Is Methicillin-Resistant Staphylococcus Aureus More Contagious than Methicillin-Susceptible S. Aureus in a Surgical Intensive Care Unit?

RNA-seq analysis reveals resistome genes and signalling pathway associated with vancomycin-intermediate Staphylococcus aureus

Context

Vancomycin-intermediate Staphylococcus aureus remains one of the most prevalent multidrug-resistant pathogens causing healthcare infections that are difficult to treat.

Aims

This study uses a comprehensive computational analysis to systematically investigate various gene expression profiles of resistant and sensitive S. aureus strains on exposure to antibiotics.

Settings and Design

The transcriptional changes leading to the development of multiple antibiotic resistance were examined by an integrative analysis of nine differential expression experiments under selected conditions of vancomycin-intermediate and -sensitive strains for four different antibiotics using publicly available RNA-Seq datasets.

Materials and Methods

For each antibiotic, three experimental conditions for expression analysis were selected to identify those genes that are particularly involved in the development of resistance. The results were further scrutinised to generate a resistome that can be analysed for their role in the development or adaptation to antibiotic resistance.

Results

The 99 genes in the resistome are then compiled to create a multiple drug resistome of 25 known and novel genes identified to play a part in antibiotic resistance. The inclusion of agr genes and associated virulence factors in the identified resistome supports the role of agr quorum sensing system in multiple drug resistance. In addition, enrichment analysis also identified the kyoto encyclopedia of genes and genomes (KEGG) pathways - quorum sensing and two-component system pathways - in the resistome gene set.

Conclusion

Further studies on understanding the role of the identified molecular targets such as SAA6008_00181, SAA6008_01127, agrA, agrC and coa in adapting to the pressure of antibiotics at sub-inhibitory concentrations can help in learning the molecular mechanisms causing resistance to the pathogens as well as finding other potential therapeutics.

Methicillin-resistant Staphylococcus aureus has greater risk of transmission in the operating room than methicillin-sensitive S aureus

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogenic S aureus strain characteristic associated with increased patient morbidity and mortality. The health care system needs to understand MRSA transmissibility in all settings to improve basic preventive measures to generate sustained reductions in invasive MRSA infections. Our primary aim was to compare intraoperative transmissibility of MRSA versus methicillin-sensitive S aureus (MSSA) isolates.

METHODS

S aureus isolates (N = 173) collected from 274 randomly selected operating room environments (first and second case of the day in each operating room, a case pair) at 3 hospitals underwent systematic-phenotypic and genomic processing to identify clonally related transmission events. Confirmed transmission events were defined as at least 2 S aureus isolates obtained from ≥2 distinct intraoperative reservoirs sampled within or between cases in a study unit that were epidemiologically and clonally related. We explored the relationship between clonal transmission and methicillin resistance with Poisson regression analysis.

RESULTS

We identified 58 clonal transmission events. MRSA isolates were associated with increased risk of clonal transmission compared with MSSA isolates (adjusted incidence risk ratio [IRR], 1.68; 95% confidence interval [CI], 1.13-2.49; P = .010; unadjusted IRR, 1.85; 95% CI, 1.23-2.77; P = .003, respectively).

CONCLUSIONS

MRSA isolates are associated with increased risk of intraoperative transmission. Future work should examine the impact of the attenuation of intraoperative MRSA transmission on the incidence of invasive MRSA infections.

Knowledge, Attitude, and Practices Regarding Contact Precautions Among Iranian Physicians

Objective.

To assess the knowledge, attitudes, and practices of Iranian physicians regarding contact isolation precautions.

Design.

Data were collected between May and November 2002 using a cross-sectional survey design.

Setting.

Teaching hospitals in Shiraz, Iran.

Participants.

A total of 155 physicians: 78 attending clinicians and 77 resident physician surgeons or internists.

Results.

