Activity of ceftaroline and epidemiologic trends in Staphylococcus aureus isolates collected from 43 medical centers in the United States in 2009

Ceftaroline fosamil for community-acquired bacterial pneumonia and acute bacterial skin and skin structure infection

INTRODUCTION

Bacterial resistance is increasing on a global basis, making treatment options more limited. The development of new agents to meet this threat is a matter of urgency. Ceftaroline fosamil , a member of an advanced cephalosporin class of antimicrobials, is currently approved by the US Food and Drug Administration for use in for acute bacterial skin and skin structure infection (ABSSSI) and community-acquired bacterial pneumonia. Ceftaroline displays activity against Gram-positive and Gram-negative bacteria, including both methicillin-susceptible and resistant Staphylococcus aureus (MRSA), Streptococcus pneumoniae (including penicillin- and ceftriaxone-resistant strains), respiratory pathogens (such as Moraxella catarrhalis and Haemophilus influenzae, including beta-lactamase-producing strains) and limited coverage against Enterobacteriaceae.

AREAS COVERED

Chemistry, mechanism of action, spectrum of activity, resistance, pharmacokinetics/pharmacodynamics, indications for use, safety and special populations are covered in this review.

EXPERT OPINION

Ceftaroline's unique activity against MRSA and penicillin- and ceftriaxone-resistant S. pneumoniae strains is due to its high affinity for penicillin binding protein (PBP)-2a and PBP-2x, respectively. In randomized, double-blinded, clinical trials, ceftaroline fosamil was found to be non-inferior to ceftriaxone for the treatment CABP and to vancomycin plus aztreonam for ABSSSI. Substantial differences between the cephalosporins exist. Ceftaroline has unique characteristics that may make it useful in specific clinical circumstances, especially against multi-drug-resistant Gram-positive organisms.

High prevalence of Panton-Valentine leukocidin among methicillin-sensitive Staphylococcus aureus colonization isolates in rural Iowa

Recent studies have shown that livestock can carry Staphylococcus aureus and transmit it to human caretakers. We conducted a pilot study to determine the prevalence and molecular epidemiology of S. aureus among rural Iowans, including individuals with livestock contact. Nasal and throat swabs were collected and plated onto selective media to isolate methicillin-susceptible and methicillin-resistant S. aureus (MRSA), followed by antibiotic resistance testing and molecular analysis of the isolates. While no MRSA was detected, overall, 23.7% (31/131) of participants were found to harbor S. aureus in their nose, throat, or both. Fifteen isolates displayed resistance to one or more tested antibiotics, and the Panton-Valentine leukocidin (PVL) genes were present at a high level (29% [9/31] of S. aureus-positive participants). Younger age and tobacco use were associated with increased risk of S. aureus carriage. Our results suggest that carriage of PVL-positive S. aureus is common among rural Iowans, even in the absence of detectable MRSA colonization.

Critical appraisal of ceftaroline in the management of community-acquired bacterial pneumonia and skin infections

Ceftaroline is a novel broad-spectrum cephalosporin β-lactam antibiotic with activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as multidrug-resistant Streptococcus pneumoniae among other routine Gram positive and Gram negative organisms. It has been approved by the US Food and Drug Administration for treatment of community-acquired bacterial pneumonia and acute bacterial skin and skin structure infections (ABSSSIs). Ceftaroline is approved for treatment of ABSSSI due to MRSA, however currently there are no data for pneumonia due to MRSA in humans. Herein we review the major clinical trials as well as ceftaroline microbiology, pharmacokinetics, and safety, followed by a look at further directions for investigation of this new agent.

Fourteen years in resistance

Resistance trends have changed greatly over the 14 years (1997-2011) whilst I was Director of the UK Antibiotic Resistance Monitoring and Reference Laboratory (ARMRL). Meticillin-resistant Staphylococcus aureus (MRSA) first rose, then fell with improved infection control, although with the decline of one major clone beginning before these improvements. Resistant pneumococci too have declined following conjugate vaccine deployment. If the situation against Gram-positive pathogens has improved, that against Gram-negatives has worsened, with the spread of (i) quinolone- and cephalosporin-resistant Enterobacteriaceae, (ii) Acinetobacter with OXA carbapenemases, (iii) Enterobacteriaceae with biochemically diverse carbapenemases and (iv) gonococci resistant to fluoroquinolones and, latterly, cefixime. Laboratory, clinical and commercial aspects have also changed. Susceptibility testing is more standardised, with pharmacodynamic breakpoints. Treatments regimens are more driven by guidelines. The industry has fewer big profitable companies and more small companies without sales income. There is good and bad here. The quality of routine susceptibility testing has improved, but its speed has not. Pharmacodynamics adds science, but over-optimism has led to poor dose selection in several trials. Guidelines discourage poor therapy but concentrate selection onto a diminishing range of antibiotics, threatening their utility. Small companies are more nimble, but less resilient. Last, more than anything, the world has changed, with the rise of India and China, which account for 33% of the world's population and increasingly provide sophisticated health care, but also have huge resistance problems. These shifts present huge challenges for the future of chemotherapy and for the edifice of modern medicine that depends upon it.

