Phenotypic and Genotypic Evaluation of Biofilm Formation and Antibiotic Susceptibility Pattern of Uncommon Microorganisms Obtained from Urinary Catheters of Patients Hospitalized in two Referral Hospitals in Tehran

Background and Objectives: Indwelling urinary catheters significantly increase the risk of urinary tract infection (UTI)among hospitalized patients, mostly due to biofilm formation by a combination of either common or uncommon uropathogens.Uncommon microorganisms are increasingly becomingresistant to currently available antibiotics, which makes them important reservoirs for resistance to antibiotics. Their phenotypic (intensity) and genotypic (responsible genes) patterns of biofilm formation vary in every single isolate.Meanwhile, updating theknowledge about their antibiotic resistance pattern is important for modifying the drugs of choice forearly empirical therapy.This study was conducted to characterize different biofilm formation and antibiotic resistance patterns of uncommon isolatesrecovered from urinary catheters of hospitalized patients. Materials and Methods: This prospective analysis was carried out over a period of 18 months from the catheters of the patients withno primarysymptoms of UTI who were hospitalized in either Imam orLoghman hospitals in Tehran, Iran. All the isolates werecharacterized first. They were then subjected to the biofilm formation assay using microtiter plate method and their antibiotic susceptibilitypatterns were determined by disk diffusion method. The presence of the biofilm formation related genes was examined by PCR assay. Results: Fifty isolates obtained from 50 patients (26 females, 24 males). As usual, Gram-negative bacteria were the most common strains (62%), followed by Gram-positive bacteria (24%) and fungi (14%). Therefore, the focus of study was on the Candida species (14%) and comparing their biofilm strength with others.Eighty five percent of these species form strong biofilms, while only 15% of them form biofilms moderately, and none of them produced weak biofilm. Meanwhile, 82% of the isolates hadAls1&Brc1biofilmgenes. In comparison, 26% of the Gram-positive and 13% of the Gram-negative bacteria form biofilms strongly, while most of them form moderate biofilms (67% of Gram-negative and 41% of Gram-positive bacteria). Finally, 1/3 of Gram-positive and 1/5 of Gram-negative bacteria produce biofilms weakly. Moreover, antibiotic resistance to piperacillin-tazobactam, ciprofloxacin, imipenem, ampicillin-sulbactamand trimethoprim-sulfamethoxazole was seen among Candida species, and 64% of these fungi weremultidrug resistant. Conclusion: It seems that although some species like Candida are uncommon on urinary catheters and, therefore,are not among common causes of catheter-associated UTI, they should be considered as important because of their stronger biofilm formation ability and their antibiotic resistance patterns.