Risk factors for community-associated Staphylococcus aureus infections: results from parallel studies including methicillin-resistant and methicillin-sensitive S. aureus compared to uninfected controls.

Despite the increasing burden of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, the risk factors are not well understood. We conducted a hypothesis-generating study using three parallel case-control studies to identify risk factors for CA-MRSA and community-associated methicillin-susceptible S. aureus (CA-MSSA) infections. In the multivariate model, antimicrobial use in the 1-6 months prior to culture was associated with CA-MRSA infection compared to CA-MSSA [adjusted odds ratio (aOR) 1·7, P=0·07] cases. Antimicrobial use 1-6 months prior to culture (aOR 1·8, P=0·04), history of boils (aOR 1·6, P=0·03), and having a household member who was a smoker (aOR 1·3, P=0·05) were associated with CA-MRSA compared to uninfected community controls. The finding of an increased risk of CA-MRSA infection associated with prior antimicrobial use highlights the importance of careful antimicrobial stewardship.

Impact of early central venous catheter removal on outcome in patients with candidaemia.

Removal of central venous catheters (CVCs) from candidaemic patients is considered the reference standard of care, although this practice is not always possible. The impact of prompt catheter removal on outcome was investigated by analysing data from an active population-based surveillance study in Barcelona, Spain. Patients with candidaemia and a CVC were identified between January 2002 and December 2003. Cases with CVC removal within 2 days were classified as having early CVC removal. Outcome, defined as in-hospital mortality 2-30 days after diagnosis of candidaemia, was determined among hospitalised adults using univariate, Kaplan-Meier and multivariate logistic regression analysis. Outpatients, paediatric patients and those who died or were discharged within 2 days were excluded. The study identified 265 patients with candidaemia and a CVC. Median time from diagnosis of candidaemia to catheter removal was 1 day (range 0-29 days). Overall, 172 patients met the criteria for inclusion in the outcome study. Patients with early CVC removal differed significantly from those with delayed CVC removal. According to univariate, Kaplan-Meier and multivariate analysis, the marker most predictive of in-hospital mortality among candidaemic patients with CVCs was severity of illness. These data suggest that timing of CVC removal may best be determined after carefully considering the risks and benefits to individual patients.

Secular trend of hospital-acquired candidemia among intensive care unit patients in the United States during 1989-1999.

We describe the annual incidence of primary bloodstream infection (BSI) associated with Candida albicans and common non-albicans species of Candida among patients in intensive care units that participated in the National Nosocomial Infections Surveillance system from 1 January 1989 through 31 December 1999. During the study period, there was a significant decrease in the incidence of C. albicans BSI (P<.001) and a significant increase in the incidence of Candida glabrata BSI (P=.05).

The effect of renal dysfunction on antimicrobial use measurements.

The defined daily dose, a popular measurement of antimicrobial use, may underestimate the use of antimicrobials that are dose-adjusted in patients with renal insufficiency. To evaluate the effect of renal dysfunction on these measures, we performed a retrospective cohort study that involved patients receiving ceftriaxone, levofloxacin, or vancomycin, with use of defined daily doses and 2 methods based on therapy duration--stop-start days (i.e., entire therapy duration) and transaction days (i.e., unique therapeutic days). The vancomycin use rate for patients with renal insufficiency was 36% lower than that of patients with normal renal function for defined daily doses, and it was 23% lower for transaction days; for levofloxacin, there was a 27% rate reduction for the defined daily dose. No significant reduction was noted when the stop-start day method was used. Compared with the defined daily dose method, measures of therapy duration are less affected by renal function and may improve comparisons between populations.

SHEA-CDC TB survey, Part I: Status of TB infection control programs at member hospitals, 1989-1992. Society for Healthcare Epidemiology of America.