The mean scores for knowledge and attitude were acceptable, with 71% of physicians scoring the maximum for knowledge and 65% achieving the maximum scores for attitude, whereas the mean score for practice was low, with only 26% achieving the maximum score. A good level of knowledge be associated with a good attitude (odds ratio [OR], 68.4 [95% confidence interval {CI}, 20.0-285.6]; P< .001), good practices were associated with good knowledge (OR, 22.5 [95% CI, 7.1-91.3]; P< .001), and a good attitude was associated with good practice (OR, 20.0 [95% CI, 5.7-105.2]; P<.001).

Conclusion.

Although strong associations were found among knowledge, attitude, and practice, the level of compliance with precautions was not nearly as high as it should be.

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.

Trends in Methicillin-ResistantStaphylococcus aureus(MRSA) Bloodstream Infections: Effect of the MRSA “Search and Isolate” Strategy in a Hospital in Italy with Hyperendemic MRSA

Objective:

To evaluate the secular trends in MRSA BSIs after the introduction of a nosocomial MRSA control intervention.

Design:

Before-after study.

Setting:

An 850-bed community hospital with an ICU and vascular surgery, neurosurgery, bone marrow transplantation, and AIDS units. MRSA is endemic at this hospital; the prevalence of methicillin resistance among patients withS. aureusinfection is greater than 50%.

Patients:

Among all inpatients, MRSA BSI was identified, its origin defined, and incidence rates calculated by ward and origin.

Intervention:

A MRSA control program was implemented based on active surveillance cultures to identify MRSA-colonized patients, followed by isolation using contact precautions. Incidence rates of MRSA BSI during the intervention (ie, July 1, 1997, to December 31, 2001) and preintervention (ie, January 1, 1996, to June 30, 1997) periods were compared.

Results:

Sixty-nine MRSA BSIs were identified. When compared with the preintervention period, the incidence rate of MRSA BSI was reduced from 0.64 to 0.30 per 1,000 admissions (RR, 0.46; CI95, 0.25–0.87;P= .02) during the intervention period. The impact was greater in the ICU, with an 89% reduction (RR, 0.11; CI95, 0.01–0.98;P= .03), and for CVC-associated MRSA BSIs, with an 82% decrease (RR, 0.17; CI95, 0.05–0.55;P= .002). Methicillin resistance amongS. aureusblood isolates decreased from 46% to 17% (RR, 0.36; CI95, 0.22–0.62;P= .0002).

Conclusion:

A reduction in MRSA bacteremia is achievable through use of the MRSA “search and isolate” intervention even in a hospital with high rates of endemic MRSA.

Political Versus Epidemiological Correctness

In the March issue of the journal, the Joint SHEA and APIC Task Force indicates that the Society for Healthcare Epidemiology of America (SHEA) and the Association for Professionals in Infection Control and Epidemiology (APIC) support the use of active detection and isolation (ADI) for controlling nosocomial infections due to methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) “in appropriate circumstances, as recommended in previously published guidelines”1(p250) (those published by SHEA and the Healthcare Infection Control Practices Advisory Committee [HICPAC]), but that SHEA and APIC oppose the use of legislation for mandating any infection control approach, including this one as tried in 2006 in Illinois and Maryland.

Both supporters and opponents of controlling MRSA and VRE with ADI probably will agree that legislation is not the optimal way to control nosocomial infections in general, but this position statement undoubtedly will please the latter more than it does the former because the SHEA/APIC Task Force argues that ADI is not ready for routine use throughout all healthcare facilities, directly opposing the position of the original SHEA guideline. As an author of that SHEA guideline, I would like to comment. First, the new position seems politically correct (since most infection control professionals have not yet bothered using ADI to control MRSA and VRE), but many of the planks of the SHEA/APIC Task Force position statement are misleading.

