Control of methicillin-resistant Staphylococcus aureus in the hospital setting

In Vivo Effect of Halicin on Methicillin-Resistant Staphylococcus aureus-Infected Caenorhabditis elegans and Its Clinical Potential

Recently, the high proportion of methicillin-resistant Staphylococcus aureus infections worldwide has highlighted the urgent need for novel antibiotics to combat this crisis. The recent progress in computational techniques for use in health and medicine, especially artificial intelligence (AI), has created new and potential approaches to combat antibiotic-resistant bacteria, such as repurposing existing drugs, optimizing current agents, and designing novel compounds. Halicin was previously used as a diabetic medication, acting as a c-Jun N-terminal protein kinase (JNK) inhibitor, and has recently demonstrated unexpected antibacterial activity. Although previous efforts have highlighted halicin's potential as a promising antibiotic, evidence regarding its effectiveness against clinical strains remains limited, with insufficient proof of its clinical applicability. In this study, we sought to investigate the antibacterial activity of halicin against MRSA clinical strains to validate its clinical applicability, and a C. elegans model infected by MRSA was employed to evaluate the in vivo effect of halicin against MRSA. Our findings revealed the antibacterial activity of halicin against methicillin-resistant S. aureus clinical strains with MICs ranging from 2 to 4 µg/mL. Our study is also the first work to evaluate the in vivo effect of halicin against S. aureus using a C. elegans model, supporting its further development as an antibiotic.

Prevalence of MRSA as an Infectious Agent in Sanitary Swimming Pools and Jacuzzis

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is considered resistant to beta-lactam antibiotic groups. Infection caused by this strain is more difficult to treat with antibiotics, and hence, it will be more dangerous. This study focused on detecting the mecA gene Staphylococcus in sanitary swimming pools and Jacuzzis in Yazd city, Iran (2019). Also, the relationship between methicillin-resistant Staphylococcus aureus (MRSA) and the water quality standards has been investigated.

MATERIALS AND METHODS

60 samples were randomly collected in sterile bottles from 20 active pools and Jacuzzis. Quality parameters were analyzed by standard methods. Antibiotic resistance and the mecA gene's presence were detected by the disk diffusion and PCR method, respectively.

RESULTS

The results of this study showed that the resistance of Staphylococcus aureus isolates was high against erythromycin (41.20%), tetracycline (35.10%), clindamycin (28.90%), and cefoxitin (25.80%). Out of 97 samples, 9 (25.80%) strains of Staphylococcus aureus were identified as MRSA, 30 samples (30.92%) showed multiple patterns of antibiotic resistance, and 9 samples (9.27%) carried the mecA gene. The results revealed that water quality has greatly impacted the mecA gene strain presence, especially microbial parameters. On the other hand, in the presence of mecA gene strains, the averages of microbial qualities were higher than standard in Jacuzzis; the latter finding was confirmed for swimming pools due to physicochemical parameters.

CONCLUSION

The number of reported sanitary water is increasing, and this study's results are useful examples of these findings. Therefore, a lack of careful and regular monitoring of swimming pools and Jacuzzis can lead to MSRA prevalence and outbreak sources.

High Fecal Carriage of Multidrug Resistant Bacteria in the Community among Children in Northwestern Tanzania

Colonization of multidrug resistant (MDR) bacteria is associated with subsequent invasive infections in children with comorbidities. This study aimed to determine the resistance profile and factors associated with MDR pathogen colonization among HIV−and HIV+ children below five years of age in Mwanza, Tanzania. A total of 399 (HIV− 255 and HIV+ 144) children were enrolled and investigated for the presence of MDR bacteria. The median [IQR] age of children was 19 (10–36) months. Out of 27 Staphylococcus aureus colonizing the nasal cavity, 16 (59.5%) were methicillin resistant while 132/278 (47.2%) of Enterobacteriaceae from rectal swabs were resistant to third generation cephalosporins, with 69.7% (92/132) exhibiting extended spectrum beta lactamase (ESBL) phenotypes. The proportion of resistance to gentamicin, amoxicillin/clavulanic acid and meropenem were significantly higher among HIV+ than HIV− children. A history of antibiotic use in the last month OR 2.62 [1.1, 6.9] (p = 0.04) and history of a relative admitted from the same household in the past three months OR 3.73 [1.1, 13.2] (p = 0.03) independently predicted ESBL rectal colonization. HIV+ children had significantly more fecal carriage of isolates resistant to uncommonly used antibiotics. There is a need to strengthen antimicrobial stewardship and Infection Prevention and Control (IPC) programs to prevent the emergence and spread of MDR pathogens in children.

Detection of Methicillin Susceptible and Resistant Staphylococcus aureus Nasal Carriage and Its Antibiotic Sensitivity among Basic and Clinical Years Medical Students

Background: Healthcare workers (HCWs) and medical students can be asymptomatic carriers in transmitting methicillin resistant and susceptible Staphylococcus aureus (MRSA and MSSA). Studying epidemiological and antibiotic susceptibility data is necessary to limit the spread of infections, help with treatment and understand the transmission dynamics of MSSA and MRSA. Our study assessed the rate of MSSA and MRSA nasal carriage and its antibiogram among medical students in basic and clinical years at the University of Jordan. Methods: A total of 210 nasal swabs were randomly collected from participants. MSSA and MRSA were identified by culture, biochemical and other phenotypical analysis methods. Antibiotic susceptibility was determined by the disc diffusion method. Results: The nasal carriage of MSSA was 6.6% and 11.4% and that of MRSA was 1.9% and 2.8% among basic and clinical years, respectively. There was no significant difference for the nasal carriage of MSSA and MRSA among basic and clinical year students (p value ≥ 0.05). MSSA resistance ranged between 25% and 33% for trimethoprim-sulfamethoxazole, tetracycline and ciprofloxacin. For MRSA, the highest resistance was to trimethoprim-sulfamethoxazole and tetracycline (67% to 100%), followed by gentamicin and ciprofloxacin (33% to 67%), in all participants in the study. Conclusion: The difference in the carriage rates of MSSA and MRSA among basic and clinical students was statistically insignificant. The continuous awareness and implementation of infection control procedures and guided patient contact are recommended. The results might also suggest that healthcare workers could be victims in the cycle of MRSA nasal carriage, a theory that needs further study.

Modeling Transmission of Methicillin-ResistantStaphylococcus AureusAmong Patients Admitted to a Hospital

Objective:

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistantStaphylococcus aureus(MRSA) transmission among hospitalized patients.

Setting:

General medical ward.

