Clonal Dissemination of KPC-2, VIM-1, OXA-48-Producing Klebsiella pneumoniae ST147 in Katowice, Poland

Results

Patients’ characteristics. Patients’ characteristics is presented in Table I. During seven months, the 15 K. pneumoniae isolates were collected from fourteen patients aged 65.5 years on average. The average duration of hospitalization was 37 days. All patients were found to be colonized by similar CRKP isolates. One patient developed a bloodstream infection (only blood isolate available) and was successfully treated with linezolid and colistin. Two of the improved patients were treated with carbapenem. Five patients died; their deaths were not associated with any particular etiology, though. CRKP strains were isolated at various stages of patients’ hospital stay. An average time from patient admission to the microorganism isolation was 16 days; in patient no. 3 the corresponding period was 64 days, while in patients nos. 1 and 5 – the period was only five days. None of the patients had traveled abroad shortly before their hospital admissions, so any travel experience could explain the colonization.

Epidemiologic investigation. The studied K. pneumoniae isolates’ epidemic curve exhibited a bimodal distribution of cases with two peaks separated by 148 days (Fig. 1). It could indicate double discrete periods (February-March 2018 and July-August 2018) with unobserved cases in January, April, May, and June. The NR ward was involved in these distinct periods. Following the index case, four new cases were registered in the OAIT, six cases in the NR, and three in the REU (Table I).

Fig. 1.

Antimicrobial resistance. The antimicrobial resistance profiles for the isolates are listed in Table II. We have classified nine (60%) strains as MDR and six (40%) as XDR. All isolates showed resistance to penicillins, cefalosporins, carbapenems (doripenem, ertapenem, meropenem), quinolone (ciprofloxacin), aminoglycosides (amikacin, gentamycin, netilmycin, tobramycin), and other antibiotics (aztreonam, trimethoprim/sulfamethoxazole, fosfomycin). Eleven isolates (73.3%) were sensitive to amikacin, two isolates (13.3%) were in the intermediate range with the MIC values equal to 12 μg/ml, and two isolates (13.3%) were resistant. Moreover, seven strains (42.8%) were resistant to tigecycline, five (35.7%) were in the intermediate range with the MIC values above 2 μg/ml. Interestingly, two isolates (13.3%) showed susceptibility to imipenem, and the resistance of one isolate (6.7%) to imipenem was within the intermediate range.

Discussion

The presented work stems from the problem of clonal dissemination of KPC-2, VIM-1, and OXA-48-producing K. pneumoniae ST147 noticed in one hospital in Katowice, the Silesian Voivodeship, Poland.

K. pneumoniae belongs to Gram-negative bacteria of the family Enterobacteriaceae. The pathogens can easily cause hazardous epidemic outbreaks and spread globally in the form of clones with increased virulence and epidemicity. These features are associated with the widespread presence of Enterobacteriaceae in humans (gastrointestinal carriage) and their great importance as frequent infection etiologic agent in facilities that carry out inpatient and outpatient treatment (Navon-Venezia et al. 2017). Studies that focus on K. pneumoniae are therefore desired, as they provide vital scientific grounds for the relevant action to be taken in the field of public health in respect of molecular epidemiology.

This study’s subject was a particular group of microorganisms classified as bacterial alarm agents (BCA) of particular virulence or resistance, i.e., carbapenemase-producing K. pneumoniae strains belonging to the order Enterobacterales. All K. pneumoniae isolates were derived from intestinal colonization cases in the patients studied. This work elaborated epidemiological opinions on the BCA epidemic threat occurrence in the multi-profile medical center in Katowice. It was also based on suspicion of an epidemic outbreak since we noticed clonal dissemination of several CRKP isolates and one case of symptomatic hospital infection with a blood CRKP strain. This strain was isolated in a given department 48 hours after the patient’s admission. The colonization of fourteen consecutive hospitalized patients with the same strain of the CRKP was also reported. CRKP isolates had unique properties such as the accumulation of numerous antibiotic resistance mechanisms and the capability to persist in a hospital environment. It resulted in special attention being paid to CRKP strains’ health care risk (Navon-Venezia et al. 2017). The genes encoding KPC, MBL, and OXA-48 are located on the so-called mobile genetic elements (plasmids, transposons) that allow effective spreading within bacterial populations. The genes encoding KPC carbapenemases (bla_KPC) are located on the Tn4401 transposon located on plasmids with different types of replicons (IncF, IncL/M, ColE1, IncR, and IncX3). These plasmids show the ability to conjugate and propagate the bla_KPC genes to new bacterial populations (Baraniak et al. 2011).