Colonization and transmission of meticillin-susceptible and meticillin-resistant Staphylococcus aureus in a murine nasal colonization model

Nasal colonization by Staphylococcus aureus is an important risk factor for the development of a nosocomial infection. Acquisition of nasal colonization by S. aureus increases mortality in hospitalized patients, but little is known about the transmission dynamics of S. aureus. To study S. aureus transmission, colonization and colonization persistence, we developed a murine transmission model. In 20 cages, 2 out of 10 mice were nasally inoculated (at 5×10(8) c.f.u. per mouse) with either meticillin-susceptible S. aureus (MSSA) (10 cages) or meticillin-resistant S. aureus (MRSA) (10 cages). On days 5, 15, 25 and 40, all mice in a cage were swabbed or sacrificed and nasal colonization and c.f.u. were determined in all 10 mice by nasal dissection or by nasal swab. Spread and subsequent stable colonization by both MSSA and MRSA from colonized to uncolonized mice within a cage was seen. At day 5, an increased number of colonized mice were observed in the MSSA group compared to the MRSA group (P = 0.003). On day 40, the mean number of c.f.u. per mouse was higher for MRSA than for MSSA (P = 0.06). Faecal-oral transmission was shown to be a possibly important transmission route in this model. These results suggest a more rapid spread of MSSA compared to MRSA. However, MRSA shows a more stable nasal colonization after a longer period of time.

Evaluation of the DiversiLab system for detection of hospital outbreaks of infections by different bacterial species

Many bacterial typing methods are specific for one species only, time-consuming, or poorly reproducible. DiversiLab (DL; bioMérieux) potentially overcomes these limitations. In this study, we evaluated the DL system for the identification of hospital outbreaks of a number bacterial species. Appropriately typed clinical isolates were tested with DL. DL typing agreed with pulsed-field gel electrophoresis (PFGE) for Acinetobacter (n = 26) and Stenotrophomonas maltophilia (n = 13) isolates. With two exceptions, DL typing of Klebsiella isolates (n = 23) also correlated with PFGE, and in addition, PFGE-nontypeable (PFGE-NT) isolates could be typed. Enterobacter (n = 28) results also correlated with PFGE results; also, PFGE-NT isolates could be clustered. In a larger study (n = 270), a cluster of 30 isolates was observed that could be subdivided by PFGE. The results for Escherichia coli (n = 38) correlated less well with an experimental multilocus variable number of tandem repeats analysis (MLVA) scheme. Pseudomonas aeruginosa (n = 52) showed only a limited number of amplification products for most isolates. When multiple Pseudomonas isolates were assigned to a single type in DL, all except one showed multiple multilocus sequence types. Methicillin-resistant Staphylococcus aureus generally also showed a limited number of amplification products. Isolates that belonged to different outbreaks by other typing methods, including PFGE, spa typing, and MLVA, were grouped together in a number of cases. For Enterococcus faecium, the limited variability of the amplification products obtained made interpretation difficult and correlation with MLVA and esp gene typing was poor. All of the results are reflected in Simpson's index of diversity and adjusted Rand's and Wallace's coefficients. DL is a useful tool to help identify hospital outbreaks of Acinetobacter spp., S. maltophilia, the Enterobacter cloacae complex, Klebsiella spp., and, to a somewhat lesser extent, E. coli. In our study, DL was inadequate for P. aeruginosa, E. faecium, and MRSA. However, it should be noted that for the identification of outbreaks, epidemiological data should be combined with typing results.

Methicillin-Resistant Staphylococcus Aureus in a Surgical Intensive Care Unit

The rate of methicillin-resistant Staphylococcus aureus (MRSA) infections has increased significantly over the last years, especially from community-associated MRSA (CA-MRSA) sources. The true prevalence of these multidrug-resistant infections among the trauma patient population, however, is not well defined. A retrospective review of our surgical intensive care unit (SICU) database from April 2003 to April 2007 was performed to identify all trauma patients surviving 48 hours or more that had a positive culture result during their SICU stay. The results of the cultures were examined. A total of 582 SICU patients with 2,860 cultures were assessed for MRSA infection. Among these, 368 cultures (12.9%) in 36 patients were reported as MRSA positive. Thirteen of these patients fulfilled the criteria for a CA-MRSA infection. When outcomes were analyzed, no significant difference in mortality (8.7% vs 15.4%, P = 0.540) or hospital related charges ($364,231 ± 323,719 vs $242,458 ± 276,630, P = 0.091) was noted. Patients with a hospital-acquired MRSA infection, however, had longer hospital lengths of stay (42.7 ± 47.1 vs 25.3 ± 31.1, P = 0.037) than their community-associated counterparts. MRSA constitutes an important source of infection among critically ill trauma patients. CA-MRSA organisms may play an increasing pathogenic role in this population.