Methods:

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

Results:

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Conclusion:

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)

Management of Outbreaks of Methicillin-ResistantStaphylococcus aureusInfection in the Neonatal Intensive Care Unit: A Consensus Statement

Objective.

In 2002, the Chicago Department of Public Health (CDPH; Chicago, Illinois) convened the Chicago-Area Neonatal MRSA Working Group (CANMWG) to discuss and compare approaches aimed at control of methicillin-resistantStaphylococcus aureus(MRSA) in neonatal intensive care units (NICUs). To better understand these issues on a regional level, the CDPH and the Evanston Department of Health and Human Services (EDHHS; Evanston, Illinois) began an investigation.

Design.

Survey to collect demographic, clinical, microbiologic, and epidemiologic data on individual cases and clusters of MRSA infection; an additional survey collected data on infection control practices.

Setting.

Level III NICUs at Chicago-area hospitals.

Participants.

Neonates and healthcare workers associated with the level III NICUs.

Methods.

From June 2001 through September 2002, the participating hospitals reported all clusters of MRSA infection in their respective level III NICUs to the CDPH and the EDHHS.

Results.

Thirteen clusters of MRSA infection were detected in level III NICUs, and 149 MRSA-positive infants were reported. Infection control surveys showed that hospitals took different approaches for controlling MRSA colonization and infection in NICUs.

Conclusion.

The CANMWG developed recommendations for the prevention and control of MRSA colonization and infection in the NICU and agreed that recommendations should expand to include future data generated by further studies. Continuing partnerships between hospital infection control personnel and public health professionals will be crucial in honing appropriate guidelines for effective approaches to the management and control of MRSA colonization and infection in NICUs.

Methicillin Resistant Staphylococcus aureus among HIV Infected Pediatric Patients in Northwest Ethiopia: Carriage Rates and Antibiotic Co-Resistance Profiles

Background

MRSA infections are becoming more prevalent throughout the HIV community. MRSA infections are a challenge to both physicians and patients due to limited choice of therapeutic options and increased cost of care.

Objectives

This study was aimed to determine the prevalence of colonization and co-resistance patterns of MRSA species among HIV positive pediatric patients in the Amhara National Regional State, Northwest Ethiopia.

Methods

Culture swabs were collected from the anterior nares, the skin and the perineum of 400 participants. In vitro antimicrobial susceptibility testing was done on Muller Hinton Agar by the Kirby-Bauer disk diffusion method, using 30 μg cefoxitin (OXOID, ENGLAND) according to the recommendations of the Clinical and Laboratory Standards Institute. Methicillin sensitivity/resistance was tested using cefoxitin. Data was analyzed by descriptive statistics and logistic regression model using Epi Info 7.

Results

S. aureus was detected in 206 participants (51.5%). The prevalence of MRSA colonization in this study was 16.8%. Colonization by S. aureus was associated with male gender (OR = 0.5869; 95% CI: 0.3812–0.9036; p-value = 0.0155), history of antibiotic use over the previous 3 months (OR = 2.3126; 95% CI: 1.0707–4.9948; p-value = 0.0329) and having CD₄ T-cell counts of more than 350 x 10⁶ cells / L (OR = 0.5739; 95% CI = 0.3343–0.9851; p-value = 0.0440). Colonization by MRSA was not associated with any one of the variables. Concomitant resistance of the MRSA to clindamycin, chloramphenicol, co-trimoxazole, ceftriaxone, erythromycin and tetracycline was 7.6%, 6%, 5.25%, 20.9%, 23.9% and 72.1%, respectively.

Conclusion

High rates of colonization by pathogenic MRSA strains is observed among HIV positive pediatric patients in the Amhara National Regional state.

Bacterial colonisation of the burn wound: a UK experience

OBJECTIVE

Bacterial colonisation of the burn wound remains a major source of morbidity and mortality in burns patients. This study aimed to determine the presence of different micro-organisms in a UK regional burns centre and to examine the relationships between bacterial colonisation, burn size, length of hospital stay and delayed referral.

METHOD

A retrospective review of microbiology surveillance swab results on all adult patients admitted to a regional burns centre over a 12-month period was performed.

RESULTS

139 adult patients were included in the study. Approximately 68% of patients showed evidence of burn wound colonisation at some point during their inpatient stay. The remaining 32% had negative microbiology swabs throughout their hospital stay. A total of 202 micro-organisms were isolated. Staphylococcus aureus was found to be the most common micro-organism, found in 79% of patients with positive swab results. A direct link was found between an increased incidence of bacterial colonisation and delay in referral of >24 hours, larger burn size and length of hospital stay.

CONCLUSION

By understanding the potential sources of bacteria and the effect of patient factors on their susceptibility to bacterial colonisation, we can form better management and treatment strategies to reduce morbidity and mortality from burns wound sepsis.

Facing antibiotic resistance: Staphylococcus aureus phages as a medical tool

Staphylococcus aureus is a common and often virulent pathogen in humans. This bacterium is widespread, being present on the skin and in the nose of healthy people. Staphylococcus aureus can cause infections with severe outcomes ranging from pustules to sepsis and death. The introduction of antibiotics led to a general belief that the problem of bacterial infections would be solved. Nonetheless, pathogens including staphylococci have evolved mechanisms of drug resistance. Among current attempts to address this problem, phage therapy offers a promising alternative to combat staphylococcal infections. Here, we present an overview of current knowledge on staphylococcal infections and bacteriophages able to kill Staphylococcus, including experimental studies and available data on their clinical use.

Prevalence of Methicillin Resistant Staphylococcus aureus Carriage amongst Health Care Workers of Critical Care Units in Kasturba Medical College Hospital, Mangalore, India

BACKGROUND

Outbreaks and prevalence of Methicillin resistant Staphylococcus aureus (MRSA) Nosocomial Infection (NI) among various populations have been well reported in literature, particularly those from developed countries. There is a paucity of information on carriage of MRSA in developing nations, including the carriage by critical healthcare givers who are potential transmitters.

AIM AND OBJECTIVES

Present study was aimed at establishing the carriage rate of MRSA among healthcare workers in the critical care units of Kasturba Medical College Hospital, Mangalore, India and at formulating an MRSA control policy, based on the outcomes.

MATERIAL AND METHODS

We screened 200 healthcare workers in the critical care units of the Kasturba Medical College Hospital, Mangalore, India, for MRSA and vancomycin susceptibility of the isolates. Swabs taken from both anterior nares were transported, inoculated onto mannitol salt agar (MSA) and incubated aerobically at 37°C for 18-24 hours. Gram positive cocci in clusters, with positive catalase, coagulase and DNAse tests, were identified as S.aureus. Further categorization of S.aureus into MRSA was done by using cefoxitin disc diffusion method. Sensitivity to vancomycin was tested by vancomycin disc diffusion and vancomycin agar screen plating.

