Pathogenic Potentials of Clinical MRSA Isolates from the UK and Nigeria: A Comparative Study

Methicillin-resistant S. aureus (MRSA) are a major problem in both clinical and community settings. They have the potential to produce invasive infections and are now most often multi-resistant. There is an indication that African S. aureus may be more virulent than those from other parts of the world. Thus, the primary aim of this study was to determine if Nigerian MRSA were more virulent than UK MRSA. Polymerase chain reaction characterisation of all the MRSA isolates under study revealed variability in the distribution of virulence factors among the isolates. With the aid of two-dimensional electrophoresis, variation was observed in the intracellular protein profiles of MRSA from the same and different lineages. Antibiogram profiling of the isolates, using antibiotic disc susceptibility and minimum inhibitory concentration assays, showed that higher proportions of Nigerian MRSA were resistant to more antibiotics compared to UK MRSA. An assessment of the levels of interaction between the MRSA isolates with cell lines (KB and A549) showed that no significant differences existed between the means of the levels of interaction (association, invasion) of the UK and Nigerian MRSA with the cell lines. A further investigation of the cytotoxic effects of MRSA on cell lines showed that with just one exception, means of the toxic effects of live Nigerian MRSA, on both cell lines, were significantly greater than those of live UK MRSA on the cell lines, 6 and 24 hrs post-infection. Assessment of the anti-MRSA potential of five novel iron-chelators (iChs) revealed that the iCh with the highest molecular weight had the greatest inhibitory effect on MRSA. Although findings from this work indicate that Nigerian MRSA are more virulent than UK MRSA, more work still needs to be done to conclusively determine if African S. aureus are indeed more virulent than those from other parts of the world.