Antimicrobial activity of ceftaroline and comparator agents tested against bacterial isolates causing skin and soft tissue infections and community-acquired respiratory tract infections isolated from the Asia-Pacific region and South Africa (2010)

Ceftolozane/Tazobactam Activity Against Drug-Resistant Pseudomonas aeruginosa and Enterobacterales Causing Healthcare-Associated Infections in Eight Asian Countries: Report from an Antimicrobial Surveillance Program (2016-2018)

PURPOSE

To evaluate the in vitro activity of ceftolozane/tazobactam and comparator agents tested against Pseudomonas aeruginosa and Enterobacterales isolates from hospitalised patients in Asia. Ceftolozane/tazobactam is an antipseudomonal cephalosporin combined with a well-established β-lactamase inhibitor.

METHODS

A total of 2038 Gram-negative organisms (376 P. aeruginosa and 1662 Enterobacterales) were collected consecutively using a prevalence-based approach from 11 medical centres. Organisms were susceptibility tested by broth microdilution according to CLSI guidelines. CLSI and EUCAST breakpoint criteria were used.

RESULTS

Ceftolozane/tazobactam was the most potent (MIC50/90, 0.5/4 mg/L) β-lactam agent tested against P. aeruginosa isolates, inhibiting 91.0% of the isolates at an MIC of ≤4 mg/L. P. aeruginosa exhibited high rates of susceptibility to amikacin (92.0/92.0% [CLSI/EUCAST]) and colistin by EUCAST criteria only (99.2% intermediate [CLSI]/99.2% susceptible [EUCAST]). Ceftolozane/tazobactam (MIC50/90, 0.25/16 mg/L; 86.8/86.8% susceptible [CLSI/EUCAST]) and meropenem (MIC50/90, 0.03/0.12 mg/L; 93.0/93.3% susceptible [CLSI/EUCAST]) were the most active compounds tested against Enterobacterales. Isolates displayed susceptibility rates to other β-lactam agents, ranging from 81.5/77.7% for piperacillin/tazobactam, 66.0/64.5% for cefepime, and 65.3/60.9% for ceftazidime using CLSI/EUCAST breakpoints. Among the Enterobacterales isolates, 6.8% were carbapenem-resistant Enterobacterales (CRE) and 29.6% exhibited an extended-spectrum β-lactamase (ESBL) non-CRE phenotype. Ceftolozane/tazobactam showed good activity against ESBL non-CRE phenotype strains of Enterobacterales (MIC50/90, 0.5/8 mg/L; 84.8/84.8% susceptible), but not against isolates with a CRE phenotype (MIC50/90, >32/>32 mg/L).

CONCLUSION

Ceftolozane/tazobactam was the most active β-lactam agent tested against P. aeruginosa and demonstrated higher in vitro activity than the available cephalosporins when tested against Enterobacterales from Asian countries.

Evaluation of in vitro activity of ceftaroline on methicillin resistant Staphylococcus aureus blood isolates from Iran

Background and Objectives:

Ceftaroline (CPT) is a novel cephalosporin with potent activity against methicillin-resistant Staphylococcus aureus (MRSA). Despite its recent introduction, CPT resistance in MRSA has been described worldwide. We aimed in the current study to evaluate the in vitro activity of CPT against 91 clinical MRSA and 3 MSSA isolates.

Materials and Methods:

Susceptibility of isolates to CPT was tested using E-test and disk diffusion (DD) method. The nucleotide sequence of the mecA gene and molecular types of isolates with reduced susceptibility to CPT were further studied to identify resistance conferring mutations in PBP2a and the genetic relatedness of the isolates respectively.

Results:

Overall, 92.5% of isolates were found to be CPT susceptible (MICs≤1mg/l) and 7 MRSA isolates were characterized with MIC=2mg/l and categorized as susceptible dose dependent. Compared to E-test, DD revealed a categorical agreement rate of 93.6% and the obtained rates for minor, major /very major error were found to be 6.3% and 0% respectively. The MRSA isolates with increased CPT MICs (n=7), belonged to spa types t030 (n=6) and t13927 (n=1) and all carried N146K substitution in PBP2a allosteric domain, except for one isolate which harbored a wild-type PBP2a.

Conclusion:

While resistance to CPT was not detected we found increased CPT MICs in 7.69% of MRSA isolates. Reduced susceptibility to CPT in the absence of mecA mutations is indicative of contribution of secondary chromosomal mutations in resistance development.

