Using Real Time PCR for Rapid Detection of Community-Acquired Staphylococcus aureus Panton-Valentine leukocidin (PVL) Gene in Pediatric Infections

Abstract

Community-acquired S. aureus is becoming an important public health problem. Centers for Disease Control and Prevention set criteria for definition of Community-acquired S. aureus. The diagnosis based on the outpatient setting or on the basis of a positive culture for MRSA within 48 hours after hospital admission, no history in the preceding year of hospitalization, no dialysis, no surgery, no permanent indwelling catheters or medical devices that pass through the skin into the body. Genetic variation affects the clinical manifestations of different S. aureus clones. The staphylococcal cassette chromosome mec (SCCmec) region contains antibiotic resistance genes; Community-acquired S. aureus isolates carry smaller SCCmec types (IV and V) with fewer resistance genes than hospital-acquired strains. Community-acquired S. aureus differs from hospital-acquired S. aureus in that Community-acquired S. aureus is not multidrug-resistant and can usually be treated with clindamycin, rifampicin and linezolid. Panton-Valentine leukocidin (PVL) is a cytotoxin, one of the pore-forming toxins. PVL creates pores in the membranes of infected cells. PVL hashas beenbeen associated associatedassociatedassociated associated associated withwithwithwith chronic chronic chronicchronicchronic or recurrent recurrent recurrent skin and and softsoftsoft tissue infectionsinfectionsinfections infectionsinfectionsinfectionsinfections and and withwithwithwith necrotizingnecrotizing necrotizingnecrotizingnecrotizing necrotizingnecrotizing pneumoniapneumoniapneumonia pneumoniapneumoniapneumoniapneumoniapneumonia. It is present in the majority of community acquired S. aureus isolates studied. Summary - 104 - The study was conducted on total number of fifty S. aureus isolates from pediatrics patients. Isolates were identified by morphological, cultural and biochemical characteristics. All isolates were subjected to genotypic method for detection of PVL gene by real-time PCR. Recently hospitalized patients within 48 hours were asked about pervious hospitalization in the last year, antibiotic intake, comorbid condition and contact to medical staff. The PVL gene was detected in 46 (92%) out of 50 isolates by PCR. From CA-MRSA 93.8% carry PVL gene and 91.3% of CA-MSSA carry PVL gene. A significant relationship was found between osteomyelitis and CA-MRSA compare to CA-MSSA. From outpatients 11 out of 14 were PVL gene positive, while from recently hospitalized patients 35 out of 36 were PVL gene positive. There is a higher percentage of PVL gene positivity among hospitalized patients and it is statistically significant. In the present study, the PVL gene was detected in 100% of osteomyelitis, bacteremia and pneumonia, 86.3% of soft tissue infection of, 80% in UTI and other types of infection respectively. Conclusion: As PVL is one of the pore-forming toxins that cause serious conditions. The results showed that 96% of isolates were positive using real time PCR. Early detection of PVL gene is recommended to adjust antimicrobial therapy. Summary - 105 - Recommendations: Laboratories should provide more rapid method for detection of PVL gene such as immuno-chromatography and ELISA to adjust antibiotics therapy