Cell free preparations of probiotics exerted antibacterial and antibiofilm activities against multidrug resistant E. coli

Abdelhamid, Ahmed G.; Esaam, Aliaa; Hazaa, Mahmoud M.

The emergence of multidrug-resistant E. coli has been increasingly reported (Paterson and Bonomo, 2005) . Nearly, 63% of total E. coli isolates in many countries were able to produce extendedspectrum beta-lactamase and the majority belonged to E. coli isolated from the ICU patients (Magiorakos et al., 2012; Nakai et al., 2016) . In this work, all E. coli isolates were resistant to at least six antibiotics of different classes. Multidrug resistance of clinical pathogens imposes a rising threat to the human health by increasing the disease burden and spread. In previous studies, the resistance of E. coli to multiple drugs such as co-trimoxazole, penicillin and nitrofurantoin was at high frequencies (Mubita et al., 2008) . High resistance rates of 60.6% of E. coli strains to cefazolin, tetracycline, ampicillin and trimethoprim/sulfamethoxazole was reported by (Li et al., 2017) . The continuous emergence of multidrug resistance and even resistance to antibiotics of the last resort led to developing alternative intervention strategies to combat bacteria pathogenesis. Probiotics have received a growing interest in the prevention and treatment of infectious and other human diseases such as gastrointestinal, urogenital, respiratory and even periodontal diseases (Vuotto et al., 2014) . In this work, cell-free preparations of different probiotics belong to Lactobacillus and Bifidobacterium species were able to reduce the growth of drug-resistant E. coli when investigated using agar well diffusion method. In other words, the inhibitory activity of seleniumenriched probiotics against pathogenic E. coli under in vitro and in vivo conditions was well-documented (Yang et al., 2009 ). In addition, probiotics isolated from yoghurts exhibited antibacterial effects against some common pathogens including E. coli (Kaboosi, 2011) . Moreover, fifteen strains of probiotics belonging to many genera among which Lactobacillus and Bifidobacterium had antibacterial properties against gram negative and gram positive bacteria (Tejero-Sariñena et al., 2013) . In the same cell, free supernatants of probiotics were used and the evidence of antibacterial properties was due to produced organic acids lowering the pH. In addition, bioactive compounds released by probiotics such as bacteriocins and hydrogen peroxide were responsible for their antimicrobial properties (Drider et al., 2016; Noordiana et al., 2013; Yang et al., 2014) . These results support the potential use of probiotics/their bioactive compounds as antimicrobials against multidrugresistant pathogens such as E. coli.