Activity of Ceftaroline and Epidemiologic Trends in Staphylococcus aureus Isolates Collected from 43 Medical Centers in the United States in 2009

Abstract

A Staphylococcus aureus surveillance program was initiated in the United States to examine the in vitro activity of ceftaroline and epidemiologic trends. Susceptibility testing by Clinical and Laboratory Standards Institute broth microdilution was performed on 4,210 clinically significant isolates collected in 2009 from 43 medical centers. All isolates were screened for mecA by PCR and evaluated by pulsed-field gel electrophoresis. Methicillin-resistant S. aureus (MRSA) were analyzed for Panton-Valentine leukocidin (PVL) genes and the staphylococcal cassette chromosome mec (SCCmec) type. All isolates had ceftaroline MICs of <2 g/ml with an MIC 50 of 0.5 and an MIC 90 of 1 g/ml. The overall resistance rates, expressed as the percentages of isolates that were intermediate and resistant (or nonsusceptible), were as follows: ceftaroline, 1.0%; clindamycin, 30.2% (17.4% MIC > 4 g/ml; 12.8% inducible); daptomycin, 0.2%; erythromycin, 65.5%; levofloxacin, 39.9%; linezolid, 0.02%; oxacillin, 53.4%; tetracycline, 4.4%; tigecycline, 0%; trimethoprim-sulfamethoxazole, 1.6%; vancomycin, 0%; and high-level mupirocin, 2.2%. The mecA PCR was positive for 53.4% of the isolates. The ceftaroline MIC 90 s were 0.25 g/ml for methicillin-susceptible S. aureus and 1 g/ml for MRSA. Among the 2,247 MRSA isolates, 51% were USA300 (96.9% PVL positive, 99.7% SCCmec type IV) and 17% were USA100 (93.4% SCCmec type II). The resistance rates for the 1,137 USA300 MRSA isolates were as follows: erythromycin, 90.9%; levofloxacin, 49.1%; clindamycin, 7.6% (6.2% MIC > 4 g/ml; 1.4% inducible); tetracycline, 3.3%; trimethoprim-sulfamethoxazole, 0.8%; high-level mupirocin, 2.7%; daptomycin, 0.4%; and ceftaroline and linezolid, 0%. USA300 is the dominant clone causing MRSA infections in the United States. Ceftaroline demonstrated potent in vitro activity against recent S. aureus clinical isolates, including MRSA, daptomycinnonsusceptible, and linezolid-resistant strains.

Characterization of Nasal and Blood Culture Isolates of Methicillin-Resistant Staphylococcus aureus from Patients in United States Hospitals

“…A recent report on MRSA strain types from 43 U.S. medical centers by Richter et al (38) shows a larger proportion of USA100 than USA300 isolates among blood isolates nationwide, even though, overall, there were over 3 times as many USA300 isolates recovered across all specimen types compared to USA100 isolates (1,137 versus 377, respectively). Given that five of nine U.S. census regions showed similar data in our convenience sample (where USA100 predominates), we do not believe that our data are necessarily in conflict with those reported by Richter et al (38). Unfortunately, the data in the latter study were not reported by geographic region.…”

Genomic insights into the emergence and spread of international clones of healthcare-, community- and livestock-associated meticillin-resistant Staphylococcus aureus : Blurring of the traditional definitions

“…However, these MRSA failed to become established in hospitals in the UK and Denmark [20]. isolates are increasingly recognised as a cause of hospital-associated bacteraemia [35][36][37]. Indeed, the USA300 epidemic peaked in 2004 leading to the mathematical Page 13 of 34 A c c e p t e d M a n u s c r i p t 13 predictions that the USA300 CA-MRSA strains will eventually displace the HA-MRSA strains owing to the survival advantage of the former as a result of smaller and fewer genes leading to enhanced fitness [38].…”

Detection of Staphylococcus aureus Isolates with Heterogeneous Intermediate-Level Resistance to Vancomycin in the United States

“…The mecA PCRpositive isolates (53.4% of collection) had been analyzed by SCCmec typing and Panton-Valentine leukocidin (PVL) gene analysis using modifications of previously published methods (14,18,20). Details of the epidemiologic trends for the entire collection were recently published (23).…”