Community-associated methicillin-resistant Staphylococcus aureus, Minnesota, 2000-2003

A Rare Occurrence of Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia Complicated by Nasal Vestibulitis and Orbital Cellulitis: A Case Report

We report the case of left lower lobe community-acquired methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in an immunocompetent male in his 20s. His illness was complicated by the dramatic appearance of right nasal vestibulitis and right preseptal orbital cellulitis post-admission. The patient responded well to vancomycin and made a complete recovery. Community-acquired MRSA pneumonia in immunocompetent adults is a rare entity in India, and the combination with vestibulitis has not yet been reported. This hitherto unreported presentation sheds further light on the evolving pattern of MRSA infections in the community.

Community-acquired and healthcare-associated Staphylococcus aureus infections in a pediatric hospital in southern Brazil over 8 years: how common is MRSA?

Backgrounds

Both healthcare-associated and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are relevant in children. The objective of our study was to evaluate their impact in a pediatric hospital in southern Brazil.

Methods

Data from patients under 18 years of age with S. aureus infections between January 2013 and December 2020 were retrospectively analyzed. Data were collected regarding infection site, infection type (community-acquired or healthcare-associated), susceptibility to oxacillin [methicillin-susceptible S. aureus (MSSA) or MRSA] and other antimicrobials. We analyzed the evolution of the susceptibility rates for the isolates over this period.

Results

A total of 563 patients were included, among whom the prevalences of community- and hospital-acquired MRSA infections were 46.1% and 8.1%, respectively. No significant change occurred in these prevalences over the study period. In community-acquired infections, MSSA was significantly more associated with osteoarticular infections and MRSA was more associated with respiratory and intra-abdominal infections. In healthcare-associated infections, there was an association between MSSA and primary bloodstream infections and between MRSA, skin/soft tissue infections, and respiratory infections. Community-acquired MRSA were highly susceptible to trimethoprim-sulfamethoxazole (96.1%), clindamycin (88.4%), and doxycycline (99.0%).

Conclusion

Our study draws attention to the high rates of MRSA in community-acquired staphylococcal infections in this population, indicating a need to review initial protocols for severe staphylococcal infections according to local epidemiology.

Multidrug-Resistant Staphylococcus aureus Isolates in a Tertiary Care Hospital, Kingdom of Bahrain

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a ubiquitous pathogen associated with a wide spectrum of human infections. In recent decades, MRSA infections have been increasingly reported in individuals without established risk factors, infecting immunocompetent members of the community. This emergence is attributed to the production of various virulence factors, notably Panton-Valentine leukocidin (PVL).

OBJECTIVE

The aim of this study was to better understand the prevalence, antibiotic resistance profiles, and molecular characteristics of S. aureus and MRSA in a tertiary care hospital in the Kingdom of Bahrain.

MATERIALS AND METHODS

This cross-sectional study was carried out in a tertiary hospital for a one-year period, from December 2020 to December 2021. A total of 161 consecutive S. aureus isolates were collected. Antibiotic susceptibility was tested using BD Phoenix™ automated identification and susceptibility testing system. Molecular analysis was conducted via conventional PCR and conventional multiplex PCR for SCCmec typing.

RESULTS

In this study, 161 S. aureus isolates were investigated, 60% (n=97) were characterized as MRSA, of which, 12% (n=12) were healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) while 88% (n=85) were community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). No statistically significant difference (P>0.05) in antibiotic resistance trends between HA-MRSA and CA-MRSA was detected. Multidrug resistance (MDR) amounted to 19% (n=30) of all S. aureus isolates, 14% (n=9) of methicillin-susceptible Staphylococcus aureus (MSSA) isolates, and 22% (n=21) of MRSA isolates. SCCmec typing demonstrated a high prevalence of type IV (61%, n=59), followed by type V (32%, n=31), then type II (4%, n=4), and type III (3%, n=3). The PVL prevalence was 39% (n=25) in MSSA and 62% (n=60) in MRSA, 33% (n=4) in HA-MRSA, and 66% (n=56) in CA-MRSA.

CONCLUSION

This study demonstrated the emergence of PVL-producing CA-MRSA in a tertiary care hospital, as well as the detection of PVL-producing MDR strains. This development prompts serious measures to be taken in order to sustain a healthy clinical environment.

Current and emerging drug treatment strategies to tackle invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) infection: what are the challenges?

INTRODUCTION

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections represent a leading cause of purulent skin and soft tissue infections in some geographical regions. Traditionally, 'old antibiotics' such as trimethoprim-sulfamethoxazole, tetracyclines, clindamycin, chloramphenicol,vancomycin, and teicoplanin have been used to treat these infections, but these were often associated with low efficacy and excessive side effects and toxicity, especially nephrotoxicity. Along with the development of new compounds, the last decade has seen substantial improvements in the management of CA-MRSA infections.

AREAS COVERED

In this review, the authors discuss the current and emerging drug treatment strategies to tackle invasive CA-MRSA infections. Articles reported in this review were selected from through literature searches using the PubMed database.

EXPERT OPINION

The availability of new drugs showing a potent in vitro activity against CA-MRSA represents a unique opportunity to face the threat of resistance while potentially reducing toxicity. All these compounds represent promising options to enhance our antibiotic armamentarium. However, data regarding the use of these new drugs in real-life studies are limited and their best placement in therapy and in terms of optimization of medical resources and balance of cost-effectiveness requires further investigation.

Molecular Epidemiology of Community-Acquired Methicillin-Resistant Staphylococcus aureus and Clinical Characteristics of Different Sites of Infection

Purpose

Since community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized, the molecular epidemiology of CA-MRSA in China has been diverse. It is unclear whether different sites of CA-MRSA infection differ in antimicrobial resistance and clinical characteristics. The purpose of this study was to identify the molecular types, virulence factors and antimicrobial resistance of CA-MRSA strains and to analyze the clinical characteristics of different sites of CA-MRSA infection.

Methods

26 CA-MRSA strains were screened from Beijing Chao-Yang Hospital from 2014 to 2022. SCCmec type, MLST type, spa type, Panton-Valentine leukocidin (PVL), hemolysin α (Hla), phenolic soluble regulatory protein α (PSMα), toxic shock syndrome toxin-1 (TSST-1), and enterotoxin (SE) A to E were detected by PCR and gene sequencing. Antimicrobial susceptibility tests and the clinical features of CA-MRSA infection cases were collected for statistical analysis.

Results

The predominant type of CA-MRSA was ST59-t437-IV. New non-epidemic types, SCCmec VII, were also found. PVL was seen in 65.4% of CA-MRSA strains and TSST-1 was only be detected in 3.8% of CA-MRSA strain which caused poor prognosis. There were three types of infections: pneumonia (61.5%), infective endocarditis (7.7%), and skin and soft tissue infections (SSTIs) (30.8%). CA-MRSA pneumonia cases were secondary to influenza infection (37.5%). Patients with CA-MRSA-associated infective endocarditis were more likely to have underlying cardiac diseases. Patients with CA-MRSA-associated SSTIs were more likely to have a history of diabetes mellitus, and strains in this group were more susceptible to erythromycin and clindamycin.

