Methicillin-resistant Staphylococcus Aureus Positivity Research Articles

Evaluation of PhenoMATRIX and PhenoMATRIX PLUS for the screening of MRSA from nasal and inguinal/perineal swabs using chromogenic media.

The objective of this study was to assess the clinical performances of PhenoMATRIX and PhenoMATRIX PLUS for the screening of methicillin-resistant Staphylococcus aureus (MRSA) from nasal and inguinal/perineal ESwabs using chromogenic media. The automated performances were compared to the manual reading. Additionally, we evaluated PhenoMATRIX PLUS for the automatic release of the negative results to the Laboratory Information System (LIS) and the automatic discharge of the negative plates from the incubators. A total of 6,771 non-duplicate specimens were used by PhenoMATRIX as a machine learning model. The validation of these settings was performed on 17,223 non-duplicate specimens. The MRSA positivity rate was 5% (866/17,223). Validated settings were then used by PhenoMATRIX PLUS on another 1,409 non-duplicate specimens. The sensitivities of PhenoMATRIX and PhenoMATRIX PLUS were 99.8% [95% confidence interval (CI), 99.2%-99.9%] and 100% (95% CI, 92.1%-100%), respectively. The specificities of PhenoMATRIX and PhenoMATRIX PLUS were 99.1% (95% CI, 99.0%-99.2%) and 95.2% (95% CI, 93.8%-96.1%), respectively. All the 1,297 MRSA-negative specimens analyzed by PhenoMATRIX PLUS were automatically released and sent to the LIS immediately after availability of the culture image on the WASPLab (100% accuracy). All negative media plates were automatically discarded. PhenoMATRIX PLUS decreases the time spent by technologists on negative plates and ensures optimal usage of the incubators' capacity.

Prevalence and clinical relevance of colonization with methicillin-resistant Staphylococcus aureus in the obstetric population

Background and aims Routine screening for Methicillin-Resistant Staphylococcus aureus (MRSA) in pregnant women is common practice in many hospitals. However, little is known on its prevalence and clinical relevance in this population. In this prospective longitudinal study, we aimed to investigate the MRSA prevalence in our obstetric population, the rate of vertical transmission of MRSA and the potential clinical relevance of MRSA colonization for both mother and child. A possible correlation between GBS and MRSA colonization was also investigated. Materials and methods MRSA screening samples were collected at 35–37 weeks of gestation (from mother), at delivery and at discharge (from mother and newborn). All samples were analyzed by conventional microbiological methods and MRSA strains were subjected to spa-typing to investigate genetic similarity. The medical records of all positive mother-child pairs were analyzed to detect the occurrence of clinical infection in the postpartum period. Results 679 mother-child pairs were included between June 2014 and July 2016. Maternal MRSA positivity rate was 1.3% at 35–37 weeks (vaginal/anorectal), 3.1% at delivery (nose/throat) and 3.6% at discharge (nose/throat). MRSA positivity in neonates was 0.3% at delivery and increased to 3% at discharge (nose/umbilicus). Almost all MRSA positive children were born to MRSA positive mothers (OR 120.40, 95% CI: 38.42–377.32). Genetic similarity of the MRSA strains found in mother and child was illustrated for all but one case. 57.7% of the cases of MRSA colonization in our cohort were associated with livestock exposure. 31% of the MRSA positive mothers developed an infectious complication in the postpartum period. No neonatal infectious complications were observed. GBS positivity was not a predictive factor for MRSA colonization in our cohort. Conclusion The rate of MRSA colonization (overall 4.3%) in our obstetric population is similar to that described in the literature and that of the general population admitted to our hospital in the same period. Maternal MRSA colonization appeared to be an important risk factor for neonatal colonization. Whereas mothers were at higher risk of developing infectious morbidity in the postpartum period, no neonatal infectious complications were observed. We observed no correlation between GBS and MRSA colonization.

Nasal colonization with methicillin-resistant Staphylococcus aureus at admission among high-risk Turkish and international patients.

