Difference in agr Dysfunction and Reduced Vancomycin Susceptibility between MRSA Bacteremia Involving SCCmec Types IV/IVa and I–III

Background

Dysfunction of agr, with reduced susceptibility or hetero-resistance to vancomycin, is thought to be associated with a worse outcome of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (MRSAB). However, the difference in agr dysfunction according to the SCCmec type in MRSA infection is undetermined. We compared the prevalence of agr dysfunction, reduced vancomycin susceptibility and the outcomes of SCCmec IV/IVa and I–III MRSAB.

Methods

The study included 307 cases of MRSAB. SCCmec types were determined by multiplex PCR. The clinical and microbiological features and outcomes of 58 SCCmec IV/IVa MRSAB were compared with those of 249 SCCmec I–III MRSAB.

Results

Compared with SCCmec I–III MRSAB, SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction (3% vs. 43%), vancomycin minimum inhibitory concentration (MIC) = 2 µg/mL (3% vs. 15%), and hetero-resistance to vancomycin (0% vs. 8%) (all P<0.05). However, the 30-day and S. aureus-related mortality in patients with SCCmec IV/IVa MRSAB were not different from those in patients with SCCmec I–III MRSAB in multivariate analyses (HR 1.168, 95% CI 0.705–1.938; HR 1.025, 95% CI 0.556–1.889).

Conclusions

SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction and hetero-resistance to vancomycin and a lower vancomycin MIC, compared with SCCmec I–III MRSAB. However, the outcomes of SCCmec IV/IVa MRSAB did not differ from those of SCCmec I–III MRSAB.     

Distribution of Staphylococcal Cassette Chromosome mec Types and Correlation with Comorbidity and Infection Type in Patients with MRSA Bacteremia

Background

Molecular epidemiological definitions that are based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates are considered a reliable way to distinguish between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). However, there is little information regarding the clinical features and outcomes of bacteremia patients with MRSA carrying different SCCmec types.

Methods

From January 1 through December 31, 2006, we recorded the demographic data and outcomes of 159 consecutive adult MRSA bacteremia patients from whom isolates for SCCmec analysis were collected. All participants were patients at a tertiary care center in Taiwan.

Principal Findings

The following SCCmec types were identified in MRSA isolates: 30 SCCmec II (18.9%), 87 SCCmec III (54.7%), 22 SCCmec IV (13.8%), and 20 SCCmec V (12.6%). The time from admission to the first MRSA-positive blood culture for patients infected with isolates with the SCCmec III element (mean/median, 50.7/26 days) was significantly longer than for patients infected with isolates carrying SCCmec IV or V (mean/median, 6.7/3 days for SCCmec IV; 11.1/10.5 days for SCCmec V) (P<0.05). In univariate analysis, community onset, soft tissue infection, and deep-seated infection were predictors for SCCmec IV/V. In multivariate analysis, length of stay before index culture, diabetes mellitus, and being bedridden were independent risk factors associated with SCCmec II/III.

Conclusions

These findings are in agreement with previous studies of the genetic characteristics of CA-MRSA. MRSA bacteremia with SCCmec II/III isolates occurred more among patients with serious comorbidities and prolonged hospitalization. Community onset, skin and soft tissue infection, and deep-seated infection best predicted SCCmec IV/V MRSA bacteremia.     

Comparison of Outcomes among Adult Patients with Nosocomial Bacteremia Caused by Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus: A Retrospective Cohort Study

Several studies have shown that patients with bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) have worse outcomes than those with bacteremia caused by methicillin-susceptible S. aureus (MSSA). However, only a limited number of studies have stratified the MRSA isolates into healthcare-associated (HA-) and community-associated (CA-) MRSA strains in such a comparison. This three-year retrospective cohort study, enrolling adult patients with nosocomial S. aureus bacteremia (SAB), was designed to investigate whether CA-MRSA and/or HA-MRSA strains were associated with different outcomes in comparison to MSSA in such a setting. The drug susceptibilities and staphylococcal cassette chromosome mec (SCCmec) types were determined for all of the causative isolates available. The MRSA bacteremia was further categorized into those caused by CA-MRSA strains (CA-MRSA-S bacteremia) when the causative isolates carried the type IV or V SCCmec element, those caused by HA-MRSA strains (HA-MRSA-S bacteremia) when the isolates carried the type I, II, or III SCCmec element, or unclassified MRSA bacteremia when the isolates were not available. The relevant demographic, clinical, and laboratory data were collected by reviewing the patients’ charts. The primary outcome was all-cause in-hospital mortality. A total of 353 patients were studied. The overall in-hospital mortality rate was 32.6%, with 23.3% in MSSA, 30.5% in CA-MRSA-S, 47.5% in HA-MRSA-S, and 35.3% in unclassified MRSA bacteremia, respectively. The multivariate analysis showed that HA-MRSA-S, but not CA-MRSA-S, bacteremia was associated with a significantly worse outcome compared with MSSA. The other risk factors independently associated with all-cause in-hospital mortality included the Charlson co-morbidity index, septic shock, thrombocytopenia, and persistent bacteremia. Resistance to linezolid and daptomycin was found among the MRSA isolates. The present study showed that bacteremia caused by HA-MRSA-S, but not CA-MRSA-S, was an independent risk factor for all-cause in-hospital mortality in patients with nosocomial SAB. Continuous monitoring regarding the susceptibilities of MRSA to linezolid and daptomycin is necessary.     

