Novel bacterial metabolite merochlorin A demonstrates in vitro activity against multi-drug resistant methicillin-resistant Staphylococcus aureus

Background

We evaluated the in vitro activity of a merochlorin A, a novel compound with a unique carbon skeleton, against a spectrum of clinically relevant bacterial pathogens and against previously characterized clinical and laboratory Staphylococcus aureus isolates with resistance to numerous antibiotics.

Methods

Merochlorin A was isolated and purified from a marine-derived actinomycete strain CNH189. Susceptibility testing for merochlorin A was performed against previously characterized human pathogens using broth microdilution and agar dilution methods. Cytotoxicity was assayed in tissue culture assays at 24 and 72 hours against human HeLa and mouse sarcoma L929 cell lines.

Results

The structure of as new antibiotic, merochlorin A, was assigned by comprehensive spectroscopic analysis. Merochlorin A demonstrated in vitro activity against Gram-positive bacteria, including Clostridium dificile, but not against Gram negative bacteria. In S. aureus, susceptibility was not affected by ribosomal mutations conferring linezolid resistance, mutations in dlt or mprF conferring resistance to daptomycin, accessory gene regulator knockout mutations, or the development of the vancomycin-intermediate resistant phenotype. Merochlorin A demonstrated rapid bactericidal activity against MRSA. Activity was lost in the presence of 20% serum.

Conclusions

The unique meroterpenoid, merochlorin A demonstrated excellent in vitro activity against S. aureus and C. dificile and did not show cross-resistance to contemporary antibiotics against Gram positive organisms. The activity was, however, markedly reduced in 20% human serum. Future directions for this compound may include evaluation for topical use, coating biomedical devices, or the pursuit of chemically modified derivatives of this compound that retain activity in the presence of serum.     

Cross Border Comparison of MRSA Bacteraemia between The Netherlands and North Rhine-Westphalia (Germany): A Cross-Sectional Study

Background

We describe the impact of methicillin-resistant Staphylococcus aureus (MRSA) in two neighbouring regions in Europe with a comparable population size, North Rhine-Westphalia (NRW) in Germany and the Netherlands.

Methodology/Principal Findings

We compared the occurrence of MRSA in blood cultures from surveillance systems. In the Netherlands in 2009, 14 of 1,510 (0.9%) Staphylococcus aureus bacteraemia episodes under surveillance were MRSA. Extrapolation using the number of clinical admissions results in a total of 29 MRSA bacteraemia episodes in the Netherlands or 1.8 episodes per 1,000,000 inhabitants. In 2010 in NRW, 1,029 MRSA bacteraemias were reported, resulting in 57.6 episodes of MRSA bacteraemia per 1,000,000 inhabitants: a 32-fold higher incidence than in the Netherlands.

Conclusion/Significance

Based on an estimated attributable mortality of 15%, the Dutch approach would save approximately 150 lives per year by the prevention of bacteraemia only.     

Geographic Distribution of Staphylococcus aureus Causing Invasive Infections in Europe: A Molecular-Epidemiological Analysis

Background

Staphylococcus aureus is one of the most important human pathogens and methicillin-resistant variants (MRSAs) are a major cause of hospital and community-acquired infection. We aimed to map the geographic distribution of the dominant clones that cause invasive infections in Europe.

Methods and Findings

In each country, staphylococcal reference laboratories secured the participation of a sufficient number of hospital laboratories to achieve national geo-demographic representation. Participating laboratories collected successive methicillin-susceptible (MSSA) and MRSA isolates from patients with invasive S. aureus infection using an agreed protocol. All isolates were sent to the respective national reference laboratories and characterised by quality-controlled sequence typing of the variable region of the staphylococcal spa gene (spa typing), and data were uploaded to a central database. Relevant genetic and phenotypic information was assembled for interactive interrogation by a purpose-built Web-based mapping application. Between September 2006 and February 2007, 357 laboratories serving 450 hospitals in 26 countries collected 2,890 MSSA and MRSA isolates from patients with invasive S. aureus infection. A wide geographical distribution of spa types was found with some prevalent in all European countries. MSSA were more diverse than MRSA. Genetic diversity of MRSA differed considerably between countries with dominant MRSA spa types forming distinctive geographical clusters. We provide evidence that a network approach consisting of decentralised typing and visualisation of aggregated data using an interactive mapping tool can provide important information on the dynamics of MRSA populations such as early signalling of emerging strains, cross border spread, and importation by travel.

