Bacteremia due to Methicillin-Resistant Staphylococcus aureus: New Therapeutic Approaches

Native Infective Endocarditis: A State-of-the-Art-Review

Native valve infective endocarditis (NVE) is a global phenomenon, defined by infection of a native heart valve and involving the endocardial surface. The causes and epidemiology of the disease have evolved in recent decades, with a doubling of the average patient age. A higher incidence was observed in patients with implanted cardiac devices that can result in right-sided infection of the tricuspid valve. The microbiology of the disease has also changed. Previously, staphylococci, which are most often associated with health-care contact and invasive procedures, were the most common cause of the disease. This has now been superseded by streptococci. While innovative diagnostic and therapeutic strategies have emerged, mortality rates have not improved and remain at 30%, which is higher than that for many cancer diagnoses. The lack of randomized trials and logistical constraints impede clinical management, and long-standing controversies such as the use of antibiotic prophylaxis persist. This state of the art review addresses clinical practice, controversies, and strategies to combat this potentially devastating disease. A multidisciplinary team will be established to provide care for patients with presumptive NVE. The composition of the team will include specialists in cardiology, cardiovascular surgery, and infectious disease. The prompt administration of combination antimicrobial therapy is essential for effective NVE treatment. Additionally, a meticulous evaluation of each patient is necessary in order to identify any indications for immediate valve surgery. With the intention of promoting a more comprehensive understanding of the procedural management of native infective endocarditis and to furnish clinicians with a reference, the current evidence for the utilization of distinct strategies for the diagnosis and treatment of NVE are presented.

The Bayesian-Based Area under the Curve of Vancomycin by Using a Single Trough Level: An Evaluation of Accuracy and Discordance at Tertiary Care Hospital in KSA

The AUC_0-24 is the most accurate way to track the vancomycin level while the C_min is not an accurate surrogate. Most hospitals in Saudi Arabia are under-practicing the AUC-guided vancomycin dosing and monitoring. No previous work has been conducted to evaluate such practice in the whole kingdom. The current study objective is to calculate the AUC_0-24 using the Bayesian dosing software (PrecisePK), identify the probability of patients who receive the optimum dose of vancomycin, and evaluate the accuracy and precision of the Bayesian platform. This retrospective study was conducted at King Abdulaziz medical city, Jeddah. All adult patients treated with vancomycin were included. Pediatric patients, critically ill patients requiring ICU admission, patients with acute renal failure or undergoing dialysis, and febrile neutropenic patients were excluded. The AUC_0-24 was predicted using the PrecisePK platform based on the Bayesian principle. The two-compartmental model by Rodvold et al. in this platform and patients' dose data were utilized to calculate the AUC_0-24 and trough level. Among 342 patients included in the present study, the mean of the estimated vancomycin AUC_0-24 by the posterior model of PrecisePK was 573 ± 199.6 mg, and the model had a bias of 16.8%, whereas the precision was 2.85 mg/L. The target AUC_0-24 (400 to 600 mg·h/L) and measured trough (10 to 20 mg/L) were documented in 127 (37.1%) and 185 (54%), respectively. Furthermore, the result demonstrated an increase in odds of AUC_0-24 > 600 mg·h/L among trough level 15-20 mg/L group (OR = 13.2, p < 0.05) as compared with trough level 10-14.9 mg/L group. In conclusion, the discordance in the AUC_0-24 ratio and measured trough concentration may jeopardize patient safety, and implantation of the Bayesian approach as a workable alternative to the traditional trough method should be considered.

Synthesis and Development of N-2,5-Dimethylphenylthioureido Acid Derivatives as Scaffolds for New Antimicrobial Candidates Targeting Multidrug-Resistant Gram-Positive Pathogens

The growing antimicrobial resistance to last-line antimicrobials among Gram-positive pathogens remains a major healthcare emergency worldwide. Therefore, the search for new small molecules targeting multidrug-resistant pathogens remains of great importance. In this paper, we report the synthesis and in vitro antimicrobial activity characterisation of novel thiazole derivatives using representative Gram-negative and Gram-positive strains, including tedizolid/linezolid-resistant S. aureus, as well as emerging fungal pathogens. The 4-substituted thiazoles 3h, and 3j with naphthoquinone-fused thiazole derivative 7 with excellent activity against methicillin and tedizolid/linezolid-resistant S. aureus. Moreover, compounds 3h, 3j and 7 showed favourable activity against vancomycin-resistant E. faecium. Compounds 9f and 14f showed broad-spectrum antifungal activity against drug-resistant Candida strains, while ester 8f showed good activity against Candida auris which was greater than fluconazole. Collectively, these data demonstrate that N-2,5-dimethylphenylthioureido acid derivatives could be further explored as novel scaffolds for the development of antimicrobial candidates targeting Gram-positive bacteria and drug-resistant pathogenic fungi.

Impact of a monthly antimicrobial stewardship quality assurance tool for elevated vancomycin levels

Objective:

We sought to determine the value of an audit-and-feedback monitoring method in facilitating meaningful practice changes to improve vancomycin dosing and monitoring.

Design:

Retrospective, multicenter, before-and-after implementation observational quality assurance initiative.

Setting:

The study was conducted in 7 not-for-profit, acute-care hospitals within a health system in southern Florida.

