A control programme for MRSA (methicillin-resistant Staphylococcus aureus) containment in a paediatric intensive care unit: evaluation and impact on infections caused by other micro-organisms

What To Think If the Results of the National Institutes of Health Randomized Trial of Methicillin-ResistantStaphylococcus aureusand Vancomycin-ResistantEnterococcusControl Measures Are Negative (and Other Advice to Young Epidemiologists): A Review and an Au Revoir

The incidence of methicillin-resistantStaphylococcus aureus(MRSA) and vancomycin-resistantEnterococcus(VRE) infections continues to rise in National Nosocomial Infections Surveillance system hospitals, and these pathogens are reportedly causing more than 100,000 infections and many deaths each year in US healthcare facilities. This has led some to insist that control measures are now urgently needed, but several recent articles have suggested that isolation of patients does not work, is not needed, or is unsafe, or that a single cluster-randomized trial could be used to decide such matters. At least 101 studies have reported controlling MRSA infection and 38 have reported controlling VRE infection by means of active detection by surveillance culture and use of isolation for all colonized patients in healthcare settings where the pathogens are epidemic or endemic, in academic and nonacademic hospitals, and in acute care, intensive care, and long-term care settings. MRSA colonization and infection have been controlled to exceedingly low levels in multiple nations and in the state of Western Australia for decades by use of active detection and isolation. Studies suggesting problems with using such data to control MRSA colonization and infection have their own problems, which are discussed. Randomized trials are epidemiologic tools that can sometimes provide erroneous results, and they have not been considered necessary for studying isolation before it is used to control other important infections, such as tuberculosis, smallpox, and severe acute respiratory syndrome. No single epidemiologic study should be considered definitive. One should always weigh all available evidence. Infection with antibiotic-resistant pathogens such as MRSA and VRE is controllable to a low level by active detection and isolation of colonized and infected patients. Effective measures should be used to minimize the morbidity and mortality attributable to these largely preventable infections.

Immunisation With Immunodominant Linear B Cell Epitopes Vaccine of Manganese Transport Protein C Confers Protection against Staphylococcus aureus Infection

Vaccination strategies for Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA) infections have attracted much research attention. Recent efforts have been made to select manganese transport protein C, or manganese binding surface lipoprotein C (MntC), which is a metal ion associated with pathogen nutrition uptake, as potential candidates for an S. aureus vaccine. Although protective humoral immune responses to MntC are well-characterised, much less is known about detailed MntC-specific B cell epitope mapping and particularly epitope vaccines, which are less-time consuming and more convenient. In this study, we generated a recombinant protein rMntC which induced strong antibody response when used for immunisation with CFA/IFA adjuvant. On the basis of the results, linear B cell epitopes within MntC were finely mapped using a series of overlapping synthetic peptides. Further studies indicate that MntC113-136, MntC209-232, and MntC263-286 might be the original linear B-cell immune dominant epitope of MntC, furthermore, three-dimensional (3-d) crystal structure results indicate that the three immunodominant epitopes were displayed on the surface of the MntC antigen. On the basis of immunodominant MntC113-136, MntC209-232, and MntC263-286 peptides, the epitope vaccine for S. aureus induces a high antibody level which is biased to TH2 and provides effective immune protection and strong opsonophagocytic killing activity in vitro against MRSA infection. In summary, the study provides strong proof of the optimisation of MRSA B cell epitope vaccine designs and their use, which was based on the MntC antigen in the development of an MRSA vaccine.

An integrative review of infection prevention and control programs for multidrug-resistant organisms in acute care hospitals: a socio-ecological perspective

BACKGROUND

The infection rates of multidrug-resistant organisms (MDRO) are increasing in Canada and the United States. The prevention and control of MDRO infections remain an important issue in acute care hospitals. Although comprehensive infection prevention and control programs have been recommended, there is little evidence to date of their effectiveness or of what aspects are most important.

OBJECTIVES

Our objectives were to review and critique the literature on the relationship between an MDRO infection and control program and MDRO rates in acute care hospitals.

METHODS

Studies including original research published between January 1, 1998, and May 14, 2009, were identified through MEDLINE, CINAHL, EMBASE, PUBMED, The Cochrane Library, and expert consultation. A comprehensive search strategy was developed with a librarian to find studies that covered the main subject areas of this integrative review.

