Carriage of methicillin-resistant Staphylococcus aureus, ceftazidime-resistant Gram-negative bacilli, and vancomycin-resistant enterococci before and after intensive care unit admission

Gastrointestinal colonization of methicillin-resistant Staphylococcus aureus: an unrecognized burden in the hospital infection control

The incidence, risk factors, outcomes, and genomic relatedness of patients with newly diagnosed gastrointestinal colonization of meticillin-resistant Staphylococcus aureus (MRSA) were analyzed epidemiologically and genetically by whole genome sequencing (WGS) in a hospital network in Hong Kong. Between 1 October 2015 and 31 December 2018, 919 (2.7%) of 34,667 patients had newly diagnosed gastrointestinal MRSA colonization by admission screening. The incidence was 0.67±0.32 per 1,000-patient-days-per-quarter. Including patients with gastrointestinal MRSA colonization, the overall burden of MRSA increased by 59.2% (from 1.13±0.13 to 1.80±0.36 case per 1,000-patient-days-per-quarter), with an addition of MRSA 4,727 patient-days during the study period. Patients referred from residential care home for the elderly [odds ratio (95% confidential interval): 4.18 (3.50-4.99), p<0.001], with history of hospitalization in the past 6 months [1.90 (1.56-2.30), p<0.001], and consumption of fluoroquinolones [1.76 (1.34-2.30), p<0.001], cephalosporins [1.61 (1.11-2.31), p=0.011], and proton pump inhibitors [1.31 (1.10-1.56), p=0.002] in the preceding 6 months were found to be independent risk factors by multivariable analysis in the case-control analysis. The median survival of case was significantly shorter than control (860 vs 1507 days, p<0.001). 127 (13.8%) of 919 patients developed symptomatic MRSA infection in 112 days (median, range: 2-712 days). Of 19 patients with paired MRSA faecal and blood culture isolates subjected to WGS, clonality was found in 16 (84.2%) pairs of MRSA isolates. MRSA ST45 constituted 44.7% (17/38) of MRSA isolates. Gastrointestinal MRSA colonization may contribute to adverse clinical outcomes and pose an unrecognized burden to the hospital infection control.

Elimination of Staphylococcus aureus nasal carriage in intensive care patients lowers infection rates

This study surveys the clinical relevance of the nasal Staphylococcus aureus colonization status on intensive care unit (ICU)-acquired S. aureus infections and compares molecular characteristics of isolates from the nose and infectious sites. The 390 patients included comprised 278 non-carriers and 112 carriers. Among the carriers, 56 were decolonized with mupirocin. Decolonization was verified through a second (negative) culture. Spa typing and virulence gene profiling were performed for all isolates. Twenty six S. aureus infections were detected in the carriage group and 20 in the non-carriage group. Eighteen of these 26 (69.2%) infections were among carriers, and 8 of these 26 (30.8%) infections occurred among decolonized carriers (p = 0.02). Overall, 31/112 (27.7%) of the colonized patients and 25/46 (60.1%) of infection were due to methicillin-resistant S. aureus (MRSA). The highest frequency virulence genes were sea and hlg (both 100%) in nasal isolates and sea, hlg, fnb, and clf (100%) for infectious isolates. t030 was the most abundant spa type overall. S. aureus carriers were more likely to develop S. aureus infection compared with decolonized and non-carrying patients. The sources of ICU S. aureus infection appear to be exogenous mostly, and a predominant clone (spa type 030) plays an important role. We confirm that nasal mupirocin treatment prevents ICU infections even when there is an increased prevalence of nosocomial MRSA.

Streptomyces as a Prominent Resource of Future Anti-MRSA Drugs

Methicillin-resistant Staphylococcus aureus (MRSA) pose a significant health threat as they tend to cause severe infections in vulnerable populations and are difficult to treat due to a limited range of effective antibiotics and also their ability to form biofilm. These organisms were once limited to hospital acquired infections but are now widely present in the community and even in animals. Furthermore, these organisms are constantly evolving to develop resistance to more antibiotics. This results in a need for new clinically useful antibiotics and one potential source are the Streptomyces which have already been the source of several anti-MRSA drugs including vancomycin. There remain large numbers of Streptomyces potentially undiscovered in underexplored regions such as mangrove, deserts, marine, and freshwater environments as well as endophytes. Organisms from these regions also face significant challenges to survival which often result in the production of novel bioactive compounds, several of which have already shown promise in drug development. We review the various mechanisms of antibiotic resistance in MRSA and all the known compounds isolated from Streptomyces with anti-MRSA activity with a focus on those from underexplored regions. The isolation of the full array of compounds Streptomyces are potentially capable of producing in the laboratory has proven a challenge, we also review techniques that have been used to overcome this obstacle including genetic cluster analysis. Additionally, we review the in vivo work done thus far with promising compounds of Streptomyces origin as well as the animal models that could be used for this work.

Epidemiology and clinical relevance of Staphylococcus aureus intestinal carriage: a systematic review and meta-analysis

INTRODUCTION

Recent data highlight the importance of screening more than one site for improving the detection of S. aureus colonization. Intestinal carriage is frequently under-investigated and its clinical impact ought to be defined a better way. Areas covered: This review and meta-analysis provide an updated overview of prevalence, characteristics and clinical significance of S. aureus intestinal carriage in different populations, both for methicillin-susceptible and -resistant S. aureus strains. Expert commentary: Intestinal S. aureus carriage is documented with higher prevalence in children and in patients with S. aureus skin and soft tissue infections. This site of colonization was shown to be associated with a high risk of dissemination in the environment and with S. aureus infection. Intestinal carriage is frequently retrieved in nasal carriers, reflecting probably an association with a high bacterial load. Exclusive intestinal carriage present in one third of intestinal carriers can be associated with infection. Comparative genotyping analysis of different strains from nasal and extra-nasal sites of carriage, including the intestinal ones, in the same individuals, would allow a better comprehension of the pathophysiology of S. aureus endogenous infection. It could also permit to improve the prevention of these infections by decolonization of sites implicated in infection genesis.

Incidence, Clinical Outcome and Risk Factors of Intensive Care Unit Infections in the Lagos University Teaching Hospital (LUTH), Lagos, Nigeria

Background

Infections are common complications in critically ill patients with associated significant morbidity and mortality.

Aim

This study determined the prevalence, risk factors, clinical outcome and microbiological profile of hospital-acquired infections in the intensive care unit of a Nigerian tertiary hospital.

Materials and Methods

This was a prospective cohort study, patients were recruited and followed up between September 2011 and July 2012 until they were either discharged from the ICU or died. Antimicrobial susceptibility testing of isolates was done using CLSI guidelines.

Results

Seventy-one patients were recruited with a 45% healthcare associated infection rate representing an incidence rate of 79/1000 patient-days in the intensive care unit. Bloodstream infections (BSI) 49.0% (22/71) and urinary tract infections (UTI) 35.6% (16/71) were the most common infections with incidence rates of 162.9/1000 patient-days and 161.6/1000 patient-days respectively. Staphylococcus aureus was the most common cause of BSIs, responsible for 18.2% of cases, while Candida spp. was the commonest cause of urinary tract infections, contributing 25.0% of cases. Eighty percent (8/10) of the Staphylococcus isolates were methicillin-resistant. Gram-negative multidrug bacteria accounted for 57.1% of organisms isolated though they were not ESBL-producing. Use of antibiotics (OR = 2.98; p = 0.03) and surgery (OR = 3.15, p< 0.05) in the month preceding ICU admission as well as urethral catheterization (OR = 5.38; p<0.05) and endotracheal intubation (OR = 5.78; p< 0.05) were risk factors for infection.

Conclusion

Our findings demonstrate that healthcare associated infections is a significant risk factor for ICU-mortality and morbidity even after adjusting for APACHE II score.