Outcomes and Risk Factors for Mortality among Patients Treated with Carbapenems for Klebsiella spp. Bacteremia

Background

Extensive dissemination of carbapenemase-producing Enterobacteriaceae has led to increased resistance among Klebsiella species. Carbapenems are used as a last resort against resistant pathogens, but carbapenemase production can lead to therapy failure. Identification of risk factors for mortality and assessment of current susceptibility breakpoints are valuable for improving patient outcomes.

Aim

The objective of this study was to evaluate outcomes and risk factors for mortality among patients treated with carbapenems for Klebsiella spp. bacteremia.

Methods

Patients hospitalized between 2006 and 2012 with blood cultures positive for Klebsiella spp. who received ≥ 48 hours of carbapenem treatment within 72 hours of positive culture were included in this retrospective study. Patient data were retrieved from electronic medical records. Multivariate logistic regression was used to identify risk factors for 30-day hospital mortality.

Results

One hundred seven patients were included. The mean patient age was 61.5 years and the median APACHE II score was 13 ± 6.2. Overall, 30-day hospital mortality was 9.3%. After adjusting for confounding variables, 30-day mortality was associated with baseline APACHE II score (OR, 1.17; 95% CI, 1.01–1.35; P = 0.03), length of stay prior to index culture (OR, 1.03; 95% CI, 1.00–1.06; P = 0.04), and carbapenem non-susceptible (imipenem or meropenem MIC > 1 mg/L) infection (OR, 9.08; 95% CI, 1.17–70.51; P = 0.04).

Conclusions

Baseline severity of illness and length of stay prior to culture were associated with 30-day mortality and should be considered when treating patients with Klebsiella bacteremia. These data support the change in carbapenem breakpoints for Klebsiella species.     

Teicoplanin as an Effective Alternative to Vancomycin for Treatment of MRSA Infection in Chinese Population: A Meta-analysis of Randomized Controlled Trials

Objective

To evaluate whether teicoplanin could be an alternative to vancomycin for treatment of MRSA infection in Chinese population using a meta-analysis in randomized controlled trials.

Methods

The following databases were searched: Chinese Biomedical Literature database (CBM), Chinese Journal Full-text database (CNKI), Wanfang database, Medline database, Ovid database and Cochrane Library. Articles published from 2002 to 2013 that studied teicoplanin in comparison to vancomycin in the treatment of MRSA infected patients were collected. Overall effects, publishing bias analysis and sensitivity analysis on clinical cure rate, microbiologic eradication rate and adverse events rate were performed by using Review Manager 5.2 and Stata 11.0 softwares.

Results

Twelve articles met entry criteria. There was no statistically significant difference between the two groups regarding the clinical cure rate (risk ratio [RR], teicoplanin vs vancomycin, 0.94; 95% CI, 0.74∼1.19; P = 0.60), microbiological cure rate (risk ratio [RR], teicoplanin vs vancomycin, 0.99; 95% CI, 0.91∼1.07; P = 0.74) and adverse event rate (risk ratio [RR], teicoplanin vs vancomycin, 0.86; 95% CI, 0.40∼1.84; P = 0.70).

Conclusions

The meta-analysis results indicate that the two therapies are similar in both efficacy and safety, thus teicoplanin can act as an effective alternative to vancomycin for treating patients infected by MRSA.     

Molecular typing and phenotype characterization of methicillin-resistant Staphylococcus aureus isolates from blood in Taiwan

Background

Staphylococcus aureus causes a variety of severe infections such as bacteremia and sepsis. At present, 60–80% of S. aureus isolates from Taiwan are methicillin resistant (MRSA). It has been shown that certain MRSA clones circulate worldwide. The goals of this study were to identify MRSA clones in Taiwan and to correlate the molecular types of isolates with their phenotypes.