RESULTS

Of the 1,382 papers retrieved, 47 were reviewed, and 32 studies met the inclusion criteria. The interventions in the included studies were assessed using the tier 1/tier 2 framework. A total of 18 (56.25%) studies had an administrative measure as an intervention; 20 (62.5%) studies had education and training of health care personnel; 8 (25.0%) studies had judicious use of antimicrobial agents; 17 (53.1%) studies used surveillance; 24 (75.0%) studies had infection control precautions to prevent transmission; 7 studies (21.9%) introduced environmental measures; and 9 (28.1%) studies used patient decolonization. Although all the 32 studies were quasiexperimental studies, only 2 (5.9%) studies provided sample size calculations, and only 5 studies reported confounding factors. Whereas 27 used an interrupted time series design and 2 were controlled pre- and post-intervention designs, 3 were pre- and post-intervention without control groups.

CONCLUSION

This integrative review demonstrated that the evidence of the relationship between MDRO infection prevention and control programs and the rates of MDRO is weak. Although major methodologic weaknesses exist in the published literature making it not possible to exclude other plausible explanations for the reduction of the acquisition of MDRO, the overall evidence does support the use of multiple interventions to reduce the rates of MDRO in acute care hospitals. Whereas it is unclear which bundles of interventions are effective, there is a clear suggestion that multiple simultaneous interventions can be effective in reducing MDRO infections. In addition, despite the limitations of interrupted time series, multiple studies employing active surveillance cultures were associated with reduced MDRO infections. Future individual reports of outbreaks and intervention studies should be written in a standardized manner using the recommended Outbreak Reports and Intervention Studies of Nosocomial Infection (ORION) guidelines. Further research is needed on the proposed tier 1/tier 2 framework clearly indicating all the interventions implemented.

Epidemiology and virulence insights from MRSA and MSSA genome analysis

Staphylococcus aureus is a major human pathogen responsible for a wide diversity of infections ranging from localized to life threatening diseases. From 1961 and the emergence of methicillin-resistant S. aureus (MRSA), this bacterium has shown a particular capacity to survive and adapt to drastic environmental changes and since the beginning of the 1990s it has spread worldwide. Until recently, S. aureus was considered as the prototype of a nosocomial pathogen but it has now been recognized as an agent responsible for outbreaks in the community. Several recent reports suggest that the epidemiology of MRSA is changing. Understanding of pathogenicity, virulence and emergence of epidemic clones within MRSA populations is not clearly defined, despite several attempts to identify common molecular features between strains that share similar epidemiological and/or virulence behavior. These studies included: pattern profiling of bacterial adhesins, analysis of clonal complex groups, molecular genotyping and enterotoxin content analysis. To date, all approaches failed to find a correlation between molecular determinants and clinical outcomes. We hypothesize that the capacity of the bacterium to become more invasive or virulent is determined by genetics. The utilization of massively parallel methods of analysis is therefore ideal to study the contribution of genetics. Therefore, this article focuses on the entire genome including coding sequences as well as noncoding sequences. This high resolution approach allows the monitoring micro- and macroevolution of MRSA and identification of specific genomic markers of evolution of invasive or highly virulent phenotypes.

Risk factors for healthcare-associated infection in pediatric intensive care units: a systematic review

A systematic review of observational studies on risk factors for healthcare-associated infection in pediatric Intensive Care Units (ICU) was carried out. Studies indexed in MEDLINE, LILACS, Cochrane, BDENF, CAPES databases published in English, French, Spanish or Portuguese between 1987 and 2006 were included and cross references added. Key words for search were 'cross infection' and 'Pediatric Intensive Care Units' with others sub-terms included. 11 studies were selected from 419 originally found: four studies had healthcare-associated infection as the main outcome without a specific site; three articles identified factors associated with lower respiratory tract infection (pneumonia or tracheitis); three articles were concerned with laboratory-confirmed bloodstream infection; and a single retrospective study analyzed urinary tract infection. The production of evidence on risk factors Paediatric ICU has not kept up the same pace of that on adult - there are few studies with adequate design and statistical analysis. The methodological diversity of the studies did not allow for a summarized measurement of risk factors.

Acquisition and cross-transmission of Staphylococcus aureus in European intensive care units

OBJECTIVE

To study the acquisition and cross-transmission of Staphylococcus aureus in different intensive care units (ICUs).

