Vancomycin-resistant Staphylococcus aureus: perspectives on measures needed for control

Given the dramatic increase in the incidence of vancomycin resistance among the enterococci and experimental evidence for the transfer of vancomycin resistance from enterococci to Staphylococcus aureus, there is concern that strains of S. aureus will emerge that are resistant to vancomycin. The result would be a highly virulent pathogen for which effective antimicrobial therapy would not be available. To prevent the nosocomial transmission of such an organism, stringent infection control policies need to be developed and implemented. We offer proposals that are based on the limited data available on the transmission and control of S. aureus and that may be used as starting points for the development of formal guidelines for the isolation of colonized and infected patients and for microbiology laboratory precautions.

Outbreak of keratitis presumed to be caused by Acanthamoeba

PURPOSE

A sharp increase of Acanthamoeba keratitis from two cases per year to 30 cases per year at our institution prompted this study to determine whether there was a change in the clinical characteristics, basic epidemiology, and outcome of this disease.

METHODS

We reviewed all cases of Acanthamoeba keratitis diagnosed at the University of Iowa Hospitals and Clinics from mid-1993 through 1994.

RESULTS

We screened 217 patients with keratitis by tandem scanning confocal microscopy and suspected Acanthamoeba in 51 patients. Diagnosis was confirmed by cytology in 43 patients (48 eyes). There were no positive cultures. Patients examined within four weeks of onset of symptoms were younger (mean age, 32.6 +/- 15.4 years) and wore contact lenses (11 of 18 patients), and infrequently herpes simplex keratitis (four of 18 patients) was diagnosed. Patients examined after four weeks were older (mean age, 54.0 +/- 19.5 years), infrequently wore contact lenses (six of 25 patients), and often had herpes simplex keratitis (12 of 25 patients).

CONCLUSIONS

Corneal examination with tandem scanning confocal microscopy was associated with a marked increase in the detection of Acanthamoeba, strongly suggesting that the disease is more prevalent than suspected. Acanthamoeba may account for many cases of clinically presumed herpes simplex keratitis, the leading cause of corneal blindness in the United States. Acanthamoeba should be considered in the differential diagnosis of any unexplained keratitis, even those of short duration.

Bedside prediction of mortality from bacteremic sepsis. A dynamic analysis of ICU patients

The prognosis in patients with sepsis depends on severity of acute illness, underlying chronic diseases, and complications associated with infection. Adjusting for these factors is essential for evaluation of new therapies. The purpose of the present study was to determine variables readily identifiable at the bedside that predict mortality in intensive care unit (ICU) patients with sepsis and positive blood cultures. For a 5-yr period, all patients of a surgical ICU presenting with positive blood cultures and sepsis were systematically analyzed for clinical variables and organ dysfunctions at the day of onset of sepsis and bacteremia and during the subsequent clinical course. The prognostic value of these variables was determined using logistic regression procedures. Of the 5,457 admissions to the ICU, 176 patients developed sepsis with positive blood cultures (3.2 per 100 admissions). The fatality rate was 35% at 28 days after the onset of sepsis; in-hospital mortality was 43%. Independent predictors of mortality at onset of sepsis were previous antibiotic therapy (odds ratio [OR], 2.40; 95% confidence interval [CI95], 1.59 to 3.62; p = 0.034), hypothermia (OR, 1.43; CI95, 1.04 to 2.44; p = 0.030), requirement for mechanical ventilation (OR, 2.97; CI95, 1.96 to 4.51; p = 0.009), and onset-of-sepsis APACHE II score (OR, 1.21; CI95, 1.13 to 1.29; p < 0.001). Vital organ dysfunctions developing after the onset of sepsis influenced outcome markedly. The best two independent prognostic factors were the APACHE II score at the onset of sepsis (OR, 1.13 per unit; CI95, 1.08 to 1.17; p = 0.0016) and the number of organ dysfunctions developing thereafter (OR, 2.39; CI95, 2.02 to 2.82; p < 0.001). In ICU patients with sepsis and positive blood cultures, outcome can be predicted by the severity of illness at onset of sepsis and the number of vital organ dysfunctions developing subsequently. These variables are easily assessed at the bedside and should be included in the evaluation of new therapeutic strategies.

