Methicillin-Resistant Staphylococcus aureus Keratitis: Initial Treatment, Risk Factors, Clinical Features, and Treatment Outcomes

PURPOSE

To analyze the clinical characteristics, management choices, and outcomes of cases of methicillin-resistant Staphylococcus aureus (MRSA) keratitis.

DESIGN

Retrospective interventional case series.

METHODS

Fifty-two culture-proven (52 eyes) cases of MRSA keratitis diagnosed and treated at the University of Pittsburgh Medical Center were identified and reviewed.

RESULTS

The mean age was 66.6 ± 19.2 years with a median follow-up time of 147 days. The most prevalent risk factors included a history of ocular surgery (62.5%), topical corticosteroid use (35.4%), and dry eye syndrome (37.5%). There was a high burden of systemic disease (95.8%). The average presenting logarithm of minimal angle of resolution visual acuity was 1.7 ± 0.8 and the average final logarithm of minimal angle of resolution visual acuity was 1.2 + 1.0. Initial antibiotic treatment varied, with 20.8% receiving moxifloxacin alone, 20.8% receiving fortified cefazolin and fortified tobramycin together, and 12.5% receiving fortified vancomycin and fortified tobramycin, although other antibiotics were used during treatment if warranted. Surgical management was often required as 17.3% of eyes perforated: 13.5% required tarsorrhaphy, 5.8% required penetrating keratoplasty, and 1 eye was enucleated. When patients treated with fourth-generation fluoroquinolones were compared with those treated with fortified vancomycin, no difference in final visual acuity, treatment duration, or need for surgery was found.

CONCLUSION

MRSA causes fulminant keratitis often requiring surgical management with poor visual acuity outcomes. Poor ocular surface, topical corticosteroid use, previous ocular surgery, and/or a high burden of systemic disease were identified as common risk factors. Patients treated with fluoroquinolones in our study had comparable outcomes to those treated with fortified vancomycin; however, those treated with fortified vancomycin tended to have more severe ulcers at presentation.

Phenotypic and genotypic characterization of clinical Staphylococcus aureus isolates from Kenya

BACKGROUND

The increase and spread of virulent-outbreak associated, methicillin and vancomycin resistant (MRSA/VRSA) Staphylococcus aureus require a better understanding of the resistance and virulence patterns of circulating and emerging strains globally. This study sought to establish the resistance phenotype, and strains of 32 non-duplicate clinical MRSA and MSSA S. aureus isolates from four Kenyan hospitals, identify their resistance and virulence genes and determine the genetic relationships of MRSA with global strains.

METHODS

Antimicrobial susceptibility profiles were determined on a Vitek 2, genomic DNA sequenced on an Illumina Miseq and isolates typed in-silico. Resistance and virulence genes were identified using ARIBA and phylogenies generated using RAxML.

RESULTS

The MRSA isolates were 100% susceptible to vancomycin, teicoplanin, linezolid, and tigecycline. Nine distinct CC, 12 ST and 15 spa types including the novel t17826 and STs (4705, 4707) were identified with CC8 and CC152 predominating. MRSA isolates distributed across 3 CCs; CC5-ST39 (1), CC8 - ST241 (4), a novel CC8-ST4705 (1), ST8 (1) and CC152 (1). There was > 90% phenotype-genotype concordance with key resistance genes identified only among MRSA isolates: gyrA, rpoB, and parC mutations, mecA, ant (4')-lb, aph (3')-IIIa, ermA, sat-4, fusA, mphC and msrA. Kenyan MRSA isolates were genetically diverse and most closely related to Tanzanian and UK isolates. There was a significant correlation between map, hlgA, selk, selq and cap8d virulence genes and severe infections.

CONCLUSION

The findings showed a heterogeneous S. aureus population with novel strain types. Though limited by the low number of isolates, this study begins to fill gaps and expand our knowledge of S. aureus epidemiology while uncovering interesting patterns of distribution of strain types which should be further explored. Although last-line treatments are still effective, the potential for outbreaks of both virulent and resistant strains remain, requiring sustained surveillance of S. aureus populations.

Prevalence of methicillin-resistant Staphylococcus aureus carriage on admission among patients attending regional hospitals in Dar es Salaam, Tanzania

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for hospital and community acquired infection. Colonization with MRSA is associated with a high risk of developing infection. This study aimed to determine the rate of MRSA carriage on admission and the associated risk factors among patients attending regional hospitals, in Dar es Salaam, Tanzania.

Results

A total of 258 patients were included in this study. Nasal swabs were collected on admission to the hospital and after 48 h of hospital stay for detection of MRSA. Of 258 patients enrolled, 89 (34.5%) were colonized with S. aureus and out them 22 (24.7%) were carriers of MRSA, giving an overall MRSA nasal carriage rate of 8.5% (22/258). One patient acquired MRSA while admitted in the hospital. Most of the S. aureus isolates 85 (95.5%) were resistant to penicillin. Resistance to gentamycin, ciprofloxacin, kanamycin, linezolid and mupirocin were 14.6, 11.2, 11.2, 3.4 and 1.1%, respectively. The prevalence of inducible clindamycin resistance, constitutive clindamycin resistance, MS phenotype (resistance to erythromycin alone), and multidrug resistance was 21.3, 3.4, 12.4, and 16.9%, respectively. We observed a statistically significant association between MRSA and multiple drugs resistance among S. aureus isolates (p = 0.001). Of the risk factors investigated none were statistically significant associated with MRSA.

Conclusion

There is a high prevalence of MRSA among patients on admission at the two municipal hospitals in Dar es Salaam. The high prevalence of MRSA and the increased rates of resistance to commonly used antimicrobials among MRSA isolates call for attention to the importance of including the screening of MRSA in our hospitals setting in order to prevent further spread of MRSA strains to other patients and to the communities. Control and prevention strategies should be emphasized including decolonization.

Methicillin-Resistant Staphylococcus aureus Nasal Colonization in Chinese Children: A Prevalence Meta-Analysis and Review of Influencing Factors

OBJECTIVE

To determine the pooled prevalence and review the influencing factors of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization in Chinese children.

METHODS

Articles published between January 2005 and October 2015 that studied prevalence or influencing factors of MRSA nasal colonization in Chinese children were retrieved from Chinese Biomedical Literature database (CBM), China National Knowledge Infrastructure (CNKI) database, Chinese VIP database, Chinese Wanfang database, Medline database and Ovid database. Prevalence and influencing factors were analyzed by STATA 13.1.