Conclusion

ST59-t437-IV was the primary CA-MRSA type in our research and in China. We proposed that TSST-1 might be one of the indicators to predict the severity and prognosis of CA-MRSA infection. Different sites of CA-MRSA infection had difference in antibiotics susceptibility testing and underlying diseases of patients. It could provide a new perspective on treating different types of CA-MRSA infection.

Prevalence and Characterization of Methicillin-Resistant Staphylococcus aureus from Community- and Hospital-Associated Infections: A Tertiary Care Center Study

The community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become increasingly prevalent in both community and hospital settings. The aim of this study was to determine the prevalence, molecular characteristics and antibiotic resistance profiles of CA-MRSA from community- and hospital-associated infections in a tertiary care hospital in Mangalore, India. Of 520 S. aureus isolates, 362 were from inpatients (IP) and 158 were from outpatients (OP). One-hundred and thirty-two MRSA isolates obtained from 94 inpatients and 38 outpatients with complete clinical details were further analyzed. Of these, 81 (61.4%) were CA-MRSA (IP-47.9%, OP-94.7%) and 51 (38.6%) were HA-MRSA (IP-52.1%, OP-5.3%). All (100%) MRSA isolates were mecA gene positive. SCCmec typing identified SCCmec type IV (50.6%) and SCCmec type V (66.7%) in CA-MRSA, while SCCmec type I (41.2%), SCCmec type III (19.6%), SCCmec type IV (31.4%) and SCCmec type V (25.5%) were detected in HA-MRSA isolates. The Panton–Valentine Leukocidin (PVL) gene was found in 70.4% of CA-MRSA, 43.1% of HA-MRSA with SCCmec type IV and SCCmec type V, and in 7.8% of true HA-MRSA. The antibiotic resistance profiles were determined by the disc diffusion method. Resistance to cefoxitin was used to identify MRSA. A significant difference (p < 0.05) was observed between CA-MRSA and HA-MRSA with respect to resistance against cephalexin, cefotaxime, levofloxacin, linezolid and teicoplanin. CA-MRSA was predominantly resistant to ciprofloxacin (86.4%), erythromycin (66.7%), ofloxacin (49.4%), cefotaxime (44.4%), gentamicin (40.7%) and clindamycin (40.7%), while HA-MRSA showed resistance against ciprofloxacin (80.4%), erythromycin (80.1%), cefotaxime (70.6%),ofloxacin (58.8%), clindamycin (47.1%) and levofloxacin (41.2%).This study reports the prevalence of CA-MRSA in community and hospital settings and the possibility of multidrug-resistant CA-MRSA replacing HA-MRSA in hospitals. The observations from our study emphasize the need for urgent measures to manage this emerging crisis in healthcare settings.

Global Epidemiology and Evolutionary History of Staphylococcus aureus ST45

Staphylococcus aureus ST45 is a major global MRSA lineage with huge strain diversity and a high clinical impact. It is one of the most prevalent carrier lineages but also frequently causes severe invasive disease, such as bacteremia. Little is known about its evolutionary history. In this study, we used whole-genome sequencing to analyze a large collection of 451 diverse ST45 isolates from 6 continents and 26 countries. De novo-assembled genomes were used to understand genomic plasticity and to perform coalescent analyses. The ST45 population contained two distinct sublineages, which correlated with the isolates' geographical origins. One sublineage primarily consisted of European/North American isolates, while the second sublineage primarily consisted of African and Australian isolates. Bayesian analysis predicted ST45 originated in northwestern Europe about 500 years ago. Isolation time, host, and clinical symptoms did not correlate with phylogenetic groups. Our phylogenetic analyses suggest multiple acquisitions of the SCCmec element and key virulence factors throughout the evolution of the ST45 lineage.

Community-acquired pneumonia caused by methicillin-resistant Staphylococcus aureus in a Chinese adult: A case report

RATIONALE

Methicillin-resistant Staphylococcus aureus (MRSA) has been established as an important cause of severe community-acquired pneumonia (CAP) with very high mortality. Panton-Valentine leukocidin (PVL) producing MRSA has been reported to be associated with necrotizing pneumonia and worse outcome. The incidence of community-acquired MRSA (CA-MRSA) pneumonia is very low, as only a few CA-MRSA pneumonia cases were reported in the last few years. We present a case of severe CAP caused by PVL-positive MRSA with ensuing septic shock.

PATIENT CONCERNS

A 68-year-old male with no concerning medical history had developed a fever that reached 39.0°C, a productive cough that was sustained for 5 days, and hypodynamia. He was treated with azithromycin and alexipyretic in a nearby clinic for 2 days in which the symptoms were alleviated. However, 1 day later, the symptoms worsened, and he was taken to a local Chinese medicine hospital for traditional medicine treatment. However, his clinical condition deteriorated rapidly, and he then developed dyspnea and hemoptysis.

DIAGNOSIS

CA-MRSA pneumonia and septic shock. The sputum culture showed MRSA. Polymerase chain reaction of MRSA isolates was positive for PVL genes.

INTERVENTIONS

Mechanical ventilation, fluid resuscitation, and antibiotic therapy were performed. Antibiotic therapy included mezlocillin sodium/sulbactam sodium, linezolid, and oseltamivir.

OUTCOMES

He died after 12 hours of treatment.

LESSONS

This is a report of severe pneumonia due to PVL-positive CA-MRSA in a healthy adult. CA-MRSA should be considered a pathogen of severe CAP, especially when combined with septic shock in previously healthy individuals.

Molecular epidemiology and virulence factors of methicillin-resistant Staphylococcus aureus isolated from patients with bacteremia

BACKGROUND

The various virulence factors of methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) are associated with a high mortality rate worldwide. Further studies are warranted to confirm the significant relationship between the strains and virulence genes. Here, we prospectively investigated the molecular characteristics underlying the genotypes and virulence factors of MRSA isolated from patients with bacteremia.

METHODS

We collected 59 MRSA isolates from adult patients with bacteremia. Antimicrobial susceptibility results were obtained with the Vitek2 automated system. Genotypes were identified with multi-locus sequence typing (MLST) and pulse-field gel electrophoresis (PFGE), and 21 virulence genes were detected with polymerase chain reaction (PCR).

RESULTS

The 59 MRSA isolates mainly comprised ST5 (n = 31, 52.5%) and ST72 (n = 22, 37.2%). Most ST5 isolates and all ST72 isolates were clustered into one and two PFGE groups, respectively. The mean number of virulence genes was higher in ST5 than in ST72. Sel was more frequently detected in ST5 than in ST72, whereas sec and sed were found only in ST5. ST5 had significantly higher resistance against many antibiotics than ST72.

CONCLUSION

Most MRSA isolates causing bacteremia were ST5 (CC5) and ST72 (CC8), and those belonging to the same STs were divided into only a few PFGE groups. ST5 was associated with higher antibiotic resistance and staphylococcal superantigen toxin genes, than ST72, which may be related to its higher virulence.

Higher Risk for All-cause Mortality of Staphylococcus aureus Bacteremia in Patients with Non-Dialysis Dependent Chronic Kidney Disease

Background

Staphylococcus aureus bacteremia (SAB) is a common and serious infection with a high mortality. Patients with chronic kidney disease (CKD) are vulnerable to SAB, but there have been few studies performed on the clinical characteristics and outcomes of SAB in CKD patients stratified by dialysis. We aimed to estimate the all-cause mortality and identify its predictors in patients with CKD.

