Determining vancomycin Etest MICs in patients with MRSA bloodstream infection does not support switching antimicrobials

Clinical epidemiology and case fatality due to antimicrobial resistance in Germany: a systematic review and meta-analysis, 1 January 2010 to 31 December 2021

BackgroundAntimicrobial resistance (AMR) is of public health concern worldwide.AimWe aimed to summarise the German AMR situation for clinicians and microbiologists.MethodsWe conducted a systematic review and meta-analysis of 60 published studies and data from the German Antibiotic-Resistance-Surveillance (ARS). Primary outcomes were AMR proportions in bacterial isolates from infected patients in Germany (2016-2021) and the case fatality rates (2010-2021). Random and fixed (common) effect models were used to calculate pooled proportions and pooled case fatality odds ratios, respectively.ResultsThe pooled proportion of meticillin resistance in Staphylococcus aureus infections (MRSA) was 7.9% with a declining trend between 2014 and 2020 (odds ratio (OR) = 0.89; 95% CI: 0.886-0.891; p < 0.0001), while vancomycin resistance in Enterococcus faecium (VRE) bloodstream infections increased (OR = 1.18; (95% CI: 1.16-1.21); p < 0.0001) with a pooled proportion of 34.9%. Case fatality rates for MRSA and VRE were higher than for their susceptible strains (OR = 2.29; 95% CI: 1.91-2.75 and 1.69; 95% CI: 1.22-2.33, respectively). Carbapenem resistance in Gram-negative pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Enterobacter spp. and Escherichia coli) was low to moderate (< 9%), but resistance against third-generation cephalosporins and fluoroquinolones was moderate to high (5-25%). Pseudomonas aeruginosa exhibited high resistance against carbapenems (17.0%; 95% CI: 11.9-22.8), third-generation cephalosporins (10.1%; 95% CI: 6.6-14.2) and fluoroquinolones (24.9%; 95% CI: 19.3-30.9). Statistical heterogeneity was high (I2 > 70%) across studies reporting resistance proportions.ConclusionContinuous efforts in AMR surveillance and infection prevention and control as well as antibiotic stewardship are needed to limit the spread of AMR in Germany.

Bimetallic oxide Cu2O@MnO2 with exposed phase interfaces for dual-effect purification of indoor formaldehyde and pathogenic bacteria

The combination of materials with different functions is an optimal strategy for synchronously removing various indoor pollutants. For multiphase composites, exposing all components and their phase interfaces fully to the reaction atmosphere is a critical problem that needs to be solved urgently. Here, a bimetallic oxide Cu2O@MnO2 with exposed phase interfaces was prepared by a surfactant-assisted two-step electrochemical method, which shows a composite structure of non-continuously dispersed Cu2O particles anchored on flower-like MnO2. Compared with the pure catalyst MnO2 and bacteriostatic agent Cu2O, Cu2O@MnO2 respectively shows superior dynamic formaldehyde (HCHO) removal efficiency (97.2% with a weight hourly space velocity of 120 000 mL g-1 h-1) and pathogen inactivation ability (the minimum inhibitory concentration for 104 CFU mL-1 Staphylococcus aureus is 10 μg mL-1). According to material characterization and theoretical calculation, its excellent catalytic-oxidative activity is attributable to the electron-rich region at the phase interface which is fully exposed to the reaction atmosphere, inducing the capture and activation of O2 on the material surface, and then promoting the generation of reactive oxygen species that can be used for the oxidative-removal of HCHO and bacteria. Additionally, as a photocatalytic semiconductor, Cu2O further enhances the catalytic ability of Cu2O@MnO2 under the assistance of visible light. This work will provide efficient theoretical guidance and a practical basis for the ingenious construction of multiphase coexisting composites in the field of multi-functional indoor pollutant purification strategies.