The Effect of Contact Precautions on Frequency of Hospital Adverse Events

OBJECTIVE

To determine whether use of contact precautions on hospital ward patients is associated with patient adverse events

DESIGN

Individually matched prospective cohort study

SETTING

The University of Maryland Medical Center, a tertiary care hospital in Baltimore, Maryland

METHODS

A total of 296 medical or surgical inpatients admitted to non-intensive care unit hospital wards were enrolled at admission from January to November 2010. Patients on contact precautions were individually matched by hospital unit after an initial 3-day length of stay to patients not on contact precautions. Adverse events were detected by physician chart review and categorized as noninfectious, preventable and severe noninfectious, and infectious adverse events during the patient's stay using the standardized Institute for Healthcare Improvement's Global Trigger Tool.

RESULTS

The cohort of 148 patients on contact precautions at admission was matched with a cohort of 148 patients not on contact precautions. Of the total 296 subjects, 104 (35.1%) experienced at least 1 adverse event during their hospital stay. Contact precautions were associated with fewer noninfectious adverse events (rate ratio [RtR], 0.70; 95% confidence interval [CI], 0.51-0.95; P=.02) and although not statistically significant, with fewer severe adverse events (RtR, 0.69; 95% CI, 0.46-1.03; P=.07). Preventable adverse events did not significantly differ between patients on contact precautions and patients not on contact precautions (RtR, 0.85; 95% CI, 0.59-1.24; P=.41).

CONCLUSIONS

Hospital ward patients on contact precautions were less likely to experience noninfectious adverse events during their hospital stay than patients not on contact precautions.

Rapid, highly discriminatory binary genotyping to demonstrate methicillin-resistant Staphylococcus aureus transmission in a tertiary care intensive care unit

OBJECTIVES

No previous studies of methicillin-resistant Staphylococcus aureus (MRSA) epidemiology in adult intensive care units (ICUs) have assessed the utility of rapid, highly discriminatory strain typing in the investigation of transmission events.

DESIGN

Observational.

SETTING

A 22-bed medical-surgical adult ICU. Patients Those admissions MRSA-positive on initial screening and all admissions <48 hours in duration were excluded, leaving a cohort of 653 patients (median age, 61 years; APACHE-II, 19).

METHODS

We conducted this study of MRSA transmission over 1 year (August 1, 2011 to July 31, 2012) using a multiplex PCR-based reverse line blot (mPCR/RLB) assay to genotype isolates from surveillance swabs obtained at admission and twice weekly during ICU stays. MRSA prevalence and incidence rates were calculated and transmission events were identified using strain matching. Colonization pressure was calculated daily by summation of all MRSA cases.

RESULTS

Of 1,030 admissions to ICU during the study period, 349 patients were excluded. MRSA acquisition occurred during 31 of 681 (4.6%) remaining admissions; 19 of 31(61%) acquisitions were genotype-confirmed, including 7 (37%) due to the most commonly transmitted strain. Moving averages of MRSA patient numbers on the days prior to a documented event were used in a Poisson regression model. A significant association was found between transmission and colonization pressure when the average absolute colonization pressure on the previous day was ≥3 (χ2=7.41, P=0.01).

CONCLUSIONS

mPCR/RLB characterizes MRSA isolates within a clinically useful time frame for identification of single-source clusters within the ICU. High MRSA colonization pressure (≥3 MRSA-positive patients) on a given day is associated with an increased likelihood of a transmission event.

The Effect of Universal Glove and Gown Use on Adverse Events in Intensive Care Unit Patients

BACKGROUND

No randomized trials have examined the effect of contact precautions or universal glove and gown use on adverse events. We assessed if wearing gloves and gowns during all patient contact in the intensive care unit (ICU) changes adverse event rates.

METHODS

From January 2012 to October 2012, intervention ICUs of the 20-site Benefits of Universal Gloving and Gowning cluster randomized trial required that healthcare workers use gloves and gowns for all patient contact. We randomly sampled 1800 medical records of adult patients not colonized with antibiotic-resistant bacteria and reviewed them for adverse events using the Institute for Healthcare Improvement Global Trigger Tool.

RESULTS

Four hundred forty-seven patients (24.8%) had 1 or more ICU adverse events. Adverse events were not associated with universal glove and gown use (incidence rate ratio [IRR], 0.81; 95% confidence interval [CI], .48-1.36). This did not change with adjustment for ICU type, severity of illness, academic hospital status, and ICU size, (IRR, 0.91; 95% CI, .59-1.42; P = .68). Rates of infectious adverse events also did not differ after adjusting for the same factors (IRR, 0.75; 95% CI, .47-1.21; P = .24).

CONCLUSIONS

In ICUs where healthcare workers donned gloves and gowns for all patient contact, patients were no more likely to experience adverse events than in control ICUs. Concerns of adverse events resulting from universal glove and gown use were not supported. Similar considerations may be appropriate regarding use of contact precautions.

CLINICAL TRIALS REGISTRATION

NCT0131821.

Influence of First-Line Antibiotics on the Antibacterial Activities of Acetone Stem Bark Extract of Acacia mearnsii De Wild. against Drug-Resistant Bacterial Isolates

Background. This study was aimed at evaluating the antibacterial activity of the acetone extract of A. mearnsii and its interactions with antibiotics against some resistant bacterial strains. Methods. The antibacterial susceptibility testing was determined by agar diffusion and macrobroth dilution methods while the checkerboard method was used for the determination of synergy between the antibiotics and the extract. Results. The results showed that the susceptibility of the different bacterial isolates was concentration dependent for the extract and the different antibiotics. With the exception of S. marcescens, the inhibition zones of the extract produced by 20 mg/mL ranged between 18 and 32 mm. While metronidazole did not inhibit any of the bacterial isolates, all the antibiotics and their combinations, except for ciprofloxacin and its combination, did not inhibit Enterococcus faecalis. The antibacterial combinations were more of being antagonistic than of being synergistic in the agar diffusion assay. From the macrobroth dilution, the extract and the antibiotics exerted a varied degree of inhibitory effect on the test organisms. The MIC values of the acetone extract which are in mg/mL are lower than those of the different antibiotics which are in μg/mL. From the checkerboard assay, the antibacterial combinations showed varied degrees of interactions including synergism, additive, indifference, and antagonism interactions. While antagonistic and additive interactions were 14.44%, indifference interaction was 22.22% and synergistic interaction was 37.78% of the antibacterial combinations against the test isolates. While the additivity/indifference interactions indicated no interactions, the antagonistic interaction may be considered as a negative interaction that could result in toxicity and suboptimal bioactivity. Conclusion. The synergistic effects of the herbal-drug combinations may be harnessed for the discovery and development of more rational evidence-based drug combinations with optimized efficiency in the prevention of multidrug resistance and therapy of multifactorial diseases.

Does colonization with methicillin-susceptible Staphylococcus aureus protect against nosocomial acquisition of methicillin-resistant S. aureus?

OBJECTIVE

To test the hypothesis that methicillin-susceptible Staphylococcus aureus (MSSA) carriage may protect against nosocomial methicillin-resistant S. aureus (MRSA) acquisition by competing for colonization of the anterior nares.

DESIGN

Prospective cohort and nested case-control study.

SETTING

Swiss university hospital.

PATIENTS

All adult patients admitted to 14 wards of the general medicine division between April 1 and October 31, 2007.

METHODS

Patients were screened for MRSA and MSSA carriage at admission to and discharge from the division. Associations between nosocomial MRSA acquisition and MSSA colonization at admission and other confounders were analyzed by univariable and multivariable analysis.

RESULTS

Of 898 patients included, 183 (20%) were treated with antibiotics. Nosocomial MRSA acquisition occurred in 70 (8%) of the patients (case patients); 828 (92%) of the patients (control subjects) were free of MRSA colonization at discharge. MSSA carriage at admission was 20% and 21% for case patients and control subjects, respectively. After adjustment by multivariate logistic regression, no association was observed between MSSA colonization at admission and nosocomial MRSA acquisition (adjusted odds ratio [aOR], 1.2 [95% confidence interval (CI), 0.6-2.3]). By contrast, 4 independent predictors of nosocomial MRSA acquisition were identified: older age (aOR per 1-year increment, 1.05 [95% CI, 1.02-1.08]); increased length of stay (aOR per 1-day increment, 1.05 [95% CI, 1.02-1.09]); increased nursing workload index (aOR per 1-point increment, 1.02 [95% CI, 1.01-1.04]); and previous treatment with macrolides (aOR, 5.6 [95% CI, 1.8-17.7]).

