Epidemiological surveillance of circulating clones among carbapenem-resistant Enterobacteriaceae strains in hospitalised patients

Introduction The emerging spread of carbapenemase-producing Enterobacteriaceae strains (CPE), in particular Klebsiella pneumoniae (KPCKp) and Escherichia coli (CP-Ec), has become a significant threat for hospitalised patients. It is known as KPC-Kp strains are currently responsible for hospital-acquired infections whereas CP-Ec represent an important risk for spread in the community 1. Genes encoding for carbapenemase enzymes are frequently located on plasmids than can be exchanged among clonal strains increasing the antibiotic resistance rate. Their adaptation ability allows such clones to colonise and persist in clinical niches contributing to the global expansion of certain high-risk sequence types (STs) 2. This study was aimed to provide an epidemiological survey of CPE isolates collected from hospitalised patients in order to evaluate the potential risk associated to the circulating clones. Materials and methods Isolates were sampled during 2018 as part of routine clinical microbiology screening of patients admitted to the Regional Hospital of Ancona. Antimicrobial susceptibility was determined in accordance with EUCAST guidelines and carbapenem-resistance was assessed through PCR amplification of determinant genes (blaKPC, blaVIM, blaNDM, blaOXA-48, blaIMP). Plasmid incompatibility (Inc) group was established by PCR-based replicon typing using the PBRT 2.0 kit (Diatheva Srl). A representative strain of PBRT profile for each species was finally characterized by multilocus sequence typing (MLST) to identify the circulating STs. Results A total of 48 strains were collected from the rectal swabs of adult patients. The major part was identified as KPC-Kp (94%) whereas a low percentage was CP-Ec (6%) and more than 50% were multidrug-resistant strains (MDR). In all isolates, with the exception of a CP-Ec strain, blaKPC gene was detected and only once in combination with blaVIM. PBRT revealed that IncFIB KQ was the most predominant Inc group observed in 81% of strains and a multireplicon status was observed in 39 strains with the prevalence of FIIK, FIB KQ (33%) profile. MLST analysis distinguished 5 different STs among the 14 strains representative of each PBRT profile. In 11 strains of K. pneumoniae, 3 STs were determined with the prevalence of ST512, an endemic Italian variant of ST258, and the emerging of ST101 and ST307. The latter is slowly becoming the main competitor of the clonal group CG258 3. On the other hand, 2 STs were detected among the 3 strains of E. coli: the well-known ST131 and the sporadic ST405. All of them, designed as MDR, are able to persist in hosts for long period of time 2. Conclusions Despite the modest size, this study offers a general but relevant view of the epidemiological situation within an Italian hospital. The widespread dissemination of CPE strains as well as the identification of high-risk clones poses a threat for public health. These data emphasise the need to implement infection control measures in hospitals based on a multidisciplinary approach. An adequate cooperation between healthcare and infection control staffing supported by the routinely application of advanced molecular methods might be helpful to monitor and contain the further diffusion of clonal strains among different hospital wards.