Ceftaroline in complicated skin and skin-structure infections

Molecular docking and proteomics reveals the synergistic antibacterial mechanism of theaflavin with β-lactam antibiotics against MRSA

Recurrent epidemics of methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) have illustrated that the effectiveness of antibiotics in clinical application is rapidly fading. A feasible approach is to combine natural products with existing antibiotics to achieve an antibacterial effect. In this molecular docking study, we found that theaflavin (TF) preferentially binds the allosteric site of penicillin-binding protein 2a (PBP2a), inducing the PBP2a active site to open, which is convenient for β-lactam antibiotics to treat MRSA infection, instead of directly exerting antibacterial activity at the active site. Subsequent TMT-labeled proteomics analysis showed that TF treatment did not significantly change the landscape of the S. aureus USA300 proteome. Checkerboard dilution tests and kill curve assays were performed to validate the synergistic effect of TF and ceftiofur, and the fractional inhibitory concentration index (FICI) was 0.1875. The antibacterial effect of TF combined with ceftiofur was better than that of single-drug treatment in vitro. In addition, TF effectively enhanced the activity of ceftiofur in a mouse model of MRSA-induced pneumonia. Our findings provide a potential therapeutic strategy to combine existing antibiotics with natural products to resolve the prevalent infections of multidrug-resistant pathogens.

Penicillin binding protein 2a: An overview and a medicinal chemistry perspective

Antimicrobial resistance is an imminent threat worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the "superbug" family, manifesting resistance through the production of a penicillin binding protein, PBP2a, an enzyme that provides its transpeptidase activity to allow cell wall biosynthesis. PBP2a's low affinity to most β-lactams, confers resistance to MRSA against numerous members of this class of antibiotics. An Achilles' heel of MRSA, PBP2a represents a substantial target to design novel antibiotics to tackle MRSA threat via inhibition of the bacterial cell wall biosynthesis. In this review we bring into focus the PBP2a enzyme and examine the various aspects related to its role in conferring resistance to MRSA strains. Moreover, we discuss several antibiotics and antimicrobial agents designed to target PBP2a and their therapeutic potential to meet such a grave threat. In conclusion, we consider future perspectives for targeting MRSA infections.

Advances in the local and targeted delivery of anti-infective agents for management of osteomyelitis

INTRODUCTION

Osteomyelitis, a common and debilitating invasive infection of bone, is a frequent complication following orthopedic surgery and causes pathologic destruction of skeletal tissues. Bone destruction during osteomyelitis results in necrotic tissue, which is poorly penetrated by antibiotics and can serve as a nidus for relapsing infection. Osteomyelitis therefore frequently necessitates surgical debridement procedures, which provide a unique opportunity for targeted delivery of antimicrobial and adjunctive therapies. Areas covered: Following surgical debridement, tissue voids require implanted materials to facilitate the healing process. Antibiotic-loaded, non-biodegradable implants have been the standard of care. However, a new generation of biodegradable, osteoconductive materials are being developed. Additionally, in the face of widespread antimicrobial resistance, alternative therapies to traditional antibiotic regimens are being investigated, including bone targeting compounds, antimicrobial surface modifications of orthopedic implants, and anti-virulence strategies. Expert commentary: Recent advances in biodegradable drug delivery scaffolds make this technology an attractive alternative to traditional techniques for orthopedic infection that require secondary operations for removal. Advances in novel treatment methods are expanding the arsenal of viable antimicrobial treatment strategies in the face of widespread drug resistance. Despite a need for large scale clinical investigations, these strategies offer hope for future treatment of this difficult invasive disease.

The large scale antibacterial, antifungal and anti-phage efficiency of Petamcin-A: new multicomponent preparation for skin diseases treatment

BACKGROUND

Human and animal skin diseases of bacterial, fungal and viral nature and their complications are widespread and globally cause a serious trouble. Their prevalence is increasing mainly due to drug resistance. Consequently, demand has increased for new effective antimicrobial drugs, which also should be less toxic, possess a wider spectrum of action and be economically more beneficial. The goal was to investigate antibacterial, antifungal and anti-phage activity of Petamcin-A-a new multicomponent preparation. It contains acetic acid and hexamethylenetetramine as main active antimicrobial components, as well as phosphatidylcholine, tocopheryl acetate and glycerol as excipients.