CONCLUSIONS

Endogenous MSSA colonization does not appear to protect against nosocomial MRSA acquisition in a population of medical patients without frequent antibiotic exposure.

Admission Screening of Methicillin-Resistant Staphylococcus aureus with Rapid Molecular Detection in Intensive Care Unit: A Three-Year Single-Centre Experience in Hong Kong

Background. The admission screening of methicillin-resistant Staphylococcus aureus (MRSA) by rapid molecular assay is considered to be an effective method in reducing the transmission of MRSA in intensive care unit (ICU). Method. The admission screening on patients from ICU once on their admissions by BD GeneOhm MRSA assay has been introduced to Prince of Wales Hospital, Hong Kong, since 2008. The assay was performed on weekdays and reported on the day of testing. Patients pending for results were under standard precautions until the negative screening results were notified, while contact precautions were implemented for MRSA-positive patients. In this study, we compared the MRSA transmission rate in molecular screening periods (2008 to 2010) with the historical culture periods (2006 to 2007) as control. Results. A total of 4679 samples were tested; the average carriage rate of MRSA on admission was 4.45%. By comparing with the historical culture periods, the mean incidence ICU-acquired MRSA infection was reduced from 3.67 to 1.73 per 1000 patient bed days. Conclusion. The implementation of admission screening of MRSA with molecular method in intensive care unit could reduce the MRSA transmission, especially in the area with high MRSA prevalence situation in Hong Kong.

Trends and significance of VRE colonization in the ICU: a meta-analysis of published studies

Background

The burden and significance of vancomycin-resistant enterococci (VRE) colonization in the ICU is not clearly understood.

Methods

We searched PubMed and EMBASE up to May 2013 for studies reporting the prevalence of VRE upon admission to the ICU and performed a meta-analysis to assess rates and trends of VRE colonization. We calculated the prevalence of VRE on admission and the acquisition (colonization and/or infection) rates to estimate time trends and the impact of colonization on ensuing VRE infections.

Findings

Across 37 studies (62,959 patients at risk), the estimated prevalence of VRE on admission to the ICU was 8.8% (7.1-10.6). Estimates were more consistent when cultures were obtained within 24 hours from admission. The VRE acquisition rate was 8.8% (95% CI 6.9-11.0) across 26 evaluable studies (35,364 patients at risk). Across US studies, VRE acquisition rate was 10.2% (95% CI 7.7-13.0) and demonstrated significant decline in annual trends. We used the US estimate of colonization on admission [12.3% (10.5-14.3)] to evaluate the impact of VRE colonization on admission in overall VRE prevalence. We demonstrated that VRE colonization on admission is a major determinant of the overall VRE burden in the ICU. Importantly, among colonized patients (including admitted and/or acquired cases) the VRE infection rates vary widely from 0-45% (with the risk of VRE bacteremia being reported from 0-16%) and <2% among those without a proven colonization.

Conclusion

In summary, up to 10.6% of patients admitted in the ICU are colonized with VRE on admission and a similar percentage will acquire VRE during their ICU stay. Importantly, colonization on admission is a major determinant of VRE dynamics in the ICU and the risk of VRE-related infections is close related to colonization.

A systematic literature review and meta-analysis of factors associated with methicillin-resistant Staphylococcus aureus colonization at time of hospital or intensive care unit admission

OBJECTIVE

Screening for methicillin-resistant Staphylococcus aureus (MRSA) in high-risk patients is a legislative mandate in 9 US states and has been adopted by many hospitals. Definitions of high risk differ among hospitals and state laws. A systematic evaluation of factors associated with colonization is lacking. We performed a systematic review of the literature to assess factors associated with MRSA colonization at hospital admission.

DESIGN

We searched MEDLINE from 1966 to 2012 for articles comparing MRSA colonized and noncolonized patients on hospital or intensive care unit (ICU) admission. Data were extracted using a standardized instrument. Meta-analyses were performed to identify factors associated with MRSA colonization.

RESULTS

We reviewed 4,381 abstracts; 29 articles met inclusion criteria (n = 76,913 patients). MRSA colonization at hospital admission was associated with recent prior hospitalization (odds ratio [OR], 2.4 [95% confidence interval (CI), 1.3-4.7]; P < .01), nursing home exposure (OR, 3.8 [95% CI, 2.3-6.3]; P < .01), and history of exposure to healthcare-associated pathogens (MRSA carriage: OR, 8.0 [95% CI, 4.2-15.1]; Clostridium difficile infection: OR, 3.4 [95% CI, 2.2-5.3]; vancomycin-resistant Enterococci carriage: OR, 3.1 [95% CI, 2.5-4.0]; P < .01 for all). Select comorbidities were associated with MRSA colonization (congestive heart failure, diabetes, pulmonary disease, immunosuppression, and renal failure; P < .01 for all), while others were not (human immunodeficiency virus, cirrhosis, and malignancy). ICU admission was not associated with an increased risk of MRSA colonization (OR, 1.1 [95% CI, 0.6-1.8]; P = .87).

CONCLUSIONS

MRSA colonization on hospital admission was associated with healthcare contact, previous healthcare-associated pathogens, and select comorbid conditions. ICU admission was not associated with MRSA colonization, although this is commonly used in state mandates for MRSA screening. Infection prevention programs utilizing targeted MRSA screening may consider our results to define patients likely to have MRSA colonization.

Patient-level factors associated with methicillin-resistant Staphylococcus aureus carriage at hospital admission: a systematic review

BACKGROUND

Selective methicillin-resistant Staphylococcus aureus (MRSA) screening programs target high-risk populations. To characterize high-risk populations, we conducted this systematic review to identify patient-level factors associated with MRSA carriage at hospital admission.

METHODS

Studies were identified in the MEDLINE (1950-2011) and EMBASE (1980-2011) databases. English studies were included if they examined adult populations and used multivariable analyses to examine patient-level factors associated with MRSA carriage at hospital admission. From each study, we abstracted details of the population, the risk factors examined, and the association between the risk factors and MRSA carriage at hospital admission.

RESULTS

Our electronic search identified 972 citations, from which we selected 27 studies meeting our inclusion criteria. The patient populations varied across the studies. Ten studies included all patients admitted to hospital, and the others were limited to specific hospital areas. MRSA detection methods also varied across studies. Ten studies obtained specimens from the nares only, whereas other studies also swabbed wounds, catheter sites, and the perianal region. Methods of MRSA diagnoses included polymerase chain reaction tests, cultures in various agar mediums, and latex agglutination tests. Patient age, gender, previous admission to hospital, and previous antibiotic use were the risk factors most commonly examined. The risk factor definition and study methods varied among studies to an extent that precluded meta-analysis.

CONCLUSION

The existing literature cannot be used to identify risk factors for MRSA colonization at the time of hospitalization. Future studies should be aware of the differences in the existing literature and aim to develop standardized risk factor definitions.

Quantifying the impact of extranasal testing of body sites for methicillin-resistant Staphylococcus aureus colonization at the time of hospital or intensive care unit admission

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of healthcare-associated infections. Recent legislative mandates require nares screening for MRSA at hospital and intensive care unit (ICU) admission in many states. However, MRSA colonization at extranasal sites is increasingly recognized. We conducted a systematic review of the literature to identify the yield of extranasal testing for MRSA.

DESIGN

We searched MEDLINE from January 1966 through January 2012 for articles comparing nasal and extranasal screening for MRSA colonization. Studies were categorized by population tested, specifically those admitted to ICUs and those admitted to hospitals with a high prevalence (6% or greater) or low prevalence (less than 6%) of MRSA carriers. Data were extracted using a standardized instrument.

RESULTS

We reviewed 4,381 abstracts and 735 articles. Twenty-three articles met the criteria for analysis ((n = 39,479 patients). Extranasal MRSA screening increased the yield by approximately one-third over nares alone. The yield was similar at ICU admission (weighted average, 33%; range, 9%-69%) and hospital admission in high-prevalence (weighted average, 37%; range, 9%-86%) and low-prevalence (weighted average, 50%; range, 0%-150%) populations. For comparisons between individual extranasal sites, testing the oropharynx increased MRSA detection by 21% over nares alone; rectum, by 20%; wounds, by 17%; and axilla, by 7%.

