Background Pseudomonas aeruginosa infection in patients with cystic fibrosis causes destructive lung disease, reduced quality of life and a poorer prognosis. Eradication of early P aeruginosa infection is possible, but not once chronic infection is established. P aeruginosa gains much of its pathogenicity through the production of virulence factors and biofilm formation. The expression of these is co-ordinated by intercellular signalling (quorum sensing, QS). QS inhibition with garlic has not previously been demonstrated with clinical strains.

Aim The authors aimed to determine the in vitro efficacy of a garlic supplement upon the inhibition of QS in clinical strains of P aeruginosa.

Methods A laboratory strain of P aeruginosa (PA01) and clinical isolates obtained from the sputa of five children with cystic fibrosis were tagged chromosomically using chromosomal transcriptional lux-based fusions (CTX::lux) to the QS controlled genes pqsA and lasB to evaluate the impact of garlic on these genes. Isolates were grown in control LB or LB media infused with garlic oil. Growth and bioluminescence from the transcriptional fusions were measured using an automated microplate reader. The difference in expression between the two groups was calculated accompanied by a 95% CI.

Results The garlic preparation reduced expression of lasB and pqsA in all strains examined.

Conclusion Macerated garlic oil reduces the expression of two genes which represent major loci of control of quorum sensing, the process by which P aeruginosa regulates its virulence. This is promising and further advances the potential for translation as a therapeutic candidate.