Implementing the MRSA recommendations made by the Commission for Hospital Hygiene and Infection Prevention (KRINKO) of 1999 - current considerations by the DGKH Management Board

In Germany, recommendations on dealing with patients who are colonised with methicillin-resistant S. aureus (MRSA) for the inpatient sector have been published in 1999 by the Commission for Hospital Hygiene and Infection Prevention (KRINKO). Some challenges arise with regard to the practical implementation of the KRINKO recommendations. These challenges do not principally question the benefit of the recommendations but have come into criticism from users. In this commentary the German Society for Hospital Hygiene (DGKH) discusses some controversial issues and adds suggestions for unresolved problems regarding the infection control management of MRSA in healthcare settings.

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.

Dissemination of the CDC's Hand Hygiene Guideline and impact on infection rates

BACKGROUND

The diffusion of national evidence-based practice guidelines and their impact on patient outcomes often go unmeasured.

METHODS

Our objectives were to (1) evaluate implementation and compliance with clinical practices recommended in the new Centers for Disease Control and Prevention (CDC) Hand Hygiene Guideline, (2) compare rates of health care-associated infections (HAI) before and after implementation of the Guideline recommendations, and (3) examine the patterns and correlates of changes in rates of HAI. We used pre- and post-Guideline implementation site visits and surveys in the setting of 40 US hospitals--members of the National Nosocomial Infections Surveillance System--and measured HAI rates 1 year before and after publication of the CDC Guideline and used direct observation of hand hygiene compliance and Guideline implementation scores.

RESULTS

All study hospitals had changed their policies and procedures and provided products in compliance with Guideline recommendations; 89.8% of 1359 staff members surveyed anonymously reported that they were familiar with the Guideline. However, in 44.2% of the hospitals (19/40), there was no evidence of a multidisciplinary program to improve compliance. Hand hygiene rates remained low (mean, 56.6%). Rates of central line-associated bloodstream infections were significantly lower in hospitals with higher rates of hand hygiene (P < .001). No impact of Guideline implementation or hand hygiene compliance on other HAI rates was identified. Other factors occurring over time could affect rates of HAI. Observed hand hygiene compliance rates were likely to overestimate rates in actual practice. The study may have been of too short duration to detect the impact of a practice guideline.

CONCLUSION

Wide dissemination of this Guideline was not sufficient to change practice. Only some hospitals had initiated multidisciplinary programs; practice change is unlikely without such multidisciplinary efforts and explicit administrative support.

Is MRSA more virulent than MSSA?

Numerous clinical studies have indicated, based on mortality rates, that methicillin-resistant Staphylococcus aureus (MRSA) strains are more virulent than methicillin-susceptible S. aureus (MSSA) strains. In contrast, quantitative laboratory examinations of the presence and magnitude of pathogenic mechanisms and virulence factors in strains of MRSA and MSSA have generated conflicting data. The most important reason for these conflicting results is probably the heterogeneic nature of the resistant population. A comparison of selected and congenic MRSA and MSSA sub-populations of the same strain is required to resolve this issue.

[Positive screening for MRSA--clinical consequences?]

BACKGROUND

The worldwide rise of MRSA is equivalent to an increase of nasal colonization with MRSA. The objectives of this study were to investigate the rate of occult nasal MRSA colonization in trauma patients, to elucidate the role of MRSA carriers for endogenous infection (nose --> wound) and to check the efficiency of mupirocin therapy.

PATIENTS AND METHODS

A total of 643 consecutive trauma patients underwent MRSA screening (nasal swabs) on admission. At the same time all MRSA wound infections were registered and all isolates were analysed with PFGE (pulsed-field gel electrophoresis) to detect cross-infection between individuals.

