Strain-relatedness of methicillin-resistant Staphylococcus aureus isolates recovered from patients with repeated infection.

Invasive disease following methicillin-resistant Staphylococcus aureus (MRSA) detection is common, regardless of whether initial detection involves colonization or infection. We assessed the genetic relatedness of isolates obtained > or =2 weeks apart representing either repeated infections or colonization-infection sets to determine if infections are likely to be caused by previously harbored strains. We found that MRSA infection following initial colonization or infection is caused by the same strain in most cases, suggesting that a single successful attempt at decolonization may prevent the majority of later infection.

Candidemia surveillance in Iowa: emergence of echinocandin resistance.

We performed prospective surveillance for candidemia at 14 Iowa hospitals in 2011-2012. A total of 163 episodes were analyzed. Candida albicans (n = 69 [42%]) and Candida glabrata (n = 58 [36%]) were the most common species. Antifungal resistance was uncommon; 9% of C. glabrata were fluconazole resistant, and 5% (3 isolates) were intermediate or resistant to 1 or more of the echinocandins. Molecular analyses of the fks1 and fks2 hotspots of the C. glabrata revealed no mutations except in 2 of these 3 isolates (L628R and S629P in fks1). Compared with previous surveillance performed in 1998-2001, there was a decrease in proportion of candidemia due to C. albicans (58 to 42%) and an increased proportion due to C. glabrata (20 to 36%). Further emergence of echinocandin resistance among the increasingly common species C. glabrata would complicate the management of this life-threatening infection.

Continued emergence of USA300 methicillin-resistant Staphylococcus aureus in the United States: results from a nationwide surveillance study.

BACKGROUND: The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is changing, with USA300 emerging first in community and then in healthcare settings. We performed nationwide surveillance to assess recent trends in the molecular epidemiology of MRSA. METHODS: One hundred consecutive unique clinically significant S. aureus isolates were recovered from patients at each of 43 US centers between July 1, 2011, and December 31, 2011. Susceptibility testing, pulsed-field gel electrophoresis (PFGE), staphylococcal protein A gene (spa) and staphylococcal cassette chromosome mec typing, and Panton-Valentine leukocidin detection were performed on all MRSA isolates. RESULTS: Of 4,131 isolates collected, 2,093 (51%) were MRSA. Specimen sources of MRSA isolates included wound or abscess (54%), blood (24%), lower respiratory tract (11%), and other sterile site (10%). Thirty percent were isolated more than 48 hours after hospital admission (ie, were associated with nosocomial acquisition of infection). USA300 was the most common PFGE type (1,269 isolates; 61%), overall and in all regions, followed by USA100 (368 isolates; 18%). Among 173 spa types found, the most common were t008 (51%) and t002 (18%); no other spa type accounted for more than 2% of isolates. One strain type (USA300/t008/IV) constituted almost half of all MRSA isolates (1,005 isolates; 48%) and was the most common at all body sites, causing 37% of MRSA bloodstream infections (BSIs) and 38% of nosocomial MRSA infections. Multidrug-resistant phenotypes were found among 34 USA300 isolates (3%) from 18 states. CONCLUSIONS: The USA300 PFGE type continues to advance nationwide. A single strain type (USA300/t008/IV) predominates in all regions and infection sites and is now more common than USA100 as a cause of MRSA BSI and nosocomial infections. Although most USA300 retain typical susceptibility profiles, multidrug-resistant phenotypes are emerging.

Wild-type minimum effective concentration distributions and epidemiologic cutoff values for caspofungin and Aspergillus spp. as determined by Clinical and Laboratory Standards Institute broth microdilution methods.