METHODS

We performed a multicenter cohort study. Six ICUs in 6 countries participated. During a 3-month period at each ICU, all patients had nasal and perineal swab specimens obtained at ICU admission and during their stay. All S. aureus isolates that were collected were genotyped by spa typing and multilocus variable-number tandem-repeat analysis typing for cross-transmission analysis. A total of 629 patients were admitted to ICUs, and 224 of these patients were found to be colonized with S. aureus at least once during ICU stay (22% were found to be colonized with methicillin-resistant S. aureus [MRSA]). A total of 316 patients who had test results negative for S. aureus at ICU admission and had at least 1 follow-up swab sample obtained for culture were eligible for acquisition analysis.

RESULTS

A total of 45 patients acquired S. aureus during ICU stay (31 acquired methicillin-susceptible S. aureus [MSSA], and 14 acquired MRSA). Several factors that were believed to affect the rate of acquisition of S. aureus were analyzed in univariate and multivariate analyses, including the amount of hand disinfectant used, colonization pressure, number of beds per nurse, antibiotic use, length of stay, and ICU setting (private room versus open ICU treatment). Greater colonization pressure and a greater number of beds per nurse correlated with a higher rate of acquisition for both MSSA and MRSA. The type of ICU setting was related to MRSA acquisition only, and the amount of hand disinfectant used was related to MSSA acquisition only. In 18 (40%) of the cases of S. aureus acquisition, cross-transmission from another patient was possible.

CONCLUSIONS

Colonization pressure, the number of beds per nurse, and the treatment of all patients in private rooms correlated with the number of S. aureus acquisitions on an ICU. The amount of hand disinfectant used was correlated with the number of cases of MSSA acquisition but not with the number of cases of MRSA acquisition. The number of cases of patient-to-patient cross-transmission was comparable for MSSA and MRSA.

Overcrowding and understaffing in modern health-care systems: key determinants in meticillin-resistant Staphylococcus aureus transmission

Recent decades have seen the global emergence of meticillin-resistant Staphylococcus aureus (MRSA), causing substantial health and economic burdens on patients and health-care systems. This epidemic has occurred at the same time that policies promoting higher patient throughput in hospitals have led to many services operating at, or near, full capacity. A result has been limited ability to scale services according to fluctuations in patient admissions and available staff, and hospital overcrowding and understaffing. Overcrowding and understaffing lead to failure of MRSA control programmes via decreased health-care worker hand-hygiene compliance, increased movement of patients and staff between hospital wards, decreased levels of cohorting, and overburdening of screening and isolation facilities. In turn, a high MRSA incidence leads to increased inpatient length of stay and bed blocking, exacerbating overcrowding and leading to a vicious cycle characterised by further infection control failure. Future decision making should use epidemiological and economic evidence to evaluate the effect of systems changes on the incidence of MRSA infection and other adverse events.

Multidrug-resistant bacteria in hospitalized children: a 5-year multicenter study

OBJECTIVE

The objective of this study was to determine the incidence of multidrug-resistant bacteria in hospitalized children.

METHODS

This multicenter study was conducted in 5 hospitals in the Paris area from 1999 to 2003. We recorded all isolations of multidrug-resistant bacteria from clinical samples that were obtained from hospitalized children. Strains that were isolated during systematic screening for carriers were excluded.

RESULTS

The mean incidences were 0.9 per 1000 hospitalization-days for methicillin-resistant Staphylococcus aureus, 0.45 for extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, 0.32 for extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, 0.40 for Enterobacter species with derepressed cephalosporinase, and 0.01 for vancomycin-resistant Enterococcus. The incidences per 1000 hospitalization-days of methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, and Enterobacter species with derepressed cephalosporinase decreased significantly from 1999 to 2003, whereas the incidence of vancomycin-resistant Enterococcus remained very low. The proportion of resistant strains within the species did not vary significantly for methicillin-resistant Staphylococcus aureus (11% to 9.6%), extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae (1.1%), and vancomycin-resistant Enterococcus (0.03% to 0.023%). In contrast, the frequency of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae decreased from 31.6% to 7.4%, and that of Enterobacter species with derepressed cephalosporinase decreased from 38.8% to 18.5%.

CONCLUSIONS

We report significant decreases in the incidence of methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, and Enterobacter species with derepressed cephalosporinase in hospitalized children during a 5-year period.

