Proposed definitions of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA)

On-site detection of methicillin-resistant Staphylococcus aureus (MRSA) utilizing G-quadruplex based isothermal exponential amplification reaction (GQ-EXPAR)

Methicillin-resistant Staphylococcus aureus (MRSA) has a high incidence in infectious hospitals and communities, highlighting the need for early on-site detection due to its resistance to methicillin antibiotics. The present study introduces a highly sensitive detection system for mecA, a crucial methicillin marker, utilizing an RCA-based isothermal exponential amplification reaction. The G-quadruplex-based isothermal exponential amplification reaction (GQ-EXPAR) method designs probes to establish G-quadruplex secondary structures incorporating thioflavin T for fluorescence. The system, unlike conventional genetic detection methods, works with portable isothermal PCR devices (isoQuark), facilitating on-site detection. A detection limit of 0.1 fmol was demonstrated using synthetic DNA, and effective detection was proven using thermal lysis. The study also validated the detection of targets swabbed from surfaces within bacterial 3D nanostructures using the GQ-EXPAR method. After applying complementary sequences to the padlock probe for the target, the GQ-EXPAR method can be used on various targets. The developed method could facilitate rapid and accurate diagnostics within MRSA strains.

Inhibition of α-hemolysin activity of Staphylococcus aureus by theaflavin 3,3'-digallate

The ongoing rise in antibiotic resistance, and a waning of the introduction of new antibiotics, has resulted in limited treatment options for bacterial infections, including these caused by methicillin-resistant Staphylococcus aureus, leaving the world in a post-antibiotic era. Here, we set out to examine mechanisms by which theaflavin 3,3'-digallate (TF3) might act as an anti-hemolytic compound. In the presented study, we found that TF3 has weak bacteriostatic and bactericidal effects on Staphylococcus aureus, and strong inhibitory effect towards the hemolytic activity of its α-hemolysin (Hla) including its production and secretion. A supportive SPR assay reinforced these results and further revealed binding of TF3 to Hla with KD = 4.57×10-5 M. Interestingly, TF3 was also able to protect human primary keratinocytes from Hla-induced cell death, being at the same time non-toxic for them. Further analysis of TF3 properties revealed that TF3 blocked Hla-prompting immune reaction by inhibiting production and secretion of IL1β, IL6, and TNFα in vitro and in vivo, through affecting NFκB activity. Additionally, we observed that TF3 also markedly attenuated S. aureus-induced barrier disruption, by inhibiting Hla-triggered E-cadherin and ZO-1 impairment. Overall, by blocking activity of Hla, TF3 subsequently subdued the inflammation and protected the epithelial barrier, which is considered as beneficial to relieving skin injury.

Genetic Diversity among Methicillin-Resistant Staphylococcus aureus in Malaysia (2002-2020)

1.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a common organism seen in both healthcare-associated and community-associated infections worldwide and in Malaysia over the past two decades. The aim of this review is to provide a firsthand documentation of all MRSA strains prevalent in the Malaysian population from 2002 to present and briefly describe the changing patterns. 2.

METHODS

Electronic and manual intensive literature searches were conducted between 2002 and 2020, addressing issues directly related to patients and published in the English language were selected. 3.

RESULTS

The literature search retrieved a total of 2217 articles and abstracts of 27 articles. The search yielded a total of 24 articles on genotyping of MRSA in Malaysia. The study found that MRSA strains were mostly genetically related and resulted in the predominant MRSA clones that caused active infections. Thirty-six different sequence types (ST) were recorded. The highest rates of STs detected were ST239 (52.6%), ST1 (47.4%), and ST22 (42.1%). The majority of studies showed that both SCCmec types III and IV were the most common SCCm type in Malaysia, followed by SCCmec type V (57.9%). 4.

CONCLUSIONS

Both Brazilian (ST 239 IIIA) and Hungarian (ST 239-III) MRSA strains were detected in Malaysia. PFGE remains the best method for comparing MRSA strains. However, whole-genome sequencing has a promising chance to replace PFGE in the future.

Genomic characterization of two community-acquired methicillin-resistant Staphylococcus aureus with novel sequence types in Kenya

Staphylococcus aureus is a clinically important bacteria with high antimicrobial resistance (AMR) challenge globally. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) clones with unique sequence types have been identified in the community showing evidence that the epidemiology of MRSA globally is changing and requires continual surveillance. We utilized whole genome sequencing to characterize two community acquired-MRSA (CA-MRSA) strains isolated from wound swabs from community-onset infections in two health facilities in Kenya. The two strains belonged to multilocus sequence type (MLST) sequence type (ST) 7460, and ST 7635. The resistance genes detected showed that the novel STs are carriers of clinically relevant resistance genes. Linezolid and mupirocin resistance was observed, yet mupirocin is not commonly used in the country. Mutations within resistance genes were also detected and the pathogenicity toward the human host matched various pathogenic global S. aureus families, e.g., S. aureus subsp. aureus USA300. Multidrug efflux transporters, important in antimicrobial resistance including restriction enzymes type I and type IV were detected. Plasmids identified showed similarities with the plasmids in other clinically significant non-staphylococcal species, such as Pseudomonas aeruginosa, Escherichia coli, Morganella morganii, and Enterococcus faecium. Both STs belong to clonal complex 8 (CC8) which is the most successful MRSA clone in Kenya. Spa type t30 to which ST 7635 belongs has not been reported in the country. The results of this study further highlight the need for epidemiological studies to reveal circulating strains and antimicrobial resistance spread between hospitals and the community. The genomic research highlights resistance to anti-staphylococcal broad-spectrum antimicrobials not used frequently in the country, jeopardizing successful MRSA treatment since most health facilities do not perform genotypic resistance tests for routine patient management. Preliminary insights into unidentified STs of CA-MRSA in Kenya show the need for molecular epidemiological surveillance studies to further understand the diversity of S. aureus in Africa.

Novel therapeutic interventions towards improved management of septic arthritis

Septic arthritis (SA) represents a medical emergency that needs immediate diagnosis and urgent treatment. Despite aggressive treatment and rapid diagnosis of the causative agent, the mortality and lifelong disability, associated with septic arthritis remain high as close to 11%. Moreover, with the rise in drug resistance, the rates of failure of conventional antibiotic therapy have also increased. Among the etiological agents frequently isolated from cases of septic arthritis, Staphylococcus aureus emerges as a dominating pathogen, and to worsen, the rise in methicillin-resistant S. aureus (MRSA) isolates in bone and joint infections is worrisome. MRSA associated cases of septic arthritis exhibit higher mortality, longer hospital stay, and higher treatment failure with poorer clinical outcomes as compared to cases caused by the sensitive strain i.e methicillin-sensitive S. aureus (MSSA).

In addition to this, equal or even greater damage is imposed by the exacerbated immune response mounted by the patient’s body in a futile attempt to eradicate the bacteria. The antibiotic therapy may not be sufficient enough to control the progression of damage to the joint involved thus, adding to higher mortality and disability rates despite the prompt and timely start of treatment. This situation implies that efforts and focus towards studying/understanding new strategies for improved management of sepsis arthritis is prudent and worth exploring.

The review article aims to give a complete insight into the new therapeutic approaches studied by workers lately in this field. To the best of our knowledge studies highlighting the novel therapeutic strategies against septic arthritis are limited in the literature, although articles on pathogenic mechanism and choice of antibiotics for therapy, current treatment algorithms followed have been discussed by workers in the past. The present study presents and discusses the new alternative approaches, their mechanism of action, proof of concept, and work done so far towards their clinical success. This will surely help to enlighten the researchers with comprehensive knowledge of the new interventions that can be used as an adjunct therapy along with conventional treatment protocol for improved success rates.