CONCLUSIONS

Extranasal MRSA screening at hospital or ICU admission in adults will increase MRSA detection by one-third compared with nares screening alone. Findings were consistent among subpopulations examined. Extranasal testing may be a valuable strategy for outbreak control or in settings of persistent disease, particularly when combined with decolonization or enhanced infection prevention protocols.

New acquisition of antibiotic-resistant organisms in skilled nursing facilities

The epidemiology of new acquisition of antibiotic-resistant organisms (AROs) in community-based skilled nursing facilities (SNFs) is not well studied. To define the incidence, persistence of, and time to new colonization with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and ceftazidime-resistant (CAZ(r)) and ciprofloxacin-resistant (CIP(r)) Gram-negative bacteria (GNB) in SNFs, SNF residents were enrolled and specimens from the nares, oropharynx, groin, perianal area, and wounds were prospectively cultured monthly. Standard microbiological tests were used to identify MRSA, VRE, and CAZ(r) and CIP(r) GNB. Residents with at least 3 months of follow-up were included in the analysis. Colonized residents were categorized as having either preexisting or new acquisition. The time to colonization for new acquisition of AROs was calculated. Eighty-two residents met the eligibility criteria. New acquisition of AROs was common. For example, of the 59 residents colonized with CIP(r) GNB, 28 (47%) were colonized with CIP(r) GNB at the start of the study (96% persistent and 4% intermittent), and 31 (53%) acquired CIP(r) GNB at the facility (61% persistent). The time to new acquisition was shortest for CIP(r) GNB, at a mean of 75.5 days; the time to new acquisition for MRSA was 126.6 days (P = 0.007 versus CIP(r) GNB), that for CAZ(r) was 176.0 days (P = 0.0001 versus CIP(r) GNB), and that for VRE was 186.0 days (P = 0.0004 versus CIP(r) GNB). Functional status was significantly associated with new acquisition of AROs (odds ratio [OR], 1.24; P = 0.01). New acquisition of AROs, in particular CIP(r) GNB and MRSA, is common in SNFs. CIP(r) GNB are acquired rapidly. Additional longitudinal studies to investigate risk factors for ARO acquisition are required.

Relationship between antibiotic consumption, oropharyngeal colonization, and ventilator-associated pneumonia by Staphylococcus aureus in an intensive care unit of a Brazilian teaching hospital

INTRODUCTION: his study evaluated the consumption of major classes of antibiotics, the colonization of the oropharynx of patients on mechanical ventilation, and the risk of ventilator-associated pneumonia (VAP) caused by Staphylococcus aureus in an intensive care unit for adults. METHODS: A case-control study was carried out using colonized patients (cases) by oxacillin-resistant S. aureus (ORSA) and (controls) oxacillin-sensitive S. aureus (OSSA) from May 2009 to August 2010. The occurrence of VAP by S. aureus was also evaluated in the same period. Antibiotic consumption was expressed as the number of defined daily doses (DDD)/1,000 patient-days for glycopeptides, carbapenems, and extended-spectrum cephalosporins. RESULTS: Three hundred forty-six (56.1%) patients underwent mechanical ventilation with a frequency of oropharyngeal colonization of 36.4%, corresponding to 63.5% for ORSA and 36.5% for OSSA. The risk of illness for this organism was significant (p<0.05), regardless of whether colonization/infection was by ORSA or OSSA. The consumption of antibiotics was high, mainly for broad-spectrum cephalosporins (551.26 DDDs/1,000 patient-days). The high density of use of glycopeptides (269.56 DDDs/1,000 patient-days) was related to colonization by ORSA (Pearson r=0.57/p=0.02). Additionally, age >60 years, previous antibiotic therapy, and previous use of carbapenems were statistically significant by multivariate analysis. CONCLUSIONS: There was a significant relationship between the colonization of the oropharyngeal mucosa and the risk of VAP by both phenotypes. The use of glycopeptides was related to colonization by ORSA.

Risk factors for positive admission surveillance cultures for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci in a neurocritical care unit

OBJECTIVE

Hospitals are under increasing pressure to perform active surveillance cultures for methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. This study aimed to identify patients at low and high risk for positive admission surveillance cultures for methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus in a neurocritical care unit using readily ascertainable historical factors.

DESIGN

Before/after study with nested case/control study.

SETTING

Neurocritical care unit of an academic hospital.

PATIENTS

During the intervention period (July 2007 to June 2008), after implementation of an admission surveillance culture screening program for methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, 2,059 patients were admitted to the neurocritical care unit for a total of 5,957 patient days.

INTERVENTIONS

Cases had positive methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus admission surveillance cultures within 48 hrs of hospital admission. Controls had negative cultures.

MEASUREMENTS AND MAIN RESULTS

Admission surveillance cultures grew methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus in 35 of 823 (4.3%) and 19 of 766 (2.5%) patients, respectively. Factors significantly associated with both methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus colonization were intravenous antibiotics and hospitalization in the past year, immunocompromised health status, intravenous drug use, long-term hemodialysis, and known prior carrier status. Transfer from an outside hospital and residence in a long-term care facility in the past year were associated with vancomycin-resistant Enterococcus colonization. Classification and regression tree analysis was used to identify variables that best predicted positive methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus surveillance cultures. A classification and regression tree model with six of these variables yielded an overall cross-validated predictive accuracy of 87.12% to detect methicillin-resistant Staphylococcus aureus colonization. For vancomycin-resistant Enterococcus, a four-variable classification and regression tree model (intravenous antibiotics, hospitalization and long-term patient care in the past year, and not being "admitted same day of procedure") optimized the predictive accuracy (94.91%). There were no cases of vancomycin-resistant Enterococcus colonization in patients admitted same day of procedure.

CONCLUSIONS

Colonization with methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus in neurocritical care patients can be predicted with a high predictive accuracy using decision trees that include four to six readily attainable risk factors. In our setting, in the absence of these risk factors and in patients admitted from home for neurosurgical procedures, routine admission surveillance cultures to the intensive care unit may not be cost-effective.

Optimal Dose of Vancomycin for Treating Methicillin-Resistant Staphylococcus Aureus Pneumonia in Critically Ill Patients

A prospective cohort study was performed to determine the optimal dose of vancomycin to maintain a serum trough concentration of at least 15 to 20 mg/l and to assess the efficacy of this target vancomycin concentration in the treatment of methicillin-resistant Staphylococcus aureus pneumonia. Vancomycin pharmacokinetic parameters were estimated using a CAPSIL software program from serum concentrations of 141 patients with pneumonia treated with vancomycin, regardless of methicillin-resistant Staphylococcus aureus status, at a 28-bed medical intensive care unit. Vancomycin trough concentrations and other pharmacokinetic parameters were compared between five groups of patients differing in their renal function: 1) creatinine clearance >60 ml/minute, 2) creatinine clearance 30 to 60 ml/minute, 3) creatinine clearance <30 ml/minute, 4) on intermittent haemodialysis, and 5) on continuous renal replacement therapy. More than 70% of patients failed to reach the recommended therapeutic serum trough concentrations: a higher dose of vancomycin is necessary to maintain serum trough concentration at 15 to 20 mg/l, particularly in critically ill patients with creatinine clearance above 60 ml/minute and in those on intermittent haemodialysis. Among patients with methicillin-resistant Staphylococcus aureus pneumonia, no significant differences were observed in the treatment success rate, length of intensive care unit stay, and intensive care unit mortality rate between patients with vancomycin trough concentrations of >20 mg/l, 15 to 20 mg/l and <15 mg/l.

Systematic review of measurement and adjustment for colonization pressure in studies of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and clostridium difficile acquisition

OBJECTIVE

Colonization pressure is an important infection control metric. The aim of this study was to describe the definition and measurement of and adjustment for colonization pressure in nosocomial-acquisition risk factor studies of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile.

METHODS

We performed a computerized search of studies of nosocomial MRSA, VRE, and C. difficile acquisition published before July 1, 2009, through MEDLINE. Studies were included if a study outcome was MRSA, VRE, or C. difficile acquisition; the authors identified risk factors associated with MRSA, VRE, or C. difficile acquisition; and the study measured colonization pressure.

