Marine bug tames pathogen
doi:10.1038/nindia.2012.72 Published online 15 May 2012
New research has shown that bacteria isolated from coral could inhibit the virulence of drug-resistant Serratia marcescens, a rod-shaped bacteria responsible for severe urinary tract infections in hospitalized people. These coral-harvested bacteria could yield novel drug candidates for coping with the virulence of S. marcescens.
S. marcescens causes sepsis, meningitis, urinary tract infections, osteomyelitis and ocular infections. The bacterium turns virulent by growing 'biofilms' that make it resistant to common antibacterial agents. Researchers began to focus on a new drug target called quorum sensing (QS), a cell-to-cell communication system that makes such bacteria virulent through drug-resistant biofilms.
To explore the potential for novel anti-QS and anti-biofilm agents, the researchers collected reef-building coral (Acropora digitifera) from the Gulf of Mannar in South India. They isolated 41 bacterial isolates (coral-associated bacteria; CAB) from the mucus of the coral. They then investigated the anti-QS activity of each bacterium by exposing it to Chromobacterium violaceum, bacteria that affect humans through contaminated water or seafood.
Of these CAB, eight exhibited anti-QS properties. The researchers explored their anti-QS and anti-biofilm properties with S. marcescens. By growing biofilms on glass surfaces, they studied the effect of the CAB on biofilm formation. CAB-23 and CAB-41 showed the most anti-QS and anti-biofilm properties.
Besides biofilm formation, QS regulates various virulence factors such as swimming motility, swarming and the production of biosurfactants and a pigment called prodigiosin. The study found that CAB-23 and CAB-41 both significantly inhibited the swarming motility and production of prodigiosin.
"CAB-23 and CAB-41 — identified as Delftia tsuruhatensis and Stenotrophomonas maltophilia by gene sequencing — could yield novel anti-pathogenic agents," says lead researcher S. K. Pandian.