Meticillin-resistant S. Aureus Research Articles

In vitro evaluation of bactericidal effects of fluorescent light energy on Staphylococcus pseudintermedius and S. aureus.

Staphylococcus pseudintermedius and S. aureus are bacterial species of importance in veterinary medicine. The increasing incidence of antibiotic resistance necessitates the implementation of novel treatment modalities. Fluorescent light energy (FLE) is used as an adjunctive and primary treatment for canine pyoderma. However, no invitro studies exist investigating its bactericidal effects against S. pseudintermedius or S. aureus. To determine the bactericidal effects of FLE on S. pseudintermedius and S. aureus isolates. Two meticillin-susceptible S. pseudintermedius (MSSP) isolates, three meticillin-resistant S. pseudintermedius (MRSP) isolates and one meticillin-resistant S. aureus (MRSA) isolate were studied. Acommercially available blue light-emitting diode (bLED) lamp and photoconverting hydrogel FLE system was used. All bacteria were exposed to five conditions following inoculation: (i) no treatment (control); (ii) blue light (bLED) once; (iii) bLED twice consecutively; (iv) FLE (bLED and photoconverting hydrogel) once; and (v) FLE (bLED and photoconverting hydrogel) twice consecutively. Each individual exposure was 2 min long. No statistically significant differences (p < 0.05) were found for any treatment group when each bacterial isolate was evaluated individually, MSSP isolates were grouped, MRSP isolates were grouped, when all S. pseudintermedius isolates were combined, or when all isolates of both Staphylococcus species were combined. While clinical success is reported when using FLE to treat Staphylococcus infections in animals, no invitro antibacterial efficacy was identified for S. pseudintermedius or S. aureus under experimental conditions. The clinical success observed with FLE may be the result of a more complex invivo response.

Molecular epidemiology of meticillin-susceptible Staphylococcus aureus in the neonatal intensive care unit

Staphylococcus aureus - both meticillin-resistant S.aureus (MRSA) and meticillin-susceptible S.aureus (MSSA) - is a major cause of neonatal infections. Infection control measures have not lowered the incidence of MSSA infections to the same degree as that of MRSA infections. To investigate the transmission pathway of MSSA in neonatal intensive care unit (NICU) using genetic analysis. Neonatal patients, their parents, and healthcare workers were swab-tested in the NICU at our hospital at the time of hospitalization and then every month thereafter from October 1st, 2018 to March 31st, 2019. Whole-genome sequencing was performed to test for MSSA strains. Multi-locus sequence typing and single nucleotide polymorphism analysis were used to identify strains and understand their relatedness. There were 16 MSSA-positive patients. Four MSSA-positive patients shared strains from the same phylogenetic groups as those of healthcare workers. One presented the same strain as the parent. MSSA-positive twin neonates shared the same strain. Ten had sporadic strains; 32 of the 97 tested healthcare workers were MSSA positive. The findings of this study suggest that the route of transmission of MSSA in NICU may be through MSSA in the hospital environment in addition to horizontal transmission via healthcare workers. Along with hand hygiene with alcohol, thorough environmental maintenance and parental education are important for infection control in NICUs targeting MSSA.

Key predictors and burden of meticillin-resistant Staphylococcus aureus infection in comparison with meticillin-susceptible S. aureus infection in an Australian hospital setting

Staphylococcus aureus is associated with significant mortality and increased burden on the healthcare system. Relatively few reliable estimates are available regarding the impact of meticillin-resistant S.aureus (MRSA) infection compared with meticillin-susceptible S.aureus (MSSA) infection. To compare patients with MRSA infection and MSSA infection to identify differences in inpatient mortality, length of stay and costs of hospital services, and identify predictors of MRSA as a cause of S.aureus infection. An analytical, retrospective, longitudinal study using non-identifiable linked data on adults admitted to hospitals of a health district in Australia with a diagnosis of S.aureus infection over a 10-year period. The main outcome measure was 30-day inpatient mortality. Secondary endpoints included total overnight stays, all-cause inpatient mortality, and hospitalization costs within 1 year of index admission. Inpatient mortality at 30, 100 and 365 days was estimated to be significantly greater for patients with MRSA infection. The mean additional cost of MRSA infection when controlling for additional factors was $5988 and 4 nights of additional hospital stay per patient within 1 year of index admission. Key predictors of MRSA infection were: date of index admission; higher comorbidity score; greater socio-economic disadvantage; admission to hospital other than via the emergency department; older age; and prior admission to hospital within 28 days of index admission. MRSA infection is associated with increased inpatient mortality, costs and hospital length of stay compared with MSSA infection. Efforts are required to alleviate the additional burden of MRSA infection on patients and healthcare systems.

