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Updated: May 7, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Reduced vancomycin susceptibility found in methicillin-resistant and methicillin-sensitive Staphylococcus aureus
Jian Hu1, Xiao Xue Ma, Yuan Tian
1Department of Medical Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang, People's Republic of China ; Department of Clinical Laboratory, Yixing Hospital of Traditional Chinese Medicine, Yixing, Jiangsu, People's Republic of China.
Background:
Strains of Staphylococcus aureus with an intermediate level of resistance to vancomycin (vancomycin-intermediate S. aureus, or VISA) or which contain subpopulations of mixed susceptibility (heterogeneous VISA, or hVISA) have been reported worldwide. However, the prevalence of VISA and hVISA infections in Northeast China is unknown. From 2007 through 2010, we surveyed the vancomycin susceptibility of methicillin-resistant and methicillin-sensitive S. aureus (MRSA and MSSA, respectively) clinical isolates in Northeast China.
Methods:
S. aureus clinical isolates (369 MRSA and 388 MSSA) were screened for hVISA and VISA on brain heart infusion agar containing 3 μg/mL vancomycin, and their identity confirmed using a modified population analysis profile-area under the curve method and broth microdilution. All hVISA and VISA isolates were characterized genotypically and phenotypically.
Results:
Ten percent and 0.5 percent of the isolates were hVISA and VISA, respectively. The proportion of hVISA among MSSA isolates for the entire study period was 4.1%, but increased significantly year-by-year, from 1.2% in 2007 to 7.2% in 2010. The predominant sources of hVISA and VISA isolates were sputum (56.3%), pus (18.8%), and blood (8.8%). Molecular typing of hVISA and VISA strains revealed that, taken together, 80% contained the accessory gene regulator (agr) group II, and of these, 85.7% of the MR-hVISA and MR-VISA strains were staphylococcal cassette chromosome mec (SCCmec) type II. The adherence ability of all hVISA and VISA strains was reduced compared with that of vancomycin-susceptible strains, shown by biofilm assay.
Conclusions:
The percentage of hVISA strains was high and increased each year. The proportion of hVISA among MSSA specifically also increased significantly each year. In isolates collected from diverse infection sites, hVISA and VISA strains were found predominantly in sputum, pus, and blood, in descending order. Testing for vancomycin susceptibility should include both MRSA and MSSA isolates collected from different clinical sites.
Insights
The prevalence of vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) is increasing in Northeast China, particularly among methicillin-sensitive S. aureus (MSSA) strains. Susceptibility testing should encompass diverse clinical isolates.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Vancomycin resistance in Staphylococcus aureus, including vancomycin-intermediate (VISA) and heterogeneous (hVISA) strains, is a global concern.
- The prevalence of VISA and hVISA in Northeast China remained uncharacterized prior to this study.
- This research addresses the knowledge gap regarding VISA and hVISA prevalence in this region.
Purpose of the Study:
- To determine the prevalence of vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) among clinical isolates in Northeast China.
- To analyze trends in VISA and hVISA prevalence over a four-year period (2007-2010).
- To characterize the genotypic and phenotypic features of these resistant strains.
Main Methods:
- Screening of 369 methicillin-resistant S. aureus (MRSA) and 388 methicillin-sensitive S. aureus (MSSA) isolates for hVISA and VISA.
- Confirmation of resistance using modified population analysis profile-area under the curve and broth microdilution.
- Genotypic and phenotypic characterization, including molecular typing and biofilm assays.
Main Results:
- Ten percent of isolates were identified as hVISA and 0.5% as VISA.
- The proportion of hVISA among MSSA isolates significantly increased from 1.2% in 2007 to 7.2% in 2010.
- Predominant sources of hVISA/VISA were sputum (56.3%), pus (18.8%), and blood (8.8%).
Conclusions:
- A significant and increasing proportion of hVISA strains were detected in Northeast China, notably among MSSA.
- hVISA and VISA strains were most frequently isolated from sputum, pus, and blood.
- Comprehensive vancomycin susceptibility testing, including MRSA and MSSA from various clinical sites, is recommended.
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