RESULTS

Thirteen articles were included. The overall prevalence of MRSA nasal colonization was 4.4% (95% confidence interval [CI]: 0.027-0.062). With an MRSA prevalence of 3.9% (95% CI: 0.018-0.061) in healthy children and 5.8% (95% CI: 0.025-0.092) in children with underlying medical conditions. Children recruited in the hospitals presented MRSA prevalence of 6.4% (95% CI: 0.037-0.091), which was higher than those recruited in the communities [2.7% (95% CI: 0.012-0.043)]. A number of influencing factors for MRSA nasal colonization were noted in three eligible studies: gender (male vs female; OR: 0.67; 95% CI: 0.55-0.82), younger age (OR: 2.98; 95% CI: 1.31-6.96 and OR: 1.56; 95% CI: 1.21-2.00), attending day care centers (OR: 2.97; 95% CI: 1.28-6.76), having infectious diseases (OR: 2.31; 95% CI: 1.10-4.52), using antibiotics (OR: 2.77; 95% CI: 1.45-5.05), residing in northern Taiwan (OR: 1.41; 95% CI: 1.15-1.71), passive smoking (OR: 1.30; 95% CI: 1.02-1.63), and pneumococcal vaccination (OR: 1.22; 95% CI: 1.01-1.48).

CONCLUSIONS

Children could act as reservoirs of MRSA transmissions. Hospitals remained the most frequent microorganism-circulated settings. More MRSA infection control strategies are required to prevent the dissemination among children.

Epidemiology of Methicillin-ResistantStaphylococcus aureusat a University Hospital in the Canary Islands

Objectives:

To describe the epidemiology of methicillin-resistantStaphylococcus aureus(MRSA) at a university hospital in Tenerife, Canary Islands, during a 40-month period and to evaluate the effectiveness of the application of control measures.

Design:

Laboratory-based surveillance, medical charts and microbiological records review, and characterization of strains by pulsed-field gel electrophoresis (PFGE) were used to describe the epidemiology. Infection control practices were introduced as an intervention.

Setting:

A 650-bed, tertiary-care university hospital.

Subjects:

Patients with clinical and nasal isolates of MRSA and colonized staff members.

Results:

The rate of nosocomial MRSA infections was 32.5% for 1997, 17.9% for 1998, 14.5% for 1999, and 25.6% during the first 4 months of 2000. The major sites of isolation for nosocomial MRSA infection included surgical wounds (25%) and the lower respiratory tract (24%). Intensive care units and surgical specialties had more frequent MRSA cases. Characteristics associated with nosocomial MRSA isolates included prior use of intensive antibiotic therapy, prolonged hospital stays, major underlying illness, invasive procedures, and older age. PFGE type A (subtype A1) was the strain most frequently found and the only PFGE type involved in clusters.

Conclusions:

Surveillance cultures and contact droplet precautions were followed by decreased rates for 2 years. Nevertheless, the spread of PFGE subtype Al to many different areas of the hospital and the increase in incidence during the first third of 2000 indicates either that surveillance cultures were not used widely enough or that compliance with isolation measures was suboptimal.

Bacterial skin colonization and infections in patients with atopic dermatitis

Atopic Dermatitis is a chronic inflammatory skin disease that affects a large number of children and adults. The disease results from an interaction between genetic predisposition, host environment, skin barrier defects, and immunological factors. A major aggravating factor associated with Atopic Dermatitis is the presence of microorganisms on the patient's skin surface. Staphylococcus aureus and Streptococcus pyogenes, for instance, can exacerbate chronic skin inflammation. As a result, antimicrobials have often been prescribed to control the acute phase of the disease. However, increased bacterial resistance to antimicrobial agents has made it difficult for dermatologists to prescribe appropriate medication. In the presence of disseminated dermatitis with secondary infection, systemic antibiotics need to be prescribed; however, treatment should be individualized, in an attempt to find the most effective antibiotic with fewer side effects. Also, the medication should be used for as short as possible in order to minimize bacterial resistance.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Staphylococcus aureus colonization of anterior nares of school going children

OBJECTIVE

To determine the colonization rates of S. aureus in anterior nares of school going children, evaluate the antimicrobial resistance of such isolates against various antibiotics.

METHODS

Nasal swabs taken for S. aureus in 392 healthy school going children aged between 5 and 15 yr belonging to three schools surrounding Kamineni Institute of Medical Sciences, Narketpally, Andhra Pradesh, India. Swabs were inoculated in to Mannitol Salt Agar (MSA) and incubation at 37 degrees C for 24hr, Staphylococcus aureus isolates were identified by standard microbiological methods such as Gram's stain, catalase and coagulase. MICs were determined by Agar dilution technique against Vancomycin, Ciprofloxacin, Sparfloxacin, Sparfloxacin beta Cyclodextrin. Antimicrobial resistance patterns of all the isolates against Oxacillin (1 microg) Penicillin (10 units), Ampicillin (10 microg), Co-trimoxazole (23.75 microg), Erythromycin (15 microg), Tetracycline (30 microg) and Gentamicin (10 microg) were tested using Kirby-Baeur disk diffusion method in accordance with CLSI standards.

RESULTS

Of the 392 samples screened 63(16%) showed the growth of Staphylococcus aureus. 12(19%) isolates were found to be MRSA. Antimicrobial susceptibility testing using Agar dilution method against Vancomycin, ciprofloxacin, Sparfloxacin, and Sparfloxacin beta Cyclodextrin revealed MICs in the range of 0.52 microg/ml, 0.51 microg/ml, 0.5 microg/ml and <0.0312-0.250 microg/ml respectively. Disk diffusion method showed that all the isolates were resistant to Penicillin and Ampicillin. A resistance of 14.3%, 25% and 22.2% was observed against Co-trimoxazole, Erythromycin and Tetracycline respectively. Gentamiicin was the only antibiotic against which most of the isolates were sensitive.

CONCLUSION

Our results suggests that healthy school going children under 16 yr of age are potential carriers of S. aureus and in particular MRSA and multi-drug resistant strains.