The aim of this study was to detect the frequency of methicillin-resistant Staphylococcus aureus (MRSA) colonization at admission in a group of presumably high-risk international or Turkish patients referred to our center for elective operations, some of whom were from countries with an unknown prevalence of MRSA infection or colonization. The results of nasal swab screening for MRSA colonization performed using a specific algorithm between 2011 and 2018 in a private medical center were retrospectively reviewed. Presence of MRSA was ascertained using culture and/or real-time polymerase chain reaction (real-time PCR). A total of 3,795 patients were included in the study. More than half of the patients were ≤19 years of age (2,094, 55.2%), and MRSA positivity was more common among these patients. Turkish patients constituted 24.5% of the study population. International patients were most frequently referred from Iraq (55.92%), Libya (11.44%), Romania (2.69%), and Bulgaria (1.98%). MRSA positivity was significantly more common among patients referred from other countries when compared to Turkish nationals (11.5% vs. 4.4%, P = 0.00001). Countries with the highest prevalence rates of MRSA colonization were as follows with decreasing order: United Arab Emirates, 25.0%; Georgia, 23.1%; Russia, 22.7%; Iraq, 13.0%, Romania, 12.7%. Other countries with high number of admitted patients (>70 patients) had the following MRSA rates: Turkey, 4.4%; Libya, 6.0%; Bulgaria, 5.3%. Although MRSA has a low prevalence in our center, a variation in the rate of MRSA positivity was observed across patients from different countries. Absence hospital acquired contamination or outbreaks in our institution may be attributed to the screening algorithm used and underscores the importance of risk analysis for patients referred from geographical locations with unknown MRSA frequency, to reduce the risk of transmission.

Vitamin D supplementation to persistent carriers of MRSA\u2014a randomized and placebo-controlled clinical trial

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to all beta-lactam antibiotics and can cause severe infections that are difficult to treat. Eradication strategies with conventional antibiotics are not always effective and alternative approaches are warranted. Here, we tested the hypothesis that daily supplementation with vitamin D for 12 months would reduce MRSA carriage rates among a group of persistent carriers. This was a double-blind, placebo-controlled randomized trial with n = 65 persistent MRSA carriers with 25-hydroxy vitamin D3 (25OHD) < 75 nmol/L, who were followed up with bacterial cultures at baseline and every 3 months for 1 year. The primary endpoint was the decline in MRSA positivity during the study period. The study was conducted in two MRSA outpatient clinics at the Karolinska University Hospital, Stockholm, Sweden. In total, n = 65 persistent MRSA carriers were randomized and n = 3 were lost to follow-up. Only patients deficient in vitamin D (< 75 nmol/L) were included. Vitamin D (4000 IU) or placebo/day was administered for 12 months. The decline in MRSA positivity was equal in the vitamin D and placebo group during the study period (OR, 1.00; 95% CI, 0.97–1.03; p = 0.928) and approximately 40% in both groups were MRSA-negative after 12 months. The vitamin D group produced 103 positive cultures out of 318 cultures (32.4%) from nose, throat, and perineum over the study period, whereas the placebo group produced 135/393 positive cultures (34.0%) (Fisher’s exact test, p = 0.94). Vitamin D supplementation did not influence MRSA carriage. Thus, available data does not support vitamin D supplementation to persistent MRSA carriers.Trial registration:www.clinicaltrials.gov; NCT02178488.

Using multiplex PCR as a diagnostic tool to detect methicillin resistant Staphylococcus aureus

Aim: The goal of this report was to deliver the methicillin resistant Staphylococcus aureus (MRSA) reports to the clinician and prevent the treatment delays, investigating the efficacy in addition to diagnostic testing and contact isolation strategies for intensive care unit (ICU) patients with MRSA.Methods: In this report, 320 Staphylococcus aureus strains identified as coagulase positive were cultured from hospitalized ICU patients between 2015 and 2017. Wound swabs were performed and bacteria cultures were evaluated for identification and antibiotic susceptibility testing using a culture antibiogram. Among these cultures from the swabs, MRSA was identified and subsequently screened for the MecA gene using rapid Multiplex polymerase chain reaction (PCR).Results: MRSA was detected in 67 of 320 strains, because of oxacillin resistance was detected by working with a fully automated culture antibiogram device. In addition, MRSA positivity was detected because of the high MecA gene expression in 56 of these 67 strains using rapid multiplex PCR. Conclusion: With greater than 86% sensitivity, patients were able to get early treatment for MRSA due to the rapid screening analysis using Multiplex PCR. This method, as a diagnostic tool, may be of benefit in other diseases.