Materials and Methods

We conducted a retrospective study on the patients with SAB hospitalized in a tertiary care center in Korea between March 2014 and December 2018. Kaplan-Meier analysis was performed to compare all-cause mortality following SAB among patients with non-dialysis dependent CKD (ND-CKD), those receiving dialysis, and those without CKD (non-CKD). The predictors of mortality among CKD patients were analyzed by Cox proportional hazards regression.

Results

As a total, 278 SAB of 43 ND-CKD (31 males), 58 dialysis (39 males), and 177 non-CKD (112 males) patients were included. The 30-day mortality was 39.5% in ND-CKD, 27.6% in dialysis, and 7.9% in non-CKD patients. The hazard ratio of all-cause mortality following SAB in ND-CKD was 2.335 (95% confidence interval, 1.203 – 4.531; P = 0.003), compared to non-CKD patients. For methicillin-resistant S. aureus bacteremia (MRSAB), the hazard ratio of all-cause mortality in ND-CKD was 2.628 (95% CI, 1.074 – 6.435; P = 0.011), compared to dialysis patients. Appropriate antibiotics <48 h was independently related to improved survival following SAB among ND-CKD (adjusted HR, 0.304; 95% CI, 0,108 – 0.857; P = 0.024) and dialysis (adjusted HR, 0.323; 95% CI, 0,116 – 0.897; P = 0.030) patients.

Conclusion

ND-CKD patients demonstrated poor outcome following SAB and administration of appropriate antibiotics within 48 h could reduce the risk for mortality.

Clinical and Molecular Characterization of Panton-Valentine Leukocidin-Positive Invasive Staphylococcus aureus Infections in Korea

AIM

Panton-Valentine leukocidin (PVL) is a virulent cytotoxin and an indicator of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection. In this study, we evaluated the prevalence and clinical and molecular characteristics of PVL-positive invasive S. aureus (ISA) infections in Korea.

RESULTS

A collection of 1,962 nonduplicate clinical isolates were screened for multilocus sequence typing, staphylococcal cassette chromosome mec (SCCmec), accessory gene regulator typing, major toxins, and antimicrobial susceptibility. Twenty-eight (1.4%) PVL-positive S. aureus samples were found; of them 19 (67.9%) were MRSA (8 CA and 11 healthcare-associated infections). Seventeen patients (60.7%) were men (median age: 63 years; range: 13-93 years) and 12 patients (42.9%) had no underlying comorbidities. The most common infections were skin and skin structure infection (SSSI) and pneumonia. The 30-day mortality rate was 37.0%. The most common PVL-positive MRSA clones were ST8-SCCmec IVa and ST30-SCCmec IVc along with their single-locus variants. Antimicrobial susceptibility and toxin-gene profile differed according to the clone.

CONCLUSIONS

ISA infections caused by PVL-positive strains are rare in Korea, with the two most common infections being SSSI and pneumonia. Our findings indicated that several PVL-positive MRSA clones, predominantly ST8-SCCmecIVa and ST30-SCCmecIVc, were circulating and causing sporadic cases of ISA infections in the community and hospital settings.

Metabolic niche adaptation of community- and hospital-associated methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) originally emerged in nosocomial settings and has subsequently spread into the community. In turn, community-associated (CA) MRSA lineages are nowadays introduced from the community into hospitals where they can cause hospital-associated (HA) infections. This raises the question of how the CA-MRSA lineages adapt to the hospital environment. Previous studies implicated particular virulence factors in the CA-behaviour of MRSA. However, we hypothesized that physiological changes may also impact staphylococcal epidemiology. With the aim to identify potential metabolic adaptations, we comparatively profiled the cytosolic proteomes of CA- and HA-isolates from the USA300 lineage that was originally identified as CA-MRSA. Interestingly, enzymes for gluconeogenesis, the tricarboxylic acid cycle and biosynthesis of amino acids are up-regulated in the investigated CA-MRSA isolates, while enzymes for glycolysis and the pentose phosphate pathway are up-regulated in the HA-MRSA isolates. Of note, these data apparently match with the clinical presentation of each group. These observations spark interest in central carbon metabolism as a key driver for adaptations that streamline MRSA for propagation in the community or the hospital.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Evaluation of Methicillin-Resistance Rates among Community-associated Staphylococcus aureus Infections in Korean Military Personnel

To evaluate methicillin-resistance (MR) rates among community-associated (CA) Staphylococcus aureus infections in the Korean military, we screened electronic medical records of 223 patients with S. aureus infection in a military referral hospital from 2012 to 2017. During the study period, MR rates did not change annually, and were not different between officers and conscripted personnel. Among conscripted personnel, MR rates in CA S. aureus infections did not increase with longer duration of military service, both in trend analysis and multivariate analysis. In conclusion, MR rates among CA S. aureus infections did not increase during military service in Korea.

Characteristics of cefazolin inoculum effect-positive methicillin-susceptible staphylococcus aureus infection in a multicentre bacteraemia cohort

Cefazolin treatment failure has been observed in high-inoculum infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) with a cefazolin inoculum effect (CIE). However, data on the characteristics and risk factors for the acquisition of CIE-positive MSSA infection are scarce. CIE positivity was measured as an MIC ≥ 16 μg/ml with a high inoculum (∼5 × 10⁷ CFU/ml). The blaZ gene type was assessed through sequence analysis. The clinical characteristics and risk factors for the acquisition of CIE-positive MSSA infection were assessed. The association between the antimicrobial susceptibility profile and CIE positivity was evaluated. A total of 303 MSSA bacteraemia cases and their corresponding isolates were collected from ten hospitals: 61 (20.1 %) isolates showed a positive CIE; 254 (83.8 %) were positive for the blaZ gene. No significant association was found between CIE positivity and the site of infection. Metastatic cancer (aOR 2.86, 95 % CI, 1.10-7.48) and recent (≤1 month) close contact with a chronically ill patient (aOR 4.69, 95 % CI, 1.76-12.50) were identified as significant risk factors for CIE-positive MSSA infection through multivariate analyses. Resistances to clindamycin (OR 3.55, 95 % CI, 1.62-7.80) and erythromycin (OR 5.00, 95 % CI, 2.50-9.99) were associated with CIE positivity, presenting high specificity (92.9 %) and a negative predictive value (82.3 %). CIE-positive MSSA constituted approximately one-fifth of MSSA bacteraemia cases. Although CIE positivity was not clinically discernible, CIE positivity was associated with clindamycin or erythromycin susceptibility. Therefore, our findings suggest that cefazolin can be used in the treatment of high-inoculum MSSA infection if the isolates are susceptible to clindamycin or erythromycin.

