Prevalence and characterization of heterogeneous vancomycin-intermediate Staphylococcus aureus isolates from 14 cities in China.
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.
Sun
Wenjia
W
Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, People's Republic of China.
Chen
Hongbin
H
Liu
Yudong
Y
Zhao
Chunjiang
C
Nichols
Wright W
WW
Chen
Minjun
M
Zhang
Jianzhong
J
Ma
Yue
Y
Wang
Hui
H
D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D002681:China; D002947:Cities; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000187:drug effects* / Q000235:genetics; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D014640:Vancomycin / Q000494:pharmacology / Q000627:therapeutic use; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D014640:Vancomycin