Costs of hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) and its control

For most countries badly affected by methicillin-resistant Staphylococcus aureus (MRSA) there have been many years of debate about its relative virulence compared with methicillin-susceptible S. aureus (MSSA) and whether it could be controlled. Now that it is endemic in the majority of hospitals around the world, it is clear that it is at least as virulent as MSSA and is an additional burden of healthcare-acquired infection. There is increasing evidence that, despite this endemicity, control efforts can be successful, although they are often perceived as expensive. In reality, there is a large body of consistent evidence that control is highly cost effective, particularly in the context of the huge societal costs of MRSA and the future ever-greater threats that it poses.

Effectiveness of barrier precautions and surveillance cultures to control transmission of multidrug-resistant organisms: a systematic review of the literature

BACKGROUND

Despite the priority placed on preventing transmission of multidrug-resistant organisms (MDROs) in health care facilities, there is a lack of consensus among recommended infection control guidelines. We focused on control measures that have a great potential to affect patient care, patient services, and hospital cost/resources: barrier precautions/patient isolation and surveillance cultures.

METHODS

We conducted a systematic review of the literature and published English-language guidelines pertaining to the use of barrier precautions/patient isolation and surveillance cultures to prevent the transmission of MDROs. The recommendations made by the published guidelines were summarized and compared. The primary research studies identified through our literature search were evaluated for study quality. We then summarized the outcomes of the studies with the highest quality scores and made recommendations for future work.

RESULTS

A total of 29 studies were included in our assessment of study quality; of those, 7 studies were of high quality.

CONCLUSION

This systematic review identified key gaps in the literature including a need for greater monitoring of implementation of the interventions, more cost analyses of interventions, determining the independent contribution of specific interventions, and identifying the minimum interventions needed to reduce transmission.

Impact of selective screening in the emergency department on meticillin-resistant Staphylococcus aureus control programmes

Identification of the meticillin-resistant Staphylococcus aureus (MRSA) reservoir by active screening followed by the implementation of contact precautions is one of the major components of MRSA control programmes. The objective of this study was to evaluate the results of a programme of selective screening in an emergency department (ED) and the appropriateness of the contact precautions implemented. This was estimated by distinguishing necessary and unnecessary days of contact precautions. This estimation was performed for all days of contact precautions and, more specifically, for days of preventive contact precautions implemented before the availability of screening results. During a three-year period, screening of MRSA carriers was performed on 0.95% (N=605) of patients visiting the emergency ward. Among the 193 (31.9%) MRSA carriers identified, 159 were hospitalized in the short-length-hospitalization area (SLHA) of the ED and/or in other wards. Among the 140 patients admitted to the SLHA, 44 were hospitalized for at least 48 h, with a mean length of hospitalization of 5.9 days. The cumulative duration of hospitalization of carriers identified by screening was 1897 days. In total, 2370 days of contact precautions (including 924 days of preventive precautions) were implemented for patients screened in the ED. Considering the whole hospital, the appropriateness of this entire programme of contact precautions for patients screened in the ED was 80.0% (52.1% for the SLHA), whereas the specific appropriateness of preventive isolation days was 48.6% (43.6% for the SLHA). This study underscores the risk of MRSA cross-transmission in the SLHA, and the usefulness of implementing a control programme of screening carriers in the ED.

[Staphylococcus aureus infections: new challenges from an old pathogen]

Staphylococcus aureus is a versatile organism with several virulent characteristics and resistance mechanisms at its disposal. It is also a significant cause of a wide range of infectious diseases in humans. S. aureus often causes life-threatening deep seated infections like bacteremia, endocarditis and pneumonia. While traditionally confined mostly to the hospital setting, methicillin-resistant S. aureus (MRSA) is now rapidly becoming rampant in the community. Community-acquired MRSA is particularly significant because of its potential for unchecked spread within households and its propensity for causing serious skin and pulmonary infections. Because of the unfavorable outcome of many MRSA infections with the standard glycopeptide therapy, new antimicrobial agents belonging to various classes have been introduced and have been evaluated in clinical trials for their efficacy in treating resistant staphylococcal infections. A number of preventive strategies have also been suggested to contain the spread of such infections. In this review, we address the recent changes in the epidemiology of S. aureus and their impact on the clinical manifestations and management of serious infections. We also discuss new treatment modalities for MRSA infections and emphasize the importance of preventive approaches.

Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities

Meticillin-resistant Staphylococcus aureus (MRSA) remains endemic in many UK hospitals. Specific guidelines for control and prevention are justified because MRSA causes serious illness and results in significant additional healthcare costs. Guidelines were drafted by a multi-disciplinary group and these have been finalised following extensive consultation. The recommendations have been graded according to the strength of evidence. Surveillance of MRSA should be undertaken in a systematic way and should be fed back routinely to healthcare staff. The inappropriate or unnecessary use of antibiotics should be avoided, and this will also reduce the likelihood of the emergence and spread of strains with reduced susceptibility to glycopeptides, i.e. vancomycin-intermediate S. aureus/glycopeptide-intermediate S. aureus (VISA/GISA) and vancomycin-resistant S. aureus (VRSA). Screening for MRSA carriage in selected patients and clinical areas should be performed according to locally agreed criteria based upon assessment of the risks and consequences of transmission and infection. Nasal and skin decolonization should be considered in certain categories of patients. The general principles of infection control should be adopted for patients with MRSA, including patient isolation and the appropriate cleaning and decontamination of clinical areas. Inadequate staffing, especially amongst nurses, contributes to the increased prevalence of MRSA. Laboratories should notify the relevant national authorities if VISA/GISA or VRSA isolates are identified.

Ecological theory suggests that antimicrobial cycling will not reduce antimicrobial resistance in hospitals

Hospital-acquired infections caused by antibiotic-resistant bacteria pose a grave and growing threat to public health. Antimicrobial cycling, in which two or more antibiotic classes are alternated on a time scale of months to years, seems to be a leading candidate in the search for treatment strategies that can slow the evolution and spread of antibiotic resistance in hospitals. We develop a mathematical model of antimicrobial cycling in a hospital setting and use this model to explore the efficacy of cycling programs. We find that cycling is unlikely to reduce either the evolution or the spread of antibiotic resistance. Alternative drug-use strategies such as mixing, in which each treated patient receives one of several drug classes used simultaneously in the hospital, are predicted to be more effective. A simple ecological explanation underlies these results. Heterogeneous antibiotic use slows the spread of resistance. However, at the scale relevant to bacterial populations, mixing imposes greater heterogeneity than does cycling. As a consequence, cycling is unlikely to be effective and may even hinder resistance control. These results may explain the limited success reported thus far from clinical trials of antimicrobial cycling.

Isolation measures in the hospital management of methicillin resistant Staphylococcus aureus (MRSA): systematic review of the literature

OBJECTIVE

To evaluate the evidence for the effectiveness of isolation measures in reducing the incidence of methicillin resistant Staphylococcus aureus (MRSA) colonisation and infection in hospital inpatients.

DESIGN

Systematic review of published articles.

DATA SOURCES

Medline, Embase, CINAHL, Cochrane Library, System for Information on Grey Literature in Europe (SIGLE), and citation lists (1966-2000).

REVIEW METHODS

Articles reporting MRSA related outcomes and describing an isolation policy were selected. No quality restrictions were imposed on studies using isolation wards or nurse cohorting. Other studies were included if they were prospective or employed planned comparisons of retrospective data.

RESULTS

46 studies were accepted; 18 used isolation wards, nine used nurse cohorting, and 19 used other isolation policies. Most were interrupted time series, with few planned formal prospective studies. All but one reported multiple interventions. Consideration of potential confounders, measures to prevent bias, and appropriate statistical analysis were mostly lacking. No conclusions could be drawn in a third of studies. Most others provided evidence consistent with a reduction of MRSA acquisition. Six long interrupted time series provided the strongest evidence. Four of these provided evidence that intensive control measures including patient isolation were effective in controlling MRSA. In two others, isolation wards failed to prevent endemic MRSA.

CONCLUSION

Major methodological weaknesses and inadequate reporting in published research mean that many plausible alternative explanations for reductions in MRSA acquisition associated with interventions cannot be excluded. No well designed studies exist that allow the role of isolation measures alone to be assessed. None the less, there is evidence that concerted efforts that include isolation can reduce MRSA even in endemic settings. Current isolation measures recommended in national guidelines should continue to be applied until further research establishes otherwise.