Current concepts in laboratory testing to guide antimicrobial therapy

Antimicrobial susceptibility testing (AST) is indicated for pathogens contributing to an infectious process that warrants antimicrobial therapy if susceptibility to antimicrobials cannot be predicted reliably based on knowledge of their identity. Such tests are most frequently used when the etiologic agents are members of species capable of demonstrating resistance to commonly prescribed antibiotics. Some organisms have predictable susceptibility to antimicrobial agents (ie, Streptococcus pyogenes to penicillin), and empirical therapy for these organisms is typically used. Therefore, AST for such pathogens is seldom required or performed. In addition, AST is valuable in evaluating the activity of new and experimental compounds and investigating the epidemiology of antimicrobial resistant pathogens. Several laboratory methods are available to characterize the in vitro susceptibility of bacteria to antimicrobial agents. When the nature of the infection is unclear and the culture yields mixed growth or usual microbiota (wherein the isolates usually bear little relationship to the actual infectious process), AST is usually unnecessary and results may, in fact, be dangerously misleading. Phenotypic methods for detection of specific antimicrobial resistance mechanisms are increasingly being used to complement AST (ie, inducible clindamycin resistance among several gram-positive bacteria) and to provide clinicians with preliminary direction for antibiotic selection pending results generated from standardized AST (ie, β-lactamase tests). In addition, molecular methods are being developed and incorporated by microbiology laboratories into resistance detection algorithms for rapid, sensitive assessment of carriage states of epidemiologically and clinically important pathogens, often directly from clinical specimens (ie, presence of vancomycin-resistant enterococci in fecal specimens).

Characterization of nasal and blood culture isolates of methicillin-resistant Staphylococcus aureus from patients in United States Hospitals

A total of 299 nares and 194 blood isolates of methicillin-resistant Staphylococcus aureus (MRSA), each recovered from a unique patient, were collected from 23 U.S. hospitals from May 2009 to March 2010. All isolates underwent spa and staphylococcal cassette chromosome mec element (SCCmec) typing and antimicrobial susceptibility testing; a subset of 84 isolates was typed by pulsed-field gel electrophoresis (PFGE) using SmaI. Seventy-six spa types were observed among the isolates. Overall, for nasal isolates, spa type t002-SCCmec type II (USA100) was the most common strain type (37% of isolates), while among blood isolates, spa type t008-SCCmec type IV (USA300) was the most common (39%). However, the proportion of all USA100 and USA300 isolates varied by United States census region. Nasal isolates were more resistant to tobramycin and clindamycin than blood isolates (55.9% and 48.8% of isolates versus 36.6% and 39.7%, respectively; for both, P < 0.05). The USA300 isolates were largely resistant to fluoroquinolones. High-level mupirocin resistance was low among all spa types (<5%). SCCmec types III and VIII, which are rare in the United States, were observed along with several unusual PFGE types, including CMRSA9, EMRSA15, and the PFGE profile associated with sequence type 239 (ST239) isolates. Typing data from this convenience sample suggest that in U.S. hospitalized patients, USA100 isolates of multiple spa types, while still common in the nares, have been replaced by USA300 isolates as the predominant MRSA strain type in positive blood cultures.

Detection of Staphylococcus aureus isolates with heterogeneous intermediate-level resistance to vancomycin in the United States

The prevalence of heterogeneous intermediate-level resistance to vancomycin (hVISA) in Staphylococcus aureus was assessed by screening a large collection of recent isolates. Susceptibility testing by the Clinical and Laboratory Standards Institute broth microdilution method and the Etest GRD (glycopeptide resistance detection) method (bioMérieux) was performed on 4,210 clinically significant S. aureus isolates obtained in 2009 from 43 U.S. centers. Isolates with Etest GRD-positive results for hVISA were evaluated further by repeat GRD testing and population analysis profiling-area under the curve (PAP-AUC) analysis. No VISA (vancomycin MIC, 4 to 8 μg/ml) or vancomycin-resistant (MIC ≥ 16 μg/ml) strains were detected. The Etest GRD screen for hVISA was initially positive for 68 isolates (1.6%; all by teicoplanin MIC ≥ 8 μg/ml at 24 or 48 h). Among those 68 isolates, 45 were reproducibly GRD positive. PAP-AUC testing confirmed only 11 isolates as hVISA (all had reproducible GRD-positive results). The 11 hVISA isolates were from nine medical centers and appeared genetically diverse (ten different PFGE types). The rates of resistance (including intermediate) for hVISA were as follows: oxacillin, 82%; erythromycin, 82%; clindamycin, 73%; levofloxacin, 73%; trimethoprim-sulfamethoxazole, 9%; and daptomycin, 9%. All hVISA isolates were susceptible to linezolid, tigecycline, and ceftaroline. Our data suggest that the overall prevalence of hVISA in the United States is low (0.3%). The hVISA isolates represented 10.5% of isolates with vancomycin MICs of 2 μg/ml and 0.1% of isolates with vancomycin MICs of 1 μg/ml. The positive predictive value of GRD Etest for hVISA was 16.2% for initial screen positive and 24.4% for reproducibly positive results.