RESULTS

The number of strains of S. aureus which was isolated from our 200 participants was 35, with a rate of 17.5% of the 35 isolates of S. aureus, 5 (14.3%) were MRSA. None of the S. aureus strains were vancomycin resistant.

CONCLUSION

MRSA carriage among healthcare workers who were involved in the management of critically ill patients at Kasturba Medical College hospital, Mangalore, India was 2.5%, which is comfortably low. The existing infection control policy in our hospital seems to be effective and the same should be maintained.

Infection control strategies for preventing the transmission of meticillin-resistant Staphylococcus aureus (MRSA) in nursing homes for older people

BACKGROUND

Nursing homes for older people provide an environment likely to promote the acquisition and spread of meticillin-resistant Staphylococcus aureus (MRSA), putting residents at increased risk of colonisation and infection. It is recognised that infection prevention and control strategies are important in preventing and controlling MRSA transmission.

OBJECTIVES

To determine the effects of infection prevention and control strategies for preventing the transmission of MRSA in nursing homes for older people.

SEARCH METHODS

In August 2013, for this third update, we searched the Cochrane Wounds Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), Database of Abstracts of Reviews of Effects (DARE, The Cochrane Library), Ovid MEDLINE, OVID MEDLINE (In-process and Other Non-Indexed Citations), Ovid EMBASE, EBSCO CINAHL, Web of Science and the Health Technology Assessment (HTA) website. Research in progress was sought through Current Clinical Trials, Gateway to Reseach, and HSRProj (Health Services Research Projects in Progress).

SELECTION CRITERIA

All randomised and controlled clinical trials, controlled before and after studies and interrupted time series studies of infection prevention and control interventions in nursing homes for older people were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the results of the searches. Another review author appraised identified papers and undertook data extraction which was checked by a second review author.

MAIN RESULTS

For this third update only one study was identified, therefore it was not possible to undertake a meta-analysis. A cluster randomised controlled trial in 32 nursing homes evaluated the effect of an infection control education and training programme on MRSA prevalence. The primary outcome was MRSA prevalence in residents and staff, and a change in infection control audit scores which measured adherence to infection control standards. At the end of the 12 month study, there was no change in MRSA prevalence between intervention and control sites, while mean infection control audit scores were significantly higher in the intervention homes compared with control homes.

AUTHORS' CONCLUSIONS

There is a lack of research evaluating the effects on MRSA transmission of infection prevention and control strategies in nursing homes. Rigorous studies should be conducted in nursing homes, involving residents and staff to test interventions that have been specifically designed for this unique environment.

Trends in annual incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection in HIV-infected and HIV-uninfected patients

We describe trends in incidence rates of methicillin-resistant Staphylococcus aureus (MRSA) in HIV-infected and HIV-uninfected patients enrolled in a large northern California Health Plan, and the ratio of MRSA to methicillin-susceptible S. aureus (MSSA) case counts. Between 1995 and 2010, 1549 MRSA infections were diagnosed in 14060 HIV-infected patients (11·0%) compared to 89546 MRSA infections in 6597396 HIV-uninfected patients (1·4%) (P = 0·00). A steady rise in MRSA infection rates began in 1995 in HIV-uninfected patients, peaking at 396·5 infections/100000 person-years in 2007. A more rapid rise in MRSA infection rates occurred in the HIV-infected group after 2000, peaking at 3592·8 infections/100000 in 2005. A declining trend in MRSA rates may have begun in 2008-2009. Comparing the ratio of MRSA to MSSA case counts, we observed that HIV-infected patients shouldered a greater burden of MRSA infection during most years of study follow-up compared to HIV-uninfected patients.

Length of exposure to the hospital environment is more important than antibiotic exposure in healthcare associated infections by methicillin-resistant Staphylococcus aureus: a comparative study

OBJECTIVES

Both total antimicrobial use and specific antimicrobials have been implicated as risk factors for healthcare-associated methicillin-resistant Staphylococcus aureus (HCA-MRSA) infection. The aims of this study were: (I) to explore predictors of a new HCA-MRSA infection in comparison with a new healthcare-associated methicillin-sensitive Staphylococcus aureus (HCA-MSSA); (II) to thoroughly assess the role of recent antibiotic use qualitatively and quantitatively.

METHODS

The time-period for our study was from October 1997 through September 2001. Through applying strict criteria, we identified two groups of inpatients, one with a new HCA-MRSA infection and one with a new HCA-MSSA infection. We recorded demographic, clinical and antibiotic use-related data up to 30 days before the positive culture date.

RESULTS

We identified 127 and 70 patients for each group, respectively. Two logistic regression models were carried out to assess the role of antimicrobial use (qualitatively and quantitatively). In model I, duration of hospital stay, presence of chronic wounds, aminoglycoside and fluoroquinolone use retained statistical significance. In model II, duration of hospital stay and history of intubation during the last month stood out as the only significant predictors of a subsequent HCA-MRSA infection. No significant differences in outcome were noted.

CONCLUSIONS

The length of exposure to the hospital environment may be the best predictor of a new HCA-MRSA infection. Use of aminoglycosides and fluoroquinolones may also stand independently along with presence of chronic ulcers and surgical procedures. No independent association between quantitative antibiotic use and subsequent HCA-MRSA infection was documented.

Infection control strategies for preventing the transmission of meticillin-resistant Staphylococcus aureus (MRSA) in nursing homes for older people

BACKGROUND

Nursing homes for older people provide an environment likely to promote the acquisition and spread of meticillin-resistant Staphylococcus aureus (MRSA), putting residents at increased risk of colonisation and infection. It is recognised that infection prevention and control strategies are important in preventing and controlling MRSA transmission.

OBJECTIVES

To determine the effects of infection prevention and control strategies for preventing the transmission of MRSA in nursing homes for older people.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2011, Issue 2), the Cochrane Wounds Group Specialised Register (searched May 27th, 2011). We also searched Ovid MEDLINE (from 1950 to April Week 2 2011), OVID MEDLINE (In-process and Other Non-Indexed Citations, April 26th 2011) Ovid EMBASE (1980 to 2011 Week 16), EBSCO CINAHL (1982 to April 21st 2011), DARE (1992 to 2011, week 16), Web of Science (1981 to May 2011), and the Health Technology Assessment (HTA) website (1988 to May 2011). Research in progress was sought through Current Clinical Trials (www.controlled-trials.com), Medical Research Council Research portfolio, and HSRPRoj (current USA projects).

