The Decrease in Spectrum Intensity of ESBL Spectra after Exposure to Clavulanic Acid in Nosocomial Urinary Tract Infected Escherichia coli Analysed by VITEK® MS

Abstract The present study aimed to investigate the influence of clavulanic acid on the spectrum intensity of Extended Spectrum β- Lactamase (ESBL) indicative spectra in the nosocomial urinary tract infected Escherichia coli. Two hundred nosocomial urinary tract infected E. coli isolates collected between 2017-2019 were recruited. Their antibiotic susceptibilities and ESBL productions were then determined. The effect of clavulanic acid contained in amoxicillin-clavulanic acid towards the change of spectra intensity after being exposed was also determined to identify their ESBL indicative spectra. Results revealed that these nosocomial isolates exhibited a low percent resistance after being tested to piperacillin-tazobactam, meropenem, doripenem, and gentamicin. VITEK® MS analysis demonstrated five E. coli species-specific spectra including 4363, 5097, 5381, 6255, and 9065 Dalton. After exposure to ceftazidime alone, and co-exposure to ceftazidime and amoxicillin-clavulanic acid, six ceftazidime-susceptible, and five ceftazidime-stress spectra, 5381, 6412, 7870, 8876,10139 and 10301 Dalton and 3578, 6226, 6316, 7274, and 8370 Dalton were significantly detected, respectively. Whereas two ceftazidime-resistant spectra, 4613 and 9715 Dalton, exhibited a significantly decreased intensity after determined in the high ESBL producing group after co-exposure to ceftazidime and clavulanic acid, respectively. In conclusion, an ESBL inhibitor or clavulanic acid could significantly decrease the spectrum intensity of two spectra 4613 and 9715 Dalton after being co-exposed to ceftazidime and clavulanic acid and these spectra were suspected as ESBL indicative spectra in the high ESBL producing nosocomial E. coli isolates. Keywords: Extended spectrum β- Lactamase indicative spectra, clavulanic acid exposure, nosocomial urinary tract infection, Escherichia coli, VITEK® MS