role of ica operon and biofilm formation in coagulase negative staphylococcal infection

ABSTRACT

Coagulase negative staphylococci are normal skin commensals and are frequently isolated from clinical specimens. CoNS are a major cause of sepsis in the neonatal intensive care unit. The virulence of these bacteria is mainly due to their ability to form biofilms on indwelling medical devices. One important element in this process is the ica operon [intercellular adhesion operon], a gene cluster encoding the production of polysaccharide intercellular adhesion [PIA], which mediates the intercellular adherence of bacteria and the accumulation of multilayer biofilm . This work aimed to evaluate that pathogenic CoNS isolates are more likely to be positive for the ica operon and to produce biofilm than isolates isolated randomly from healthy individuals. Also to compare between antibiotic sensitivity of biofilm producing CoNS isolates and non-biofilm producing CoNS isolates. Finally to detect source of infection in neonatal intensive care unit using biotyping, antibiogram and plasmid profile as epidemiological markers. This study was conducted from April 2010 to April 2011, at Medical Microbiology and Immunology Department, Faculty of Medicine Zagazig University. The study included 40 neonates admitted to NICU, with picture of bacteremia with the mean age 17.43+/- 7.2 days. From them 40 blood samples were taken from peripheral sites and 40 skin swabs were taken from axilla for culture on blood culture bottles and blood agar respectively. 40 age matched healthy neonates as control group and 25 health care workers from NICU to detect source of infection were enrolled in the study. The biofilm production was examined using congo red agar and the presence of genes icaA, icaD were determined by PCR. Biotyping, antibiogram and plasmid profiles were used as epidemiological markers to detect source of infection in NICU. The isolated CoNS were [32.5%, 37.5%, 20% and 24 from blood samples, skin swabs, control and health care workers respectively and the most common isolated organism was S. epidermidis followed by S. haemolyticus then S. hominis. Also the results of qualitative detection of biofilm formation were 69.2%, 33.3% and 33.3% from the studied specimens respectively but all control were non-biofilm forming. The icaA and icaD genes were 76.9%, 40% and 33.3% from studied specimens respectively but both genes were not found in any control isolates. We conclude that the isolates of CONS infections are more likely to be positive for ica operon and health care workers play a role in dissemination of CONS infection in hospital