An overview of antimicrobial resistance surveillance among healthcare-associated pathogens in South Africa

Healthcare-associated infections are a serious public health concern resulting in morbidity and mortality particularly in developing countries. The lack of information from Africa, the increasing rates of antimicrobial resistance and the emergence of new resistance mechanisms intensifies this concern warranting the need for vigorous standardised surveillance platforms that produce reliable and accurate data which can be used for addressing these concerns. The implementation of national treatment guidelines, policies, antimicrobial stewardship programmes and infection prevention and control practices within healthcare institutions require a platform from which it can draw information and direct its approach. In this review, the importance of standardised surveillance systems, the challenges faced in the application of a surveillance system and the condition (existence and nonexistence) of such systems in African countries is discussed. This review also reports on some South African data.

Management of complicated skin and soft tissue infections with a special focus on the role of newer antibiotics

Complicated skin and soft tissue infections (cSSTIs) represent the severe form of infectious disease that involves deeper soft tissues. Involvement of methicillin-resistant Staphylococcus aureus (MRSA) further complicates cSSTI with increased hospitalization, health care costs, and overall mortality. Various international guidelines provide recommendations on the management of cSSTIs, with the inclusion of newer antibiotics. This literature-based review discusses the overall management of cSSTI, including appropriate use of antibiotics in clinical practice. Successful treatment of cSSTIs starts with early and precise diagnosis, including identification of causative pathogen and its load, determination of infection severity, associated complications, and risk factors. The current standard-of-care for cSSTIs involves incision, drainage, surgical debridement, broad-spectrum antibiotic therapy, and supportive care. In recent years, the emergence of newer antibiotics (eg, ceftaroline, tigecycline, daptomycin, linezolid, etc) has provided clinicians wider options of antimicrobial therapy. Selection of antibiotics should be based on the drug characteristics, effectiveness, safety, and treatment costs, alongside other aspects such as host factors and local multidrug resistance rates. However, larger studies on newer antibiotics are warranted to refine the decision making on the appropriate antimicrobial therapy. Local Antimicrobial Stewardship Program strategies in health care settings could guide clinicians for early initiation of specific treatments to combat region-specific antimicrobial resistance, minimize adverse effects, and to improve outcomes such as reduction in Clostridium difficile infections. These strategies involving iv-to-oral switch, de-escalation to narrow-spectrum antibiotics, and dose optimization have an impact on the overall improvement of cSSTI therapy outcomes, especially in countries like Singapore that has a high disease burden.

Antimicrobial activity of ceftaroline against methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 2013-2014 at the Geneva University Hospitals

Ceftaroline is a broad-spectrum antibiotic with activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. Ceftaroline susceptibility of an MRSA set archived between 1994 and 2003 in the Geneva University Hospitals detected a high percentage (66 %) of ceftaroline resistance in clonotypes ST228 and ST247 and correlated with mutations in PBP2a. The ceftaroline mechanism of action is based on the inhibition of PBP2a; thus, the identification of PBP2a mutations of recently circulating clonotypes in our institution was investigated. We analyzed ceftaroline susceptibility in MRSA isolates (2013 and 2014) and established that resistant strains correlated with PBP2a mutations and specific clonotypes. Ninety-six MRSA strains were analyzed from independent patients and were isolated from blood cultures (23 %), deep infections (38.5 %), and superficial (skin or wound) infections (38.5 %). This sample showed a ceftaroline minimum inhibitory concentration (MIC) range between 0.25 and 2 μg/ml and disk diameters ranging from 10 to 30 mm, with a majority of strains showing diameters ≥20 mm. Based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, 76 % (73/96) of isolates showed susceptibility to ceftaroline. Nevertheless, we still observed 24 % (23/96) of resistant isolates (MIC = 2 μg/ml). All resistant isolates were assigned to clonotype ST228 and carried the N146K mutation in PBP2a. Only two ST228 isolates showed ceftaroline susceptibility. The decreasing percentage of ceftaroline-resistant isolates in our hospital can be explained by the decline of ST228 clonotype circulating in our hospital since 2008. We present evidence that ceftaroline is active against recent MRSA strains from our hospital; however, the presence of PBP2a variants in particular clonotypes may affect ceftaroline efficacy.