Strategies to Prevent and Control the Emergence and Spread of Antimicrobial-Resistant Microorganisms in Hospitals. A challenge to hospital leadership

OBJECTIVE

To provide hospital leaders with strategic goals or actions likely to have a significant impact on antimicrobial resistance, outline outcome and process measures for evaluating progress toward each goal, describe potential barriers to success, and suggest countermeasures and novel improvement strategies.

PARTICIPANTS

A multidisciplinary group of experts was drawn from the following areas: hospital epidemiology and infection control, infectious diseases (including graduate training programs), clinical practice (including nursing, surgery, internal medicine, and pediatrics), pharmacy, administration, quality improvement, appropriateness evaluation, behavior modification, practice guideline development, medical informatics, and outcomes research. Representatives from appropriate federal agencies, the Joint Commission on Accreditation of Healthcare Organizations, and the pharmaceutical industry also participated.

EVIDENCE

Published literature, guidelines, expert opinion, and practical experience regarding efforts to improve antibiotic utilization and prevent and control the emergence and dissemination of antimicrobial-resistant microorganisms in hospitals.

CONSENSUS PROCESS

Participants were divided into two quality improvement teams: one focusing on improving antimicrobial usage and the other on preventing and controlling transmission of resistant microorganisms. The teams modeled the process a hospital might use to develop and implement a strategic plan to combat antimicrobial resistance.

CONCLUSIONS

Ten strategic goals and related process and outcome measures were agreed on. The five strategic goals to optimize antimicrobial use were as follows: optimizing antimicrobial prophylaxis for operative procedures; optimizing choice and duration of empiric therapy; improving antimicrobial prescribing by educational and administrative means; monitoring and providing feedback regarding antibiotic resistance; and defining and implementing health care delivery system guidelines for important types of antimicrobial use. The five strategic goals to detect, report, and prevent transmission of antimicrobial resistant organisms were as follows: to develop a system to recognize and report trends in antimicrobial resistance within the institution; develop a system to rapidly detect and report resistant microorganisms in individual patients and ensure a rapid response by caregivers; increase adherence to basic infection control policies and procedures; incorporate the detection, prevention, and control of antimicrobial resistance into institutional strategic goals and provide the required resources; and develop a plan for identifying, transferring, discharging, and readmitting patients colonized with specific antimicrobial-resistant pathogens.

The infection control committee

Hospital epidemiologists translate their expertise into institutional policy and gain the support of administrators through the infection control committee. Committee members have the important task of helping to disseminate information to all important hospital constituencies. The infection control team can facilitate its goals by properly preparing committee members for the meeting. A well-educated committee will approve policies efficiently. The committee periodically should reassess its accomplishments and goals. This article will explore the workings of the infection control committee and will suggest strategies that the hospital epidemiologist can use to make the committee an asset rather than a hindrance. an asset rather than a hindrance.

The Lowbury Lecture. The economics of nosocomial infections

A simple model of the costs and benefits of an infection control programme is presented. Liberal costs and conservative benefits were assumed. The concepts of crude and attributable mortality were applied to examine the cost per life year saved if a minority of infection-related deaths were prevented. An effective infection control programme is one of the most cost-beneficial medical interventions available in modern public health.