Rate of contamination of hospital privacy curtains in a burns/plastic ward: A longitudinal study

Since hospital patient privacy curtains can harbor bacteria, are high-touch surfaces, and are cleaned infrequently, they may be involved in pathogen transmission. The aim of this longitudinal prospective study was to understand curtain contamination to inform curtain hygiene protocols, thereby minimizing the role of curtains in pathogen transmission. Over 21 days, cultures of 10 freshly laundered curtains (8 test curtains surrounding patient beds and 2 controls in an unoccupied staff room) were taken in the Regional Burns/Plastics Unit. Contact plates were used to sample the curtains near the edge hem where they are most frequently touched. Microbial contamination and the presence of methicillin-resistant Staphylococcus aureus (MRSA) were determined. By day 3, test curtains showed increased microbial contamination (mean colony-forming units [CFU]/cm2 = 1.17) compared to control curtains (mean CFU/cm2 = 0.19). Test curtains became increasingly contaminated over time, with mean CFU/cm2 for days 17 and 21 of 1.86 and 5.11, respectively. By day 10, 1/8 test curtains tested positive for MRSA, and 5/8 were positive by day 14. Patient privacy curtains became progressively contaminated with bacteria, including MRSA. Between days 10 and 14 after being hung, curtains showed increased MRSA positivity. This may represent an opportune time to intervene, either by cleaning or replacing the curtains.

The effects of regular hot black tea consumption on nasal carriage of methicillin-resistant Staphylococcus aureus.

This study aims to evaluate the possible relationship between oral consumption of hot black tea and methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage in a mid-sized town population in central Anatolia. Nasal swabs were taken from a total of 109 subjects (53 females, 56 males; mean age 34.4 years; range 18 to 65 years) including 55 non-tea drinkers and 54 subjects consuming more than 10 cups of tea a day. The MRSA positivity in the nasal cultures was investigated. In the tea consumer group MRSA was cultured in 10 subjects. Twenty-one subjects' nasal cultures were positive for MRSA in the non-tea drinkers. We found a statistically significant difference in the nasal MRSA carriage among tea drinkers and non-tea drinkers. Our study findings indicate a lower incidence of nasal MRSA carriage in tea drinkers, suggesting that certain soluble tea compounds may exhibit some antibacterial properties when consumed orally.

Correlation between animal nasal carriage and environmental methicillin-resistant Staphylococcus aureus isolates at U.S. horse and cattle farms

Animals on farms may be a potential reservoir and environmental source of methicillin-resistant Staphylococcus aureus (MRSA). Expanded surveillance methods for animal-associated MRSA are needed. To develop an environmental sampling method and to determine the correlation between animal and environmental MRSA positivity in the farm setting, we sampled horses, cattle, and their local environments at several farms in the mid-Atlantic United States. We obtained nasal swabs from 13 racehorses at first visit, and 11 racehorses at the same farm eight weeks later. We also sampled 26 pleasure horses and 26 beef cattle from two additional farm sites. Sterilized electrostatic cloths were used to collect dry dust samples from environmental surfaces in proximity to animals; cloths were cultured using a broth enrichment protocol. We described isolates by genotype and antimicrobial susceptibility phenotype. None of the samples (nasal or environmental) were positive from the pleasure horse farm or the cattle farm. On the racehorse farm, 8/13 (61%) nasal and 5/7 (71%) environmental samples were positive for MRSA at the first visit. Isolates found were indistinguishable by pulsed-field gel electrophoresis (PFGE) genotype. We observed significant positive correlation between nasal carriage of MRSA in animals and our ability to isolate MRSA from dry surface samples of their local environments. The methods presented here may aid in surveillance efforts for equine and other animal MRSA. This study successfully applies existing MRSA surveillance methods for indoor, high animal density settings to outdoor and low-density farms.