In vitro activity of Ceftaroline against bacterial pathogens isolated from patients with skin and soft tissue and respiratory tract infections in African and Middle Eastern countries: AWARE global surveillance program 2012-2014

The objective of this report was to document antimicrobial susceptibility testing surveillance data for ceftaroline and comparative agents from the AWARE (Assessing Worldwide Antimicrobial Resistance Evaluation) global surveillance program for bacterial pathogens causing skin and soft tissue and respiratory tract infections in African and Middle Eastern countries from 2012 through 2014. Pathogen identities were confirmed by MALDI-TOF and antimicrobial susceptibility testing performed by CLSI broth microdilution methodology in a central laboratory. All methicillin-susceptible Staphylococcus aureus (MSSA) (n= 923; MIC90, 0.25 μg/mL) and 91.8% of methicillin-resistant S. aureus (MRSA) (n= 1161; MIC90, 1 μg/mL) tested were susceptible to ceftaroline. The maximum ceftaroline MIC observed for isolates of MRSA was 2 μg/mL. All Streptococcus pyogenes (n= 174; MIC90, 0.008 μg/mL), Streptococcus agalactiae (n= 44; MIC90, 0.015 μg/mL), Streptococcus pneumoniae (n= 351; MIC90, 0.25 μg/mL), and Haemophilus influenzae (n= 84; MIC90, ≤0.015 μg/mL) were susceptible to ceftaroline. Rates of susceptibility to ceftaroline among ESBL-negative Escherichia coli (n= 338), Klebsiella pneumoniae (n= 241), and Klebsiella oxytoca (n= 97) were 89.1% (MIC90, 1 μg/mL), 94.2% (MIC90, 0.5 μg/mL), and 99.0% (MIC90, 0.5 μg/mL), respectively.

Ceftaroline fosamil versus ceftriaxone for the treatment of community-acquired pneumonia: individual patient data meta-analysis of randomized controlled trials

BACKGROUND

We conducted a meta-analysis of clinical trials of adults hospitalized with pneumonia outcomes research team (PORT) risk class 3-4 community-acquired pneumonia (CAP) receiving ceftaroline fosamil versus ceftriaxone.

METHODS

Three Phase III trials (clinicaltrials.gov registration numbers NCT00621504, NCT00509106 and NCT01371838) including 1916 hospitalized patients with CAP randomized 1:1 to empirical ceftaroline fosamil (600 mg every 12 h) or ceftriaxone (1-2 g every 24 h) for 5-7 days were included in the meta-analysis. Primary outcome was clinical response at the test-of-cure visit (8-15 days after end of treatment) in the PORT risk class 3-4 modified ITT (MITT) and clinically evaluable (CE) populations. Data were tested for heterogeneity (χ(2) test) and, if not significant, results were pooled and OR and 95% CI constructed. A logistic regression analysis assessed factors impacting cure rate and treatment interactions.

RESULTS

Clinical cure rates in each trial consistently favoured ceftaroline fosamil versus ceftriaxone, with no evidence of heterogeneity. In the meta-analysis, ceftaroline fosamil was superior to ceftriaxone in the MITT (OR: 1.66; 95% CI 1.34, 2.06; P < 0.001) and CE (OR: 1.65; 95% CI 1.26, 2.16; P < 0.001) populations. Results were consistent across various patient- and disease-related factors including patients' age and PORT score. Prior antimicrobial use within 96 h of starting study treatment was associated with diminished differences in cure rates between treatments.

CONCLUSIONS

Ceftaroline fosamil was superior to ceftriaxone for empirical treatment of adults hospitalized with CAP. Receipt of prior antimicrobial therapy appeared to diminish the observed treatment effect.

In Vitro Activity of Ceftaroline against Staphylococcus aureus Isolated in 2012 from Asia-Pacific Countries as Part of the AWARE Surveillance Program