Methods:

The preimplementation period (September 1, 2019, through August 31, 2020) was compared to the postimplementation period (September 1, 2020, through May 31, 2022). All vancomycin serum-level results were screened for inclusion. The primary end point was the rate of fallout, defined as vancomycin serum level ≥25 µg/mL with acute kidney injury (AKI) and off-protocol dosing and monitoring. Secondary end points included the rate of fallout with respect to AKI severity, rate of vancomycin serum levels ≥25 µg/mL, and average number of serum-level evaluations per unique vancomycin patient.

Results:

In total, 27,611 vancomycin levels were analyzed from 13,910 unique patients. There were 2,209 vancomycin serum levels ≥25 µg/mL (8%) among 1,652 unique patients (11.9%). AKI was identified in 379 unique patients (23%) with a vancomycin levels ≥25 µg/mL. In total, 60 fallouts (35.2%) occurred in the 12-month preimplementation period (∼5 per month) and 41 fallouts (19.6%) occurred in the 21-month postimplementation period (∼2 per month; P = .0006). Failure was the most common AKI severity in both periods (risk: 35% vs 24.3%, P = .25; injury: 28.3% vs 19.5%, P = .30; failure: 36.7% vs 56%, P = .053). Overall, the number of evaluations of vancomycin serum levels per unique patient remained consistent throughout both periods (2 vs 2; P = .53).

Conclusions:

Implementation of a monthly quality assurance tool for elevated outlier vancomycin levels can improve dosing and monitoring practices resulting in enhanced patient safety.

Evaluation of the synergistic effect of ceftaroline against methicillin-resistant Staphylococcus aureus

OBJECTIVES

We aimed to determine the synergistic effects of ceftaroline (CPT) in combination with daptomycin (DAP), vancomycin (VAN), or linezolid (LNZ) against various methicillin-resistant Staphylococcus aureus (MRSA) strains.

METHODS

MRSA strains randomly selected from 2014 to 2018 were studied. Checkerboard titration and in vitro time-kill analyses were used to determine the synergistic activities of the antibiotic combinations.

RESULTS

A total of 10 genetically distinct MRSA strains were included in this study. The checkerboard titration analysis revealed that the CPT-DAP, CPT-VAN, and CPT-LNZ combinations had a synergistic effect against 30%, 10%, and 10% of the selected MRSA strains, respectively. Using time-kill analysis, we showed that CPT-DAP exhibited a significant synergistic and sustained bactericidal effect against both DAP-susceptible (Δ colony-forming units/ml, -5.79; P = 0.0495) and DAP-resistant (Δ colony-forming units/ml, -6.40; P = 0.0463) MRSA strains at a concentration of 0.5 × the minimum inhibitory concentration of CPT plus 0.5 × the minimum inhibitory concentration of DAP. No synergistic bactericidal effects were observed for the CPT-VAN and CPT-LNZ combinations against the selected strains.

CONCLUSION

The CPT-DAP combination showed better synergistic activity than the CPT-VAN and CPT-LNZ combinations against the enrolled MRSA strains. DAP, rather than VAN or LNZ, might be a better choice for CPT combination in the treatment of MRSA infections.

Dimer stilbene, a resveratrol analogue exhibits synergy with antibiotics that target protein synthesis in eradicating Staphylococcus aureus infection

Antibiotic resistance has become a major hurdle for successful treatment of several infections resulting in increased length of stay in hospitals and mortality. One of the notorious pathogens that wreaks havoc due to antibiotic resistance is Staphylococcus aureus. There is an urgent need to discover and understand the function of newer molecules that could serve in the arsenal to combat these bacteria. Our recent work identified important structural determinants of stilbenes that could aid in better antibacterial activity and identified Dimer stilbene (DS) as a potent inhibitor of S. aureus. Contrasting reports exist in literature about the combination of stilbenes with different antibiotics. In this study we evaluated the ability of DS to synergize with different classes of antibiotics. A screen revealed DS exhibited positive co-operativity with antibiotics that target protein synthesis. DS exhibited synergy with the aminoglycoside kanamycin and additive effect with tetracycline. Resistance generation to DS was null while to that of kanamycin was rapid. Kanamycin resistant S. aureus was equally susceptible to DS compared to wildtype. The efficacy of DS against clinical isolates susceptible and resistant to methicillin were similar. Laboratory generated kanamycin resistant strain and clinical strains were sensitized to kanamycin by pre-treatment with DS. DS cured S. aureus infection in mice as a standalone drug as well as in conjunction with kanamycin. Synergy with kanamycin was also observed in other stilbenes apart from DS. Thus our study reveals stilbenes could be exploited towards combating S. aureus infections either as standalone drugs or in combination with existing antibiotics.

Challenges in replicating secondary analysis of electronic health records data with multiple computable phenotypes: A case study on methicillin-resistant Staphylococcus aureus bacteremia infections

BACKGROUND

Replication of prediction modeling using electronic health records (EHR) is challenging because of the necessity to compute phenotypes including study cohort, outcomes, and covariates. However, some phenotypes may not be easily replicated across EHR data sources due to a variety of reasons such as the lack of gold standard definitions and documentation variations across systems, which may lead to measurement error and potential bias. Methicillin-resistant Staphylococcus aureus (MRSA) infections are responsible for high mortality worldwide. With limited treatment options for the infection, the ability to predict MRSA outcome is of interest. However, replicating these MRSA outcome prediction models using EHR data is problematic due to the lack of well-defined computable phenotypes for many of the predictors as well as study inclusion and outcome criteria.