Successful Treatment of Disseminated Cerebritis Complicating Methicillin-resistant Staphylococcus aureus Endocarditis Unresponsive to Vancomycin Therapy with Linezolid

A unique case of community acquired methicillin resistant Staphylococcus aureus (MRSA) sepsis, with endocardial and cerebral metastatic seeding, caused by a strain representative of the Italian clone, is described. The patient was a 47-y-old man without apparent risk factors for endocarditis and for MRSA infection who developed coma with multiple cerebritis lesions under vancomycin plus amikacin therapy. He was eventually cured with the addition of linezolid to the initial antimicrobial regimen. This observation seems to confirm previous reports of the efficacy of linezolid for the treatment of central nervous system infections caused by multidrug resistant Gram-positive bacteria. To our knowledge, this is the first report of MRSA disseminated cerebritis, a nearly always fatal disease, cured with this oxazolidinone drug. The increase in community acquired MRSA may have some impact on empirical treatment of serious infections caused by this organism.

Detection of virulence genes in Staphylococcus aureus isolated from paper currency

BACKGROUND

Infection with Staphylococcus aureus was initially considered a major problem in hospitals, but over the last few decades the incidence of community-acquired infection has also increased. Paper currency has recently been identified as another mode of spread by which community-acquired S. aureus infection may be transmitted, since paper currency is frequently transferred from one person to another. In the present study, S. aureus strains were isolated from paper currency and screened to detect virulence-associated genes.

METHODS

Paper currency was collected randomly from operators in mutton shops, vegetable shops, hospitals, medical stores, snacks corners, and restaurants in the two cities of India, Dehradun and Delhi. Samples were screened for pathogenic S. aureus by various biochemical assays. Three isolates were used to study the survival of S. aureus on paper currency. Virulence genes were amplified by PCR. Antibiotic susceptibility was determined against nine antibiotics by the disk diffusion method.

RESULTS

Sixty-seven isolates of Staphylococcus aureus were isolated from paper currency from the two Indian cities. The maximum number of isolates was recovered from hospitals, followed by mutton shops, and the minimum from restaurants. The test isolates could survive on paper currency for eight days under in vitro conditions (27 degrees C temperature and 30% relative humidity). A set of four virulence genes viz. cna (16 isolates), icaA (19 isolates), hlg (21 isolates), and sdrE (18 isolates) was amplified using gene-specific primers. Only eight isolates possessed all four virulence genes. Antimicrobial susceptibility tests showed that those isolates having all the tested virulence genes were more resistant.

CONCLUSIONS

This study clearly suggests that paper currency can serve as a carrier for the spread of resistant bacterial pathogens.

Treatment strategies for methicillin-resistant Staphylococcus aureus infections in pediatrics

Staphylococcus aureus is an important pathogen that frequently causes clinical disease in children. A wide array of illnesses can be caused by this common pathogen ranging from non-invasive skin infections to severe, life-threatening sepsis. Additionally, as antibacterials have been used to eradicate S. aureus, it has developed resistance to these important therapeutic agents. Methicillin-resistant S. aureus (MRSA) has become an increasing problem in pediatric patients over the past decade. In this review, we discuss the epidemiology, pathogenesis, and treatment options available in treating MRSA infections in children. Specifically, we address the importance of abscess drainage in the treatment of skin and soft tissue infections, the most common clinical manifestation of MRSA infections, and highlight the various agents that are available for treating this common infection. In severe, life-threatening invasive MRSA infections the primary therapeutic option is vancomycin. In cases of MRSA toxic shock syndrome the addition of clindamycin is necessary. In other invasive MRSA infections, such as pneumonia and musculoskeletal infections, the empiric treatment of choice is clindamycin. Finally, newer agents and additional treatment options are discussed.

Linezolid versus glycopeptide or beta-lactam for treatment of Gram-positive bacterial infections: meta-analysis of randomised controlled trials

Linezolid has been approved for the treatment of patients with infections caused by Gram-positive cocci that are resistant to traditionally used antibiotics, including glycopeptides. This oxazolidinone antibiotic has been reported to have excellent pharmacokinetics and effectiveness. We did a meta-analysis of randomised controlled trials (RCTs) to clarify whether linezolid is superior to glycopeptides or beta-lactams for the treatment of Gram-positive infections. 12 RCTs, involving 6093 patients, were included. Overall, with respect to treatment success, linezolid was more effective than glycopeptides or beta-lactams (odds ratio [OR] 1.41 [95% CI 1.11-1.81]). Mortality was similar between the groups (OR 0.97 [0.79-1.19]). Linezolid was more effective than comparators in patients with skin and soft-tissue infections (OR 1.67 [1.31-2.12]) and bacteraemia (OR 2.07 [1.13-3.78]). However, there was no difference in treatment success for patients with pneumonia (OR 1.03 [0.75-1.42]). Treatment with linezolid was not associated with more adverse effects in general (OR 1.40 [0.95-2.06]); however, thrombocytopenia was recorded more commonly in patients receiving linezolid (OR 11.72 [3.66-37.57]). Although linezolid is more effective than its comparators for the empirical treatment of selected patients, several points, such as the use of less potent antistaphylococcal beta-lactams, the same all-cause mortality, and the higher probability of thrombocytopenia, should be taken into account and may limit the use of linezolid to specific patient populations or infections that are difficult to treat with other antibiotics.

Financial implications of plans to combat methicillin-resistant Staphylococcus aureus (MRSA) in an orthopaedic department

INTRODUCTION

The aim of this study was to calculate retrospectively the cost of MRSA infections in the elective and trauma orthopaedic population in Rotherham District General Hospital in a 3-month period during 2005.

PATIENTS AND METHODS

A total of 686 patients were admitted to the orthopaedic wards and the surgical wounds 10 patients became infected with MRSA.

RESULTS

The cost of these infections when extrapolated over 12 months was pound384,000 excluding staff costs.

CONCLUSIONS

The key in the fight against MRSA in the hospital setting is multifactorial and requires a combination of measures. Our solution is: cohort nursing; non-selective screening of all admissions to the orthopaedic wards; use of a polymerase chain reaction as a diagnostic tool; ring-fencing of beds; and separate wound dressing rooms for each ward. The total cost is projected to be pound301,000.

Usefulness of teicoplanin for preventing methicillin-resistant Staphylococcus aureus infections in orthopedic surgery

In order to gather more data on the use of teicoplanin for reducing MRSA infections in high-risk populations, the present study was conducted. At a hospital in Barcelona, Spain, there was a high prevalence of MRSA infections among patients who underwent surgery for femoral neck fracture during the first 5 months of 2002 (period A) when cefuroxime was the antibiotic prophylaxis. During the following 12 months (period B) 600 mg of teicoplanin was added to cefuroxime. The rates of overall and MRSA infection during period A were 5.07 and 2.73%, respectively. Pulsed-field gel electrophoresis demonstrated there was no clonal relationship among MRSA strains. No nasal carriers of MRSA were detected among health workers. During period B the rates of overall and MRSA infection were 2.36 and 0.19%, respectively. Both rates were statistically significantly lower than those in period A (p<0.05). These results suggest teicoplanin may be useful in patients undergoing orthopedic surgery when the prevalence of MRSA is high.