Control of endemic MRSA-what is the evidence? A personal view

Although there is extensive literature on the control of MRSA, when that concerning epidemics is excluded, only a limited amount remains regarding the control of endemic MRSA. Several guidelines have been recently published recommending stringent control measures, which are often suggested based on their success in controlling MRSA outbreaks in hospitals with few MRSA or in containing MRSA cases introduced into a hospital with no MRSA. In these settings, multiple measures are usually introduced with apparently successful results. However, results may not be generalizable to other settings and we do not know the minimum effective measures required for MRSA containment. This paper aims critically to review the literature to determine whether evidence exists for the value of the infection control measures that are widely recommended in the endemic setting. Much of this literature is based on observational studies, with few randomized, controlled trials having been conducted. More well-designed studies are required before many of the principles on which we build infection control programmes can be regarded as evidence based.

Safe paediatric intensive care. Part 2: workplace organisation, critical incident monitoring and guidelines

In order to optimise safety within the paediatric intensive care unit (PICU), it is essential to optimise organisation, identify problem areas and implement standards and guidelines for safe practice (with appropriate monitoring). Organisational issues have a major impact on safety: the introduction and-recently-centralisation of paediatric intensive care, the appointment of dedicated paediatric intensivists, nursing staffing, handovers, rounds, the number of work hours and night shifts with the associated problems of disturbed circadian rhythms. The technique of voluntary, anonymous, non-punitive critical incident reporting has the potential to identify incidents and latent errors before they become self-evident through a major incident. This systems approach focuses on organisational and communication problems. Standards and guidelines may help in weighing up the benefits and risks of invasive procedures, and interventional studies have shown that implementation of standards and guidelines can improve outcome. Mortality prediction models enable us to monitor quality of care and, thus, to investigate the best ways of organising intensive care and monitoring the effects of changes in practice.

Persistent colonization and the spread of antibiotic resistance in nosocomial pathogens: resistance is a regional problem

Infections with antibiotic-resistant bacteria (ARB) in hospitalized patients are becoming increasingly frequent despite extensive infection-control efforts. Infections with ARB are most common in the intensive care units of tertiary-care hospitals, but the underlying cause of the increases may be a steady increase in the number of asymptomatic carriers entering hospitals. Carriers may shed ARB for years but remain undetected, transmitting ARB to others as they move among hospitals, long-term care facilities, and the community. We apply structured population models to explore the dynamics of ARB, addressing the following questions: (i) What is the relationship between the proportion of carriers admitted to a hospital, transmission, and the risk of infection with ARB? (ii) How do frequently hospitalized patients contribute to epidemics of ARB? (iii) How do transmission in the community, long-term care facilities, and hospitals interact to determine the proportion of the population that is carrying ARB? We offer an explanation for why ARB epidemics have fast and slow phases and why resistance may continue to increase despite infection-control efforts. To successfully manage ARB at tertiary-care hospitals, regional coordination of infection control may be necessary, including tracking asymptomatic carriers through health-care systems.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus strains causing neonatal toxic shock syndrome-like exanthematous disease in neonatal and perinatal wards

Neonatal toxic shock syndrome-like exanthematous disease (NTED) is a new neonatal disease caused by toxic shock syndrome toxin 1 (TSST-1). We conducted a prospective surveillance study and characterized the methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from patients with NTED and compared them with the strains from patients with other MRSA infections and asymptomatic carriers. The study was performed in the neonatal intensive care unit and a general neonatal and maternal ward in the Tokyo Women's Medical University Hospital (TWMUH) from September to December 1998. Among 103 patients eligible for the study, MRSA was detected in 62 (60.2%) newborns; of these 62 newborns, 8 (12.9%) developed NTED, 1 (1.6%) had another MRSA infection, and 53 (85.5%) were asymptomatic MRSA carriers. Sixty-nine MRSA strains were obtained from the 62 newborns. DNA fingerprinting by pulsed-field gel electrophoresis showed two clusters: clone A with 8 subtypes and clone B. Sixty-seven of the 69 MRSA strains (97.1%) belonged to clone A, and type A1 was the most predominant (42 of 69 strains; 60.9%) in every neonatal and perinatal ward. All but one of the clone A strains had the TSST-1 and staphylococcal enterotoxin C genes. We also analyzed eight MRSA strains from eight NTED patients in five hospitals in Japan other than TWMUH. All the MRSA strains from NTED patients also belonged to clone A. These results suggest that a single clone that predominated in the neonatal wards of six hospitals might have caused NTED. However, the occurrence of NTED might not be dependent on the presence of an NTED-specific strain.

Nosocomial transmission of methicillin-resistant Staphylococcus aureus: a blinded study to establish baseline acquisition rates

OBJECTIVE

To define the extent of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to a tertiary-care hospital.