Ceftaroline, the active metabolite of the prodrug ceftaroline-fosamil, is an advanced-generation cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA). This investigation provides in vitro susceptibility data for ceftaroline against 1,971 S. aureus isolates collected in 2012 from seven countries (26 centers) in the Asia-Pacific region as part of the Assessing Worldwide Antimicrobial Resistance and Evaluation (AWARE) program. Broth microdilution as recommended by the CLSI was used to determine susceptibility. In all, 62% of the isolates studied were MRSA, and the ceftaroline MIC90 for all S. aureus isolates was 2 μg/ml (interpretive criteria: susceptible, ≤1 μg/ml). The overall ceftaroline susceptibility rate for S. aureus was 86.9%, with 100% of methicillin-sensitive S. aureus isolates and 78.8% of MRSA isolates susceptible to this agent. The highest percentages of ceftaroline-nonsusceptible MRSA isolates came from China (47.6%), all of which showed intermediate susceptibility, and Thailand (37.1%), where over half (52.8%) of isolates were resistant to ceftaroline (MIC, 4 μg/ml). Thirty-eight ceftaroline-nonsusceptible isolates (MIC values of 2 to 4 μg/ml) were selected for molecular characterization. Among the isolates analyzed, sequence type 5 (ST-5) was the most common sequence type encountered; however, all isolates analyzed from Thailand were ST-228. Penicillin-binding protein 2a (PBP2a) substitution patterns varied by country, but all isolates from Thailand had the Glu239Lys substitution, and 12 of these also carried an additional Glu447Lys substitution. Ceftaroline-fosamil is a useful addition to the antimicrobial agents that can be used to treat S. aureus infections. However, with the capability of this species to develop resistance to new agents, it is important to recognize and monitor regional differences in trends as they emerge.

Susceptibility testing challenges with ceftaroline, MRSA and a 1 mg/L breakpoint

OBJECTIVES

A 1 mg/L susceptibility breakpoint for ceftaroline and staphylococci is universally agreed; EUCAST counts MIC >1 mg/L as resistant whereas CLSI and FDA count 2 mg/L as intermediate and >2 mg/L as resistant. We investigated whether routine diagnostic tests reliably distinguish MICs of 1 versus 2 mg/L.

METHODS

Thirty-five UK laboratories collected Staphylococcus aureus isolates and performed tests with 5 μg (as EUCAST) or 30 μg (as CLSI) discs and either confluent growth on Mueller-Hinton agar (as EUCAST and CLSI) or semi-confluent growth on Iso-Sensitest agar (as BSAC). They also ran Etests for MRSA. Reference MICs were determined centrally by CLSI and BSAC agar dilution.

RESULTS

We obtained paired local disc and central MIC results for 1607 S. aureus (33% MRSA). EUCAST's zone breakpoint recognized 56% of isolates found resistant in MIC tests, but the positive predictive value (PPV) for resistance was 11.0%; corresponding proportions by CLSI testing were 28.0% and 13.4%. The BSAC disc method detected 25% of resistant isolates, with a PPV of 18.2%. Essential agreement, ±1 dilution, of local Etests and central agar MICs was >95%, but only 20% of the isolates found non-susceptible by agar dilution were found non-susceptible by Etest and vice versa. Review for isolates with the modal MIC (0.25 mg/L) indicated that the same laboratories reported large or small zones irrespective of disc and method, implying systematic bias.

CONCLUSIONS

MRSA with ceftaroline MICs of 1 and 2 mg/L were poorly discriminated by routine methods. Solutions lie in greater standardization, automation or dosages justifying a higher breakpoint.

Reduced In Vitro Activity of Ceftaroline by Etest among Clonal Complex 239 Methicillin-Resistant Staphylococcus aureus Clinical Strains from Australia

A total of 421 methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates were tested for ceftaroline susceptibility by Etest (bioMérieux). A multidrug resistant phenotype was found in 40.9%, and clonal complex 239 (CC239) was found in 33.5%. Ceftaroline nonsusceptibility (MIC, >1.0 μg/ml) was 16.9% overall. Nonsusceptibility was significantly higher in CC239 (41.1%, 58/141) and in isolates with a multidrug resistant phenotype (35.5%, 61/172) compared with comparators (P < 0.0001). Nonsusceptibility of common multidrug resistant MRSA clones limits the empirical use of ceftaroline for these infections.

Antibiotic Tissue Penetration in Diabetic Foot Infections A Review of the Microdialysis Literature and Needs for Future Research

Although many antimicrobial agents display good in vitro activity against the pathogens frequently implicated in diabetic foot infections, effective treatment can be complicated by reduced tissue penetration in this population secondary to peripheral arterial disease and emerging antimicrobial resistance, which can result in clinical failure. Improved characterization of antibiotic tissue pharmacokinetics and penetration ratios in diabetic foot infections is needed. Microdialysis offers advantages over the skin blister and tissue homogenate studies historically used to define antibiotic penetration in skin and soft-tissue infections by defining antibiotic penetration into the interstitial fluid over the entire concentration versus time profile. However, only a select number of agents currently recommended for treating diabetic foot infections have been evaluated using these methods, which are described herein. Better characterization of the tissue penetration of antibiotic agents is needed for the development of methods for maximizing the pharmacodynamic profile of these agents to ultimately improve treatment outcomes for patients with diabetic foot infections.

