New Gram-positive antibiotics: better than vancomycin?

Antibiotic treatment of acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

Acute bacterial skin and skin structure infections (ABSSSI) are a leading cause of morbidity, with a considerable variety of clinical presentation and a wide range of etiological pathogens. Of importance, the spread of multidrug-resistant (MDR) strains (i.e. methicillin-resistant Staphylococcus aureus or Gram-negative bacteria) is increasingly reported in some regions. in this review, we summarize the current clinical approach to patients with ABSSSI.

RECENT FINDINGS

Accurate diagnosis and identification of risk factors for MDR pathogens are key determinants for administering appropriate therapy in patients with ABSSSI. In daily clinical practice, this can be critical as there are many features defining the 'high risk patient' including both disease and host-associated risk factors.

SUMMARY

Antibiotic therapy should be based according to the different clinical spectrum of disease belonging to the ABSSSI, on the pathogens most likely to be involved and local resistance. Careful evaluation of antibiotic therapy after 48-72 h of initial therapy could help clinicians to early identify patients with treatment failure and to consider an alternative approach. Close monitoring of patients with multiple comorbidities, drug-drug interaction or adverse host factors are also necessary.

Methionine Limitation Impairs Pathogen Expansion and Biofilm Formation Capacity

Multidrug-resistant bacterial pathogens are becoming increasingly prevalent, and novel strategies to treat bacterial infections caused by these organisms are desperately needed. Bacterial central metabolism is crucial for catabolic processes and provides precursors for anabolic pathways, such as the biosynthesis of essential biomolecules like amino acids or vitamins. However, most essential pathways are not regarded as good targets for antibiotic therapy since their products might be acquired from the environment. This issue raises doubts about the essentiality of such targets during infection. A putative target in bacterial anabolism is the methionine biosynthesis pathway. In contrast to humans, almost all bacteria carry methionine biosynthesis pathways which have often been suggested as putative targets for novel anti-infectives. While the growth of methionine auxotrophic strains can be stimulated by exogenous methionine, the extracellular concentrations required by most bacterial species are unknown. Furthermore, several phenotypic characteristics of methionine auxotrophs are only partly reversed by exogenous methionine. We investigated methionine auxotrophic mutants of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli (all differing in methionine biosynthesis enzymes) and found that each needed concentrations of exogenous methionine far exceeding that reported for human serum (∼30 µM). Accordingly, these methionine auxotrophs showed a reduced ability to proliferate in human serum. Additionally, S. aureus and P. aeruginosa methionine auxotrophs were significantly impaired in their ability to form and maintain biofilms. Altogether, our data show intrinsic defects of methionine auxotrophs. This result suggests that the pathway should be considered for further studies validating the therapeutic potential of inhibitors.IMPORTANCE New antibiotics that attack novel targets are needed to circumvent widespread resistance to conventional drugs. Bacterial anabolic pathways, such as the enzymes for biosynthesis of the essential amino acid methionine, have been proposed as potential targets. However, the eligibility of enzymes in these pathways as drug targets is unclear because metabolites might be acquired from the environment to overcome inhibition. We investigated the nutritional needs of methionine auxotrophs of the pathogens Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli We found that each auxotrophic strain retained a growth disadvantage at methionine concentrations mimicking those available in vivo and showed that biofilm biomass was strongly influenced by endogenous methionine biosynthesis. Our experiments suggest that inhibition of the methionine biosynthesis pathway has deleterious effects even in the presence of external methionine. Therefore, additional efforts to validate the effects of methionine biosynthesis inhibitors in vivo are warranted.

Skin and soft tissue infections after breast surgery

PURPOSE OF REVIEW

Breast surgery is considered a clean surgical procedure; nevertheless, infection rates are often higher than those reported after other similarly considered clean surgeries (e.g., thyroid, hernia). Acute bacterial skin and soft tissue infections, mostly surgical site infections and implant-associated infections are commonest events that could complicate postoperative care.

RECENT FINDINGS

Risk of infection is closely related to surgery procedure itself and patients host factors. Gram-positive bacteria with pattern of antimicrobial resistance are increasingly isolated and before today less frequent causes such as gram negative and mycobacteria infections. Impact of postoperative complications is underestimated and lacking an appropriate care and education for local and systemic management.

SUMMARY

We report the current evidence on the management of infections after breast surgery. New drugs options for methicillin-resistant Staphylococcus aureus and other gram positive should have a place in this setting. Stewardship activities aiming at reducing infections risks with the correct considerations of host, microbiological and surgical risk factors.

Outpatient parenteral antimicrobial therapy and antibiotic stewardship: opponents or teammates?