Methods

A total of 157 MRSA isolates from bacteremic patients were collected from nine medical centers. They were typed based on polymorphisms in agr, SCCmec, MLST, spa, and dru. Phenotypes characterized included Panton-Valentine leucocidin (pvl), inducible macrolide-lincosamide-streptogramin B resistance (MLSBi), vancomycin (VA) and daptomycin (DAP) minimal inhibitory concentrations (MIC), and superantigenic toxin gene profiles. Difference between two consecutive samples was determined by Mann-Whitney-U test, and difference between two categorical variables was determined by Fisher''s exact test.

Results

Four major MRSA clone complexes CC1, CC5, CC8, and CC59 were found, including 4 CC1, 9 CC5, 111 CC8, and 28 CC59 isolates. These clones had the following molecular types: CC1: SCCmecIV and ST573; CC5: SCCmecII and ST5; CC8: SCCmecIII, ST239, and ST241, and CC59: SCCmecIV, SCCmecV_T, ST59, and ST338. The toxin gene profiles of these clones were CC1: sec-seg-(sei)-sell-selm-(seln)-selo; CC5: sec-seg-sei-sell-selm-(seln)-selp-tst1; CC8: sea-selk-selq, and CC59: seb-selk-selq. Most isolates with SCCmecV_T, ST59, spat437, and dru11 types were pvl ⁺ (13 isolates), while multidrug resistance (≥4 antimicrobials) were associated with SCCmecIII, ST239, spa t037, agrI, and dru14 (119 isolates) (p<0.001). One hundred and twenty four isolates with the following molecular types had higher VA MIC: SCCmecII and SCCmecIII; ST5, ST239, and ST241; spa t002, t037, and t421; dru4, dru10, dru12, dru13, and dru14 (p<0.05). No particular molecular types were found to be associated with MLSBi phenotype.

Conclusions

Four major MRSA clone complexes were found in Taiwan. Further studies are needed to delineate the evolution of MRSA isolates.     

Quantifying Cost-Effectiveness of Controlling Nosocomial Spread of Antibiotic-Resistant Bacteria: The Case of MRSA

Background

The costs and benefits of controlling nosocomial spread of antibiotic-resistant bacteria are unknown.

Methods

We developed a mathematical algorithm to determine cost-effectiveness of infection control programs and explored the dynamical interactions between different epidemiological variables and cost-effectiveness. The algorithm includes occurrence of nosocomial infections, attributable mortality, costs and efficacy of infection control and how antibiotic-resistant bacteria affect total number of infections: do infections with antibiotic-resistant bacteria replace infections caused by susceptible bacteria (replacement scenario) or occur in addition to them (addition scenario). Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia was used for illustration using observational data on S. aureus bacteremia (SAB) in our hospital (n = 189 between 2001–2004, all being methicillin-susceptible S. aureus [MSSA]).

Results

In the replacement scenario, the costs per life year gained range from € 45,912 to € 6590 for attributable mortality rates ranging from 10% to 50%. Using € 20,000 per life year gained as a threshold, completely preventing MRSA would be cost-effective in the replacement scenario if attributable mortality of MRSA is ≥21%. In the addition scenario, infection control would be cost saving along the entire range of estimates for attributable mortality.

Conclusions

Cost-effectiveness of controlling antibiotic-resistant bacteria is highly sensitive to the interaction between infections caused by resistant and susceptible bacteria (addition or replacement) and attributable mortality. In our setting, controlling MRSA would be cost saving for the addition scenario but would not be cost-effective in the replacement scenario if attributable mortality would be <21%.     

In Vitro Activity of Sodium New Houttuyfonate Alone and in Combination with Oxacillin or Netilmicin against Methicillin-Resistant Staphylococcus aureus

Background

Staphylococcus aureus can cause severe infections, including bacteremia and sepsis. The spread of methicillin-resistant Staphylococcus aureus (MRSA) highlights the need for novel treatment options. Sodium new houttuyfonate (SNH) is an analogue of houttuynin, the main antibacterial ingredient of Houttuynia cordata Thunb. The aim of this study was to evaluate in vitro activity of SNH and its potential for synergy with antibiotics against hospital-associated MRSA.

Methodology

A total of 103 MRSA clinical isolates recovered in two hospitals in Beijing were evaluated for susceptibility to SNH, oxacillin, cephalothin, meropenem, vancomycin, levofloxacin, minocycline, netilmicin, and trimethoprim/sulfamethoxazole by broth microdilution. Ten isolates were evaluated for potential for synergy between SNH and the antibiotics above by checkerboard assay. Time-kill analysis was performed in three isolates to characterize the kill kinetics of SNH alone and in combination with the antibiotics that engendered synergy in checkerboard assays. Besides, two reference strains were included in all assays.