OBJECTIVE

In this study, we aimed to evaluate a prediction model for 30-day mortality after MRSA bacteremia infection diagnosis with reduced vancomycin susceptibility (MRSA-RVS) considering multiple computable phenotypes using EHR data.

METHODS

We used EHR data from a large academic health center in the United States to replicate the original study conducted in Taiwan. We derived multiple computable phenotypes of risk factors and predictors used in the original study, reported stratified descriptive statistics, and assessed the performance of the prediction model.

RESULTS

In our replication study, it was possible to (re)compute most of the original variables. Nevertheless, for certain variables, their computable phenotypes can only be approximated by proxy with structured EHR data items, especially the composite clinical indices such as the Pitt bacteremia score. Even computable phenotype for the outcome variable was subject to variation on the basis of the admission/discharge windows. The replicated prediction model exhibited only a mild discriminatory ability.

CONCLUSION

Despite the rich information in EHR data, replication of prediction models involving complex predictors is still challenging, often due to the limited availability of validated computable phenotypes. On the other hand, it is often possible to derive proxy computable phenotypes that can be further validated and calibrated.

Competence Mining of Vancomycin (VAN) in the Management of Infections Due to Bacterial Strains With High VAN Minimum Inhibitory Concentrations (MICs): A Novel Dosing Strategy Based on Pharmacokinetic/Pharmacodynamic Modeling

The increasing emergence of bacterial strains with high VAN MICs (BS_H–VAN–M), such as Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus bovis, results in growing concern that VAN is not effective against these isolates. Due to the limited data on VAN against BS_H–VAN–M and the application limits of drugs currently considered to be effective for BS_H–VAN–M, exploration of “new usages for old drugs” is reasonable to improve and maximize the efficacy of existing antibiotics. This study aimed to construct a novel dosing strategy to mine the competence of VAN in the management of BS_H–VAN–M infections. Herein, we optimized the traditional intermittent i.v. infusion (TIII) method to create an optimal two-step infusion (OTSI). With pharmacokinetic (PK)/pharmacodynamic (PD) modeling at the targeted ratio of the daily area under the concentration-time curve (AUC_0–24) to the minimum inhibitory concentration (MIC) (AUC_0–24/MIC) of 400, we used Monte Carlo simulations to evaluate the efficacy of 25 VAN regimens (including 15 OTSI regimens and 10 TIII regimens with daily doses of up to 6 g) to treat pneumonia, meningitis, sternal osteomyelitis, mastitis, pleuritis, bacteremia, and bacterial pericarditis resulting from isolates with MICs of ≤64 mg/L and to the current E. faecalis, E. faecium, S. aureus, S. epidermidis, and S. bovis populations with a pooled MIC distribution. Our data indicated that 4 g/day VAN, with an OTSI but not a TIII, for mastitis, pleuritis, bacteremia, and bacterial pericarditis due to isolates with MICs of ≤4 mg/L or to the current E. faecalis, S. aureus, S. epidermidis, and S. bovis populations achieved the desired PK/PD exposure at the AUC_0–24/MIC target of 400. This study suggests the superiority and feasibility of OTSI relative to TIII for the competence mining of VAN against BS_H–VAN–M from the perspective of PK/PD and provides a new resource for understanding how PK/PD modeling shapes the performance of VAN to meet the growing challenges of BS_H–VAN–M infections.

Significantly Lower Infection Risk for Anterior Cruciate Ligament Grafts Presoaked in Vancomycin Compared With Unsoaked Grafts: A Systematic Review and Meta-analysis

PURPOSE

To compare postoperative infection rates following ACL reconstruction performed with grafts presoaked in vancomycin versus those without vancomycin.

METHODS

A systematic review was performed using PRISMA guidelines. PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials were searched for therapeutic level I to III studies that compared outcomes of presoaking ACL grafts with vancomycin versus without vancomycin in human patients. Included graft types were tendon autografts or allografts, and included studies documented infection with a minimum follow-up of 30 days. Postoperative infection rates and knee-specific patient-reported outcome scores were extracted from each study and compared between groups. Study methodological quality was analyzed using the Methodological Index for Non-Randomized Studies (MINORS) and Modified Coleman Methodology Score (MCMS). Infection rates and retear rates were pooled and weighted for meta-analysis using a random-effects model. All P values were reported with an α level of 0.05 set as significant.

RESULTS

The initial search yielded 144 articles (44 duplicates, 100 screened, 29 full-text review). Ten articles (21,368 subjects [7,507 vancomycin and 13,861 no vancomycin], 67% males, mean ± standard deviation age 29.5 ± 1.5 years) were included and analyzed. Eight of the 10 studies included only autografts, with 94.5% of grafts being hamstring autografts. Soaking grafts in vancomycin resulted in significantly fewer infections (0.013% versus 0.77%; odds ratio 0.07; 95% confidence interval 0.03, 0.18; P < .001). Only 2 studies included patient-reported outcomes, and both demonstrated no difference in International Knee Documentation Committee scores 1 year after surgery for patients with grafts presoaked in vancomycin versus without vancomycin.