DESIGN

A blinded, prospective surveillance culture study of patients admitted to the hospital to determine the transmission (acquisition) rate of MRSA. Risk factors associated with the likelihood of MRSA colonization on admission were investigated.

SETTING

Tertiary-care military medical facility.

PARTICIPANTS

All patients admitted to the medicine, surgery, and pediatric wards, and to the medical, surgical, and pediatric intensive care units were eligible for inclusion.

RESULTS

Five hundred thirty-five admission and 374 discharge samples were collected during the study period. One hundred forty-one patients were colonized with methicillin-susceptible S. aureus (MSSA) and 20 patients (3.7%) were colonized with MRSA on admission. Of the 354 susceptible patients, 6 acquired MRSA during the study for a transmission rate of 1.7%. Patients colonized with MRSA on admission were more likely to be older than non-colonized or MSSA-colonized patients, to have received antibiotics within the past year, to have been hospitalized within the prior 3 years, or to have a known history of MRSA. Patients acquiring MRSA had an average hospital stay of 17.7 days compared with 5.3 days for those who did not acquire MRSA. Pulsed-field gel electrophoresis of the 6 MRSA isolates from patients who acquired MRSA revealed 4 distinct band patterns.

CONCLUSIONS

Most patients colonized with MRSA were identified on admission samples. Surveillance cultures of patients admitted may help to prevent MRSA transmission and infection.

Rapid detection of methicillin-resistant Staphylococcus aureus directly from sterile or nonsterile clinical samples by a new molecular assay

A rapid procedure was developed for detection and identification of methicillin-resistant Staphylococcus aureus (MRSA) directly from sterile sites or mixed flora samples (e.g., nose or inguinal swabs). After a rapid conditioning of samples, the method consists of two main steps: (i) immunomagnetic enrichment in S. aureus and (ii) amplification-detection profile on DNA extracts using multiplex quantitative PCR (5'-exonuclease qPCR, TaqMan). The triplex qPCR assay measures simultaneously the following targets: (i) mecA gene, conferring methicillin resistance, common to both S. aureus and Staphylococcus epidermidis; (ii) femA gene from S. aureus; and (iii) femA gene from S. epidermidis. This quantitative approach allows discrimination of the origin of the measured mecA signal. qPCR data were calibrated using two reference strains (MRSA and methicillin-resistant S. epidermidis) processed in parallel to clinical samples. This 96-well format assay allowed analysis of 30 swab samples per run and detection of the presence of MRSA with exquisite sensitivity compared to optimal culture-based techniques. The complete protocol may provide results in less than 6 h (while standard procedure needs 2 to 3 days), thus allowing prompt and cost-effective implementation of contact precautions.

Appropriate use of antibiotics for common infections in an era of increasing resistance

In many respects, antibiotics have changed medicine forever. Countless lives have been enhanced and saved with antibiotic use. Unfortunately, the medical community has opened Pandora's box through the casual distribution of outpatient antibiotics. Society will indeed suffer, as well as the medical profession, if antibiotics are not used judiciously. To date, the rate of penicillin resistance has steadily risen in North America and in many other areas of the world. Much of the increase in resistance has been caused by the distribution of antibiotics for viral infections (e.g., bronchitis, colds, or purulent nasal discharge) as well as nonstreptococcal throat infections. Parental pressure for physicians to prescribe antibiotics also has contributed to the rise in antibiotic resistance. The authors have discussed many common pediatric ED infections and have illustrated the key points for making the diagnosis of each. In addition, the authors also recommend the appropriate choice of antibiotics for each disease process, with an emphasis on narrow-spectrum, first-line antimicrobials. Physicians, as the "holders of the prescription pad," should be aware of the problems with increasing bacterial resistance especially ED practitioners who work on the front line. In addition, families and patients should be educated about the harm of inappropriate antibiotic use. The AAP publishes pamphlets for parents that discuss these issues. It is believed, as was seen in Finland and Japan, that judicious use of antibiotics leads to a decrease in resistant bacteria and prolong antibiotic usefulness. This is an issue of great importance to the long-term health of patients. What Benjamin Rush stated in 1789 is true today: "Do not condemn, or oppose, unnecessarily, the simple, prescriptions of your patients. Yield to them in matters of little consequence but maintain an inflexible authority over matters that are essential to life."

