Abstract
Staphylococcus aureus toxins represent a public health challenge all over the world. This study aims to analyze the prevalence of genes encoding the staphylococcal leukocidins and their correlation with antimicrobial susceptibility and the source of isolation. For this purpose, the susceptibility of 75 S. aureus isolates to 12 antimicrobial agents was investigated. The leukocidins genes (lukD, lukE, lukF and lukS) were detected by polymerase chain reaction (PCR). The ability to express these genes was assessed among 20 isolates by RT-PCR. The most prevalent luk genes were lukF gene (73.3%), followed by lukE (64%), lukD (44%) and lukS (34.7%). Expression of lukD, lukE and lukS genes were variable. lukF gene was not expressed by any of the tested isolates. A statistically significant association was found between lukF occurrence and burn isolates. Besides that, lukF gene was more prevalent among amoxicillin-clavulenic acid and amikacin resistant isolates, while lukE was predominant with gentamicin resistant isolates. High expression level of lukD was found in MRSA and MDR isolates. Key words: Staphylococcus aureus, leukocidins, antimicrobial sensitivity.
Highlights
Staphylococcus aureus is one of the important human pathogens that causes wide varieties of diseases, ranging from skin infection to bacteraemia and infective endocarditis, beside toxin-mediated diseases (Lowy, 1998)
A significant association was found between methicillin resistant S. aureus (MRSA) and multidrug resistant (MDR) isolates
These results demonstrate high prevalence of luk genes including Panton-Valentine leukocidin (PVL) genes among S. aureus isolates
Summary
Staphylococcus aureus is one of the important human pathogens that causes wide varieties of diseases, ranging from skin infection to bacteraemia and infective endocarditis, beside toxin-mediated diseases (Lowy, 1998). More than 30 extracellular products are produced by S. aureus (Rogolsky, 1979). Almost all strains secrete a group of cytotoxins and enzymes such as nucleases, haemolysins, lipases, collagenases, proteases and hyaluronidase. Some strains produce additional exoproteins, which include leukocidins, toxic shock syndrome toxin (TSST-1), the exfoliative toxins and the staphylococcal enterotoxins. Leukocidins and γhaemolysin are members of a toxin family known as synergohymenotropic toxins, as they act by the synergy of two proteins to form a pore on cell membranes (Dinges et al, 2000). Γ-Hemolysins (Hlg) and leukocidins (Luk) consist of two classes: F class (molecular weight of about 34 kDa).
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