use in pediatrics. The Pediatric Prevention Network.

BACKGROUND: The rapid emergence of both new infections and new technologies has revolutionized health care during the past 50 years. Increased use of the Internet has enabled health care professionals to educate, interact, and collaborate throughout the world in ways never before possible. Increased use of vancomycin has been associated with the emergence of organisms with decreased susceptibility to vancomycin, such as Enterococcus and staphylococcal species. The purpose of this article is to describe our experience using Internet technology to assess vancomycin use at children's hospitals in the United States. METHODS: A Web-based evaluation was developed and distributed on the Internet to 57 Pediatric Prevention Network hospitals. The evaluation was structured to collect summary statistics on vancomycin use and admissions data by service for 1997 and 1998. RESULTS: Twenty-four hospitals were able to provide archived vancomycin use and patient admissions data; completed evaluations were returned from 15 hospitals (62.5% response rate). Personnel at 6 (40%) hospitals completed the evaluation directly on the Internet. CONCLUSIONS: In our study, Internet technology facilitated a more efficient evaluation of vancomycin use, but fewer than half of the personnel at Pediatric Prevention Network hospitals completed the evaluation directly on the Internet. It is unclear whether personnel at these hospitals were limited in Internet access, support, or understanding. Efforts should be directed to educate health care personnel on the advantages of the Internet. Furthermore, many of the pharmacy databases used in our assessment were not standardized across hospitals nor systematically validated. Understanding that limitations still remain-within the source of the data studied, the health care system sampled, and the Internet tools available-is essential because the Internet offers health care professionals today a tool both to protect patients and to improve quality throughout the world.

Attitude to Computers↗
PubMed2000

Enterobacter cloacae bloodstream infections traced to contaminated human albumin.

In August 1996, a patient in Kansas developed an Enterobacter cloacae bloodstream infection (BSI) shortly after receiving Albuminar, a brand of human albumin. Albuminar contamination was suspected. A case-control study of patients with primary gram-negative bacterial BSIs showed that patients with E. cloacae BSIs were significantly more likely than patients with non-E. cloacae gram-negative BSIs to have received Albuminar within 3 days of developing their BSIs (3 of 5 vs. 0 of 9; OR, undefined; P=.03). The E. cloacae isolate from the Kansas patient was found by pulsed-field gel electrophoresis to be identical to the isolate from the patient's Albuminar vial, to isolates from 2 previously unopened Albuminar vials, and to an isolate from a Wisconsin patient who had received Albuminar. A worldwide recall of approximately 116,000 Albuminar vials took place. This multistate outbreak was detected because of clinical astuteness and prompt reporting. Combined epidemiological and laboratory approaches are valuable when investigating potentially contaminated blood components and plasma derivatives.

Adult↗
PubMed2000

Risk factors for radial artery harvest site infection following coronary artery bypass graft surgery.

Radial arteries increasingly are used during coronary artery bypass graft (CABG) surgery. Although risk factors for saphenous vein harvest site infection (HSI) have been reported, rates of and risk factors for radial artery HSI are not well established. We compared rates of radial artery HSI that were detected by 2 surveillance methods, regular and heightened. Risk factors were determined by a case-control study. We identified 35 radial artery HSIs ("case sites") in 26 case patients. The radial artery HSI rate was significantly higher during heightened surveillance than during routine surveillance (12.3% vs. 3.1%, respectively; P=.002). Multivariate analysis showed that diabetes mellitus with a preoperative glucose level >/=200 mg/dL (odds ratio [OR], 4.4; P=. 01) and duration of surgery >/=5 h (OR, 3.1; P=.02) were independent risk factors for radial artery HSI. Infection is a common complication of radial artery harvesting for CABG surgery, and infection rates are dependent on the intensity of surveillance. We identified preoperative hyperglycemia and surgery duration as independent risk factors for radial artery HSI.

Aged↗
PubMed2000

Epidemic transmission of human immunodeficiency virus in renal dialysis centers in Egypt.

In 1993 an epidemic of human immunodeficiency virus (HIV) infection occurred among 39 patients at 2 renal dialysis centers in Egypt. The centers, private center A (PCA) and university center A (UCA) were visited, HIV-infected patients were interviewed, seroconversion rates at UCA were calculated, and relatedness of HIV strains was determined by sequence analysis; 34 (62%) of 55 patients from UCA and 5 (42%) of 12 patients from PCA were HIV-infected. The HIV seroconversion risk at UCA varied significantly with day and shift of dialysis session. Practices that resulted in sharing of syringes among patients were observed at both centers. The analyzed V3 loop sequences of the HIV strain of 12 outbreak patients were >96% related to each other. V3 loop sequences from each of 8 HIV-infected Egyptians unrelated to the 1993 epidemic were only 76%-89% related to those from outbreak strains. Dialysis patients may be at risk for HIV infection if infection control guidelines are not followed.

Adolescent↗
PubMed2000

The influence of the composition of the nursing staff on primary bloodstream infection rates in a surgical intensive care unit.

OBJECTIVES: To determine the risk factors for acquisition of nosocomial primary bloodstream infections (BSIs), including the effect of nursing-staff levels, in surgical intensive care unit (SICU) patients. DESIGN: A nested case-control study. SETTING: A 20-bed SICU in a 1,000-bed inner-city public hospital. PATIENTS: 28 patients with BSI (case-patients) were compared to 99 randomly selected patients (controls) hospitalized > or =3 days in the same unit. RESULTS: Case- and control-patients were similar in age, severity of illness, and type of central venous catheter (CVC) used. Case-patients were significantly more likely than controls to be hospitalized during a 5-month period that had lower regular-nurse-to-patient and higher pool-nurse-to-patient ratios than during an 8-month reference period; to be in the SICU for a longer period of time; to be mechanically ventilated longer; to receive more antimicrobials and total parenteral nutrition; to have more CVC days; or to die. Case-patients had significantly lower regular-nurse-to-patient and higher pool-nurse-to-patient ratios for the 3 days before BSI than controls. In multivariate analyses, admission during a period of higher pool-nurse-to-patient ratio (odds ratio [OR]=3.8), total parenteral nutrition (OR=1.3), and CVC days (OR=1.1) remained independent BSI risk factors. CONCLUSIONS: Our data suggest that, in addition to other factors, nurse staffing composition (ie, pool-nurse-to-patient ratio) may be related to primary BSI risk. Patterns in intensive care unit nurse staffing should be monitored to assess their impact on nosocomial infection rates. This may be particularly important in an era of cost containment and healthcare reform.

Case-Control Studies↗