Principal Findings

SNH inhibited all test strains with minimum inhibitory concentrations (MICs) ranging from 16 to 64 µg/mL in susceptibility tests, and displayed inhibition to bacterial growth in concentration-dependent manner in time-kill analysis. In synergy studies, the combinations of SNH-oxacillin, SNH-cephalothin, SNH-meropenem and SNH-netilmicin showed synergistic effects against 12 MRSA strains with median fractional inhibitory concentration (FIC) indices of 0.38, 0.38, 0.25 and 0.38 in checkerboard assays. In time-kill analysis, SNH at 1/2 MIC in combination with oxacillin at 1/128 to 1/64 MIC or netilmicin at 1/8 to 1/2 MIC decreased the viable colonies by ≥2log₁₀ CFU/mL.

Conclusions/Significance

SNH demonstrated in vitro antibacterial activity against 103 hospital-associated MRSA isolates. Combinations of sub-MIC levels of SNH and oxacillin or netilmicin significantly improved the in vitro antibacterial activity against MRSA compared with either drug alone. The SNH-based combinations showed promise in combating MRSA.     

Nasal Carriage of Methicillin-Resistant Staphylococcus aureus among Pediatricians in Taiwan

Background

Health care workers (HCWs) are at the interface between hospitals and communities. The survey for methicillin-resistant Staphylococcus aureus (MRSA) carriage among HCWs has mostly been conducted to investigate outbreaks or endemics. Community-associated MRSA are prevalent among children in Taiwan. We conducted this study to better understand the carriage rate of MRSA among pediatricians in non-outbreak situations in Taiwan,.

Methods

A total of 220 pediatricians from Taiwan who attended the annual meeting of Taiwan Pediatric Association in April, 2010 were recruited to participate in this study and were sampled from the nares for the detection of MRSA by polymerase chain reaction (PCR) and further by culture. The following molecular analyses were performed, including pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), typing of staphylococcal cassette chromosome mec (SCCmec) and the presence of Panton-Valentine leukocidin (PVL) genes.

Results

MRSA was detected from 15 attendees (6.8%) by PCR. MRSA-colonized attendees had a significantly lower rate (0.041) of working in the medical center, while borderline significantly higher rate of working in the Regional Hospital (p=0.056), than those without MRSA colonization. From those 15 samples, 12 MRSA isolates were identified by culture and molecularly characterized. Three PFGE patterns, two sequence types (ST 59, ST 508), and two SCCmec types (IV and V_T) were identified, respectively. Five isolates, including three carrying SCCmec types V_T, were PVL-positive. All 12 isolates were susceptible to vancomycin, teicoplanin, linezolid, fusidic acid, trimethoprim/sulfamethoxazole, and doxycyclin, and resistant to penicillin.

Conclusion/significance

Around seven percent of pediatricians in Taiwan harbored CA-MRSA in their nares.     

Systematic Review and Meta-Analysis of the Epidemiology of Vancomycin-Intermediate and Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Isolates

Background

Vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) are associated with vancomycin treatment failure, and are becoming an increasing public health problem. Therefore, we undertook this study of 91 published studies and made subgroup comparisons of hVISA/VISA incidence in different study years, locations, and types of clinical samples. We also analyzed the genetic backgrounds of these strains.

Methods

A systematic literature review of relevant articles published in PubMed and EMBASE from January 1997 to August 2014 was conducted. We selected and assessed journal articles reporting the prevalence rates of hVISA/VISA.

Results

The pooled prevalence of hVISA was 6.05% in 99,042 methicillin-resistant S. aureus (MRSA) strains and that of VISA was 3.01% in 68,792 MRSA strains. The prevalence of hVISA was 4.68% before 2006, 5.38% in 2006–2009, and 7.01% in 2010–2014. VISA prevalence was 2.05%, 2.63%, and 7.93%, respectively. In a subgroup analysis of different isolation locations, the prevalence of hVISA strains was 6.81% in Asia and 5.60% in Europe/America, and that of VISA was 3.42% and 2.75%, respectively. The frequencies of hVISA isolated from blood culture samples and from all clinical samples were 9.81% and 4.68%, respectively, and those of VISA were 2.00% and 3.07%, respectively. The most prevalent genotype was staphylococcal cassette chromosome mec (SCCmec) II, which accounted for 48.16% and 37.74% of hVISA and VISA, respectively. Sequence Type (ST) 239 was most prevalent.

Conclusion

The prevalence of hVISA/VISA has been increasing in recent years, but has been grossly underestimated. Its incidence is higher in Asia than in Europe/America. hVISA is isolated from blood culture samples more often than from other samples. These strains are highly prevalent in epidemic MRSA strains. This study clarifies the epidemiology of hVISA/VISA and indicates that the detection of these strains and the control of nosocomial infections must be strengthened.     

Prevalence and Trends of Staphylococcus aureus Bacteraemia in Hospitalized Patients in South Africa, 2010 to 2012: Laboratory-Based Surveillance Mapping of Antimicrobial Resistance and Molecular Epidemiology

Introduction

We aimed to obtain an in-depth understanding on recent antimicrobial resistance trends and molecular epidemiology trends of S. aureus bacteraemia (SAB).