OBJECTIVE: To determine trends in Mycobacterium tuberculosis infection in healthcare workers, tuberculosis (TB) control measures, and compliance with the 1990 Centers for Disease Control and Prevention (CDC) guideline for preventing transmission of TB in healthcare facilities. DESIGN: Voluntary questionnaire sent to all members of the Society for Healthcare Epidemiology of America, representing 359 hospitals. RESULTS: Respondents' hospitals (210 [58%]) had a median of 2,400 healthcare workers (range, 396 to 13,745), 437 beds (range, 48 to 1,250), 5.6 patients with TB per year (range, 0 to 492), and 0 multidrug-resistant (MDR) TB patients per year (range, 0 to 33). Of 166 respondents' hospitals for which data were provided for 1989 through 1992, the number caring for MDR-TB patients increased from 10 (6%) in 1989 to 49 (30%) in 1992. Reported policies for routine healthcare worker tuberculin skin testing varied. The median skin-test positivity rate for healthcare workers at the time of hire increased from 0.54% in 1989 to 0.81% in 1992, but the median conversion rate during routine testing remained similar: 0.35% in 1989 and 0.33% in 1992. Among 196 hospitals with reported data on respiratory protection use for 1989 through 1992, the use of either surgical submicron, dust-mist, or dust-fume-mist respirators for healthcare workers increased from 9 (5%) in 1989 to 85 (43%) in 1992. Of 181 hospitals with reported data, 113 (62%) had acid-fast bacilli isolation facilities consistent with the 1990 CDC guideline (ie, a single patient room, negative air pressure relative to the hallway, air exhausted directly outside, and > or = 6 air exchanges per hour). CONCLUSIONS: While the number of surveyed hospitals caring for TB and MDR-TB patients increased during 1989 through 1992, TB infection control measures at many hospitals still did not meet the 1990 CDC guideline recommendations.

SHEA-CDC TB survey, Part II: Efficacy of TB infection control programs at member hospitals, 1992. Society for Healthcare Epidemiology of America.

OBJECTIVE: To assess the efficacy of current Mycobacterium tuberculosis control measures. DESIGN: Voluntary questionnaire to members of the Society for Healthcare Epidemiology of America. RESULTS: Healthcare worker (HCW) tuberculin skin-test (TST) conversion rates were significantly higher in larger hospitals (> or = 437 beds) (0.9% versus 0.6%; P < 0.05), or in hospitals reporting > or = 6 TB patients in 1992 (1.2% versus 0.6%; P < 0.05). Among larger hospitals or those hospitals surveyed reporting > or = 6 TB patients, those without at least three of the four criteria suggested in the 1990 Centers for Disease Control and Prevention (CDC) TB guidelines for acid-fast bacilli (AFB) isolation (specifically, a single-patient room; negative pressure; and air exhausted directly outside) had significantly higher annual TST conversion rates than those with these criteria (1.8% versus 0.6%; P < 0.05). Respiratory therapist or bronchoscopist TST conversion rates were significantly lower in hospitals compliant with the exhaust criteria (1.2% versus 2.8%; P < 0.05). Regardless of hospital characteristic, HCW TST conversion rates did not differ between hospitals in which HCWs used surgical masks or used disposable particulate respirators. CONCLUSION: Among larger hospitals or hospitals reporting > or = 6 TB patients per year, failure to comply with the 1990 CDC TB recommendations for AFB isolation room guidelines was associated with higher HCW TST conversion rates. These data suggest that complete implementation of the 1990 CDC TB guidelines would decrease HCWs' risk of nosocomial transmission of TB in larger hospitals or those reporting more TB patients. However, in nonoutbreak situations, disposable particulate respirators or submicron surgical masks may not offer significantly greater protection to HCWs than surgical masks.

Practices to improve antimicrobial use at 47 US hospitals: the status of the 1997 SHEA/IDSA position paper recommendations. Society for Healthcare Epidemiology of America/Infectious Diseases Society of America.

OBJECTIVE: To determine the status of programs to improve antimicrobial prescribing at select US hospitals. DESIGN: Cross-sectional survey. PARTICIPANTS AND SETTING: Pharmacy and infection control staff at all 47 hospitals participating in phase 3 of Project Intensive Care Antimicrobial Resistance Epidemiology. RESULTS: All 47 hospitals had some programs to improve antimicrobial use, but the practices reported varied considerably. All used a formulary, and 43 (91%) used it in conjunction with at least one of the other three antimicrobial-use policies evaluated: stop orders, restriction, and criteria-based clinical practice guidelines (CPGs). CPGs were reported most commonly (70%), followed by stop orders (60%) and restriction policies (40%). Although consultation with an infectious disease physician (70%) or pharmacist (66%) was commonly used to influence initial antimicrobial choice, few (40%) reported a system to measure compliance with these consultations. CONCLUSIONS: In most hospitals surveyed, practices to improve antimicrobial use, although present, were inadequate based on recommendations in a Society for Healthcare Epidemiology of America and Infectious Disease Society of America joint position paper. There is room to improve antimicrobial-use stewardship at US hospitals.

The role of understaffing in central venous catheter-associated bloodstream infections.