Carriage of methicillin-resistant Staphylococcus aureus on admission to European rehabilitation centres-a prospective study

This study aimed to determine the prevalence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) carriage among patients newly admitted to rehabilitation centres. It is a prospective study examining MRSA carriage on admission to seven rehabilitation wards in four countries. Risk factors for MRSA carriage were analysed using univariate and multivariate analyses. A total of 1204 patients were studied. Among them, 105 (8.7%) had a positive admission MRSA screening result. The MRSA carriers were more likely to be male, to have had a recent stay in another long-term-care facility or >2 weeks acute-care hospital stay, history of colonization with MRSA, reduced level of consciousness, peripheral vascular disease and pressure sores. In multivariable logistic regression male gender (odds ratio (OR) 2.2, 95% confidence interval (CI) 1.4-3.6, p 0.001), history of MRSA positivity (OR 6.8, 95% CI 3.8-12.3, p <0.001), peripheral vascular disease (OR 2.5, 95% CI 1.2-5, p 0.013), recent stay in another long-term-care facility (OR 2.1, 95% CI 1.3-3.5, p 0.004), or long (>2 weeks) acute-care hospital stay (OR 1.9, 95% CI 1.2-3, p 0.004), remained significant risk factors for MRSA carriage. MRSA carriage is common on admission to rehabilitation centres but less so, than previously described in long-term-care facilities. Male gender, history of MRSA positivity, previous hospitalization and peripheral vascular disease may predict MRSA carriage, and may serve as indicators for using pre-emptive infection control measures.

Editorial Commentary: Deconstructing the Veterans Affairs MRSA Prevention Bundle

During the 1970s and 1980s, methicillinresistant Staphylococcus aureus (MRSA) became endemic in hospitals worldwide [1]. By 2007, a large-scale epidemiological study determined that 94 000 cases of invasive MRSA disease and 19 000 MRSA-related in-hospital deaths occurred annually in the United States [2]. Using these estimates, an editorial suggested that the burden of MRSA deaths exceeded that of deaths due to human immunodeficiency virus or AIDS in the United States [3]. TheoptimalapproachtoMRSAprevention in hospital settings is debated [4, 5]. In general, 2 epidemiological approaches have been described: (1) “horizontal” programs that broadly attempt to reduce infections from all pathogens and (2) “vertical” programs that aim to eradicate a single pathogen [6]. Horizontal programs include hand hygiene improvement interventions and centralline association bloodstream infection (CLABSI) “bundles.” Vertical programs screen all or selected patients for MRSA colonization by obtaining a nares swab sample and place MRSA-colonized or MRSA-infected patients on contact precautions. Contact precautions include single-bed rooms and patient cohorting and require healthcare workers to wear gowns and gloves for all contacts. Some studies reported benefits of such screening programs [7], some reported benefits when screening was combined with decolonization [8], and some found screening and isolation to be ineffective [9, 10]. After a successful pilot study in the VA Pittsburgh Healthcare System, in August 2006 the Veterans Health Administration implemented a MRSA bundle in 17 US Department of Veterans Affairs (VA) medical centers [11]. The bundle included (1) admission, inhospital transfer, and discharge activesurveillance swab samples for MRSA; (2) contact precautions for patients known or found to be MRSA carriers; (3) efforts targeting improved hand hygiene; and (4) efforts encouraging culture change [12]. Importantly, and infrequently, mentioned in descriptions of the VA MRSA Initiative, support was also made available for a MRSA prevention coordinator at each site, who was responsible for coordinating implementation of the bundle. Thus, the VA bundle included 1 vertical intervention (swab samples and contact precautions) and 3 horizontal interventions (hand hygiene, culture change, and MRSA prevention coordinator). By October 2007 the bundle was implemented in all acute-care (except mental health) units in 150 of 153 VA medical centers. By most measures the VA MRSA Initiative was a success. From initiation to June 2010, healthcare-associated MRSA infections declined by 62% in intensive care units (ICUs) and by 45% in nonICUs. MRSA acquisition declined 17% in ICUs and 21% in non-ICU settings. Interestingly, a subset of hospitals reported healthcare-associated vancomycin-resistant enterococcal and Clostridium difficile infection rates. After the initiative, vancomycin-resistant enterococcal infections were eliminated in ICUs and declined by 73% in non-ICUs. C. difficile infections declined 61% in non-ICU settings, with no change in ICUs [12]. How do we explain the MRSA declines reported by the VA? A nationwide decline in MRSA seen during the study period [13] might have contributed to these in-hospital declines; however, MRSA positivity on admission was relatively flat during the study period, so any outside impact should have been negligible. Importantly, infections declined 2–3 times more than incident colonization, suggesting that factors other than surveillance swab samples and isolation played a role in reduced MRSA infections. Thus, it seems that one benefit of the bundle was to reduce Received 22 February 2012; accepted 24 February 2012; electronically published 4 April 2012. Correspondence: Eli N. Perencevich, MD, MS, CADRE, Iowa City VA Medical Center, 601 Hwy 6 W, Iowa City, IA 52246 (eli-perencevich@uiowa.edu). Clinical Infectious Diseases 2012;54(11):1621–3 © The Author 2012. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com. DOI: 10.1093/cid/cis277

