Investigation of the Presence of Panton-Valentine Leukocidin and Clonal Relationship of Community- and Hospital-Acquired Clinical Isolates of Staphylococcus aureus

Abstract

Staphylococcus aureus is one of the most important pathogens that cause community- and hospital-acquired infections by its toxins and enzymes. Panton-Valentine leukocidin (PVL), a cytotoxin which is especially produced by community-acquired S.aureus strains that cause soft tissue and skin infections and pneumonia. PVL leads to the destruction on polymorphonuclear cells by necrosis or induce apoptosis, so that it has great importance in the virulence of the organism. PVL can also exacerbate the clinical course of S.aureus infections and may lead to severe complications. Studies show that community-acquired PVL-positive S.aureus strains have become prevalent in hospital environments. In this study, we aimed to investigate the presence of PVL from hospital- and community-acquired S.aureus strains and to determine the clonal relationship between the PVL-positive strains. A total of 265 S.aureus strains isolated from different clinical samples (wound, blood, tracheal aspirate, urine, drainage, catheter, parasynthesis fluid) of which 88 were community-acquired and 177 were hospital-acquired according to the CDC criteria were included in the study. Methicillin resistance of the strains were investigated by conventional methods, the presence of PVL and mecA gene regions by polymerase chain reaction, and clonal relationship among the PVL positive S.aureus strains by pulsed-field gel electrophoresis (PFGE). Community-acquired 12.5% (11/88) and hospital-acquired 43% (76/177) of the strains were found resistant to methicillin. Community-acquired (CA) strains were most commonly isolated from wound samples (86%), while 34% of hospital-acquired (HA) strains were isolated from wound, and 33% were from blood samples. The rate of PVL positivity among CA- and HA-strains were found as 15% and 3%, respectively. Hospital-acquired PVL-positive strains were isolated from the samples originating from pediatric (n= 1) and neurology inpatient clinics and intensive care unit (n= 3). Thirty nine percent of PVL-positive CA-S.aureus strains were isolated from samples originated from internal medicine, 23% from general surgery, 15% from dermatology, 15% from orthopedic surgery and 8% from pediatrics outpatient clinics. Ninety two percent of PVL-positive CA-S.aureus strains have been isolated from wound samples, while 67% of HA-S.aureus strains from wound and 33% from blood samples. Five PVL-positive HA- methicillin-sensitive S.aureus strains were found clonally-related with each other by PFGE. When the macrorestriction patterns were evaluated according to Tenover criteria; three of those isolates were indistinguishable, and two were clonally unrelated. There was no clonal relationship between community-acquired strains. In conclusion we observed that PVL could be detected not only in community-acquired strains but also in hospital-acquired strains. The spread of PVL-positive strains in the hospital environment and even create epidemics, increases the risk of mortality and morbidity. Epidemiological studies will help us to understand the clonal spread of CA and HA-S.aureus strains.