PURPOSE

This narrative review aims to describe barriers of outpatient parenteral antimicrobial therapy at home (OPAT), potentially compromising general standards of antibiotic stewardship (ABS) and facilitators of OPAT for ABS.

METHODS

After a literature review, five authors determined the barriers and facilitators to discuss in this review.

RESULTS

Sixty-six publications were included in the narrative review and seven barriers and five facilitators are discussed in this article. The impracticability of multiple daily dosing during OPAT, the impact of real-life temperature variations, deviations of the infusion rates of elastomeric devices, access to prolonged intravenous antibiotic therapy, not administering loading doses before the initiation of extended or continuous infusions and the transmural nature of care associated with OPAT, can lead to deviations of recommended treatment regimens and sub-optimal clinical and laboratory follow-up, with a risk of inferior clinical outcomes, adverse events, drug-resistance and higher costs. On the other hand, OPAT provides access to treatments with intravenous antibiotics and simultaneously avoids prolonged hospitalization.

CONCLUSION

Implementing ABS guidelines in OPAT programs, e.g., by using a multidisciplinary team approach and facility-specific protocols for OPAT with patient selection criteria and instructions for selection, storage, preparation and administration of antibiotics, can improve appropriate antibiotic use. Additionally, further research should examine the effectiveness of these interventions on outcomes of OPAT.

Current and future trends in antibiotic therapy of acute bacterial skin and skin-structure infections

In 2013 the US Food and Drug Administration (FDA) issued recommendations and guidance on developing drugs for treatment of skin infection using a new definition of acute bacterial skin and skin-structure infection (ABSSSI). The new classification includes cellulitis, erysipelas, major skin abscesses and wound infection with a considerable extension of skin involvement, clearly referring to a severe subset of skin infections. The main goal of the FDA was to better identify specific infections where the advantages of a new antibiotic could be precisely estimated through quantifiable parameters, such as improvement of the lesion size and of systemic signs of infection. Before the spread and diffusion of methicillin-resistant Staphylococcus aureus (MRSA) in skin infections, antibiotic therapy was relatively straightforward. Using an empiric approach, a β-lactam was the preferred therapy and cultures from patients were rarely obtained. With the emergence of MRSA in the community setting, initial ABSSSI management has been changed and readdressed. Dalbavancin, oritavancin and tedizolid are new drugs, approved or in development for ABSSSI treatment, that also proved to be efficient against MRSA. Dalbavancin and oritavancin have a long half-life and can be dosed less frequently. This in turn makes it possible to treat patients with ABSSSI in an outpatient setting, avoiding hospitalization or potentially allowing earlier discharge, without compromising efficacy. In conclusion, characteristics of long-acting antibiotics could represent an opportunity for the management of ABSSSI and could profoundly modify the management of these infections by reducing or in some cases eliminating both costs and risks of hospitalization.

Comparative efficacy of telavancin and daptomycin in experimental endocarditis due to multi-clonotype MRSA strains

BACKGROUND

MRSA strains of clonal complexes (CCs) 5, 8, 30 and 45 are leading causes of complicated endovascular infections associated with suboptimal clinical outcomes. Telavancin is a novel anti-MRSA agent that both inhibits bacterial cell wall synthesis and disrupts membranes by depolarization.

METHODS

In this study, we compared the in vitro susceptibility and in vivo efficacy of telavancin versus daptomycin in an experimental rabbit infective endocarditis (IE) model caused by four MRSA strains representing each of the above CC types.

RESULTS

All study strains were susceptible to telavancin (MICs of ≤0.12 mg/L) and daptomycin (MICs of ≤0.5 mg/L). In vitro time-kill analyses revealed that supra-MIC levels of telavancin were effective at preventing regrowth at 24 h of incubation. In the IE animal model for all CC types, treatment with telavancin produced significantly greater reductions in MRSA counts as compared with daptomycin-treated animals in all target tissues. Moreover, telavancin-treated animals had a significantly higher percentage of sterile tissue cultures versus daptomycin-treated animals (e.g. 78%-100% versus 0% sterile vegetations and 100% versus 0%-11% sterile kidneys and spleen, in the telavancin- and daptomycin-treated animals, respectively).

CONCLUSIONS

These results suggest that telavancin exhibits significantly greater efficacies versus daptomycin in treating experimental IE caused by MRSA clinical isolates across four common CC types.