Conclusions

In contrast to MSSA, MRSA spa types have a predominantly regional distribution in Europe. This finding is indicative of the selection and spread of a limited number of clones within health care networks, suggesting that control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful and should therefore be strongly encouraged. Please see later in the article for the Editors'' Summary     

Staphylococcus aureus Bacteraemia in a Tropical Setting: Patient Outcome and Impact of Antibiotic Resistance

Background

Most information on invasive Staphylococcus aureus infections comes from temperate countries. There are considerable knowledge gaps in epidemiology, treatment, drug resistance and outcome of invasive S. aureus infection in the tropics.

Methods

A prospective, observational study of S. aureus bacteraemia was conducted in a 1000-bed regional hospital in northeast Thailand over 1 year. Detailed clinical data were collected and final outcomes determined at 12 weeks, and correlated with antimicrobial susceptibility profiles of infecting isolates.

Principal Findings

Ninety-eight patients with S. aureus bacteraemia were recruited. The range of clinical manifestations was similar to that reported from temperate countries. The prevalence of endocarditis was 14%. The disease burden was highest at both extremes of age, whilst mortality increased with age. The all-cause mortality rate was 52%, with a mortality attributable to S. aureus of 44%. Methicillin-resistant S. aureus (MRSA) was responsible for 28% of infections, all of which were healthcare-associated. Mortality rates for MRSA and methicillin-susceptible S. aureus (MSSA) were 67% (18/27) and 46% (33/71), respectively (p = 0.11). MRSA isolates were multidrug resistant. Only vancomycin or fusidic acid would be suitable as empirical treatment options for suspected MRSA infection.

Conclusions

S. aureus is a significant pathogen in northeast Thailand, with comparable clinical manifestations and a similar endocarditis prevalence but higher mortality than industrialised countries. S. aureus bacteraemia is frequently associated with exposure to healthcare settings with MRSA causing a considerable burden of disease. Further studies are required to define setting-specific strategies to reduce mortality from S. aureus bacteraemia, prevent MRSA transmission, and to define the burden of S. aureus disease and emergence of drug resistance throughout the developing world.     

Methicillin-Resistant Staphylococcus aureus (MRSA) Is Increasing in Norway: A Time Series Analysis of Reported MRSA and Methicillin-Sensitive S. aureus Cases, 1997–2010

Background

Accurate estimates of the incidence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections are needed to inform public health policies. In Norway, where both MRSA infection and carriage are notifiable conditions, the reported incidence of MRSA is slowly increasing. However, the proportion of MRSA in relation to all S. aureus isolates is unknown, making it difficult to determine if the rising incidence is real or an artifact of an increasing number of tests performed.

Aim

To characterize recent trends in MRSA infections and obtain a more complete understanding of the MRSA level in Norway.

Methods

All reported cases of MRSA and methicillin-sensitive S. aureus (MSSA) from Oslo County (1997–2010) and Health Region East (2008–2008), representing approximately 11% and 36% of the Norwegian population, respectively, were analyzed using a stochastic time series analysis to characterize trends.

Results

In Oslo County, the proportion of methicillin-resistant cases increased from 0.73% to 3.78% during the study period and was well modeled by an exponential growth with a doubling constant of 5.7 years (95% CI 4.5–7.4 years). In Health Region East, the proportion of MRSA cases increased from 0.4% to 2.1% from 2002 to 2008, with a best-fitting linear increase of 0.26% (95% CI 0.21–0.30%) per year. In both cases, the choice of a linear or exponential model for the time trend produced only marginally different model fits. We found no significant changes due to revised national MRSA guidelines published in June 2009. Significant variations in the increasing time trend were observed in the five hospitals within the region. The yearly reported incidence of MSSA was relatively stable in both study areas although we found seasonal patterns with peaks in August.

Conclusion

The level of MRSA is increasing in Norway, and the proportion of methicillin resistance in all S. aureus isolates are higher than the reported proportion of MRSA in invasive infections.     