Methods

Thirteen academic centres in South Africa were included from June 2010 until July 2012. S. aureus susceptibility testing was performed on the MicroScan Walkaway. Real-time PCR using the LightCycler 480 II was done for mecA and nuc. SCCmec and spa-typing were finalized with conventional PCR. We selected one isolate per common spa type per province for multilocus sequence typing (MLST).

Results

S. aureus from 2709 patients were included, and 1231 (46%) were resistant to methicillin, with a significant decline over the three-year period (p-value = 0.003). Geographical distribution of MRSA was significantly higher in Gauteng compared to the other provinces (P<0.001). Children <5 years were significantly associated with MRSA with higher rates compared to all other age groups (P = 0.01). The most prevalent SCCmec type was SCCmec type III (531 [41%]) followed by type IV (402 [31%]). Spa-typing discovered 47 different spa-types. The five (87%) most common spa-types were t037, t1257, t045, t064 and t012. Based on MLST, the commonest was ST612 clonal complex (CC8) (n = 7) followed by ST5 (CC5) (n = 4), ST36 (CC30) (n = 4) and ST239 (CC8) (n = 3).

Conclusions

MRSA rate is high in South Africa. Majority of the isolates were classified as SCCmec type III (41%) and type IV (31%), which are typically associated with hospital and community- acquired infections, respectively. Overall, this study reveals the presence of a variety of hospital-acquired MRSA clones in South Africa dominance of few clones, spa 037 and 1257. Monitoring trends in resistance and molecular typing is recommended to detect changing epidemiological trends in AMR patterns of SAB.     

Association between the AUC0-24/MIC Ratio of Vancomycin and Its Clinical Effectiveness: A Systematic Review and Meta-Analysis

Background

A target AUC_0-24/MIC ratio of 400 has been associated with its clinical success when treating Staphylococcus aureus infections but is not currently supported by state-of-the-art evidence-based research.

Objective

This current systematic review aimed to evaluate the available evidence for the association between the AUC_0-24/MIC ratio of vancomycin and its clinical effectiveness on hospitalized patients and to confirm the existing target value of 400.

Methods

PubMed, Embase, Web of Sciences, the Cochrane Library and two Chinese literature databases (CNKI, CBM) were systematically searched. Manual searching was also applied. Both RCTs and observational studies comparing the clinical outcomes of high AUC_0-24/MIC groups versus low AUC_0-24/MIC groups were eligible. Two reviewers independently extracted the data. The primary outcomes were mortality and infection treatment failure. Risk ratios (RRs) with 95% confidence intervals (95%CIs) were calculated.

Results

No RCTs were retrieved. Nine cohort studies were included in the meta-analysis. Mortality rates were significantly lower in high AUC_0-24/MIC groups (RR = 0.47, 95%CI = 0.31–0.70, p<0.001). The rates of infection treatment failure were also significantly lower in high AUC/MIC groups and were consistent after correcting for heterogeneity (RR = 0.39, 95%CI = 0.28–0.55, p = 0.001). Subgroup analyses showed that results were consistent whether MIC values were determined by broth microdilution (BMD) method or Etest method. In studies using the BMD method, breakpoints of AUC_0-24/MIC all fell within 85% to 115% of 400.

Conclusions

This meta-analysis demonstrated that achieving a high AUC_0-24/MIC of vancomycin could significantly decrease mortality rates by 53% and rates of infection treatment failure by 61%, with 400 being a reasonable target.     

Comparison of Biofilm Formation between Major Clonal Lineages of Methicillin Resistant Staphylococcus aureus

Objectives

Epidemic methicillin-resistant S. aureus (MRSA) clones cause infections in both hospital and community settings. As a biofilm phenotype further facilitates evasion of the host immune system and antibiotics, we compared the biofilm-forming capacities of various MRSA clones.

Methods

Seventy-six MRSA classified into 13 clones (USA300, EMRSA-15, Hungarian/Brazilian etc.), and isolated from infections or from carriers were studied for biofilm formation under static and dynamic conditions. Static biofilms in microtitre plates were quantified colorimetrically. Dynamic biofilms (Bioflux 200, Fluxion, USA) were studied by confocal laser-scanning and time-lapse microscopy, and the total volume occupied by live/dead bacteria quantified by Volocity 5.4.1 (Improvision, UK).

