Use of Variations in Staphylococcal Interspersed Repeat Units for Molecular Typing of Methicillin-Resistant Staphylococcus aureus Strains

Abstract

Staphylococcal interspersed repeat unit typing has previously been shown to have the ability to discriminate between epidemic methicillin-resistant Staphylococcus aureus strains in the United Kingdom. The current study illustrates its ability to distinguish between strains within an endemic setting thereby providing a rapid transportable typing method for the identification of transmission events.

Characterization of Dutch Staphylococcus aureus from bovine mastitis using a Multiple Locus Variable Number Tandem Repeat Analysis

“…A combination of 6 loci (SIRU01, 05, 07, 13, 15 and 21 (spa)) from a previous study by Hardy et al (2006) were used for MLVA typing. Amplification of SIRUs (Staphylococcal Interspersed Repeat Units) was performed as described before (Ikawaty et al, 2008).…”

Staphylococcal Interspersed Repeat Unit Typing of Staphylococcus aureus : Evaluation of a New Multilocus Variable-Number Tandem-Repeat Analysis Typing Method

“…In a first approach, we tested the method with four completely sequenced strains (N315 [ST5-SCCmec II], NCTC8325 [ST8-MSSA], COL [ST250-SCCmec I], and MW2 [ST1-SCCmec IV]) for which theoretical SIRU profiles had previously been published (36,38). Five of the seven loci were amplified from the four tested strains; SIRU16 was amplified from strain MW2 only, whereas SIRU05 was amplified from all strains except MW2.…”

“…SIRU05 showed the lowest typeability (72%), followed by SIRU15 (95%), while the remaining SIRUs showed a typeability of 99% (one isolate was nontypeable). The consistent nonamplification of SIRU05 from all strains belonging to particular CCs, i.e., CC22, CC45, and CC80, led us to perform a BLAST (36) has no similarity with strains MW2, MSSA476, EMRSA-15 (ST22), and RF122 (ST151). Therefore, a new SIRU05R2 reverse primer was designed considering these particular strains (see Materials and Methods), and a new PCR was performed on all isolates for which this locus was not amplified with the previously published SIRU05R primer.…”

“…DNA was extracted as previously reported (3). The SIRU method was performed as previously described (36,38), with the following minor modifications: (i) 0.5 U of AmpliTaq DNA polymerase (Applied Biosystems, CA) was used per PCR in a final volume of 25 l, (ii) an annealing temperature of 59°C was used with primer SIRU05R2 (see below), and (iii) PCR products (10 l) were resolved in a 2.5% Seakem LE (Cambrex, Rockland, ME) agarose gel in 0.5% Tris-borate-EDTA buffer (Bio-Rad, Hercules, CA) at 5 V/cm for 2.5 h. The size of each amplicon was determined by visual inspection by comparison with a 50-bp ladder size marker and by computer analysis using Bionumerics, version 4.61, software, which facilitates marker-based normalization of the migration distances and therefore guarantees accurate length measurements. The number of repeats was calculated, taking into account the combined size of the The primers used to amplify each of the seven loci were previously published (36), except for those for locus 16 (SIRU16) and an additional reverse primer for locus 5 (SIRU05).…”

“…This allelic profile makes the SIRU method amenable to interlaboratory comparisons and database management, comparable to MLST. So far, the SIRU method has been applied to S. aureus isolates from nosocomial outbreaks in the United Kingdom and Germany, mainly MRSA isolates, and therefore to highly related strains (29,(35)(36)(37). Very recently, a single study evaluated a MLVA scheme including the SIRU typing loci and the sspA gene, using a European collection of contemporary S. aureus isolates (39).…”