CONCLUSIONS

Soaking ACL tendon grafts with vancomycin before implantation is associated with a nearly 15 times decrease in odds of infection compared with grafts not soaked in vancomycin. Few studies investigated patient-reported outcomes and retear rates after soaking ACL grafts in vancomycin.

LEVEL OF EVIDENCE

III, systematic review of level III studies.

Prevalence, predictors, and mortality of bloodstream infections due to methicillin-resistant Staphylococcus aureus in patients with malignancy: systemic review and meta-analysis

BACKGROUND

Cancer patients are more likely to develop and die of bloodstream infection (BSI) than noncancer patients. Methicillin-resistant Staphylococcus aureus (MRSA), which is associated with immense mortality and economic burden worldwide, is not covered by the recommended initial antibiotic therapy for cancer patients with BSI. This systemic review was performed to estimate the global methicillin-resistant Staphylococcus aureus (MRSA) prevalence among bacteremia in patients with malignancy, and further study the predictors and mortality of cancer patients with MRSA bacteremia.

METHODS

The PubMed and EMBASE databases were searched for studies published from Jan. 2000 to Mar. 2020 that provided primary data on the prevalence, predictors, or mortality of MRSA bacteremia in cancer patients. A random-effects model meta-analysis was performed to estimate the pooled prevalence of MRSA with 95% confidence intervals (95% CIs).

RESULTS

The pooled prevalence of MRSA was 3% (95% CI 2-5%) among all bloodstream infections (BSIs) and 44% (95% CI 32-57%) among S. aureus bacteremia in cancer patients. Based on geographical stratification, the pooled prevalence was 5% in Africa (95% CI 1-14%), 1% in Americas (95% CI 1-2%), 2% in Europe (95% CI 1-4%), 4% in Western Pacific (95% CI 2-7%), 8% in South-east Asia (95% CI 4-14%) and 0% in Eastern Mediterranean (95% CI 0-3%). No significant temporal change in MRSA rates was detected in this analysis (R2 = 0.06; P = 0.24). Predictors for MRSA BSIs among cancer patients were identified by comparison with their methicillin-susceptible counterparts, and they were mainly related to healthcare-associated infections and immunosuppression. Finally, the 60-day mortality in adult cancer patients with MRSA BSIs was reported to be 12%, and the 6-month overall mortality was 43.2%, with community-onset infection, secondary BSI, and vancomycin MIC≥2 g/mL being the risk factors for mortality.

CONCLUSIONS

Although the prevalence of MRSA BSIs among cancer patients is relatively low, it did not decline over time as MRSA BSIs in the general hospital population and the high mortality rate was related to MRSA BSIs in patients with malignancy.

The Expression of Efflux Pump Genes in Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Isolated from Blood Cultures in Iran

Background: Efflux pump is a significant resistance mechanism in Staphylococcus aureus. A total of 100 patients with bacteremia from Shahid Beheshti University Hospitals of Tehran in Iran were tested for the expression of efflux pump genes, contributing to S. aureus antimicrobial resistance. Objectives: This study was conducted to identify antibiotic resistance pattern, and to evaluate the inhibitory effect of efflux pump, MIC of ciprofloxacin, and expression levels of norA, norB, and norC efflux pump genes in the presence of an efflux pump inhibitor against MDR S. aureus. Methods: A total of 100 MRSA isolates were investigated in different hospitals of Shahid Beheshti University of Medical Sciences from April 2017 - 2018. Owing to new consensus guidelines from the Clinical and Laboratory Standards Institute (CLSI), both the Kirby-Bauer disk diffusion test and micro-dilution method were used to evaluate antimicrobial susceptibility. Efflux pump activity using carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was identified as a chemical efflux pump inhibitor. E-test was used to determine vancomycin-resistant antibiotic. Broth micro-dilution method for S. aureus isolates resistant to ciprofloxacin has been developed for minimum inhibitory concentration (MIC) of ciprofloxacin and CCCP and their composition. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to investigate the expression level of norA, norB, and norC efflux pump genes. Results: A total of 38 of 45 MRSA isolates (84.4%) showed resistance to ciprofloxacin. Moreover, 100% of isolates had the norA and norB genes. Further, 95% of S. aureus isolates had the norC gene. According to this study, ciprofloxacin MIC has decreased by CCCP compared to ciprofloxacin. There was an increase in the expression level of norA, norB, and norC efflux pump genes in methicillin-resistant and ciprofloxacin-resistant S. aureus strains based on RT- PCR. In this study, four different spA types were obtained as the most prevalent type of spA by t037and t790 (23.3%) and t030 (14.1%) and t044 (12.2%). Conclusions: This study indicates that the prevalence of ciprofloxacin-resistant S. aureus strains has a rising trend among MRSA clinical isolates. The ability of S. aureus isolates to be converted into drug-resistant strains using efflux pump mechanism has become a widespread concern.