RESULTS

In 13 patients (2.0%) we found MRSA in the nose and limited isolation as well as therapy with mupirocin were performed. No endogenous transmission of MRSA from the nose to the wound could be seen, and no cross-infection to other patients could be detected.

CONCLUSION

Our findings suggest that in our patients with nasal colonization the risk of intra- and interindividual transmission of MRSA is very small. Therefore, in trauma patients screening on admission does not seem to be absolutely necessary either for clinical or for epidemiological reasons.

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.

Evaluation of a Strategy of Screening Multiple Anatomical Sites for Methicillin-Resistant Staphylococcus aureus at Admission to a Teaching Hospital

We compared the sensitivity of screening with nasal culture alone with that of a multiple-site screening method for the identification of carriers of methicillin-resistant Staphylococcus aureus at hospital admission. If nasal cultures alone had been used during the 1-year study, 27.0% of carriers of methicillin-resistant S. aureus would have been missed, which corresponds to 560 theoretical isolation days. If rectal screening had not been used, 431 theoretical isolation days would have been missed, and, if axillary screening had not been used, 99 theoretical isolation days would have been missed.

What proportion of hospital patients colonized with methicillin-resistant Staphylococcus aureus are identified by clinical microbiological cultures?

BACKGROUND

Most hospitals in the United States do not perform active surveillance cultures and, thus, rely on clinical microbiological cultures (CMCs) to identify patients colonized with methicillin-resistant Staphylococcus aureus (MRSA). We sought to determine what proportion of patients who are colonized with MRSA at admission are identified by CMCs during hospitalization.

METHODS

From February 1998 through November 2002, patients found to be colonized with MRSA at admission by use of active surveillance cultures were identified. The proportion of colonized patients who had a CMC that was positive for MRSA, the number of CMCs performed and their type (ie, according to the anatomical site from which specimens were obtained for culture), and the number and type of CMCs that were positive for MRSA were calculated.

RESULTS

Four hundred thirty-seven patients were found to be colonized with MRSA at admission, and 98 of 1,238 CMCs (7.9%; 95% confidence interval, 6.5%-9.6%) performed for 66 of these patients (15%; 95% confidence interval, 11.9%-18.8%) were positive for MRSA. The number of nonisolated days that would have occurred by relying on CMCs to identify MRSA-colonized patients was 3,247 (mean, 7.4 days per patient). Among the anatomical sites from which specimens were obtained for CMC, wounds demonstrated the highest sensitivity (30.2%) for identifying MRSA-colonized patients.

CONCLUSIONS

CMCs failed to identify 85% of MRSA-colonized patients, because, in part, CMCs identified only a small proportion of colonized patients. Because many studies have shown a decrease in the transmission of MRSA from colonized patients for whom contact precautions, rather than standard precautions, are used, the findings of this study suggest that failure to identify colonized patients and to use contact precautions may be an important reason for the increasing rate of nosocomial MRSA infection in hospitals in the United States.

Escherichia coli modulates extraintestinal spread of Staphylococcus aureus

Staphylococcus aureus remains one of the most frequent causes of life-threatening systemic infection in surgical and trauma patients. It is understood that S. aureus colonization predisposes to complicating infection, but extraintestinal dissemination of S. aureus from the intestinal lumen to the draining mesenteric lymph nodes has not been systematically studied. After oral inoculation with high numbers of S. aureus, otherwise normal mice had low levels of cecal S. aureus (6.7 log10/g) and the incidence of extraintestinal dissemination was 30%. As expected, parenteral Escherichia coli lipopolysaccharide (LPS) was associated with increased numbers of cecal S. aureus, but the incidence of translocation remained unchanged. Purified LPS had no effect on S. aureus internalization by cultured HT-29 enterocytes and no effect on S. aureus transmigration through confluent enterocytes. To begin to clarify the effect of alterations in cecal bacteria on S. aureus translocation, mice were orally inoculated with E. coli and S. aureus. Compared with mice inoculated with S. aureus alone, these mice had increased numbers of cecal E. coli and S. aureus, and the incidence of S. aureus translocation nearly doubled from 46% to 88%. Experiments with HT-29 enterocytes indicated that viable E. coli had no effect on S. aureus internalization, but viable E. coli was at least 40 times more potent in inducing S. aureus transmigration across confluent enterocytes compared with a corresponding amount of purified LPS. Thus, S. aureus disseminated from the intestinal tract of normal mice by a mechanism that could involve paracellular migration across the intestinal epithelial barrier.

