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Antimicrobial Agents and Chemotherapy, September 2009, p. 3642-3649, Vol. 53, No. 9
0066-4804/09/$08.00+0 doi:10.1128/AAC.00206-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Prevalence and Characterization of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Isolates from 14 Cities in China
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Wenjia Sun,1,2,
Hongbin Chen,1,2,
Yudong Liu,1,2
Chunjiang Zhao,1,2
Wright W. Nichols,3
Minjun Chen,1
Jianzhong Zhang,4
Yue Ma,5 and
Hui Wang1,2*
Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, People's Republic of China,1 Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, People's Republic of China,2 AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts 02451,3 Chinese Center for Disease Control and Prevention, Beijing 102206, People's Republic of China,4 National Institute for the Control of Pharmaceutical and Biological Products, Beijing 100050, People's Republic of China5
Received 15 February 2009/ Returned for modification 27 March 2009/ Accepted 31 May 2009
The prevalence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among 1,012 vancomycin-susceptible methicillin (meticillin)-resistant S. aureus isolates collected from 14 cities in China from 2005 to 2007 was 13 to 16%, as determined by a combination of (i) measurement by the modified population analysis profile-area under the curve method (PAP-AUC) and (ii) estimation from the measured sensitivity and specificity of a screening method. Two hundred isolates from blood were chosen as a subset for measurement of the sensitivities and the specificities of several previously described screening methods by using the results of PAP-AUC as the reference. During this testing, one isolate was found to be a vancomycin-intermediate S. aureus (VISA) strain so was not used in the evaluation of the screening tests. Of the other 199 isolates, 26 (13.1%) were hVISA, as assessed by PAP-AUC. A screening cascade of culturing the isolates on brain heart infusion agar containing teicoplanin (5 mg/liter) and then subjecting the positive isolates to a macro-Etest method was applied to the 812 non-blood isolates, yielding 149 positive results. From these results and by adjusting for sensitivity (0.423) and specificity (0.861), the prevalence was estimated to be 15.7%. The precision of that estimate was assessed by reapplying the screening cascade to 120 randomly selected isolates from the 812 non-blood isolates and simultaneously determining their heterogeneous vancomycin-intermediate susceptibility status by PAP-AUC. Because PAP-AUC is impractical for use with large numbers of isolates, the screening-based estimation method is useful as a first approximation of the prevalence of hVISA. Of the 27 VISA or hVISA isolates from blood, 22.2% and 74.1% were staphylococcal chromosome cassette mec types II and III, respectively, while 77.8% and 22.2% were agr type 1 and agr type 2, respectively; the MIC ranges were 0.5 to 4 mg/liter for vancomycin and 0.25 to 1 mg/liter for daptomycin.
* Corresponding author. Mailing address: Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, No. 1 Shuaifuyuan, Wangfujing, Beijing 100730, People's Republic of China. Phone and fax: 86-10-6529-5406. E-mail: wh_bj{at}tom.com
Published ahead of print on 22 June 2009.
Supplemental material for this article may be found at http://aac.asm.org/.
W. Sun and H. Chen contributed equally to this paper.
Antimicrobial Agents and Chemotherapy, September 2009, p. 3642-3649, Vol. 53, No. 9
0066-4804/09/$08.00+0 doi:10.1128/AAC.00206-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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