SELECTION CRITERIA

All randomised and controlled clinical trials, controlled before and after studies and interrupted time series studies of infection prevention and control interventions in nursing homes for older people were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the results of the searches. Another review author appraised identified papers and undertook data extraction which was checked by a second review author.

MAIN RESULTS

For this second update only one study was identified, therefore it was not possible to undertake a meta-analysis. A cluster randomised controlled trial in 32 nursing homes evaluated the effect of an infection control education and training programme on MRSA prevalence. The primary outcome was MRSA prevalence in residents and staff, and a change in infection control audit scores which measured adherence to infection control standards. At the end of the 12 month study, there was no change in MRSA prevalence between intervention and control sites, while mean infection control audit scores were significantly higher in the intervention homes compared with control homes.

AUTHORS' CONCLUSIONS

There is a lack of research evaluating the effects on MRSA transmission of infection prevention and control strategies in nursing homes. Rigorous studies should be conducted in nursing homes, to test interventions that have been specifically designed for this unique environment.

Decolonization of methicillin-resistant Staphylococcus aureus during routine hospital care: Efficacy and long-term follow-up

BACKGROUND/OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) colonization is associated with a significant risk of subsequent MRSA infection in the hospital setting. The use of decolonization as an infection control strategy remains highly controversial despite publications evaluating more than 40 different decolonization regimens over the past 60 years. The present study describes the benefits and potential drawbacks of such an approach in the patient population.

METHODS

A retrospective cohort study was performed to assess the efficacy and subsequent outcome for patients with newly identified MRSA colonization at the Horizon Health Network in Moncton, New Brunswick.

RESULTS

A total of 241 patients with MRSA colonization or infection during the study period (2000 to 2005 inclusive) were identified. Eighty-nine MRSA-positive patients were decolonized according to a standardized regimen (hospital protocol group), and 98 received an alternative decolonization regimen (other treatment group). No attempt at decolonization was made for 54 patients (no treatment group). The hospital protocol group demonstrated superior overall successful decolonization compared with the other treatment group (67 of 84 [80%] versus 48 of 89 [54%]; OR 3.3; 95% CI 1.6 to 7.1; P=0.0004) and the no treatment group (four of 43 [9%]; OR 36.9; 95% CI 11.2 to 161.7; P<0.000001). The mean observed duration of culture negativity for the subgroup who remained MRSA culture negative over the long term was 419±398 days (range one to 1817 days). Successful decolonization occurred in 115 patients and permitted subsequent release from contact isolation for 4530 patient-days. The rate of clinical infection with MRSA was significantly lower in the hospital protocol group versus the other treatment group (16 of 89 [18%] versus 37 of 98 [38%]; OR 0.38; 95% CI 0.18 to 0.78; P=0.003).

CONCLUSION

The present study supports recent reports indicating that MRSA decolonization can be successful using a multifactorial approach (chlorhexidine soap, enhanced hygiene/housekeeping and combination oral/topical antimicrobial therapy) in hospitalized patients, both over the short and long term. Unlike previous studies, decolonization appeared to be effective in a relatively unselected population, including patients with lines and catheters. Inability to decolonize was most closely associated with failure to use a standardized decolonization protocol.

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario.

METHODS

Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted.

RESULTS

Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain.

CONCLUSION

The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.

Comparison of a multiplexed MassARRAY system with real-time allele-specific PCR technology for genotyping of methicillin-resistant Staphylococcus aureus

The Sequenom MassARRAY iPLEX single-nucleotide polymorphism (SNP) typing platform uses matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) coupled with single-base extension PCR for high-throughput multiplex SNP detection. In this study, we investigated the use of iPLEX MassARRAY technology for methicillin-resistant Staphylococcus aureus (MRSA) genotyping. A 16-plex MassARRAY iPLEX GOLD assay (MRSA-iPLEX) was developed that targets a set of informative SNPs and binary genes for MRSA characterization. The method was evaluated with 147 MRSA isolates, and the results were compared with those of an established SYBR Green-based real-time PCR system utilizing the same SNP-binary markers. A total of 2352 markers belonging to 44 SNP-binary profiles were analysed by both real-time PCR and MRSA-iPLEX. With real-time PCR as the reference standard, MRSA-iPLEX correctly assigned 2298 of the 2352 (97.7%) markers. Sequence variation in the MRSA-iPLEX primer targets accounted for the majority of MRSA-iPLEX erroneous results, highlighting the importance of primer target selection. MRSA-iPLEX provided optimal throughput for MRSA genotyping, and was, on a reagent basis, more cost-effective than the real-time PCR methods. The 16-plex MRSA-iPLEX is a suitable alternative to SYBR Green-based real-time PCR typing of major sequence types and clonal complexes of MRSA.

Epidemiology and virulence insights from MRSA and MSSA genome analysis

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

Epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among patients and healthcare workers in a Portuguese hospital: a pre-intervention study toward the control of MRSA

This two-year study investigated the epidemiology of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) among patients and healthcare workers (HCWs) in two wards with a high frequency of MRSA isolation, at Hospital Geral de Santo António (HGSA), Portugal. Three point-prevalence surveys per year were carried out. A case-control approach was used to identify potential risk factors associated with MRSA carriage among patients. Incidence rates and risk factors of MRSA carriage among HCWs who were negative at the baseline observation were estimated. Prevalence of MRSA carriage among 276 patients screened was 5.1%. Admission to HGSA or attendance to the Diabetic Foot Outpatient Unit (DFOU) of HGSA within the past 12 months, and previous MRSA isolation were significant risk factors for MRSA carriage. Among HCWs (n = 126), the prevalence of MRSA carriage was 4.8% and the incidence rate was 61/1000 person-years. Nurses and nurse aids were the HCW categories with the highest risk of becoming colonized with MRSA over time (p = 0.01). One HCW chronically colonized was detected. Molecular typing revealed a clonal identity for isolates recovered from patients and HCWs of the same wards, with 88.6% of isolates belonging to the EMRSA-15 (ST22-MRSA-IV) clone.

