&i&In Vitro&/i& Quantitative Assessment of Some Virulence Factors Produced by &i&Escherichia coli&/i& in Different pH, Temperature and Oxygen Conditions

摘要

Background: Bacteria virulence is modulated by different factors in the gut and other host environments. Aim: This study was to quantitatively determine some virulence factors produced in Escherichia coli when exposed to different conditions. Method: The different conditions of temperature and pH were used. The growth response and biofilm production of E. coli in these conditions was quantified. The production of secretory molecules was analyzed using the thin layer chromatography (TLC) method. The isolates exposed to these conditions were analyzed for antibiotic susceptibility using the disk diffusion method. Results: For the acidic condition, the comparisons of the growth in the other temperatures were lower than the neutral pH and significant results were noted in 25°C (P = 0.0036), 4°C (P = 0.0006) and -5°C (P = 0.0011), while non-significant result was seen in 37°C (P = 0.2453). In the alkaline condition, at 37°C the degree of significance was P = 0.0102, 25°C (P = 0.0007), 4°C (P = 0.0009), and at -5°C (P = 0.0006). The formation of biofilm, when compared to the normal body temperature of 37°C, was significantly higher at 4°C (P = 0.0382). TLC showed production of bands at -5°C, (Rf = 0.5), at 25°C two bands in both the acidic and alkaline condition (Rf = 0.4) and at 37°C, two bands were seen: one in the acidic condition with an Rf of 0.6 and 0.5 in the alkaline condition. Antibiotic susceptibility testing showed varying zones of susceptibility and resistance in the different conditions to the antibiotics used. In the temperature condition, the isolates became resistant to Cefotaxime (CTX) and ColistinSulphate (CT) at -5°C, Ceftolozane/Tazobactam (CT) at 4°C, Cefotaxime (CTX) at 25°C, and at 37°C, it was resistant to Ceftolozane/Tazobactam (CT). Resistance was also seen in the pH condition of Cefotaxime (CTX) in the alkaline condition. Conclusion: Exposure to these different conditions shows an increase in growth, biofilm, antibiotic resistance, and susceptibility in some conditions which indicates that these conditions promote virulence. The results in the study showed that different conditions of temperature and pH induce some virulence factors such as growth and biofilm. Different secretory proteins were found in different treatment conditions. These observations could be responsible for the resistance to some antibiotics seen in this study.