RESULTS

The initial MEDLINE search yielded 505 articles. Sixty-six of these were identified as studies of nosocomial MRSA, VRE, or C. difficile acquisition; of these, 18 (27%) measured colonization pressure and were included in the final review. The definition of colonization pressure varied considerably between studies: the proportion of MRSA- or VRE-positive patients (5 studies), the proportion of MRSA- or VRE-positive patient-days (6 studies), or the total or mean number of MRSA-, VRE-, or C. difficile-positive patients or patient-days (7 studies) in the unit over periods of varying length. In 10 of 13 studies, colonization pressure was independently associated with MRSA, VRE, or C. difficile acquisition.

CONCLUSION

There is a need for a simple and consistent method to quantify colonization pressure in both research and routine clinical care to accurately assess the effect of colonization pressure on cross-transmission of antibiotic-resistant bacteria.

Co-colonization with multiple different species of multidrug-resistant gram-negative bacteria

BACKGROUND

The characteristics of co-colonization with multiple different species of multidrug-resistant gram-negative bacteria (MDRGN) have not been fully elucidated. Quantifying the prevalence of co-colonization and those patients at higher risk of co-colonization may have important implications for strategies aimed at limiting the spread of MDRGN.

METHODS

To determine the prevalence of MDRGN colonization, rectal swabs were obtained from 212 residents residing in a 600-bed long-term care facility. Co-colonization was defined as colonization with ≥2 different MDRGN species. Co-colonized residents were compared with residents colonized with a single MDRGN species to identify factors associated with an increased risk for co-colonization. Molecular typing was performed to determine the contribution of cross transmission to the co-colonized state.

RESULTS

A total of 53 (25%) residents was colonized with ≥1 MDRGN. Among these, 11 (21%) were colonized with ≥2 different species of MDRGN. A global deterioration score of ≥5 representing advanced dementia and an increased requirement for assistance from health care workers was significantly associated with co-colonization (P = .05). Clonally related MDRGN strains were identified among 7 (64%) co-colonized residents.

CONCLUSION

The prevalence of co-colonization with ≥2 different MDRGN is substantial. Cross transmission of MDRGN is a major contributor to the co-colonized state.

Increase of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE

To determine the incidence of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in four German tertiary care hospitals.

METHODS

This study was conducted at four tertiary care hospitals (all with >1,000 beds) in different geographic regions in Germany (Berlin in the east, Luebeck in the north, Freiburg in the southwest and Nuernberg in the southeast). Routine surveillance data on MRSA, vancomycin-resistant enterococci (VRE) and ESBL-producing bacteria were analysed from 2007 to 2009. Co-colonisation or co-infection was defined as a patient having positive cultures for at least two of the following resistant pathogens: MRSA, VRE faecium or different species of ESBL-producing Enterobacteriaceae within one calendar year.

RESULTS

A total of 896,822 patients were analysed, of which 10,066 patients harboured MRSA, VRE faecium and/or ESBL-producing Enterobacteriaceae, and 542 patients co-harboured at least two of those resistant pathogens. In 2009, 7.6% of the MRSA patients, 13.7% of the VRE faecium patients and even 16.1% of the ESBL-producing Enterobacteriaceae patients were co-colonised or co-infected. The incidence of patients with co-infection or co-colonisation increased steadily from 5 (2007) to 7 per 10,000 patients (2009).

CONCLUSIONS

Patients harbouring ESBL-producing Enterobacteriaceae or VRE faecium had a higher risk of being co-colonised or co-infected compared to what was to be extrapolated from their overall incidence. This might be linked to their gastrointestinal reservoir and impracticality to decolonise the gut of resistant VRE and ESBL-producing Enterobacteriaceae.

Clinical course and outcomes of single-organism Enterococcus peritonitis in peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Enterococci are part of the normal flora of the gastrointestinal tract. They can cause enteric peritonitis, which is a serious complication of peritoneal dialysis (PD). However, the clinical course and outcome of PD-related Enterococcus peritonitis remains unclear.

METHODS

We reviewed all Enterococcus peritonitis episodes occurring in our dialysis unit from 1995 to 2009.

RESULTS

During the study period, 1421 episodes of peritonitis were recorded. Of 29 episodes (2.0%) that were attributable to single-organism Enterococcus, 12 episodes were caused by E. faecalis; 9, by E. faecium; and the remaining 8, by other Enterococcus species. The overall rate of ampicillin resistance was 41.4%. Recent use of antibiotics was associated with the development of ampicillin-resistant Enterococcus (ARE) peritonitis (hazard ratio: 12.53; p = 0.04). The primary response rate of Enterococcus peritonitis was significantly higher than that of Escherichia coli peritonitis (89.7% vs. 69.9%, p = 0.038), but the primary response rate was not significantly lower for ARE peritonitis than for ampicillin-susceptible Enterococcus (ASE) peritonitis (83.3% vs. 94.1%, p = 0.553). However, significantly more patients with ARE had received vancomycin (83.3% vs. 23.5%, p = 0.003), with a longer mean duration of vancomycin treatment (11.8 ± 6.9 days vs. 3.7 ± 6.8 days, p = 0.005).

CONCLUSIONS

Recent use of antibiotics was a risk factor for the development of ARE peritonitis. Outcomes in ASE and ARE peritonitis were similar, but vancomycin was required during treatment for ARE peritonitis, in turn possibly predisposing the patients to infections caused by vancomycin-resistant organisms.

Successful control of vancomycin-resistant Enterococcus faecium outbreak in a neurosurgical unit at non-endemic region

Vancomycin-resistant enterococci (VRE) have emerged in many parts of the world, but have only been reported sporadically in Hong Kong. We report an outbreak of vancomycin-resistant Enterococcus faecium (VREfm) in a neurosurgical unit at a tertiary teaching hospital between 3 March and 3 April 2009 in Hong Kong. During the outbreak investigation, clinical samples from 193 (91.5%) of 211 patients who had stayed in the neurosurgical unit and 506 environmental samples were screened for VREfm. Besides the index case, another 3 (1.6%) out of 192 patients were found to be positive for VREfm. Two (0.4%) out of 506 environmental samples were positive for VREfm. All four clinical and two environmental isolates were found to be clonally related by pulse-field gel electrophoresis. The risk factors for nosocomial acquisition of VREfm included advanced age (P=0.047), presence of nasogastric tubing (P=0.002) and tracheostomy (P<0.001), and the use of β-lactam antibiotics (P<0.001) and vancomycin (P=0.001). Contrary to other VRE outbreaks in which the spread was rapid, the neurosurgical patients' immobilization because of coma and mechanical ventilation dependency, and the vigilant practice of hand hygiene by health-care workers successfully limited the number of secondary cases despite the delayed recognition of the index case. All patients with VREfm were labeled in the hospital network information system so that stringent infection control measures with contact precautions would be carried out once these patients were readmitted to prevent its spread in our locality.

Vancomycin MIC creep in MRSA isolates from 1997 to 2008 in a healthcare region in Hong Kong

OBJECTIVES

To assess whether vancomycin MIC creeps among blood methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from 5 hospitals in Hong Kong from 1997 to 2008.

METHODS

Blood cultures MRSA isolates from 1997 to 1999 (period 1), 2004 (period 2) and 2006-2008 (period 3) were retrieved. Etest method was used to determine their vancomycin MIC. The genotypic features were determined by PCR and sequencing.

RESULTS

247 blood MRSA isolates were studied. The vancomycin MIC were 0.375, 0.5, 0.75 and 1 mg/L for 15 (6.1%), 68 (27.5%), 89 (36%) and 75 (30.4%) isolates, respectively. There was an increase in the percentage of isolates with an MIC=1mg/L from 10.4% (5/48) during period 1 to 21.6% (8/37) during period 2 and 38.3% (62/162) during period 3 (period 1 vs. period 3, P<0.001). Molecular typing showed that this was due to increased percentages of clonal cluster (CC) 8/SCCmec III/IIIA (agr group I), CC45/SCCmec IV/V (agr group IV) and other minor clones with elevated MIC over time.