Factors Associated with Post-Operative Conversion to Methicillin-ResistantStaphylococcus AureusPositivity or Infection in Initially MRSA-Negative Patients

Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) is associated with morbid, invasive infections and has been implicated in nearly every type of nosocomial infection. Our aim was to identify the risk factors for patient conversion from MRSA negativity pre-operatively to MRSA positivity post-operatively. We retrospectively reviewed all patients at the Veterans Affairs-Boston Health Care System who underwent clean or clean-contaminated surgical procedures during the years 2008 and 2009 and had documented pre-operative nasal polymerase chain reaction (PCR) testing for MRSA. We abstracted post-operative MRSA microbiologic testing results, MRSA infections, surgical site infections (SSIs), surgical prophylaxis data, and SSI risk index, as calculated using the Veterans Affairs Surgical Quality Improvement Project (VASQIP) database variables. All patients who had a negative nasal MRSA PCR result in the 31-day pre-operative period and did not have any positive MRSA clinical swab or culture in the 1-year pre-operative period were defined as MRSA-negative. These patients were classified as converters to MRSA positivity if they had at least one documented positive nasal MRSA PCR swab, culture, nosocomial infection, or SSI within 31 days post-operatively. Among 4,238 eligible patients, 3,890 (92%) qualified as MRSA-negative pre-operatively. A total of 1,432 (37%) of these patients were assessed in the VASQIP database, of whom 34 (2%) converted to MRSA positivity post-operatively. On multivariable logistic regression analysis of the VASQIP sample, age (odds ratio [OR] 1.049; 95% confidence interval [CI] 1.016, 1.083), SSI risk index (OR 2.863; 95% CI 1.251-6.554), and vancomycin prophylaxis alone or in combination (OR 3.223; 95% CI 1.174-8.845) were significantly associated with conversion to MRSA positivity. In pre-operatively MRSA-negative patients, age, SSI risk index, and vancomycin prophylaxis were significant factors for conversion to MRSA positivity post-operatively. Alternatives to vancomycin prophylaxis in non-colonized patients and optimization of patients' SSI risk factors should be considered before elective surgery.

132 Non-respiratory swabs have little role in the detection of methicillin resistant Staphylococcus aureus in cystic fibrosis

