Different factors associated with CTX-M-producing ST131 and non-ST131 Escherichia coli clinical isolates

To determine factors associated with CTX-M-producing ST131 Escherichia coli which is the worldwide predominant lineage among CTX-M-producing E. coli isolates.

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.

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.

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.