Methicillin-resistant Staphylococcus aureus isolates with SCCmec type V and spa types t437 or t1081 associated to discordant susceptibility results between oxacillin and cefoxitin, Central Taiwan

Staphylococcus aureus isolates with discordant susceptibility results between oxacillin and cefoxitin obtained using automated microbiology systems are infrequently observed. From April 2013 to December 2014, 1956 methicillin-resistant S. aureus (MRSA) and 1761 methicillin-susceptible S. aureus isolates were obtained from different patients. Forty isolates (1.1% and 2% in case of S. aureus and MRSA, respectively) with discordant susceptibility results (oxacillin susceptible and cefoxitin resistant) and carrying mecA gene were obtained. Except 2 SCCmec type IV isolates, 38 MRSA isolates were all SCCmec type V (V_T or non-V_T), which were further divided into V_T (n=22) and non-V_T (n=16). The most common spa type in V_T and non-V_T isolates were t437 (n=19) and t1081 (n=13), respectively. Only 55% of patients received effective antimicrobial agents; 2 mortalities were not attributable to MRSA infection. Using standard agar dilution, 17 MRSA isolates (0.46% and 0.87% in case of S. aureus and MRSA, respectively) had oxacillin MIC in the susceptible ranges (oxacillin-susceptible MRSA [OS-MRSA]); all carried SCCmec type V (V_T, n=8; non-V_T, n=9). The most common spa-MLST types of OS-MRSA in V_T and non-V_T were t437-ST59 (n=4) and t1081-ST45 (n=7), respectively. Concomitant testing by both cefoxitin- and oxacillin-based methods is a practical strategy for OS-MRSA detection in the clinical laboratories. Continuous monitoring of OS-MRSA isolates is necessary to elucidate their impact in clinical infectious diseases.

Molecular Characterization of Community- and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Isolates in Southern Taiwan

A growing tendency for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) to be involved in nosocomial infections was reported. The predominance of SCCmec type IV or V CA-MRSA in soft tissue infection has also been indicated in Northern Taiwan. To establish basic information about the molecular characteristics of MRSA in our region, a total of 102 MRSA isolates were collected and characterized by an array of typing methods. Healthcare-associated MRSA (HA-MRSA) were found to be more resistant to levofloxacin (p=0.016) and moxifloxacin (p=0.015) than CA-MRSA. However, no difference was found in each and overall SCCmec type distribution between the two MRSA groups. Type I (8.7% vs. 2.6%) was more frequently found in CA-MRSA, whereas type V was more often observed in HA-MRSA (24.4% vs. 8.7%). No difference was found in the dichotomous group of PVL, SCCmec type IV, V, and IV/V between the two MRSA groups. Twenty-seven distinct spa types were identified; t437 and t1081 were the predominant types in our isolates. Moreover, 12 novel spa types with extremely low global frequency were detected in our isolates. SCCmec type III and IV were the major subtypes in the MRSA we collected. The t1081 clones all belonged to HA-MRSA and mostly to SCCmec type V (71.4%). CA-MRSA t437 clones were mostly SCCmec type IV strains (71.4%), but HA-MRSA t437 clones were predominantly SCCmec type IV (42.1%) and III (36.8%). Our findings support a difference in the molecular characteristics of CA-MRSA and HA-MRSA that may reflect various clonal origins in our isolates.

Chlorhexidine-Impregnated Cloths to Prevent Skin and Soft-Tissue Infection in Marine Recruits: A Cluster-Randomized, Double-Blind, Controlled Effectiveness Trial

Background.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) causes skin and soft-tissue infection (SSTI) in military recruits.

Objective.

To evaluate the effectiveness of 2% Chlorhexidine gluconate (CHG)-impregnated cloths in reducing rates of SSTI and S. aureus colonization among military recruits.

Design.

A cluster-randomized (by platoon), double-blind, controlled effectiveness trial.

Setting.

Marine Officer Candidate School, Quantico, Virginia, 2007.

Participants.

Military recruits.

Intervention.

Application of CHG-impregnated or control (Comfort Bath; Sage) cloths applied over entire body thrice weekly.

Measurements.

Recruits were monitored daily for SSTI. Baseline and serial nasal and/or axillary swabs were collected to assess S. aureus colonization.

Results.

Of 1,562 subjects enrolled, 781 (from 23 platoons) underwent CHG-impregnated cloth application and 781 (from 21 platoons) underwent control cloth application. The rate of compliance (defined as application of 50% or more of wipes) at 2 weeks was similar (CHG group, 63%; control group, 67%) and decreased over the 6-week period. The mean 6-week SSTI rate in the CHG-impregnated cloth group was 0.094, compared with 0.071 in the control group (analysis of variance model rate difference, 0.025 ± 0.016; P = .14). At baseline, 43% of subjects were colonized with methicillin-susceptible S. aureus (MSSA), and 2.1% were colonized with MRSA. The mean incidence of colonization with MSSA was 50% and 61% (P = .026) and with MRSA was 2.6% and 6.0% (P = .034) for the CHG-impregnated and control cloth groups, respectively.

Conclusions.

CHG-impregnated cloths applied thrice weekly did not reduce rates of SSTI among recruits. S. aureus colonization rates increased in both groups but to a lesser extent in those assigned to the CHG-impregnated cloth Intervention. Antecedent S. aureus colonization was not a risk factor for SSTI. Additional studies are needed to identify effective measures for preventing SSTI among military recruits.

Clinical Trials Registration.

ClinicalTrials.gov identifier: NCT00475930.

Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among skin and soft tissue infections in an emergency department in Guyana

OBJECTIVE

The characteristics of staphylococcal skin and soft tissue infections (SSTIs) are poorly understood in northern South America and the Caribbean. The objectives of this study were to determine the frequency of methicillin resistance among Staphylococcus aureus isolates in an emergency department (ED) in Guyana and to identify specific molecular characteristics of these methicillin-resistant Staphylococcus aureus (MRSA) strains.

METHODS

This was a cross-sectional study conducted at the main teaching hospital in Georgetown, Guyana. Eligible subjects included patients of all ages with SSTIs with obtainable purulent material. Purulent material was cultured, and S. aureus isolates were evaluated for antibiotic susceptibilities by disc diffusion. Molecular characterisation of MRSA isolates included identification of SCCmec type, assignment of genetic relatedness by rep-PCR and determination of the presence of two exotoxins, Panton-Valentine Leukocidin (PVL) and LukAB.

RESULTS

Eighty-five samples were collected; of these, 47 grew S. aureus. 24 of the 47 S. aureus samples were MRSA (51%; 95% CI 37% to 65%), representing 28% of all samples. All MRSA isolates were SCCmec type IV, PVL positive, LukAB positive and were highly related to the current epidemic clone in the USA, USA300.

CONCLUSIONS

Here, we demonstrate a clinically significant proportion of methicillin resistance in SSTI-associated staphylococcal isolates. Guyanese isolates were highly related to the most common community-associated strain seen in the USA, USA300. These results have important implications for empiric antibiotic therapy and infection control policies in Guyana and similar settings.

Clinical and epidemiological factors associated with methicillin resistance in community-onset invasive Staphylococcus aureus infections: prospective multicenter cross-sectional study in Korea

Successful empirical therapy of Staphylococcus aureus infections requires the ability to predict methicillin resistance. Our aim was to identify predictors of methicillin resistance in community-onset (CO) invasive S. aureus infections. Sixteen hospitals across Korea participated in this study from May to December 2012. We prospectively included cases of S. aureus infection in which S. aureus was isolated from sterile clinical specimens ≤72 hours after hospitalization. Clinical and epidemiological data were gathered and compared in methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) cases. Community-associated (CA) infections were defined as in previous studies. In total, there were 786 cases of community-onset S. aureus infection, 102 (13.0%) of which were CA-MRSA. In addition to known risk factors, exposure to 3rd generation cephalosporins in the past 6 months [odds ratio (OR), 1.922; 95% confidence interval (CI), 1.176–3.142] and close contact with chronically ill patients in the past month (OR, 2.647; 95% CI, 1.189–5.891) were independent risk factors for MRSA infection. However, no clinical predictors of CA-MRSA were identified. Methicillin resistance, CO infection, and appropriateness of empirical antibiotics were not significantly related to 30-day mortality. MRSA infection should be suspected in patients recently exposed to 3rd generation cephalosporins or chronically-ill patients. There were no reliable predictors of CA-MRSA infection, and mortality was not affected by methicillin resistance.

