The effect of the mecA gene and its mutant form on the response of S. aureus to the most common antibiotics

Abstract

Staphylococcus aureus isolates were collected from different hospitals in the Alexandria governorate in Egypt. The 100 isolates were subjected to fingerprinting based on their resistance/susceptibility to antibiotics which are commonly used in Egypt and all over the world. About 54% of the isolates showed multidrug resistance. The Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) was used to study the relationship between the examined isolates. Four arbitrary primers were used in this study and the results revealed that approximately 54 different banding patterns were obtained, dividing the isolates into five different groups. The PCR was performed for the detection of the mecA gene in all the isolates (susceptible and resistant). The mecA gene was detected in all the resistant isolates and in only one susceptible isolate (AS38). The mecA gene from the AS38 strain (Methicillin-Susceptible S. aureus or MSSA) and another one from a resistant strain (Methicillin-Resistant S. aureus or MRSA) were subjected to DNA sequencing. The sequence alignment showed that a point mutation was carried out in the nucleotide 215 (T substituted by A), which leads to the conversion of the amino acid asparagine into isoleucine. Phylogenetic analysis was carried out to study the evolution of such genes between different S. aureus strains. Also, the data revealed that there is a contentious modification for such genes.