Molecular characterization of MRSA isolates bracketing the current EUCAST ceftaroline-susceptible breakpoint for Staphylococcus aureus: the role of PBP2a in the activity of ceftaroline

OBJECTIVES

The objectives of this study were to characterize contemporary MRSA isolates and understand the prevalence and impact of sequence variability in PBP2a on ceftaroline susceptibility.

METHODS

A total of 184 MRSA isolates collected from 28 countries were collected and characterized.

RESULTS

WT PBP2a proteins were found in MRSA distributed evenly over the ceftaroline MIC range of 0.5-2 mg/L (n=56). PBP2a variations found in 124 isolates fell into two categories: (i) 12 isolates contained a substitution in the transpeptidase pocket located in the penicillin-binding domain and exhibited significantly decreased ceftaroline susceptibility (typically 8 mg/L); and (ii) isolates with substitutions in the non-penicillin-binding domain (nPBD) in a region proposed to be functionally important for cell wall biogenesis. The majority (71%) of isolates containing only nPBD variations were inhibited by 2 mg/L ceftaroline, 23% by ≤1 mg/L and 6% by 4 mg/L. These data suggest that the WT MRSA distribution extends beyond the current EUCAST and CLSI susceptible breakpoints and includes isolates inhibited by 2 mg/L ceftaroline. SCCmec type IV was the predominant type in the ceftaroline-susceptible population (68%), whereas it only represented 6% of the non-susceptible population. The variations of MLST lineages were fewer among the non-susceptible group.

CONCLUSIONS

This study suggests that MRSA populations with a WT PBP2a and those with nPBD variations overlap significantly and that PBP2a sequence-independent factors contribute to ceftaroline susceptibility. Whereas characterization of isolates with a ceftaroline MIC of 2 mg/L enriched for isolates with nPBD variations, it was not a discrete population. In contrast, the rare isolates containing a substitution in the transpeptidase-binding pocket were readily differentiated.

Salicylanilide carbamates: Promising antibacterial agents with high in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA)

A series of twenty-one salicylanilide N-alkylcarbamates was assessed for novel antibacterial characteristics against three clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus ATCC 29213 as the reference and quality control strain. The minimum inhibitory concentration was determined by the broth dilution micro-method with subsequent subcultivation of aliquots to assess minimum bactericidal concentration. The bactericidal kinetics was established by time-kill assay. Ampicillin, ciprofloxacin and vancomycin were used as reference antibacterial drugs. All the tested compounds exhibited highly potent anti-MRSA activity (⩽ 0.008-4 μg/mL) comparable or up to 250× higher than that of vancomycin, the standard in the treatment of serious MRSA infections. 4-Chloro-2-(3,4-dichlorophenylcarbamoyl)phenyl butylcarbamate and 4-chloro-2-(3,4-dichlorophenylcarbamoyl)phenyl ethylcarbamate were the most active compounds. In most cases, compounds provided reliable bacteriostatic activity, except for 4-chloro-2-(4-chlorophenylcarbamoyl)phenyl decylcarbamate exhibiting bactericidal effect at 8h (for clinical isolate of MRSA 63718) and at 24h (for clinical isolates of MRSA SA 630 and MRSA SA 3202) at 4× MIC. Structure-activity relationships are discussed.

Pre-Use Susceptibility to Ceftaroline in Clinical Staphylococcus aureus Isolates from Germany: Is There a Non-Susceptible Pool to be Selected?

Ceftaroline is a new cephalosporin active against Methicillin-resistant Staphylococcus aureus (MRSA). Based on a representative collection of clinical S. aureus isolates from Germany, supplemented with isolates of clonal lineages ST228 and ST239, we demonstrate the in-vitro susceptibility towards ceftaroline prior to its introduction into clinical use for a total of 219 isolates. Susceptibility testing was performed by broth microdilution, disc diffusion and Etest, respectively. Results were interpreted according to EUCAST guidelines and showed considerable variance in dependence on clonal affiliation of the isolates tested. Among isolates of widespread hospital-associated lineages we found a high proportion of clinical isolates with MICs close to the EUCAST breakpoint (MIC50/90 1.0/1.5 mg/L); currently, interpretation of these "borderline" MICs is complicated by a lack of concordant susceptibility testing methods and reasonable breakpoint determination. Isolates of clonal lineages ST228 and ST239 demonstrated increased MIC50/90 values of 2.5/3.33 mg/L. Sequencing of mecA revealed no association of resistance to a specific mecA polymorphism, but rather reveals two regions in the non-penicillin-binding domain of PbP2a which displayed different combinations of mutations putatively involved in resistance development. This study provides national baseline data to (i) adjust susceptibility testing methods and current breakpoints to clinical and epidemiological requirements, (ii) evaluate current breakpoints with respect to therapeutic outcome and (iii) monitor further resistance evolution.