Implementation of a novel in vitro model of infection of reconstituted human epithelium for expression of virulence genes in methicillin-resistant Staphylococcus aureus strains isolated from catheter-related infections in Mexico

Background

Methicillin-resistant Staphylococcus aureus (MRSA) are clinically relevant pathogens that cause severe catheter-related nosocomial infections driven by several virulence factors.

Methods

We implemented a novel model of infection in vitro of reconstituted human epithelium (RHE) to analyze the expression patterns of virulence genes in 21 MRSA strains isolated from catheter-related infections in Mexican patients undergoing haemodialysis. We also determined the phenotypic and genotypic co-occurrence of antibiotic- and disinfectant-resistance traits in the S. aureus strains, which were also analysed by pulsed-field-gel electrophoresis (PFGE).

Results

In this study, MRSA strains isolated from haemodialysis catheter-related infections expressed virulence markers that mediate adhesion to, and invasion of, RHE. The most frequent pattern of expression (present in 47.6% of the strains) was as follows: fnbA, fnbB, spa, clfA, clfB, cna, bbp, ebps, eap, sdrC, sdrD, sdrE, efb, icaA, and agr. Seventy-one percent of the strains harboured the antibiotic- and disinfectant-resistance genes ermA, ermB, tet(M), tet(K), blaZ, qacA, qacB, and qacC. PFGE of the isolated MRSA revealed three identical strains and two pairs of identical strains. The strains with identical PFGE patterns showed the same phenotypes and genotypes, including the same spa type (t895), suggesting hospital personnel manipulating the haemodialysis equipment could be the source of catheter contamination.

Conclusion

These findings help define the prevalence of MRSA virulence factors in catheter-related infections. Some of the products of the expressed genes that we detected in this work may serve as potential antigens for inclusion in a vaccine for the prevention of MRSA-catheter-related infections.

Evolution of community- and healthcare-associated methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is a prominent cause of human infections globally. The high prevalence of infections is compounded by antibiotic resistance--a significant problem for treatment. Methicillin-resistant S. aureus (MRSA) is endemic in hospitals and healthcare facilities worldwide, and is an increasingly common cause of community-associated bacterial infections in industrialized countries. Although much focus is placed on the role of S. aureus as a human pathogen, it is in fact a human commensal organism that has had a relatively long coexistence with the human host. Many S. aureus infections can be explained by host susceptibility or other predisposing risk factors. On the other hand, the emergence/re-emergence of successful S. aureus clones (referred to as epidemic waves) suggests a rapid bacterial adaption and evolution, which includes the emergence of antibiotic resistance and increased virulence and/or transmissibility. It is within this context that we review our understanding of selected S. aureus epidemic waves, and highlight the use of genome sequencing as a means to better understand the evolution of each lineage.

Epidemiologic Similarities in Pediatric Community-Associated Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus in the San Francisco Bay Area

BACKGROUND

Risk factors differentiating methicillin-resistant Staphylococcus aureus (MRSA) from methicillin-sensitive S aureus (MSSA) infections in the pediatric community have been unclear.

METHODS

We performed a prospective case-comparison investigation of clinical, epidemiological, and molecular factors in pediatric community-associated (CA) MRSA and MSSA cases in the San Francisco Bay Area. Chart reviews were conducted in 270 CA-MRSA and 313 CA-MSSA cases. Fifty-eight CA-MRSA (21.4%) and 95 CA-MSSA (30.4%) cases were interviewed. Molecular typing was performed on 111 isolates.

RESULTS

MSSA represented 53.7% of CA cases and was more likely to cause invasive disease (6.2% vs 1.1%, P = .004). Few potential epidemiologic risk factors distinguished CA-MRSA from CA-MSSA. No differences were found in factors related to crowding, cleanliness, or prior antibiotic use. Compromised skin integrity due to eczema (24.3% vs 13.5%, P = .001) was associated with CA-MSSA. Many exposures to potentially infected or colonized contacts or contaminated objects were assessed; only three were associated with CA-MSSA: having a household contact who had surgery in the past year (18.9% vs 6.0%, P = .02), and regular visits to a public shower (9.1% vs 2.0%, P = .01) or gym (12.6% vs 3.3%, P = .04). Molecular typing identified clonal complex 8 as the predominant genetic lineage among CA-MRSA (96.4%) and CA-MSSA (39.3%) isolates.

CONCLUSIONS

In the context of recent heightened focus on CA-MRSA, the burden of serious disease caused by CA-MSSA among children should not be overlooked. MRSA and MSSA may be growing epidemiologically similar; thus, research, clinical, and public health efforts should focus on S aureus as a single entity.

High rate of qacA- and qacB-positive methicillin-resistant Staphylococcus aureus isolates from chlorhexidine-impregnated catheter-related bloodstream infections

Chlorhexidine has been widely used for infection control. Although the use of chlorhexidine-impregnated catheters has reduced catheter-related infections, chlorhexidine-resistant Staphylococcus aureus has emerged. The correlation between the existence of the chlorhexidine-resistant genes qacA and qacB (qacA/B) in methicillin-resistant Staphylococcus aureus (MRSA) isolates and the effectiveness of chlorhexidine-impregnated catheters in the prevention of MRSA infections is unknown. Sixty methicillin-sensitive Staphylococcus aureus (MSSA) and 96 MRSA isolates from the blood cultures of different patients were collected, and a case-control study was conducted to determine whether more clinical S. aureus isolates from chlorhexidine-impregnated catheter-related bloodstream infections (CRBSI) have the biocide-resistant genes (qacA/B or smr) than those from other infections. The chlorhexidine MIC(50)s of MSSA and MRSA isolates were 1 μg/ml and 2 μg/ml, respectively. Results of PCR analyses showed that 3.3% (n = 2) of MSSA and 43.8% (n = 42) of MRSA isolates harbored qacA/B and 5% (n = 3) of MSSA and 25% (n = 24) of MRSA isolates contained smr. With multivariate logistic regression analyses, the significant risk factors for definite CRBSI with chlorhexidine-impregnated catheters were determined to be S. aureus isolates with qacA/B and a chlorhexidine MIC of ≥2 μg/ml (odds ratios [OR], 9.264 and 8.137, respectively, in all 156 S. aureus isolates and 6.097 and 4.373, respectively, in the 96 MRSA isolates). Further prospective studies are needed to investigate the transmission of these biocide-resistant genes.

