Biofilm formation and the presence of intercellular adhesion locus "ica" among staphylococcal from catheter associated infections

ABSTRACT

Catheter infections are most commonly caused by staphylococci, either coagulase negative [CONS] or Staphylococcal aureus [S. aureus]. It has been established that clinical isolates often produce a biofilm, which is involved in adherence to biomaterials and provides enhanced resistance of bacteria against host defences and antibiotic treatment. This study aims to detect the biofilm forming ability of staphylococcal clinical isolates evaluated by Congo red agar plate test [CRA] and spectrophotometer, and to determine the occurrence of the of the icaA and icaD genes for biofilm production by PCR. This study included 50 staphylococcal strains 26 [52%] CONS and 24 [48%] S. aureus isolated from urine catheters, central venous catheters, peripheral venous catheters, collected from 137 catheterized patients attending neonatal, internal medicine and surgical intensive care units [ICUs] and 20 strains, [10 [50%] CONS, 10 [50%]] S. aureus] isolated from skin and nasal swabs collected from 40 healthy volunteers as a control group. The results showed that according to CRA, 14 [53%] CONS and 18 [75%] S. aureus strains were biofilm producers. While quantitative detection showed that 10 [38.4%] CONS and 14 [58.3%]S. aureus were strong biofilm forming, 2 [7.6%] CONS and 4 [16.6%] S. aureus strains were weak biofilm producers, and all strains of control group were non biofilm forming. Both icaA and icaD genes were present in 17 [65.5%] CONS and 19 [79.1%] S. aureus strains, [6 strains were PCR positive and negative with the other two tests] and absent in all strains of the control group. We concluded that CRA, spectrophotometer and PCR are all valid tests and we can use any of them in the diagnosis of catheter associated biofilm formation, the choice depends on the health condition of the patient, PCR is a rapid tool for diagnosis especially because a large number of catheterized patients are critically ill and rapid diagnosis is required