A population-based study examining the emergence of community-associated methicillin-resistant Staphylococcus aureus USA300 in New York City

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a serious pathogen in several regions in the United States. It is unclear which populations are at high risk for the emergence of these strains.

Methods

All unique patient isolates of S. aureus were collected from hospitals in Brooklyn, NY over a three-month period. Isolates of MRSA that were susceptible to clindamycin underwent SCCmec typing. Isolates with the SCCmec type IV (characteristic of CA-MRSA strains) underwent ribotyping. Demographic information involving the neighborhoods of Brooklyn was also gathered and correlated with the prevalence of CA-MRSA strains.

Results

Of 1316 isolates collected during the surveillance, 217 were MRSA susceptible to clindamycin. A total of 125 isolates possessed SCCmec type IV; 72 belonged to the USA300 strain and five belonged to the USA400 strain. Hospitals in the eastern part of the city had the highest prevalence of USA300 strain. Individuals in the eastern region, when compared to the western region, were more likely to be Black, Hispanic, female, and < 18 years of age, and to have households of ≥ 3 persons. In addition, the median household income was lower, and the proportion of individuals on public assistance was higher, for the population in the eastern region.

Conclusion

The USA300 strain of CA-MRSA is emerging in New York City. In this population-based study, urban regions of lower socioeconomic status and with evidence of overcrowding appear to be at higher risk for the emergence of this pathogen.

Increased Prevalence of Community-Acquired Methicillin-Resistant Staphylococcus aureus in Hand Infections at an Urban Medical Center

BACKGROUND

The purpose of this article is to report the increased incidence of community-acquired methicillin-resistant S. aureus in hand infections at an urban medical center.

METHODS

The authors performed a retrospective review of all patients with hand infections over a 21-month period, and all patients with culture-positive methicillin-resistant S. aureus were identified. Cases determined to be nosocomial were excluded. The study period was divided into three 7-month periods.

RESULTS

A total of 343 hand infections were treated over a 21-month period. Eighty-nine patients (26 percent) with culture positive methicillin-resistant S. aureus were identified; of these, 75 were determined to be community-acquired methicillin-resistant S. aureus patients. Statistical analysis was performed using the Fisher's exact test (p < 0.0001), the chi-square test for equal proportions, the Cochran-Armitage trend test, and two-way analysis of variance. The demographics of the patients were compared using two-way analysis of variance, and patients were found to be similar in all three time periods with respect to mean age and sex. The incidence of community-acquired methicillin-resistant S. aureus increased to 40 percent during the last 7-month period compared with 14 percent during the first two periods. Overall, the incidence of methicillin-resistant S. aureus increased to 47 percent during the last 7 months compared with 16 percent and 17 percent in the first two 7-month periods, respectively. Based on their treatment approach and literature review, the authors have developed an algorithm to treat community-acquired methicillin-resistant S. aureus hand infections.

CONCLUSIONS

The authors' findings at Temple University Hospital may help to alert health care providers to take necessary steps to control the spread of methicillin-resistant S. aureus in the community and in the inpatient setting. Cultures should be carefully followed and infections should be treated with appropriate antibiotics.

Risk factors and molecular analysis of community methicillin-resistant Staphylococcus aureus carriage

A total of 1,838 subjects from the community and 393 subjects from health care-related facilities in Taiwan were evaluated for the prevalence of nasal Staphylococcus aureus colonization and to identify risk factors associated with S. aureus and methicillin-resistant S. aureus (MRSA) colonization. Among the community subjects, 3.5% had nasal MRSA colonization. Subjects from health care-related facilities had a lower S. aureus colonization rate (19.1%) than community subjects (25.2%) but had a significantly higher rate of colonization with MRSA (7.63%). Age (P < 0.001) was a significant risk factor for S. aureus colonization, with subjects under age 20 years or between 71 and 80 years showing higher rates of colonization. Recent gastrointestinal disease (P = 0.011) and hospital admission (P = 0.026) were risk factors for nasal MRSA colonization. Comparison of hospital MRSA isolates with the colonization strains by staphylococcal cassette chromosome mec (SCCmec) gene typing and pulsed-field gel electrophoresis (PFGE) typing revealed that most MRSA strains carried in the community were SCCmec type IV and that most clinical hospital isolates were type III, while health care facility-related carriage isolates were mainly SCCmec type III and type IV. Two new variant SCCmec types were identified. Six clusters of PFGE patterns were distinguished: two mainly comprised health care facility-related MRSA strains, three mainly comprised community MRSA strains, and one comprised mixed community and health care facility-related MRSA strains. In conclusion, a high prevalence of MRSA colonization was observed among people with no relationship to the hospital setting. The high level of multiple-drug resistance among community MRSA strains in association with the previously reported excessive use of antibiotics in Taiwan highlights the importance of the problem of antibiotic selective pressure. Our results indicate that both the clonal spread of MRSA and the transmission of hospital isolates contribute to the high MRSA burden in the community.

Emergence and spread of community-associated methicillin-resistant Staphylococcus aureus in rural Wisconsin, 1989 to 1999

We investigated the emergence and spread of community-associated strains of methicillin-resistant Staphylococcus aureus (CA-MRSA) in central and northern Wisconsin by determining the temporal and clonal relationships and geographic expansion among 581 of 956 clinical isolates of MRSA collected between 1989 and 1999. Based on EcoRI plasmid profiles (PP), two types, PP-11 and PP-13, were highly stable over time and were consistently associated with multidrug-sensitive strains recovered from outpatients treated at Native American community clinics. Pulsed-field gel electrophoresis (PFGE) yielded six major clonal groups (MCGs) and 19 minor clonal groups. The six MCGs represented 82% of the isolates. All strains with either PP-11 or -13 were present in MCG-2. Eighty-nine percent of the isolates in MCG-2 originated from Native American clinics, and 90% belonged to two PFGE types (19 and 20), the types associated with an outbreak of MRSA in a Native American community in 1992. MCG-2 isolates were multidrug sensitive, harbored type IVa staphylococcal cassette chromosome mec, and were very closely related by PFGE to the Midwestern CA-MRSA strain MW2. MCG-2 strains were mostly obtained from skin infections and affected patients with a mean age of 24 (+/-18.0) years. MCG-2 strains spread to four additional Native American communities and 20 other communities. Our findings suggest that CA-MRSA in Wisconsin likely originated in Native American communities in the early 1990s and since has become widespread throughout the state. Two early CA-MRSA strains (WI-33 and WI-34) in Wisconsin represent progenitors of the MW2 strain, based on their almost indistinguishable genotypic characteristics.