Two cases of corneal ulcer due to methicillin-resistant Staphylococcus aureus in high risk groups

Considering the popular use of antibiotic-containing eyedrops in Korea, it is important to know the emerging antibiotic-resistant strains of bacteria before treating infectious eye diseases. This is especially important in high-risk groups because of the high incidence of resistant infections and the subsequent treatment requirements. We report two cases of methicillin-resistant Staphylococcus aureus (MRSA) corneal ulcers in high-risk groups. The first case involved a patient who had keratitis after using antibiotic- and steroid-containing eyedrops to treat a corneal opacity that developed after repeated penetrating keratoplasty. The second case involved a patient who used antibiotic-containing eyedrops and a topical lubricant on a regular basis for >1 month to treat exposure keratitis due to lagophthalmos. The second patient's problems, which included a persistent superficial infiltration, developed after brain tumor surgery. Both cases showed MRSA on corneal culture, and the corneal ulcers improved in both patients after the application of vancomycin-containing eyedrops. In conclusion, MRSA infection should be considered in corneal ulcers that have a round shape, mild superficial infiltration, and slow progression, especially in high-risk groups. This report includes descriptions of the characteristic features, antibiotic sensitivities, prevention, and successful treatment with vancomycin-containing eyedrops for MRSA corneal ulcers.

Vaccination as infection control: a pilot study to determine the impact of Staphylococcus aureus vaccination on nasal carriage

BACKGROUND

There is a critical need for an effective Staphylococcus aureus vaccine for the prevention of staphylococcal disease. In this study, we investigated the impact of S. aureus conjugate vaccine comprised of capsular polysaccharides 5 and 8 (CP5, CP8) on nasal colonization with S. aureus.

METHODS

Healthy adults recruited from one academic medical center to participate in a lot consistency trial of StaphVAX (S. aureus capsular polysaccharide 5 and 8 conjugate vaccine) were assessed for S. aureus nasal colonization at two weekly points prior to vaccination and again at six weeks post-vaccination. Serum anti-capsular antibody titers to CP5 and CP8 were obtained prior to vaccination and 42 days post-vaccination and measured by ELISA.

RESULTS

Thirty of 88 enrolled subjects (34%) had S. aureus isolated from at least one of the pre-immunization cultures. Of these, 20 were termed persistent carriers due to two positive cultures one week apart; 19 of the 20 were evaluable at Day 42. Baseline anti-CP8 concentrations were higher in persistent carriers of CP8+ S. aureus; however, baseline anti-CP5 levels were not significantly higher in individuals persistently colonized with CP5+ S. aureus. Statistically significant rises in antibody concentrations were noted after vaccination. At Day 42, 14 of 19 persistent carriers remained colonized; 5 subjects did not have evidence of S. aureus colonization. Ten additional subjects were positive for S. aureus at Day 42 who were not persistently colonized at baseline. Serum antibody concentrations were not statistically different between those with persistent carriage vs. those that lost carriage or those with newly acquired carriage.

CONCLUSIONS

Immune responses to vaccine were brisk and comparable in subjects with or without persistent colonization. Despite a substantial rise in anti-CP5 and anti-CP8 antibody concentrations post-vaccination, S. aureus nasal colonization rates did not significantly change.

The role of healthcare personnel in the maintenance and spread of methicillin-resistant Staphylococcus aureus

Healthcare workers may acquire methicillin-resistant Staphylococcus aureus (MRSA) from patients, both hospital and home environments, other healthcare workers, family and public acquaintances, and pets. There is a consensus of case reports and series which now strongly support the role for MRSA-carrying healthcare personnel to serve as a reservoir and as a vehicle of spread within healthcare settings. Carriage may occur at a number of body sites and for short, intermediate, and long terms. A number of approaches have been taken to interrupt the linkage of staff-patient spread, but most emphasis has been placed on handwashing and the treatment of staff MRSA carriers. The importance of healthcare workers in transmission has been viewed with varying degrees of interest, and several logistical problems have arisen when healthcare worker screening is brought to the forefront. There is now considerable support for the screening and treatment of healthcare workers, but it is suggested that the intensity of any such approach must consider available resources, the nature of the outbreak, and the strength of epidemiological associations. The task of assessing healthcare personnel carriage in any context should be shaped with due regard to national and international guidelines, should be honed and practiced according to local needs and experience, and must be patient-oriented.

Antibacterial activity of Thai medicinal plants against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen which causes severe morbidity and mortality worldwide. Seventeen Thai medicinal plants were investigated for their activity against MRSA. Garcinia mangostana was identified as the most potent plant, and its activity was traced to the prenylated xanthone, alpha-mangostin (MIC and MBC values of 1.95 and 3.91 microg/ml, respectively).

Rapid identification of hospitalized patients at high risk for MRSA carriage

Patients who are asymptomatic carriers of methicillin-resistant Staphylococcus aureus (MRSA) are major reservoirs for transmission of MRSA to other patients. Medical personnel are usually not aware when these high-risk patients are hospitalized. We developed and tested an enterprise-wide electronic surveillance system to identify patients at high risk for MRSA carriage at hospital admission and during hospitalization. During a two-month study, nasal swabs from 153 high-risk patients were tested for MRSA carriage using polymerase chain reaction (PCR) of which 31 (20.3%) were positive compared to 12 of 293 (4.1%, p < 0.001) low-risk patients. The mean interval from admission to availability of PCR test results was 19.2 hours. Computer alerts for patients at high-risk of MRSA carriage were found to be reliable, timely and offer the potential to replace testing all patients. Previous MRSA colonization was the best predictor but other risk factors were needed to increase the sensitivity of the algorithm.

Health-care workers: source, vector, or victim of MRSA?

There is ongoing controversy about the role of health-care workers in transmission of meticillin-resistant Staphylococcus aureus (MRSA). We did a search of the literature from January, 1980, to March, 2006, to determine the likelihood of MRSA colonisation and infection in health-care workers and to assess their role in MRSA transmission. In 127 investigations, the average MRSA carriage rate among 33 318 screened health-care workers was 4.6%; 5.1% had clinical infections. Risk factors included chronic skin diseases, poor hygiene practices, and having worked in countries with endemic MRSA. Both transiently and persistently colonised health-care workers were responsible for several MRSA clusters. Transmission from personnel to patients was likely in 63 (93%) of 68 studies that undertook genotyping. MRSA eradication was achieved in 449 (88%) of 510 health-care workers. Subclinical infections and colonisation of extranasal sites were associated with persistent carriage. We discuss advantages and disadvantages of screening and eradication policies for MRSA control and give recommendations for the management of colonised health-care workers in different settings.

