Resistance to Aminoglycosides among Biofilm Producing Escherichia coli Strains Isolated from Patients with Urinary Tract Infection in Isfahan during 2017

Backgroun and

Urinary tract infections (UTIs) are known as a worldwide serious challenge, mainly because of higher recurrence rates due to the ability of strains to form biofilm which results in resistance to frontline antibiotics such as aminoglycosides. Aminoglycosides are broad-spectrum antibiotics that show appropriate bactericidal activity against most Gram-negative bacteria such as uropathogeneic Escherichia coli (UPEC). In this study we aimed to assess the antibiotic resistance patterns of biofilm producing UPEC strains isolated from patients with UTI in a referral hospital in Isfahan.

During 2017, a total of 166 Uropathogenic UPEC strains were collected from a referral hospital laboratory in Isfahan. All isolates were cultured on MacConkey agar and eosin methylene blue agar and identified using Polymerase Chain Reaction (PCR) assay. The ability of strains to form biofilm was tested by quantitative microtiter plate (MTP) assay and susceptibility of biofilm-producing strains to amikacin, gentamycin, kanamycin, streptomycin, and tobramycin was determined using disk diffusion method according to the recommendations of Clinical & Laboratory Standards Institute (CLSI).

Using phenotypic methods & PCR test all isolates were confirmed as E. coli in which 39 strains (23%) were biofilm positive; and among all, 18, 26 and 56% of UPEC strains were able to form strong, moderate, and weak biofilm, respectively. Moreover, 28% of biofilm producing strains showed susceptibility to all antibiotics tested and 72% were resistant to streptomycin. Moreover, resistance to kanamycin and amikacin was also limited to 36 and 10% of strains, resptecively. A total of 7 resistance patterns were determined among the strains in which pattern 1 (resistance to streptomycin) was the most prevalent pattern.

The results of this study indicated the presence and persistence of aminoglycoside resistant and biofilm producing UPEC strains among patients with UTI in the studied hospital in Isfahan. Also, tobramycin and gentamicin were selected as the the most effective antiobiotcs against biofilm producing strains in this research.