Genomic fingerprints analysis of coagulase-positive and negative Staphylococci isolated from patients with bacteremia by repetitive sequence based PCR method

Abstract

Staphylococci are important organisms involved in many infections, including bacteremia or septicemia. Repetitive sequence–based PCR (rep-PCR) is a useful method for detection of staphylococcal DNA fingerprint patterns, especially when the origins of these organisms are unknown. Staphylococcal positive blood cultures were collected from patients with bacteremia hospitalized in four hospitals. The patients who had two positive blood cultures out of three samples were considered as subjects. After isolation of Staphylococci on blood agar medium, the species of isolates were determined by standard biochemical tests. DNA was extracted from bacterial cells and genomic fragments were amplified by rep-PCR. Furthermore, relationship of strains was determined based on the similarities between DNA fingerprints by using Jaccards coefficient. In this survey, 88 cases of bacteremia caused by coagulase positive Staphylococcus aureus (36 cases), and coagulase negative strains (52 cases), were studied. Extracted DNA from staphylococcal isolates generated multiple fingerprints in sizes ranging between 600(61%) and 2642 bp (87.5%) by rep-PCR method. The fingerprint patterns of S. aureus (33 strains), S. epidermidis (32 strains) and S. lugdunensis (7 strains) were 31, 30 and 7 types, respectively. This study demonstrated only a few of Staphylococci strains that displayed similarity or that are closely related in the DNA fingerprint patterns. We concluded that rep-PCR is a rapid, simple and suitable method for epidemiological studies. The results of our study also showed that most of Staphylococci isolated from bacteremic patients produced different genomic fingerprint patterns by rep-PCR and so, at present study, dissemination source of infection is different. Key words: rep-PCR, fingerprint patterns, Staphylococci, bacteremia.