OBJECTIVE: To determine risk factors for central venous catheter-associated bloodstream infections (CVC-BSI) during a protracted outbreak. DESIGN: Case-control and cohort studies of surgical intensive care unit (SICU) patients. SETTING: A university-affiliated Veterans Affairs medical center. PATIENTS: Case-control study: all patients who developed a CVC-BSI during the outbreak period (January 1992 through September 1993) and randomly selected controls. Cohort study: all SICU patients during the study period (January 1991 through September 1993). MEASUREMENTS: CVC-BSI or site infection rates, SICU patient clinical data, and average monthly SICU patient-to-nurse ratio. RESULTS: When analyzed by hospital location and site, only CVC-BSI in the SICU had increased significantly in the outbreak period compared to the previous year (January 1991 through December 1991: pre-outbreak period). In SICU patients, CVC-BSI were associated with receipt of total parenteral nutrition [TPN]; odds ratio, 16; 95% confidence interval, 4 to 73). When we controlled for TPN use, CVC-BSI were associated with increasing severity of illness and days on assisted ventilation. SICU patients in the outbreak period had shorter SICU and hospital stays, were younger, and had similar mortality rates, but received more TPN compared with patients in the pre-outbreak period. Furthermore, the patient-to-nurse ratio significantly increased in the outbreak compared with the pre-outbreak period. When we controlled for TPN use, assisted ventilation, and the period of hospitalization, the patient-to-nurse ratio was an independent risk factor for CVC-BSI in SICU patients. CONCLUSIONS: Nursing staff reductions below a critical level, during a period of increased TPN use, may have contributed to the increase in CVC-BSI in the SICU by making adequate catheter care difficult. During healthcare reforms and hospital downsizing, the effect of staffing reductions on patient outcome (i.e., nosocomial infection) needs to be critically assessed.

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.

Characteristics of hospitals and infection control professionals participating in the National Nosocomial Infections Surveillance System 1999.

The National Nosocomial Infections Surveillance (NNIS) system is the oldest and largest monitoring system for health care-acquired infections in the United States. This report describes both the characteristics of NNIS hospitals compared with those of US hospitals with 100 beds or more and their infection control programs. Overall, NNIS hospitals tend to have more hospital beds than the average for-comparable US hospitals. The majority of NNIS hospitals have affiliations with academic medical centers, and most have substantial intensive care units. Even though infection control professionals in NNIS hospitals spend most of their time in inpatient settings, 40% of their time is also spent in a variety of other settings, including home health, outpatient surgery or clinics, extended care facilities, employee health and quality management, and other clinical or administrative activities. As described in this report, the infrastructure of the NNIS system offers a national resource on which to build improved voluntary patient safety monitoring efforts, as outlined in the recent Institute of Medicine report on medical errors.

Status of tuberculosis infection control programs at United States hospitals, 1989 to 1992. APIC. Association for Professionals in Infection Control and Epidemiology.

BACKGROUND: Recent nosocomial outbreaks have raised concern about the risk of Mycobacterium tuberculosis transmission in United States hospitals. METHODS: To determine current tuberculosis (TB) infection control practices, we surveyed a sample of approximately 3000 acute care facilities about the number of patients with drug-susceptible or multidrug-resistant TB (MDR-TB), health care worker (HCW) tuberculin skin test (TST) results, and compliance with the 1990 Centers for Disease Control and Prevention (CDC) TB guidelines. Analyses were restricted to one response per hospital. RESULTS: Personnel at 1494 (49.8%) hospitals returned a completed survey. Respondent hospitals had a mean of 881 HCWs (range 8 to 10,000) and 196 (range 6 to 2450) beds; 62% percent were community nonteaching hospitals. Of respondent hospitals providing data for 1989 through 1992, the proportion that cared for patients with TB or MDR-TB increased from 46.4% to 56.6% and 0.8% to 4.5%, respectively. The pooled mean HCW TST positivity rate at hire rose from 0.95% to 1.14%, and the pooled mean HCW TST conversion rate increased from 0.40% to 0.51%. In 1992, when we compared hospitals with zero, one to five, or six or greater patients with TB, the risk of a positive HCW TST result at hire or at routine testing significantly increased with increasing number of patients with TB. From 1989 through 1992, the number of hospitals reporting the use of surgical masks for HCW respiratory protection decreased from 96.8% to 66.8%. In 1992, 66% of the hospitals reported compliance with four or more of the AFB isolation room criteria specified in the 1990 CDC TB guidelines. CONCLUSIONS: Contrary to prior surveys, this study shows that many U.S. community hospitals admit patients with TB less frequently than do teaching hospitals, and infrequently admit patients with MDR-TB. Because the risk of HCW TST conversion varies with hospital characteristics, these data show the importance of performing a risk assessment, as recommended in the CDC TB guidelines, for each ward and hospital so that TB control measures can be individualized.

