Production of KPC-2 Carbapenemase by an Escherichia coli Clinical Isolate Belonging to the International ST131 Clone

LETTER

The rapid international dissemination of Klebsiella pneumoniae carbapenemase (KPC)-producing organisms is of major concern. Of the 13 variants of KPC described to date, KPC-2 is the most widely reported and disseminated. KPC-producing isolates of K. pneumoniae have reached epidemic proportions in the United States, Israel, and Greece, with increasing reports from other European countries (1, 2, 7, 8).

Escherichia coli O25b:H4-ST131 is a very successful pandemic uropathogenic clone associated predominantly with community-acquired antimicrobial-resistant infection. The close association between the extended-spectrum β-lactamase (ESBL) CTX-M-15 and E. coli ST131 has been implicated in the international dissemination of this enzyme (2, 12). We report the KPC-2 carbapenemase in an isolate belonging to the ST131 clone; this has not been reported previously.

E. coli 490995 and K. pneumoniae 490995.1 were isolated in April 2010 from the urine of an 84-year-old woman. She was an independently mobile long-term resident of an elderly care facility in the Mid-Western region of Ireland, with no history of foreign travel or admission to hospital in the 6 months prior to isolation of these organisms. She had received four courses of amoxicillin-clavulanic acid, two courses of quinolones (ofloxacin and ciprofloxacin), and two courses of cephalosporins (cefuroxime and cefixime) in the previous 6 months for treatment of lower respiratory tract and urinary tract infections. Screening using rectal swabs at the time of isolation of these organisms and 6 months later did not identify carriage of a carbapenemase producer among the seven other residents sharing her room.

The meropenem, ertapenem, and imipenem MICs for E. coli 490995 were 8 μg/ml, >16 μg/ml, and 16 μg/ml, respectively, as determined by agar dilution, and the isolate was susceptible to chloramphenicol, minocycline, amikacin, and kanamycin and resistant to ampicillin, ceftazidime, cefotaxime, cefpodoxime, cefoxitin, aztreonam, amoxicillin-clavulanic acid, piperacillin-tazobactam, tetracycline, sulfonamides, streptomycin, gentamicin, ciprofloxacin, nalidixic acid, and trimethoprim by the CLSI disk diffusion method (4). The meropenem, ertapenem, and imipenem MICs for K. pneumoniae 490995.1 were >32 μg/ml, >16 μg/ml, and 64 μg/ml, respectively, and the isolate was susceptible to only 3 of the 19 antimicrobial agents screened: streptomycin, gentamicin, and tetracycline. Both isolates were confirmed as carbapenemase producers by the modified Hodge method of the CLSI, and the KPC enzyme was indicated by a commercial synergy test (Rosco Diagnostica, Taastrup, Denmark). PCR and sequencing confirmed that both isolates harbored bla_KPC-2, bla_TEM-1, and bla_CTX-M-15 (6, 13, 14); K. pneumoniae 490995.1 additionally harbored bla_SHV-12. E. coli 490995 was confirmed to belong to the sequence type 131 (ST131) clonal group by PCR (3) and multilocus sequence typing (MLST) (http://mlst.ucc.ie/mlst/dbs/Ecoli). Both isolates harbored four plasmids ranging in size from 7 kb to 190 kb. A 120-kb IncFIIK2 plasmid was common to both isolates and carried bla_KPC-2 in an isoform “a” Tn4401 element (5).

The occurrence of an isolate belonging to the pandemic E. coli clonal group O25b:H4-ST131 that produces a KPC-type carbapenemase has not been reported previously, although NDM-1 and VIM-1 carbapenemases have recently been reported in this clone (9, 10, 11). Given that carbapenems are vital therapeutic agents for treatment of severe infection and the success with which CTX-M ESBL-producing E. coli 025b:H4-ST131 has disseminated throughout the world, the spread of carbapenemases into this clonal group is a cause of serious concern.

(This work was presented in part at the 21st European Congress of Clinical Microbiology and Infectious Diseases [ECCMID], Milan, Italy, 7 to 10 May 2011.)