Identification of horizontally transferred genes in the genus Colletotrichum reveals a steady tempo of bacterial to fungal gene transfer

Background

Horizontal gene transfer (HGT) is the stable transmission of genetic material between organisms by means other than vertical inheritance. HGT has an important role in the evolution of prokaryotes but is relatively rare in eukaryotes. HGT has been shown to contribute to virulence in eukaryotic pathogens. We studied the importance of HGT in plant pathogenic fungi by identifying horizontally transferred genes in the genomes of three members of the genus Colletotrichum.

Results

We identified eleven HGT events from bacteria into members of the genus Colletotrichum or their ancestors. The HGT events include genes involved in amino acid, lipid and sugar metabolism as well as lytic enzymes. Additionally, the putative minimal dates of transference were calculated using a time calibrated phylogenetic tree. This analysis reveals a constant flux of genes from bacteria to fungi throughout the evolution of subphylum Pezizomycotina.

Conclusions

Genes that are typically transferred by HGT are those that are constantly subject to gene duplication and gene loss. The functions of some of these genes suggest roles in niche adaptation and virulence. We found no evidence of a burst of HGT events coinciding with major geological events. In contrast, HGT appears to be a constant, albeit rare phenomenon in the Pezizomycotina, occurring at a steady rate during their evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-16-2) contains supplementary material, which is available to authorized users.     

Staphylococcus aureus Ocular Infection: Methicillin-Resistance, Clinical Features, and Antibiotic Susceptibilities

Background

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an important public health issue. The study aimed to determine the prevalence of ocular infections caused by MRSA and to identify the clinical characteristics and antibiotic susceptibility of ocular MRSA infections by comparing those of ocular methicillin-sensitive S. aureus (MSSA) infections.

Methodology/Principal Findings

The medical records of the patients (n = 519) with culture-proven S. aureus ocular infections seen between January 1, 1999 and December 31, 2008 in Chang Gung Memorial Hospital were retrospectively reviewed. Two hundred and seventy-four patients with MRSA and 245 with MSSA ocular infections were identified. The average rate of MRSA in S. aureus infections was 52.8% and the trend was stable over the ten years (P value for trend  = 0.228). MRSA ocular infections were significantly more common among the patients with healthcare exposure (P = 0.024), but 66.1% (181/274) patients with MRSA ocular infections had no healthcare exposure. The most common clinical presentation for both MRSA and MSSA ocular infections was keratitis; MRSA and MSSA caused a similar disease spectrum except for lid infections. MRSA was significantly more resistant than MSSA to clindamycin, erythromycin and sulfamethoxazole/trimethoprim (all P<0.001).

Conclusions/significance

We demonstrated a paralleled trend of ocular MRSA infection in a highly prevalent MRSA country by hospital-based survey. Except for lid disorder, MRSA shared similar spectrum of ocular pathology with MSSA. Since S. aureus is a common ocular pathogen, our results raise clinician’s attention to the existence of highly prevalent MRSA.     

Structural equation models to estimate risk of infection and tolerance to bovine mastitis

Background

One method to improve durably animal welfare is to select, as reproducers, animals with the highest ability to resist or tolerate infection. To do so, it is necessary to distinguish direct and indirect mechanisms of resistance and tolerance because selection on these traits is believed to have different epidemiological and evolutionary consequences.

Methods

We propose structural equation models with latent variables (1) to quantify the latent risk of infection and to identify, among the many potential mediators of infection, the few ones that influence it significantly and (2) to estimate direct and indirect levels of tolerance of animals infected naturally with pathogens. We applied the method to two surveys of bovine mastitis in the Walloon region of Belgium, in which we recorded herd management practices, mastitis frequency, and results of bacteriological analyses of milk samples.

Results and discussion

Structural equation models suggested that, among more than 35 surveyed herd characteristics, only nine (age, addition of urea in the rations, treatment of subclinical mastitis, presence of dirty liner, cows with hyperkeratotic teats, machine stripping, pre- and post-milking teat disinfection, and housing of milking cows in cubicles) were directly and significantly related to a latent measure of bovine mastitis, and that treatment of subclinical mastitis was involved in the pathway between post-milking teat disinfection and latent mastitis. These models also allowed the separation of direct and indirect effects of bacterial infection on milk productivity. Results suggested that infected cows were tolerant but not resistant to mastitis pathogens.

