I recently posted an article on the difference between CPE and CRE, which is neatly illustrated by a prevalence survey from Alder Hey Children’s Hospital in Liverpool. In case you didn’t read my CPE/CRE blog (shame on you), here’s a reminder of the difference between the two:
Carbapenem-resistant Enterobacteriaceae (CRE) – Enterobacteriaceae that are resistant to carbapenems by any mechanism, including the production of an acquired carbapenemase or the production of an ESBL or AmpC combined with porin loss.
Carbapenemase-producing Enterobacteriaceae (CPE) – Enterobacteriaceae that are resistant to carbapenems by means of an acquired carbapenemase.
At Alder Hey, a large children’s hospital in Liverpool, a prevalence survey was performed between September 2011 and August 2012. All clinical and screening specimens were included; rectal screens were collected on admission and weekly from all patients in the ICU and HDU. 24 patients with CRE were identified, five (21%) from clinical specimens and 19 (79%) from rectal screens. The prevalence of CRE in rectal screens was 4.5% (19/421). Four of the 19 patients identified by screening specimens only went on to develop an infection, so 9 (38%) of patients ended up with a CRE cultured from a clinical specimen.
The majority (71%) of the 24 isolates were resistant to carbapenems by AmpC or ESBL combined with impermeability; seven (29%) were CPE, 4 with NDM and three with KPC (Figure). Typing indicated that the 3/4 NDM producing Klebsiella pneumoniae isolates were clonal, and they were clustered in space and time, which may indicate a small outbreak.
Carbapenem-resistance due to the production of an ESBL or AmpC combined with porin loss may lead to treatment failure, but it is often unstable and may impose a fitness cost, meaning that these strains rarely spread. Hence, carbapenem resistance conferred by an acquired carbapenemases is the key problem. This study helps to define the prevalence of CRE (and, more importantly CPE) in the population. We are not given a denominator for the clinical specimens, so the prevalence of CRE amongst clinical specimens cannot be calculated. However, the fact that around 5% of patients admitted to ICU / HDU were carrying CRE is a concern, although the prevalence of CPE on the rectal screens was lower at 1.7% (7/421).
Currently, the prevalence and epidemiology of CRE and CPE is poorly defined in the UK so this useful prevalence survey from Alder Hey is welcome. However, we urgently need more research from other hospitals to scale the CRE problem.