METHODS

Bacteriostatic activity and minimal inhibitory concentrations of the preparation against various test-organisms were determined by agar well diffusion assay. Antifungal activity was tested by agar dilution assay. To explore anti-phage activity double agar overlay plaque assay was used. Nystatin, chlorhexidine and acetic acid were used as control agents for comparative analysis. Statistical analysis was done with GraphPad Prism 5.03 or R 3.1.0 software.

RESULTS

The results showed a higher activity of Petamcin-A against all bacterial and fungal test strains compared with its components or control agents. The preparation was more effective against tested gram-positive bacteria than gram-negative ones. Petamcin-A expressed bactericidal activity against almost all test strains. In addition, the preparation demonstrated high activity against T4 phage of Escherichia coli C-T4 completely inhibiting its growth. 5-fold diluted Petamcin-A also exhibited considerable activity reducing phage concentration by 2.6 Log10.

CONCLUSIONS

Petamcin-A has a high antimicrobial activity against all tested strains of bacteria, yeasts and moulds. The preparation also exhibited high anti-phage activity. Moreover, taking into account that Petamcin-A has no observable toxicity on skin and its components are not expensive, it can be advantageous for management of various skin medical conditions.

Ceftaroline in the management of complicated skin and soft tissue infections and community acquired pneumonia

Ceftaroline is a new parenteral cephalosporin approved by the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) for the treatment of complicated skin and soft tissue infections (cSSTIs) including those due to methicillin-resistant Staphylococcus aureus (MRSA), and community-acquired pneumonia (CAP). Ceftaroline has broad-spectrum activity against gram-positive and gram-negative bacteria and exerts its bactericidal effects by binding to penicillin-binding proteins (PBPs), resulting in inhibition of bacterial cell wall synthesis. It binds to PBP 2a of MRSA with high affinity and also binds to all six PBPs in Streptococcus pneumoniae. In in vitro studies, ceftaroline demonstrated potent activity against Staphylococcus aureus (including MRSA and vancomycin-intermediate isolates), Streptococcus pneumoniae (including multidrug resistant isolates), Haemophilus influenzae, Moraxella catarrhalis, and many common gram-negative pathogens, excluding extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and Pseudomonas aeruginosa. In Phase II and Phase III clinical trials, ceftaroline was noninferior to its comparator agents and demonstrated high clinical cure rates in the treatment of cSSTIs and CAP. It demonstrated favorable outcomes in patients treated for both regulatory-approved indications and unlicensed indications in a retrospective analysis. Ceftaroline is a safe and effective option for treatment in specific patient populations in which its efficacy and safety have been proven. This article reviews the challenges in the treatment of cSSTI and CAP, ceftaroline and its microbiology, pharmacology, efficacy, and safety data which support its use in treatment of cSSTIs and CAP.

Disruption of allosteric response as an unprecedented mechanism of resistance to antibiotics

Ceftaroline, a recently approved β-lactam antibiotic for treatment of infections by methicillin-resistant Staphylococcus aureus (MRSA), is able to inhibit penicillin-binding protein 2a (PBP2a) by triggering an allosteric conformational change that leads to the opening of the active site. The opened active site is now vulnerable to inhibition by a second molecule of ceftaroline, an event that impairs cell-wall biosynthesis and leads to bacterial death. The triggering of the allosteric effect takes place by binding of the first antibiotic molecule 60 Å away from the active site of PBP2a within the core of the allosteric site. We document, by kinetic studies and by determination of three X-ray structures of the mutant variants of PBP2a that result in resistance to ceftaroline, that the effect of these clinical mutants is the disruption of the allosteric trigger in this important protein in MRSA. This is an unprecedented mechanism for antibiotic resistance.

Penicillin-binding protein 2a of methicillin-resistant Staphylococcus aureus

High-level resistance to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus (MRSA) is due to expression of penicillin-binding protein 2a (PBP2a), a transpeptidase that catalyzes cell-wall crosslinking in the face of the challenge by β-lactam antibiotics. The activity of this protein is regulated by allostery at a site 60 Å distant from the active site, where crosslinking of cell wall takes place. This review discusses the state of knowledge on this important enzyme of cell-wall biosynthesis in MRSA.