Surveillance of multi-drug resistance phenotypes in Staphylococcus aureus in Japan and correlation with whole-genome sequence findings

Antimicrobial resistance in Staphylococcus aureus imposes a high disease burden. Both phenotypic and genotypic monitoring are key to understanding and containing emerging resistant strains. Phenotypic monitoring of emerging resistance in S.aureus and correlation of priority strain phenotypes with whole-genome sequencing (WGS) findings. Antimicrobial susceptibility test results of >40,000 isolates from 213 participating hospitals from 2011 to 2019 were exported from the national Japan Nosocomial Infections Surveillance (JANIS) database. Longitudinal and geographic distribution and prevalence of distinct multi-drug resistance phenotypes ('resistance profiles') of S.aureus were examined among hospitals and prefectures. We further conducted a genome sequence analysis of strains with specific resistance profiles of concern. The overall prevalence of meticillin-resistant S.aureus (MRSA) decreased from 40.3% to 35.1% from 2011 to 2019. However, among dozens of S.aureus resistance profiles, only one profile of a type of MRSA, exhibited a statistically significant increase in inpatient frequency, exceeding 10% during the nine years. This MRSA profile showed resistance to oxacillin, erythromycin and levofloxacin. Analysis of WGS results of S.aureus isolates with this phenotype revealed that most belonged to clonal complex 8, and all carried SCCmec IV, typical of community-acquired MRSA. Tracking distinct resistance profiles deepened our understanding of the overall decrease in MRSA and led to recognition of the emergence of a new resistance phenotype. This study provides a model for future epidemiological research on antimicrobial resistance correlating multi-drug resistance phenotypes with selective genome sequencing, which can be applied to other bacterial species.

Staphylococcus aureus bloodstream infections: diverging trends of meticillin-resistant and meticillin-susceptible isolates, EU/EEA, 2005 to 2018.

BackgroundInvasive infections caused by Staphylococcus aureus have high clinical and epidemiological relevance. It is therefore important to monitor the S. aureus trends using suitable methods.AimThe study aimed to describe the trends of bloodstream infections (BSI) caused by meticillin-resistant S. aureus (MRSA) and meticillin-susceptible S. aureus (MSSA) in the European Union (EU) and the European Economic Area (EEA).MethodsAnnual data on S. aureus BSI from 2005 to 2018 were obtained from the European Antimicrobial Resistance Surveillance Network (EARS-Net). Trends of BSI were assessed at the EU/EEA level by adjusting for blood culture set rate (number of blood culture sets per 1,000 days of hospitalisation) and stratification by patient characteristics.ResultsConsidering a fixed cohort of laboratories consistently reporting data over the entire study period, MRSA percentages among S. aureus BSI decreased from 30.2% in 2005 to 16.3% in 2018. Concurrently, the total number of BSI caused by S. aureus increased by 57%, MSSA BSI increased by 84% and MRSA BSI decreased by 31%. All these trends were statistically significant (p < 0.001).ConclusionsThe results indicate an increasing health burden of MSSA BSI in the EU/EEA despite a significant decrease in the MRSA percentage. These findings highlight the importance of monitoring antimicrobial resistance trends by assessing not only resistance percentages but also the incidence of infections. Further research is needed on the factors associated with the observed trends and on their attributable risk.

Exploring the evolution and epidemiology of European CC1-MRSA-IV: tracking a multidrug-resistant community-associated meticillin-resistant Staphylococcus aureus clone.