The Evolving Reduction of Vancomycin and Daptomycin Susceptibility in MRSA-Salvaging the Gold Standards with Combination Therapy

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with substantial morbidity and mortality. Vancomycin (VAN) has been used as the gold standard treatment for invasive MRSA infections for decades but, unfortunately, the reliance of VAN as the primary treatment option against these infections has led to a reduction in VAN susceptibility in MRSA isolates. Although daptomycin (DAP) is another common treatment option against invasive MRSA infections, it has been shown that the development of VAN resistance can lead to DAP nonsusceptibility. VAN or DAP backbone regimens in combination with other antibiotics has been advocated as an alternative approach to improve patient outcomes in VAN/DAP-susceptible infections, enhance outcomes in infections caused by isolates with reduced VAN/DAP susceptibility, and/or prevent the emergence of VAN/DAP resistance or further resistance. A peer-reviewed literature search was conducted using Medline, Google Scholar and PubMed databases. The primary purpose of this review is to describe the mechanisms and epidemiology of MRSA isolates with a reduction in VAN and/or DAP susceptibility, evaluate in vitro and in vivo literature describing combination therapy (CT) against MRSA isolates with reduced VAN and/or DAP susceptibility and describe studies involving the clinical outcomes of patients treated with CT against invasive MRSA infections.

Patient Case Report Daptomycin Holiday-A Daptomycin Dosing Strategy for Asymptomatic Increases in Creatine Phosphokinase Levels

Daptomycin possesses excellent activity against many multidrug-resistant gram positive organisms. However, a side effect of concern with daptomycin is skeletal muscle injury, which is manifested in the form of elevated creatine phosphokinase (CPK). Management of such CPK elevations has traditionally been discontinuation of the offending agent, with many studies showing a resolution of a normal CPK level within 1 week of discontinuation and no long term adverse effects. Nevertheless, the question remains if daptomycin can be successfully restarted in such patients. Here, we present a case of a "daptomycin holiday" in which daptomycin was withheld upon CPK elevation and successfully reintroduced to the patient's regimen again after several days without further elevation of the CPK. The patient had a peak CPK of 2,557 U/L, and had no associated symptoms. A hypothesis for this holiday could be the adaptability of the skeletal muscle myocytes, in which the extra period between doses may allow for additional recovery of the membrane structure to further daptomycin exposure. Giving an asymptomatic patient with elevated CPK level, a short daptomycin holiday to allow for the CPK level to trend downward before resuming daptomycin therapy could be a potential strategy in patients for whom continuing daptomycin is still preferred.

Recent pattern of antibiotic resistance in Staphylococcus aureus clinical isolates in Eastern India and the emergence of reduced susceptibility to vancomycin

PURPOSE:

We aimed to determine the recent pattern of antibiotic resistance and assess the vancomycin susceptibility profile of clinical Staphylococcus aureus in view of emerging reports of vancomycin creep, reduced vancomycin susceptibility (RVS), including heterogeneous vancomycin-intermediate S. aureus (hVISA) and vancomycin-intermediate S. aureus, and vancomycin resistance in S. aureus isolates.

MATERIALS AND METHODS:

Consecutive, nonduplicate isolates of S. aureus between July 2015 and June 2016 were subjected to antimicrobial susceptibility testing using standard disk diffusion test or Etest as per the Clinical and Laboratory Standards Institute 2015. Detection of hVISA was done by glycopeptide resistance detection Etest according to the manufacturer's instructions in strains with vancomycin minimum inhibitory concentration of 1–2 μg/ml.

RESULTS:

A total of 284 S. aureus were obtained from pus (175, 61.6%), respiratory tract (31, 10.9%), urine (27, 9.5%), blood (25, 8.8%), body fluids (18, 6.3%), and catheter tips (8, 2.8%). 127 (44.7%) isolates were methicillin resistant, and 158 (55.6%) were multidrug resistant. High resistance was observed to penicillin (81.7%), erythromycin (62.3%), and ciprofloxacin (52.1%), whereas the resistance was low to gentamicin (5.3%), rifampicin (8.1%), and doxycycline (9.5%). Two hundred and fifty-one (88.3%) isolates were fully susceptible to vancomycin, whereas 33 (11.6%) demonstrated RVS. All were uniformly susceptible to linezolid, tigecycline, and daptomycin.

CONCLUSIONS:

A moderately high percentage of S. aureus isolates demonstrated RVS, which may limit its usefulness in methicillin-resistant isolates and may be associated with increased complications in methicillin-susceptible infections. In view of increasing glycopeptide resistance, the susceptibility status of vancomycin along with other antibiotics among clinical S. aureus isolates should be investigated periodically.

Is there still a role for vancomycin in skin and soft-tissue infections?

PURPOSE OF REVIEW

Skin and soft-tissue infections (SSIs) are among the commonest infections encountered in clinical practice. Spread of methicillin-resistant Staphylococcus aureus SSIs continues to increase in both health care and community settings and presents a challenge for the best treatment choice. Vancomycin has been the mainstay of SSIs treatment, but recently its use has been questioned because of concerns about its efficacy, tolerability, and unfavorable pharmacokinetic/pharmacodynamic profile. The purpose of this review is to establish the current role for vancomycin in light of the literature published from January 2007 to September 2017 on comparison with both old and new alternatives.

