Emerging Gram-negative bacteria: pathogenic or innocent bystanders

The current review examines the current literature around 'emerging' Gram-negative bacteria other than Pseudomonas aeruginosa in cystic fibrosis (CF), paying particular focus on the recent literature for those that are more frequently encountered: Pandoraea, Achromobacter, Ralstonia and Stenotrophomonas species.

The recent literature is evolving our understanding of the clinical consequences of infection with an 'emerging' Gram-negative bacteria in CF. There is an increase in reported prevalence for many species. They are commonly isolated from patients who already have low baseline lung function. Initial infection can lead to chronic carriage, often with evidence of an associated host immune response and subsequent clinical deterioration. For some species occasional cases of bacteraemia have been reported.

There are a number of Gram-negative organisms, other than P. aeruginosa, that can cause chronic infection in patients with CF. There is data to suggest that some of these so-called emerging Gram-negative bacteria are increasing in prevalence and can be pathogenic in patients with CF. The prevalence and clinical consequences however differ from species to species. There is a pressing need to agree a definition of chronic infection for these organisms to compare data between studies.