The significance of nasal carriage of Staphylococcus aureus and the incidence of postoperative wound infection

Staphylococcus aureus infections are associated with considerable morbidity and, in certain situations, mortality. The association between the nasal carriage of S. aureus and subsequent infection has been comprehensively established in a variety of clinical settings, in particular, patients undergoing haemodialysis and continuous ambulatory peritoneal dialysis (CAPD), and in patients undergoing surgery. Postoperative wound infections are associated with a high degree of morbidity and represent an important medical issue. Until recently, eradication of S. aureus nasal carriage by various topical and systemic agents had proved unsuccessful. Mupirocin is a novel topical antibiotic with excellent antibacterial activity against staphylococci. Recent studies have demonstrated that intranasal administration of mupirocin is effective in eradicating the nasal carriage of S. aureus and in reducing the incidence of S. aureus infections in haemodialysis and CAPD patients. It has been suggested that sufficient evidence now exists to test the hypothesis that eradication of the carrier state in surgical patients preoperatively may reduce the incidence of S. aureus postoperative wound infections.

Familial carriage of methicillin-resistant Staphylococcus aureus and subsequent infection in a premature neonate

During routine surveillance of patients in a Neonatal Intensive Care Unit (NICU), an alert infection-control practitioner confirmed the relationship of the index patient (sibling 3) who had a methicillin-resistant Staphylococcus aureus (MRSA) infection to an infant sibling (sibling 2) who had been admitted to the hospital 7 months previously with an MRSA infection. Cultures of nasal specimens obtained from the index patient's parents and two other siblings also yielded MRSA for two of the family members, the mother and sibling 1. The strains were typed by antibiogram, plasmid analysis, and genomic DNA typing. The isolates from sibling 1, sibling 2, the mother, and one isolate from sibling 3 were found to be identical by all techniques. The other isolates from sibling 3 shared the same genomic type but had no detectable plasmids. These findings suggest that transmission of this strain occurred at least three times within this family and that at least one family member was colonized with the same strain for 7 months or more. Recognition that family members may serve as reservoirs for nosocomial infections with MRSA raises important issues for infection control.

Molecular epidemiology of an outbreak of meningococcal disease in a university community

Over a 2-month period, five cases of serogroup C meningococcal disease occurred in Iowa City, Iowa. Two patients were unacquainted university students who had independently visited another university with endemic meningococcal disease. Isolates from these patients had DNA fingerprints identical to those of the isolates responsible for infections on the other campus. Three cases for which the patients' isolates had a different DNA fingerprint were linked to visiting a local tavern. To disrupt the outbreak, the University of Iowa offered free meningococcal vaccine to all students. This report demonstrates that outbreaks of meningococcal disease may be due to more than one circulating strain and illustrates the utility of pulsed-field gel electrophoresis in defining the molecular epidemiology of meningococcal infections.

Long-term survival and function after suspected gram-negative sepsis

OBJECTIVE

To determine the long-term (> 3 months) survival of septic patients, to develop mathematical models that predict patients likely to survive long-term, and to measure the health and functional status of surviving patients.

SETTING

A large tertiary care university hospital and an associated Veterans Affairs Medical Center.

DESIGN

From December 1986 to December 1990, a total of 103 patients with suspected gram-negative sepsis entered a double-blind, placebo-controlled efficacy trial of monoclonal antiendotoxin antibody. Of these, we followed up 100 patients for 7667 patient-months. Beginning in May 1992, we reviewed hospital records and contacted all known survivors. We measured the health status of all surviving patients.

MAIN OUTCOME MEASURES

The determinants of long-term survival (up to 6 years) were identified through two Cox proportional hazard regression models: one that included patient characteristics identified at the time of sepsis (bedside model) and another that included bedside, infection-related, and treatment characteristics (overall model).