RECENT FINDINGS

Meta-analyses show better clinical and microbiological outcomes for drugs approved for the treatment of SSI, including those sustained by methicillin-resistant S. aureus, in the last 10 years than for vancomycin. The newer glycopeptides and linezolid decrease the total treatment costs compared with vancomycin, by reducing the length of stay or avoiding the hospitalization.

SUMMARY

Vancomycin is noninferior in efficacy and safety to all comparator drugs, including the newest on the market. However, the SSI treatment evidence base presents several shortcomings limiting the clinical applicability of the results. High-level clinical trials should be performed to obtain results that can be generalized and applied effectively in clinical practice.

Cervicofacial Infections Caused by Staphylococcus aureus

Staphylococcus aureus (S. aureus) is an opportunistic pathogen that causes a wide range of diseases. Dissemination of perioral infections is a common problem in the field of oral and maxillofacial surgery. The aim of the study was to evaluate S. aureus carriage in the oral cavity and its dissemination to different cervicofacial regions. Clinical case 1 is a patient with a systemic history of type I diabetes which led to foot amputation one year previou sly, who presented alteration of ocular motility and the culture showed Grampositive cocci compatible with S. aureus. The patient was discharged after eight days of antibiotic therapy and drainage. Clinical case 2 was a young female without any comorbidities who had never been hospitalized before or even exposed to the hospital environment. The presence of lesions compatible with necrotizing fasciitis (NF) in the lower lip mucosal region, rapid evolution of the infection to deep planes, and evolution of the clinical picture alerted health-care providers to the need for prompt care. Clinical case 3 was an immunosuppressed patient with cellulitis which is a bacterial infection of the skin and soft tissues that occurs when the physical barrier of the skin and soft tissues, the immune system, and/or the circulatory system are affected. S. aureus is an opportunistic pathogen which causes a wide range of diseases. It inhabits the oral cavity, from where it can spread to distant cervicofacial regions. This is why it is important for health-care professionals to be aware of this niche in case of dissemination in order to provide prompt diagnosis and appropriate treatment.

Treatments and limitations for methicillin-resistant Staphylococcus aureus: A review of current literature

Methicillin-resistant Staphylococcus aureus (MRSA) has remained a major threat to healthcare; in both hospital and community settings over the past five decades. With the current use of antibiotics for a variety of infections, including MRSA, emerging resistance is a major concern. Currently available treatments have restrictions limiting their use. These issues include, but are not limited to, side effects, cross-resistance, lack of understanding of pharmacokinetics and clinical pharmacodynamics, gradual increment in minimal inhibitory concentration over the period (MIC creep) and ineffectiveness in dealing with bacterial biofilms. Despite availability of various therapeutic options for MRSA, the clinical cure rates remain low with high morbidity and mortality. Given these challenges with existing treatments, there is a need for development of novel agents for MRSA. Along with prompt infection control strategies and strict implementation of antibiotic stewardship, cautious use of newer anti-MRSA agents will be of utmost importance. This article reviews the treatments and limitations of MRSA management and highlights the future path.

Clinical Data on Daptomycin plus Ceftaroline versus Standard of Care Monotherapy in the Treatment of Methicillin-Resistant Staphylococcus aureus Bacteremia

Vancomycin (VAN) and daptomycin (DAP) are approved as a monotherapy for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. A regimen of daptomycin plus ceftaroline (DAP+CPT) has shown promise in published case series of MRSA salvage therapy, but no comparative data exist to compare up-front DAP+CPT head-to-head therapy versus standard monotherapy as an initial treatment. In a pilot study, we evaluated 40 adult patients who were randomized to receive 6 to 8 mg/kg of body weight per day of DAP and 600 mg intravenous (i.v.) CPT every 8 h (q8h) (n = 17) or standard monotherapy (n = 23) with vancomycin (VAN; dosed to achieve serum trough concentrations of 15 to 20 mg/liter; n = 21) or 6 to 8 mg/kg/day DAP (n = 2). Serum drawn on the first day of bacteremia was sent to a reference laboratory post hoc for measurement of interleukin-10 (IL-10) concentrations and correlation to in-hospital mortality. Sources of bacteremia, median Pitt bacteremia scores, Charlson comorbidity indices, and median IL-10 serum concentrations were similar in both groups. Although the study was initially designed to examine bacteremia duration, we observed an unanticipated in-hospital mortality difference of 0% (0/17) for combination therapy and 26% (6/23) for monotherapy (P = 0.029), causing us to halt the study. Among patients with an IL-10 concentration of >5 pg/ml, 0% (0/14) died in the DAP+CPT group versus 26% (5/19) in the monotherapy group (P = 0.057). Here, we share the full results of this preliminary (but aborted) assessment of early DAP+CPT therapy versus standard monotherapy in MRSA bacteremia, hoping to encourage a more definitive clinical trial of its potential benefits against this leading cause of infection-associated mortality. (The clinical study discussed in this paper has been registered at ClinicalTrials.gov under identifier NCT02660346.).