Simulated Enzyme Activity and Efficient Antibacterial Activity of Copper-Doped Single-Atom Nanozymes

Nanozymes with good biocompatibility are novel antibacterial agents because they mimic the structure and properties of enzymes and destroy bacterial structures by generating reactive oxygen species in large quantities. Herein, we synthesized a Cu single-atom nanozyme (Cu-N-C) with intrinsic peroxidase- and oxidase-like activities. Cu-N-C can generate ·OH and O₂^·- during oxidase-catalyzed reactions, which have good antibacterial effects. Meanwhile, the antimicrobial performance can be further enhanced by light emitting diode light incubation due to photocatalysis. Lethal disruption of the membrane structure was confirmed by biofilm staining and scanning electron microscopy analysis. Notably, the antibacterial effect of Cu-N-C (MIC = 16 μg/mL) was significantly better than that of vancomycin (MIC = 1500 μg/mL), a commonly used drug for methicillin-resistant Staphylococcus aureus, and Cu-N-C outperformed the positive control cephalexin and gentamicin in terms of resistance development (27.3% less production of drug-resistant bacteria). Good biocompatibility was also verified using the MTT method, hemolysis analysis, and routine blood measurements in mice. The results of this work suggest that Cu-N-C has great potential for clinical applications as an efficient metal antimicrobial agent.

Automated Susceptibility Testing With Vitek 2 Compared to MicroScan Reduces Vancomycin Alternative Therapy For Methicillin-Resistant Staphylococcus Aureus Bacteremia

OBJECTIVES

Variability in minimum inhibitory concentration (MIC) with automated susceptibility testing instruments may influence methicillin-resistant Staphylococcus aureus (MRSA) treatment. The purpose of this study was to evaluate the difference in vancomycin MIC values and the impact on vancomycin alternative therapy for MRSA bacteremia using the MicroScan and VITEK 2 automated systems.

METHODS

This was a retrospective multicenter cohort study of adult patients with MRSA bacteremia. Patients were stratified by susceptibility testing with MicroScan (May 2013-December 2016) or VITEK 2 (June 2017-February 2020). The primary outcome was vancomycin alternative therapy use. Secondary endpoints included MRSA MIC, 30-day mortality, 30- and 90-day readmission, and hospital length of stay (LOS).

RESULTS

A total of 193 patients were included for analysis: 89 in the MicroScan group and 104 in the VITEK 2 group. Vancomycin alternative therapy use was higher in the MicroScan group than the VITEK 2 group (56.2% vs 20.2%; p <0.001). Median MIC value was 2 mg/L and 1 mg/L for MicroScan and VITEK 2, respectively (p <0.001). Median hospital LOS was shorter in the VITEK 2 period (16 vs 12 days; p = 0.02). Thirty-day mortality (10.1% vs 7.7%; p = 0.555) and 90-day readmission (34.8% vs 29.8%; p = 0.457) did not significantly differ between MicroScan and VITEK 2 groups.

CONCLUSIONS

VITEK 2 use was associated with lower reported vancomycin MICs and less use of vancomycin alternative therapy.

Genotyping of methicillin-resistant Staphylococcus aureus isolates causing invasive infections using spa typing and their correlation with antibiotic susceptibility

The antibiotic susceptibility patterns were correlated with particular spa types, and this correlation would help physicians select appropriate antibiotics for treatment of invasive MRSA infections. The aim of this research was to investigate invasive methicillin-resistant Staphylococcus aureus (MRSA) through delineatingthe molecular typing results and correlating them with antibiotic susceptibility. Totally 670 non-duplicate mecA+MRSA isolates from patients with invasive infections were collected from a 5-year nationwide antimicrobial surveillance program (TIST), and 58 spa types were identified among 639 (95.4%) isolates by determining the allelic profile of the spa gene with PCR and nucleotide sequencing. Six major types, including spa t002 (103, 15.3%) and t037 (253, 37.8%), were classified as healthcare-associated MRSA (HA-MRSA, 53.1%); while t437 (151, 22.5%), t441 (13, 1.9%), t1081 (19, 2.8%), and t3525 (14, 2.1%) were classified as community-associated MRSA (CA-MRSA, 29.4%). Antimicrobial susceptibility was performed with agar or microbroth dilutions for various antibiotics and the Etest was used for both daptomycin and vancomycin. The declining trend in the vancomycin MIC was in parallel with an increasing frequency of CA-MRSA. The antibiotic susceptibility patterns were correlated with particular spa types, and this correlation would help physicians select appropriate antibiotics for treatment of invasive MRSA infections.

