Different Factors Associated with CTX-M-Producing ST131 and Non-ST131 Escherichia coli Clinical Isolates

OBJECTIVES: To determine factors associated with CTX-M-producing ST131 Escherichia coli which is the worldwide predominant lineage among CTX-M-producing E. coli isolates. METHODS: Consecutive inpatients with a clinical sample positive for CTX-M-producing E. coli and considered as cases in a previous 8-month (2008–2009) case-control study performed in ten university hospitals in the Paris area were included in the present sub-population study. Patients with a CTX-M-producing ST131 E. coli clinical isolate were compared with those with a CTX-M-producing non-ST131 E. coli clinical isolate with regard to 66 variables. Variables were first compared using univariate logistic regression, then a multivariate analysis using a backward selection with variables with p-value <0.1 in univariate analysis was carried out. RESULTS: Fifty-five patients with a CTX-M-producing ST131 E. coli clinical isolate were compared to 97 patients with a CTX-producing non-ST131 E. coli clinical isolate. Multivariate analysis showed that only previous residence in long term care facilities (OR = 4.4; 95% CI = 1.3–14.7) was positively associated with a CTX-M-producing ST131 E. coli isolate. However, it also showed that regular consumption of poultry products (OR = 0.2; 95% CI = 0.1–0.6), having had at least one device in the preceding 6 months (OR = 0.3; 95% CI = 0.1–0.7) and stay in ICU (OR = 0.2; 95% CI = 0.05–0.8) were negatively associated with isolation of CTX-M-producing ST131 E. coli from clinical samples. CONCLUSIONS: This study provides more insight into the epidemiological features of ST131 and non-ST131 E. coli producing CTX-M enzymes. It shows, for the first time, that isolation of CTX-M-producing ST131 E. coli from clinical samples is not linked to consumption of various foods and confirms that residence in long term care facilities is a predictor of these isolates.