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العنوان
Prevalence of Panton Valentine Gene in both Community-acquired and Healthcare-acquired Methicillin Resistant Staphylococcus aureus Isolates /
المؤلف
Mohamed, Rana Abd el fattah Abd el Fattah.
هيئة الاعداد
باحث / رنا عبد الفتاح عبد الفتاح
مشرف / لميـــــاء فـــــؤاد فتحــــى
مشرف / نهى ناجى محمد صلاح الدين
تاريخ النشر
2018.
عدد الصفحات
136 p. :
اللغة
الإنجليزية
الدرجة
ماجستير
التخصص
علم المناعة والحساسية
تاريخ الإجازة
1/1/2018
مكان الإجازة
جامعة عين شمس - كلية الطب - الميكروبيولوجيا الطبية والمناعة
الفهرس
Only 14 pages are availabe for public view

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from 136

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen distributed worldwide and a leading cause of morbidity and mortality. It causes a variety of infections ranging in severity from mild to severe, life threatening conditions.
Methicillin-resistant Staphylococcus aureus is classified into Hospital acquired methicillin resistant Staphylococcus aureus (HA-MRSA) and Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA).
HA-MRSA is frequently responsible for serious and often life-threatening infections in individuals with established risk factors, such as prolonged hospital stay and antibiotic usage, older age, recent surgery, or an immunocompromised state.
CA-MRSA is considered now a health care problem, the Centers for Disease Control and Prevention (CDC) had established a definition for identification of community acquired S. aureus which stated that a case of MRSA infection is community acquired when it is diagnosed in an outpatient or within 48 hours of hospitalization if the patient lacks the following traditional risk factors for MRSA infection: receipt of hemodialysis, surgery, residence in a long-term care facility, or hospitalization during the previous year, the presence of an indwelling catheter or a percutaneous device at the time culture samples were obtained, or previous isolation of MRSA.
There was genotypic variation among different S. aureus infections as staphylococcal cassette chromosome mec (SCC mec) confer different microbiological characteristics, such as different antimicrobial resistance rates, so different (SCC mec) genotypes are associated with different types of infections. Types I-III SCC mec are large elements that typically contain additional resistance genes and are characteristically isolated from HA-MRSA strains. Conversely, CA-MRSA is associated with types IV and V, which are smaller and lack resistance genes other than mecA.
Infections caused by CA-MRSA have been associated with the presence of Panton-Valentine leukocidin (PVL) and associated with increased disease severity, ranging from cutaneous infection requiring surgical drainage to severe chronic osteomyelitis and deadly necrotizing pneumonia.
The Panton-Valentine leukocidin (PVL) is an extracellular product of S. aureus that is encoded by the genes lukS-PV and lukF-PV, characterized by its cytolytic pore forming activity that cause damage to the cell membranes of neutrophils, monocytes and macrophages.
The study was conducted on eighty-nine (89) clinical isolates of S. aureus to isolate fifteen (15) community acquired isolates and fifteen (15) hospital acquired isolates) isolated from different clinical specimens from adult patients. All isolates were conventionally identified then genotypic detection of mecA gene and pvl gene by polymerase chain reaction (PCR).
In the present study among fifteen (15) isolates of HA-MRSA that was identified phenotypically as MRSA by using mannitol salt agar with cefoxitin disc (30 ug), mecA was positive in 40% (6/15) compared to 47.6% (7/15) of the fifteen (15) CA-MRSA isolates. While, pvl gene was positive 53.3% (8/15) in HA-MRSA isolates compared to 26.7% (4/15) of CA-MRSA isolates.
Among the fifteen (15) CA-MRSA isolates, mecA was positive in 46.7% of samples isolated from skin infection. While PVL gene was positive in 26.7% (4/15) of samples isolated from patients with skin infections.
Among the fifteen (15) HA-MRSA isolates, mecA gene was positive in only 57.1% (4/7) of skin samples obtained from burn infection and 33.3% (2/6) of sputum samples isolated from patients with respiratory tract infection (RTI) while mecA was not detected in blood samples isolated from septicemic patients. While pvl gene was positive in 71.4% (5/7) of skin samples obtained from burn infection from ICU department, 16.7%(1/6) of sputum samples obtained from patients with respiratory tract infection (RTI) and 100%(2/2) positive in blood samples isolated from septicemic patients.
In conclusion the results showed that there was no significant correlation between mecA gene and pvl gene among the studied thirty (30) MRSA isolates (P value =1), as 50% (3/6) only of positive mecA were positive for pvl, and 44.4% (4/9) of negative mecA were negative pvl. The results of detection of pvl gene in both community and hospital isolates made this gene not a sole genetic marker for diagnosis of CA-MRSA.