This study investigated the evolution and epidemiology of the community-associated and multidrug-resistant Staphylococcus aureus clone European CC1-MRSA-IV. Whole-genome sequences were obtained for 194 European CC1-MRSA-IV isolates (189 of human and 5 of animal origin) from 12 countries, and 10 meticillin-susceptible precursors (from North-Eastern Romania; all of human origin) of the clone. Phylogenetic analysis was performed using a maximum-likelihood approach, a time-measured phylogeny was reconstructed using Bayesian analysis, and in silico microarray genotyping was performed to identify resistance, virulence-associated and SCCmec (staphylococcal cassette chromosome mec) genes. Isolates were typically sequence type 1 (190/204) and spa type t127 (183/204). Bayesian analysis indicated that European CC1-MRSA-IV emerged in approximately 1995 before undergoing rapid expansion in the late 1990s and 2000s, while spreading throughout Europe and into the Middle East. Phylogenetic analysis revealed an unstructured meticillin-resistant S. aureus (MRSA) population, lacking significant geographical or temporal clusters. The MRSA were genotypically multidrug-resistant, consistently encoded seh, and intermittently (34/194) encoded an undisrupted hlb gene with concomitant absence of the lysogenic phage-encoded genes sak and scn. All MRSA also harboured a characteristic ~5350 nt insertion in SCCmec adjacent to orfX. Detailed demographic data from Denmark showed that there, the clone is typically (25/35) found in the community, and often (10/35) among individuals with links to South-Eastern Europe. This study elucidated the evolution and epidemiology of European CC1-MRSA-IV, which emerged from a meticillin-susceptible lineage prevalent in North-Eastern Romania before disseminating rapidly throughout Europe.

Prevalence and clinical associations of Staphylococcus aureus small-colony variant respiratory infection in children with cystic fibrosis (SCVSA): a multicentre, observational study

Staphylococcus aureus is the bacterium cultured most often from respiratory secretions of people with cystic fibrosis. Both meticillin-susceptible S aureus and meticillin-resistant S aureus (MRSA) can adapt to form slow-growing, antibiotic-resistant isolates known as small-colony variants that are not routinely identified by clinical laboratories. We aimed to determine the prevalence and clinical significance of S aureus small-colony variants and their subtypes among children with cystic fibrosis. The Small Colony Variant Staphylococcus aureus (SCVSA) study was a 2-year longitudinal study of children aged 6-16 years at five US cystic fibrosis centres, using culture methods sensitive for small-colony variants. Children were eligible if they had a documented diagnosis of cystic fibrosis and a minimum of two cystic fibrosis clinic visits and two respiratory cultures in the previous 12 months at enrolment. Participants attended clinic visits quarterly, at which respiratory tract samples were taken and measures of lung function (percentage of predicted forced expiratory volume in 1 s [FEV1] and frequency of respiratory exacerbations) were recorded. We determined the prevalence of small-colony variants and their subtypes, and assessed their independent associations with lung function and respiratory exacerbations using linear mixed-effects and generalised estimating equation logistic regression models. Analyses included both univariate models (unadjusted) and multivariate models that adjusted for potential confounders, including age, sex, race, baseline microbiology, treatment with CFTR modulator, and CTFR genotype. Between July 1, 2014, and May 26, 2015, we enrolled 230 children. Participants were followed-up for 2 years, with a mean of 6·4 visits (SD 1·14) per participant (range 2-9 visits) and a mean interval between visits of 3·94 months (SD 1·77). Across the 2-year period, S aureus small-colony variants were detected in 64 (28%) participants. Most (103 [56%] of 185) of the small-colony variants detected in these participants were thymidine dependent. Children with small-colony variants had significantly lower mean percentage of predicted FEV1 at baseline than did children without small-colony variants (85·5 [SD 19] vs 92·4 [SD 18·6]; p=0·0145). Small-colony variants were associated with significantly lower percentage of predicted FEV1 throughout the study in regression models, both in univariate analyses (regression coefficient -7·07, 95% CI -12·20 to -1·95; p=0·0068) and in multivariate analyses adjusting for potential confounders (-5·50, -10·51 to -0·48; p=0·0316). Small colony variants of the thymidine-dependent subtype had the strongest association with lung function in multivariate regression models (regression coefficient -10·49, -17·25 to -3·73; p=0·0024). Compared with children without small-colony variants, those with small-colony variants had significantly increased odds of respiratory exacerbations in univariate analyses (odds ratio 1·73, 95% CI 1·19 to 2·52; p=0·0045). Children with thymidine-dependent small-colony variants had significantly increased odds of respiratory exacerbations (2·81, 1·69-4·67; p=0·0001), even after adjusting for age, sex, race, genotype, CFTR modulator, P aeruginosa culture status, and baseline percentage of predicted FEV1 (2·17, 1·33-3·57; p=0·0021), whereas those with non-thymidine-dependent small-colony variants did not. In multivariate models including small-colony variants and MRSA status, P aeruginosa was not independently associated with lung function (regression coefficient -4·77, 95% CI -10·36 to 0·83; p=0·10) and was associated with reduced odds of exacerbations (0·54, 0·36 to 0·81; p=0·0028). Only the small-colony variant form of MRSA was associated with reduced lung function (-8·44, -16·15 to -0·72; p=0·0318) and increased odds of exacerbations (2·15, 1·24 to 3·71; p=0·0061). Infection with small-colony variants, and particularly thymidine-dependent small-colony variants, was common in a multicentre paediatric population with cystic fibrosis and associated with reduced lung function and increased risk of respiratory exacerbations. The adoption of small-colony variant identification and subtyping methods by clinical laboratories, and the inclusion of small-colony variant prevalence data in cystic fibrosis registries, should be considered for ongoing surveillance and study. The Cystic Fibrosis Foundation and the National Institutes of Health.

