An Outbreak of β -Lactamase Klebsiella Pneumoniae Carbapenemase 2–Producing Klebsiella Pneumoniae Bacteremia in Hematology Patients

Carbapenems are frequently used for severe hospital
infections caused by K. pneumoniae, especially when isolates
produce extended-spectrum β-lactamases...


Introduction
Carbapenems are frequently used for severe hospital infections caused by K. pneumoniae, especially when isolates produce extended-spectrum β-lactamases (ESBLs) or have chromosomal cephalosporinases. The last decade, several studies have documented the emergence of carbapenem resistant K.
pneumoniae (CR-KP) worldwide and in Greece. Data from the Greek System for the Surveillance of Antimicrobial Resistance [1] show that among K. pneumoniae blood isolates, carbapenem resistance increased from <1% in 2001 to 42% in medical wards and to 72% in intensive care units (ICUs). Carbapenem resistance is mainly due to the production of carbapenemases which is considered to be the most important molecular mechanism. Carbapenemases belong to four molecular families but Classes A and B and D are of greater clinical importance. Classes A and B are distinguished by the hydrolytic mechanism at the active site. The carbapenemases of Class A utilize serine at their active sites, with KPC being the main representative. The carbapenemases of Class B contain at least one zinc atom at the active site, establishing them as metalloenzymes, with VIM and IMP representing the most prevalent enzymes [2]. In 2001, the first KPC-producing K. pneumoniae isolate was reported in North Carolina [3] and then several reports documented the emergence of Enterobacteriaceae strains from various species producing b-lactamase KPC-2 and KPC-3 variants in the eastern USA and recently disseminated in other countries worldwide, such as France, Colombia, Israel and China [4][5][6]. There were two publications, one in late 2007 and the other in early 2008, reporting infections due to KPC-producing K. pneumoniae in two patients, one in Sweden and the other in France. Both patients had originally been hospitalized in Crete, Greece [7,8]. The same time period two other outbreaks of infections due to K. pneumoniae were identified in two Greek hospitals [9,10]. A surveillance study organized from February through December 2008 at 21 hospitals in Greece identified the presence of KPC-2-producing K. pneumoniae at 18 hospitals in Athens, Crete, and Thessaloniki. Among the 171 isolates studied, 97.1% belonged to the same pulse type, which was found at 17 hospitals, suggesting a nationwide dissemination of a hyperepidemic clone [11,12]. The aim of the present study was to describe the epidemiologic, microbiologic and clinical characteristics of the emergence of KPC-2 producing K. pneumoniae outbreak at a General Hospital, in Athens.

Setting
We conducted a retrospective study of KPC-2 producing K. preunoniae bacteremias occurring from November 2016 through May 2019, in the 42-bed adult Hematology department of the General Hospital of Athens "G. Gennimatas". This department includes a 15-bed day care Center, a 25-bed ward and a two-bed isolation unit. All rooms have their own toilet and washroom.
During neutropenia, patients are cared for using strict contact and respiratory isolation procedures.

Bacteriological Studies
The identification and the initial susceptibility testing of K. pneumoniae strains isolated from clinical samples were performed by Kirby-Bauer method. MICs of imipenem, meropenem, ertapenem, tigecycline and colistin were determined by Vitek II automated system (bioMerieux, France) and by E-test method (AB Biodisk, bioMerieux) according to CLSI guidelines and interpretative criteria [13]. Suspect strains from colonization and infection were forwarded to the National School of Public Health in Athens for further identification. The presence of the blaKPC gene was confirmed by PCR using forward and reverse primers proposed by Queenan and Bush [2] and subsequent sequencing on both strands of the PCR products. Molecular typing was performed by pulsed field gel electrophoresis (PFGE) of Xbal-restricted genomic DNA [14]. Restriction fragments were separated through a 1% agarose using a contour-clamber homogeneous electric field DRIII apparatus (BioRad, Milano, Italy). Gel Compar II was used for classification of the isolates into PFGE types [11].

Antimicrobial Management
Systemic antimicrobial prophylaxis is not routinely

Data Collection and Definitions
We retrospectively reviewed the medical records of patients  producers, belonging to the same clone (palsotype A), (Figure 1).  Table 2.

Discussion
The emergence of multidrug-resistant Gram-negative bacteria causing nosocomial infections is growing worldwide and has become a great challenge especially for clinicians and the Public Health System. KPC-producing bacteria are frequently misclassified as carbapenem-susceptible by routine susceptibility testing and should be suspected with ertapenem resistance [16]. The outbreak strain corresponds to the predominant KPC variant (KPC-2) which has been recently published [18]. Currently, not only the KPC-2 enzyme but also the VIM-type is spread in Greece [19,20]. Recent epidemiology studies have shown that the outbreak of MBL-producing K. pneumoniae infection was polyclonal, while that of KPC-2 producing K. pneumoniae infection was monoclonal [11,12]. The epidemiological profile of the present outbreak was monoclonal similar to that described in US hospitals [21,22] and different from the polyclonal profile of the outbreak observed in Israel [6]. In our study, the monoclonal type of the outbreak and failure to isolate the implicated pathogen in the environmental stuff, implicates the poor adherence to hand hygiene among healthcare personnel and patient-to-patient spread of the pathogen as the main mechanism of transmission of the KPC strain, as was also reported in previous studies [12].

Conclusion
In summary, we described the emergence of KPC-2 producing K.pneumoniae in a Hematology Unit, which is still a major problem between immunocompromised patients, with striking mortality rates in hospitalized hematology patients. This condition underscores the urgent need for institutions to develop strategies to limit and control carbapenem-resistant outbreaks which warrants a good collaboration between clinicians, pharmacologists, microbiologists and infection control professionals.