RESULTS

Of the 60 patients in the cohort who died at a median interval of 30.5 days after sepsis, 32 died within the first month of the septic episode, seven died within 3 months, and four more died within 6 months. In the bedside multivariate model constructed to predict long-term survival, large hazard ratios (HRs) were associated with severity of underlying illness as classified by McCabe and Jackson criteria (for rapidly fatal disease, HR = 30.4, P < .001; for ultimately fatal disease, HR = 7.6, P < .001) and the use of vasopressors (HR = 2.5; P = .001). In the overall model for long-term survival, severity of underlying illness (rapidly fatal disease, HR = 23.7, P < .001; ultimately fatal disease, HR = 6.5, P < .001), number of active comorbid illnesses (HR = 1.3; P = .04), use of vasopressors at the time of sepsis (HR = 2.0; P = .02), and development of adult respiratory distress syndrome (HR = 2.3; P = .02) predicted patients most likely to die. The Acute Physiology and Chronic Health Evaluation II score was not a significant predictor of outcome when either model included the simpler McCabe and Jackson classification of underlying disease severity. We compared the health status scores with norms for the general population and found that patients with resolved sepsis reported more physical dysfunction (P < .001), including problems with work and activities of daily living (P = .02), and more poorly perceived general health (P < .01). In contrast, patients' scores for perceived emotional health were higher than those in the general population (P = .004). The mean Barthel score of our patients was 85 (100 = total independence) and the mean Eastern Cooperative Oncology Group score was 0.7 (0 = normal, 4 = 100% bedridden), suggesting that the patients' physical function was not normal.

CONCLUSIONS

At the onset of suspected gram-negative sepsis, severity of underlying illness and in-hospital use of vasopressors are strong and consistent predictors of short- and long-term survival. Our data validate the McCabe and Jackson severity of illness scoring system for predicting long-term survival after sepsis. Physical dysfunction and more poorly perceived general health occur commonly after sepsis.

Nosocomial bloodstream infections. Secular trends in rates, mortality, and contribution to total hospital deaths

BACKGROUND

Nosocomial bloodstream infections occur at a rate of 1.3 to 14.5 per 1000 hospital admissions and are believed to lead directly to 62,500 deaths per year in the United States. Measures of the incidence and the proportion of all hospital deaths related to deaths from these infections provide estimates of their impact. The objectives of the study were to characterize the secular trends in nosocomial bloodstream infection at a single institution and to estimate the population-attributable risk for death among patients experiencing the infection.

METHODS

A 12-year retrospective study using prospectively collected data from a hospital-wide surveillance system for nosocomial infections in a 900-bed tertiary care institution. All patients (N = 260,834) admitted to the institution between 1980 and 1992 were included in the study. Bloodstream infection rates were calculated for the 10 leading groups of pathogens, and trends were analyzed using simple linear regression. In-hospital mortality rates from patients who did or did not develop nosocomial blood stream infections were compared.

RESULTS

Between 1980 and 1992, a total of 3077 patients developed 3464 episodes of nosocomial bloodstream infection. The crude infection rates increased linearly from 6.7 to 18.4 per 1000 discharges (0.83 to 1.72 episodes per 1000 patient-days) during the 12-year study period (r = .87). Increases in the infection rates were due to gram-positive cocci (r = .96) and yeasts (r = .95) and essentially explained by infections caused by coagulase-negative staphylococci, Staphylococcus aureus, enterococci, and Candida species, respectively. Although the crude mortality in patients with nosocomial bloodstream infections decreased from 51% in 1981 to 29% in 1992, the in-hospital population-attributable mortality among infected patients increased from 3.55 deaths per 1000 discharges in 1981 to 6.22 per 1000 discharges in 1992 (r = .67). The etiologic fraction or the proportion of deaths in patients with bloodstream infection to all deaths occurring in the hospital increased from 11.4% in 1981 to 20.4% in 1992 (r = .59).

CONCLUSIONS

The incidence, the etiologic fraction, and the population-attributable risk for death among patients experiencing nosocomial bloodstream infections increased progressively during the last decade.

A second large controlled clinical study of E5, a monoclonal antibody to endotoxin: results of a prospective, multicenter, randomized, controlled trial. The E5 Sepsis Study Group

OBJECTIVE

To evaluate the safety and efficacy of E5, a murine, monoclonal antibody directed against endotoxin, in the treatment of patients with Gram-negative sepsis.