Missense mutations in PBP2A Affecting ceftaroline susceptibility detected in epidemic hospital-acquired methicillin-resistant Staphylococcus aureus clonotypes ST228 and ST247 in Western Switzerland archived since 1998

The development and maintenance of an arsenal of antibiotics is a major health care challenge. Ceftaroline is a new cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA); however, no reports concerning MRSA ceftaroline susceptibility have been reported in Switzerland. We tested the in vitro activity of ceftaroline against an archived set of 60 MRSA strains from the University Hospital of Geneva collected from 1994 to 2003. Our results surprisingly revealed ceftaroline-resistant strains (MIC, >1 μg/ml in 40/60 strains; EUCAST breakpoints, susceptible [S], ≤1 μg/ml; resistant [R], >1 μg/ml) were present from 1998 to 2003. The detected resistant strains predominantly belonged to sequence type 228 (ST228) (South German clonotype) but also to ST247 (Iberian clonotype). A sequence analysis of these strains revealed missense mutations in the penicillin-binding protein 2A (PBP2A) allosteric domain (N146K or E239K and N146K-E150K-G246E). The majority of our ST228 PBP2A mutations (N146K or E150K) were distinct from ST228 PBP2A allosteric domain mutations (primarily E239K) recently described for MRSA strains collected in Thailand and Spain during the 2010 Assessing Worldwide Antimicrobial Resistance Evaluation (AWARE) global surveillance program. We also found that similar allosteric domain PBP2A mutations (N146K) correlated with ceftaroline resistance in an independent external ST228 MRSA set obtained from the nearby University Hospital of Lausanne, Lausanne, Switzerland, collected from 2003 to 2008. Thus, ceftaroline resistance was observed in our archived strains (including two examples of an MIC of 4 µg/ml for the Iberian ST247 clonotype with the triple mutation N146K/E150K/G246E), at least as far back as 1998, considerably predating the commercial introduction of ceftaroline. Our results reinforce the notion that unknown parameters can potentially exert selective pressure on PBP2A that can subsequently modulate ceftaroline resistance.

A multicentre study of meticillin-resistant Staphylococcus aureus in acute bacterial skin and skin-structure infections in China: susceptibility to ceftaroline and molecular epidemiology

Ceftaroline is a novel cephalosporin with activity against Gram-positive organisms, including meticillin-resistant Staphylococcus aureus (MRSA). The objective of this study was to investigate the susceptibility to ceftaroline of hospital-associated MRSA (HA-MRSA) isolates causing acute bacterial skin and skin-structure infections (ABSSSIs) in China and to examine their relationship by genotyping. A total of 251 HA-MRSA isolates causing ABSSSIs were collected from a multicentre study involving 56 hospitals in 38 large cities across 26 provinces in mainland China. All isolates were characterised by multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, spa typing and detection of the Panton-Valentine leukocidin locus (lukS-PV and lukF-PV). Minimum inhibitory concentrations (MICs) of 14 antimicrobial agents, including ceftaroline, were determined by broth microdilution and were interpreted using Clinical and Laboratory Standards Institute breakpoints. The ceftaroline MIC50 and MIC90 values (MICs that inhibit 50% and 90% of the isolates, respectively) were 1 μg/mL and 2 μg/mL, respectively; 33.5% (n=84) of the isolates studied were ceftaroline-non-susceptible, with MICs of 2 μg/mL, but no isolate exhibited ceftaroline resistance (MIC>2 μg/mL). All of the ceftaroline-non-susceptible isolates belonged to the predominant HA-MRSA clones: 95.2% (n=80) from MLST clonal complex 8 (CC8), with the remaining 4.8% (n=4) from CC5. The high rate of non-susceptibility to ceftaroline amongst HA-MRSA causing ABSSSIs in China is concerning.