Daptomycin: an evidence-based review of its role in the treatment of Gram-positive infections

Infections caused by Gram-positive pathogens remain a major public health burden and are associated with high morbidity and mortality. Increasing rates of infection with Gram-positive bacteria and the emergence of resistance to commonly used antibiotics have led to the need for novel antibiotics. Daptomycin, a cyclic lipopeptide with rapid bactericidal activity against a wide range of Gram-positive bacteria including methicillin-resistant Staphylococcus aureus, has been shown to be effective and has a good safety profile for the approved indications of complicated skin and soft tissue infections (4 mg/kg/day), right-sided infective endocarditis caused by S. aureus, and bacteremia associated with complicated skin and soft tissue infections or right-sided infective endocarditis (6 mg/kg/day). Based on its pharmacokinetic profile and concentration-dependent bactericidal activity, high-dose (>6 mg/kg/day) daptomycin is considered an important treatment option in the management of various difficult-to-treat Gram-positive infections. Although daptomycin resistance has been documented, it remains uncommon despite the increasing use of daptomycin. To enhance activity and to minimize resistance, daptomycin in combination with other antibiotics has also been explored and found to be beneficial in certain severe infections. The availability of daptomycin via a 2-minute intravenous bolus facilitates its outpatient administration, providing an opportunity to reduce risk of health care-associated infections, improve patient satisfaction, and minimize health care costs. Daptomycin, not currently approved for use in the pediatric population, has been shown to be widely used for treating Gram-positive infections in children.

Spondylodiscitis by drug-multiresistant bacteria: a single-center experience of 25 cases

BACKGROUND CONTEXT

Although the incidence of pyogenic spinal infections is increasing, the ideal treatment of spondylodiscitis is still a controversially discussed issue. Furthermore, the proportion of multiresistant bacteria in spondylodiscitis is increasing, and treatment recommendations or reported results are missing for this especially difficult subset of patients.

PURPOSE

The aim of this study is to evaluate the surgical outcome and the postoperative antibacterial treatment regime.

STUDY DESIGN

Retrospective case series.

PATIENT SAMPLE

Patients treated for a spondylodiscitis from multiresistant bacteria at our department between 2006 and 2011.

METHODS

Data were gathered through review of patients' case notes, relevant imaging, and electronic records. Magnetic resonance imaging of the whole spine including gadolinium (Gd)-enhanced T1 sequences and computed tomography scans of the affected regions were obtained in all cases.

OUTCOME MEASURES

C-reactive protein (CRP) and complete blood cell count were analyzed in all cases using routine laboratory techniques. Neurologic deficits were classified according to the American Spinal Injury Association (ASIA) impairment scale.

RESULTS

Twenty-five patients were identified (15 gram-positive and 10 gram-negative drug-multiresistant bacteria). The mean age at presentation was 66 years, and 14 patients were male (56%). All patients presented with pain, and a neurologic deficit was present in 11 (44%) cases. An epidural abscess was found in 11 (44%) cases. At admission, CRP was elevated in all cases with a mean of 13±9.2 mg/dL. The main source of infection was previous spine surgery (36%). All patients in this series underwent surgical debridement of the infection and instrumentation of the spine. Postoperative intravenous antibiotics were administered for 19±8.6 days followed by 3±0.3 months of oral antibiotic therapy. Eradication of the infection was achieved ultimately in all surviving patients. Out of 11 patients with neurologic deficits, 4 had a full recovery, 4 improved incompletely, and 3 remained unchanged after surgery.

CONCLUSIONS

Staged surgical immobilization and instrumentation and optimal debridement at the interdiscal space and spinal canal is a reliable approach to achieve complete healing of spinal infection with multiresistant bacteria. A period of intravenous antibiotic therapy of 2 to 3 weeks followed by a 3-month oral antibiotic therapy seems appropriate for most cases.

antibacTR: dynamic antibacterial-drug-target ranking integrating comparative genomics, structural analysis and experimental annotation

BACKGROUND

Development of novel antibacterial drugs is both an urgent healthcare necessity and a partially neglected field. The last decades have seen a substantial decrease in the discovery of novel antibiotics, which combined with the recent thrive of multi-drug-resistant pathogens have generated a scenario of general concern. The procedures involved in the discovery and development of novel antibiotics are economically challenging, time consuming and lack any warranty of success. Furthermore, the return-on-investment for an antibacterial drug is usually marginal when compared to other therapeutics, which in part explains the decrease of private investment.