DESIGN

A multicenter, randomized, double-blind, placebo-controlled trial.

SETTING

Fifty-three hospitals across the United States, including university medical centers, Veterans Affairs Medical Centers, and community hospitals.

PATIENTS

847 patients were randomized into this study. Enrolled patients met criteria for three conditions: a) known or suspected Gram-negative infection; b) clinical evidence of sepsis; and c) signs of end-organ dysfunction. Patients with refractory shock were excluded from the study.

INTERVENTIONS

Two doses of E5 (2 mg/kg/day by intravenous infusion 24 hrs apart), or placebo that was identical in appearance were administered. In addition, all patients received standard supportive therapy and broad-spectrum antibiotics.

MEASUREMENTS AND MAIN RESULTS

The primary end point was mortality over 30 days. Secondary outcome measures included the resolution and prevention of organ failure in the same two populations. Additionally, the safety of E5 was evaluated. There was no significant improvement in survival over 30 days among patients with Gram-negative sepsis who received E5 compared with those patients who received placebo (n = 530; p = .21). In addition, E5 did not improve survival for patients with Gram-negative sepsis and organ failure (n = 139; p = .3). However, a significantly greater percentage of patients with Gram-negative sepsis experienced resolution of major organ failure if they received E5, compared with those patients who received placebo (n = 139; 48% E5 vs. 25% placebo; p = .005). This result extended to all patients who entered the study with one or more major organ failures, regardless of the etiology of the infection (n = 225; 41% E5 vs. 27% placebo; p = .024). E5 also provided protection against the development of some organ failures, but significant prevention was only observed for adult respiratory distress syndrome (p = .007) and central nervous system dysfunction (p = .050). Hypersensitivity reactions attributable to E5 occurred in 2.6% of patients. An asymptomatic antibody response occurred in 44% of the E5-treated patients and in 12% of the patients who received placebo.

CONCLUSIONS

In this study, E5 did not reduce mortality in nonshock patients with Gram-negative sepsis whether or not those patients also had organ failure. However, E5 did result in greater resolution of organ failure in patients with Gram-negative sepsis. This benefit extended to those patients with suspected Gram-negative etiology. This finding is important because patients with suspected Gram-negative sepsis and organ failure can be identified without waiting for culture results. In addition, E5 resulted in the prevention of adult respiratory distress syndrome and central nervous system organ failure. However, more studies are needed to determine if this result can be extended to organ failure in general. E5 is safe as a treatment for patients with Gram-negative sepsis.

Nosocomial candidemia: risk factors and attributable mortality

Over the past decade, the incidence of hospital-acquired bloodstream infections caused by Candida species has risen and the species associated with such infections have changed. The incidence of candidemia is dramatically higher in high-risk, critical-care units than in other parts of the hospital. Certain underlying physical conditions including acute leukemia, leukopenia, burns, gastrointestinal disease, and premature birth predispose patients to nosocomial candidemia. Independent risk factors include prior treatment with multiple antibiotics, prior Hickman catheterization, isolation of Candida species from sites other than the blood, and prior hemodialysis. In this article some of the challenges posed by the management of nosocomial candidemia are presented in three case studies. In addition, the results of several investigations of nosocomial candidemia at the University of Iowa Hospitals and Clinics are reviewed.

