Trends of the Use of Anti-methicillin-Resistant Staphylococcus aureus Agents in Japan Based on Sales Data from 2006 to 2015.

Patterns of the use of anti-methicillin-resistant Staphylococcus aureus (MRSA) agents in Japan might be influenced by the launch of new anti-MRSA agents, the publication of relevant guidelines, and the increase in the number of generic medicines. However, as anti-MRSA agents are included in multiple anatomical therapeutic chemical classifications, such as glycopeptides and aminoglycosides, the trends of the use of individual anti-MRSA agents remain unclear. Here, we aimed to clarify the trends of anti-MRSA agent use in Japan from 2006 to 2015 based on sales data. Total anti-MRSA agent use was found to have significantly increased from 2006 to 2015 (Pfor trend = 0.027, r = 0.00022). Individual trends for vancomycin (VCM), daptomycin, and linezolid (LZD) use showed significant increases, while those for arbekacin (ABK) and teicoplanin (TEIC) showed decreases. In addition, oral LZD use significantly increased, while there was no significant change in intravenous LZD use. The ratio of oral LZD use to total LZD use increased from 25.5% in 2006 to 39.9% in 2015. Meanwhile, TEIC and ABK use decreased, while VCM use increased, following the launch of generic medicines. These results might reflect the status of guideline compliance, the launch of new anti-MRSA agents, and the decline in the sales promotion of the original medicines. It is extremely important to investigate trends for the use of not only different antibiotic groups but also individual antibiotics to develop and implement antimicrobial resistance countermeasures.

Local and Transboundary Transmissions of Methicillin-Resistant Staphylococcus aureus Sequence Type 398 through Pig Trading.

Livestock-associated methicillin-resistant Staphylococcus aureus sequence type (ST) 398 (LA-MRSA ST398) is a genetic lineage for which pigs are regarded as the main reservoir. An increasing prevalence of LA-MRSA ST398 has been reported in areas with high livestock density throughout Europe. In this study, we investigated the drivers contributing to the introduction and spread of LA-MRSA ST398 through the pig farming system in southern Italy. Whole-genome sequencing (WGS) of LA-MRSA ST398 isolates collected in 2018 from pigs (n = 53) and employees (n = 14) from 10 farms in the Calabria region of Italy were comparatively analyzed with previously published WGS data from Italian ST398 isolates (n = 45), an international ST398 reference collection (n = 89), and isolates from Danish pig farms (n = 283), which are the main suppliers of pigs imported to Italy. Single-nucleotide polymorphisms (SNP) were used to infer isolate relatedness, and these data were used together with data from animal trading to identify factors contributing to LA-MRSA ST398 dissemination. The analyses support the existence of two concurrent pathways for the spread of LA-MRSA ST398 in southern Italy: (i) multiple introductions of LA-MRSA ST398 through the import of colonized pigs from other European countries, including Denmark and France, and (ii) the spread of distinct clones dependent on local trading of pigs between farms. Phylogenetically related Italian and Danish LA-MRSA ST398 isolates shared extensive similarities, including carriage of antimicrobial resistance genes. Our findings highlight the potential risk of transboundary transmission of antimicrobial-resistant bacterial clones with a high zoonotic potential during import of pigs from countries with high LA-MRSA prevalence.IMPORTANCE Over the past decade, livestock-associated methicillin-resistant Staphylococcus aureus sequence type 398 (LA-MRSA ST398) has spread among pig holdings throughout Europe, in parallel with the increased incidence of infections among humans, especially in intensive pig farming regions. Despite the growing prevalence of LA-MRSA ST398 in Italian pig farms, the transmission dynamics of this clone in Italy remains unclear. This work provides genome-based evidence to suggest transboundary LA-MRSA ST398 transmission through trading of colonized pigs between European countries and Italy, as well as between farms in the same Italian region. Our findings show that both international trading and local trading of colonized pigs are important factors contributing to the global spread of LA-MRSA ST398 and underscore the need for control measures on and off the farm to reduce the dissemination of this zoonotic pathogen.

Clinical and economic impact of methicillin-resistant Staphylococcus aureus: a multicentre study in China.

Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious threat to global health. In China, the proportion of S. aureus isolates that were MRSA was 44.6% in 2014. The clinical and economic impact of MRSA in China remains largely uninvestigated. This study aims to compare the differences in hospital costs, length of hospital stay, and hospital mortality rate between MRSA and methicillin-susceptible S. aureus (MSSA) colonization or infection and between MRSA cases and those without an S. aureus infection. A retrospective and multicentre study was conducted in four tertiary hospitals in China between 2013 and 2015. Inpatient characteristics and hospital costs were collected from electronic medical records. We conducted propensity score matching (PSM) to eliminate selection bias by balancing the potential confounding variables between the two groups. The main indicators included hospital costs, length of hospital stay, and hospital mortality rate. A total of 1,335 inpatients with MRSA, 1,397 with MSSA, and 33,606 without an S. aureus infection were included. PSM obtained 954 and 1,313 pairs between the MRSA and MSSA groups and between the MRSA and S. aureus-free groups, respectively. After PSM, MRSA colonization or infection is associated with an increased total hospital cost ranging from $3,220 to $9,606, an excess length of hospital stay of 6 days-14 days, and an attributable hospital mortality rate of 0-3.58%. Between the MRSA and MSSA groups, MRSA colonization or infection was significantly associated with a higher total hospital cost and longer length of hospital stay among survivors but not among non-survivors; however, there were no differences in the hospital mortality rate between these two groups. Between the MRSA and the S. aureus-free groups, MRSA colonization or infection was significantly associated with an increased total hospital cost, a prolonged length of hospital stay and a higher hospital mortality rate among both survivors and non-survivors. It is critical to quantify the clinical and economic impact of MRSA to justify resource allocation for the development of strategies to improve clinical outcomes and to reduce the economic burden.

A Rapid Lysostaphin Production Approach and a Convenient Novel Lysostaphin Loaded Nano-emulgel; As a Sustainable Low-Cost Methicillin-Resistant Staphylococcus aureus Combating Platform.

Staphylococcus aureus is a Gram-positive pathogen that is capable of infecting almost every organ in the human body. Alarmingly, the rapid emergence of methicillin-resistant S.aureus strains (MRSA) jeopardizes the available treatment options. Herein, we propose sustainable, low-cost production of recombinant lysostaphin (rLST), which is a native bacteriocin destroying the staphylococcal cell wall through its endopeptidase activity. We combined the use of E. coli BL21(DE3)/pET15b, factorial design, and simple Ni-NTA affinity chromatography to optimize rLST production. The enzyme yield was up to 50 mg/L culture, surpassing reported systems. Our rLST demonstrated superlative biofilm combating ability by inhibiting staphylococcal biofilms formation and detachment of already formed biofilms, compared to vancomycin and linezolid. Furthermore, we aimed at developing a novel rLST topical formula targeting staphylococcal skin infections. The phase inversion composition (PIC) method fulfilled this aim with its simple preparatory steps and affordable components. LST nano-emulgel (LNEG) was able to extend active LST release up to 8 h and cure skin infections in a murine skin model. We are introducing a rapid, convenient rLST production platform with an outcome of pure, active rLST incorporated into an effective LNEG formula with scaling-up potential to satisfy the needs of both research and therapeutic purposes.

One-pot fabrication of multifunctional catechin@ZIF-L nanocomposite: Assessment of antibiofilm, larvicidal and photocatalytic activities.

Zeolitic imidazole framework (ZIF) is an emerging class of metal organic frameworks exhibiting unique features such as crystalline nature with tunable pore size, large surface area and biocompatible nature. Exceptional thermal and chemical stabilities of ZIF-L make it a suitable candidate for biomedical applications. The present study has focused on the single step fabrication of catechin encapsulated ZIF-L and evaluation of its antibiofilm efficiency, larvicidal activity and dye degradation ability. The as- prepared CA@ZIF-L nanocomposite was characterized by spectroscopic and microscopic techniques. The results revealed that the CA@ZIF-L showed significant toxicity against mosquito larvae in a dose dependent manner with the IC50 63.43±1.25 µg/mL. CA@ZIF-L showed dose dependent reduction of biofilm formation in both ATCC and clinical MRSA strains. In addition, CA@ZIF-L exhibited excellent photocatalytic activity with around 92% degradation of methylene blue under direct sunlight. Overall, the present work highlights the possibility of employing the multifunctional CA@ZIF-L nanocomposite as a suitable material for biomedical and photocatalytic applications.