Infectious Disease Consultation for Staphylococcus aureus Bacteremia Improves Patient Management and Outcomes

BACKGROUND: Staphylococcus aureus bacteremia (SAB) is a common, severe infectious disease with accepted standards of care. METHODS: A retrospective cohort study of all 233 SAB cases at the Minneapolis Veterans Affairs Medical Center (MVAMC) between October 2004 and February 2008 was performed to measure the impact of Infectious Disease (ID) consultation on conformance to standards and patient outcomes. Outcomes were classified as survived without relapse, relapsed, or died without relapse. ID involvement was classified as consultation, curbside, or no involvement. RESULTS: ID involvement occurred in 179/233 cases (77%). Management conformed to accepted standards in 162/197 cases (82%) evaluable for conformance. ID involvement was associated with increased conformance in univariable analysis and multivariable analysis adjusted for propensity for ID consultation (OR 5.9, 95% CI 2.5 - 13.8). Relapse occurred in 14/156 cases (9%) in which therapy conformed to standards compared with 8/35 cases (23%) in which therapy did not conform to standards (p=0.045). Relapse was more common in older patients (OR 1.05, CI 1.01-1.09) and in cases without ID involvement (OR 3.02, CI 1.003-9.1). Death was associated with greater Charlson Index scores (OR 1.89, CI 1.4-2.5). Of 111 cases with definitely or possibly infected devices, relapse occurred in 9/92 cases (9.8%) in which the device was wholly or partially removed compared with 6/19 cases (32%) in which the device was left in place (p=0.02). CONCLUSIONS: ID involvement in SAB cases was associated with increased adherence to accepted standards and fewer relapses. ID consultation should be performed for all SAB cases.

Community-associated meticillin-resistant Staphylococcus aureus: the case for a genotypic definition

BACKGROUND

New distinct strains of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) have emerged as a cause of infection in previously healthy individuals in community settings. It is important to identify CA-MRSA for clinical management, epidemiological analysis, infection prevention and control, and regulatory reporting, but definitions and nomenclature of these strains are confused.

AIM

To review attempts to define CA-MRSA and propose a new definition.

METHODS

Non-systematic review.

FINDINGS

Epidemiological definitions were useful for differentiating CA-MRSA and healthcare-associated (HA)-MRSA strain types in the past. However, although HA-MRSA strain types are rarely transmitted in the community, CA-MRSA strains have started to be transmitted in healthcare facilities, so epidemiological definitions are breaking down. CA-MRSA are community strains of S. aureus that have acquired the meticillin resistance gene, mecA. They are distinct from HA-MRSA and should be defined genetically. This may be done by combining genotypic typing by multi-locus sequence or spa with analysis of the staphylococcal cassette chromosome mec. Carriage of Panton-Valentine leukocidin or antimicrobial susceptibility profiles can be useful indicators of CA-MRSA but should not be used for their definition.

CONCLUSION

For full assessment of their epidemiology, MRSA infections should be characterized as: (1) caused by HA- or CA-MRSA strain types; (2) acquired in community or healthcare settings; and (3) onset in the community or healthcare facility.

Neutrophils in innate host defense against Staphylococcus aureus infections

Staphylococcus aureus has been an important human pathogen throughout history and is currently a leading cause of bacterial infections worldwide. S. aureus has the unique ability to cause a continuum of diseases, ranging from minor skin infections to fatal necrotizing pneumonia. Moreover, the emergence of highly virulent, drug-resistant strains such as methicillin-resistant S. aureus in both healthcare and community settings is a major therapeutic concern. Neutrophils are the most prominent cellular component of the innate immune system and provide an essential primary defense against bacterial pathogens such as S. aureus. Neutrophils are rapidly recruited to sites of infection where they bind and ingest invading S. aureus, and this process triggers potent oxidative and non-oxidative antimicrobial killing mechanisms that serve to limit pathogen survival and dissemination. S. aureus has evolved numerous mechanisms to evade host defense strategies employed by neutrophils, including the ability to modulate normal neutrophil turnover, a process critical to the resolution of acute inflammation. Here we provide an overview of the role of neutrophils in host defense against bacterial pathogens and discuss strategies employed by S. aureus to circumvent neutrophil function.

Risk factors for household transmission of community-associated methicillin-resistant Staphylococcus aureus

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a community pathogen. Community-associated (CA) MRSA infections have occurred among multiple members of a household. We describe the incidence of and risk factors for MRSA colonization among household contacts of children with CA-MRSA infections.

METHODS

MRSA-infected children <18 years of age who lacked established healthcare-associated MRSA risk factors were identified through surveillance at 12 Minnesota hospital laboratories. Nasal swab specimens and information on medical history and hygiene behaviors were collected from case-patients and enrolled household contacts during home visits. S. aureus isolates obtained from nasal cultures were screened for oxacillin resistance.

RESULTS

In all, 236 households consisting of 236 case-patients and 712 household contacts were enrolled. Home visits were conducted on an average of 69 days after the onset of symptom in case-patients (range: 16-178 days). Twenty-nine (13%) case-patients and 82 (12%) household contacts had MRSA nasal colonization. Nasal MRSA colonization in ≥ 1 household contact occurred in 58 (25%) households. Household contacts who assisted the case-patient to bathe or who shared balms/ointments/lotion with the case-patient were more likely to be colonized (P < 0.01, P < 0.05), whereas those who reported using antibacterial versus nonantibacterial soap for hand washing were less likely to be colonized (P < 0.05) with MRSA clonally related to the case-patient infection isolate.

CONCLUSIONS

Only 13% of case-patients had MRSA nasal colonization on an average of 69 days after their initial MRSA infection. CA-MRSA colonization may be short-lived or may occur at non-nasal sites. One quarter of households had at least one household contact colonized with MRSA. Modifiable behaviors, such as sharing personal items, may contribute to transmission.

Common childhood bacterial infections

Children with infectious diseases are commonly encountered in primary care settings. Identification of the subset of patients with bacterial infections is key in guiding the best possible management. Clinicians frequently care for children with infections of the upper respiratory tract, including acute otitis media, otitis externa, sinusitis, and pharyngitis. Conjunctivitis is not an uncommon reason for office visits. Bacterial pneumonia, urinary tract infections, and gastroenteritis are regularly seen. Over the last decade, a growing number of children have had infections of the skin and soft tissue, driven by the increased prevalence of infections caused by methicillin-resistant Staphylococcus aureus. The following review addresses the epidemiology and risk factors for specific infections and examines the clinical presentation and selection of appropriate diagnostic methods in such conditions. Methods to prevent these bacterial infections and recommendations for follow-up are suggested. Management of these infections requires that antimicrobial agents be used in a judicious manner in the outpatient setting. Such antibiotic therapy is recommended using both available clinical evidence and review of disease-specific treatment guidelines.

Clonal spreading of methicillin-resistant SCCmec Staphylococcus aureus with specific spa and dru types in central Taiwan

The goal of this study was to delineate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Ninety-six MRSA isolates were collected from the blood cultures of different patients during the period July to December of 2008. The spa typing, staphylococcal chromosomal cassette (SCCmec) typing, mec-associated direct repeat unit (dru) copy numbers, and toxin genes (sea, seb, sec, tst, lukS/F) of each isolate were determined. Thirty-eight, 28, 18, and 12 MRSA isolates were SCCmec type II, SCCmec type III, SCCmec type IV, and SCCmec type V, respectively. Most (31/38, 81.6%) of the SCCmec type II isolates were of spa t002 with four dru repeats. Some of them also carried the sec or tst toxin gene (67.7 and 80.6%, respectively). Of the 28 SCCmec type III MRSA isolates, 15 (53.6%) were of t037 with 14 dru repeats, and all also carried the sea gene. Of the 18 SCCmec type IV MRSA isolates, 13 (72.2%) were of t437 with nine dru repeats, and ten of them also had the seb gene. Among the SCCmec type V MRSA isolates, nine were type V(T). Five (55.6%) of them were of t437 with 11 dru repeats, and all contained the lukS/F gene. The clonal spreading of SCCmec MRSA strains with specific spa and dru types was found. Further longitudinal, multiple-site surveillance is required in order to define the MRSA evolution in Taiwan.