Magnitude and prevention of nosocomial infections in the intensive care unit.

Nosocomial infections among intensive care unit (ICU) patients usually are related to the use of invasive devices (e.g., mechanical ventilators, urinary catheters, or central venous catheters). This article discusses the impact of these devices and other risk factors for nosocomial infection in ICU patients. Data on etiologic pathogens and device-related infection rates from the National Nosocomial Infection Surveillance System are presented, general infection control guidelines for ICUs are reviewed, and special infection control problems encountered in ICUs are discussed.

Ability of laboratories to detect emerging antimicrobial resistance in nosocomial pathogens: a survey of project ICARE laboratories.

A proficiency testing project was conducted among 48 microbiology laboratories participating in Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology). All laboratories correctly identified the Staphylococcus aureus challenge strain as oxacillin- resistant and an Enterococcus faecium strain as vancomycin-resistant. Thirty-one (97%) of 32 laboratories correctly reported the Streptococcus pneumoniae strain as erythromycin-resistant. All laboratories testing the Pseudomonas aeruginosa strain against ciprofloxacin or ofloxacin correctly reported the organism as resistant. Of 40 laboratories, 30 (75%) correctly reported resistant MICs or zone sizes for the imipenem- and meropenem-resistant Serratia marcescens. For the extended-spectrum beta-lactamase (ESBL)-producing strain of Klebsiella pneumoniae, 18 (42%) of 43 laboratories testing ceftazidime correctly reported ceftazidime MICs in the resistant range. These results suggest that current testing generally produces accurate results, although some laboratories have difficulty detecting resistance to carbapenems and extended-spectrum cephalosporins. This highlights the need for monitoring how well susceptibility test systems in clinical laboratories detect emerging resistance.

Antimicrobial resistance in intensive care units.

The unique nature of the intensive care unit (ICU) environment makes this part of the hospital a focus for the emergence and spread of many antimicrobial-resistant pathogens. There are ample opportunities for the cross-transmission of resistant bacteria from patient to patient, and patients are commonly exposed to broad-spectrum antimicrobial agents. Rates of resistance have increased for most pathogens associated with nosocomial infections among ICU patients, and rates are almost universally higher among ICU patients compared with non-ICU patients. There are many opportunities, however, to prevent the emergence and spread of these resistant pathogens through improved use of established infection control measures (i.e., patient isolation, hand washing, glove use, and appropriate gown use), and implementation of a systematic review of antimicrobial use.

Nosocomial acquisition of Pseudomonas aeruginosa resistant to both ciprofloxacin and imipenem: a risk factor and laboratory analysis.

In vitro, ciprofloxacin can select for dual resistance to fluoroquinolones and imipenem in Pseudomonas aeruginosa via a mutation in the regulatory gene, mexT, which downregulates OprD and upregulates MexEF-OprN. We performed a nested case-control study of patients in two medical intensive care units participating in an observational cohort study. Patients colonized or infected with P. aeruginosa resistant to both ciprofloxacin and imipenem (cases) were compared to controls. The presence of OprD and OprN from cases was evaluated by Western blot. In total, 44 cases were compared to 132 controls. Imipenem exposure [adjusted odds ratio (AOR) = 11.4, p = 0.044] was significantly associated with case status, but fluoroquinolone use was not (AOR = 1.0, p = 0.998). Neither OprD nor OprN were detected in any isolate. Fluoroquinolone use was not a risk factor for acquisitions of dually resistant P. aeruginosa. The absence of OprN in these isolates suggests that dual resistance is not due to mexT mutations.

Incidence of invasive aspergillosis following hematopoietic stem cell and solid organ transplantation: interim results of a prospective multicenter surveillance program.