Effect of trans-Cinnamaldehyde on Methicillin-Resistant Staphylococcus aureus Biofilm Formation: Metabolic Activity Assessment and Analysis of the Biofilm-Associated Genes Expression.

The effects of trans-cinnamaldehyde (TC) on transcriptional profiles of biofilm-associated genes and the metabolic activity of two methicillin-resistant Staphylococcus aureus (MRSA) strains showing a different degree of adherence to polystyrene, were evaluated. Metabolic activity of S. aureus in biofilm was significantly decreased in the presence of TC at 1/2 minimum biofilm inhibition concentration (MBIC). Expression levels of the genes encoding laminin binding protein (eno), elastin binding protein (ebps) and fibrinogen binding protein (fib) in the presence of TC at 1/2 MBIC were lower than in untreated biofilm in both the weakly and strongly adhering strain. The highest decrease of expression level was observed in case of fib in the strongly adhering strain, in which the amount of fib transcript was 10-fold lower compared to biofilm without TC. In the presence of TC at 1/2 MBIC after 3, 6, 8 and 12 h, the expression level of icaA and icaD, that are involved in the biosynthesis of polysaccharide intercellular adhesin, was above half lower in the weakly adhering strain compared to biofilm without TC. In the strongly adhering strain the highest decrease in expression of these genes was observed after 3 and 6 h. This study showed that TC is a promising anti-biofilm agent for use in MRSA biofilm-related infections.

Drivers for Livestock-Associated Methicillin-Resistant Staphylococcus Aureus Spread Among Danish Pig Herds - A Simulation Study.

To gain insight into the rapid increase in the number of livestock-associated Methicillin-resistant Staphylococcus aureus (LA-MRSA)-positive herds in Denmark, we developed an individual-based Monte Carlo simulation model. We aimed to assess whether transmission of LA-MRSA via pig movements could explain the observed increase in the number of positive herds in Denmark, and to evaluate the effect of other between-herd transmission mechanisms. Pig movements alone were not sufficient to mimic the observed increase in LA-MRSA-positive herds in Denmark in any of the modelled scenarios. The model identified three factors that played important roles in the between-herd spread of LA-MRSA: (1) the within-herd dynamics, (2) the frequency and effectiveness of indirect transmissions, and (3) unexplainable introduction of LA-MRSA to swine herds. These factors can act as starting points for the development of LA-MRSA control programs in pig herds in order to limit the risk of its transmission to humans.

Assessment of in vivo versus in vitro biofilm formation of clinical methicillin-resistant Staphylococcus aureus isolates from endotracheal tubes.

Our aim was to demonstrate that biofilm formation in a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA) can be enhanced by environment exposure in an endotracheal tube (ETT) and to determine how it is affected by systemic treatment and atmospheric conditions. Second, we aimed to assess biofilm production dynamics after extubation. We prospectively analyzed 70 ETT samples obtained from pigs randomized to be untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). A clinical MRSA strain (MRSA-in) was inoculated in pigs to create a pneumonia model, before treating with antibiotics. Tracheally intubated pigs with MRSA severe pneumonia, were mechanically ventilated for 69 ± 16 hours. All MRSA isolates retrieved from ETTs (ETT-MRSA) were tested for their in vitro biofilm production by microtiter plate assay. In vitro biofilm production of MRSA isolates was sequentially studied over the next 8 days post-extubation to assess biofilm capability dynamics over time. All experiments were performed under ambient air (O2) or ambient air supplemented with 5% CO2. We collected 52 ETT-MRSA isolates (placebo N = 19, linezolid N = 11, and vancomycin N = 22) that were clonally identical to the MRSA-in. Among the ETT-MRSA isolates, biofilm production more than doubled after extubation in 40% and 50% under 5% CO2 and O2, respectively. Systemic antibiotic treatment during intubation did not affect this outcome. Under both atmospheric conditions, biofilm production for MRSA-in was at least doubled for 9 ETT-MRSA isolates, and assessment of these showed that biofilm production decreased progressively over a 4-day period after extubation. In conclusion, a weak biofilm producer MRSA strain significantly enhances its biofilm production within an ETT, but it is influenced by the ETT environment rather than by the systemic treatment used during intubation or by the atmospheric conditions used for bacterial growth.