Does biofilm formation have different pathways in Staphylococcus aureus?

Objective(s):Biofilm formation is one of the most important factors in the development of infections caused by Staphylococcus aureus. In this study, the expression levels of genes responsible for biofilm formation were studied in methicillin sensitive and methicillin resistant S. aureus.Materials and Methods:A total of 100 meticillin-resistant s.aureus (MRSA) and meticillin-sensetive s.aureus (MSSA) isolates were studied. Bacterial biofilm formation was evaluated phenotypically using microtiter plate method. Real-time PCR tests were conducted to determine the expression levels of genes involved in biofilm formation.Results:Quantitative biofilm formation test was repeated three times for each specimen. The prevalence of weak, medium, and strong biofilm producers were 16%, 49%, and 35%, respectively. In MSSA isolates, expression levels of ica genes increased compared to the fnbA, fnbB, clfA and clfB genes. These results were different in MRSA isolates, and ica genes showed a decreased gene expression levels compared to the aforementioned genes. Conclusion:Considering the results of this study, clf genes probably contribute to the same extent in both MRSA and MSSA isolates, and there is probably no significant difference in the role of these genes in these isolates. In addition, the results of this study indicated that MRSA may not use the conventional route for biofilm formation and may use independent pathways through Polysaccharide intercellular adhesion (PIA).

The in vitro antibacterial activity of the anthelmintic drug oxyclozanide against common small animal bacterial pathogens

Repurposing existing drugs is one approach to address the growing concerns of multi-drug resistant bacterial pathogens in veterinary medicine. Oxyclozanide is in the anthelmintic drug class salicylanilide, which has been used primarily as a treatment and preventative for Fasciola hepatica in ruminants. The antimicrobial activity of oxyclozanide has been studied in human medicine; its activity against common small animal bacterial pathogens such as Staphylococcus pseudintermedius has yet to be determined. The aim of this study was to measure and establish the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of oxyclozanide against S.pseudintermedius and other common small animal bacterial pathogens. The MIC and MPC of oxyclozanide were determined from eighteen meticillin sensitive S.pseudintermedius (MSSP) isolates and eleven meticillin-resistant S.pseudintermedius (MRSP), as well as single isolates of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. The MIC of the eighteen meticillin-sensitive S.pseudintermedius isolates was 0.5-1μg/mL and the MPC ranged between 16 and 32μg/mL. The MIC of the eleven meticillin-resistant strains of S.pseudintermedius ranged from 0.5 to 2μg/mL with a MPC ranging between 16 and 32μg/mL. A single isolate of meticillin-resistant S.aureus (MRSA) had an MIC of 1μg/mL and MPC 16μg/mL. No inhibition of growth was seen at the concentrations tested for bacterial isolate strains E.coli, P.aeruginosa and E.faecalis. Oxyclozanide demonstrated in-vitro antibacterial activity against meticillin-resistant S.pseudintermedius. Further studies are needed to evaluate the potential use of oxyclozanide as a topical bactericidal agent.

The value of the infection prevention and control nurse led MRSA ward round

Meticillin-resistant S. aureus (MRSA) is prevalent in most parts of the world. The study took place at Queen Elizabeth Hospital Birmingham (QEHB) a UK tertiary referral hospital. At QEHB innovative nurse led daily ward rounds for patients that acquire hospital acquired MRSA during their hospital stay are undertaken. The aim is to optimise care delivered for these patients whilst at QEHB, thereby reducing the risk of infection in patients with healthcare-acquired MRSA. A segmented Poisson regression model suggests that the MRSA bacteraemia rate was affected where an 88.94% reduction (p = 0.0561) in bacteraemias was seen by the introduction of these ward rounds. We describe a nurse led MRSA ward round which was associated with a lower rate of MRSA bacteraemias.