Conclusions

We revealed the advantages of structural equation models, compared to classical models, for dissecting measurements of resistance and tolerance to infectious diseases, here bovine mastitis. Using our method, we identified nine major risk factors that were directly associated with an increased risk of mastitis and suggested that cows were tolerant but not resistant to mastitis. Selection should aim at improved resistance to infection by mastitis pathogens, although further investigations are needed due to the limitations of the data used in this study.     

Molecular Characterization of Staphylococcus aureus from Patients with Surgical Site Infections at Mulago Hospital in Kampala,Uganda

Background

The prevalence of Methicillin resistant Staphylococcus aureus (MRSA) is progressively increasing globally with significant regional variation. Understanding the Staphylococcus aureus lineages is crucial in controlling nosocomial infections. Recent studies on S. aureus in Uganda have revealed an escalating burden of MRSA. However, the S. aureus genotypes circulating among patients are not known. Here, we report S. aureus lineages circulating in patients with surgical site infections (SSI) at Mulago National hospital, Kampala, Uganda.

Methods

A cross-sectional study involving 314 patients with SSI at Mulago National Hospital was conducted from September 2011 to April 2012. Pus swabs from the patients’ SSI were processed using standard microbiological procedures. Methicillin sensitive Staphylococcus aureus (MSSA) and MRSA were identified using phenotypic tests and confirmed by PCR-detection of the nuc and mecA genes, respectively. SCCmec genotypes were determined among MRSA isolates using multiplex PCR. Furthermore, to determine lineages, spa sequence based-genotyping was performed on all S. aureus isolates.

Results

Of the 314 patients with SSI, S. aureus accounted for 20.4% (64/314), of which 37.5% (24/64) were MRSA. The predominant SCCmec types were type V (33.3%, 8/24) and type I (16.7%, 4/24). The predominant spa lineages were t645 (17.2%, 11/64) and t4353 (15.6%, 10/64), and these were found to be clonally circulating in all the surgical wards. On the other hand, lineages t064, t355, and t4609 were confined to the obstetrics and gynecology wards. A new spa type (t10277) was identified from MSSA isolate. On multivariate logistic regression analysis, cancer and inducible clindamycin resistance remained as independent predictors of MRSA-SSI.

Conclusion

SCCmec types I and V are the most prevalent MRSA mecA types from the patients’ SSI. The predominant spa lineages (t645 and t4353) are clonally circulating in all the surgical wards, calling for strengthening of infection control practices at Mulago National Hospital.     

Changes in the nasal colonization with methicillin-resistant Staphylococcus aureus in children: 2004-2009

Background

Staphylococcus aureus is an important cause of infection, particularly in persons colonized with this organism. This study compared the annual prevalence and microbiological characteristics of methicillin-resistant S. aureus (MRSA) nasal colonization in Taiwanese children from 2004 through 2009. Risk factors for MRSA were determined for the overall study period.

Methods

Children from birth to ≤14 years of age presenting for health maintenance visits or attending 1 of 57 kindergartens were recruited. Nasal swabs were obtained, and a questionnaire was administered. The prevalence and microbiological characteristics of MRSA colonization were also calculated for two 3-year periods: 2004–2006 and 2007–2009.

Results

Cultures of the anterior nares were positive for S. aureus in 824 (25.8%) of the 3,200 children, and MRSA colonization was found in 371 (11.6%) children. The prevalence of S. aureus colonization decreased from 28.1% in 2004–2006 to 23.3% in 2007–2009 (p<0.01), whereas the prevalence of MRSA colonization increased from 8.1% to 15.1% during this period (p<0.0001). Multivariate analysis revealed that the independent risk factors for MRSA carriage were different for male and female children, and also among age groups. Most MRSA isolates belonged to sequence type 59 (ST59) (86.3%); however, a multiresistant MRSA clone with ST338 background emerged in 2007–2009. Ten (62.5%) of the 16 MRSA isolates expressed the genotypic profile ST338/staphylococcal cassette chromosome mec V_T/Panton-Valentine leukocidin-positive/staphylococcal enterotoxin B-positive, and differed only in their antimicrobial susceptibility patterns.