Costs and Benefits Associated with the MRSA Search and Destroy Policy in a Hospital in the Region Kennemerland, The Netherlands.

OBJECTIVE: The objective of this study was to analyze the costs and benefits of the MRSA Search and Destroy (S&D) policy between 2008 and 2013 in the Kennemer Gasthuis, a 400 bed teaching hospital in the region Kennemerland, the Netherlands. METHODS: A patient registration database was used to retrospectively calculate costs, including screening, isolation, follow-up, contact tracing, cleaning, treatment, deployment of extra healthcare workers, salary for an infection control practitioner (ICP) and service of isolation rooms. The estimated benefits (costs and lives when no MRSA S&D was applied) were based on a varying MRSA prevalence rate (up to 50%). RESULTS: When no MRSA S&D policy was applied, the additional costs and deaths due to MRSA bacteraemia were estimated to be € 1,388,907 and 33 respectively (at a MRSA prevalence rate of 50%). Currently, the total costs were estimated to be € 290,672 (€ 48,445 annually) and a MRSA prevalence rate of 17.3% was considered as break-even point. Between 2008 and 2013, a total of 576 high risk patients were screened for MRSA carriage, of whom 19 (3.3%) were found to be MRSA positive. Forty-nine patients (72.1%) were found unexpectedly. CONCLUSIONS: Application of the MRSA S&D policy saves lives and money, although the high rate of unexpected MRSA cases is alarming.

Developments in the pharmacokinetic/pharmacodynamic index of linezolid: a step toward dose optimization using Monte Carlo simulation in critically ill patients.

OBJECTIVES: This study evaluated the efficacy of the pharmacokinetic/pharmacodynamic (PK/PD) index for increasing the success rate of linezolid treatment based on Monte Carlo simulation, and compared differences between the calculated PK/PD breakpoints and those defined by committee for critically ill patients with linezolid treatment. METHODS: A Monte Carlo simulation involving 10000 subjects was used to analyze the pharmacokinetic parameters and microbiological data of linezolid for an effectiveness evaluation at the corresponding AUC24/MIC values (area under the serum concentration-time curve over 24h/minimum inhibitory concentration). RESULTS: As the PK/PD index of linezolid increased from 80 to 120, the corresponding probability of target attainment (PTA) decreased from 99.91% to 18.97%, with a MIC of 2mg/l. Furthermore, the cumulative fraction of response (CFR) reached <90% for several pathogens at an AUC24/MIC of 100-120, revealing a relatively lower efficacy with recommended linezolid dosing. CONCLUSIONS: These findings reveal that the target AUC24/MIC value of 80-120 requires further classification for more accurate assessment of the linezolid dose regimen. At a MIC of ≥2mg/l, the clinical outcome varies greatly for different AUC24/MIC values when applying the same dose of linezolid. In such cases, we suggest optimized adjustment of the linezolid dosage regimen.

An assessment of the effectiveness of mechanical and chemical cleaning of Essix orthodontic retainer.