Risk factors for community-associated methicillin-resistant Staphylococcus aureus infections in an outbreak of disease among military trainees in San Diego, California, in 2002

An outbreak of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections was observed in a population of U.S. military trainees in the summer of 2002. A questionnaire was developed and administered to 206 trainees, 22 of whom had MRSA infections. Factors associated with infection were described by multivariable logistic regression modeling and included having a roommate in training with a prior skin infection (odds ratio [OR] = 3.44) or having a family member or friend who worked in a health care setting (OR = 2.79). Previous antibiotic use, hospitalization, or health problems were not associated with MRSA infection. This outbreak of MRSA skin infections in an otherwise-healthy, well-defined, military population provided an opportunity to describe risk factors for CA-MRSA which may help focus prevention efforts in this and other communities.

Bloodstream infections caused by Staphylococcus aureus in a university hospital in Turkey: clinical and molecular epidemiology of methicillin-resistant Staphylococcus aureus

In total, 177 patients with bloodstream infections caused by Staphylococcus aureus (BSISA) were investigated prospectively between June 1999 and June 2001. Of these, 19.8% had community-acquired BSISA, while 80.2% had nosocomial BSISA. Surgical intervention, foreign body, mechanical ventilation, total parenteral nutrition, and previous antibiotic treatment were found to be important risk factors for the nosocomial BSISA group. Secondary BSISA formed a greater proportion (62.9%) of community-acquired infections than of nosocomial infections (26.8%; p 0.0001). Catheter-related nosocomial BSISA was observed in 72.1% of patients. The suppurative complication rate was significantly higher among community-acquired infections (22.9%) than among nosocomial infections (6.3%; p 0.008). Of the nosocomial BSISA, 65.5% were methicillin-resistant. Analysis of 80 methicillin-resistant S. aureus isolates by pulsed-field gel electrophoresis identified ten main clones (A-J), but 61 (76.3%) of the 80 isolates belonged to clone A.

Prediction model to identify patients with Staphylococcus aureus bacteremia at risk for methicillin resistance

OBJECTIVES

To identify institution-specific risk factors for MRSA bacteremia and develop an objective mechanism to estimate the probability of methicillin resistance in a given patient with Staphylococcus aureus bacteremia (SAB).

DESIGN

A cohort study was performed to identify institution-specific risk factors for MRSA. Logistic regression was used to model the likelihood of MRSA. A stepwise approach was employed to derive a parsimonious model. The MRSA prediction tool was developed from the final model.

SETTING

A 279-bed, level 1 trauma center.

PATIENTS

Between January 1, 1999, and June 30, 2001, 494 patients with clinically significant episodes of SAB were identified.

RESULTS

The MRSA rate was 45.5%. Of 18 characteristics included in the logistic regression, the only independent features for MRSA were prior antibiotic exposure (OR, 9.2; CI95, 4.8 to 17.9), hospital onset (OR, 3.0; CI95, 1.9 to 4.9), history of hospitalization (OR, 2.5; CI95, 1.5 to 3.8), and presence of decubitus ulcers (OR, 2.5; CI95, 1.2 to 4.9). The prediction tool was derived from the final model, which was shown to accurately reflect the actual MRSA distribution in the cohort.

CONCLUSION

Through multivariate modeling techniques, we were able to identify the most important determinants of MRSA at our institution and develop a tool to predict the probability of methicillin resistance in a patient with SAB. This knowledge can be used to guide empiric antibiotic selection. In the era of antibiotic resistance, such tools are essential to prevent indiscriminate antibiotic use and preserve the longevity of current antimicrobials.

Methicillin-resistant Staphylococcus aureus: impact on dermatology practice

Methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) emerged in the 1960s and is now commonly seen in hospitals, clinics and, since the mid-1990s, the community. Risk factors for the acquisition of MRSA include chronic dermatoses, underlying medical illnesses, attending healthcare facilities, use of prescription antibacterials, surgery, intravenous lines, hospitalization in an intensive care unit, and proximity to patients colonized with MRSA. Recent community-associated strains often occur in patients without these risk factors. Staphylococci are readily spread from person to person and readily contaminate the environment. Infection control measures thus involve identifying the infected patients, separating them from other non-infected patients, cleaning of the environment and, most important of all, scrupulous attention to hand hygiene. Alcoholic antiseptic hand rubs offer an alternative to antiseptic hand washes and increase compliance. Treatment of MRSA skin infections is challenging. Topical agents such as mupirocin or fusidic acid can be used, but the organisms often become resistant. Systemic therapy involves non-beta-lactams. Parenteral treatment is generally with glycopeptides such as vancomycin; oral therapy is more complex. Monotherapy with quinolones, rifampin (rifampicin), and fusidic acid often results in the development of resistance and so, if any of these agents are chosen it should be in combination. There are no data on combination therapy, although rifampin-containing combinations are often chosen. Fourth-generation quinolones and linezolid are expensive but promising alternatives.

Smoothing a discrete hazard function for the number of patients colonized with Methicillin-resistantStaphylococcus Aureus in an intensive care unit

A new method for estimating the time to colonization of Methicillin-resistant Staphylococcus Aureus (MRSA) patients is developed in this paper. The time to colonization of MRSA is modelled using a Bayesian smoothing approach for the hazard function. There are two prior models discussed in this paper: the first difference prior and the second difference prior. The second difference prior model gives smoother estimates of the hazard functions and, when applied to data from an intensive care unit (ICU), clearly shows increasing hazard up to day 13, then a decreasing hazard. The results clearly demonstrate that the hazard is not constant and provide a useful quantification of the effect of length of stay on the risk of MRSA colonization which provides useful insight.

Cost analysis of switching from IV vancomycin to PO linezolid for the management of methicillin-resistant Staphylococcus species

BACKGROUND

Infections with methicillin-resistant Staphylococcus species (MRSS) are associated with higher treatment costs than infections with methicillin-sensitive Staphylococcus species in the United States--partly because of an increased length of hospital stay (LOS).