Background: Chronic methicillin resistant Staphylococcus aureus (MRSA) infection in CF is associated with faster FEV1 decline and greater mortality. Screening for infection involves swabs from both upper respiratory (nose, throat) and peripheral sites (groin, axilla), as well as sputum culture. There are no data to indicate which is superior. Methods: Microbiology results of pts attending our adult tertiary care centre who have had any positive MRSA result between 01/01/09 and 01/08/2010 were reviewed. Patients were considered continuously infected between their earliest and last MRSA culture. Results: 17pts (5%) had at least 1 MRSA isolate: 6 known chronic MRSA; 3 intermittent; 6 detected on routine outpatient sputum culture; 2 detected on ward screening. 307 microbiology samples were taken during periods of MRSA positivity: 180 (59%) were swabs (throat = 71, nose = 35, groin = 59 and axilla = 15) and 127 sputa. Of these, 70 (55%) sputa were MRSA positive. Nose swabs grew MRSA in 24%, throat 23%, groin 19% and axilla 0% cases. 28 sets of concurrent samples from 12 pts were discordant. Nose swabs were positive in 17/28 (61%) of these, throat swabs in 8/14 (57%). Peripheral swabs grew MRSA in 5/27 (19%), all also positive in nose +/− sputum. Concurrent sputa were MRSA positive in 15/23 (65%). Discussion: Upper respiratory tract swabs constitute an important tool for MRSA surveillance. Little additional information however is derived from non-respiratory swabs, and their routine use could be discontinued in units with low MRSA prevalence. In those who expectorate easily, sputum is the most effective method of detecting MRSA. There is a considerable false negative rate for all sample methods.

Methicillin-resistant Staphylococcus Aureus: Prevalence and current susceptibility pattern in Sikkim

Background:Prevalence of methicillin-resistant Staphylococcus Aureus (MRSA) strains is reported to be increasing globally.Objectives:The study was conducted to find the magnitude and antibiotic susceptibility pattern of MRSA infection in a referral tertiary care teaching hospital of Sikkim, India.Materials and Methods:In this cross sectional study, 827 clinical specimens were collected from different departments of Central Referral Hospital. One hundred and ninety-six carrier screening nasal swabs were obtained from health care workers of the hospital. Subsequently, the antimicrobial susceptibility test was performed for the confirmed MRSA isolates as per Clinical and Laboratory Standards Institute (CLSI).Results:Methicillin resistance was seen in 152 isolates of S. aureus – 111 from clinical specimens and 41 from carrier screening samples. MRSA positivity among males was significantly higher than females. Extremely significant MRSA-positive cases were observed from ages less than 30 years, in-patient cases, particularly with a stay of more than 15 days and with a previous history of intake of broad spectrum antibiotics. Incidentally, there was no significant difference of MRSA positivity with a previous history of hospitalization. The extent of MRSA and drug resistance pattern was significantly different among various samples of S. aureus-positive isolates. The strains tested exhibited decreased susceptibility to vancomycin and imipenem. Most vulnerable of the carrier were the cleaners, that was a significant observation. Incidentally, there was no resistance in the carriers to both vancomycin and imipenem.Conclusion:MRSA is prevalent in our hospital and strains resistant to methicillin and vancomycin were quite high.

Long-term persistence of MRSA in re-admitted patients

BackgroundA better knowledge of methicillin-resistant Staphylococcus aureus (MRSA) persistence in hospitalised patients may impact on specific prevention strategies. We have investigated the persistence of MRSA-carriage in patients admitted and re-admitted to a university hospital.Patients and methodsBetween January 2002 and October 2005 all MRSA-positive patients admitted to the university hospital of Hannover Medical School were assessed at first admission and all subsequent re-admissions. Patients re-admitted at least once were analysed for the persistence or loss of MRSA. The association of possible factors influencing the persistence of MRSA colonisation or infection (age group, gender, decolonisation therapy during first hospital stay due to MRSA positivity and colonisation of different anatomical sites) was analysed using univariate, multivariate and time-dependent analyses.ResultsA total of 1,032 patients who had tested positive at least once for MRSA were admitted to our hospital during the study period, accounting for 2,038 admissions. Of these patients, 403 (39.1%) were admitted more than once (from two times to 21 times), and 238 (59.1%) of the re-admitted patients remained MRSA positive during all subsequent admissions. Fifty-five (13.6%) patients tested MRSA negative at their last admission, and 61 (15.1%) tested MRSA negative at at least two consecutive admissions. In 27 (6.7%) patients, the MRSA status differed more than once between subsequent admissions. Overall, the half-life time (HLT) of MRSA persistence was 549 days, with the duration of persistence dependent on the colonisation of different anatomical sites (HLT only wounds 117 days; HLT mouth, throat, bronchial secretions 627 days; HLT nose, wounds and other body sites 801 days; p < 0.01) and was prolonged if more than one body site was MRSA-positive (HR 2.18, 95% confidence interval 1.52–3.15).ConclusionA detailed knowledge of the dynamics of the loss of MRSA infection could result in a reduction of the incidence of MRSA in the future. Multiple anatomical site carriage of MRSA appeared to predict a prolonged persistence in our cohort of patients re-admitted to a university hospital.