Infection control strategies for preventing the transmission of meticillin-resistant Staphylococcus aureus (MRSA) in nursing homes for older people

BACKGROUND

Nursing homes for older people provide an environment likely to promote the acquisition and spread of meticillin-resistant Staphylococcus aureus (MRSA), putting residents at increased risk of colonisation and infection. It is recognised that infection control strategies are important in preventing and controlling MRSA transmission.

OBJECTIVES

The objective of this review was to determine the effects of infection control strategies for preventing the transmission of MRSA in nursing homes for older people.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2007, Issue 1), the Cochrane Wounds Group Specialised Register (searched April 2007); the Infectious Diseases Group and EPOC also searched their Specialised Registers for this review (both May 2006). We also searched MEDLINE (from 1966 to March Week 3 2007), EMBASE (1980 to 2007 Week 13), CINAHL (1982 to March Week 3 2007), British Nursing Index (1985 to March 2007), DARE (1992 to March 2007), Web of Science (1981 to March 2007), and the Health Technology Assessment (HTA) database (1988 to March 2007). Research in progress was identified through the National Research Register, Current Clinical Trials (www.controlled-trials.com), Medical Research Council Register, Current Research in Britain (CRIB), and HSRPRoj (current USA projects). SIGLE was also searched in order to identify atypical material which was not accessible through more conventional sources.

SELECTION CRITERIA

All randomised and controlled clinical trials, controlled before and after studies and interrupted time series studies of infection control interventions in nursing homes for older people were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the results of the searches.

MAIN RESULTS

Since no studies met the selection criteria, neither a meta-analysis nor a narrative description of studies was possible.

AUTHORS' CONCLUSIONS

The lack of studies in this field is surprising. Nursing homes for older people provide an environment likely to promote the acquisition and spread of infection, with observational studies repeatedly reporting that being a resident of a nursing home increases the risk of MRSA colonisation. Much of the evidence for recently-issued United Kingdom guidelines for the control and prevention of MRSA in health care facilities was generated in the acute care setting. It may not be possible to transfer such strategies directly to the nursing home environment, which serves as both a healthcare setting and a resident's home. Rigorous studies should be conducted in nursing homes, to test interventions that have been specifically designed for this unique environment.

Meticillin-resistant Staphylococcus aureus control in an intensive care unit: a 10 year analysis

Data regarding the efficacy of programmes to control meticillin-resistant Staphylococcus aureus (MRSA) in intensive care units (ICUs) are limited. We performed an observational 'before-and-after' study to evaluate the search-and-destroy (S&D) strategy as compared with S&D and isolation (SDI), to control MRSA in a general ICU. S&D included active surveillance, contact precautions and treatment of carriers; in SDI, isolation or cohorting were added. Three phases were identified: period 1 (p1), 1996-1997, before the introduction of programme; period 2 (p2), 1998-2002, with S&D programme; period 3 (p3), 2003-2005, with SDI in a new ICU. During the 10 years of the study we observed 3978 patients; 667, 1995 and 1316 patients in p1, p2 and p3 respectively. The numbers of MRSA-infected patients were 19 in p1, 23 in p2, and 6 in p3. The infection rate was 3.5, 1.7 and 0.7 cases per 1000 patient-days in p1, p2 and p3, respectively; a significant reduction was observed between p1 vs p2 (P=0.024) and p2 vs p3 (P=0.048), although the latter was not confirmed by a segmented regression analysis. The proportion of ICU-acquired MRSA cases was 80%, 77% and 52% during p1, p2 and p3, respectively (P=0.0001 for trend). The proportion of S. aureus isolates resistant to meticillin was 51%, 32% and 23% during p1, p2 and p3, respectively (P<0.0001 for trend). S&D strategy was effective in significantly reducing MRSA infection, transmission rates and proportion of meticillin resistance in an ICU with endemic MRSA. SDI may further enhance S&D efficacy.

Early switch from vancomycin to oral linezolid for treatment of gram-positive heart valve endocarditis

BACKGROUND

Patients with complicated gram-positive endocarditis are usually treated with a combination of surgical procedure and long-term antibiotic therapy with intravenous vancomycin. However, oral linezolid offers the potential for an early switch from intravenous vancomycin to oral linezolid therapy.

METHODS

We conducted a retrospective study from February 2002 to August 2005 to determine the potential for early switch from intravenous vancomycin to oral linezolid in patients surgically treated for a left-sided active gram-positive endocarditis.

RESULTS

Fourteen patients were identified; average age was 52 +/- 16 years. There were 10 (85%) and 2 (15%) cases of native and prosthetic valve endocarditis, respectively. Patients were operated on 3 to 10 days after diagnosis. There were no cases of operative mortality. Mean follow-up was 20.8 +/- 7.0 months. Two (14%) patients died of noncardiac causes during follow-up. The mean intensive care unit length of stay was 3.1 +/- 2.3 days, and mean hospital length of stay was 10.5 +/- 3.4 days. No cases of recurrent endocarditis or periprosthetic leakage were observed.

CONCLUSIONS

The combination of aggressive surgical treatment and the early switch from intravenous vancomycin to oral linezolid for treatment of active gram-positive heart valve endocarditis is safe and effective, and reduces infection relapses, vancomycin use, hospital length of stay, and economic costs.

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.

Emergence and resurgence of meticillin-resistant Staphylococcus aureus as a public-health threat

Staphylococcus aureus is a gram-positive bacterium that colonises the skin and is present in the anterior nares in about 25-30% of healthy people. Dependent on its intrinsic virulence or the ability of the host to contain its opportunistic behaviour, S aureus can cause a range of diseases in man. The bacterium readily acquires resistance against all classes of antibiotics by one of two distinct mechanisms: mutation of an existing bacterial gene or horizontal transfer of a resistance gene from another bacterium. Several mobile genetic elements carrying exogenous antibiotic resistance genes might mediate resistance acquisition. Of all the resistance traits S aureus has acquired since the introduction of antimicrobial chemotherapy in the 1930s, meticillin resistance is clinically the most important, since a single genetic element confers resistance to the most commonly prescribed class of antimicrobials--the beta-lactam antibiotics, which include penicillins, cephalosporins, and carbapenems.

Performance of methicillin-resistant Staphylococcus aureus protocols in Dutch hospitals

BACKGROUND

Although numerous studies have stressed the importance of compliance with methicillin-resistant Staphylococcus aureus (MRSA) protocols with regard to cost reduction and a safer environment for health care workers and patients, an evaluation of the usability of the protocols themselves is lacking. In this study, we evaluated the usability and performance of those protocols.

