A symmetrical azomethine ligand L was synthesised from a reaction of m-phenylenediamine and o-vanillin in 1:2 molar ratio. Dinuclear complexes of Zn2L2 and Co2L2 have been successfully isolated and characterised through 1H NMR, IR and magnetic moment. The x-ray crystal structure of Zn2L2 showed that the two Zn(II) nuclei were coordinated to two L moieties through the phenolic oxygen and imine nitrogen atoms, forming a slightly distorted tetrahedral geometry around the Zn(II) centres. When coordinated to metal centres, the signature n(C=N) of Lat 1616 cm-1 experienced a shift towards lower wave numbers of 1573-1613 cm-1. The Zn(II) complex was diamagnetic whereas the Co2L2 complex was paramagnetic with 3 unpaired electrons having µeff = 4.07 B.M. An antibacterial screening against methicillin resistant Staphylococcus aureus (MRSA) revealed that the activity of the complexes was more pronounced than that of the uncoordinated L. The complex Zn2L2 revealed the lowest MIC value of 0.56 µg/µl MIC, indicating that it was a better bactericides than Co2L2 and L, in that order.
Efflux-mediated resistance has been recognized as an important contributor of antibiotic resistance in bacteria, especially in methicillin-resistant Staphylococcus aureus (MRSA) isolates. This study was carried out to detect and analyze efflux genes (norA and mdeA) and active efflux activity in a collection of Malaysian MRSA and methicillin-sensitive S. aureus (MSSA) clinical isolates. Nineteen isolates including three ATCC S. aureus reference strains were subjected to PCR detection and DNA sequence analysis for norA and mdeA and active efflux detection using modified minimum inhibitory concentration (MIC) assay. From the 19 isolates, 18 isolates harboured the mdeA gene while 16 isolates contained norA gene. DNA sequence analysis reveals 98-100% correlation between the PCR product and the published DNA sequences in GenBank. In addition, 16 isolates exhibited active efflux activity using the ethidium bromide (EtBr)-reserpine combination MIC assay. To our knowledge, this is the first report on the detection of efflux genes and active efflux activity amongst Malaysian clinical isolates of MRSA/MSSA. Detection of active efflux activity may explain the previous report on efflux-mediated drug resistance profile amongst the local clinical isolates.