RESULTS

In this work we present antibacTR, a computational pipeline designed to aid researchers in the selection of potential drug targets, one of the initial steps in antibacterial-drug discovery. The approach was designed and implemented as part of two publicly funded initiatives aimed at discovering novel antibacterial targets, mechanisms and drugs for a priority list of Gram-negative pathogens: Acinetobacter baumannii, Escherichia coli, Helicobacter pylori, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. However, at present this list has been extended to cover a total of 74 fully sequenced Gram-negative pathogens. antibacTR is based on sequence comparisons and queries to multiple databases (e.g. gene essentiality, virulence factors) to rank proteins according to their potential as antibacterial targets. The dynamic ranking of potential drug targets can easily be executed, customized and accessed by the user through a web interface which also integrates computational analyses performed in-house and visualizable on-site. These include three-dimensional modeling of protein structures and prediction of active sites among other functionally relevant ligand-binding sites.

CONCLUSIONS

Given its versatility and ease-of-use at integrating both experimental annotation and computational analyses, antibacTR may effectively assist microbiologists, medicinal-chemists and other researchers working in the field of antibacterial drug-discovery. The public web-interface for antibacTR is available at 'http://bioinf.uab.cat/antibactr'.

The impact of initial antibiotic therapy (linezolid, vancomycin, daptomycin) on hospital length of stay for complicated skin and soft tissue infections

Background

Empiric therapy of inpatient skin and soft tissue infections (SSTIs) generally require methicillin resistant Staphylococcus aureus (MRSA) coverage. Limited data are available to directly compare the effect of initial antibiotic choice on treatment outcomes and length of stay (LOS).

Objective

To assess potential differences in length of hospital stay when inpatients with complex skin and soft tissue infections (SSTIs) were initially treated with either vancomycin, linezolid, or daptomycin.

Methods

A retrospective review of 219 patients diagnosed with inpatient SSTI who received linezolid, vancomycin, or daptomycin for >48 hours was performed. Data collected included demographics, comorbidities, microbiologic/laboratory data, additional management (surgical, non-study antibiotics), hospital LOS, treatment outcome and morbidity/mortality.

Results

The three groups evaluated were linezolid (n = 45), vancomycin (n = 90) daptomycin (n = 84). There was no difference between the three groups with respect to gender, age, comorbidities, leukocytosis, fever, antibiotics prior to admission, site of infection culture results and surgical intervention. One death was recorded, not associated with diagnosis of SSTI. No significant difference in LOS was found (P = 0.525) between the 3 groups. The mean LOS in entire cohort was 4.5 days (SD ± 2.5); thirty patients had prolonged LOS for non-SSTI reasons; reanalyzing the data without these 30 patients did not produce any difference in the mean LOS between the 3 groups. Switching vancomycin just prior to discharge to facilitate outpatient therapy was common but did not impact LOS.

Conclusions

No difference was detected in hospital length of stay with respect to the initial choice of antibiotic (linezolid, vancomycin, or daptomycin) for SSTI. The three antibiotic regimens were equally effective in treating SSTIs as judged by LOS, irrespective of age, gender, comorbidities or baseline severity of SSTI. Given the large standard deviation in LOS, this result should be confirmed by larger studies.

The giant protein Ebh is a determinant of Staphylococcus aureus cell size and complement resistance

Staphylococcus aureus USA300, the clonal type associated with epidemic community-acquired methicillin-resistant S. aureus (MRSA) infections, displays the giant protein Ebh on its surface. Mutations that disrupt the ebh reading frame increase the volume of staphylococcal cells and alter the cross wall, a membrane-enclosed peptidoglycan synthesis and assembly compartment. S. aureus ebh variants display increased sensitivity to oxacillin (methicillin) as well as susceptibility to complement-mediated killing. Mutations in ebh are associated with reduced survival of mutant staphylococci in blood and diminished virulence in mice. We propose that Ebh, following its secretion into the cross wall, contributes to the characteristic cell growth and envelope assembly pathways of S. aureus, thereby enabling complement resistance and the pathogenesis of staphylococcal infections.

Ceftaroline fosamil: a brief clinical review

Ceftaroline is a novel cephalosporin with a favorable tolerability profile and broad in vitro activity against many resistant Gram-positive and common Gram-negative organisms. Ceftaroline fosamil is the first cephalosporin to be approved by the United States Food and Drug Administration (FDA) for the treatment of adults with acute bacterial skin and soft tissue infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA). It is also approved by the FDA for the treatment of adults with community-acquired bacterial pneumonia, including cases caused by Streptococcus pneumoniae (with or without concurrent bacteremia), although there are no data at this time to support the use of ceftaroline fosamil for the treatment of pneumonia caused by MRSA. Ceftaroline fosamil is likewise approved by the European Commission for the treatment of adults with complicated skin and soft tissue infections or community-acquired pneumonia. This review summarizes the pharmacokinetic and microbiologic properties of ceftaroline, as well as the safety and efficacy data that led to its approval by the FDA in 2010 and the European Commission in 2012. Future directions to be addressed are also highlighted.