High prevalence of methicillin resistant and enterotoxin gene-positive Staphylococcus aureus among nasally colonized food handlers in central Iran.

This study defined the prevalence of enterotoxin gene-positive Staphylococcus aureus strains among food handlers and non-food processing healthy nasal S. aureus carriers in central Iran. Meticillin-resistant S. aureus (MRSA) strains were diagnosed by cefoxitin disk diffusion. PCR was used to detect the mecA, Sa442, and enterotoxin genes. Out of the 1113 food handlers, 224 (20.1%) were nasal carriers of S. aureus and 157 (70.1%) of these isolates were positive for one or more enterotoxin genes. The most prevalent enterotoxin gene was sei (40.2%), followed by seg (35.3%), sea (23.5%), seb (15.2%), sec (5.5%), and seh (2.7%). See and sed genes were not found. Sixty seven (42.7%) of enterotoxin gene-positive isolates possessed a single enterotoxin gene, and 64 (40.8%), 23 (14.7%), and 3 (1.9%) contained two, three, or four enterotoxin genes, respectively. The most frequently detected gene combination was sei/seg (n = 35, 22.3%). Thirty seven (16.5%) isolates were diagnosed as MRSA, and 27 (73%) of these strains were positive for at least one enterotoxin gene. Out of 546 healthy controls, 100 individuals were identified as S. aureus nasal carriers; among the strains, 39 (39%) were positive for at least one enterotoxin gene. Only one (1%) CA-MRSA was identified among the strains from the volunteers. A high prevalence of meticillin resistant and enterotoxin-positive S. aureus were documented in food handlers. We suggest that this may be due to the frequent handling of contaminated foodstuffs and that this is possibly related to the elevated frequencies of acquired staphylococcal food poisoning in this population.

Clinical and economic burden of bloodstream infections caused by meticillin-resistant and meticillin-susceptible Staphylococcus aureus in Chinese tertiary hospitals from 2010 to 2017: a multicentre, retrospective cohort study

BackgroundGlobally, antimicrobial resistance has become one of the most complex public health challenges. Accurate estimates of health and economic burden of antimicrobial resistance has not been available in China because of the absence of representative empirical data. We therefore aimed to estimate the effect of antimicrobial resistance attributable to Staphylococcus aureus bloodstream infections in Chinese hospitals, and to compare the effect of resistant strains with susceptible strains. MethodsWe did a multicentre, retrospective cohort study of 11 tertiary hospitals in China. The cohort consisted of all inpatients with S aureus bloodstream infections from the sample hospitals, and we randomly included individuals free of S aureus bloodstream infections. We stratified the patients into two categories of S aureus bloodstream infections: meticillin-susceptible S aureus (MSSA) or meticillin-resistant S aureus (MRSA). The primary outcome was the effect of antimicrobial resistance on excess length of stay in the hospital, hospital mortality, and cost of treatment. We adopted a multistate model to estimate the expected length of stay. Multi-level Cox proportional hazards models were adopted to compare the hazard of reaching hospital death, discharge alive, and the combined end-of-stay endpoint. Two bed-day values were adopted when estimating the cost of treatment. This study was approved by Peking University Health Science Center Ethics Committee, with a waiver for individual informed consent. FindingsFrom Jan 1, 2010, to June 31, 2017, we assessed 861 inpatients with S aureus bloodstream infections and 10 000 individuals free of S aureus bloodstream infections. Of the 861 admissions with an S aureus blood stream infection detected, 324 (38%) were due to MRSA and 537 (62%) were due to MSSA. Bloodstream infections caused by MRSA prolonged the length of stay in the hospital by 13·4 days (95% CI 11·1–16·3), and MSSA bloodstream infections prolonged the length of stay by 11·9 days (95% CI 9·7–14·1). However, bloodstream infections caused by MRSA did not increase the hazard of death (adjusted hazard ratio [aHR] 0·31, 95% CI 0·09–1·10). MSSA bloodstream infections also did not increase the hazard of death (aHR 0·59, 95% CI 0·14–2·54). Compared with MSSA, MRSA did not significantly increase the hazard of death (aHR 0·44, 95% CI 0·19–1·03), excess length of stay (1·5 days, 95% CI −0·4 to 2·8), and cost of treatment. Although the cost of MRSA treatment was higher per infection than MSSA treatment, the annual cost of MSSA was higher overall. InterpretationBy accounting for time-dependent bias and important confounders, this study added to the existing literature about the effect of antimicrobial resistance in China. Current results of the study implicate the importance of surveillance and infection control policies that target infections rather than resistance. FundingChina Medical Board (17-270).

