Multiple-Locus Variable-Number Tandem Repeat Analysis for Typing of Staphylococcus epidermidis

Abstract

We applied a high-resolution PCR-based typing method, multiple-locus variable-number tandem repeat analysis (MLVA), for discrimination of 30 multidrug-resistant clinical isolates of Staphylococcus epidermidis. The results of MLVA were congruent with results obtained by pulsed-field gel electrophoresis (PFGE). MLVA generated discrete character data, and its discriminatory capacity was comparable to that of PFGE.The clinical significance of Staphylococcus epidermidis is increasingly recognized. The bacterium is primarily associated with nosocomial infections such as prosthesis-and intravascular-catheter-related infections and a variety of postoperative infections (17). Moreover, nosocomial isolates of S. epidermidis frequently exhibit multidrug resistance, which limits the therapeutic arsenal (5). Despite the growing importance of S. epidermidis as a cause of hospital-acquired infections, there is still limited information available regarding the epidemiology of S. epidermidis in the hospital setting. Methods that may distinguish clinically significant strains from contaminant strains are lacking. For epidemiological studies, there is also a lack of easy-to-use, rapid typing methods with high reproducibility. Since the 1990s, pulsed-field gel electrophoresis (PFGE) of whole-genome SmaI digests has been considered the "gold standard" for molecular typing of S. epidermidis (13,14). The method has high discriminatory power but is laborious and therefore costly. Interpretation and exchange of PFGE-typing data are not uncomplicated because they depend on banding patterns and subjective decisions regarding the true existence of discrete bands. There is a consensus that exchange of typing data between laboratories is highly desirable, and systems with a binary output (numbers or characters), rather than methods generating banding patterns such as PFGE, are therefore preferred. Multiple-locus variable-number tandem repeat analysis (MLVA) has proved efficient for high-resolution typing of several bacterial species (4, 6, 16). The method targets multiple genomic loci and relies on the detection of different copy numbers of short repeated sequences that are arranged in tandem arrays. MLVA is an easy-to-use, PCR-based method that provides simple numerical data by identifying the copy numbers of tandem repeats that are present at the assayed genomic loci. The aim of the present study was to develop and evaluate an MLVA system for molecular typing of S. epidermidis.

Core genome conservation of Staphylococcus haemolyticus limits sequence based population structure analysis

“…However, previously published schemes using five tandem repeat loci in Chlamydia abortus (Laroucau et al, 2009), S. epidermidis (Johansson et al, 2006), and Salmonella enterica (Lindstedt et al, 2004) have shown satisfactory discrimination. Other studies comparing MLVF to MLST have also shown a good concordance between type assignment made by the two methods (Malachowa et al, 2005).…”

Biofilm Producing Staphylococcus epidermidis Strains Isolated From Clinical Samples in Tehran, Iran

“…The high frequency of this transposon in this study might be due to the origin of the isolates, as we did not focus on hospital strains and some of the strains were isolated from outpatients. On the other hand, the presence of IS256 among most of the biofilm-producing strains, which were positive for icaA, icaD and atlE genes, showed the correlation between these factors and clinically relevant strains (10,25,42).…”

Staphylococcus epidermidis, Clonality and Accessory Gene Regulator Diversity in Clinical Isolates

“…The MLVA was performed for S. epidermidis isolates, using seven VNTR loci, including SE2395, SE0331, SE 828, SE1632, SE0175, Se2, and Se4, as previously described (16,17). Polymerase chain reaction was performed for each locus in a 25-µL volume PCR reaction containing specific primers (Pishgam biotech, Iran).…”

“…Genotypic and phenotypic diversity have been created due to point mutation, recombination or other addition methods as well as deletion of mobile genetic elements (14). Different methods of typing and criteria are used to determine the closeness of strains, although time and place should also be considered (13)(14)(15)(16).…”