Vancomycin-resistant Enterococcus faecium bacteremia: risk factors for infection

We describe an outbreak of vancomycin-resistant Enterococcus faecium (vanA phenotype) bacteremia on the oncology ward of a tertiary care community hospital. In 10 of the 11 cases the patients had leukemia and were neutropenic (median duration of neutropenia, 21 days) at the time of bacteremia. On average, patients received six antibiotic agents for a total of 61 agent-days prior to development of vancomycin-resistant E. faecium bacteremia. The mortality rate was 73%. Molecular typing of 22 isolates revealed that the majority (83%) represented a common strain, indicating nosocomial spread. When the 11 cases were compared to 22 matched control patients, gastrointestinal colonization with vancomycin-resistant E. faecium (odds ratio [denominator, 0] infinity, P = .005) and the use of antimicrobial agents with significant activity against anaerobes (metronidazole, clindamycin, and imipenem; odds ratio infinity, P = .02) were found to be risk factors for the development of vancomycin-resistant E. faecium bacteremia. Since no proven therapy for such infection exists, there is an urgent need to identify effective measures to prevent and control the development of vancomycin-resistant E. faecium bacteremia.

Evidence of nosocomial spread of Candida albicans causing bloodstream infection in a neonatal intensive care unit

Candida albicans is an increasingly important bloodstream pathogen. We investigated a cluster of bloodstream infections in the neonatal intensive care unit (NICU) to determine whether nosocomial transmission occurred. Subjects included any patient in the NICU who developed clinically significant bloodstream infection with C. albicans from January 1984 to December 1987 (N = 7). Isolates were typed by restriction fragment length polymorphism analysis using a C. albicans-specific DNA probe (27A). Four of the neonates were infected from June to August 1984 (1.4 infections per 100 admissions) (the epidemic period) versus none in the period from January to May 1984, and three in the period from September 1984 to December 1987 (0.12 infections per 100 admissions) (P = .002). Three of the four patients in the epidemic period were infected with identical strains, readily distinguished from epidemiologically unrelated strains from the NICU. We conclude that nosocomial transmission of C. albicans occurred and that neonates in intensive care units may represent one group at increased risk.

Systemic inflammatory response syndrome, sepsis, severe sepsis and septic shock: incidence, morbidities and outcomes in surgical ICU patients

OBJECTIVES

To determine the incidence of systemic inflammatory response syndrome (SIRS), sepsis and severe sepsis in surgical ICU patients and define patient characteristics associated with their acquisition and outcome.

DESIGN

One-month prospective study of critically ill patients with a 28 day in-hospital follow up.

SETTING

Surgical intensive care unit (SICU) at a tertiary care institution.

METHODS

All patients (n = 170) admitted to the SICU between April 1 and April 30, 1992 were prospectively followed for 28 days. Daily surveillance was performed by two dedicated, specifically-trained research nurses. Medical and nursing chart reviews were performed, and follow up information at six and twelve months was obtained.

RESULTS

The in-hospital surveillance represented 2246 patient-days, including 658 ICU patient-days. Overall, 158 patients (93%) had SIRS for an incidence of 542 episodes/1000 patients-days. The incidence of SIRS in the ICU was even higher (840 episodes/1000 patients-days). A total of 83 patients (49%) had sepsis; among them 28 developed severe sepsis. Importantly, 13 patients had severe sepsis after discharge from the ICU. Patient groups were comparable with respect to age, sex ratio, and type of surgery performed. Apache II score on admission to the ICU and ASA score at time of surgery were significantly higher (p < 0.05) only for patients who subsequently developed severe sepsis. The crude mortality at 28 days was 8.2% (14/170); it markedly differed among patient groups: 6% for those with SIRS vs. 35% for patients with severe sepsis. Patients with sepsis and severe sepsis had a longer mean length of ICU stay (2.1 +/- 0.2 and 7.5 +/- 1.5, respectively) than those with SIRS (1.45 +/- 0.1) or control patients (1.16 +/- 0.1). Total length of hospital stay also markedly differed among groups (35 +/- 9 (severe sepsis), 24 +/- 2 (sepsis), 11 +/- 0.8 (SIRS), and 9 +/- 0.1 (controls, respectively).

CONCLUSIONS

Almost everyone in the SICU had SIRS. Therefore, because of its poor specificity, SIRS was not helpful predicting severe sepsis and septic shock. Patients who developed sepsis or severe sepsis had higher crude mortality and length of stay than those who did not. Studies designed to identify those who develop complications of SIRS would be very useful.

