Comparative Metabolic Characterization of Extraintestinal Pathogenic Blood Isolates from Saudi Arabia.

BACKGROUND

The prevalence of bloodstream infections caused by extraintestinal pathogenic (ExPEC) has increased substantially. E. ST131 is one of the dominant ExPEC clones among E. bacteremia population. Metabolism can trigger the pathogenesis of some bacterial isolates, and here we evaluated and compared the metabolic traits of E. bacteremia isolates including -lactamase (BL)/extended-spectrum -lactamase (ESBL)-positive and ESBL-negative isolates and ST131 and non-ST131 isolates.

METHODS

The metabolic profiles of thirty E. isolates, obtained from blood samples for hospitalized individuals at a tertiary healthcare facility in Riyadh, were determined using HiMedia carbohydrate test strips. The difference in the utilization ability between isolate groups was then statistically assessed.

RESULTS

Our data found that non-BL/ESBL producers were of low metabolic capacity compared with ESBL-positive isolates although the difference remained insignificant. Higher levels of utilization for some carbohydrates, such as fructose and trehalose, were detected among ST131 isolates when compared with non-ST131, and ST131 was also significantly associated with metabolizing rhamnose. The mean bio-score of both isolate groups was insignificant. We showed no link between metabolism and antimicrobial susceptibility profiles among tested blood isolates.

CONCLUSION

ST131 blood isolates were slightly higher in their carbohydrate utilization activity than non-ST131. More importantly, ST131 isolates were significantly capable of metabolizing rhamnose. Future research should focus on the factors that might drive the success of major ExPEC clones such as ST131.