Virulence determinants, biofilm production and antimicrobial susceptibility in Staphylococcus aureus causing device-associated infections in a Tunisian hospital

Staphylococcus aureus is a clinically relevant pathogen that causes device-related infections (DRI) driven by several virulence factors. This study characterized S. aureus isolates involved in DRI in Tunisian patients. Forty consecutive S. aureus strains causing DRI and 47 randomly selected S. aureus strains causing non-device-related infections (NDRI) were collected. All strains were screened phenotypically for antibiotic susceptibility and biofilm forming ability. They were investigated for accessory gene regulator (agr) types, biofilm encoding genes (icaADBC), adhesins, leukotoxins, toxic shock toxin, enterotoxins and exotoxins encoding genes by polymerase chain reaction. Meticillin-resistant S. aureus (MRSA) strains were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing. MRSA rates among DRI and NDRI isolates were 23% and 49% (P=0.02), respectively. The DRI isolates formed biofilm more frequently (n=32) than the NDRI isolates (n=28) (P=0.04), with predominance of the moderate biofilm producer category (P=0.027). All biofilm-positive isolates except four harboured icaADBC genes. A significant difference was observed between DRI and NDRI isolates for fnbA (53-77%), spa (45-26%), sdrD (80-55%) and sen (33-11%) genes. DRI strains were agrI (48%) and agrII (30%) types, whereas NDRI strains were agrI (36%) and agrIII (43%) types. SCCmec type IV was carried by 50% of MRSA isolates. This study highlights the virulence potential displayed by S. aureus isolated from DRI in comparison with NDRI.

The Changing Pattern of Population Structure of Staphylococcus aureus from Bacteremia in China from 2013 to 2016: ST239-030-MRSA Replaced by ST59-t437.

To investigate the epidemiology and genetic structure of Staphylococcus aureus bacteremia in China, a total of 416 isolates from 22 teaching hospitals in 12 cities from 2013 and 2016 were characterized by antibiogram analysis, multilocus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing. The predominant meticillin-susceptible (MSSA) genotypes in 2013 were ST188 (19.1%), ST7 (8.7%), and ST398 (7.8%), respectively, and they continued to be the main genotypes in 2016. The prevalence of meticillin-resistant S. aureus (MRSA) were 36.5% (66/181) and 36.6% (86/235) in 2013 and 2016, respectively. Interestingly, the susceptibility rates of MRSA to rifampicin and fluoroquinolones increased significantly from 2013 to 2016 (P < 0.01), and this was associated with changes in genetic structure. ST239-t030-MRSA, the predominant genotype among all MRSAs in 2013 (34.8%), was replaced by ST59-t437-MRSA (15.1%) in 2016. Further analysis revealed that the ST239-t030-MRSA were more resistant to rifampicin, tetracycline and fluoroquinolones than ST59-t437-MRSA (P < 0.01). To further gain insight into the mechanisms underlying the changes of genetic structure, in vitro competition and fitness measurements were performed. Importantly, ST239-t030-MRSA displayed lower growth rate and lower competitive advantage compared to ST59-t437-MRSA. Together, our findings reveal that fitness advantage of ST59-t437-MRSA over ST239-t030-MRSA may lead to changes in genetic structure and increased susceptibility of MRSA to rifampicin and fluoroquinolones in Chinese patients with S. aureus bacteremia. Our study supports temporal dynamics in MRSA clone diversities, further providing critical insights into the importance of continued monitoring of MRSA.