Growth and laboratory maintenance of Staphylococcus aureus

Staphylococcus aureus is a facultative anaerobic Gram-positive coccus and a member of the normal skin flora as well as the nasal passages of humans. S. aureus is also the etiological agent of suppurative abscesses, as first described by Sir Alexander Ogston in 1880. Ever since, studies on S. aureus have focused on the complex battery of virulence factors and regulators that allow for its swift transition between commensalism and pathogenic states and escape from host immune defenses. The success of this pathogen is further evidenced by its ability to acquire antibiotic resistance traits through mechanisms that often remain poorly understood.

Anti-MRSA drug use and antibiotic susceptibilities of MRSA at a university hospital in Japan from 2007 to 2011

The purpose of this study is to examine the use of anti-methicillin-resistant Staphylococcus aureus (MRSA) drugs, such as vancomycin (VCM), teicoplanin (TEIC), arbekasin (ABK) and linezolid (LZD), and the antibiotic susceptibilities of MRSAs in Kobe University Hospital. We investigated MRSA isolation and use of anti-MRSA drugs and susceptibilities of MRSA, using linear regression analysis, from 2007 to 2011, and checked for correlation between the use of these drug and the antibiotic susceptibilities of MRSA. The overall monthly isolation rates of MRSA decreased from a mean of 84.8% in 2007 to 70.0% in 2011 (r=0.946, P=0.015, b=-0.220), and the monthly isolation rate of MRSA in inpatients decreased from a mean of 78.6% in 2007 to 57.7% in 2011 (r=0.952, P=0.012, b=-0.160). From 2007 to 2011, VCM consumption significantly increased (r=0.916, P=0.029, b=0.055), whereas TEIC and LZD use remained stable during the study period. In addition, ABK use significantly decreased from 23.8 defined daily dose (DDD) per 1000 patient-days in 2007 to 5.2 DDD per 1000 in 2011 (r=0.902, P=0.036, b=-0.216). Susceptibility rates of MRSA were almost 100% to TEIC and VCM. The rates of MRSA to ABK and LZD significantly increased (r=0.959, P=0.010, b=2.137 for ABK and r=0.933, P=0.020, b=3.111 for LZD). In conclusion, our findings indicated a decreased MRSA isolation rate and the effective use of anti-MRSA drugs (VCM, TEIC, ABK and LZD), and improved susceptibility rates to anti-MRSA drugs, suggesting the possibilities that appropriate and early use of anti-MRSA drugs may cause the decrease of MRSA isolation.

Small molecule inhibitor of lipoteichoic acid synthesis is an antibiotic for Gram-positive bacteria

The current epidemic of infections caused by antibiotic-resistant gram-positive bacteria requires the discovery of new drug targets and the development of new therapeutics. Lipoteichoic acid (LTA), a cell wall polymer of gram-positive bacteria, consists of 1,3-polyglycerol-phosphate linked to glycolipid. LTA synthase (LtaS) polymerizes polyglycerol-phosphate from phosphatidylglycerol, a reaction that is essential for the growth of gram-positive bacteria. We screened small molecule libraries for compounds inhibiting growth of Staphylococcus aureus but not of gram-negative bacteria. Compound 1771 [2-oxo-2-(5-phenyl-1,3,4-oxadiazol-2-ylamino)ethyl 2-naphtho[2,1-b]furan-1-ylacetate] blocked phosphatidylglycerol binding to LtaS and inhibited LTA synthesis in S. aureus and in Escherichia coli expressing ltaS. Compound 1771 inhibited the growth of antibiotic-resistant gram-positive bacteria and prolonged the survival of mice with lethal S. aureus challenge, validating LtaS as a target for the development of antibiotics.

Nano-technology for targeted drug delivery to combat antibiotic resistance

Several microbes have evolved clinically significant resistance against almost every available antibiotic. Yet the development of new classes of antibiotics has lagged far behind our growing need. Frequent and suboptimal use of antibiotics particularly in developing countries aggravated the problem by increasing the rate of resistance. Therefore, developing new and multidimensional strategies to combat microbial infections is warranted. These include i) modification of existing antibiotics, ii) searching new and novel antibiotics, iii) development and improvement of antibiotics carrier system to reduce amount and frequency of antibiotic doses, iv) development of targeted antibiotic delivery systems. Here, the authors discuss trends and development of nano-materials and alternative antimicrobials to solve the problem of antibiotic resistance.