METHODS

The performance of MRSA protocols was examined in 5 Dutch hospitals by means of a questionnaire (n = 63), followed by a practical test (n = 50), in a stratified random sample of 3 types of health care workers (physicians, nursing staff, and cleaning personnel). The questionnaire consisted of constructs related to exposure to risk, risk perception, knowledge of and attitude toward the protocols and safety preventive measures, self-reported behavior, and social and organizational support. The practical test consisted of "what if" scenarios that simulate the actual use of the protocol as a guideline for solving infection problems. The health care workers were asked to verbalize their thoughts and actions while using the protocol.

RESULTS

The questionnaire demonstrated adequate knowledge of and attitude toward the MRSA protocols. However, the practical test revealed that the majority of respondents had problems with the accessibility, comprehensibility, applicability, and acceptability of the protocols. Problems not only occurred because of unclear information about the preventive measures and a poor infrastructure but also because of preventive measures that conflict with principles in providing care.

CONCLUSION

The protocols do not reflect the practical needs of the health care workers. In view of the different decisions that health care workers have to take in various circumstances, it would be impracticable to use the same MRSA protocol for all hospital staff. Finally, the practical test provided more reliable results than the questionnaire.

Emergence of rifampicin resistance in methicillin-resistant Staphylococcus aureus isolated at a Turkish university hospital

Twenty-three rifampicin-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolated in three wards at a university hospital in Turkey between June, 2000, and February, 2001, were studied for their genetic relatedness using a combination of antibiogram, coagulase serotyping, coagulase gene polymorphism (coa-RFLP), and pulsed-field gel electrophoresis (PFGE). They all expressed high-level rifampicin resistance (MIC, >256 mg/L) and were resistant to gentamicin, kanamycin, amikacin, ciprofloxacin, tetracycline, and cadmium acetate and were susceptible to fusidic acid, vancomycin, trimethoprim, and mupirocin. They belonged to the same coagulase serotype (serotype IV) and had identical coa-RFLP patterns. In contrast, PFGE generated nine banding patterns designated type A, types A1-A5, B, C, and D. The most common PFGE pattern (type A) and its subtypes (types A1-A5) were seen in 20 (87%) of the 23 isolates in the three wards. The results demonstrated the acquisition of rifampicin resistance by different MRSA clones and the spread of one clone among patients in the three wards.

A systematic approach to diabetic foot infections

Foot infection is the most common reason for hospitalization and subsequent lower extremity amputation among persons with diabetes. Foot ulceration caused by diabetic neuropathy, trauma, and peripheral vascular disease can lead to a limbor life-threatening infection. The optimum treatment of these potentially devastating conditions depends on a multidisciplinary approach that addresses the related or underlying disorders and thus ensures proper wound healing and a positive outcome. In addition to antibiotic therapy, severe soft-tissue or bone infections may necessitate surgical treatment, including drainage, débridement, and vascular reconstruction. Initial (empiric) antibiotic therapy should provide coverage against staphylococci and streptococci and should be revised according culture results. Antibiotic therapy is not indicated in clinically noninfected wounds. The duration of antibiotic treatment can range from 1 week for mild infections to 6 weeks or more for residual osteomyelitis and severe deep tissue infections. Aggressive (and sometimes repeated or staged) surgical intervention and appropriate antibiotic therapy can reduce the likelihood of a major amputation and the duration of hospitalization.

[Methicillin-resistant Staphylococcus aureus. Types of resistance and clinical consequences]

The problem of methicillin-resistant Staphylococcus aureus (MRSA) is on the rise worldwide. However, significant regional differences exist with respect to incidence, types of prevalent outbreak strains and accompanying resistance patterns as well as local conditions and resources to control epidemics. Intensive care units are regularly epicenters of MRSA epidemics. Accordingly, anaesthesists, intensive care physicians and surgeons need to know the established recommendations and guidelines about early recognition and infection control of MRSA, must be familiar with principles of the antimicrobial MRSA therapy, and should adapt the principles for prevention and therapy of MRSA infections to the needs of the respective institution and situation. The result of this process has to be a rational and efficient approach to this nosocomial pathogen allowing its control under consideration of cost effectiveness.

An investigation of MRSA infection in a hospice

This study investigated the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage and infection among patients admitted to a hospice. Under the existing policy at this hospice, only patients admitted from hospital wards where MRSA is known to be present are screened for MRSA prior to transfer. Hence the investigators were keen to study patients transferred from settings other than this. One hundred and twenty patients, all either from the community or from hospital wards without known MRSA, were entered into the study ('study group') and were swabbed for MRSA on admission to the hospice. Swabbing was continued at weekly intervals until discharge or death. Of the 120 patients, seven (5.8%) were MRSA positive on admission. A further four patients who were negative on admission showed MRSA on later swabs. Another two patients developed symptomatic infections during admission that were proven to be due to MRSA, but neither of these had shown MRSA on any swabs taken during the study. During the study period, a separate group of 156 patients was swabbed routinely before transfer from hospital wards where MRSA was known to be present in accordance with hospice policy ('non-study group'). Of these patients, 11 (7.1%) were found to be colonized with MRSA but none developed associated symptomatic infection. It appears that the risk of symptomatic infection with MRSA in hospice patients is low, and the burden placed on this vulnerable group by conventional eradication regimes may be disproportionate to any benefit derived.

Risk factors for acquisition of methicillin-resistant Staphylococcus aureus (MRSA) by patients with cystic fibrosis

Methicillin-resistant Staphylococcus aureus (MRSA) is an increasing problem for patients with cystic fibrosis (CF). It has been associated with clinical deterioration in some patients with CF, creates additional infection control problems, and may affect acceptance onto transplant waiting lists. Recent attempts to eradicate the organism have met with only moderate success. An understanding of those factors which increase the risk of acquisition of MRSA by CF patients will aid the development of effective preventative strategies. We conducted a retrospective case-control study comparing a variety of risk factors for 15 MRSA-positive patients and 30 age-sex-matched MRSA-negative controls who attended the Regional Paediatric or Regional Adult Cystic Fibrosis Units in Leeds. During the year prior to initial isolation, MRSA-positive CF patients spent more days in hospital (mean 19.8 days versus 5.5 days, p=0.0003), received more treatment days of oral ciprofloxacin (43.5 days versus 13.9 days, p=0.03) more treatment days of oral/intravenous cephalosporins (42.7 days versus 15.4 days, p=0.04) and were more likely to be chronically infected with Aspergillus fumigatus (40% versus 10%, p=0.04) than the age-sex-matched MRSA-negative controls. There were no significant differences in observed clinical parameters (clinical and X-ray scores) with between the two groups. Minimising the number and length of hospital admissions and judicious use of antibiotics, particularly ciprofloxacin, should be the key components of any strategies designed to reduce the risk of MRSA acquisition by patients with CF.