CONCLUSION

This study found vancomycin MIC creep among blood MRSA isolates over time. As elevated MIC within the susceptible range may reduce vancomycin efficacy, clinical laboratories should adopt methods with the required precision to accurately determine MICs.

Risk factors and outcomes of methicillin-resistant Staphylococcus aureus bacteraemia in critically ill patients: a case control study

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an increasing threat to critically ill patients in many intensive care units. MRSA bacteraemia is an extreme form of MRSA infection and is a significant cause of morbidity and mortality. This case control study aimed to assess the risk factors and outcomes of MRSA bacteraemia compared to methicillin-susceptible Staphylococcus aureus (MSSA) bacteraemia. A total of 21 MRSA bacteraemia and 60 randomly selected MSSA bacteraemia episodes, admitted to the intensive care unit at Royal Perth Hospital between 1997 and 2007, were considered. There was a suggestion that hospitalisation within the preceding six months (P = 0.087) and residence in a long-term care facility (P = 0.065) were associated with a higher risk of MRSA bacteraemia. MRSA bacteraemia was more often treated with antibiotics to which the pathogen was not susceptible in vitro (38.1% vs 0%, P = 0.001), resulting in a longer duration of fever (median 7.0 vs 2.0 days, P= 0.009) and bacteraemia (mean 3.2 vs 0.6 days, P = 0.005) and a higher incidence of metastatic seeding of infection (52.4% vs 21.7%, P = 0.012) as compared to MSSA bacteraemia. While in-hospital mortality between MRSA and MSSA was similarly high (47.6% vs 38.3% for MRSA and MSSA respectively, P = 0.607), a significant proportion of the patients who had MRSA bacteraemia died within five years of hospital discharge (36.4%, hazard ratio 26.0, 95% confidence interval 1.90 to 356.7, P = 0.015). Infections contributed to 75% of the deaths after hospital discharge in patients who had an episode of MRSA bacteraemia. MRSA bacteraemia carries a much worse long-term prognosis than MSSA bacteraemia and that could be explained by recurrent MRSA infections and residual confounding.

Bacteremia in previously hospitalized patients: prolonged effect from previous hospitalization and risk factors for antimicrobial-resistant bacterial infections

STUDY OBJECTIVE

Patients who came from the community but were recently discharged from the hospital have a higher risk of contracting antimicrobial-resistant bacterial infections. Our objectives are to determine the time from previous hospital discharge that affects subsequent antimicrobial susceptibility pattern and risk factors for antimicrobial-resistant infection in bacteremia in recently discharged patients.

METHODS

Excluding patients of hospital-acquired, patients with regular health care-associated exposure, and patients whose previous hospitalization was not at our hospital, a total of 789 nonduplicated bacteremia episodes from community adult patients were enrolled in a 1-year study period. Antimicrobial-resistant bacteria, including multidrug-resistant gram-negative bacilli, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci causing bacteremia, were logistically analyzed according to different posthospitalization periods (3 to 90 days, 91 to 180 days, 181 to 360 days, and no hospitalization in the past 360 days) to identify the independent effect from previous hospitalization on subsequent antimicrobial-resistant bacteremia.

RESULTS

Of the 789 bacteremia patients, the proportion of antimicrobial-resistant bacteremia is 14.6% (95% confidence interval [CI] 9.8% to 19.4%) for 3 to 90 days, 9.6% (95% CI 1.6% to 17.6%) for 91 to 180 days, and 6.4% (95% CI 0% to 13.4%) for 181 to 360 days since last hospitalization and 1.0% (95% CI 0.1% to 1.9%) for no hospitalization within the last 360 days. Risk of antimicrobial-resistant bacteremia decreased monthly after discharge by an odds ratio of 0.83 (95% CI 0.76 to 0.90) (P<.01). Previous carriage of antimicrobial-resistant bacteria in the past 360 days and previous stay at ICU in the past 180 days were independent risk factors for antimicrobial-resistant bacteremia in previously hospitalized patients.

CONCLUSION

Previous hospitalization affects the antimicrobial susceptibility of subsequent bacteremia up to 360 days after hospital discharge. Presence of risk factors for antimicrobial-resistant bacteremia in previously hospitalized patients may help emergency physicians in selecting empirical antimicrobial agents and prompting infection control precautions.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in residential care homes for the elderly in Hong Kong

This territory-wide study evaluated the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in residential care homes for elderly (RCHEs) in Hong Kong. MRSA colonization was assessed by taking swab culture from anterior nares and active skin lesions. Of 487 RCHEs surveyed, 80 MRSA strains were recovered from 1563 residents, giving a prevalence of 5.1%. Twenty-four isolates had SCCmec II, 2 had SCCmec III, 17 had SCCmec IV, 36 had SCCmec V, and 1 had a composite SCCmec type. Pulsed-field gel electrophoresis typing clustered 75 isolates into 7 clones (HKU10 to 50, HKU80, and HKU90). Two predominant types, HKU30 and HKU50, which together account for 75% of all MRSA strains, were found in 13 and 15 of the 18 geographic districts in Hong Kong, respectively. The main features for HKU50 strains were spa t1081/ST45-IV or V, capsular type 8, agrIV, and hla, seg, sei positive. On the other hand, HKU30 strains had spa t002/ST5-II, capsular type 5, agrII, and were hla, seg, sei positive. HKU30 strains were often multidrug resistant (MDR, involving ciprofloxacin, erythromycin, gentamicin, and tetracycline). In contrast, HKU50 strains exhibit both multidrug resistance (MDR) (involving ciprofloxacin, erythromycin, and tetracycline, but not gentamicin) and non-MDR patterns.

Relationship between immunosuppression and intensive care unit-acquired multidrug-resistant bacteria: a case-control study

OBJECTIVE

To determine the relationship between immunosuppression and intensive care unit (ICU)-acquired multidrug-resistant (MDR) bacteria.

DESIGN

Retrospective case-control study based on prospectively collected data.

SETTING

A 30-bed medical and surgical ICU.

PATIENTS

All patients hospitalized >48 hrs in the ICU were eligible during a 2-yr period.

INTERVENTIONS

Immunosuppression was defined as active solid or hematologic malignancy, leucopenia, or chronic immunosuppressive treatment. MDR bacteria were defined as methicillin-resistant Staphylococcus aureus, ceftazidime- or imipenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia, and extending spectrum beta-lactamase producing Gram-negative bacilli. MDR bacteria screening (nasal, anal, and axilla swabs and tracheal aspirate in intubated patients) was performed at ICU admission and weekly. Only MDR bacteria isolated >48 hrs after ICU admission were taken into account; duplicates were excluded. Isolation measures were applied in all patients at ICU admission, in patients with MDR bacteria, and in patients with immunosuppression. Immunosuppressed patients (cases) were matched (1:1) with immunocompetent patients (controls) according to all the following criteria: age +/-5 yrs, Simplified Acute Physiology Score II +/-5, duration of ICU stay +/-3 days, and category of admission (medical/surgical). Risk factors for ICU-acquired MDR bacteria were determined using univariate and multivariate analyses.

MEASUREMENTS AND MAIN RESULTS

Of 1,065 eligible patients, nine patients were excluded for absence of MDR bacteria screening at ICU admission. One hundred thirty-three (12%) patients were immunosuppressed, and 128 (96%) of them were successfully matched. Mean time between ICU admission and first ICU-acquired MDR bacteria was 12 +/- 9 days. Incidence of MDR bacteria was significantly higher in cases than in controls (22 vs. 12 MDR bacteria/1000 ICU days, p = .004). However, immunosuppression was not independently associated with ICU-acquired MDR bacteria.Multivariate analysis identified prior antibiotic treatment and antibiotic treatment in the ICU as risk factors for ICU-acquired MDR bacteria (odds ratio [95% confidence interval] = 1.9 [1-3.6], p = .003; 11 [1.4-83], p = .02; respectively).

CONCLUSIONS

Immunosuppression is not independently associated with ICU-acquired MDR bacteria. However, infection control measures used in our ICU may have influenced this result.