Evaluation of the contribution of isolation precautions in prevention and control of multi-resistant bacteria in a teaching hospital

From February 1999 to January 2000, a control programme to prevent the spread multi-resistant bacteria (MRB) was implemented in a French teaching hospital. This programme focused on methicillin-resistant Staphylococcus aureus (MRSA) and Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBL), and was based on the application of barrier precautions (washing hands with antiseptic soaps, wearing disposable gloves and gowns, identifying MRB carriers). No changes in antibiotic policy occurred during the year. Our aim was to conduct an evaluation of this programme by measuring incidence rates. Concurrently, the effect of barrier precautions was estimated in an indirect way, by documenting the availability of barrier precautions in MRB carriers' rooms and by analysing the monthly correlation between the supply of such material and the theoretical cumulated length of MRB carriers' isolation in six randomized wards. All MRB isolated in hospitalized patients were recorded, and differentiated between acquisition in our hospital or from elsewhere. For the analysis of trends, the year was divided in three periods of four months. Over the year, the global MRB incidence was 1.26 per 1000 patient-days (PD) [95% confidence interval (95%CI)=1.16-1.36]. The MRSA incidence was 0.89 per 1000 PD (95%CI=0.81- 0.97) and the ESBL incidence was 0.38 per 1000 PD (95% CI=0.33-0.43). The MRB incidence decreased significantly in all types of specialties except for surgical wards. The incidence decreased by 17.9% for MRSA, 54.9% for ESBL and 34.8% for both MRB. Concurrently, the proportion of strains acquired in our hospital decreased for MRSA (P for trend > or = 0.05) and ESBL (P for trend > or = 0.01), whereas the incidence of imported strains increased slightly. The proportion of multiresistant strains in S. aureus (36.8%) and Enterobacter aerogenes (37.0%) remained similar throughout the year. Thus, the decrease of the incidence concerned both resistant and susceptible strains. The availability of antiseptic soaps increased significantly (P for trend > or = 0.01). The amount of antiseptic soap ordered and the theoretical lengths of isolation were correlated on a monthly basis (Spearman coefficient = 0.72; P > or = 0.02). These results shows the efficacy of such a programme of MRB containment in a large hospital, provided barrier nursing is instigated, together with the availability of such material as antiseptic soap, to allow implementation.

Screening for methicillin-resistant Staphylococcus aureus in the endemic hospital: what have we learned?

Control of methicillin-resistant Staphylococcus aureus (MRSA) still generates controversy among infection control practitioners. Opponents claim that once MRSA becomes endemic in an institution, control efforts are no longer justified. This review examines the usefulness, feasibility and cost-effectiveness of control programmes in acute-care hospitals where eradication of MRSA has either failed or has never been attempted; hence, the pathogen has become endemic. High endemicity is associated with increased hospital-acquired infection rates, increased use of glycopeptides and subsequent risk of emergence of antibiotic-resistant Gram-positive bacteria, and additional healthcare costs. Thus, MRSA control has many advantages. Indeed, in many institutions the actual benefit of containment efforts was manifested through the resultant decrease in the incidence of hospital-acquired MRSA infections. Successful programmes are based on an early identification of the MRSA reservoir and prompt implementation of contact precautions. The most efficacious strategy to detect occult MRSA carriage is via the screening of high-risk patients on admission to the hospital which has proven to be cost-effective in varied acute-care endemic settings.

The epidemiology of antibiotic resistance in hospitals: paradoxes and prescriptions

A simple mathematical model of bacterial transmission within a hospital was used to study the effects of measures to control nosocomial transmission of bacteria and reduce antimicrobial resistance in nosocomial pathogens. The model predicts that: (i) Use of an antibiotic for which resistance is not yet present in a hospital will be positively associated at the individual level (odds ratio) with carriage of bacteria resistant to other antibiotics, but negatively associated at the population level (prevalence). Thus inferences from individual risk factors can yield misleading conclusions about the effect of antibiotic use on resistance to another antibiotic. (ii) Nonspecific interventions that reduce transmission of all bacteria within a hospital will disproportionately reduce the prevalence of colonization with resistant bacteria. (iii) Changes in the prevalence of resistance after a successful intervention will occur on a time scale of weeks to months, considerably faster than in community-acquired infections. Moreover, resistance can decline rapidly in a hospital even if it does not carry a fitness cost. The predictions of the model are compared with those of other models and published data. The implications for resistance control and study design are discussed, along with the limitations and assumptions of the model.