On the other hand, the most important families of the MBL acquired are the enzymes IMP and VIM occurring both in non-fermenting and intestinal bacilli. The bla_IMP and bla_VIM genes always exist as cassettes inserted into integrons. In turn, integrons can be located on transposons and move with them between DNA molecules (Izdebski et al. 2018b). ESβL enzymes exist mainly as acquired, plasmid-encoded β-lactamases. ESβL-encoding genes are often located on conjugation plasmids (IncFII, IncI), including those with a broad host range (IncA/C, IncL/M). It allows them to spread rapidly, also between strains belonging to different species. Frequently noted are encoded by bla_CTX-M genes ESβL enzymes, active against cefotaxime CTX-M and localized on plasmids in Enterobacterales (Izdebski et al. 2018a; 2018b).

The isolates’ antibiotic susceptibility testing confirmed the β-lactamase antibiotics resistance profile typical for carbapenemase producers, as presented elsewhere (Zacharczuk et al. 2011; Guo et al. 2016; Izdebski et al. 2018a). All strains expressed high-level resistance to doripenem, ertapenem, meropenem, although they showed varying levels of resistance to imipenem. Ertapenem is the carbapenem that has been suggested as most suitable for detecting the presence of bla_KPC, which was confirmed by high MIC values for ertapenem (> 32 μg/ml) in the present study. The presence of KPC does not always result in expression of in vitro resistance to imipenem or meropenem, as this carbapenemase shows limited efficiency of β-lactam ring hydrolysis in carbapenem particles. In this study, E-test showed resistance to ertapenem of 7/25804, 11/25808, 13/25810 strains, and susceptibility or medium susceptibility to imipenem (MICs 4–8 μg/ml), while PCR confirmed the presence of the bla_KPC-2 gene in all three isolates. Imipenem and meropenem resistance of other strains might have resulted from decreased outer membrane permeability or other β-lactamases providing a synergistic effect with KPC (Protonotariou et al. 2018). The strains’ resistance to third-generation cephalosporins confirmed this hypothesis similarly to the various β-lactamases production by K. pneumoniae. The variability in CRKP strains’ carbapenem susceptibility illustrates the difficulties encountered while trying to identify strains producing carbapenemases only with the E-testing of resistance profiles. To reliably identify such strains, additional and more specific techniques should be applied (Xu et al. 2005; Magiorakos et al. 2012; Han et al. 2013; Caltagirone et al. 2017; Bukavaz et al. 2018).

The bla_KPC-2, bla_OXA-48, and bla_VIM-1 carbapenemase encoding genes and an additional bla_CTX-M-15 cefotaximase encoding genes have been found to coexist in all the strains concerned. Lee et al. (2016) found that K. pneumoniae can carry multiple β-lactamase genes in the same strain, which could be partly responsible for the pathogen’s selective success. All types of the bla genes were reported in combinations for this species (Lee et al. 2016). So far, K. pneumoniae that produce KPC-2 and KPC-3 carbapenemases have been frequently found in Europe, including Poland (Baraniak et al. 2011; Zacharczuk et al. 2011; Baraniak et al. 2015; Grundmann et al. 2017). On the other hand, Matsumura et al. (2017) presented the global dissemination of Enterobacteriaceae strains carrying the bla_VIM genes. The VIM-producing Enterobacteriaceae are generally present in Europe, particularly in Greece, Spain, Hungary, and Italy (Matsumura et al. 2017). Significantly, an increasing problem with VIM-producing K. pneumoniae has been recorded in Greece, where the strains have accounted for the deaths of 48% of patients over the last two years (Protonotariou et al. 2018). In Poland, Izdebski et al. (2018b), collected one hundred and nineteen cases of VIM/IMP-positive Enterobacteriaceae in the period from 2006 to 2012, and showed many specific or entirely new features of these microorganisms, undoubtedly related to the properties of pathogens isolated in the abovementioned central-southern countries Europe, including several likely imported from abroad (e.g., from Greece) (Izdebski et al. 2018b).

The strains containing OXA-48 β-lactamases provide another example of rapid immigration of harmful microorganisms to Europe from their endemic regions, mostly eastern and southern Mediterranean countries (Egypt, Morocco, and Turkey). OXA-48-like-positive strains cause hospital outbreaks of epidemics in Belgium, France, Netherlands, Germany, Spain, and other countries (Nordmann and Poirel 2014; Grundmann et al. 2017). In the most recent report developed by OXA-48-PL Study Group monitoring the Enterobacteriaceae OXA-48-positive strains’ spread, the authors demonstrate that these strains have been isolated relatively rarely in Poland (Izdebski et al. 2018a). It was confirmed by other European and international research teams (Nordmann and Poirel 2014; Grundmann et al. 2017). Conjugative transfer of a specific plasmid group is regarded to be the central mechanism in the spread of OXA-48 among the Enterobacteriaceae populations (Nordmann and Poirel 2014).