Epidemiology and genetic diversity of methicillin-resistant Staphylococcus aureus strains in residential care homes for elderly persons in Hong Kong

OBJECTIVE

To determine the prevalence and molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) strains among residents in residential care homes for the elderly in Hong Kong.

DESIGN

Cross-sectional and descriptive study.

PARTICIPANTS

A total of 949 residents in 13 residential care homes for elderly persons in Hong Kong in January 2005.

METHODS

MRSA colonization was assessed by culture of swab specimens from anterior nares and active skin lesions. Characteristics of residents were obtained by a standard questionnaire. All MRSA isolates were analyzed by polymerase chain reaction for their staphylococcal cassette chromosome (SCC) mec content and were typed by pulsed-field gel electrophoresis (PFGE) and multilocus sequencing.

RESULTS

MRSA colonization was detected in 27 residents (2.8%). No MRSA was found in 2 facilities. The rate of MRSA carriage in the other 11 facilities ranged from 1.9% to 4.2%. In univariate analysis, functional immobility (odds ratio [OR], 1.4), history of hospital admission (OR, 2.3), and the use of nebulized medication (OR, 5.4) were significantly associated with MRSA colonization. The isolates had 11 unique antibiograms, with 14 isolates susceptible to all but 1 or 2 of the non- beta -lactam antimicrobial agents tested. The isolates exhibited SCCmec types I (1 isolate), II (2 isolates), III (1 isolate), IV/IVA (10 isolates), and V (13 isolates). No isolates had the Panton-Valentine leukocidin genes. PFGE analysis clustered all except 1 isolate into 7 PFGE types, designated HKU10 to HKU70. Between 1 and 4 unique PFGE types were found in the individual residential care facilities.

CONCLUSION

This study documented the emergence of SCCmec types IV and V among genetically diverse MRSA strains in residential care homes for elderly persons in Hong Kong.

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.

Molecular epidemiology and household transmission of community-associated methicillin-resistant Staphylococcus aureus in Hong Kong

This study evaluated the clinical and epidemiologic features of individuals with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Hong Kong from January 2004 through December 2005. Twenty-four episodes of skin and soft tissue infections and 1 episode of meningitis due to CA-MRSA were identified. CA-MRSA infections or carriage was found in 6 (13%) of 46 household contacts. A total of 29 isolates were analyzed by the Staphylococcus cassette chromosome mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing. In addition, polymerase chain reaction detection of the genes encoding Panton-Valentine leukocidin was also carried out. It was observed that 24 had SCCmec IV/IVA and 5 had SCCmec V, and 23 were pvl positive. PFGE analysis clustered all except 1 isolate into 3 pulsed-field types (PFTs), HKU100 through HKU300. The HKU100 isolates had genotype ST30-IV identical to the Southwest Pacific clone. The HKU200 isolates belonged to ST59-V and were multiresistant, including an ermB-mediated macrolide resistance trait, which is characteristic of the predominant CA-MRSA clone in Taiwan. The HKU300 isolates had unique features (ST8, Panton-Valentine leukocidin negative, and SCCmec IVA) typical of CA-MRSA in Japan. In conclusion, CA-MRSA has a propensity to spread within families. Our findings showed that CA-MRSA strains in Hong Kong have diverse genetic backgrounds.

Evaluation of rapid screening and pre-emptive contact isolation for detecting and controlling methicillin-resistant Staphylococcus aureus in critical care: an interventional cohort study

INTRODUCTION

Rapid diagnostic tests may allow early identification of previously unknown methicillin-resistant Staphylococcus aureus (MRSA) carriers at intensive care unit (ICU) admission. The aim of this study was twofold: first, to assess whether a new molecular MRSA screening test can substantially decrease the time between ICU admission and identification of MRSA carriers; and, second, to examine the combined effect of rapid testing and pre-emptive contact isolation on MRSA infections.

METHOD

Since November 2003, patients admitted for longer than 24 hours to two adult ICUs were screened systematically on admission using quick, multiplex immunocapture-coupled PCR (qMRSA). Median time intervals from admission to notification of test results were calculated for a five-month intervention phase (November 2003-March 2004) and compared with a historical control period (April 2003-October 2003) by nonparametric tests. ICU-acquired MRSA infection rates were determined for an extended surveillance period (January 2003 through August 2005) and analyzed by Poisson regression methods.

RESULTS

During the intervention phase, 97% (450/462) of patients admitted to the surgical ICU and 80% (470/591) of patients admitted to the medical ICU were screened. On-admission screening identified the prevalence of MRSA to be 6.7% (71/1053). Without admission screening, 55 previously unknown MRSA carriers would have been missed in both ICUs. Median time from ICU admission to notification of test results decreased from 87 to 21 hours in the surgical ICU (P < 0.001) and from 106 to 23 hours in the medical ICU (P < 0.001). In the surgical ICU, 1,227 pre-emptive isolation days for 245 MRSA-negative patients were saved by using the qMRSA test. After adjusting for colonization pressure, the systematic on-admission screening and pre-emptive isolation policy was associated with a reduction in medical ICU acquired MRSA infections (relative risk 0.3, 95% confidence interval 0.1-0.7) but had no effect in the surgical ICU (relative risk 1.0, 95% confidence interval 0.6-1.7).

CONCLUSION

The qMRSA test decreased median time to notification from four days to one day and helped to identify previously unknown MRSA carriers rapidly. A strategy linking the rapid screening test to pre-emptive isolation and cohorting of MRSA patients substantially reduced MRSA cross-infections in the medical but not in the surgical ICU.

Molecular epidemiology of clinical and carrier strains of methicillin resistant Staphylococcus aureus (MRSA) in the hospital settings of north India

BACKGROUND

The study was conducted between 2000 and 2003 on 750 human subjects, yielding 850 strains of staphylococci from clinical specimens (575), nasal cultures of hospitalized patients (100) and eye & nasal sources of hospital workers (50 & 125 respectively) in order to determine their epidemiology, acquisition and dissemination of resistance genes.

METHODS

Organisms from clinical samples were isolated, cultured and identified as per the standard routine procedures. Susceptibility was measured by the agar diffusion method, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The modified method of Birnboin and Takahashi was used for isolation of plasmids from staphylococci. Pulsed-field gel electrophoresis (PFGE) typing of clinical and carrier Methicillin resistant Staphylococcus aureus (MRSA) strains isolated during our study was performed as described previously.

RESULTS

It was shown that 35.1% of Staphylococcus aureus and 22.5% of coagulase-negative staphylococcal isolates were resistant to methicillin. Highest percentage of MRSA (35.5%) was found in pus specimens (n = 151). The multiple drug resistance of all MRSA (n = 180) and Methicillin resistant Coagulase-negative Staphylococcus aureus (MRCNS) (n = 76) isolates was detected. In case of both methicillin-resistant as well as methicillin-sensitive Saphylococcal isolates zero resistance was found to vancomycin where as highest resistance was found to penicillin G followed by ampicillin. It was shown that the major reservoir of methicillin resistant staphylococci in hospitals are colonized/infected inpatients and colonized hospital workers, with carriers at risk for developing endogenous infection or transmitting infection to health care workers and patients. The results were confirmed by molecular typing using PFGE by SmaI-digestion. It was shown that the resistant markers G and T got transferred from clinical S. aureus (JS-105) to carrier S. aureus (JN-49) and the ciprofloxacin (Cf) and erythromycin (E) resistance seemed to be chromosomal mediated. In one of the experiments, plasmid pJMR1O from Staphylococcus aureus coding for ampicillin (A), gentamicin (G) and amikacin (Ak) resistance was transformed into Escherichia coli. The minimal inhibitory concentrations (MICs) for A and G were lower in E. coli than in S. aureus. However, the MIC for Ak was higher in E. coli transformants than in S. aureus.

CONCLUSION

There is a progressive increase in MRSA prevalence and multi-drug resistance in staphylococci. Vancomycin is still the drug of choice for MRSA infections. The major reservoir of methicillin resistant staphylococci in hospitals is colonized/infected inpatients and colonized hospital workers. Resistance transfer from staphylococci to E. coli as well as from clinical to carrier staphylococci due to antibiotic stress seemed to be an alarming threat to antimicrobial chemotherapy.