Molecular characterization of methicillin-resistant Staphylococcus aureus obtained from the anterior nares of healthy Korean children attending daycare centers

OBJECTIVES

This study was performed to investigate the molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolated from the anterior nares of Korean children attending daycare centers.

METHODS

During September and October 2008, a survey of nasal carriage of MRSA was conducted among healthy children who were attending daycare centers in Seoul, Korea. Nasal swab samples were cultured to isolate S. aureus, and antimicrobial susceptibility was assessed using a disk diffusion test. All MRSA isolates were archived for subsequent molecular tests, including multilocus sequence typing, Panton-Valentine leukocidin (PVL) genes polymerase chain reaction (PCR), and staphylococcal cassette chromosome mec (SCCmec) typing.

RESULTS

Among 428 preschool-aged children enrolled, 9.3% (40/428) were colonized with MRSA. Among the 40 MRSA isolates, antibiotic susceptibilities to clindamycin and erythromycin were 97.5% (39/40) and 45% (18/40), respectively. All of the 21 strains susceptible to clindamycin and resistant to erythromycin had MLS(B)-inducible phenotypes. Sequence type (ST) 72-SCCmec type IV was the predominant clone (n=23; 57.5%), followed by ST72-SCCmec type II (n=6; 15%), ST1765-SCCmec type IV (n=4; 10%), ST1765-SCCmec type II (n=2; 5%), and ST1-SCCmec type IV (n=2; 5%). No clone was positive for PVL genes.

CONCLUSIONS

ST72 strains, which were previously found in hospital-associated MRSA, are now widely distributed in healthy Korean children. In addition, the prevalence of inducible resistance of clindamycin should be considered when selecting empirical antibiotics for community-associated MRSA infections in Korea.

High prevalence of ST121 in community-associated methicillin-susceptible Staphylococcus aureus lineages responsible for skin and soft tissue infections in Portuguese children

In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Portugal, we analyzed a collection of 38 S. aureus isolates recovered from 30 children attending the pediatric emergency department of a central hospital in Lisbon due to skin and soft tissue infections. Molecular characterization identified seven clonal lineages among the 35 methicillin-susceptible S. aureus (MSSA) isolates, of which the major lineage PFGE A/t159/ST121 included 63% of the isolates. The three MRSA isolates belonged to the Pediatric clone PFGE D/t535/ST5-IV (n = 2) and to the European CA-MRSA clone PFGE G/t044/ST80-IVc (n = 1). All isolates harbored several virulence factors, namely, leukocidins. Panton-Valentine leukocidin (PVL) was produced by isolates from five MSSA lineages and by the ST80 MRSA. Of interest, this is the first reported isolation of CA-MRSA ST80 in Portugal.

Community-Associated Methicillin-Resistant Staphylococcus Aureus Skin and Soft Tissue Infections

The prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing globally and in Singapore. Skin and soft tissue infections (SSTIs) are the most common manifestations, ranging from common furuncles to the rare but life-threatening necrotizing fasciitis. Surgical drainage and debridement where feasible are the mainstay of therapy, whereas MRSA-active antibiotics are essential when surgery is not possible or as adjunctive therapy for severe and/or complicated SSTIs. In itself, the continued inexorable rise in CA-MRSA rates poses difficult challenges for primary healthcare and hospital infection control. Innovative approaches are required to mitigate its impact in both the community and hospital settings.

Public health surveillance for methicillin-resistant Staphylococcus aureus: comparison of methods for classifying health care- and community-associated infections

OBJECTIVES

We compared 3 methods for classifying methicillin-resistant Staphylococcus aureus (MRSA) infections as health care associated or community associated for use in public health surveillance.

METHODS

We analyzed data on MRSA infections reported to the Michigan Department of Community Health from October 1, 2004, to December 31, 2005. Patient demographics, risk factors, infection information, and susceptibility were collected for 2151 cases. We classified each case by the health care risk factor, infection-type, and susceptibility pattern methods and compared the results of the 3 methods.

RESULTS

Demographic, clinical, and microbiological variables yielded similar health care-associated and community-associated distributions when classified by risk factor and infection type. When 2 methods yielded the same classifications, the overall distribution was similar to classification by 3 methods. No specific combination of 2 methods was superior.

CONCLUSIONS

MRSA categorization by 2 methods is more accurate than it is by a single method. The health care risk factor and infection-type methods yield comparable classification results. Accuracy is increased by using more variables; however, further research is needed to identify the optimal combination.

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.

Community-associated meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide, and causes substantial morbidity and mortality. Health-care-associated MRSA infections arise in individuals with predisposing risk factors, such as surgery or presence of an indwelling medical device. By contrast, many community-associated MRSA (CA-MRSA) infections arise in otherwise healthy individuals who do not have such risk factors. Additionally, CA-MRSA infections are epidemic in some countries. These features suggest that CA-MRSA strains are more virulent and transmissible than are traditional hospital-associated MRSA strains. The restricted treatment options for CA-MRSA infections compound the effect of enhanced virulence and transmission. Although progress has been made towards understanding emergence of CA-MRSA, virulence, and treatment of infections, our knowledge remains incomplete. Here we review the most up-to-date knowledge and provide a perspective for the future prophylaxis or new treatments for CA-MRSA infections.

Community acquired methicillin-resistant Staphylococcus aureus pneumonia leading to rhabdomyolysis: a case report

Community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) is considered an underreported entity in India. In this case report, the authors describe a thirty-five year old immunocompetent male presenting with severe respiratory distress requiring intubation. On further work up, a CT thorax showed features consistent with necrotizing pneumonia. The morphology and sensitivity pattern of the organism found in the bronchoalveolar lavage fluid and blood culture were consistent with MRSA. The patient's stay in the hospital was complicated by acute renal failure due to rhabdomyolysis with CPK levels of 9995 U/L. The patient was started on dialysis and improved there after. This case brings to light that CA-MRSA is becoming a problem in developing nations where antibiotics are frequently used empirically with little laboratory guidance. It also is a rare reporting of rhabdomyolysis due to CA-MRSA.

Community-associated methicillin-resistant Staphylococcus aureus infections

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been recognized for over a decade, and usually refers to MRSA identified in previously healthy individuals with no recognized MRSA risk factors. Infections range from minor skin and soft tissue infections, through to severe pneumonia and necrotizing fasciitis. This review summarizes the current data on the epidemiology and molecular features of CA-MRSA, in addition to diagnosis and therapeutic measures. We also refer to current national guidelines for the management of these infections. Areas of agreement include the important genotypic and phenotypic differences of community MRSA strains compared with hospital strains. Areas of controversy include the precise epidemiological definition of community-acquired/associated MRSA. Fortunately, true CA-MRSA can be differentiated from hospital MRSA by molecular techniques, as discussed herein. Recent interest has focused on the changing epidemiology of CA-MRSA. Worldwide, CA-MRSA is now seen outside of the initial specific population groups, and in the USA, the successful USA300 community strain is beginning to spread back into hospitals. Reasons why USA300 remains relatively uncommon in Europe are unclear. Topics timely for research include the investigation of the epidemiology of infections and evolutionary genomics.