Ceftaroline: clinical and microbiology experience with focus on methicillin-resistant Staphylococcus aureus after regulatory approval in the USA

Ceftaroline fosamil was approved in 2010 by the United States Food and Drug Administration (USA-FDA) for the treatment of patients with acute bacterial skin and skin structure infections (ABSSSIs) and community-acquired bacterial pneumonia (CABP). After approval, several studies and case reports have described the postmarketing clinical experience with ceftaroline in ABSSSIs and CABP and in patients with invasive methicillin-resistant Staphylococcus aureus (MRSA) infections, many of whom had failed prior antibiotics. Successful clinical outcomes observed among the majority of these patients were supported by preapproval and postapproval in vitro surveillance of ceftaroline activity using breakpoint criteria that have been harmonized between the USA-FDA and CLSI. MIC90 values/percentage of strains susceptible to ceftaroline has remained stable over the period 2009-2012. Taken together, these postapproval studies support the use of ceftaroline for ABSSSI as well as CABP. Importantly, these data also suggest that ceftaroline can be effective in patients with serious invasive MRSA infections who have failed other therapies.

Ceftaroline activity against bacterial organisms isolated from acute bacterial skin and skin structure infections in United States medical centers (2009-2011)

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a new cephalosporin with bactericidal activity against resistant Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant strains of Streptococcus pneumoniae, and commonly isolated Gram-negative organisms, including ceftriaxone-susceptible Enterobacteriaceae. We evaluated the in vitro activity of ceftaroline and selected comparator agents against bacterial isolates collected from patients with acute bacterial skin and skin structure infections (ABSSSIs) in the USA. A total of 6222 isolates were collected from 67 medical centers distributed across all nine USA census regions between 2009 and 2011 and tested for susceptibility by reference broth microdilution methods. Ceftaroline was very active against S. aureus (MIC50/90, 0.5/1 μg/mL; 99.6% susceptible), including MRSA (MIC50/90, 0.5/1 μg/mL; 99.1% susceptible). Against β-hemolytic streptococci, the activity of ceftaroline (MIC50/90, ≤0.015/0.03 μg/mL; 100.0% susceptible) was comparable to that of both penicillin (MIC50/90, ≤0.06/≤0.06 μg/mL; 100.0% susceptible) and ceftriaxone (MIC50/90, ≤0.25/≤0.25 μg/mL; 100.0% susceptible). Ceftaroline was also highly active against viridans group streptococci (MIC50/90, 0.03/0.06 μg/mL). Similar to ceftriaxone and ceftazidime, ceftaroline was active against wild-type strains of Escherichia coli (MIC50/90, 0.12/0.25 μg/mL; 94.0% susceptible) and Klebsiella pneumoniae (MIC50/90, 0.12/0.25 μg/mL; 96.8% susceptible); however, the ceftaroline activity was compromised among strains with an extended-spectrum β-lactamase-phenotype (MIC50/90, >32/>32 μg/mL for both E. coli and K. pneumoniae). In summary, ceftaroline showed potent activity against a large contemporary collection (6222) of bacterial isolates associated with ABSSSI in the USA.

Antimicrobial activity of ceftaroline combined with avibactam tested against bacterial organisms isolated from acute bacterial skin and skin structure infections in United States medical centers (2010-2012)

Ceftaroline-avibactam and comparator agents were tested against clinical isolates collected at 174 medical centers from patients with acute bacterial skin and skin structure infection (ABSSSI) in the United States (USA) during 2010-2012. Isolates were processed at the medical centers and forwarded to a central laboratory for confirmatory identification and susceptibility testing using reference methods. Ceftaroline-avibactam was highly active against methicillin-susceptible (MIC50/90, 0.25/0.25 μg/mL) and methicillin-resistant Staphylococcus aureus (MRSA; MIC50/90, 0.5/1 μg/mL). Vancomycin, tigecycline, daptomycin, and linezolid were also active (>99.9% susceptible) against MRSA (51.4% of S. aureus), but activity against MRSA was decreased for erythromycin, levofloxacin, and clindamycin (10.8, 40.3, and 81.9% susceptible, respectively). β-Hemolytic streptococci were highly susceptible to β-lactam antimicrobials, including ceftaroline-avibactam (MIC50/90, ≤0.03/≤0.03 μg/mL). Ceftaroline-avibactam was very active against Escherichia coli and Klebsiella pneumoniae (MIC50/90, 0.03/0.06 and 0.06/0.25 μg/mL, respectively) including extended-spectrum β-lactamase (ESBL) screen-positive phenotypes (MIC50/90, 0.06/0.12 and 0.12/1 μg/mL, respectively). Susceptibility of ESBL screen-positive E. coli and K. pneumoniae was 100.0/97.9% for tigecycline and 99.2/56.1% for meropenem, respectively. Susceptibility to other agents for ESBL screen-positive E. coli and K. pneumoniae was decreased. Ceftaroline-avibactam exhibited a broad-spectrum of in vitro activity against isolates from patients in the USA with ABSSSI including MRSA, β-hemolytic streptococci, E. coli, and K. pneumoniae as well as ESBL screen-positive phenotype isolates and merits further study in clinical indications where these resistant organisms may be a concern.

