Different Responses of ESBL Indicative Peptide Spectra to Various β- Lactam Exposures Among Community Acquired Urinary Tract Infected Escherichia coli by Using the MALDI-TOF Technique

Abstract The study aims to identify Escherichia coli specific and Extended Spectrum β- Lactamase (ESBL) indicative peptide spectra when co-exposed with ceftazidime or other beta-lactams with clavulanic acid in ESBL producing isolates in community acquired urinary tract infected E. coli by Matrix-Assisted Laser Desorption/Ionization Time - of - Flight Mass Spectrometry (MALDI-TOF) technique. Among 100 tested E. coli isolates, 13 antibiotics were used to profile the resistant isolates. They were mainly demonstrated the resistance to ampicillin, cefoxitin, cefotaxime, ceftazidime, amoxicillin/clavulanic acid, and tetracycline. The high-, low-, and non-ESBL producers, 43.86%, 40.35% and 15.79%, were classified from these resistant isolates according to the ratio of MIC fold between ceftazidime and amoxicillin/clavulanic acid by E-test. Using the MALDI-TOF technique, 5 E. coli -specific peptide spectra were identified which were located at 4362, 4531, 5380, 6254, and 9063 Da using a cut-off value of 60% of frequency. The significant intensity reduction of spectra at 10477, and 5096 Da were recorded and suspected as ESBL indicative peptide spectra after the exposure to ceftazidime or cefotaxime alone and concomitantly with amoxicillin/clavulanic acid in the high and low ESBL producers, respectively. The further significant spectra located at 2548, and 8371 and 9713 Da were exclusively related to ceftazidime hydrolysis in the low and high ESBL producers, respectively. There were 3 and 4 significant peptide spectra which were located at 5968, 7153, 9713 and 10477 Da, and 2548, 5096, and 9537 Da were also suspected as being ESBL spectra after exposure to other tested β-lactams in the high and low-ESBL producers, respectively. Keywords: Extended Spectrum β-Lactamase; E. coli; MALDI-TOF, Peptide spectra; β-lactams