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Evaluation of MLVA and spa-typing as a rapid method for studying relationships of human and bovine Staphylococcus aureus

Abstract number: 1733_1090

Ikawaty R., Verhoef J., Fluit A.C.

Objectives: At present, there is a need for a simple, efficient and high-resolution molecular typing method for S. aureus to rapidly detect outbreaks and to study evolutionary relationships. Therefore, we developed and evaluated a Multiple Locus Variable-number tandem repeat Analysis (MLVA) system combined with spa-typing on human and bovine S. aureus (HSA and BSA respectively).

Methods: Six loci (SIRU01, 05, 07, 13, 15 and 21) of 103 and 88 S. aureus isolated from humans and bovine mastitis were amplified. The number of repeat units of each locus was calculated from each amplicon. Multi Locus Sequence Typing (MLST) was used as a reference method. All HSA isolates have a known sequence type (ST) and they were well distributed within the population of S. aureus. MLST of BSA isolates was performed as part of this study. Spa-type was determined by PCR and sequencing.

Results: Almost all isolates yielded a product for the MLVA PCR. Some isolates yielded no locus-specific products. These loci were assigned an X. Variations in repeat units were observed in all loci. Large variation in the number of repeat units suggests a greater discriminatory power as shown for SIRU05, 13 and 21 of HSA isolates, and for SIRU21 of BSA isolates. It seems that HSA and BSA can be differentiated by the presence or absence of SIRU05 and 07. The absence of locus-specific PCR products and the presence of repeat numbers for each locus are shown in the table. HSA isolates revealed 46 spa-types and 3 new spa-types, whereas BSA isolates showed 5 spa-types and 1 new spa-type. When we compared the data obtained from MLVA combined with spa-type and the data from MLVA, variations within sequence types (ST) were observed indicating the MLVA combined with spa-type has better discriminatory power.

LOCUSHAS (n = 103)BSA (n = 88)
% of PCR neg.No. of repeats% of PCR neg.No. of repeats  
SIRU016.80–501–6
SIRU0523.31–22100 
SIRU071.91–3922–3
SIRU131.90–26421–5
SIRU150.90–500–3
SIRU2101–1802–12

Conclusions: The majority of S. aureus isolates can be typed by MLVA and spa-typing. The discriminatory power to detect outbreaks for HSA is good, but questionable for BSA.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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