Prevalence and association of Panton-Valentine Leukocidin gene with the risk of sepsis in patients infected with Methicillin Resistant Staphylococcus aureus

BACKGROUND

Panton-Valentine Leukocidin (PVL), is one of the virulence gene expressed by Methicillin Resistant Staphylococcus aureus (MRSA) and is known to be associated with severe form of community acquired MRSA infection. The aim of this study is to investigate its prevalence in our setting and patient's clinical outcome.

METHODS

A cross sectional study involve retrospective record review were done involving 90 MRSA positive isolates between November 2016 and October 2017. Multiplex PCR was performed to detect femA, mecA and PVL genes. Clinical presentation and outcomes of patients were reviewed and presented as descriptive analysis.

RESULTS

All of the 90 MRSA isolates included in this study were positive for femA and mecA genes following PCR. PVL gene was detected in 20% (n = 18) of the isolates of which 61.1% (n = 11) were community acquired infections and 38.8% (n = 7) were hospital acquired. Case distribution from community acquired infections include patients with skin and soft tissue infections (33.3%, n = 6), infected diabetic foot ulcers (16.7%, n = 3), and one patient each (5.5%, n = 1) for community acquired pneumonia and meningitis. Half of the PVL positive MRSA cases (50%, n = 9) were having sepsis and four of them succumbed to death due to severe infection.

CONCLUSION

This study shows a high prevalence of PVL positive MRSA infection in our population. Skin and soft tissue infections accounting for the major sources. In addition, the presence of the PVL gene is associated with increased risk for developing sepsis.

Prevalence, molecular characteristics and antimicrobial susceptibility patterns of MRSA in hospitalized and nonhospitalized patients in Barbados

The epidemiology and clonality of methicillin-resistant Staphylococcus aureus (MRSA) has not been investigated, as not much research or surveillance has been undertaken to identify and characterize the circulating MRSA strains in Barbados. Prevalence rates, molecular characteristics and antimicrobial susceptibility pattern of MRSA infections in hospitalized and nonhospitalized patients were investigated. A total of 293 isolates were included in the study, with 100 from the hospital and 193 from the public health laboratory. Isolates were collected over a period of 1 (2015–2016) and 3 years (2013–2016) respectively. MRSA was identified using standard microbiologic techniques and was further analysed by multiplex PCR for the presence of the spa, mec gene complex typing and PVL genes (lukS-PV and lukF-PV). A prevalence rate of 19.7% was calculated for those hospitalized. All hospital isolates were sensitive to vancomycin, rifampin, linezolid and cotrimoxazole (trimethoprim/sulfamethoxazole), whilst 82% were sensitive to clindamycin. The PVL gene was detected in 76% of hospital isolates. In the community isolates, resistance was observed in erythromycin (100%), ciprofloxacin (97.4%), clindamycin (13%) and cotrimoxazole (5.7%). There was no resistance to vancomycin. The PVL gene was detected in 97.9% of the isolates, the mecA gene in only 2.1% and the mecC gene in 0%. Most MRSA isolates were community acquired in both settings, and the antimicrobial susceptibility profile was similar, suggesting transmission of community-associated MRSA into the hospital environment. Further harmonization of antimicrobial policy for the treatment of MRSA (and by extension other pathogens) should be implemented to quell ongoing transmission. We found that 93.4% of MRSA in Barbados treated in the primary healthcare system were sensitive to cotrimoxazole. By typing MRSA isolates and drawing interferences on transmission on the basis of genetic relatedness, transmission pathways may be tracked. Further studies must be performed for this high level of comprehensiveness so that with the surveillance of MRSA, effective strategies may be developed to prevent or limit transmission.

Prevalence and risk factors of community-associated methicillin-resistant Staphylococcus aureus carriage in Asia-Pacific region from 2000 to 2016: a systematic review and meta-analysis

OBJECTIVE

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging global public health threat. In response to a highlighted strategic priority of the World Health Organization Global Action Plan on Antimicrobial Resistance, to "strengthen the knowledge and evidence base through surveillance and research", we synthesized published articles to estimate CA-MRSA carriage prevalence in the Asia-Pacific region.

METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PROSPERO CRD:42017067399). We searched MEDLINE, EMBASE, and PubMed for articles published from 1 January 2000 to 19 May 2017, which reported CA-MRSA carriage (defined as either colonization or infection) in Asia-Pacific region from 2000 to 2016. Studies were stratified according to settings (community or hospital where CA-MRSA was isolated) and study populations (general public or subpopulations with specified characteristics). Ranges of CA-MRSA carriage prevalence were reported for study groups.

RESULTS

In total, 152 studies were identified. Large diversity was observed among studies in most study groups. In community-level studies, the CA-MRSA carriage prevalence among the general public ranged from 0% to 23.5%, whereas that ranged from 0.7% to 10.4% in hospital settings. From community-level studies, countries with the highest prevalence were India (16.5%-23.5%), followed by Vietnam (7.9%) and Taiwan (3.5%-3.8%). Children aged ≤6 (range: 0.5%-40.3%) and household members of CA-MRSA carriers (range: 13.0%-26.4%) are subgroups without specific health conditions but with much higher CA-MRSA carriage when compared to the general population.

CONCLUSION

Our CA-MRSA prevalence estimates serve as the baseline for future national and international surveillance. The ranges of prevalence and characteristics associated with CA-MRSA carriage can inform health authorities to formulate infection control policies for high-risk subgroups. Future studies should explore the heterogeneities in CA-MRSA carriage prevalence among subgroups and countries to clarify the predominant transmission mechanisms in Asia-Pacific and other regions.

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.

Staphylococcus aureus Toxins and Their Molecular Activity in Infectious Diseases

Staphylococcus aureus is a microorganism resident in the skin and nasal membranes with a dreadful pathogenic potential to cause a variety of community and hospital-acquired infections. The frequency of these infections is increasing and their treatment is becoming more difficult. The ability of S. aureus to form biofilms and the emergence of multidrug-resistant strains are the main reasons determining the challenge in dealing with these infections. S. aureus' infectious capacity and its success as a pathogen is related to the expression of virulence factors, among which the production of a wide variety of toxins is highlighted. For this reason, a better understanding of S. aureus toxins is needed to enable the development of new strategies to reduce their production and consequently improve therapeutic approaches. This review focuses on understanding the toxin-based pathogenesis of S. aureus and their role on infectious diseases.

Association of bacterial genotypes and epidemiological features with treatment failure in hemodialysis patients with methicillin-resistant Staphylococcus aureus bacteremia

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) infections in the hemodialysis (HD) population are epidemiologically classified as healthcare-associated infections. The data about the clinical impact and bacterial characteristics of hospital-onset (HO)- and community-onset (CO)-MRSA in HD patients are scarce. The current study analyzed the difference in the clinical and molecular characteristics of HO-MRSA and CO-MRSA.

METHODS

We performed a retrospective review and molecular analysis of clinical isolates from 106 HD patients with MRSA bacteremia from 2009 to 2014. CA genotypes were defined as isolates carrying the SCCmec type IV or V, and HA genotypes were defined as isolates harboring SCCmec type I, II, or III.