Results

MRSA harbouring SCCmec IV produced significantly more biomass under static conditions than SCCmec I–III (P = 0.003), and those harbouring SCCmec II significantly less than those harbouring SCCmec I or III (P<0.001). In the dynamic model, SCCmec I–III harbouring MRSA were significantly better biofilm formers than SCCmec IV (P = 0.036). Only 16 strains successfully formed biofilms under both conditions, of which 13 harboured SCCmec IV and included all tested USA300 strains (n = 3). However, USA300 demonstrated remarkably lower percentages of cell-occupied space (6.6%) compared to the other clones (EMRSA-15 = 19.0%) under dynamic conditions. Time-lapse microscopy of dynamic biofilms demonstrated that USA300 formed long viscoelastic tethers that stretched far from the point of attachment, while EMRSA-15 consisted of micro-colonies attached densely to the surface.

Conclusions

MRSA harbouring SCCmec types IV and I–III demonstrate distinct biofilm forming capacities, possibly owing to their adaptation to the community and hospital settings, respectively. USA300 demonstrated abundant biofilm formation under both conditions, which probably confers a competitive advantage, contributing to its remarkable success as a pathogen.     

Generation of novel cationic antimicrobial peptides from natural non-antimicrobial sequences by acid-amide substitution

Background

The accessory gene regulator (agr) is a quorum sensing cluster of genes which control colonization and virulence in Staphylococcus aureus. We evaluated agr function in community- (CA) and healthcare-associated (HA) MRSA, to compare the pharmacodynamics and bactericidal activity of vancomycin against agr functional and dysfunctional HA-MRSA and CA-MRSA.

Methods

40 clinical isolates of MRSA from the Canadian Nosocomial Infection Surveillance Program were evaluated for delta-haemolysin production, as a surrogate marker of agr function. Time kill experiments were performed for vancomycin at 0 to 64 times the MIC against an initial inoculum of 10⁶ and 10⁸ cfu/ml of agr functional and dysfunctional CA-MRSA and HA-MRSA and these data were fit to a hill-type pharmacodynamic model.

Results

15% isolates were agr dysfunctional, which was higher among HA-MRSA (26.3%) versus CA-MRSA (4.76%). Against a low initial inoculum of 10⁶ cfu/ml of CA-MRSA, vancomycin pharmacodynamics were similar among agr functional and dysfunctional strains. However, against a high initial inoculum of 10⁸ cfu/ml, killing activity was notably attenuated against agr dysfunctional CA-MRSA (USA400) and HA-MRSA (USA100). CA-MRSA displayed a 20.0 fold decrease in the maximal reduction in bacterial counts (Emax) which was 3.71 log₁₀ CFU/ml for agr functional vs. 2.41 log₁₀ CFU/ml for agr dysfunctional MRSA (p = 0.0007).

Conclusions

Dysfunction in agr was less common among CA-MRSA vs. HA-MRSA. agr dysfunction demonstrated an impact on vancomycin bactericidal activity and pharmacodynamics against a high initial inoculum of CA-MRSA and HA-MRSA, which may have implications for optimal antimicrobial therapy against persistent, difficult to treat MRSA infections.     

No Outbreak of Vancomycin and Linezolid Resistance in Staphylococcal Pneumonia over a 10-Year Period

Background

Staphylococci can cause wound infections and community- and nosocomial-acquired pneumonia, among a range of illnesses. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) have been rapidly increasing as a cause of infections worldwide in recent decades. Numerous reports indicate that S. aureus and MRSA are becoming resistant to many antibiotics, which makes them very dangerous. Therefore, this study retrospectively investigated the resistance to antimicrobial agents in all hospitalized patients suffering from community- or nosocomial-acquired pneumonia due to S. aureus and MRSA.

Methods

Information from the study groups suffering from either community- or nosocomial-acquired pneumonia caused by S. aureus or MRSA was gathered by searching records from 2004 to 2014 at the HELIOS Clinic Wuppertal, Witten/Herdecke University, Germany. The findings of antibiotic resistance were analyzed after the evaluation of susceptibility testing for S. aureus and MRSA.

Results

Total of 147 patients (63.9%, 95% CI 57.5%–69.8%), mean age 67.9 ± 18.5 years, with pneumonia triggered by S. aureus, and 83 patients (36.1%, 95% CI 30.2%–42.5%), mean age 72.3 ± 13.8 years, with pneumonia due to MRSA. S. aureus and MRSA developed no resistance to vancomycin (P = 0.019 vs. < 0.0001, respectively) or linezolid (P = 0.342 vs. < 0.0001, respectively). MRSA (95.3%) and S. aureus (56.3%) showed a high resistance to penicillin. MRSA (87.7%) was also found to have a high antibiotic resistance against ß-lactam antibiotics, compared to S. aureus (9.6%). Furthermore, MRSA compared to S. aureus, respectively, had increased antibiotic resistance to ciprofloxacin (90.1% vs. 17.0%), cefazolin (89.7% vs. 10.2%), cefuroxime (89.0% vs. 9.1%), levofloxacin (88.2% vs. 18.4%), clindamycin (78.0% vs. 14.7%), and erythromycin (76.5% vs. 20.8%).