Antifungal susceptibility testing of Aspergillus spp. against caspofungin has been standardized by the Clinical and Laboratory Standards Institute (CLSI). Recent studies have documented breakthrough infections with Aspergillus spp. for which the minimum effective concentration (MEC) for caspofungin ranged from 0.25 to 8 microg/mL. We tested a collection of 1590 clinical isolates of Aspergillus spp. (188 Aspergillus flavus, 1187 Aspergillus fumigatus, 114 Aspergillus niger, 71 Aspergillus terreus, and 30 Aspergillus versicolor) against caspofungin using the CLSI broth microdilution method. An epidemiologic cutoff value (ECV) of 8 microg/mL [1]), and 1 A. versicolor (4 microg/mL). The establishment of the WT MEC distributions and ECVs for caspofungin and the major species of Aspergillus will be useful in resistance surveillance and is an important step toward the development of clinical breakpoints.

Comparison of results of fluconazole and voriconazole disk diffusion testing for Candida spp. with results from a central reference laboratory in the ARTEMIS DISK Global Antifungal Surveillance Program.

The accuracy of antifungal susceptibility testing is important for reliable resistance surveillance and for the clinical management of patients with serious infections due to Candida spp. Our primary objective was to compare the results of fluconazole and voriconazole disk diffusion testing of 3227 Candida spp. performed by 47 centers participating in the ARTEMIS program with disk diffusion and MIC results obtained by the central reference laboratory. The overall categoric agreement between participant disk diffusion test results and reference MIC results was 87% for fluconazole and 95.2% for voriconazole. Likewise good agreement was observed between participant disk diffusion test results and reference laboratory disk diffusion test results, with an agreement of 90.5%, 1% very major error (VME), and 3.4% major error (ME) for fluconazole and 94.2%, 1.1% VME, and 2.5% ME for voriconazole. The disk diffusion test was reliable for detecting those isolates of Candida spp. that were characterized as resistant to fluconazole and voriconazole by MIC testing. External quality assurance data obtained by surveillance programs such as the ARTEMIS Global Antifungal Surveillance Program ensure the generation of useful surveillance data and result in the continued improvement of antifungal susceptibility testing protocols.

A global evaluation of voriconazole activity tested against recent clinical isolates of Candida spp.

Voriconazole susceptibility testing was performed on 7191 Candida spp. from 78 centers worldwide between 2004 and 2007. Voriconazole was very active in vitro (MIC(50)/MIC(90), 0.008/0.25 microg/mL; 98% susceptible). In comparison to 5866 Candida spp. isolates collected during global surveillance from 1997 to 2001, there were no changes in voriconazole mean MIC or MIC distribution.

Evaluation of disk diffusion and Etest compared to broth microdilution for antifungal susceptibility testing of posaconazole against clinical isolates of filamentous fungi.

We performed Etest, disk diffusion, and broth microdilution susceptibility testing of posaconazole against 146 clinical isolates of filamentous fungi. By using provisional breakpoints for comparison purposes only, categorical agreement between the results of the agar-based methods and those of broth microdilution were 96 to 98%, with no very major errors. These agar-based methods hold promise as simple and reliable methods for determining the posaconazole susceptibilities of filamentous fungi.

Evaluation of Etest and disk diffusion methods compared with broth microdilution antifungal susceptibility testing of clinical isolates of Candida spp. against posaconazole.

We performed Etest, disk diffusion, and broth microdilution susceptibility testing of 2,171 clinical isolates of Candida spp. against posaconazole. By using provisional breakpoints for comparison purposes only, the categorical agreement between the agar-based methods and broth microdilution results ranged from 93 to 98%, with <1% very major errors. The essential agreement (within 2 well dilutions) between the Etest and broth microdilution methods was 94%. These agar-based methods hold promise as simple and reliable methods for determination of the posaconzole susceptibilities of Candida spp.

Caspofungin activity against clinical isolates of fluconazole-resistant Candida.

A total of 7,837 clinical isolates of Candida were tested against fluconazole, and 351 resistant (fluconazole MIC >/=64 micro g/ml) isolates were identified (4% of the total tested). All fluconazole-resistant isolates were inhibited by caspofungin at concentrations that can be exceeded by standard doses (MIC at which 90% of the isolates were inhibited, 1 micro g/ml; 99% of the MICs were