Targeted surveillance of nosocomial infection in intensive care units of 176 hospitals in Jiangsu province, China

Nosocomial infections (NIs) impact care and costs in hospitals across the globe. There are few data on targeted surveillance of NI in intensive care units (ICUs), and data specific to the risk factors for NI are especially limited. One hundred and seventy-six secondary and tertiary hospitals performed NI targeted surveillance in their ICUs. The data were collected and summarized by Minke software, then fed back once per quarter. The incidence of NI appeared to decrease, and the incidence of NI per 1000 patient-days and adjusted incidence were 25.63‰ and 7.41‰ in 2010, and 9.73‰ and 2.76‰ in 2015, respectively. The NI incidence in general hospitals was higher than in specialized hospitals. The incidence of central-line-associated bloodstream infection (CLABSI) and catheter-associated urinary tract infection (CAUTI) appeared to decrease, and the incidence of ventilator-associated pneumonia (VAP) decreased markedly from 20.33‰ to 2.76‰. There was no statistically significant difference among ICUs. The six most frequently found pathogen-caused NIs were Acinetobacter baumannii (AB), Klebsiella pneumoniae (KP), Pseudomonas aeruginosa (PA), Staphylococcus aureus, Candida albicans, and Escherichia coli (E.coli). The isolation rate of carbapenem-resistant Gram-negative bacilli were carbapenem-resistant AB 80.53%, carbapenem-resistant PA 39.94%, carbapenem-resistant KP (CRKP) 24.86%, and carbapenem-resistant E.coli 9.23%. The isolation rate of meticillin-resistant S.aureus (MRSA) was 66.30%. The increasing trend of CRKP was statistically significant as analysed by the regression model. The incidences of VAP, CAUTI, and CLABSI were high in ICUs, and multidrug-resistant organisms were the primary pathogens of NI. The implementation of targeted surveillance may determine the risk factors of NI so that effective intervention measures can be taken to reduce the incidence of NI in ICU patients.

Validation of healthcare-associated infection surveillance in smaller Australian hospitals

A validation study was conducted in smaller (<100 acute beds) Victorian hospitals to evaluate case detection for Staphylococcus aureus bloodstream (SAB), meticillin-resistant S.aureus (MRSA) and vancomycin-resistant enterococci (VRE) infections. Overall, 142 infections were identified in 20 hospitals. For routine surveillance of SAB events, sensitivity was 74.4% and specificity was 100.0%. For MRSA infections, sensitivity was 47.5% and specificity was 90.9%. All confirmed VRE infections were reported correctly. Of unreported SAB and MRSA infections, 80% (N=16) and 83.9% (N=26) were community-associated infections, respectively. Future programme refinements include targeted education to ensure appropriate application of case definitions, particularly those including community onset.

Temporal trends and epidemiology of Staphylococcus aureus surgical site infection in the Swiss surveillance network: a cohort study

Staphylococcus aureus is the leading pathogen in surgical site infections (SSI). To explore trends and risk factors associated with S.aureus SSI. Risk factors for monomicrobial S.aureus SSI were identified from the Swiss multi-centre SSI surveillance system using multi-variate logistic regression. Both in-hospital and postdischarge SSI were identified using standardized definitions. Over a six-year period, data were collected on 229,765 surgical patients, of whom 499 (0.22%) developed monomicrobial S.aureus SSI; 459 (92.0%) and 40 (8.0%) were due to meticillin-susceptible S.aureus (MSSA) and meticillin-resistant S.aureus (MRSA), respectively. There was a significant decrease in the rate of MSSA SSI (P=0.007), but not in the rate of MRSA SSI (P=0.70). Independent protective factors for S.aureus SSI were older age [≥75 years vs <50 years: odds ratio (OR) 0.60, 95% confidence interval (CI) 0.44-0.83], laparoscopy/minimally invasive surgery (OR 0.68, 95% CI 0.50-0.92), non-clean surgery [OR 0.78 (per increase in wound contamination class), 95% CI 0.64-0.94] and correct timing of pre-operative antibiotic prophylaxis (OR 0.80, 95% CI 0.65-0.98). Independent risk factors were male sex (OR 1.38, 95% CI 1.14-1.66), higher American Society of Anesthesiologists' score (per one-point increment: OR 1.30, 95% CI 1.13-1.51), re-operation for non-infectious reasons (OR 4.59, 95% CI 3.59-5.87) and procedure type: cardiac surgery, laminectomy, and hip or knee arthroplasty had two-to nine-fold increased odds of S.aureus SSI compared with other procedures. SSI due to S.aureus are decreasing and becoming rare events in Switzerland. High-risk procedures that may benefit from specific preventive measures were identified. Unfortunately, many of the independent risk factors are not easily modifiable.

The in vitro antibacterial activity of incomplete iron salt of polyacrylic acid against Pseudomonas aeruginosa, meticillin-resistant Staphylococcus pseudintermedius and meticillin-resistant S. aureus.