Association between high vancomycin minimum inhibitory concentration and clinical outcomes in patients with methicillin-resistant Staphylococcus aureus bacteremia: a meta-analysis

PURPOSE

To assess the relationship between high vancomycin minimum inhibitory concentrations (MIC), in patients with methicillin-resistant Staphylococcus aureus bacteremia (MRSAB), and both mortality and complicated bacteremia.

METHODS

Embase, Medline, EBM, Scopus and Web of Science were searched for studies published from January 1st 2014 to February 29th 2020. "High" vancomycin MIC cut off was defined as ≥ 1.5 mg/L. Three referees independently reviewed studies that compared outcomes in patients with MRSAB stratified by vancomycin MIC. Subgroup analyses were performed for rates of mortality and complicated bacteremia.

RESULTS

A total of 13 studies with 2089 patients were included. Overall, mortality was 27.7% and 23.3% in the high and low vancomycin MIC group, respectively. No significant difference was found between vancomycin MIC groups for overall mortality, in-hospital mortality, late mortality, persistent bacteremia, severe sepsis or septic shock, acute renal failure, septic emboli or endocarditis, and osteomyelitis or septic arthritis. Early mortality was significantly associated with low vancomycin MIC. Mortality in studies using broth microdilution method (BMD) and need for mechanical ventilation were significantly associated with high vancomycin MIC.

CONCLUSION

Overall mortality and complicated bacteremia were not significantly associated with high vancomycin MICs in a patient with MRSAB. Randomized controlled trials to assess the utility of vancomycin MIC values in predicting mortality and other adverse clinical outcomes are warranted.

Discordance of vancomycin minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus at 2 μg/mL between Vitek II, E-test, and Broth Microdilution

Background

Vancomycin, the first line antibiotic for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, is often administered inappropriately when MIC is greater than 2 µg/mL, including ‘susceptible’ strains. This study assessed the discordance of vancomycin minimum inhibitory concentration (MIC) for methicillin-resistant Staphylococcus aureus (MRSA).

Methods

In total, 229 MRSA isolates from blood cultures collected between 2009 and 2015 at a tertiary hospital in Taiwan were examined. The MICs of vancomycin were measured using Vitek 2, E-test, and standard broth microdilution at the level of 2 µg/mL.

Results

The geometric mean of the MICs of hospital-acquired MRSA was higher than that of community-acquired MRSA (P < 0.001), with the exact agreement rates (with broth microdilution) at 2 µg/mL being 53.6% in Vitek 2 and 86.7% in E-test. Overall, E-test (98.1%) had more categorical accordance than did Vitek 2 (94.0%; P = 0.026). Vitek 2 had a tendency to overestimate MRSA in high-MIC isolates, whereas E-test inclined underestimation in low-MIC isolates. Surprisingly, the discordance rates of MRSA vancomycin MICs were higher in hospital-acquired isolates (13.3%–17.0%) than in community-acquired isolates (6.2%–7.0%).

Conclusion

The Infectious Diseases Society of America recommends the use of alternative antimicrobial agents when vancomycin MIC is ≥ 2 µg/mL; in this study, only 53.6% of the isolates tested using Vitek 2 showed a high MIC in the broth microdilution method. Accurate identification of the resistance profile is a key component of antimicrobial stewardship programs. Therefore, to reduce inappropriate antibiotic use and mitigate the emergence of resistant strains, we recommend using complementary tests such as E-test or Broth microdilution to verify the MIC before administering second-line antibiotics.

Strengths

(1) We compared the categorical agreement between different methods measuring MRSA MICs level. (2) Physicians should incorporate this information and consider a complementary test to verify the appropriateness of the decision of shifting vancomycin to second-line antibiotic treatment to improve patients’ prognosis. (3) MRSA-vancomycin MICs at a cutoff of 2 µg/mL obtained using Vitek II exhibited a higher sensitivity level and negative predictive value than those obtained using E-test in the prediction of categorical agreement with standard broth microdilution.

Limitation

(1) Our research was based on a single hospital-based study. (2) The MRSA strains in this study were stored for more than 12 months after isolation. (3) We did not collect information on clinical prognosis.

