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

Quorum-sensing systems are considered as important mechanisms for pathogenesis and bacterial communication. The accessory gene regulator (agr) is one of the quorum-sensing systems in staphylococci, which is generally conserved. It is believed that there is a correlation between agr groups and infection. Multiple-locus VNTR analysis is a method for bacterial typing, previously applied for several different species of bacteria. This study aimed at determining the diversity of Staphylococcus epidermidis accessory gene regulator and clonality in clinical isolates from intensive care unit patients, Tehran, Iran.
A total of 59 Staphylococcus epidermidis isolates were obtained from intensive care unit patients. The MLVA was performed for S. epidermidis isolates, using seven VNTR loci, including SE2395, SE0331, SE 828, SE1632, SE0175, Se2, and Se4. Specific primers were used for agr diversity determination.
The agr type I was observed in 29 (49%), while each of the agr type II and agr type III were observed in 10 (17%). Furthermore, 10 (17%) isolates were untypeable with using primers. In total, 49 MLVA genotypes were discriminated. Isolates were classified to six clonal complexes. Of the 59 isolate, 33 were included in clonal complex 1 (CC1), the largest of which harbored 15 (45.4%) agr type I.
Agr type I was observed in the majority of the isolates. The MLVA results of this study suggest that there was a clone with 33 samples, comprised of 56% of isolates; smaller clones each comprised of two to seven isolates, and four isolates in the form of singleton. It seems that big clone isolates were settled in the intensive care unit (ICU), and singleton isolates entered the ward by visitors or medical personnel and caused infection.