Real-time in vivo bioluminescent imaging for evaluating the efficacy of antibiotics in a rat Staphylococcus aureus endocarditis model

Therapeutic options for invasive Staphylococcus aureus infections have become limited due to rising antimicrobial resistance, making relevant animal model testing of new candidate agents more crucial than ever. In the present studies, a rat model of aortic infective endocarditis (IE) caused by a bioluminescently engineered, biofilm-positive S. aureus strain was used to evaluate real-time antibiotic efficacy directly. This strain was vancomycin and cefazolin susceptible but gentamicin resistant. Bioluminescence was detected and quantified daily in antibiotic-treated and control animals with IE, using a highly sensitive in vivo imaging system (IVIS). Persistent and increasing cardiac bioluminescent signals (BLS) were observed in untreated animals. Three days of vancomycin therapy caused significant reductions in both cardiac BLS (>10-fold versus control) and S. aureus densities in cardiac vegetations (P < 0.005 versus control). However, 3 days after discontinuation of vancomycin therapy, a greater than threefold increase in cardiac BLS was observed, indicating relapsing IE (which was confirmed by quantitative culture). Cefazolin resulted in modest decreases in cardiac BLS and bacterial densities. These microbiologic and cardiac BLS differences during therapy correlated with a longer time-above-MIC for vancomycin (>12 h) than for cefazolin ( approximately 4 h). Gentamicin caused neither a reduction in cardiac S. aureus densities nor a reduction in BLS. There were significant correlations between cardiac BLS and S. aureus densities in vegetations in all treatment groups. These data suggest that bioluminescent imaging provides a substantial advance in the real-time monitoring of the efficacy of therapy of invasive S. aureus infections in live animals.

Methicillin-resistant Staphylococcus aureus and beyond: what's new in the world of the golden staph?

Methicillin-resistant Staphylococcus aureus (MRSA) continues to plague our hospitals. With the appearance of isolates that are resistant to vancomycin, now, more than ever, we must direct our efforts to controlling its development and spread. New antimicrobials have become available for treatment, but may only be a short-term answer. Our efforts towards control must be directed towards infection control measures such as improved hand hygiene with user-friendly products, such as alcohol-based hand disinfectants. Intranasal mupirocin may have a place in prevention of surgical site infection, although this role has not yet been clearly defined. Other areas where MRSA control may be effected include prudent controlled use of antibiotics, including surgical prophylaxis.

Identification and biological evaluation of grapefruit oil components as potential novel efflux pump modulators in methicillin-resistant Staphylococcus aureus bacterial strains

Methicillin-resistant Staphylococcus aureus (MRSA) and MSSA strains were treated with: (a) grapefruit oil (GFO) components, isolated by chromatography and characterised by NMR and mass spectroscopy; (b) antimicrobial agents, or (c) a combination of both to evaluate (MIC determination) intrinsic antibacterial activity and to determine whether GFO components could modulate bacterial sensitivity to the anti-bacterial agents. Preliminary data suggested that the grapefruit component 4-[[(E)-5-(3,3-dimethyl-2-oxiranyl)-3-methyl-2-pentenyl]oxy]-7H-furo[3,2-g]chromen-7-one (2) enhances the susceptibility of test MRSA strains to agents, e.g., ethidium bromide and norfloxacin, to which these micro-organisms are normally resistant.

A novel multiplex real-time PCR assay for rapid typing of major staphylococcal cassette chromosome mec elements

We describe a novel procedure for rapid typing of the staphylococcal cassette chromosome mec element, a molecular marker allowing discrimination between community- and hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) strains. Oligonucleotides targeting the recombinase genes were type specific and used to type a collection of 399 MRSA isolates recovered during patient screening at admission. This novel assay constitutes a valuable tool for evaluating the molecular epidemiology of MRSA and adjusting infection control strategies against MRSA.

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

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

Methicillin-resistant staphylococcal infections: an important consideration for orthopedic surgeons

Postoperative infections in joint prostheses and fracture-fixation devices commonly involve both MRSA and methicillin resistant coagulase-negative staphylococcus. In addition, community-acquired MRSA has also become an important consideration when infected patients are admitted to the hospital from the community. Preoperative colonization with MRSA and methicillin resistant coagulase-negative staphylococcus increases the risk of postoperative surgical site infections in orthopedic patients. Up to 5.3% of orthopedic patients are colonized with these organisms on hospital admission. Screening and decolonization of methicillin resistant staphylococci decrease the incidence of postoperative surgical site infections in the orthopedic patient. This may be particularly important in orthopedic implants given the difficulty encountered in treating infected prosthesis. Current US guidelines advocate screening for methicillin resistant staphylococci only when risk factors are present. Growing evidence suggests that screening and decolinization of all patients having elective orthopedic procedures, especially those including prosthetic implants, will decrease the incidence of postoperative infections. The infected prosthesis may be potentially salvaged if the clinical manifestations of infection have been present for < or = 10 days, the implant is stable, and the etiologic organisms are susceptible to oral antibiotics.

Use of a novel selective medium to detect methicillin-resistant Staphylococcus aureus in colonized patients of an intensive care unit

BACKGROUND

Detection of colonized patients is important for implementing control measures for methicillin-resistant Staphylococcus aureus (MRSA). Laboratory detection of MRSA carriers is increased by the use of selective screening media, helping control dissemination of such organisms.

OBJECTIVE

To evaluate three different media, including selective and nonselective media, in the detection of MRSA from clinical specimens of patients of an intensive care unit (ICU).

PATIENTS

Adult patients in the ICU of the Hospital Mãe de Deus, Porto Alegre, Brazil.

METHODS

A total of 224 specimens were obtained from the nares of patients and plated on blood agar, mannitol salt agar containing 2 microg/mL of oxacillin (MSAO), and oxacillin resistance screening agar base (ORSAB). The presence of MRSA was investigated in typical colonies growing on the three types of media. Discrepant results were resolved by detection of the mecA gene by polymerase chain reaction and the modified penicillin binding protein known as PBP2'.

RESULTS

MRSA was detected in 32 (14.3%) of 224 specimens. Blood agar, MSAO, and ORSAB detected MRSA in 17, 31, and 28 specimens, respectively. After the coagulase test, no false resistance was observed.

CONCLUSION

MSAO and ORSAB performed equivalently in the detection of MRSA of colonized patients and require a single supplementary test (coagulase) to confirm MRSA.