Morbidity, mortality, and management of methicillin-resistant S. aureus bacteremia in the USA: update on antibacterial choices and understanding

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is associated with significant healthcare costs, morbidity, and mortality in the United States. Complications of MRSA bacteremia include infective endocarditis, osteomyelitis, and sepsis, all of which are difficult to treat. Time to effective therapy and antibacterial choice greatly affect patient outcomes. Vancomycin and daptomycin remain first-line therapies; however, reports of vancomycin-associated treatment failure and reduced daptomycin susceptibility highlight the need to define alternative strategies for MRSA bacteremia treatment. In addition, several patient- and pathogen-specific factors influence the outcomes of MRSA bacteremia. It is, therefore, critical to explore the interaction between host- and pathogen-specific factors and its effect on MRSA bacteremia pathogenesis and mortality. This review discusses the factors that drive the development of MRSA bacteremia and examines alternative treatment strategies.

Multicenter Evaluation of the Accelerate PhenoTest BC Kit for Rapid Identification and Phenotypic Antimicrobial Susceptibility Testing Using Morphokinetic Cellular Analysis

We describe results from a multicenter study evaluating the Accelerate Pheno system, a first of its kind diagnostic system that rapidly identifies common bloodstream pathogens from positive blood cultures within 90 min and determines bacterial phenotypic antimicrobial susceptibility testing (AST) results within ∼7 h. A combination of fresh clinical and seeded blood cultures were tested, and results from the Accelerate Pheno system were compared to Vitek 2 results for identification (ID) and broth microdilution or disk diffusion for AST. The Accelerate Pheno system accurately identified 14 common bacterial pathogens and two Candida spp. with sensitivities ranging from 94.6 to 100%. Of fresh positive blood cultures, 89% received a monomicrobial call with a positive predictive value of 97.3%. Six common Gram-positive cocci were evaluated for ID. Five were tested against eight antibiotics, two resistance phenotypes (methicillin-resistant Staphylococcus aureus and Staphylococcus spp. [MRSA/MRS]), and inducible clindamycin resistance (MLSb). From the 4,142 AST results, the overall essential agreement (EA) and categorical agreement (CA) were 97.6% and 97.9%, respectively. Overall very major error (VME), major error (ME), and minor error (mE) rates were 1.0%, 0.7%, and 1.3%, respectively. Eight species of Gram-negative rods were evaluated against 15 antibiotics. From the 6,331 AST results, overall EA and CA were 95.4% and 94.3%, respectively. Overall VME, ME, and mE rates were 0.5%, 0.9%, and 4.8%, respectively. The Accelerate Pheno system has the unique ability to identify and provide phenotypic MIC and categorical AST results in a few hours directly from positive blood culture bottles and support accurate antimicrobial adjustment.

Incidence, prevalence, and management of MRSA bacteremia across patient populations-a review of recent developments in MRSA management and treatment

Methicillin-resistant Staphylococcus aureus (MRSA) infection is still a major global healthcare problem. Of concern is S. aureus bacteremia, which exhibits high rates of morbidity and mortality and can cause metastatic or complicated infections such as infective endocarditis or sepsis. MRSA is responsible for most global S. aureus bacteremia cases, and compared with methicillin-sensitive S. aureus, MRSA infection is associated with poorer clinical outcomes. S. aureus virulence is affected by the unique combination of toxin and immune-modulatory gene products, which may differ by geographic location and healthcare- or community-associated acquisition. Management of S. aureus bacteremia involves timely identification of the infecting strain and source of infection, proper choice of antibiotic treatment, and robust prevention strategies. Resistance and nonsusceptibility to first-line antimicrobials combined with a lack of equally effective alternatives complicates MRSA bacteremia treatment. This review describes trends in epidemiology and factors that influence the incidence of MRSA bacteremia. Current and developing diagnostic tools, treatments, and prevention strategies are also discussed.

The Whole Price of Vancomycin: Toxicities, Troughs, and Time

Vancomycin is a glycopeptide antibiotic that is active against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus. Nephrotoxicity, which is usually reversible, is the most serious common adverse effect of vancomycin. Vancomycin-associated nephrotoxicity prolongs hospital stays, imposes a need for additional antibiotics and, in rare circumstances, dialysis treatment, and increases medical costs and mortality. Risk factors for nephrotoxicity include the dose and duration of vancomycin treatment, serum trough concentration, patient characteristics, and concomitant receipt of nephrotoxins. Contemporary guidelines recommend targeting vancomycin trough concentrations of ≥10 mg/L to prevent resistance and trough concentrations of 15-20 mg/L to optimize outcomes. There is significant correlation between vancomycin trough serum concentrations and the incidence of vancomycin-associated nephrotoxicity; however, evidence of an association between trough concentrations and efficacy is less convincing. Routine monitoring of serum vancomycin concentrations consumes time and limited healthcare resources and may not be cost effective. The use of alternative antibacterial agents that do not require monitoring would free up pharmacy resources. This time could then be devoted to initiatives such as pharmacist-led antibiotic stewardship programs that are known to reduce antibiotic use and promote improved patient outcomes.

Septic Thrombophlebitis with Persistent Methicillin-Resistant Staphylococcus Aureus Bacteremia and de Novo Resistance to Vancomycin and Daptomycin

Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is associated with significant risk of mortality, especially when it occurs while on appropriate antimicrobial therapy. We herein describe an unusual case of a patient with prosthetic aortic tissue valve, who suffered from central venous catheter related MRSA bacteremia with septic thrombus formation in the superior vena cava. MRSA bacteremia persisted despite removal of the catheter and appropriate antimicrobial therapy including vancomycin, rifampin, and daptomycin. Subsequently, the MRSA strain exhibited de novo resistance to vancomycin, rifampin and daptomycin. Eventually, salvage combination therapy with high dose daptomycin and trimethoprim-sulfamethoxazole was successful and achieved clearance of MRSA bacteremia. The case illustrates the growing complexity of treating MRSA infections.