The hospital epidemiologist: practical ideas

The modern hospital epidemiologist has broad perspectives and influence across clinical departmental lines. The opportunities to improve patient care by expanding traditional areas of focus beyond infection control are great. Useful skills include epidemiology, communication, and respect for colleagues.

The natural history of the systemic inflammatory response syndrome (SIRS). A prospective study

OBJECTIVE

Define the epidemiology of the four recently classified syndromes describing the biologic response to infection: systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, and septic shock.

DESIGN

Prospective cohort study with a follow-up of 28 days or until discharge if earlier.

SETTING

Three intensive care units and three general wards in a tertiary health care institution.

METHODS

Patients were included if they met at least two of the criteria for SIRS: fever or hypothermia, tachycardia, tachypnea, or abnormal white blood cell count.

MAIN OUTCOMES MEASURES

Development of any stage of the biologic response to infection: sepsis, severe sepsis, septic shock, end-organ dysfunction, and death.

RESULTS

During the study period 3708 patients were admitted to the survey units, and 2527 (68%) met the criteria for SIRS. The incidence density rates for SIRS in the surgical, medical, and cardiovascular intensive care units were 857, 804, and 542 episodes per 1000 patient-days, respectively, and 671, 495, and 320 per 1000 patient-days for the medical, cardiothoracic, and general surgery wards, respectively. Among patients with SIRS, 649 (26%) developed sepsis, 467 (18%) developed severe sepsis, and 110 (4%) developed septic shock. The median interval from SIRS to sepsis was inversely correlated with the number of SIRS criteria (two, three, or all four) that the patients met. As the population of patients progressed from SIRS to septic shock, increasing proportions had adult respiratory distress syndrome, disseminated intravascular coagulation, acute renal failure, and shock. Positive blood cultures were found in 17% of patients with sepsis, in 25% with severe sepsis, and in 69% with septic shock. There were also stepwise increases in mortality rates in the hierarchy from SIRS, sepsis, severe sepsis, and septic shock: 7%, 16%, 20%, and 46%, respectively. Of interest, we also observed equal numbers of patients who appeared to have sepsis, severe sepsis, and septic shock but who had negative cultures. They had been prescribed empirical antibiotics for a median of 3 days. The cause of the systemic inflammatory response in these culture-negative populations is unknown, but they had similar morbidity and mortality rates as the respective culture-positive populations.

CONCLUSIONS

This prospective epidemiologic study of SIRS and related conditions provides, to our knowledge, the first evidence of a clinical progression from SIRS to sepsis to severe sepsis and septic shock.

Efficient detection and long-term persistence of the carriage of methicillin-resistant Staphylococcus aureus

The natural history of the carriage of methicillin-resistant Staphylococcus aureus (MRSA) was examined in a 9-year retrospective cohort study of 102 known carriers. The populations studied consisted of patients admitted to a university hospital from 1989 through 1991; a review extending back to January 1983 was conducted. The focuses of the study included the duration of carriage among patients who were known to have carried MRSA previously and who were readmitted to the hospital (36 patients) and the optimal anatomic site for screening (66 patients). Cultures of the nares (sensitivity, 93%; negative predictive value, 95%) were considerably more valuable for the detection of MRSA colonization than were cultures of cutaneous sites of the axilla, groin, and perineum (sensitivity, < or = 39%; negative predictive value, < or = 69%). The estimated half-life of MRSA colonization in this special population of patients was approximately 40 months. Restriction enzyme analysis of plasmid types of paired isolates from the 12 patients with MRSA carriage persisting for > 12 months revealed five instances (42%) in which both isolates were of the same type. In summary, our results indicate that the majority of readmitted carriers harbor MRSA for > 3 years and that, in this population, culture of the anterior nares alone (with culture of wound or sputum, when present) is a valid and efficient method for the detection of persistent MRSA carriage.