Clavulanic Acid - Susceptible Peptide Spectra Tested with Agar Disk Diffusion and Epsilometer test of Urinary Tract Infected Escherichia coli Isolated from the Community-Acquired Infection

Abstract The present study aimed to investigate clavulanic acid susceptible peptide spectra in 174 community-acquired urinary tract infected Escherichia coli isolates using VITEK® MS. They were collected from bacteriuria samples at Diagnostic Laboratory Unit between January and May 2016. One hundred and fourteen multidrug resistant isolates were detected. Among these isolates, 13, 53, and 48 isolates were classified as the non, high, and low ESBL-producers, respectively by using Epsilometer strip test. Spectrum analysis was calculated for investigating the enzyme spectrum. The mass analysis and spectrum identification of ESBL-producing isolates were elucidated using the VITEK® MS apparatus. Among 58 peptide spectra, seven E. coli-specific spectra located at 3126, 3433, 6317, 6411, 7159, 9537, and 10301 Dalton (Da) were commonly detected in ≥ 85% of the total samples. Among the high ESBL-producing isolates, the spectrum intensity of four ceftazidime-resistant spectra which were located at 4613, 5613, 6508, 9713 Da was significantly increased after being exposed to ceftazidime as the ceftazidime-resistant spectra. Using agar disk diffusion, four clavulanic acid-susceptible spectra, 3433, 4613, 4768, and 9713 Da, were significantly detected after being co-exposed to ceftazidime and amoxicillin/clavulanic acid. Interestingly, the spectrum intensity of the significant spectrum, 9713 Da, was decreased after being co-exposed to ceftazidime plus clavulanic acid using an Epsilometer strip test. The interesting peptide spectra at 9713 Da significantly exhibited the clavulanic acid-susceptibility after being co-exposed to ceftazidime and clavulanic acid in both assays and could be suspected to be the ESBL indicative peptide spectra in the high ESBL-producing isolates. Keywords: VITEK® MS, Escherichia coli, ESBL, Clavulanic acid-susceptible peptide spectra, Community-acquired urinary tract infection