Different formulations of vancomycin: In vitro antimicrobial activity against clinical isolates of methicillin-resistant Staphylococcus aureus

We compared in vitro antimicrobial activity of four vancomycin formulations used clinically against clinical isolates of Staphylococcus aureus, including methicillin-resistant and -susceptible (MRSA and MSSA, respectively), using different susceptibility assays. The minimal inhibitory concentrations (MICs) against MRSA clinical isolates were significantly different for some vancomycin formulations by the broth microdilution and agar dilution methods. However, these variations would not compromise their clinical use, since the MICs were within the range recommended by the Clinical and Laboratory Standards Institute. Furthermore, 26.9% of MRSA clinical isolates showed a vancomycin MIC ≥1.5 μg/mL according to the Etest® method but none by broth microdilution. Regarding quality, all formulations were in accordance with United States Pharmacopeia criteria. Our results showed that all vancomycin formulations tested showed similar in vitro antimicrobial activity, making them suitable for clinical use, and that the evaluation method chosen to determine sensitivity to this antimicrobial should be carefully performed, particularly for MRSA.

Morbidity from in-hospital complications is greater than treatment failure in patients with Staphylococcus aureus bacteraemia

BACKGROUND

Various studies have identified numerous factors associated with poor clinical outcomes in patients with Staphylococcus aureus bacteraemia (SAB). A new study was created to provide deeper insight into in-hospital complications and risk factors for treatment failure.

METHODS

Adult patients hospitalised with Staphylococcus aureus bacteraemia (SAB) were recruited prospectively into a multi-centre cohort. The primary outcome was treatment failure at 30 days (composite of all-cause mortality, persistent bacteraemia, or recurrent bacteraemia), and secondary measures included in-hospital complications and mortality at 6- and 12-months. Data were available for 222 patients recruited from February 2011 to December 2012.

RESULTS

Treatment failure at 30-days was recorded in 14.4% of patients (30-day mortality 9.5%). Multivariable analysis predictors of treatment failure included age > 70 years, Pitt bacteraemia score ≥ 2, CRP at onset of SAB > 250 mg/L, and persistent fevers after SAB onset; serum albumin at onset of SAB, receipt of appropriate empiric treatment, recent healthcare attendance, and performing echocardiography were protective. 6-month and 12-month mortality were 19.1% and 24.2% respectively. 45% experienced at least one in-hospital complication, including nephrotoxicity in 19.5%.

CONCLUSIONS

This study demonstrates significant improvements in 30-day outcomes in SAB in Australia. However, we have identified important areas to improve outcomes from SAB, particularly reducing renal dysfunction and in-hospital treatment-related complications.

Reproducible measurement of vancomycin MICs within the susceptible range in Staphylococcus aureus by a broth microdilution method with a "quasi-continuum" gradient of antibiotic concentrations

The availability of reproducible broth microdilution (BMD) methods including inter log₂ antibiotic dilutions for measuring Staphylococcus aureus (SA) vancomycin minimum inhibitory concentrations (MICs) within the susceptible range is needed to elucidate the impact of vancomycin MICs on clinical outcomes of invasive SA infections. Here, we report on the development of a very precise BMD method that incorporates the following incremental antibiotic concentrations: 0.50, 0.62, 0.75, 0.87, 1.0, 1.25, 1.40, 1.50, 1.60, 1.75, and 2.0 μg/mL. The intra- and inter-assay coefficients of variation of this method were around 20%. The mean of the differences in MIC values for all isolates obtained across two independent runs performed at one center was 0.04 μg/mL [95% confidence interval (CI), 0.011-0.07 μg/mL] and that for ten isolates measured at two different centers was 0.04 μg/mL (95% CI, 0-13 μg/mL). Vancomycin MIC values differed by less than 0.1 μg/mL between runs for most isolates. Storage of isolates at -20 °C for up to 3 months had no impact on the vancomycin MIC values. The mean vancomycin MIC values obtained by the Etest using a standard inoculum (0.5 McFarland) were significantly higher (p ≤ 0.001) than those measured by BMD and the MIC values measured by the two methods correlated poorly (Rho, 0.319; p = 0.148). Nevertheless, the mean MIC values measured by the Etest using lower inocula (10⁷ or 10⁶ CFU/mL) and those measured by BMD were comparable and correlated significantly (p = 0.004 for 10⁷ CFU/mL and p = 0.029 for 10⁶ CFU/mL).