Conclusion

The prevalence of nasal colonization by MRSA increased among healthy Taiwanese children from 2004–2006 to 2007–2009, despite an overall decrease in the prevalence of nasal colonization by S. aureus. A multiresistant MRSA clone characterized as ST338 was identified from these children.     

Methicillin-Susceptible Staphylococcus aureus as a Predominantly Healthcare-Associated Pathogen: A Possible Reversal of Roles?

Background

Methicillin-resistant Staphylococcus aureus (MRSA) strains have become common causes of skin and soft tissue infections (SSTI) among previously healthy people, a role of methicillin-susceptible (MSSA) isolates before the mid-1990s. We hypothesized that, as MRSA infections became more common among S. aureus infections in the community, perhaps MSSA infections had become more important as a cause of healthcare-associated infection.

Methods

We compared patients, including children and adults, with MRSA and MSSA infections at the University of Chicago Medical Center (UCMC) from all clinical units from July 1, 2004-June 30, 2005; we also compared the genotypes of the MRSA and MSSA infecting bacterial strains.

Results

Compared with MRSA patients, MSSA patients were more likely on bivariate analysis to have bacteremia, endocarditis, or sepsis (p = 0.03), to be an adult (p = 0.005), to be in the intensive care unit (21.9% vs. 15.6%) or another inpatient unit (45.6% vs. 40.7%) at the time of culture. MRSA (346/545) and MSSA (76/114) patients did not differ significantly in the proportion classified as HA-S. aureus by the CDC CA-MRSA definition (p = 0.5). The genetic backgrounds of MRSA and MSSA multilocus sequence type (ST) 1, ST5, ST8, ST30, and ST59 comprised in combination 94.5% of MRSA isolates and 50.9% of MSSA isolates. By logistic regression, being cared for in the Emergency Department (OR 4.6, CI 1.5-14.0, p = 0.008) was associated with MRSA infection.

Conclusion

Patients with MSSA at UCMC have characteristics consistent with a health-care-associated infection more often than do patients with MRSA; a possible role reversal has occurred for MSSA and MRSA strains. Clinical MSSA and MRSA strains shared genotype backgrounds.     

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

Background

0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ∼200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure.

Aims

The aim of this work was to test the biophysically-based hypothesis that ∼200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues.

Methods

A Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue.

Results

We found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp.

Conclusions

As predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin.     

Vancomycin heteroresistance is associated with reduced mortality in ST239 methicillin-resistant Staphylococcus aureus blood stream infections

Background

Despite hVISA infections being associated with vancomycin treatment failure, no previous study has been able to detect a mortality difference between heteroresistant vancomycin intermediate Staphylococcus aureus (hVISA) and vancomycin susceptible Staphylococcus aureus (VSSA) bloodstream infections (BSI).

Methodology

Consecutive methicillin-resistant S. aureus (MRSA) BSI episodes between 1996 and 2008 were reviewed. Patient demographics, clinical presentation, treatment and overall mortality at 30 days were extracted from the medical records. All isolates underwent vancomycin minimum inhibitory concentration (VMIC) testing by broth microdilution and Etest. hVISA was confirmed by population analysis profiling using the area under the curve method (PAP-AUC).

Principal Findings

401 evaluable MRSA BSI episodes were identified over the 12 years. Of these, 46 (11.5%) and 2 (0.5%) were confirmed as hVISA and VISA by PAP-AUC respectively. hVISA predominantly occurred in ST239-like MRSA isolates with high VMIC (2 mg/L). Compared to VSSA, hVISA was associated with chronic renal failure (p<0.001), device related infections (haemodialysis access) (p<0.001) and previous vancomycin usage (p = 0.004). On multivariate analysis, independent predictors of mortality included age, presence of multiple co-morbidities, principal diagnosis, transit to ICU and severity of illness while infection related surgery and hVISA phenotype were associated with increased survival.