The high MIC values (> 256 μg/ml) for cefotaxime may suggest that the strains produced CTX-M β-lactamases. Multiplex PCR and sequencing have confirmed bla_CTX-M-15 presence in all isolates. The presence of various CTX-M β-lactamases in K. pneumoniae in Poland has been confirmed by other research teams (Baraniak et al. 2011; Izdebski et al. 2018a; 2018b). No bla_SHV or bla_TEM have been identified among the isolates. These results are in line with the persisting trend of diminished prevalence of hospital-associated K. pneumoniae strains producing SHV or TEM β-lactamases, which has also been noted by other scientists (Rodrigues et al. 2014). The type of ESβLs present in K. pneumoniae shifted in the 2000s, which caused outbreaks in hospitals due to the acquisition of plasmids and transposons encoding bla_CTX-M-type ESβLs, consequently resulting in the predominance of CTX-M-producing strains (Calbo and Garau 2015).

Among non-β-lactam antibiotics, colistin has shown the highest activity towards the strains concerned. Similar results have been published by other authors (Zacharczuk et al. 2011). Among aminoglycosides, amikacin showed the highest activity. The vast majority of strains (92.8%) were susceptible to amikacin, unlike in China, where total K. pneumoniae resistance to amikacin was demonstrated (Guo et al. 2016). The other aminoglycosides (gentamicin, netilmicin, and tobramycin) were nonreactive to the CRKP isolates concerned, in line with data reported by other authors (Zacharczuk et al. 2011; Guo et al. 2016). On the other hand, Bukavaz et al. (2018) presented other aminoglycoside susceptibility profiles in CRKP strains. These discrepancies are most likely due to different quantities or origins of the strains concerned, though they might as well be related to particular hospitals’ or ward’s antibiotic policies.

The present analysis has shown a relatively high percentage of isolates resistant to tigecycline (42.8%), a synthetic minocycline analogue with a broad spectrum of activity. The antibiotic is successfully applied to treat infections caused by multi-resistant bacterial strains, including K. pneumoniae. During tigecycline treatment, Enterobacteriaceae representatives, including CRKP strains, may become resistant to the antibiotic, as evidenced by Pfarrell et al. (2018). They demonstrated cross-resistance between tigecycline and minocycline in resistant Enterobacteriaceae strains due to the MDR pumps, which remove drugs from cells. The distribution of acquired tigecycline resistance can vary depending on the geographic location or time; therefore, it is recommended to concern data on local resistance, particularly while treating severe infections (Pfarrell et al. 2018).

Genetic similarity of CRKP isolates was determined by comparing PFGE profiles (Han et al. 2013). This method has been widely used by European and non-European research teams that study epidemic outbreaks of K. pneumoniae and evidence global spread of this species’ epidemic clones (Guo et al. 2016; Bukavaz et al. 2018; Protonotariou et al. 2018). All K. pneumoniae strains analyzed in this study belonged to ST147 (CC147). Navon-Venezia et al. (2017) reported that ST147 K. pneumoniae clone spread globally. The involvement of this pandemic clone in the spread of CTX-M-15 and other carbapenemases in European, Asian, and Middle East countries was confirmed by others (Rodrigues et al. 2014; Guo et al. 2016; Zautner et al. 2017). The data found in the literature on K. pneumoniae clonal organization has been confirmed by research focused on the molecular epidemiology of infections due to antibiotic-resistant Enterobacteriaceae (Guo et al. 2016; Protonotariou et al. 2018).

Because of the clonal nature of the isolates studied, the clinical data about their origin was reviewed to examine whether the same clonal type was circulating in the three various hospital wards. The study focused mainly on stroke patients or patients suffering from cardiovascular complications who were transferred to multiple-bed hospital rooms in Stroke Recovery Units, which were the only places where they were in touch. Moreover, it is plausible that the neurology ward played a major role in disseminating the bacteria throughout the hospital. The spread of the pathogen isolates across three different hospital wards could imply that the personnel who can access all hospital wards freely, unlike the patients and their relatives, might have transmitted the infections. Scientific literature emphasizes the role of hospitalization (and its duration) in the process of bacterial colonization. The frequency of gastrointestinal colonization with K. pneumoniae strains in hospitalized patients was high in our study. Gastrointestinal colonization with CRKP is an important risk factor for infections with strains of the same phenotype due to the easy transfer of the genes and strains’ persistence in hospital environments, which hinders their eradication. This research evidences K. pneumoniae adaptation typical of endemic hospital strains, which are corroborated by the accumulation of locally spreading resistance mechanisms to the antibiotics most commonly used for therapeutic purposes.

Ethics approval

The study was approved by the Bioethics Committee of the Jagiellonian University in Krakow, Poland (KBET/1072.6120.264.2019).

Authors’ contributions

DO collected the data, performed the molecular analysis and drafted the manuscript; HK-C collected the isolates with clinical data, performed the hospital laboratory analysis and coordinated the microbiological analysis; MB consulted the cases and edited the manuscript; MBW supervised the research and analysis, coordinated and edited the manuscript.

Funding

The present work was financially supported by Jagiellonian University Medical College in Krakow (Poland), Grant No: K/ZDS/007829.