OBJECTIVES: To determine the effectiveness of mechanical and chemical cleaning on the removal of microorganisms from Essix orthodontic retainers. DESIGN: In vitro laboratory study. SETTING: Department of Orthodontics and Microbiology, Eastman Dental Institute, University College London, UK. METHODS: Study 1: 120 Essix retainers were divided into four cleaning groups. The effectiveness of each cleaning method to remove a single species biofilm of Streptococcus mutans from the retainer was assessed. Study 2: 140 Essix retainers were divided into four study groups (brushing with fluoride toothpaste, chlorhexidine gel, immersion in chlorhexidine solution only and a control) to investigate the chemical and mechanical cleaning of the multispecies biolfilm of (Streptococcus sanguis, Actinomyces naeslundii, methicillin-resistant Staphylococcus aureus and Candida albicans). RELEVANT RESULTS: In study 1, brushing with toothpaste resulted in 99% reduction of Streptococcus mutans. In study 2, all three cleaning methods recorded similarly statistically significant reductions in colony forming units per millilitre compared to the control. There were no statistically significant differences between any of the cleaning groups for any of the microorganisms except MRSA-16. For MRSA-16, chlorhexidine mouthwash and gel were significantly more potent in eliminating the microorganism than the fluoride toothpaste. CONCLUSIONS: All three cleaning methods effectively removed 99% of microorganisms from the Essix retainers. Brushing with fluoride toothpaste can therefore be confirmed as an effective method for cleaning retainers in most circumstances. The use of chlorhexidine gel or mouthwash is recommended in patients where bacterial infection has to be avoided due to immunosuppression or other reasons.

Fitness cost: a bacteriological explanation for the demise of the first international methicillin-resistant Staphylococcus aureus epidemic.

OBJECTIVES: Denmark and several other countries experienced the first epidemic of methicillin-resistant Staphylococcus aureus (MRSA) during the period 1965-75, which was caused by multiresistant isolates of phage complex 83A. In Denmark these MRSA isolates disappeared almost completely, being replaced by other phage types, predominantly only penicillin resistant. We investigated whether isolates of this epidemic were associated with a fitness cost, and we employed a mathematical model to ask whether these fitness costs could have led to the observed reduction in frequency. METHODS: Bacteraemia isolates of S. aureus from Denmark have been stored since 1957. We chose 40 S. aureus isolates belonging to phage complex 83A, clonal complex 8 based on spa type, ranging in time of isolation from 1957 to 1980 and with various antibiograms, including both methicillin-resistant and -susceptible isolates. The relative fitness of each isolate was determined in a growth competition assay with a reference isolate. RESULTS: Significant fitness costs of 2%-15% were determined for the MRSA isolates studied. There was a significant negative correlation between number of antibiotic resistances and relative fitness. Multiple regression analysis found significantly independent negative correlations between fitness and the presence of mecA or streptomycin resistance. Mathematical modelling confirmed that fitness costs of the magnitude carried by these isolates could result in the disappearance of MRSA prevalence during a time span similar to that seen in Denmark. CONCLUSIONS: We propose a significant fitness cost of resistance as the main bacteriological explanation for the disappearance of the multiresistant complex 83A MRSA in Denmark following a reduction in antibiotic usage.

Pharmacodynamic assessment of vancomycin-rifampicin combination against methicillin resistant Staphylococcus aureus biofilm: a parametric response surface analysis.

OBJECTIVES: A combination of vancomycin and rifampicin (rifampin) is commonly used to treat staphylococcal infections but its efficacy against methicillin-resistant Staphylococcus aureus (MRSA) biofilm is controversial. The objective of this study was to use a recently developed quantitative methodology to characterise the killing effect of vancomycin and rifampin combination against MRSA biofilm. METHODS: MRSA biofilm was exposed to escalating concentrations of vancomycin and rifampin and the viability of the biofilm-ensconced bacteria was evaluated. ADAPT II was used to model the concentration-effect relationship and determine the optimal sampling concentrations. Combination experiments were then conducted and the observations were compared with a simulated response surface representing null interaction. Finally, the pharmacodynamic interaction index (PDI) was computed as the ratio of the volumes under the observed and simulated surfaces. KEY FINDINGS: In the combination experiments, all observations showed an inferior antibacterial effect to what is expected under null interaction assumption and the PDI was estimated to be 3.36 (95% CI, 3.25 to 3.46). CONCLUSIONS: The results of the study demonstrate in-vitro antagonism between vancomycin and rifampin against MRSA biofilm. The quantitative approach employed to quantify the antibacterial effect of the combination provides a scientific rationale for further in-vivo investigations that should allow a better understanding of the therapeutic potential of this combination in biofilm-associated MRSA infections.

