Emergence of a KPC-3-Producing Escherichia coli ST69 as a Cause of Bloodstream Infections in Italy

Introduction

The spread of carbapenem-resistant gram negatives is a global emergency due to the lack of available therapeutic options.^3,12 In particular, carbapenem-resistant Klebsiella pneumoniae (CRKP) epidemics in some European countries raise many concerns, in consideration of the high mortality rates (40–60%) associated with invasive infections due to these bacteria.^13,15,18 Resistance to carbapenems in CRKP is predominantly conferred by plasmid-encoded K. pneumoniae carbapenemases (KPC), whereas these enzymes are less frequently recovered from other gram negatives. ¹¹

However, horizontal transfer of bla_KPC genes among Enterobacteriaceae colonizing the human intestine may occur, and invasive infections due to KPC-3-producing Escherichia coli ST131 and ST448 have been reported.^1,8,14,16 Herein, we describe two patients with bloodstream infection (BSI) due to carbapenem-resistant E. coli ST69 harboring the bla_KPC-3 gene. These episodes occurred in an Italian teaching hospital with a high burden of CRKP colonized patients (6/1,000 hospital admissions, 0.6%) (Personal unpublished data). Informed consent for the use of clinical data for scientific purposes was obtained at hospital admission from both patients.

Case Reports

A 68-year-old male patient was admitted in September 2013 to the emergency department of our hospital for a parastomal herniation causing pain and impaired ostomy function (the patient had a previous laparotomy surgery for a rectal cancer in 2003). A resection of the strangulated segment was performed.

Ten days later, the patient underwent an emergency ileostomy due to anastomosis leakage. After surgery, the patients experienced two separate episodes of severe sepsis, due to Candida guilliermondii and ampicillin-resistant Enterococcus faecium, respectively. In November 2013, carbapenem-resistant E. coli (E. coli 724) (meropenem minimum inhibitory concentration [MIC]≥16 mg/L) grew from blood cultures. Gentamicin (4 mg/kg every 24 hours) and tigecycline (50 mg every 12 hours after a loading dose of 100 mg) were administered for 14 days. The patient fully recovered from BSI and was subsequently discharged home in January 2014 after definitive revision surgery.

In November 2013, an 82-year-old patient was admitted to the same ward for cholelithiasis and colicky abdominal pain, which resolved with medical treatment. Five days after the admission, the patient had fever (38°C), and two blood cultures collected 14 hours apart resulted both positive for the same carbapenem-resistant E. coli (E. coli 728) (meropenem MIC≥16 mg/L) as suggested by PFGE profiles. According to susceptibility test results, a combined therapy of ciprofloxacin (400 mg every 12 hours) and gentamicin (4 mg/kg every 24 hours) was given for 14 days with complete recovery.

The Vitek 2 automated system (bioMérieux, Marcy l'Etoile, France) was used for identification of isolates and antimicrobial susceptibility testing. MICs of chloramphenicol were determined by broth microdilution method (BMD), and MICs of imipenem and meropenem were also determined by Etest and BMD methods. The interpretative breakpoints were based on EUCAST criteria (www.eucast.org/clinical breakpoints/). Phenotypic testing for carbapenemase was performed with the Carba NP test. ⁷

Identification of carbapenemase-encoding genes (bla_VIM-, bla_IMP-, bla_NDM-, and bla_KPC- type genes) and their variants was achieved by PCR and sequencing using primer and condition described previously.^5,6,10 Detection and sequencing of extended-spectrum β-lactamase (ESBL) and/or AmpC genes (bla_CTX-M-, bla_SHV-, bla_TEM-, and bla_CMY-2 type genes), phylogenetic typing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed as described elsewhere ⁵ ; sequence types were determined using the E. coli MLST Web site (http://mlst.warwick.ac.uk/mlst/dbs/Ecoli).

The isolates were found to produce KPC-3 carbapenemase. Results of phenotypic tests were consistent with the type of carbapenemase produced. ESBL genes (CTX-M- and/or SHV-type genes) were not detected. All isolates also carried the bla_TEM-1 β-lactamase gene. No isolate carried bla_CMY-2. Both isolates had the same PFGE profile, belonged to the phylogenetic group D and to the ST69 (Table 1).

Because the two patients were hospitalized in the same ward during the same period and the PFGE profile of the strains was identical, it is conceivable that an interpatient transmission of KPC-3-producing E. coli occurred.

Table 1 summarizes the susceptibility testing of the two KPC-3-producing E. coli. Both isolates were resistant to amoxicillin–clavulanate, extended-spectrum cephalosporins, and trimethoprim/sulfamethoxazole, while retained susceptibility to gentamicin, amikacin, ciprofloxacin, tigecycline, colistin, fosfomycin, nitrofurantoin, and chloramphenicol. Both E. coli strains were categorized as resistant to imipenem and meropenem with all methods used. Although a low categorical agreement between the reference BMD method and commercial methods has been reported, ⁴ in our study, the discrepancies observed among MIC values had no effect on susceptibility categorization.

To the best of our knowledge, this is the first report describing the emergence of a KPC-3-producing E. coli belonging to the ST69 pandemic lineage. This clone has been reported worldwide since 1999 as a cause of urinary tract infections (UTI) and BSI, predominantly in the community.^2,9 Although susceptibility of our isolates to other classes of antimicrobials such as fluoroquinolones and aminoglycosides was retained, the detection of carbapenemase-positive E. coli in CRKP-endemic areas is a matter of concern, since invasive infections due to multidrug-resistant KPC-3-producing ST131 and ST448 strains have been described in Italy and Spain, respectively.^1,14

Therefore, surveillance of carbapenem resistance is critical from both public health and clinical standpoints. In our hospital, a centralized and computerized laboratory alert system informs clinicians of any carbapenem-resistant organism isolation from analyzed specimens to rapidly adopt all possible hospital-based infection-control measures, such as rapid patient isolation and patient-dedicated use of gloves and gowns. ¹⁷ In addition, an active surveillance of contacts and patients at risk has been implemented in our hospital since January 2012, according to European guidelines and by means of rectal swab. ¹⁷ No other colonization or infections due to any carbapenemase-producing E. coli have been reported to date in our center (September 2014), possibly reflecting the success of a rapid and adequate adoption of the aforementioned infection-control measures.

Finally, as regard, antimicrobial therapy in our cases, the choice of administering combined regimens was based on their ability to improve survival in patients with CRKP BSI.^15,18 However, whether or not this effect is also true in BSI due to KPC-producing E. coli remains unknown. Further studies are needed to assess the reproducibility of these findings in infections due to KPC-producing Enterobacteriaceae other than CRKP.

In conclusion, an early detection of KPC-producing E. coli is mandatory to adopt adequate control measures and avoid the spread of carbapenem-resistant clones of gram-negative bacteria.