Document Type : Original Article


1 Department of Electron Microscopy, Theodor Bilharz Research Institute, Giza, Egypt.

2 Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Egypt.

3 Faculty of Medicine, Juba University, Sudan.


Biofilm formation on indwelling urinary catheters is a leading cause of Urinary tract infection (UTI). Presence of biofilm is associated with increased bacterial resistance to antimicrobial therapy and resultant treatment failure. The study detected a reliable method for diagnosis of biofilm formation by comparing scanning electron microscopy (SEM) and tissue culture plate method (TCP). The work was conducted on 20 urinary catheters from patients ranging from 1.5 to 85 years with catheters that remained in situ for a period of 3 to 20 days. Samples of catheters for culture and SEM and samples of urine were taken at the same time. The correlation between renal conditions and biofilm formation was not significant (p=0.336). No significant correlation (p =0.836, 0.163 respectively) was found between predisposing conditions (DM, renal insufficiency, diarrhea and impaired immunity) and development of Catheter associated urinary tract infection ( CAUTI )and biofilm formation. Biofilm formation increased with duration of catheter in situ, but no significant correlation was found (p=0.095). This could be due to small number of specimens. 9/20(45%) urine samples, 12/20(60%) catheter samples were positive by culture and 14/20(70%) catheters showed biofilm on SEM. 4/12(33.33%) organisms isolated
from catheter culture produced biofilm by TCP method. 9 isolates were recovered from 9 positive urine cultures. The microorganisms isolated were non Candida albicans (3/9), E. coli (2/9), C. albicans (2/9) and Acenitobacter (2/9). 14 isolates were recovered from 12 culturepositive catheters. The organisms isolated were E. coli (3/14), non-Candida albicans (3/14), C. albicans (2/14), C tropicalis (2/14), Acenitobacter (2/14), Klebsiella (1/14) and Enterococcus
(1/14). Reduction in microbial diversity with antimicrobial use was noticed but the correlation was insignificant (p=0.317). The correlation between urine culture results as well as catheter culture results and biofilm formation by SEM were both significant (p = 0.008 & 0.000 respectively). The correlation between urine culture and TCP assay was insignificant (p =0.237). Using SEM as the gold standard method for the detection of biofilm, the sensitivity, specificity, total accuracy, PPV & NPV of urine culture and catheter culture were, 64.30%, 100%, 75%, 100%, 54% & 85.70%, 100%, 90%, 100%, 75% respectively.