Ceftaroline fosamil for the treatment of acute bacterial skin and skin structure infections

Skin infections have traditionally been classified by the US FDA as uncomplicated and complicated. In August 2010, the FDA released a new guidance document for the development of drugs to treat acute bacterial skin and skin structure infections (ABSSSI) and this was updated in 2013. Several new issues were addressed and henceforth skin infections in clinical trials were termed ABSSSI. In the USA, the annual prevalence of methicillin-resistant Staphylococcus aureus-related skin infections have continuously increased from 32.7% in 1998 to 53.8% in 2007. Ceftaroline fosamil is the only cephalosporin approved in the USA for monotherapy treatment of ABSSSI including infections caused by methicillin-resistant S. aureus. The efficacy of ceftaroline fosamil was shown in the CANVAS clinical trials. The CANVAS Day-3 analyses met an earlier, primary efficacy time point requested by the FDA. Ceftaroline has minimal drug-drug interactions, is well tolerated and possesses the safety profile associated with the cephalosporin class.

Nested case-control study of the emergence of tigecycline resistance in multidrug-resistant Klebsiella pneumoniae

We performed a nested case-control study (ratio of 1:4) on the emergence of tigecycline-resistant multidrug-resistant Klebsiella pneumoniae (TR-MDRKP) isolates among patients who initially presented with a tigecycline-susceptible MDRKP isolate. Out of 260 patients, 24 (9%) had a subsequent clinical culture positive for a TR-MDRKP isolate within the 90-day follow-up period. On logistic regression analyses, receipt of tigecycline (adjusted odds ratio [OR], 5.06; 95% confidence interval [CI], 1.80 to 14.23; P = 0.002) was the only independent predictor of subsequent isolation of a TR strain.

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.

Ceftaroline fosamil: a review of its use in the treatment of complicated skin and soft tissue infections and community-acquired pneumonia

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil (Zinforo, Teflaro), is an advanced-generation, parenteral cephalosporin with broad-spectrum antibacterial activity in vitro against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Streptococcus pneumoniae and Gram-negative bacteria, including Haemophilus influenzae and Moraxella catarrhalis, but not Pseudomonas aeruginosa. Ceftaroline has demonstrated a low potential for the selection of resistance in vitro for drug-resistant Gram-positive organisms, including MRSA, as well as for Gram-negative respiratory pathogens. In pivotal phase III studies, intravenous ceftaroline fosamil demonstrated noninferiority to intravenous vancomycin plus aztreonam in patients hospitalized with complicated skin and soft tissue infections (cSSTIs) and intravenous ceftriaxone in patients hospitalized with community-acquired pneumonia (CAP) [Pneumonia Outcomes Research Team (PORT) risk class III or IV]; however, patients with CAP admitted to the intensive care unit were not evaluated. Ceftaroline fosamil was generally well tolerated in these trials, with an adverse event profile similar to that of other cephalosporins. Diarrhoea was the most commonly reported adverse event; however, the risk of Clostridium difficile-associated diarrhoea with ceftaroline fosamil appeared to be low. Potential limitations of the drug include the lack of an oral formulation and the requirement for twice-daily administration. Nonetheless, ceftaroline fosamil represents an attractive option (either alone or in combination with other agents) for the initial empirical treatment of patients hospitalized with cSSTIs (including those with suspected MRSA infection) or CAP (PORT risk class III or IV) who require intravenous antimicrobial therapy. As with all antibacterial agents, ceftaroline fosamil should be used in accordance with good antimicrobial stewardship.