Conclusion

No development of resistance was found to vancomycin and linezolid in patients with pneumonia caused by S. aureus and MRSA.     

High Mortality of Disseminated Non-Tuberculous Mycobacterial Infection in HIV-Infected Patients in the Antiretroviral Therapy Era

Background

Little information is available on the mortality and risk factors associated with death in disseminated non-tuberculous mycobacterial infection (dNTM) in HIV-infected patients in the ART-era.

Methods

In a single-center study, HIV-infected dNTM with positive NTM culture from sterile sites between 2000 and 2013 were analysed. The clinical characteristics at commencement of anti-mycobacterial treatment (baseline) were compared between those who survived and died.

Results

Twenty-four patients were analyzed. [The median CD4 27/μL (range 2–185)]. Mycobacterium avium and M. intracellulare accounted for 20 (83%) and 3 (13%) of isolated NTM. NTM bacteremia was diagnosed in 15 (63%) patients. Seven (29%) patients died, and NTM bacteremia was significantly associated with mortality (p = 0.022). The baseline CD4 count was significantly lower in the non-survivors than the survivors (median 7/μL versus 49, p = 0.034). Concomitant AIDS-defining diseases or malignancies were not associated with mortality. Immune-reconstitution syndrome (IRS) occurred to 19 (79%) patients (8 paradoxical and 11 unmasking), and prognosis tended to be better in unmasking-IRS than the other patients (n = 13) (p = 0.078). Patients with paradoxical-IRS had marginally lower CD4 count and higher frequency of bacteremia than those with unmasking-IRS (p = 0.051, and 0.059). Treatment with systemic corticosteroids was applied in 63% and 55% of patients with paradoxical and unmasking-IRS, respectively.

Conclusion

dNTM in HIV-infected patients resulted in high mortality even in the ART-era. NTM bacteremia and low CD4 count were risk factors for death, whereas patients presented with unmasking-IRS had marginally better prognosis. IRS occurred in 79% of the patients, suggesting difficulty in the management of dNTM.     

Body Mass Index,High-Sensitivity C-Reactive Protein and Mortality in Chinese with Coronary Artery Disease

Background

To investigate single and joint associations of body mass index (BMI) and serum high-sensitivity C-reactive protein (hsCRP) with death.

Methods

The study included 1871 coronary artery disease (CAD) patients aged 40–85 year-old recruited from 2008 to 2011. Cox regression models were used to estimate the association of BMI and hsCRP with mortality. The data was analyzed in 2014.

Results

During 3.1 years follow-up, 141 deaths were recorded, 110 died of cardiovascular disease (CVD). After adjustment of major CVD risk factors, there was a J-shaped association between BMI and all-cause and CVD mortality, and a positive association between hsCRP and mortality. The J-shaped association of BMI with mortality was present among patients who never smoked or with elevated hsCRP (≥3.0 mg/L). Compared with overweight (BMI 24–27.9 kg/m²) patients with normal hsCRP (<3.0 mg/L), obese patients (BMI≥28 kg/m²) with elevated hsCRP had a 3.41-fold risk of all-cause mortality (95% CI 1.49–7.80) and a 3.50-fold risk of CVD mortality (1.40–8.75), lean patients (BMI<24 kg/m²) with elevated hsCRP concentration had a 2.54-fold risk of all-cause mortality (1.36–4.74) and a 2.36-fold risk of CVD mortality (1.19–4.70).

Conclusions

The association pattern between baseline BMI and mortality changed among different baseline hsCRP concentrations, indicating that low-grade inflammation may be related to BMI and secondary prognosis of CAD.     

Assessments of Thioridazine as a Helper Compound to Dicloxacillin against Methicillin-Resistant Staphylococcus aureus: In Vivo Trials in a Mouse Peritonitis Model

Introduction

The rise in antimicrobial resistance is a major global concern and requires new treatment strategies. The use of helper compounds, such as thioridazine (TDZ), an antipsychotic drug, in combination with traditional antibiotics must be investigated.

Objectives

The aim of this study was to investigate the efficacy of TDZ as a helper compound for dicloxacillin (DCX) against methicillin-resistant Staphylococcus aureus (MRSA) in vivo, and compare the combination treatment of DCX+TDZ with vancomycin (VAN).

Methods

Mice were inoculated with an intraperitoneal (IP) injection of MRSA (10⁸ CFU) and treated in a 12-hour cycle for 48 hours. By termination, bacterial quantities in a peritoneal flush, spleen and kidneys were obtained. In the main trial the drugs were administered subcutaneously in five treatment groups: 1) DCX, 2) TDZ, 3) DCX+TDZ, 4) VAN, 5) SALINE. Additional smaller studies with IP administration and higher subcutaneous dosages (×1.5 and ×4) of the drugs were subsequently performed.

