Epidemiology of healthcare-associated Stenotrophomonas maltophilia infections in CF and in ICU patients: role of biofilm formation

Abstract number: P1436

Cipresso R., Barchitta M., Marzagalli R., Di Bonaventura G., Pompilio A., Gherardi G., Agodi A.

Objectives:Stenotrophomonas maltophilia is an emerging bacterial pathogen which is currently isolated with increasing frequency from the airways of cystic fibrosis (CF) patients as well as from different sites of intensive care units (ICU) patients. In a previous study S. maltophilia strains isolated from the airways of independent CF patients, have been characterised for the expression of several virulence-associated factors. The present study was designed in order to: (i) investigate the clonality, the mode of transmission and the patients' risk profile for acquisition of S. maltophilia in CF and ICU patients, and (ii) to evaluate the epidemiological significance of biofilm formation both in CF-associated and in ICU-associated strains.

Methods: Patterns of S. maltophilia acquisition in the ICU during the period of the survey were carriage, colonisation and infection (ventilator-associated pneumonia, urinary tract infection, bloodstream infection, catheter related infection), characterised using well established definitions. Clonality assessment was performed by PFGE of genomic DNA digested with 25 U/ml of XbaI. Macrorestriction fragments were separated using a CHEF-DR III apparatus and genomic relatedness performed using Tenover criteria. Cross-transmission was assumed when two patients had indistinguishable isolates. Biofilm formation was assessed by crystal violet staining in polystyrene 96-well microtiter plates after 24 h of incubation at 37°C.

Results: A total of 42 CF-associated isolates and of 38 ICU-associated isolates were subjected to macrorestriction analysis. A total of 32 different PFGE profiles were observed among CF isolates. Twelve distinct clones were identified among the ICU isolates, six associated with cross-transmission of infection and/or colonisation; a major clone (named clone A) was responsible for the epidemic spread of S. maltophilia. Notably, the degree of biofilm formation was shown to be significantly higher in ICU strains than in CF strains (p < 0.05).

Conclusion: Health care-related infections are associated with high attributable mortality. S. maltophilia is an important alert organism increasingly isolated both in CF and in ICU patients: increasing levels of antibiotic resistance and the ability to form biofilms surrounding invasive devices pose special challenges to be addressed for appropriate control strategies.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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