RESULTS

CO-MRSA infections occurred in 76 patients, and 30 patients had HO-MRSA infections. There was no significant difference in the treatment failure rates between patients with CO-MRSA infections and those with HO-MRSA infections. CA genotypes were associated with less treatment failure (odds ratio [OR]: 0.18; 95% confidence interval [95% CI], 0.07-0.49; p = 0.001). For isolates with a vancomycin minimum inhibitory concentration (MIC) < 1.5 mg/L, the multivariate analysis revealed that HA genotypes and cuffed tunneled catheter use were associated with treatment failure. For isolates with a vancomycin MIC ≥1.5 mg/L, the only risk factor for treatment failure was a higher Pitt score (OR: 1.76; 95% CI, 1.02-3.05; p = 0.043).

CONCLUSION

CA genotypes, but not the epidemiological classification of CO-MRSA, impacted the clinical outcome of MRSA bacteremia in the HD population.

DNA aptamer functionalized gold nanostructures for molecular recognition and photothermal inactivation of methicillin-Resistant Staphylococcus aureus

In this work, we report the development of DNA aptamer-functionalized gold nanoparticles (Apt@Au NPs) and gold nanorods (Apt@Au NRs) for inactivation of Methicillin-resistant Staphylococcus aureus (MRSA) with targeted photothermal therapy (PTT). Although both Apt@Au NPs and Apt@Au NRs specifically bind to MRSA cells, Apt@Au NPs and Apt@Au NRs inactivated ∼5% and over 95% of the cells,respectively through PTT. This difference in inactivation was based on the relatively high longitudinal absorption of near-infrared (NIR) radiation and strong photothermal conversion capability for the Apt@Au NRs compared to the Apt@Au NPs. The Au NRs served as a nanoplatform for the loading of thiolated aptamer and also provided multivalent effects for increasing binding strength and affinity to MRSA. Our results indicate that the type of aptamer and the degree of multivalent effect(s) are important factors for MRSA inactivation efficiency in PTT. We show that the Apt@Au NRs are a very effective and promising nanosystem for specific cell recognition and in vitro PTT.

Performance of an electronic health record-based phenotype algorithm to identify community associated methicillin-resistant Staphylococcus aureus cases and controls for genetic association studies

Background

Community associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is one of the most common causes of skin and soft tissue infections in the United States, and a variety of genetic host factors are suspected to be risk factors for recurrent infection. Based on the CDC definition, we have developed and validated an electronic health record (EHR) based CA-MRSA phenotype algorithm utilizing both structured and unstructured data.

Methods

The algorithm was validated at three eMERGE consortium sites, and positive predictive value, negative predictive value and sensitivity, were calculated. The algorithm was then run and data collected across seven total sites. The resulting data was used in GWAS analysis.

Results

Across seven sites, the CA-MRSA phenotype algorithm identified a total of 349 cases and 7761 controls among the genotyped European and African American biobank populations. PPV ranged from 68 to 100% for cases and 96 to 100% for controls; sensitivity ranged from 94 to 100% for cases and 75 to 100% for controls. Frequency of cases in the populations varied widely by site. There were no plausible GWAS-significant (p < 5 E −8) findings.

Conclusions

Differences in EHR data representation and screening patterns across sites may have affected identification of cases and controls and accounted for varying frequencies across sites. Future work identifying these patterns is necessary.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2020-2) contains supplementary material, which is available to authorized users.

Fecal Carriage of Staphylococcus aureus in the Hospital and Community Setting: A Systematic Review

BACKGROUND AND RATIONALE

Staphylococcus aureus fecal carriage has been identified as a potential source for nosocomial transmission and a risk factor for disease development. This systematic review determined the overall S. aureus [including methicillin susceptible and resistant S. aureus (MSSA and MRSA)] fecal carriage rates within the community and healthcare settings.

METHODOLOGY

Peer-reviewed articles indexed in Medline, Scopus, Academic Search Premier, Africa-Wide Information, CINAHL, and Web of Science were identified using applicable and controlled vocabulary through to 11 November 2015. Eligible studies were ascertained by three independent reviewers. Random-effects meta-analyses of proportions were performed to determine S. aureus, MSSA and MRSA fecal carriage rates reported by eligible studies.

RESULTS

Twenty six studies were included in this review. The pooled estimates for S. aureus, MSSA and MRSA fecal carriage were 26% (95% confidence interval (CI): 16.8-36.3%), 86% (95% confidence interval (CI): 65.9-97.9%) and 10% (95% CI: 0.7-27.0%), respectively. Fecal S. aureus carriage rates increased on average from 10 to 65% during the first 8 weeks of life, followed by an average carriage rate of 64% at 6 months and 46% at 1 year of life. Genotyping techniques were employed mainly in studies conducted in developed countries and comprised largely of gel-based techniques. Six studies reported on the role of S. aureus fecal strains in diarrhea (n = 2) and the risk for acquiring infections (n = 4). Eight of the 26 studies included in this review performed antibiotic susceptibility testing of S. aureus fecal isolates.

CONCLUSION

This study provides evidence that screening for S. aureus fecal carriage, at least in populations at high risk, could be an effective measure for the prevention of S. aureus transmission and infection in the healthcare and community setting. More well-structured studies need to be conducted and sequence-based genotyping techniques should be employed for the comparison of isolates on a global scale in both developing and developed countries.

Evidence for Community Transmission of Community-Associated but Not Health-Care-Associated Methicillin-Resistant Staphylococcus Aureus Strains Linked to Social and Material Deprivation: Spatial Analysis of Cross-sectional Data

BACKGROUND

Identifying and tackling the social determinants of infectious diseases has become a public health priority following the recognition that individuals with lower socioeconomic status are disproportionately affected by infectious diseases. In many parts of the world, epidemiologically and genotypically defined community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged to become frequent causes of hospital infection. The aim of this study was to use spatial models with adjustment for area-level hospital attendance to determine the transmission niche of genotypically defined CA- and health-care-associated (HA)-MRSA strains across a diverse region of South East London and to explore a potential link between MRSA carriage and markers of social and material deprivation.

METHODS AND FINDINGS

This study involved spatial analysis of cross-sectional data linked with all MRSA isolates identified by three National Health Service (NHS) microbiology laboratories between 1 November 2011 and 29 February 2012. The cohort of hospital-based NHS microbiology diagnostic services serves 867,254 usual residents in the Lambeth, Southwark, and Lewisham boroughs in South East London, United Kingdom (UK). Isolates were classified as HA- or CA-MRSA based on whole genome sequencing. All MRSA cases identified over 4 mo within the three-borough catchment area (n = 471) were mapped to small geographies and linked to area-level aggregated socioeconomic and demographic data. Disease mapping and ecological regression models were used to infer the most likely transmission niches for each MRSA genetic classification and to describe the spatial epidemiology of MRSA in relation to social determinants. Specifically, we aimed to identify demographic and socioeconomic population traits that explain cross-area extra variation in HA- and CA-MRSA relative risks following adjustment for hospital attendance data. We explored the potential for associations with the English Indices of Deprivation 2010 (including the Index of Multiple Deprivation and several deprivation domains and subdomains) and the 2011 England and Wales census demographic and socioeconomic indicators (including numbers of households by deprivation dimension) and indicators of population health. Both CA-and HA-MRSA were associated with household deprivation (CA-MRSA relative risk [RR]: 1.72 [1.03-2.94]; HA-MRSA RR: 1.57 [1.06-2.33]), which was correlated with hospital attendance (Pearson correlation coefficient [PCC] = 0.76). HA-MRSA was also associated with poor health (RR: 1.10 [1.01-1.19]) and residence in communal care homes (RR: 1.24 [1.12-1.37]), whereas CA-MRSA was linked with household overcrowding (RR: 1.58 [1.04-2.41]) and wider barriers, which represent a combined score for household overcrowding, low income, and homelessness (RR: 1.76 [1.16-2.70]). CA-MRSA was also associated with recent immigration to the UK (RR: 1.77 [1.19-2.66]). For the area-level variation in RR for CA-MRSA, 28.67% was attributable to the spatial arrangement of target geographies, compared with only 0.09% for HA-MRSA. An advantage to our study is that it provided a representative sample of usual residents receiving care in the catchment areas. A limitation is that relationships apparent in aggregated data analyses cannot be assumed to operate at the individual level.