Carriage of methicillin-resistantStaphylococcus aureusin veterinary personnel

A survey of 280 attendees at a veterinary meeting in the Czech Republic in 2008 revealed a carriage rate of 0.7% for methicillin-resistant Staphylococcus aureus (MRSA). The two strains isolated were of distinct genetic lineages, carried type IV SCCmec determinants and were negative for Panton-Valentine leukocidin genes. The MRSA positivity rates for veterinarians in the Czech Republic is considerably lower than reported elsewhere.

Evaluation of MRSA Select, a new chromogenic medium for the detection of nasal carriage of methicillin-resistant Staphylococcus aureus

MRSA Select is a new chromogenic medium for the detection from clinical specimens of methicillin-resistant Staphylococcus aureus (MRSA) growing as pink colonies. Screening samples ( n = 666) taken from patients were spread onto MRSA Select, oxacillin resistance screening agar base (ORSAB), mannitol salt agar and an in-house medium containing tobramycin–colistin–fungizone (TCF). Ninety-nine samples were positive for MRSA on at least one selective medium. Sensitivity and specificity were >94% for all media provided that incubation was extended to 48 h for ORSAB and that a coagulase test was performed for ORSAB and TCF. By contrast, on the single criterion of the colour of colonies for MRSA positivity, the specificity and sensitivity of MRSA Select were high (99.8% and 99%, respectively).

Duration of Colonization with Methicillin-ResistantStaphylococcus aureusAmong Patients in the Intensive Care Unit: Implications for Intervention

To determine the duration of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection before entry and during hospitalization in the intensive care unit (ICU) and the characteristics of patients who tested positive for MRSA. Prospective observational cohort survey. A combined medical and coronary care ICU with 16 single-bed rooms in a 427-bed tertiary care Veteran Affairs Medical Center. A total of 720 ICU patients associated with 845 ICU admissions were followed up for the detection of MRSA from January 13, 2003, to October 12, 2003. MRSA colonization was detected in patients by using active surveillance cultures (ASCs) of nasal swab specimens obtained within 48 hours of ICU entry and 3 times weekly thereafter. The duration of colonization during ICU stay and before ICU entry was calculated after a review of surveillance culture results, clinical culture results, and medical history. Ninety-three (11.0%) of 845 ICU admissions involved patients who were colonized with MRSA at the time of ICU entry, and 21 admissions (2.5%) involved patients who acquired MRSA during ICU stay. ASCs were positive for MRSA in 84 (73.6%) of the 114 admissions associated with MRSA positivity and were the sole means of identifying MRSA in 50 cases (43.8%). More than half of the MRSA-associated admissions involved patients who were transferred from hospital wards. The total bed-days of care for 38 admissions involving patients who tested positive for MRSA before ICU entry (1131 days) was nearly 20% higher than the total bed-days of care for all admissions associated with MRSA positivity (970 days). Admissions involving MRSA-positive patients were associated with a longer length of hospitalization before ICU entry (P < .001), longer length of ICU stay (P < .001), longer overall length of hospitalization (P < .001), and greater inpatient mortality than admissions involving MRSA-negative patients (P < .001). A total of 22.8% of all bed-care days were dedicated to MRSA-positive patients in the ICU, and 55 (48.2%) of 114 admissions associated with MRSA positivity involved patients who were colonized for the duration of their ICU stay. In our unit, ASCs were an effective means to identify MRSA colonization among patients admitted to the ICU. Unfortunately, the majority of identified patients had long durations of stay in our own hospital before ICU entry, with prolonged MRSA colonization. Enhanced efforts to control MRSA will have to account for the prevalence of MRSA within hospital wards and to direct control efforts at these patients in the future.