Aim:This study aimed at characterizing the biofilm-forming ability of drug-resistant and sensitive Escherichia coli under in vitro gut conditions and in the presence of ciprofloxacin. Methods and Results: 153 E. coli isolates comprising 80 from clinical and 73 from environment source were studied for their ability to form biofilm under control and in vitro simulated gut conditions. The integrity of preformed biofilm on exposure to ciprofloxacin was assessed. Expression of biofilm-associated genes was analysed using qPCR. A high degree of resistance was observed in clinical isolates with a concomitant prevalence of bla TEM . Bile, pH and low temperature enabled the E. coli biofilm to resist the effect of ciprofloxacin. Clinical isolates of E. coli formed strong biofilms in in vitro gut conditions following exposure to high concentration of ciprofloxacin. The expression of biofilm genes varied between different gut conditions viz., presence of bile, pH and low temperature, included in this study. Conclusions:This study demonstrates the importance of papC and csgA for maintaining the biofilm integrity upon antibiotic exposure. Escherichia coli form biofilm as a survival strategy to adapt to the conditions in their environment irrespective of their drug resistance status. Significance and Impact of the Study:The study provides an understanding of the effect of different parameters of the gut conditions during infection and the effect of antibiotic on survival and biofilm-forming ability of clinical and environmental E. coli isolates. It further suggests that bacteria resort to biofilm formation as one of the mechanisms to adjust to alterations in gut conditions and once the biofilm is formed, it requires high concentration of ciprofloxacin to eradicate it.

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Salmonella is one among the most versatile and resilient enteric pathogens that known to have developed various survival strategies within the host system. The ability of the bacteria to circumvent the physiological parameters as well as dodge the antimicrobial stress environment within the host is one of the most crucial steps in establishing an infection. With an alarming rise in multi-drug resistant serovars of non-typhoidal Salmonella and lack of vaccine for combatting the infections, behaviour of the bacteria in the presence of host physiological gut conditions (NaCl, high and low iron) and antibiotics will help in understanding the survival strategies as well as mechanisms of resistance. 59 non-typhoidal Salmonella serovars isolated from poultry and seafood were used in the study. The isolates were screened for their antibiotic susceptibility patterns. Two multi-drug resistant and two sensitive serovars were used for growth kinetics and virulence gene expression study. The results obtained revealed that despite similar resistance pattern, the effect of individual class of antibiotics on the growth of serovars varied. On contrary, no significant difference was observed in growth pattern on exposure to in vitro gut like experimental conditions. Nevertheless, the in-vitro gut conditions and exposure to antibiotics have drastically reduced the minimum inhibitory concentration of antibiotics in resistant strains. A first of its kind study that draws attention on the significant effect of antibiotics and gut physiological conditions on MIC and expression of virulence genes from Salmonella pathogenicity island (SPI) 1 and 2 between resistant and sensitive non typhoidal Salmonella serovars.