Results

In the main trial no significant differences were found between DCX+TDZ and DCX or TDZ alone (p≥0.121–0.999). VAN performed significantly better than DCX+TDZ on all bacteriological endpoints (p<0.001). Higher subcutaneous dosages of DCX and TDZ improved the antibacterial efficacy, but the combination treatment was still not significantly better than monotherapy. IP drug administration of DCX+TDZ revealed a significantly better antibacterial effect than DCX or TDZ alone (p<0.001) but not significantly different from VAN (p>0.999).

Conclusion

In conclusion, TDZ did not prove to be a viable helper compound for dicloxacillin against MRSA in subcutaneous systemic treatment. However, IP-administration of DCX+TDZ, directly at the infection site resulted in a synergetic effect, with efficacy comparable to that of VAN.     

MRSA Clonal Complex 22 Strains Harboring Toxic Shock Syndrome Toxin (TSST-1) Are Endemic in the Primary Hospital in Gaza,Palestine

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in both community and healthcare-related settings worldwide. Current knowledge regarding the epidemiology of S. aureus and MRSA in Gaza is based on a single community-based carriage study. Here we describe a cross-sectional analysis of 215 clinical isolates collected from Al-Shifa Hospital in Gaza during 2008 and 2012.

Methods

All isolates were characterized by spa typing, SCCmec typing, and detection of genes encoding Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST-1). Representative genotypes were also subjected to multilocus sequence typing (MLST). Antibiotic susceptibility testing was performed using VITEK2 and MicroScan.

Results

MRSA represented 56.3% of all S. aureus strains, and increased in frequency from 2008 (54.8%) to 2012 (58.4%). Aside from beta-lactams, resistance was observed to tetracycline, erythromycin, clindamycin, gentamicin, and fluoroquinolones. Molecular typing identified 35 spa types representing 17 MLST clonal complexes (CC), with spa 998 (Ridom t223, CC22) and spa 70 (Ridom t044, CC80) being the most prevalent. SCCmec types I, III, IV, V and VI were identified among MRSA isolates, while type II was not detected. PVL genes (lukF/S-PV) were detected in 40.0% of all isolates, while the TSST-1 gene (tst) was detected in 27.4% of all isolates, with surprisingly high frequency within CC22 (70.4%). Both PVL and TSST-1 genes were found in several isolates from 2012.

Conclusions

Molecular typing of clinical isolates from Gaza hospitals revealed unusually high prevalence of TSST-1 genes among CC22 MRSA, which is noteworthy given a recent community study describing widespread carriage of a CC22 MRSA clone known as the ‘Gaza strain’. While the latter did not address TSST-1, tst-positive spa 998 (Ridom t223) has been detected in several neighboring countries, and described as endemic in an Italian NICU, suggesting international spread of a ‘Middle Eastern variant’ of pandemic CC22 strain EMRSA-15.     

Serum Cystatin C Reflects Angiographic Coronary Collateralization in Stable Coronary Artery Disease Patients with Chronic Total Occlusion

Objective

We investigated whether and to what extent cystatin C was associated with angiographic coronary collateralization in patients with stable coronary artery disease and chronic total occlusion.

Methods

Serum levels of cystatin C and high-sensitive C-reactive protein (hsCRP) and glomerular filtration rate (GFR) were determined in 866 patients with stable angina and angiographic total occlusion of at least one major coronary artery. The degree of collaterals supplying the distal aspect of a total occlusion from the contra-lateral vessel was graded as poor (Rentrop score of 0 or 1) or good coronary collateralization (Rentrop score of 2 or 3).

Results

In total, serum cystatin C was higher in patients with poor collateralization than in those with good collateralization (1.08 ± 0.32 mg/L vs. 0.90 ± 0.34 mg/L, P < 0.001), and correlated inversely with Rentrop score (adjusted Spearmen’s r = -0.145, P < 0.001). The prevalence of poor coronary collateralization increased stepwise with increasing cystatin C quartiles (P for trend < 0.001). After adjusting for age, gender, risk factors for coronary artery disease, GFR and hsCRP, serum cystatin C ≥ 0.97 mg/L remained independently associated with poor collateralization (OR 2.374, 95% CI 1.660 ~ 3.396, P < 0.001). The diagnostic value of cystatin C levels for detecting poor coronary collateralization persisted regardless of age, gender, presence or absence of diabetes, hypertension or renal dysfunction.

Conclusions

Serum cystatin C reflects angiographic coronary collateralization in patients with stable coronary artery disease, and cystatin C ≥ 0.97 mg/L indicates a great risk of poor coronary collaterals.