OBJECTIVE

This study used pharmacoeconomic modeling to evaluate the costs and outcomes associated with the use of i.v. vancomycin compared with p.o. linezolid in the treatment of MRSS-infected patients.

METHODS

A retrospective chart review was used to determine the number of cases with confirmed or presumed MRSS infections treated with i.v. vancomycin during calendar-year 2000 at the Veterans Affairs Greater Los Angeles Healthcare System inpatient facility. Patients who were eligible for a switch to p.o. linezolid with or without early discharge to home were identified. Cost differences associated with conversion from i.v. to p.o. therapy (compared with continued i.v. therapy) were estimated based on a mean decreased LOS and a decrease in the costs associated with catheter-related adverse events. Rates and costs of catheter-related adverse events were based on estimates from the literature. Sensitivity analyses were performed by variation of the estimated mean LOS decrease in the SD and by variation of the estimates for incidence and costs related to catheter complications. Costs were measured in year 2000 US dollars, and differences were not assessed for statistical significance.

RESULTS

Of 177 patients treated with i.v. vancomycin, 103 (58%) were eligible for conversion to p.o. linezolid and 55 (31%) were eligible for early discharge from the hospital with continuation of p.o. therapy. Early discharge was associated with a mean (SD) LOS decrease of 3.3 (2.9) days. Annual mean total cost savings in patients eligible for conversion from i.v. vancomycin to p.o. linezolid with early discharge were $294,750 (range, $35,730-$553,790). For cases eligible for inpatient conversion from i.v. vancomycin to p.o. linezolid therapy (n=48), the mean total annual cost difference was an increase of $6340 for p.o. linezolid (range, -$12,910 to $11,900).

CONCLUSION

These results--although partly based on estimates from the literature, rather than direct measurements--support the use of p.o. linezolid with or without early discharge as a potential cost-savings alternative for eligible patients treated with a full course of i.v. vancomycin for suspected or confirmed MRSS infection.

An outbreak of community-onset methicillin-resistant Staphylococcus aureus skin infections in southwestern Alaska

OBJECTIVE

We investigated a large outbreak of community-onset methicillin-resistant Staphylococcus aureus (MRSA) infections in southwestern Alaska to determine the extent of these infections and whether MRSA isolates were likely community acquired.

DESIGN

Retrospective cohort study.

SETTING

Rural southwestern Alaska.

PATIENTS

All patients with a history of culture-confirmed S. aureus infection from March 1, 1999, through August 10, 2000.

RESULTS

More than 80% of culture-confirmed S. aureus infections were methicillin resistant, and 84% of MRSA infections involved skin or soft tissue; invasive disease was rare. Most (77%) of the patients with MRSA skin infections had community-acquired MRSA (no hospitalization, surgery, dialysis, indwelling line or catheter, or admission to a long-term-care facility in the 12 months before infection). Patients with MRSA skin infections were more likely to have received a prescription for an antimicrobial agent in the 180 days before infection than were patients with methicillin-susceptible S. aureus skin infections.

CONCLUSIONS

Our findings indicate that the epidemiology of MRSA in rural southwestern Alaska has changed and suggest that the emergence of community-onset MRSA in this region was not related to spread of a hospital organism. Treatment guidelines were developed recommending that beta-lactam antimicrobial agents not be used as a first-line therapy for suspected S. aureus infections.

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

OBJECTIVE

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

DESIGN

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

SETTING

Tertiary-care military medical facility.

PARTICIPANTS

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

RESULTS

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

CONCLUSIONS

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

Epidemiology of methicillin-resistant Staphylococcus aureus at a children's hospital

OBJECTIVE

To describe the relative contribution of and risk factors for both community-acquired and nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections.

DESIGN

Retrospective cohort study.

SETTING

270-bed, tertiary-care children's hospital.

PARTICIPANTS

All MRSA-infected children from whom MRSA was recovered between October 1, 1999, and September 30, 2001.

METHODS

Demographic, clinical, and risk factor data were abstracted from medical records. Categorical variables were analyzed using the chi-square or Fisher's exact test and continuous variables were analyzed using the Mann-Whitney test.

RESULTS

Of the 62 patients with new MRSA infection, 37 had community-acquired MRSA and 25 had nosocomial MRSA. Most community-acquired MRSA infections were of the skin and soft tissue, the middle ear, and the lower respiratory tract. Nosocomial MRSA infections occurred in the lower respiratory tract, the skin and soft tissue, and the blood. Risk factors for infection, including underlying medical illness, prior hospitalization, and prior surgery, were similar for patients with community-acquired MRSA and nosocomial MRSA. History of central venous catheterization and previous endotracheal intubation was more common in patients with nosocomial MRSA. Only 3 patients with community-acquired MRSA had no identifiable risk factor other than recent antibiotic use. Resistance for clindamycin, erythromycin, and levofloxacin was similar between strains of community-acquired MRSA and nosocomial MRSA.

CONCLUSIONS

Similarities in patient risk factors and resistance patterns of isolates of both community-acquired and nosocomial MRSA suggest healthcare acquisition of most MRSA. Thus, classifying MRSA as either community acquired or nosocomial underestimates the amount of healthcare-associated MRSA.

Prevalence of and risk factors for colonization with methicillin-resistant Staphylococcus aureus at the time of hospital admission

OBJECTIVES

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization among patients presenting for hospital admission and to identify risk factors for MRSA colonization.

DESIGN

Surveillance cultures were performed at the time of hospital admission to identify patients colonized with S. aureus. A case-control study was performed to identify risk factors for MRSA colonization.

SETTING

A tertiary-care academic medical center.

PATIENTS

Adults presenting for hospital admission (N = 974).

RESULTS

S. aureus was isolated from 205 (21%) of the patients for whom cultures were performed. Methicillin-sensitive S. aureus was isolated from 179 (18.4%) of the patients, and MRSA was isolated from 26 (2.7%) of the patients. All 26 MRSA-colonized patients had been admitted to a healthcare facility in the preceding year, had at least one chronic illness, or both. In multivariate analyses comparing MRSA-colonized patients with control-patients, admission to a nursing home (odds ratio [OR], 16.5; 95% confidence interval [CI95], 1.4 to 192.1; P = .025) or a hospitalization of 5 days or longer during the preceding year (OR, 3.91; CI95, 1.1 to 13.9; P = .035) were independent predictors of MRSA colonization.