The incidence of invasive aspergillosis was estimated among 4621 hematopoietic stem cell transplants (HSCT) and 4110 solid organ transplants (SOT) at 19 sites dispersed throughout the United States, during a 22 month period from 1 March 2001 through 31 December 2002. Cases were identified using the consensus definitions for proven and probable infection developed by the Invasive Fungal Infections Cooperative Group of the European Organization for Research and Treatment of Cancer and the Mycoses Study Group of the National Institute of Allergy and Infectious Diseases. The cumulative incidence (CI) of aspergillosis was calculated for the first episode of the infection that occurred within the specified time period after transplantation. To obtain an aggregate CI for each type of transplant, data from participating sites were weighted according to the proportion of transplants followed-up for specified time periods (four and 12 months for HSCT; six and 12 months for SOT). The aggregate CI of aspergillosis at 12 months was 0.5% after autologous HSCT, 2.3% after allogeneic HSCT from an HLA-matched related donor, 3.2% after transplantation from an HLA-mismatched related donor, and 3.9% after transplantation from an unrelated donor. The aggregate CI at 12 months was similar following myeloablative or non-myeloablative conditioning before allogeneic HSCT (3.1 vs. 3.3%). After HSCT, mortality at 3 months following diagnosis of aspergillosis ranged from 53.8% of autologous transplants to 84.6% of unrelated-donor transplants. The aggregate CI of aspergillosis at 12 months was 2.4% after lung transplantation, 0.8% after heart transplantation, 0.3% after liver transplantation, and 0.1% after kidney transplantation. After SOT, mortality at three months after diagnosis of aspergillosis ranged from 20% for lung transplants to 66.7% for heart and kidney transplants. The Aspergillus spp. associated with infections after HSCT included A. fumigatus (56%), A. flavus (18.7%), A. terreus (16%), A. niger (8%), and A. versicolor (1.3%). Those associated with infections after SOT included A. fumigatus (76.4%), A. flavus (11.8%), and A. terreus (11.8%). In conclusion, we found that invasive aspergillosis is an uncommon complication of HSCT and SOT, but one that continues to be associated with poor outcomes. Our CI figures are lower compared to those of previous reports. The reasons for this are unclear, but may be related to changes in transplantation practices, diagnostic methods, and supportive care.

Increasing prevalence of antimicrobial resistance in intensive care units.

The unique nature of the intensive care unit (ICU) environment makes this part of the hospital a focus for the emergence and spread of many antimicrobial-resistant pathogens. There are ample opportunities for the cross-transmission of resistant bacteria from patient to patient, and patients are commonly exposed to broad-spectrum antimicrobial agents. Rates of resistance have increased for most pathogens associated with hospital-acquired infections among ICU patients, and rates are almost universally higher among ICU patients than non-ICU patients. Likewise, ICU patients hospitalized longer (i.e., >7 days) are two- to three-fold more likely to be infected with a pathogen possessing an antimicrobial-resistant phenotype of concern. However, there are many opportunities to prevent the emergence and spread of these resistant pathogens through improved use of established infection control measures (patient isolation, handwashing, glove use, and appropriate gown use) and implementation of a systematic review of antimicrobial use. (Crit Care Med 2001; 29[Suppl.]: N64-N68)

Vancomycin-intermediate and -resistant Staphylococcus aureus: what the infectious disease specialist needs to know.

Ever since the first strain of Staphylococcus aureus with reduced susceptibility to vancomycin and teicoplanin was reported from Japan, there has been a lot of confusion regarding the laboratory and clinical approach to patients with infections due to S. aureus with reduced susceptibility to vancomycin. To date, 6 clinical infections with vancomycin-intermediate S. aureus (VISA) have been reported in the United States. Intermediate resistance appears to develop from preexisting strains of methicillin-resistant S. aureus in the presence of vancomycin, and all but 1 infection occurred in patients with exposure to dialysis for renal insufficiency. Detection of VISA is difficult in the laboratory, and special inquiries about susceptibility testing methods may be needed. These VISA-infected patients had underlying illnesses, and their infections did not appear to respond well to conventional treatment. Prevention strategies have been outlined. Without continued vigilance in enforcing infection-control measures, improved use of antimicrobials, and coordination of efforts among public health authorities, increasing levels of vancomycin resistance in S. aureus are likely to be encountered.

Epidemiology of nosocomial fungal infections.

This paper briefly reviews the current knowledge of the epidemiology and modes of transmission of nosocomial fungal infections and some of the therapeutic options for treating these diseases. In the mid-1980s, many institutions reported that fungi were common pathogens in nosocomial infections. Most, if not all, hospitals care for patients at risk for nosocomial fungal infections. The proportion in all nosocomial infections reportedly caused by Candida spp. increased from 2% in 1980 to 5% in 1986 to 1989. Numerous studies have identified common risk factors for acquiring these infections, most of which are very common among hospitalized patients; some factors act primarily by inducing immunosuppression (e.g., corticosteroids, chemotherapy, malnutrition, malignancy, and neutropenia), while others primarily provide a route of infection (e.g., extensive burns, indwelling catheter), and some act in combination. Non-albicans Candida spp., including fluconazole-resistant C. krusei and Torulopsis (C.) glabrata, have become more common pathogens. Newer molecular typing techniques can assist in the determination of a common source of infection caused by several fungal pathogens. Continued epidemiologic and laboratory research is needed to better characterize these pathogens and allow for improved diagnostic and therapeutic strategies.