Clinical and financial outcomes due to methicillin resistant Staphylococcus aureus surgical site infection: a multi-center matched outcomes study.

BACKGROUND: The clinical and financial outcomes of SSIs directly attributable to MRSA and methicillin-resistance are largely uncharacterized. Previously published data have provided conflicting conclusions. METHODOLOGY: We conducted a multi-center matched outcomes study of 659 surgical patients. Patients with SSI due to MRSA were compared with two groups: matched uninfected control patients and patients with SSI due to MSSA. Four outcomes were analyzed for the 90-day period following diagnosis of the SSI: mortality, readmission, duration of hospitalization, and hospital charges. Attributable outcomes were determined by logistic and linear regression. PRINCIPAL FINDINGS: In total, 150 patients with SSI due to MRSA were compared to 231 uninfected controls and 128 patients with SSI due to MSSA. SSI due to MRSA was independently predictive of readmission within 90 days (OR = 35.0, 95% CI 17.3-70.7), death within 90 days (OR = 7.27, 95% CI 2.83-18.7), and led to 23 days (95% CI 19.7-26.3) of additional hospitalization and $61,681 (95% 23,352-100,011) of additional charges compared with uninfected controls. Methicillin-resistance was not independently associated with increased mortality (OR = 1.72, 95% CI 0.70-4.20) nor likelihood of readmission (OR = 0.43, 95% CI 0.21-0.89) but was associated with 5.5 days (95% CI 1.97-9.11) of additional hospitalization and $24,113 (95% 4,521-43,704) of additional charges. CONCLUSIONS/SIGNIFICANCE: The attributable impact of S. aureus and methicillin-resistance on outcomes of surgical patients is substantial. Preventing a single case of SSI due to MRSA can save hospitals as much as $60,000.

Community-associated meticillin-resistant Staphylococcus aureus infections: epidemiology, recognition and management.

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, particularly in hospitalized patients and those with significant healthcare exposure. In recent years, epidemic community-associated MRSA (CA-MRSA) infections occurring in patients without healthcare risk factors have become more frequent. The most common manifestation of CA-MRSA infection is skin and soft tissue infection, although necrotizing pneumonia, sepsis and osteoarticular infections can occur. CA-MRSA strains have become endemic in many communities and are genetically distinct from previously identified MRSA strains. CA-MRSA may be more capable colonizers of humans and more virulent than other S. aureus strains. Specific mechanisms of pathogenicity have not been elucidated, but several factors have been proposed as responsible for the virulence of CA-MRSA, including the Panton-Valentine leukocidin, phenol-soluble modulins and type I arginine catabolic mobile element. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community- or healthcare-associated status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacological therapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-beta-lactam antibacterial agents. Empirical antibacterial therapy should include an MRSA-active agent, particularly in areas where CA-MRSA is endemic.

Laboratory and in-use assessment of methicillin-resistant Staphylococcus aureus contamination of ergonomic computer keyboards for ward use.

BACKGROUND: An ideal computer keyboard for clinical use would be easily cleanable and cleaned by staff, meet acceptable levels of usability, and not attract hospital bacteria. METHODS: In vitro studies were performed to demonstrate bacterial transfer between keyboard surfaces and gloves. This was followed by a usability study and a controlled trial of keyboard contamination in an intensive care unit both with and without an alarm to indicate the need for cleaning. Eight cleanable keyboards were placed at random beds and compared with standard keyboards. RESULTS: Bacteria were most easily removed from a flat silicone-coated surface. The total viable count on flat keyboards with an alarm was lower than that on standard or other cleanable keyboards (median, 19 colony-forming units [cfu] (interquartile range, 7 to 40 cfu), n = 34; 65 cfu (33 to 140 cfu), n = 50; and 40 cfu (21 to 57 cfu), n = 80). Compliance with hand hygiene before touching the standard keyboard was 27%, but the alarmed keyboard was cleaned on 87% of occasions on which the alarm was triggered. The usability study found the flat profile of the cleanable keyboard did not interfere with routine use, except for touch-typing. CONCLUSION: The flat keyboard with an alarm is easy to clean, and it use is associated with better cleaning compliance.