Prevention and control of antimicrobial-resistant infections in intensive care patients

OBJECTIVE

To review the literature summarizing important aspects of infection control in the critical care setting and to provide recommendations to reduce infections with resistant bacteria in the intensive care unit.

DATA SOURCE

Computer searches of MEDLINE, EMBASE, and the Cochrane Library.

DATA

The frequency of antibiotic-resistant, health care-associated infections has increased every year for the past 2 decades. Infections with antibiotic-resistant organisms have been linked to increases in morbidity, length of hospitalization, increased healthcare costs, and increased mortality. A comprehensive approach is necessary to prevent antimicrobial resistance in ICUs. This includes (1) preventing infections; (2) diagnosing and treating infections appropriately; (3) using antimicrobials wisely; and (4) preventing transmission.

CONCLUSIONS

The reservoirs for antibiotic-resistant organisms are colonized patients, and the vectors are often healthcare workers. This places an enormous responsibility on healthcare providers to protect their patients. Clinicians must recognize the importance of adhering to the recommendations in the Centers for Disease Control's Campaign to Prevent Antimicrobial Resistance in the healthcare setting.

Knowledge, attitudes, and practices of contact precautions among Iranian nurses

BACKGROUND

Knowledge, attitudes, and contact precaution practices were surveyed in nurses at Shiraz University of Medical Sciences.

METHODS

Two hundred seventy nurses, midwives, and auxiliary nurses completed a questionnaire consisting of 8 knowledge items with corresponding attitudes and practices items.

RESULTS

Compliance with precaution practices was low, 19.5%, and little more than half, 51.8%, held positive attitudes toward the guidelines, whereas 65.5% could correctly answered all precaution knowledge items. Nurses with correct knowledge were 11.3 times more likely (P < .0001) to hold positive attitudes toward the guidelines and 14.2 times more likely (P < .0001) to comply with all 8 precaution practices, and compliers were 6.3 times more likely (P < .0001) to hold positive attitudes than noncompliers.

CONCLUSION

Although correct knowledge was associated with compliance and positive attitudes, the proportion of nurses who held positive attitudes also had good knowledge, and compliance with practices was not abundant. Better training coverage may result in compliance with precaution practices becoming the norm.

Colonization with methicillin-resistant Staphylococcus aureus after liver transplantation

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of infection after orthotopic liver transplantation (OLT). Colonization with MRSA is associated with a higher risk of infection. Previous studies have shown a high prevalence of MRSA colonization among OLT candidates. However, the risk of colonization with MRSA after OLT is still unclear. The objective of this study was to estimate the incidence and the factors associated with colonization with MRSA after OLT. This was a prospective cohort study including patients submitted to OLT between the years 2000 and 2002. Surveillance cultures of nasal swab specimens were performed within the 1st 72 hours of hospital admission and, subsequently, on weeks 2, 6, 13, and 26. Patients whose baseline cultures revealed nasal carriage of MRSA were excluded. A total of 60 patients were included in the study. The median follow-up was 72 days. A total of 9 patients (15%) became colonized. In multiple logistic regression analyses, the use of a urinary catheter for > or =5 days (P = .006), postoperative bleeding at the surgical site (P = .009), and preoperative use of fluoroquinolones (P = .08) were associated with a higher risk of colonization. Patients without any of these risk factors did not become colonized. In conclusion, nasal carriage of MRSA is frequently acquired after OLT. Periodic postoperative screening for MRSA carriage should be an integral component in programs designed to reduce nosocomial MRSA transmission in these patients. Further studies are needed to set up and validate a predictive model that could allow targeting postoperative screening to high-risk OLT recipients.