Antibiotic resistance in long-term acute care hospitals: the perfect storm

OBJECTIVE

To examine bacterial antibiotic resistance and antibiotic use patterns in long-term acute care hospitals (LTACHs) and to evaluate effects of antibiotic use and other hospital-level variables on the prevalence of antibiotic resistance.

DESIGN

Multihospital ecologic study.

METHODS

Antibiograms, antibiotic purchasing data, and demographic variables from 2002 and 2003 were obtained from 45 LTACHs. Multivariable regression models were constructed, controlling for other hospital-level variables, to evaluate the effects of antibiotic use on resistance for selected pathogens. Results of active surveillance in 2003 at one LTACH were available.

RESULTS

Among LTACHs, median prevalences of resistance for several antimicrobial-organism pairs were greater than the 90th percentile value for National Nosocomial Infections Surveillance system (NNIS) medical intensive care units (ICUs). The median prevalence of methicillin resistance among Staphylococcus aureus isolates was 84%. More than 60% of patients in one LTACH were infected or colonized with methicillin-resistant S. aureus and/or vancomycin-resistant Enterococcus at the time of admission. Antibiotic consumption in LTACHs was comparable to consumption in NNIS medical ICUs. In multivariable logistic regression modeling, the only significant association between antibiotic use and the prevalence of antibiotic resistance was for carbapenems and imipenem resistance among Pseudomonas aeruginosa isolates (odds ratio, 11.88 [95% confidence interval, 1.42-99.13]; P=.02).

CONCLUSIONS

The prevalence of antibiotic resistance among bacteria recovered from patients in LTACHs is extremely high. Although antibiotic use in LTACHs likely contributes to resistance prevalence for some antimicrobial-organism pairs, for the majority of such pairs, other variables, such as prior colonization with and horizontal transmission of antimicrobial-resistant pathogens, may be more important determinants. Further research on antibiotic resistance in LTACHs is needed, particularly with respect to determining optimal infection control practices in this environment.

[Meticillin-resistant Staphylococcus aureus: incidence, risk factors and interest of systematic screening for colonization in intensive-care unit]

OBJECTIVE

To summarize recent international and national epidemiological data of methicillin-resistant Staphylococcus aureus (MRSA) colonization in ICU.

STUDY DESIGN

Review articles using Medline, CDC (Atlanta, GA, USA) and IVS (St Maurice, France) databases (1994-2004): critical assessment of literature and data of MRSA colonization epidemiology in ICU.

RESULTS

MRSA colonization varied from 3 to 14% on ICU admission. Five to twelve percent of patient acquired MRSA colonization during hospitalization. This reservoir is often unknown as clinical sample identifies only a part of MRSA colonization. The probability to develop an infection caused by MRSA in colonized patients is about 30%. Acquisition of MRSA in ICU patients is strongly and independently influenced by colonization pressure.

CONCLUSION

Systematic screening for colonization on ICU admission and during hospitalization is essential for many authors to control the spread of MRSA. Other policies such as implementation of isolation precaution and antibiotic use also contribute to decrease the MRSA incidence rate observed for several years in French ICU.

Evaluating the probability of previously unknown carriage of MRSA at hospital admission

PURPOSE

We determined the prevalence and risk profile of patients with previously unknown carriage of methicillin-resistant Staphylococcus aureus (MRSA) at hospital admission.

SUBJECTS AND METHODS

We conducted a 7-month, prospective case-controlled study in adult inpatients admitted to a university hospital with endemic MRSA. Multivariate conditional logistic regression for data sets matched 1:4 was performed to identify the risk profile of newly identified MRSA carriers.

RESULTS

Overall, 399 of 12072 screened admissions (prevalence, 3.3%) were found colonized (n = 368, 92%) or infected (n = 31, 8%) with MRSA. In 204 cases (prevalence, 1.7%), MRSA carriage was newly identified. Without screening on admission, 49% (196/399) of MRSA carriers would have been missed. We identified nine independent risk factors for newly identified MRSA carriage at admission (adjusted odds ratio): male sex (1.9); age greater than 75 years (2.0); receipt of fluoroquinolones (2.7), cephalosporins (2.1), and carbapenems (3.2) in the last 6 months; previous hospitalization (1.9) or intravenous therapy (1.7) during the last 12 months; urinary catheter at admission (2.0); and intrahospital transfer (2.4). A risk score (range, 0-13) was calculated by adding points assigned to these variables. On the basis of analysis of 1006 patients included in the case-controlled study, the probability of MRSA carriage was 8% (28/342) in patients with a low score (< or =1), 19% (92/482) in patients with an intermediate score (2-4), and 46% (84/182) in patients with a high score (> or =5). The risk score had good discrimination (c-statistic, 0.73) and showed excellent calibration (P = .88).

CONCLUSIONS

On-admission prevalence of previously unknown MRSA carriers was high. Applying the risk score to newly admitted patients with an intermediate or high probability of MRSA carriage could allow a more effective MRSA control strategy.

Neumonía nosocomial causada por Staphylococcus aureus resistente a meticilina

Methicillin-resistant Staphylococcus aureus (MRSA) is an increasingly common cause of hospital acquired pneumonia (HAP) and the second most frequently isolated pathogen from patients who die from HAP. High-risk units for MRSA colonization such as intensive care (ICU's) are the most affected. Multiple risk factors for transmission of MRSA have been identified, including colonization pressure and severity of illness at ICU admission. On the other hand, the most important predisposing factor for MRSA infection is prolonged mechanical ventilation and/or previous antibiotic therapy. Controlling the spread of MRSA remains a major challenge for hospitals. Screening programs, together with contact precautions for cases with MRSA and judicious antimicrobial use are major factors for a successful control. Early appropriate initial therapy is of crucial importance and improves outcome. The standard therapy has been glycopeptides but, in spite of its in vitro activity, mortality in critically ill patients treated with glycopeptides has consistently been reported high, mainly due to their poor lung penetration. Linezolid shows better clinical cure and survival rates, but further studies are needed. As the treatment options for MRSA pneumonia are limited and inadequate, development of more effective drugs is mandatory.

An agent-based and spatially explicit model of pathogen dissemination in the intensive care unit*

OBJECTIVE

To develop and disseminate a spatially explicit model of contact transmission of pathogens in the intensive care unit.

DESIGN

A model simulating the spread of a pathogen transmitted by direct contact (such as methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus) was constructed. The modulation of pathogen dissemination attending changes in clinically relevant pathogen- and institution-specific factors was then systematically examined.

SETTING AND PATIENTS

The model was configured as a hypothetical 24-bed intensive care unit. The model can be parameterized with different pathogen transmissibilities, durations of caregiver and/or patient contamination, and caregiver allocation and flow patterns.

INTERVENTIONS

Pathogen- and institution-specific factors examined included pathogen transmissibility, duration of caregiver contamination, regional cohorting of contaminated or infected patients, delayed detection and isolation of newly contaminated patients, reduction of the number of caregiver visits, and alteration of caregiver allocation among patients.

MEASUREMENTS AND MAIN RESULTS

The model predicts the probability that a given fraction of the population will become contaminated or infected with the pathogen of interest under specified spatial, initial prevalence, and dynamic conditions. Per-encounter pathogen acquisition risk and the duration of caregiver pathogen carriage most strongly affect dissemination. Regional cohorting and rapid detection and isolation of contaminated patients each markedly diminish the likelihood of dissemination even absent other interventions. Strategies reducing "crossover" between caregiver domains diminish the likelihood of more widespread dissemination.

CONCLUSIONS

Spatially explicit discrete element models, such as the model presented, may prove useful for analyzing the transmission of pathogens within the intensive care unit.

Methicillin-resistant Staphylococcus aureus infections in ICU patients

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in patients admitted to the intensive care unit has dramatically increased in recent years, with an associated increase in morbidity and mortality and the costs of caring for patients with MRSA infections. Although indiscriminate and inappropriate use of antibiotics has contributed to this phenomenon, horizontal transmission of MRSA between patients and health care providers is the principal cause of this observed increase. This article discusses the pathogenesis, epidemiology, treatment, and prevention of MRSA infections in critically ill patients.