Methicillin-resistant Staphylococcus aureus in resident animals of a long-term care facility

Animals provide benefits to elderly and chronically ill people by decreasing loneliness, increasing social interactions, and improving mental health. As a result, many hospitals and long-term care facilities allow family pets to visit ill or convalescing patients or support animal-assisted therapy programs. These include programs that have resident animals in long-term care facilities. Despite the benefits, there are concerns about disease transmission between pets and patients. Antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), are a recognized problem in healthcare settings leading to refractory infections and potentially life-threatening illnesses. MRSA has been isolated from numerous animal species, yet few studies are available on the carriage of this pathogen in animals residing in long-term care facilities. Our objective was to characterize MRSA carriage among resident animals in a long-term care facility.

METHODS

To document MRSA colonization, nasal swabs from 12 resident animals (one dogs and 11 cats) of a long-term care facility were collected weekly for 8 weeks. Staphylococcus isolates were characterized by antimicrobial susceptibility and MRSA isolates were further characterized by pulsed-field gel electrophoresis (PFGE). PFGE isolate patterns were compared with an existing database of MRSA isolate patterns at the Minnesota Department of Health.

RESULTS

Two of 11 cats were colonized with MRSA. MRSA was recovered from five of eight weekly samples in one cat and two of eight weekly samples in the other cat. All isolates were classified as USA100 (healthcare-associated strains).

DISCUSSION

Long-term care resident animals may acquire MRSA. Clonally related strains were identified over the 8-week sampling period. It is unclear if pets serve as an on-going source of infection to their human companions in long-term care facilities.

Scapular abscess, septic emboli, and deep vein thrombosis in a healthy child due to community-acquired methicillin-resistant Staphylococcus aureus: case report

We describe a case of a scapular abscess, osteomyelitis, septic emboli, and occlusive venous thrombosis secondary to community-acquired methicillin-resistant Staphylococcus aureus in an otherwise healthy pediatric patient. This syndrome represents a life-threatening condition that should ideally be recognized and treated in a timely fashion, not only with early antibiotics and hospital admission but also with anticoagulation and possible surgical intervention. Clinicians need to be aware of the severity of the illness that can be caused by community-acquired methicillin-resistant Staphylococcus aureus infections and complications including venous thrombosis and septic emboli.

A study on antimicrobial susceptibility pattern in clinical isolates of Staphylococcus aureus in Eritrea

Background:

Staphylococcus aureus is a major pathogen in skin and soft tissue infections. Methicillin resistant S.aureus (MRSA) is prevalent in most of the countries wherever it is sought for. MRSA is one of the important pathogens implicated in hospital acquired infection. The main objectives of this study was to find out the antimicrobial susceptibility pattern of S.aureus isolates, the prevalence of methicillin resistant S.aureus (MRSA) and nasal carriage rate in healthy hospital staff.

Method

A total of 278 S.aureus strains isolated from clinical specimens were tested for antimicrobial susceptibility and 30 anterior nares swabs from healthy hospital staff were screened for S.aureus organisms using standard methods.

Results:

High resistance was observed against ampicillin, penicillin and tetracycline. High sensitivity was recorded against amikasin, amoxicillin-c and ciprofloxacin. Of the 278 isolates 26 (9%) isolates were methicillin resistant S.aureus (MRSA). 17 % of the hospital staff were positive for nasal carriage of Staphylococcus aureus .

Conclusion:

Our study emphasizes the need for continuous monitoring of the antimicrobial susceptibility pattern of S.aureus isolates including MRSA for the selection of appropriate therapy. In Eritrea, from the present findings it appears that the spread of MRSA in community and hospital settings is limited.

Usefulness of antimicrobial resistance pattern for detecting PVL- or TSST-1-producing meticillin-resistant Staphylococcus aureus in a French university hospital

Several recent reports have suggested that community-associated meticillin-resistant Staphylococcus aureus (MRSA) clones, particularly those harbouring genes for Panton-Valentine leukocidin (PVL) or toxic shock syndrome toxin 1 (TSST-1), are increasingly responsible for infections in hospitals. Here, a retrospective study was carried out to investigate whether antimicrobial resistance patterns could be used to detect these pathogens in a French university hospital. Isolates were characterized by antimicrobial susceptibility testing, PCR profiling (PVL genes and tst), PFGE typing and multilocus sequence typing. Demographic and clinical data were collected from all patients. For PVL-positive MRSA, the typical antimicrobial resistance pattern (susceptible to fluoroquinolones, non-susceptible to fusidic acid, kanamycin resistant and susceptible to gentamicin and tobramycin) had a sensitivity of 77.8 % and a positive predictive value (PPV) of 100 %. For tst-positive MRSA, the antimicrobial resistance pattern (susceptible to fluoroquinolones and non-susceptible to fusidic acid) had a sensitivity of 100 % and a PPV of 72.4 %. These results suggest that phenotypic rules based on antimicrobial resistance patterns are potentially useful for the detection of PVL- and tst-positive MRSA isolates.

Usefulness of antibiogram surveillance for methicillin-resistant Staphylococcus aureus in outpatient pediatric populations

We assessed the impact of distributing an outpatient age-specific methicillin-resistant Staphylococcus aureus (MRSA) antibiogram on physician knowledge of MRSA prevalence and choice of empiric therapy. Questionnaires were given to 125 physicians at outpatient pediatric clinics in Monroe County, NY, before and after antibiogram distribution (response rates, 42% and 24%, respectively). The median physician-estimated MRSA prevalence (among S. aureus skin infections) was 15% before they received the antibiogram and 20% after. According to the antibiogram, the true 2005 prevalence was 25% among skin infections. When asked to select empiric therapy for a pediatric outpatient with a skin abscess, while assuming varying levels of MRSA prevalence, most selected cephalexin when the prevalence was assumed to be 20% or less, and trimethoprim-sulfamethoxazole when the prevalence was assumed to be 30% or greater. These data suggest that antibiograms may improve empiric therapy decision making by increasing knowledge of local outpatient prevalence of antibiotic resistance.

Skin and soft-tissue infections caused by community-acquired methicillin-resistant Staphylococcus aureus

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection has become epidemic. Skin and soft-tissue infections (SSTIs) are the most frequent forms of the disease. Obtainment of culture specimens is important for documentation of the presence of MRSA and for susceptibility testing to guide therapy. Purulent lesions should be drained whenever possible. In areas where community-acquired MRSA isolates are prevalent, uncomplicated SSTI in healthy individuals may be treated empirically with clindamycin, trimethoprim-sulfamethoxazole, or long-acting tetracyclines, although specific data supporting the efficacy of these treatments are lacking. In healthy patients with small purulent lesions, drainage alone may be sufficient. In patients with complicated SSTI requiring hospitalization or intravenous therapy, vancomycin is the drug of choice because of the low cost, efficacy, and safety. Linezolid, daptomycin, and tigecycline are also effective, although published studies on the last 2 agents for the treatment of SSTI due to MRSA are more limited. Dalbavancin, telavancin, and ceftobiprole are investigational agents that may expand our therapeutic options for the treatment of SSTI caused by MRSA.