Environmental regulation of biofilm formation in intensive care unit isolates of Staphylococcus epidermidis

• Published in: The Journal of hospital infection Vol. 52; no. 3; pp. 212 - 218
• Main Authors: Fitzpatrick, F., Humphreys, H., Smyth, E., Kennedy, C.A., O'Gara, J.P.
• Format: Journal Article
• Language: English
• Published: Kent Elsevier Ltd 01.11.2002; Elsevier
• Subjects: Bacterial diseases; Biofilm formation, ica operon, environmental regulation, clinical isolates; Biofilms - growth & development; Biological and medical sciences; Cross Infection - etiology; Cross Infection - prevention & control; DNA, Bacterial - analysis; DNA, Bacterial - genetics; Equipment Contamination - prevention & control; Equipment Contamination - statistics & numerical data; Hospitals, Teaching; Human bacterial diseases; Humans; Infection Control; Infectious diseases; Intensive Care Units; Ireland; Medical sciences; Methicillin Resistance - genetics; Operon - genetics; Polymerase Chain Reaction; Polysaccharides, Bacterial - genetics; Prospective Studies; Staphylococcal Infections - etiology; Staphylococcal Infections - prevention & control; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus epidermidis - genetics; Staphylococcus epidermidis - growth & development; Ireland; Biofilm formation, ica operon, environmental regulation, clinical isolates; Nosocomial infection; Biofilm formation; clinical isolates; Intensive care unit; environmental regulation; Infection; Pathogenicity; Microbiological investigation; Staphylococcus epidermidis; ica operon; Bacteriosis; Biofilm; Bacteria; Micrococcales; Environment; Micrococcaceae; Staphylococcal infection; Formation; Clinical isolate
• ISSN: 0195-6701; 1532-2939
• DOI: 10.1053/jhin.2002.1309

Staphylococcus epidermidis is a common cause of prosthetic device-related infection in the intensive care unit (ICU). The environmentally regulated ica operon encodes a polysaccharide adhesin which is a key virulence determinant in the development of S. epidermidis biofilms. To evaluate the capacity of ICU S. epidermidis isolates to form biofilm, we measured biofilm production by 18 isolates associated with device-related infection and 20 contaminating isolates that were not associated with clinically diagnosed infection. Biofilm assays were performed in brain–heart infusion (BHI) medium and in BHI supplemented with salt, ethanol or subinhibitory tetracycline, all of which have the potential to promote biofilm formation. Polymerase chain reaction (PCR) was used to screen for the presence of the ica genes. A significant proportion of S. epidermidis strains associated with device-related infections (89%) were found to contain the ica locus compared with 50% of contaminating isolates ( P=0.01). However only four of 26 (15.3%) of all ica -positive isolates were biofilm-positive when grown in BHI medium, indicating that no significant association existed between the presence of the ica locus and biofilm-forming capacity, under standard growth conditions. In contrast the number of ica -positive isolates that were biofilm-positive under stress-inducing growth conditions or in the presence of subinhibitory tetracycline increased significantly to 73% ( P=0.02). These findings suggest that the presence of the ica locus alone is not sufficient for biofilm formation and that regulation of biofilm formation under altered growth conditions, which may exist in the in vivo environment, also plays a possible role in the pathogenesis of biomaterial-related S. epidermidis infections.