Effect of duplicate isolates of methicillin-susceptible and methicillin-resistant Staphylococcus aureus on antibiogram data

Duplicate Staphylococcus aureus isolates were analyzed to determine the impact of multiple isolates from the same patient on annual antibiogram data. During a 6-year period (1996 to 2001), 3,227 patients with 4,844 S. aureus isolates were evaluated. A total of 39% of patients with methicillin-resistant S. aureus (MRSA) (n = 860) and 23% of patients with methicillin-susceptible S. aureus (MSSA) (n = 2,367) infections had duplicate isolates. Cumulative data show that 91% of the patients during this 6-year period with duplicate isolates (2 to 13 duplicates/year) did not switch between MSSA and MRSA but retained the original S. aureus strain whether it was MSSA or MRSA. Rates of MRSA were calculated for each year by using all isolates and then eliminating duplicates. The impact of duplicate MRSA and MSSA isolates was evaluated by using the ratio of isolates per patient such that ratios of >1.0 indicate >1 isolate per patient. The 6-year ratio for MRSA was 1.90 isolates/patient, and the ratio for MSSA was 1.35. A significant difference (P < 0.05) was noted in the MRSA rates in 4 of 6 years when duplicate isolates were removed. Common phenotypic antibiogram patterns were compared for all MRSA isolates during the 6-year period, and 64% were of a single antibiogram phenotype. Eighty-eight percent of patients with duplicate MRSA isolates had phenotypically identical multiple isolates. The rate of MRSA differs when duplicate isolates are removed from the antibiogram data.

Role of healthcare workers in outbreaks of methicillin-resistant Staphylococcus aureus: a 10-year evaluation from a Dutch university hospital

BACKGROUND AND OBJECTIVE

The benefit of screening healthcare workers (HCWs) at risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage and furloughing MRSA-positive HCWs to prevent spread to patients is controversial. We evaluated our MRSA program for HCWs between 1992 and 2002.

SETTING

A university medical center in The Netherlands, where methicillin resistance has been kept below 0.5% of all nosocomial S. aureus infections using active surveillance cultures and isolation of colonized patients.

DESIGN

HCWs caring for MRSA-positive patients or patients in foreign hospitals were screened for MRSA. MRSA-positive HCWs had additional cultures, temporary exclusion from patient-related work, assessment of risk factors for persisting carriage, decolonization therapy with mupirocin intranasally and chlorhexidine baths for skin and hair, and follow-up cultures.

RESULTS

Fifty-nine HCWs were colonized with MRSA. Seven of 840 screened employees contracted MRSA in foreign hospitals; 36 acquired MRSA after contact with MRSA-positive patients despite isolation precautions (attack rate per outbreak varied from less than 1% to 15%). Our hospital experienced 17 MRSA outbreaks, including 13 episodes in which HCWs were involved. HCWs were index cases of at least 4 outbreaks. In 8 outbreaks, HCWs acquired MRSA after caring for MRSA-positive patients despite isolation precautions.

CONCLUSION

Postexposure screening of HCWs allowed early detection of MRSA carriage and prevention of subsequent transmission to patients. Where the MRSA prevalence is higher, the role of HCWs may be greater. In such settings, an adapted version of our program could help prevent dissemination.

SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus

BACKGROUND

Infection control programs were created three decades ago to control antibiotic-resistant healthcare-associated infections, but there has been little evidence of control in most facilities. After long, steady increases of MRSA and VRE infections in NNIS System hospitals, the Society for Healthcare Epidemiology of America (SHEA) Board of Directors made reducing antibiotic-resistant infections a strategic SHEA goal in January 2000. After 2 more years without improvement, a SHEA task force was appointed to draft this evidence-based guideline on preventing nosocomial transmission of such pathogens, focusing on the two considered most out of control: MRSA and VRE.

METHODS

Medline searches were conducted spanning 1966 to 2002. Pertinent abstracts of unpublished studies providing sufficient data were included.

RESULTS

Frequent antibiotic therapy in healthcare settings provides a selective advantage for resistant flora, but patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with surveillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed.

CONCLUSION

Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC's long-recommended contact precautions.