CONCLUSIONS

Patients colonized with MRSA admitted to this hospital likely acquired the organism during previous encounters with healthcare facilities. There was no evidence that MRSA colonization occurs commonly among low-risk individuals in this community. These data suggest that evaluation of recent healthcare exposures is essential if true community acquisition of MRSA is to be confirmed.

Rates of carriage of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in an outpatient population

OBJECTIVES

To assess the prevalence of and the clinical features associated with asymptomatic Staphylococcus aureus colonization in a healthy outpatient population, and to compare the characteristics of colonizing methicillin-resistant S. aureus (MRSA) strains with those of strains causing infection in our community and hospital.

SETTING

Outpatient military clinics.

METHODS

Specimens were obtained from the nares, pharynx, and axillae of 404 outpatients, and a questionnaire was administered to obtain demographic and risk factor information. MRSA strains were typed by pulsed-field gel electrophoresis (PFGE) and evaluated for antibiotic susceptibility. Antibiograms of study MRSA strains were compared with those of MRSA strains causing clinical illness during the same time period.

RESULTS

Methicillin-susceptible S. aureus (MSSA) colonization was present in 153 (38%) of the 404 asymptomatic outpatients, and MRSA colonization was present in 8 (2%). Detection of colonization was highest from the nares. No clinical risk factor was significantly associated with MRSA colonization; however, a tendency was noted for MRSA to be more common in men and in those who were older or who had been recently hospitalized. All colonizing MRSA strains had unique patterns on PFGE. In contrast to strains responsible for hospital infections, most colonizing isolates of MRSA were susceptible to oral antibiotics.

CONCLUSIONS

MRSA and MSSA colonization is common in our outpatient population. Colonization is best detected by nares cultures and most carriers of MRSA are without apparent predisposing risk factors for acquisition. Colonizing isolates of MRSA are heterogeneous and, unlike nosocomial isolates, often retain susceptibility to other non-beta-lactam antibiotics.

Changing epidemiology of community-onset methicillin-resistant Staphylococcus aureus bacteremia

OBJECTIVES

To review cases of community-onset Staphylococcus aureus bacteremia and to evaluate whether the risk factors and epidemiology of methicillin-resistant S. aureus (MRSA) bacteremia have changed from early reports.

DESIGN

Retrospective case-comparison study of community-onset MRSA (n = 26) and methicillin-susceptible S. aureus (MSSA) (n = 26) bacteremias at our institution.

SETTING

A 600-bed urban academic medical center.

PATIENTS

Twenty-six patients with community-onset MRSA bacteremia were compared with 26 patients with community-onset MSSA bacteremia. Molecular analysis was performed on S. aureus isolates from the 26 MRSA cases as well as from 13 cases of community-onset S. aureus bacteremia from 1980 and 9 cases of nosocomial S. aureus bacteremia from 2001.

RESULTS

The two groups were similar except that patients with MRSA bacteremia were more likely to have presented from a long-term-care facility (26.9% vs 4%; P = .05) and to have had multiple admissions within the preceding year (46% vs 15%; P = .03). Clamped homogeneous electric fields analysis of MRSA isolates from 1982 revealed predominantly that one clone was the epidemic strain, whereas there were 14 unique strains among current community-onset isolates. Among current nosocomial isolates, 3 patterns were identified, all of which were present in the community-onset cases.

CONCLUSIONS

Previously described risk factors for MRSA acquisition may not be helpful in predicting disease due to the polyclonal spread of MRSA in the community. Unlike early outbreaks of MRSA in patients presenting from the community, current acquisition appears to be polyclonal and is usually related to contact with the healthcare system.

Prevalence of and risk factors for colonization with methicillin-resistant Staphylococcus aureus in an outpatient clinic population

OBJECTIVES

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization in an outpatient population and to identify risk factors for MRSA colonization.

DESIGN

Surveillance cultures were performed during outpatient visits to identify S. aureus colonization. A case-control study was performed to identify risk factors for MRSA colonization.

SETTING

Primary care internal medicine clinic.

PATIENTS

Adults presenting for non-acute primary care (N = 494).

RESULTS

S. aureus was isolated from 122 (24.7%) of the patients for whom cultures were performed. Methicillin-susceptible S. aureus was isolated from 107 (21.7%) of the patients, whereas MRSA was isolated from 15 (3.0%) of the patients. All MRSA isolates were resistant to multiple non-beta-lactam antimicrobial agents. In multivariate analyses, MRSA colonization was independently associated with admission to a nursing home (adjusted odds ratio [OR], 103; 95% confidence interval [CI95], 7 to 999) or hospital in the previous year, although the association with hospital admission was observed only among those without chronic illness (adjusted OR, 7.1; CI95, 1.3 to 38.1). In addition, MRSA colonization was associated with the presence of at least one underlying chronic illness, although this association was observed only among those who had not been hospitalized in the previous year (adjusted OR, 5.1; CI95, 1.2 to 21.9).

CONCLUSIONS

We found a low prevalence of MRSA colonization in an adult outpatient population. MRSA carriers most likely acquired the organism through contact with healthcare facilities rather than in the community. These data show that care must be taken when attributing MRSA colonization to the community if detected in outpatients or during the first 24 to 48 hours of hospitalization.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in nursing homes: a cross-sectional study

A cross-sectional study of methicillin-resistant Staphylococcus aureus carriage in 2,857 nursing home residents showed an overall prevalence of 4.9%. The three clones identified by genetic analysis were identical to those in the acute care facilities; only their relative prevalence differed. Clone 2 took epidemic proportions in five of these nursing homes.

Community-acquired methicillin-resistant Staphylococcus aureus: a meta-analysis of prevalence and risk factors

Reports suggest that carriage of methicillin-resistant Staphylococcus aureus (MRSA) among persons without health care-associated risks has increased. A meta-analysis of studies reporting the prevalence of community-acquired MRSA (CA-MRSA) among MRSA isolates from hospitalized patients or the prevalence of MRSA colonization among community members was conducted. The CA-MRSA prevalence among hospital MRSA was 30.2% in 27 retrospective studies and 37.3% in 5 prospective studies; 85% of all patients with CA-MRSA had > or =1 health care-associated risk. The pooled MRSA colonization rate among community members was 1.3% (95% confidence interval [CI], 1.04%-1.53%), but there was significant heterogeneity among study populations. Community members from whom samples were obtained in health care facilities were more likely to be carrying MRSA than were community members from whom samples were obtained outside of the health care setting (relative risk, 2.35; 95% CI, 1.56-3.53). Among studies that excluded persons with health care contacts, the MRSA prevalence was 0.2%. Moreover, most persons with CA-MRSA had > or =1 health care-associated risk, which suggests that the prevalence of MRSA among persons without risks remains low (< or =0.24%). Effective control of dissemination of MRSA throughout the community likely will require effective control of nosocomial MRSA transmission.

