Michael John Howard Goldsworthy

Catheter-associated urinary tract infections (CAUTI) have frequently been studied in monocultures in vitro. However, many CAUTI are due to the presence of a mixed microbial community and not just a single population, especially within patients subjected to long-term catheterization. This can potentially have important clinical implications in regards to treatment strategy and outcome. This study revealed that when Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) (both commonly found in CAUTI) were grown together as a mixed culture within a CAUTI model in comparison to their respective monocultures, accelerated biofilm development was observed. Virulence gene expression analysis within P. aeruginosa and MRSA monoculture and mixed biofilms was performed through use of real-time quantitative PCR. It was revealed that production of P. aeruginosa exotoxin A was increased 1839-fold when P. aeruginosa and MRSA were grown together as a mixed biofilm. Significant expression of α-haemolysin by MRSA was not observed in either culture. It is proposed that both the biofilm-forming capability and virulence gene expression of microbes within CAUTI mixed biofilms may differ substantially to the respective microbial monocultures. This highlights the importance of developing specific treatment strategies for CAUTI when polymicrobial communities are present.