Conclusions/Significance

The presence of hVISA is dependent on the appropriate interplay between host and pathogen factors. hVISA in ST239 MRSA is an independent predictor of survival. Whether these findings would be replicated across all MRSA clones is unknown and warrants further study.     

Specificity and Effector Functions of Human RSV-Specific IgG from Bovine Milk

Background

Respiratory syncytial virus (RSV) infection is the second most important cause of death in the first year of life, and early RSV infections are associated with the development of asthma. Breastfeeding and serum IgG have been shown to protect against RSV infection. Yet, many infants depend on bovine milk-based nutrition, which at present lacks intact immunoglobulins.

Objective

To investigate whether IgG purified from bovine milk (bIgG) can modulate immune responses against human RSV.

Methods

ELISAs were performed to analyse binding of bIgG to human respiratory pathogens. bIgG or hRSV was coated to plates to assess dose-dependent binding of bIgG to human Fcγ receptors (FcγR) or bIgG-mediated binding of myeloid cells to hRSV respectively. S. Epidermidis and RSV were used to test bIgG-mediated binding and internalisation of pathogens by myeloid cells. Finally, the ability of bIgG to neutralise infection of HEp2 cells by hRSV was evaluated.

Results

bIgG recognised human RSV, influenza haemagglutinin and Haemophilus influenza. bIgG bound to FcγRII on neutrophils, monocytes and macrophages, but not to FcγRI and FcγRIII, and could bind simultaneously to hRSV and human FcγRII on neutrophils. In addition, human neutrophils and dendritic cells internalised pathogens that were opsonised with bIgG. Finally, bIgG could prevent infection of HEp2 cells by hRSV.

Conclusions

The data presented here show that bIgG binds to hRSV and other human respiratory pathogens and induces effector functions through binding to human FcγRII on phagocytes. Thus bovine IgG may contribute to immune protection against RSV.     

Rhodomyrtone Modulates Innate Immune Responses of THP-1 Monocytes to Assist in Clearing Methicillin-Resistant Staphylococcus aureus

Background

The increasing resistance of Staphylococcus aureus to conventional antibiotics poses a major health problem. Moreover, S. aureus can survive within phagocytes, thus evading some antibiotics and the innate immune response. Rhodomyrtone, a bioactive compound from the leaves of Rhodomyrtus tomentosa, possesses potent antibacterial activity against methicillin-resistant S. aureus (MRSA). This study was to investigate the immunomodulatory effects of rhodomyrtone on THP-1 monocytes in response to MRSA.

Methods

THP-1 monocytes were stimulated with heat-killed MRSA, followed by treatment with rhodomyrtone. The cell pellets were prepared to detect pro-inflammatory molecules using real-time PCR. The supernatants were collected to assess nitric oxide production using Griess assay. Assays for phagocytosis and bacterial killing by THP-1 monocytes were performed to determine if they were affected by rhodomyrtone.

Results

Expression of pro-inflammatory molecules including IL-1β, TNF-α, IL-6, and iNOS was enhanced in THP-1 monocytes stimulated with high doses of heat-killed MRSA (10⁸ to 10⁹ cfu/ml). In contrast, monocytes stimulated with MRSA at lower doses (10⁶ to 10⁷ cfu/ml) did not induce the expression of these cytokines. However, rhodomyrtone significantly increased the expression of pro-inflammatory mediators, IL-6 and iNOS in monocytes stimulated with heat-killed MRSA at low doses, and displayed some anti-inflammatory activity by reducing TNF-α expression in monocytes stimulated with heat-killed MRSA at high doses. Treatment with rhodomyrtone also significantly up-regulated the expression of the key pattern recognition receptors, TLR2 and CD14, in THP-1 monocytes stimulated with heat-killed MRSA at 10⁶ to 10⁹ cfu/ml, while heat-killed MRSA alone did not induce the expression of these molecules. The ability of rhodomyrtone to eliminate MRSA from the monocytes was observed within 24 h after treatment.

Conclusion

Rhodomyrtone enhanced the expression of pattern recognition receptors by monocytes in response to MRSA. Increased expression of these receptors might improve MRSA clearance by modulating pro- and anti-inflammatory cytokine responses.     