CONCLUSIONS

There was no evidence of community transmission of HA-MRSA strains, implying that HA-MRSA cases identified in the community originate from the hospital reservoir and are maintained by frequent attendance at health care facilities. In contrast, there was a high risk of CA-MRSA in deprived areas linked with overcrowding, homelessness, low income, and recent immigration to the UK, which was not explainable by health care exposure. Furthermore, areas adjacent to these deprived areas were themselves at greater risk of CA-MRSA, indicating community transmission of CA-MRSA. This ongoing community transmission could lead to CA-MRSA becoming the dominant strain types carried by patients admitted to hospital, particularly if successful hospital-based MRSA infection control programmes are maintained. These results suggest that community infection control programmes targeting transmission of CA-MRSA will be required to control MRSA in both the community and hospital. These epidemiological changes will also have implications for effectiveness of risk-factor-based hospital admission MRSA screening programmes.

The prevalence of community-associated methicillin-resistant Staphylococcus aureus among outpatient children in a tertiary hospital: A prospective observational study in Riyadh, Saudi Arabia

Background and objectives

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infections among previously healthy persons in community settings, without exposure to health care facilities, has been noted recently. Colonization rates of community-associated MRSA (CA-MRSA) have been reported to range from 0 to 9.2 percent. The nose and open skin areas are considered the most important sites for colonization. The aim of our study was to assess the prevalence and to describe the antibiotic susceptibility pattern of CA-MRSA among outpatient children.

Patients and methods

We prospectively screened every third consecutive child presenting to our pediatric emergency department of King Saud Medical City, a 275 bed tertiary care teaching hospital in Riyadh, Saudi Arabia, from March through July 2015.

Results

We analyzed a total of 830 screening results (n = 478 males, 57.6%). Most of the screened patients were from Riyadh (n = 824, 99.3%). A total of 164 (19.8%) were found to be colonized with S. aureus, and of these 38 (4.6%) with MRSA. Thus, the MRSA rate amongst all S. aureus carriers was 23.2%. All MRSA were susceptible to vancomycin, (94.7%) were susceptible to linezolid, (65.8%) to clindamycin, and (89.5%) to trimethoprim/sulfamethoxazole.

Conclusion

The rate of MRSA carriage among children in Riyadh province was within the range reported internationally. As the MRSA rate among S. aureus infected children was 23.2%, empirical MRSA coverage should be considered in children with suspected S. aureus infections.

Community-acquired necrotizing pneumonia caused by methicillin-resistant Staphylococcus aureus producing Panton-Valentine leukocidin in a Chinese teenager: case report and literature review

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has now been established as an important community-acquired pathogen. Although necrotizing pneumonia caused by community-acquired MRSA (CA-MRSA) strains producing Panton-Valentine leukocidin (PVL) has been reported with increasing frequency in many countries, it has been reported in only a few children younger than 1 year of age in Mainland China.

METHODS

We describe a case of life-threatening necrotizing pneumonia due to PVL-positive CA-MRSA in a 15-year-old previously healthy female who presented with high fever, shivering, a dry cough, and dyspnea. Details of the clinical outcomes, microbiological data, and therapies for this patient were collected and compared with those of cases reported in the literature on CA-MRSA.

RESULTS

Computed tomography (CT) findings showed cavitary consolidations in both lungs and bilateral pleural effusion. MRSA strains isolated from the patient's sputum and pleural fluid were susceptible to most non-β-lactam antimicrobial agents except for clindamycin and erythromycin. Both of these isolates tested positive for the mecA gene as well as PVL genes, and were identified as ST59-MRSA-SCCmec type IV-spa type t437. The patient was treated successfully with linezolid, fosfomycin, and teicoplanin.

CONCLUSIONS

To our knowledge, this is the first report from Mainland China of necrotizing pneumonia due to PVL-positive CA-MRSA among those aged older than 1 year. CA-MRSA necrotizing pneumonia should be considered in the differential diagnosis of severe community-acquired pneumonia, particularly in previously healthy individuals.

Staphylococcus aureus: Screening for Nasal Carriers in a Community Setting with Special Reference to MRSA

Introduction. Emergence of MRSA infections among previously healthy persons in community settings (without exposure to health care facilities) has been noted recently. MRSA infections are now classified as health care-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) infections. Its colonization is an important risk factor for subsequent MRSA infection. Aims and Objectives. The aim was to screen patients and health care workers for staphylococcal carriage, identify risk factors for MRSA colonization, and determine the sensitivity pattern. Materials and Methods. A total of 200 subjects were screened for nasal carriage after obtaining verbal consent. These were both healthy subjects attending various outpatient departments and health care workers. Specimens were collected from the anterior nares using premoistened sterile cotton swabs and inoculated onto blood agar and mannitol salt agar and incubated at 37°C for 24-48 h. Results. Staphylococcus aureus colonisation was found to be 12% (n = 24). MRSA was identified in 5% (n = 10) which represents 41.66% of SA. A total of 10 strains of MRSA were isolated from 200 subjects, giving an overall positivity rate of 5%. Discussion. Staphylococcal colonization was found to be 12% (MRSA 5%). Fluoroquinolone resistance was remarkable whereas all strains were sensitive to vancomycin, teicoplanin, linezolid, quinupristin-dalfopristin.

Clinical guidelines for the antimicrobial treatment of bone and joint infections in Korea

There are many various diseases in the bone and joint infections, and we tried to make antimicrobial treatment guidelines for common infectious diseases based on available data for microbiology and clinical trials. This guidelines focused on the treatment of osteomyelitis and septic arthritis, which can be experienced by physicians at diverse clinical settings. This guidelines is not applicable to diabetic foot infections, postoperative infections or post-traumatic infections which need special considerations. The guidelines for those conditions will be separately developed later. Surgical treatment of bone and joint infections, pediatric bone and joint infection, tuberculous bone and joint infection, and prophylactic antibiotic use were not included in this guideline.

Molecular recognition of live methicillin-resistant staphylococcus aureus cells using DNA aptamers

AIM: To generate DNA-aptamers binding to Methicillin-resistant Staphylococcus aureus (MRSA).

METHODS: The Cell-Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology was used to run the selection against MRSA bacteria and develop target-specific aptamers. MRSA bacteria were targeted while Enterococcus faecalis bacteria were used for counter selection during that process. Binding assays to determine the right aptamer candidates as well as binding assays on clinical samples were performed through flow cytometry and analyzed using the FlowJo software. The characterization of the aptamers was done by determination of their K_d values and determined by analysis of flow data at different aptamer concentration using SigmaPlot. Finally, the recognition of the complex Gold-nanoparticle-aptamer to the bacteria cells was observed using transmission electron microscopy (TEM).