Staphylococcus aureus Carriage and Health Care-acquired Infection

Staphylococcus aureus is one of the most common nosocomial pathogens. Its propensity to establish prolonged carriage among hospitalized patients and increasing resistance to antibiotics makes control of this organism within the hospital difficult. High-level vancomycin resistance has now been reported in a single clinical isolate of S. aureus, emphasizing the need to increase efforts to control nosocomial spread. Knowledge of the epidemiology of S. aureus colonization among patients has shed new light on the potential difficulties in interrupting nosocomial transmission. Effective control of S. aureus within the hospital and community will require more aggressive measures that include earlier diagnosis of colonized patients, better handwashing and barrier precaution measures, and renewed efforts to eradicate the carriage state.

Linezolid versus vancomycin for the treatment of methicillin-resistant Staphylococcus aureus infections

Linezolid, the first available member of a new antibiotic class, the oxazolidinones, is broadly active against gram-positive bacteria, including drug-resistant strains. In this randomized, open-label trial, hospitalized adults with known or suspected methicillin-resistant Staphylococcus aureus (MRSA) infections were treated with linezolid (600 mg twice daily; n=240) or vancomycin (1 g twice daily; n=220) for 7-28 days. S. aureus was isolated from 53% of patients; 93% of these isolates were MRSA. Skin and soft-tissue infection was the most common diagnosis, followed by pneumonia and urinary tract infection. At the test-of-cure visit (15-21 days after the end of therapy), among evaluable patients with MRSA, there was no statistical difference between the 2 treatment groups with respect to clinical cure rates (73.2% of patients in the linezolid group and 73.1% in the vancomycin group) or microbiological success rates (58.9% in the linezolid group and 63.2% in the vancomycin group). Both regimens were well tolerated, with similar rates of adverse events.

Prevalence of methicillin-resistant Staphyloccocus aureus and associated risk factors on admission to a specialist care eye hospital

BACKGROUND

Staphylococcus aureus is known to be a frequent pathogen in hospital settings, with its well-known and resistant forms to the anti-staphylococcal penicillins. Reports on community carriage outside hospital settings have been feared to be on the increase due to the frequency of reported cases on admission to hospitals. We undertook this study to determine the prevalence of, and to establish predictors for, nasal carriage of methicillin-resistant S. aureus (MRSA) at the time of admission to a specialist care eye hospital.

MATERIALS AND METHODS

A prospective survey was conducted at King Khaled Eye Specialist Hospital (KKESH), Riyadh, during three differing weeks randomly selected from the year 1999. The first 100 patients admitted during those three weeks were selected according to inclusion criteria. The hospital is a 220-bed tertiary ophthalmic care facility, with an average 7,500 admissions per year. Nasal bacterial swabs were taken within 48 hours of admission and tested for all strains of S. aureus and sensitivity to methicillin. Detailed interviews were conducted about medical history and habitual environment.

RESULTS

Of 306 nasal cultures tested, none was isolated for MRSA and 102 (33%) were sensitive to methicillin (MSSA). We found 0% nasal carriage rate for MRSA. Respondents had difficulty with questions related to antibiotic administration. No identifiable medical or environmental risk factors could be found.

CONCLUSION

Nasal swabs of patients admitted to KKESH did not reveal MRSA colonization, indicating that MRSA may not be prevalent in the community at present.

Methicillin-resistant Staphylococcus aureus in two tertiary-care centers in Jeddah, Saudi Arabia

OBJECTIVE

To review clinical experience with methicillin-resistant Staphylococcus aureus (MRSA) in tertiary-care hospitals in Jeddah, Saudi Arabia.

DESIGN

Retrospective review for the year 1998.

SETTING

Two tertiary-care hospitals.

METHODS

Results of MRSA-positive cultures of clinical specimens obtained as part of investigations for suspected infections were retrieved from the microbiology laboratories' records. Charts of patients were reviewed, with standardized data collection.

RESULTS

Of 673 S. aureus isolates identified, 222 (33%, or 6.8 isolates/1,000 admissions) were MRSA. Overall MRSA prevalence was 2% in 1988. Nosocomial acquisition occurred in 84.2% of cases. All age groups were affected, and 52% of patients had at least one comorbidity. MRSA prevalence was highest in the intensive care units (26.6% of all isolates), the medical wards (24.8%), and the surgical wards (19.8%). Seventy-three percent of isolates caused infection; the rest represented colonization. Surgical wounds (35.2%), the chest (29%), and central venous catheters (13%) were the most common sites of infection. Bacteremia occurred in 15.4% of patients. Local signs (84%) and fever (75.9%) were the most common clinical manifestations. Respiratory distress and septic shock occurred in 30.2% and 13.6% of cases, respectively. Of 162 patients with MRSA infection and 60 patients with MRSA colonization, 95.7% and 70% received antibiotics in the preceding 6 weeks, respectively (P<.0001). The total mortality of patients with MRSA infection was 53.7%: 36.4% as a result of MRSA infection and 17.3% as a result of other causes.

CONCLUSIONS

The prevalence of MRSA is high and rapidly increasing in the two hospitals, as it is worldwide. Control measures to prevent the spread of MRSA in hospitals should continue, with reinforcement of hygienic precautions and development of policies to restrict the use of antibiotics.

Evolving antimicrobial chemotherapy for Staphylococcus aureus infections: Our backs to the wall

Staphylococcus aureus is responsible for many nosocomial and community-acquired infections. Its evolving resistance to traditional antimicrobial chemotherapy and emerging prevalence outside of the healthcare environment are serious concerns. This review of the changing epidemiology of methicillin-resistant S. aureus, the emergence of vancomycin (glycopeptide)-resistant isolates, and the mechanisms of resistance to beta-lactams and glycopeptides provides an update for clinicians regarding effective strategies for treatment.

Community-acquired methicillin-resistant Staphylococcus aureus brain abscess in an immunocompetent individual

A 52-y-old woman with a community-acquired methicillin-resistant Staphylococcus aureus brain abscess who was successfully treated with surgical drainage and antibiotics is described. The increase in community-acquired methicillin-resistant S. aureus and the impact this will have on empirical treatment of such infections are discussed.