Binary IS typing for Staphylococcus aureus

Background

We present an easily applicable test for rapid binary typing of Staphylococcus aureus: binary interspace (IS) typing. This test is a further development of a previously described molecular typing technique that is based on length polymorphisms of the 16S-23S rDNA interspace region of S. aureus.

Methodology/Principal Findings

A novel approach of IS-typing was performed in which binary profiles are created. 424 human and animal derived MRSA and MSSA isolates were tested and a subset of these isolates was compared with multi locus sequence typing (MLST) and Amplified Fragment Length Polymorphism (AFLP). Binary IS typing had a high discriminatory potential and a good correlation with MLST and AFLP.

Conclusions/Significance

Binary IS typing is easy to perform and binary profiles can be generated in a standardized fashion. These two features, combined with the high correlation with MLST clonal complexes, make the technique applicable for large-scale inter-laboratory molecular epidemiological comparisons.     

Surface Microbiology of the iPad Tablet Computer and the Potential to Serve as a Fomite in Both Inpatient Practice Settings as Well as Outside of the Hospital Environment

Background

The use of tablet computers and other touch screen technology within the healthcare system has rapidly expanded. It has been reported that these devices can harbor pathogens in hospitals; however, much less is known about what pathogens they can harbor when used outside the hospital environment compared to hospital practice.

Methods

Thirty iPads belonging to faculty with a variety of practice settings were sampled to determine the presence and quantity of clinically-relevant organisms. Flocked nylon swabs and neutralizer solution were used to sample the surface of each iPad. Samples were then plated on a variety of selective agars for presence and quantity of selected pathogens. In addition, faculty members were surveyed to classify the physical location of their practice settings and usage patterns. Continuous variables were compared via an unpaired Student''s t test with two-tailed distribution; categorical variables were compared with the Fisher''s exact test.

Results

Of the iPads sampled, 16 belonged to faculty practicing within a hospital and 14 belonged to a faculty member practicing outside a hospital. More faculty within the hospital group used their iPads at their practice sites (78.6% vs. 31.3%; p = 0.014) and within patient care areas (71.4% vs. 18.8%; p = 0.009) than the non-hospital group. There were no differences in the presence, absence, or quantity of, any of the pathogens selectively isolated between groups. Problematic nosocomial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and P. aeruginosa were isolated from both hospital and non-hospital faculty iPads.

Conclusions

Gram positive and Gram negative organisms were recovered from the surfaces of iPads regardless of practice setting; these included problematic multidrug-resistant pathogens like MRSA, VRE, and Pseudomonas aeruginosa. Healthcare personnel in all settings should be aware of the potential for tablet computers to serve as a nidus for microorganism transmission.     

The environment as an unrecognized reservoir for community-associated methicillin resistant Staphylococcus aureus USA300: a case-control study

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are spreading, but the source of infections in non-epidemic settings remains poorly defined.

Methods

We carried out a community-based, case-control study investigating socio-demographic risk factors and infectious reservoirs associated with MRSA infections. Case patients presented with CA-MRSA infections to a New York hospital. Age-matched controls without infections were randomly selected from the hospital''s Dental Clinic patient population. During a home visit, case and control subjects completed a questionnaire, nasal swabs were collected from index respondents and household members and standardized environmental surfaces were swabbed. Genotyping was performed on S. aureus isolates.

Results

We enrolled 95 case and 95 control subjects. Cases more frequently reported diabetes mellitus and a higher number of skin infections among household members. Among case households, 53 (56%) were environmentally contaminated with S. aureus, compared to 36 (38%) control households (p = .02). MRSA was detected on fomites in 30 (32%) case households and 5 (5%; p<.001) control households. More case patients, 20 (21%) were nasally colonized with MRSA than were control indexes, 2 (2%; p<.001). In a subgroup analysis, the clinical isolate (predominantly USA300), was more commonly detected on environmental surfaces in case households with recurrent MRSA infections (16/36, 44%) than those without (14/58, 24%, p = .04).

Conclusions

The higher frequency of environmental contamination of case households with S. aureus in general and MRSA in particular implicates this as a potential reservoir for recolonization and increased risk of infection. Environmental colonization may contribute to the community spread of epidemic strains such as USA300.