Pharmacokinetic drug evaluation of ceftobiprole for the treatment of MRSA

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA), while decreasing in overall incidence, is still a prominent concern world-wide. New agents coming to market in the last 10 years allow practitioners to optimize treatment for MRSA infections. Ceftobiprole is a cephalosporin agent with MRSA activity, currently approved in selected countries for the treatment of community-acquired pneumonia and hospital-acquired pneumonia. Areas covered: Relevant literature regarding spectrum of activity, pharmacokinetics, pharmacodynamics, and clinical trials will be discussed. Expert opinion: Ceftobiprole is an addition to a growing number of antimicrobials with activity against MRSA. Concern for appropriate dosing in critically ill patients remains due to its ineffectiveness for the treatment of ventilator-associated pneumonia (VAP). While ceftobiprole has activity against gram-negative organisms, the allowance for use of an additional agent for gram-negative infections in clinical trials limits recommendations for monotherapy for empirical treatment of HAP. Ceftobiprole's place in therapy will lie in its activity against gram positive organisms, such as Streptococcus spp. and Staphylococcus spp.

Treatment of Staphylococcus aureus Infections

Staphylococcus aureus, although generally identified as a commensal, is also a common cause of human bacterial infections, including of the skin and other soft tissues, bones, bloodstream, and respiratory tract. The history of S. aureus treatment is marked by the development of resistance to each new class of antistaphylococcal antimicrobial drugs, including the penicillins, sulfonamides, tetracyclines, glycopeptides, and others, complicating therapy. S. aureus isolates identified in the 1960s were sometimes resistant to methicillin, a ß-lactam antimicrobial active initially against a majority S. aureus strains. These MRSA isolates, resistant to nearly all ß-lactam antimicrobials, were first largely confined to the health care environment and the patients who attended it. However, in the mid-1990s, new strains, known as community-associated (CA-) MRSA strains, emerged. CA-MRSA organisms, compared with health care-associated (HA-) MRSA strain types, are more often susceptible to multiple classes of non ß-lactam antimicrobials. While infections caused by methicillin-susceptible S. aureus (MSSA) strains are usually treated with drugs in the ß-lactam class, such as cephalosporins, oxacillin or nafcillin, MRSA infections are treated with drugs in other antimicrobial classes. The glycopeptide drug vancomycin, and in some countries teicoplanin, is the most common drug used to treat severe MRSA infections. There are now other classes of antimicrobials available to treat staphylococcal infections, including several that have been approved after 2009. The antimicrobial management of invasive and noninvasive S. aureus infections in the ambulatory and in-patient settings is the topic of this review. Also discussed are common adverse effects of antistaphylococcal antimicrobial agents, advantages of one agent over another for specific clinical syndromes, and the use of adjunctive therapies such as surgery and intravenous immunoglobulin. We have detailed considerations in the therapy of noninvasive and invasive S. aureus infections. This is followed by sections on specific clinical infectious syndromes including skin and soft tissue infections, bacteremia, endocarditis and intravascular infections, pneumonia, osteomyelitis and vertebral discitis, epidural abscess, septic arthritis, pyomyositis, mastitis, necrotizing fasciitis, orbital infections, endophthalmitis, parotitis, staphylococcal toxinoses, urogenital infections, and central nervous system infections.

In vitro ceftaroline combinations against meticillin-resistant Staphylococcus aureus

We studied in vitro ceftaroline combinations against 61 meticillin-resistant Staphylococcus aureus isolates; 18 of them were also resistant to linezolid, using overlapping E-test method. Daptomycin-ceftaroline combination obtained lower fractional inhibitory concentration values, in comparison with those including vancomycin or linezolid against meticillin-resistant S. aureus (P<0.05). All meticillin- and linezolid-resistant S. aureus strains were resistant to ceftaroline; nevertheless, combinations with vancomycin or daptomycin showed higher synergy or addition rates than those with linezolid.

Infective endocarditis

Infective endocarditis (IE) is a rare, life-threatening disease that has long-lasting effects even among patients who survive and are cured. IE disproportionately affects those with underlying structural heart disease and is increasingly associated with health care contact, particularly in patients who have intravascular prosthetic material. In the setting of bacteraemia with a pathogenic organism, an infected vegetation may form as the end result of complex interactions between invading microorganisms and the host immune system. Once established, IE can involve almost any organ system in the body. The diagnosis of IE may be difficult to establish and a strategy that combines clinical, microbiological and echocardiography results has been codified in the modified Duke criteria. In cases of blood culture-negative IE, the diagnosis may be especially challenging, and novel microbiological and imaging techniques have been developed to establish its presence. Once diagnosed, IE is best managed by a multidisciplinary team with expertise in infectious diseases, cardiology and cardiac surgery. Antibiotic prophylaxis for the prevention of IE remains controversial. Efforts to develop a vaccine that targets common bacterial causes of IE are ongoing, but have not yet yielded a commercially available product.