RESULTS: During the cell-SELEX selection process, 17 rounds were necessary to generate enrichment of the pool. While the selection was run using fixed cells, it was shown that the binding of the pools with live cells was giving similar results. After sequencing and analysis of the two last pools, four sequences were identified to be aptamer candidates. The characterization of those aptamers showed that based on their K_d values, DTMRSA4 presented the best binding with a K_d value of 94.61 ± 18.82 nmol/L. A total of ten clinical samples of MRSA, S. aureus and Enterococcus faecalis were obtained to test those aptamers and determine their binding on a panel of samples. DTMRSA1 and DTMRSA3 showed the best results regarding their specificity to MRSA, DTMRSA1 being the most specific of all. Finally, those aptamers were coupled with gold-nanoparticle and their binding to MRSA cells was visualized through TEM showing that adduction of nanoparticles on the aptamers did not change their binding property.

CONCLUSION: A total of four aptamers that bind to MRSA were obtained with K_d values ranking from 94 to 200 nmol/L.

Surveillance and management of multidrug-resistant microorganisms

Multidrug-resistant organisms are an established and growing worldwide public health problem and few therapeutic options remain available. The traditional antimicrobials (glycopeptides) for multidrug-resistant Gram-positive infections are declining in efficacy. New drugs that are presently available are linezolid, daptomicin and tigecycline, which have well-defined indications for severe infections, and talavancin, which is under Phase III trial for hospital-acquired pneumonia. Unfortunately the therapies available for multidrug-resistant Gram-negatives, including carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae, are limited to only colistin and tigecycline. Both of these drugs are still not registered for severe infections, such as hospital acquired pneumonia. Consequently, as confirmed by scientific evidence, a multidisciplinary approach is needed. Surveillance, infection control procedures, isolation and antimicrobial stewardship should be implemented to reduce multidrug-resistant organism diffusion.

Molecular characterization of the first community-acquired methicillin-resistant Staphylococcus aureus strains from Central Iran

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has spread throughout the world with varying regional incidences and different staphylococcal cassette chromosome mec (SCCmec) elements in different genetic backgrounds. No information is available on CA-MRSA in Iran. A cross-sectional study was carried out among healthy students to investigate: (1) the prevalence of CA-MRSA in Central Iran, (2) the molecular epidemiology of such CA-MRSA strains, (3) the antimicrobial resistance patterns of the strains, and (4) the distribution of virulence genes in these CA-MRSA strains.

METHODS

A total of 700 nasal swabs were collected and subjected to S. aureus and MRSA-specific isolation procedures. Antimicrobial resistance patterns were determined using the disk diffusion method, and molecular typing was carried out by multi-locus sequence typing (MLST), SCCmec typing, and Staphylococcus protein A (spa) typing for all CA-MRSA isolates. PCR was used to detect various virulence genes.

RESULTS

One hundred fifty-four S. aureus strains were isolated from the anterior nares of 700 healthy students. According to the US Centers for Disease Control and Prevention definitions for CA-MRSA, seven (4.5%) isolates were confirmed as CA-MRSA. CA-MRSA isolates belonged to SCCmec types IV (n = 6) and V (n = 1). The predominant spa-type among the CA-MRSA isolates was t790 (n = 3), with single t660, t084, and t325 isolates; one isolate was not typeable. The predominant sequence type was ST22, t790, SCCmec IV in three isolates, and the four other sequence types were ST25, ST859, ST14, and ST15.

CONCLUSIONS

Iranian CA-MRSA strains are genetically diverse with an elevated prevalence of t790/ST22 SCCmec IV isolates. These findings support the need for more effective infection control measures to reduce nasal carriage and prevent dissemination of CA-MRSA in Iran.

Molecular identification and antimicrobial susceptibility of Staphylococcus aureus nasal isolates from medical students in Cartagena, Colombia

Staphylococcus aureus (SA) remains a major cause of nosocomial and community-acquired infections worldwide. Nasal carriage of this bacterium among hospital personnel constitutes an important source for nosocomial infections. A cross-sectional study enrolling the whole medical student population (n=387) of the School of Medicine at the Universidad de Cartagena, Colombia, was conducted to evaluate the carriage rates of both methicillin sensitive- and methicillin resistant-SA, the frequency of Panton-Valentine leukocidin genes in the isolates, and risk factors associated with carriage in this selected population. After signing an informed consent, participants completed a survey related to possible risk factors for colonization, and nasal swabs were collected from anterior nares. Staphylococcus aureus strains isolated from carriers were subjected to DNA extraction and PCR assays to determine the presence of MecA and Panton-Valentine leukocidin genes. Typing of the staphylococcal chromosomal cassette was performed for methicillin resistant strains. Molecular analysis was performed for only one strain per carrier. Prevalence of carriage for methicillin sensitive- and methicillin resistant-SA was 25% and 1.6% respectively. Most of the methicillin resistant isolates carried the staphylococcal chromosomal cassette type IV and the genes for Panton-Valentine leukocidin. To determine carrier types among medical students, each participant was subjected to four additional swabs, each taken two weeks apart. 9.8% persistent carriers, 53.1% intermittent carriers, and 37.1% non-carriers of SA were found. There was no association between risk factors analyzed and carriage of the bacterium. The study was conducted from April to September 2009 and found a persistent carriage of methicillin resistant-SA strains bearing the genes for Panton-Valentine leukocidin among medical students, evidencing the potential contribution of this portion of healthcare personnel either to the spread or introduction of these strains into the healthcare environment.

Recurrent furunculosis: a review of the literature

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasing in incidence and manifests as skin and soft tissue infections including furuncles. The majority of studies have focused on the epidemiology of single furuncles and not recurrent disease. There is a lack of data concerning the incidence of furunculosis outside the U.S.A.

OBJECTIVES

This report reviews the literature of recurrent furunculosis and the impact of CA-MRSA on the disease.

METHODS

Article citations were searched within PubMed. Search terms used were 'furunculosis', 'recurrent furunculosis', 'skin abscess' and 'recurrent boils'. Articles were discarded if they did not refer to furunculosis secondary to S. aureus.

RESULTS

A total of 1515 articles were initially retrieved with the term 'furunculosis', 77 with the term 'recurrent furunculosis', 2778 with the term 'skin abscess', and 1526 with the term 'recurrent boils'. After excluding articles not referring to S. aureus furunculosis, 86 articles were included for this review.

CONCLUSIONS

Furunculosis is increasing within the U.S.A. secondary to the CA-MRSA epidemic and the resistant organism's close association with the Panton-Valentine leucocidin (PVL) virulence factor. PVL is associated with follicular infections in general, having its strongest association with furunculosis and its recurrence. The majority of furuncles in the U.S.A. are caused by CA-MRSA, while elsewhere in the world they are caused by methicillin-sensitive S. aureus. Nasal carriage of S. aureus is the primary risk factor for recurrent furunculosis and occurs in 60% of individuals.

Clinical features and risk factors of mortality for bacteremia due to community-onset healthcare-associated methicillin-resistant S. aureus

Studies comparing adult community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and community-onset healthcare-associated MRSA (COHCA MRSA bacteremia have not been available. From 1 January 2010 through 30 October 2010, a prospective observational program was conducted among all patients aged >16 years with positive Staphylococcus aureus blood cultures within 48 h after their arrival at the emergency department of our hospital. Clinical course of infection and infection foci of bacteremia were evaluated. Resistance to oxacillin was confirmed with the presence of mecA gene examined by polymerase chain reaction. Presence of TSST-1, PVL gene, SCCmec elements (I-V), mecA gene, and multilocus sequence typing were identified through methods described elsewhere. Univariate and multivariate analysis revealed that chronic renal failure was significantly more common in COHCA-MRSA than in CA-MRSA. In addition, APACHE III score was significantly higher in COHCA-MRSA than in CA-MRSA. Both the 7-day and 30-day mortality rates in COHCA-MRSA, 14.6% (7/48) and 29.2% (14/48), respectively, were higher than those in CA-MRSA without a significant difference. SCCmec II was more common in COHCA-MRSA, but SCCmecVT was more common in CA-MRSA. The majority of MRSA isolates belonged to ST59, ST239, and ST5. ST59 was significantly more common in CA-MRSA, while ST239 was nearly equally common in both CA-MRSA and COHCA-MRSA. SCCmec III and II isolates were the first and second most resistant to the antibiotics commonly used for S. aureus, whereas SCCmecVT isolates were the most susceptible to these antibiotics. We conclude that, although both CA-MRSA and COHCA-MRSA bacteremia had community onset, these 2 MRSA infections were different in underlying diseases, risk of mortality, SCCmec types, sequence types, and antimicrobial susceptibility. It is more appropriate to understand the MRSA pathogen and clinical features based on etiology and ST types than based on the location of disease onset. CA-MRSA and HCA-MRSA should be differentiated also based on etiology and ST types, in addition to location of acquisition.