The incomplete iron salt of polyacrylic acid (IIS-PAA) has been used for its haemostatic, wound healing and antibacterial properties in human patients. IIS-PAA is a water-soluble, acidic, hydrophilic polymer that is active at pH 2.9-4.0. To evaluate the antibacterial effect of IIS-PAA against Pseudomonas aeruginosa, meticillin-resistant Staphylococcus pseudintermedius (MRSP) and meticillin-resistant S. aureus (MRSA). This was a prospective, nonblinded in vitro study. Sixty canine isolates of P. aeruginosa, MRSP and MRSA were included. Minimum inhibitory concentrations (MICs) of IIS-PAA were determined by agar dilution on Mueller-Hinton agar using testing concentrations ranging from 0.0625-0.4% (raw material 100%) and based on Clinical and Laboratory Standards Institute guidelines. The median MIC for P. aeruginosa was 0.2% (range 0.2-0.3%), mean 0.2% and standard deviation (SD) of 0.018%. The median MIC for MRSP was 0.05% (0.025-0.1%), mean 0.058% and SD 0.022%, and the median MIC for MRSA was 0.1% (0.00625-0.4%), mean 0.126% and SD 0.080%. There were significant differences in MICs between the three bacteria types with MICs highest for Pseudomonas and lowest for MRSP (all P < 0.0001). IIS-PAA had in vitro antibacterial activity against three important bacterial pathogens. Further studies of IIS-PAA are indicated to assess the potential clinical benefit and in vitro studies to investigate the spectrum of anti-bacterial activity and mode of action.

Preliminary investigations into developing all-D Omiganan for treating Mupirocin-resistant MRSA skin infections.

Staphylococcus aureus is the primary pathogen responsible for the majority of human skin infections, and meticillin-resistant S.aureus (MRSA) currently presents a major clinical concern. The overuse of Mupirocin, the first-line topical antibacterial drug over 30years, has led to the emergence of Mupirocin-resistant MRSA, creating a clinical concern. The antimicrobial peptide Omiganan was touted to be a promising antibacterial drug candidate due to its rapid membrane-disrupting bactericidal mode of action, entering clinical trials in 2005 as a topical gel to prevent catheter site infections. However, drug development ceased in 2009 due to a lack of efficacy. We postulate this to be due to proteolytic degradation caused by endogenous human skin proteases. Herein, we tested our hypothesis using Omiganan and its all-D enantiomer in a human skin protease stability assay, followed by anti-MRSA activity assay against of a panel of clinical MRSA isolates, a bactericidal/static determination and a time-kill assay to gauge all-D Omiganan's potential for further topical antibacterial drug development.

Sumac (Rhus coriaria L.) Represents a Considerable Antibacterial Activity Against Meticillin Susceptible and Meticillin Resistant Staphylococcus aureus

Background: Staphylococcus aureus is one of the most important pathogens and the cause of suppuration, abscess formation, a variety of pyogenic infections, and even fatal septicemia in human beings. Isolation of resistant strains of S. aureus especially meticillin-resistant one has elucidated the importance of finding new antibacterial agents. Sumac is one of the important medicinal herbs of Iranian traditional medicine (ITM). Sumac has been traditionally prescribed for some ailments with infectious etiology and therefore, it probably contains antibacterial compounds. Recently, antibacterial activities of sumac against some bacteria were studied by our team. Objective: In this article, we aimed to compare the antibacterial activities of sumac against meticillin susceptible (MSSA) and meticillin resistant S. aureus (MRSA) via minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determination. Materials and Methods: Antibacterial activity of sumac water extract was studied on 19 clinical and 1 standard strain of S. aureus via MIC and MBC determination. Based on their sensitivity to cloxacillin, these bacteria were classified as meticillin-susceptible, intermediate meticillin-resistant, and meticillin-resistant. MICs and MBCs of the extracts in these 3 groups were statistically compared via one-way analysis of variance (ANOVA) followed by a post hoc analysis (Tukey HSD test) using SPSS for Windows (version 15). Results: The results showed that in spite of different susceptibilities to cloxacillin, susceptibility to sumac extract was not different and MICs and MBCs of sumac for all clinical isolates including MSSA and MRSA were similar (P > 0.05). Conclusion: Based on previous studies, sumac extract acts against S. aureus probably through changing the cell wall properties. This activity is similar for both MRSA and MSSA. More investigation on the precise mechanism of action of this extract would be fruitful.