Laboratory maintenance of methicillin-resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus is an important bacterial pathogen in the hospital and community settings, especially Staphylococcus aureus clones that exhibit methicillin-resistance (MRSA). Many strains of S. aureus are utilized in the laboratory, underscoring the genetic differences inherent in clinical isolates. S. aureus grows quickly at 37°C with aeration in rich media (e.g., BHI) and exhibits a preference for glycolytic carbon sources. Furthermore, S. aureus has a gold pigmentation, exhibits β-hemolysis, and is catalase and coagulase positive. The four basic laboratory protocols presented in this unit describe how to culture S. aureus on liquid and solid media, how to identify S. aureus strains as methicillin resistant, and how to generate a freezer stock of S. aureus for long-term storage.

Household risk factors for colonization with multidrug-resistant Staphylococcus aureus isolates

Antimicrobial resistance, particularly in pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), limits treatment options and increases healthcare costs. To understand patient risk factors, including household and animal contact, potentially associated with colonization with multidrug-resistant MRSA isolates, we performed a prospective study of case patients colonized with MRSA on admission to a rural tertiary care hospital. Patients were interviewed and antimicrobial resistance patterns were tested among isolates from admitted patients colonized with MRSA in 2009-10. Prevalence of resistance was compared by case-patient risk factors and length-of-stay outcome among 88 MRSA case patients. Results were compared to NHANES 2003-04. Overall prevalence of multidrug resistance (non-susceptibility to ≥ four antimicrobial classes) in MRSA nasal isolates was high (73%) and was associated with a 1.5-day increase in subsequent length of stay (p = 0.008). History of hospitalization within the past six months, but not antimicrobial use in the same time period, was associated with resistance patterns. Within a subset of working-age case patients without recent history of hospitalization, animal contact was potentially associated with multidrug resistance. History of hospitalization, older age, and small household size were associated with multidrug resistance in NHANES data. In conclusion, recent hospitalization of case patients was predictive of antimicrobial resistance in MRSA isolates, but novel risk factors associated with the household may be emerging in CA-MRSA case patients. Understanding drivers of antimicrobial resistance in MRSA isolates is important to hospital infection control efforts, relevant to patient outcomes and to indicators of the economic burden of antimicrobial resistance.

The role of the Panton-Valentine leucocidin toxin in staphylococcal disease: a systematic review and meta-analysis

BACKGROUND

Invasive community-onset staphylococcal disease has emerged worldwide associated with Panton-Valentine leucocidin (PVL) toxin. Whether PVL is pathogenic or an epidemiological marker is unclear. We investigate the role of PVL in disease, colonisation, and clinical outcome.

METHODS

We searched Medline and Embase for original research reporting the prevalence of PVL genes among Staphylococcus aureus pneumonia, bacteraemia, musculoskeletal infection, skin and soft-tissue infection, or colonisation published before Oct 1, 2011. We calculated odds ratios (ORs) to compare patients with PVL-positive colonisation and each infection relative to the odds of PVL-positive skin and soft-tissue infection. We did meta-analyses to estimate odds of infection or colonisation with a PVL-positive strain with fixed-effects or random-effects models, depending on the results of tests for heterogeneity.

RESULTS

Of 509 articles identified by our search strategy, 76 studies from 31 countries met our inclusion criteria. PVL strains are strongly associated with skin and soft-tissue infections, but are comparatively rare in pneumonia (OR 0·37, 95% CI 0·22-0·63), musculoskeletal infections (0·44, 0·19-0·99), bacteraemias (0·10, 0·06-0·18), and colonising strains (0·07, 0·01-0·31). PVL-positive skin and soft-tissue infections are more likely to be treated surgically than are PVL-negative infections, and children with PVL-positive musculoskeletal disease might have increased morbidity. For other forms of disease we identified no evidence that PVL affects outcome.

INTERPRETATION

PVL genes are consistently associated with skin and soft-tissue infections and are comparatively rare in invasive disease. This finding challenges the view that PVL mainly causes invasive disease with poor prognosis. Population-based studies are needed to define the role of PVL in mild, moderate, and severe disease and to inform control strategies.

FUNDING

None.

Methicillin-resistant Staphylococcus aureus bloodstream infection: risk factors and clinical outcome in non-intensive-care units

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is spread out in hospitals across different regions of the world and is regarded as the major agent of nosocomial infections, causing infections such as skin and soft tissue pneumonia and sepsis. The aim of this study was to identify risk factors for methicillin-resistance in Staphylococcus aureus bloodstream infection (BSI) and the predictive factors for death.

METHODS

A retrospective cohort of fifty-one patients presenting bacteraemia due to S. aureus between September 2006 and September 2008 was analysed. Staphylococcu aureus samples were obtained from blood cultures performed by clinical hospital microbiology laboratory from the Uberlândia Federal University. Methicillinresistance was determined by growth on oxacillin screen agar and antimicrobial susceptibility by means of the disk diffusion method.

RESULTS

We found similar numbers of MRSA (56.8%) and methicillin-susceptible Staphylococcus aureus (MSSA) (43.2%) infections, and the overall hospital mortality ratio was 47%, predominantly in MRSA group (70.8% vs. 29.2%) (p=0.05). Age (p=0.02) was significantly higher in MRSA patients as also was the use of central venous catheter (p=0.02). The use of two or more antimicrobial agents (p=0.03) and the length of hospital stay prior to bacteraemia superior to seven days (p=0.006) were associated with mortality. High odds ratio value was observed in cardiopathy as comorbidity.

CONCLUSIONS

Despite several risk factors associated with MRSA and MSSA infection, the use of two or more antimicrobial agents was the unique independent variable associated with mortality.

Community-acquired methicillin-resistant Staphylococcus aureus from skin and soft tissue infections (in a sample of Egyptian population): analysis of mec gene and staphylococcal cassette chromosome

BACKGROUND

Staphylococcus aureus has been recognized as an important pathogen associated with inpatients and community infections. Community-acquired methicillin-resistant S. aureus (CA-MRSA) infections commonly present as skin and soft-tissue infections (SSTIs). Treatment often includes incision and drainage with or without adjunctive antibiotics.

OBJECTIVES

This study aimed to identify CA-MRSA infections both phenotypically and genotypically, to determine their spectrum of antibiotic resistance, and to establish the best scheme for molecular distinction between hospital-acquired MRSA (HA-MRSA) and CA-MRSA by staphylococcal cassette chromosome mec (SCCmec) typing and detection of Panton Valentine leukocidin (PVL).

MATERIALS

50 swabs, from skin and soft tissue of infected lesions of outpatients attending the dermatology department of the Medical School, Alexandria University, were collected. Additionally, a nasal swab was taken from every participant.

METHODS

Collection of swabs from the infected skin and soft tissues, followed by laboratory testing to phenotypically and genotypically identify MRSA. Also, nasal swabs were taken from every patient to identify MRSA colonization.

RESULTS

Staphylococcus aureus strains were identified in 38 (76%) of the 50 clinical isolates. 18 (47.37%) out of the 38 S. aureus strains were resistant to oxacillin and cefoxitin discs, were penicillin binding protein 2a (PBP2a) producers, and were initially diagnosed as MRSA. All of the 18 strains were definitively diagnosed as MRSA by mecA gene detection using real time PCR, while only six (33.33%) strains were PVL positive. Using the sets of primers of Zhang et al.: nine (50%) out of the 18 CA-MRSA strains were SCCmec type V, and one (5.56%) was SCCmec type IVc. Then, using the set of primers by Oliveira et al., two (25%) out of the eight untypable MRSA strains were found to be SCCmec type IV, and six (75%) remained untypable.

CONCLUSIONS

CA-MRSA must be considered when treating skin and soft tissue infections, especially in developing countries. Empirical use of agents active against CA-MRSA is warranted for patients presenting with serious SSTIs.

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.

Molecular and phenotypic characteristics of healthcare- and community-associated methicillin-resistant Staphylococcus aureus at a rural hospital

Background

While methicillin-resistant Staphylococcus aureus (MRSA) originally was associated with healthcare, distinct strains later emerged in patients with no prior hospital contact. The epidemiology of MRSA continues to evolve.

Methods

To characterize the current epidemiology of MRSA-colonized patients entering a hospital serving both rural and urban communities, we interviewed patients with MRSA-positive admission nasal swabs between August 2009 and March 2010. We applied hospitalization risk factor, antimicrobial resistance phenotype, and multi-locus sequence genotype (MLST) classification schemes to 94 case-patients.

Results

By MLST analysis, we identified 15 strains with two dominant clonal complexes (CCs)–CC5 (51 isolates), historically associated with hospitals, and CC8 (27 isolates), historically of community origin. Among patients with CC5 isolates, 43% reported no history of hospitalization within the past six months; for CC8, 67% reported the same. Classification by hospitalization risk factor did not correlate strongly with genotypic classification. Sensitivity of isolates to ciprofloxacin, clindamycin, or amikacin was associated with the CC8 genotype; however, among CC8 strains, 59% were resistant to ciprofloxacin, 15% to clindamycin, and 15% to amikacin.

Conclusions

Hospitalization history was not a strong surrogate for the CC5 genotype. Conversely, patients with a history of hospitalization were identified with the CC8 genotype. Although ciprofloxacin, clindamycin, and amikacin susceptibility distinguished CC8 strains, the high prevalence of ciprofloxacin resistance limited its predictive value. As CC8 strains become established in healthcare settings and CC5 strains disseminate into the community, community-associated MRSA definitions based on case-patient hospitalization history may prove less valuable in tracking community MRSA strains.

Antibacterial resistance, genes encoding toxins and genetic background among Staphylococcus aureus isolated from community-acquired skin and soft tissue infections in France: a national prospective survey

The epidemiology of staphylococcal community-acquired skin and soft tissues infections (CA-SSTIs) has changed dramatically. We described prospectively the characteristics of the Staphylococcus aureus isolated from 71 non-teaching French hospitals and implicated in CA-SSTIs: antimicrobial susceptibility (mecA polymerase chain reaction [PCR], disk diffusion method), virulence factor gene (sea, tst, pvl) prevalence and genetic background (agr allele). During November 2006, 235 strains were collected (wound infection: 51%, abscess: 21%, whitlow: 8%, diabetic foot: 7%, furunculosis: 3%). sea, tst and pvl were identified in 22.1, 13.2 and 8.9% strains, respectively. agr allele 1 was the most frequently encountered genetic background, whatever the methicillin susceptibility. Among the 34 methicillin-resistant S. aureus (MRSA, 14.5% of all S. aureus), only one strain (2.9%) harboured pvl (belonging to the European ST80 clone), four (11.8%) tst (belonging to two endemic French clones) and 18 (52.9%) sea gene (mainly the Lyon clone). According to their in vitro activity, pristinamycin or trimethoprim/sulfamethoxazole could be considered as first-choice antibiotics. To date, the international pvl-positive MRSA clones have not spread in France. MRSA strains isolated from putative CA-SSTIs exhibited a genetic and phenotypic background of hospital-acquired (HA) clones. National survey should be continued, in order to monitor the emergence of virulent clones.

Detection of Staphylococcus aureus with a fluorescence in situ hybridization that does not require lysostaphin

To detect with whole-cell fluorescence in situ hybridization (FISH), Staphylococcus aureus is typically permeabilized with lysozyme and lysostaphin. We tested whether it was feasible to detect S. aureus and differentiate it from Staphylococcus epidermidis with lysozyme-only permeabilization. We compared lysozyme permeabilization to S. aureus permeabilized with lysozyme in combination with lysostaphin. It was determined that S. aureus treated with agarose, methanol, and lysozyme could be detected with FISH. The 1  hr protocol is a useful alternative to conventional FISH.

Community-associated meticillin-resistant Staphylococcus aureus strains as a cause of healthcare-associated infection

Community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) was first noticed as a cause of infection in community-based individuals without healthcare contact. As the global epidemic of CA-MRSA has continued, CA-MRSA strain types have begun to emerge as a cause of healthcare-associated infections (HAIs) and hospital outbreaks have occurred worldwide. In areas where CA-MRSA clones have become established with high prevalence, for example USA300 (ST8-IV) in the USA, CA-MRSA are beginning to supplant or overtake traditional healthcare-associated MRSA strains as causes of HAI. The emergence of CA-MRSA as a cause of HAI puts a wider group of hospitalised patients, healthcare workers and their community contacts potentially at risk of MRSA infection. It also exposes CA-MRSA strains to the selective pressure of antibiotic use in hospitals, potentially resulting in increased antibiotic resistance, challenges traditional definitions of CA-MRSA and hampers control efforts due to the constant re-introduction of MRSA from an emerging community reservoir. There is thus an urgent need to clarify the definitions, prevalence and epidemiology of CA-MRSA and to develop systems for the identification and control of these organisms in the community, in hospitals and other healthcare facilities, and at the community-hospital interface.

Screening of Staphylococcus aureus nasal strains isolated from medical students for toxin genes

Three hundred twenty-one students (156 students with no clinical exposure and 165 students with clinical exposure) were screened for nasal colonization by Staphylococcus aureus; 20.9% of students were S. aureus nasal carriers, and 40.3% of S. aureus isolates harbored toxin genes. The most prevalent genes were tst (15.0 %) and sec (13.4 %). Isolates with multiple genes were only found among clinical students (p = 0.045). Six of 11 PFGE clones were positive for toxin genes. Methicillin-resistant (MRSA) isolates were only detected in the clinical students (4.5 %). The exposure of students to the hospital environment neither radically increased S. aureus nasal carriage, nor the frequency of clinically important toxin gene presence, but it could have influenced the positive selection of toxigenic MRSA strains.

Diagnostic and therapeutic evaluation of community-acquired methicillin-resistant Staphylococcus Aureus (MRSA) skin and soft tissue infections in the emergency department

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections commonly present as skin and soft-tissue infections (SSTIs). Treatment often includes incision and drainage with or without adjunctive antibiotics. Emergency department (ED) pharmacists wished to provide specific data to emergency physicians to better inform antibiotic choices for patients with SSTIs.

STUDY OBJECTIVES

The objectives of this study were to describe local susceptibility trends of CA-MRSA isolates obtained from patients with SSTIs and describe diagnostic and empiric therapeutic management of CA-MRSA SSTIs among ED health care providers at University of Utah Hospitals and Clinics.

METHODS

Susceptibility of all unique CA-MRSA SSTI isolates for 2008 were identified and compiled into an antibiogram. ED providers evaluated their diagnostic and treatment habits using a self-assessment questionnaire, which was verified against charted information documented in the electronic medical records for patients presenting to the ED with a CA-MRSA SSTI.

RESULTS

The ED antibiogram indicated that 57/58 (98%) CA-MRSA SSTI isolates were susceptible to sulfamethoxazole/trimethoprim (SMX/TMP); 50/58 (86%) isolates were susceptible to tetracycline, and 47/58 (81%) isolates were susceptible to clindamycin. Incision and drainage were performed in 23/25 (92%) patient cases, which was consistent with providers' perceived habits (100%). SMX/TMP monotherapy was preferred among 23/35 (66%) providers, however, SMX/TMP combined with cephalexin was the antibiotic regimen prescribed in 9/22 (41%) patient cases.

CONCLUSIONS

Cephalexin was often added to cover for potential cellulitis due to Streptococcus spp., however, the surrounding erythema may simply be an extension of the CA-MRSA infection. Department-specific antibiograms are useful in guiding empiric antibiotic selection and may help providers judiciously prescribe antibiotics only when necessary.

Surgical site infections: incidence and trends at a community teaching hospital

BACKGROUND

There has been increased national attention on methicillin-resistant Staphylococcus aureus (MRSA) and surgical site infections (SSIs) highlighted by the media, the public, and federal agencies. It was therefore considered important to analyze the trends and incidence of inpatient detected SSIs and associated resistant organisms at our own institution.

METHODS

The analysis reflects the cultures and sensitivities of SSI on the surgical services at Monmouth Medical Center, a 527-bed community teaching hospital, from January 2003 through December 2007. The SSIs included in the study were those detected in hospitalized patients.

RESULTS

There were 312 surgical patients who developed SSIs. Contrary to observed national trends, our study demonstrated a statistically significant decrease in the incidence of MRSA among all the surgical services. We also noted a statistically significant decrease trend of SSIs in orthopedic surgery. The 312 patients' cultures yielded 399 bacterial strains. The most common strains varied with the service. Overall, the most common isolate identified was Staphylococcus species, numbering 143% or 35.8% of all isolates. MRSA was identified in 46 SSIs and 8 SSIs were positive for vancomycin-resistant enterococci (VRE).

CONCLUSIONS

Only a hospital-specific SSI analysis can help focus improvement with clinical impact. The scrutiny of SSI analysis has highlighted SSI problems in the pediatric and orthopedic surgery services that have been addressed.

Superantigen gene profiles and presence of exfoliative toxin genes in community-acquired meticillin-resistant Staphylococcus aureus isolated from Chinese children

This study aimed to evaluate the distribution of superantigen gene profiles and the presence of exfoliative toxin genes in community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) isolated from Chinese children, and simultaneously to assess virulence gene profiles and genetic background. Of the CA-MRSA isolates, 88.9 % (88/99) harboured toxin genes, with sek as the most frequent toxin gene (62.6 %), followed by seq (61.6 %), seb (60.6 %) and sea (35.4 %). The eta gene was detected only in one ST398-IVa-spa t034 strain. The sed and etd genes were not found in any of the isolates tested. A total of 38 virulence genotypes were observed, of which the genotype seb-sek-seq (27.3 %, 24/88) comprised the majority, followed by sea-seb-sek-seq (18.2 %, 16/88). The enterotoxin gene cluster including seg-sei-sem-sen-seo-seu predominated at a rate of 15.1 %. The relationship among toxin genotypes, toxin genes encoding profiles of mobile genetic elements and genetic background was analysed. Among 66 clonal complex (CC) 59 isolates, 87.9 % (58/66) were positive for toxin genes, and 75.8 % (50/66) harboured the toxin gene combination seb-sek-seq. Among seb-sek-seq-positive CC59 strains, 42.0 % (21/50) also carried the sea gene. CC59 corresponded exclusively to accessory gene regulator 1 (agr-1). The data presented here enhance our current knowledge on the virulence determinants of CA-MRSA.

Activity of moxifloxacin against intracellular community-acquired methicillin-resistant Staphylococcus aureus: comparison with clindamycin, linezolid and co-trimoxazole and attempt at defining an intracellular susceptibility breakpoint

BACKGROUND

Co-trimoxazole, clindamycin and linezolid are used to treat community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, but little is known about intracellular activity. Moxifloxacin is active against intracellular methicillin-susceptible S. aureus (MSSA), but CA-MRSA has not been studied.

METHODS

We used 12 clinical CA-MRSA, 1 MSSA overexpressing norA and 2 hospital-acquired MRSA (moxifloxacin MICs: 0.03 to 4 mg/L). Activity was assessed in broth and after phagocytosis by THP-1 macrophages or keratinocytes {concentration-dependent experiments [24 h of incubation] to determine relative potencies [EC(50)], static concentrations [C(s)] and maximal relative efficacies [E(max) (change in log(10) cfu compared with initial inoculum)] and time-dependent experiments [0-72 h] at human C(max)}.

RESULTS

Concentration-dependent experiments: in broth, EC(50) and C(s) were correlated with the MIC for all antibiotics, but moxifloxacin achieved significantly (P < 0.01) greater killing (more negative E(max)) than the comparators; and in THP-1 cells and keratinocytes, moxifloxacin acted more slowly but still reached a near bactericidal effect (2 to 3 log(10) cfu decrease) at 24 h with unchanged EC(50) and C(s) as long as its MIC was ≤0.125 mg/L (recursive partitioning analysis). Clindamycin and linezolid were static, and co-trimoxazole was unable to suppress the intracellular growth of CA-MRSA. At human C(max) in broth, moxifloxacin killed more rapidly and more extensively (≥5 log(10) cfu decrease at 10 h) than clindamycin (4 log(10) cfu at 48 h) or co-trimoxazole and linezolid (1-2 log(10) cfu at 72 h).

CONCLUSIONS

Moxifloxacin is active against both extracellular and intracellular CA-MRSA if the MIC is low, and is more effective than clindamycin, co-trimoxazole and linezolid.

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.

Bacterial septic arthritis in adults

Symptoms and signs of septic arthritis are an important medical emergency, with high morbidity and mortality. We review the changing epidemiology of septic arthritis of native joints in adults, encompassing the increasing frequency of the disorder and its evolving antibiotic resistance. We discuss various risk factors for development of septic arthritis and examine host factors (tumour necrosis factor alpha, interleukins 1 and 10) and bacterial proteins, toxins, and enzymes reported to be important determinants of pathogenesis in mouse models. Diagnosis of disease is largely clinical, guided by investigations and the opinion of skilled clinicians. We emphasise the need for timely medical and surgical intervention-most importantly, through diagnostic aspiration of relevant joints, choice of suitable antibiotic, and appropriate supportive measures. Management is growing in complexity with the advent of novel and antibiotic-resistant causative microorganisms and within the current climate of increased immunosuppression. Findings from animal models and patients are shedding light on disease pathogenesis and the possibility of novel adjunctive treatments, including systemic corticosteroids, cytokines and anticytokines, and bisphosphonates.