Emergence of Klebsiella pneumoniae producing NDM-1 carbapenemase in Saint Petersburg, Russia

Sir, Gram-negative bacilli producing NDM-type metallo-carbapenemases present a recognized threat to the healthcare system. Most NDM-positive isolates are multidrug resistant and remain susceptible only to colistin and tigecycline. Although first and most often detected in Klebsiella pneumoniae and Escherichia coli, the NDM-1 gene can spread rapidly and has been found in diverse bacterial strains and species, in healthcare settings and in the environment. NDM producers have been reported from many countries and often, though not always, from patients with travel or healthcare links in other countries. We report here an NDM-1-producing strain of K. pneumoniae that was recovered in a Russian patient with no history of overseas travel. In April 2012, a patient with heart failure (class III, New York Heart Association functional classification) was admitted to Almazov Centre, where the patient received standard treatment for this condition. The patient did not have a urinary catheter during this hospitalization and no antibiotics were administered; the patient was discharged 31 days after admission when the symptoms of heart failure were stabilized. The patient has resided solely in Saint Petersburg throughout their life. At the end of May 2012, the patient complained of frequent urination. An outpatient urine sample yielded 1.5×10 leucocytes/L and a multidrug-resistant K. pneumoniae (10 cfu/mL) was cultured (isolate 1), which was susceptible in vitro to aztreonam, colistin, chloramphenicol, tetracyclines and tigecycline. The MIC of fosfomycin, determined by the agar dilution method, was 16 mg/L and the patient received this preparation (daily dose 3 g) for 2 days with a positive clinical effect. Microbiological reinvestigation was not performed. Multidrugresistant K. pneumoniae (10 cfu/mL) was again isolated from a follow-up outpatient urine sample taken 5 weeks later (isolate 2). CT revealed urolithiasis and chronic pyelonephritis. By this time, both isolates 1 and 2 were known to carry the blaNDM-1 gene (see below) and aztreonam was initiated at a daily dose of 3.0 g after readmission of the patient to Almazov Centre. The treatment was terminated after 4 days due to adverse effects (diarrhoea and hypotension) and urine cultures yielded no bacteria up to the fifth day after cessation of aztreonam treatment. However, 2 weeks later, multidrug-resistant K. pneumoniae (10 cfu/mL) was again recovered from a urine sample (isolate 3). No antibiotics were administered at this time. The patient’s stools did not grow Gram-negative bacilli on selective media for the detection of carbapenem-resistant Enterobacteriaceae: Brilliance CRE agar, MacConkey agar with meropenem and ertapenem discs as well as agar plates supplemented with 0.5 mg/L meropenem. E. coli and Acinetobacter johnsonii isolated on non-selective agar plates were susceptible to carbapenems and did not carry the blaNDM-1 gene. The renal stones were recognized as uric acid deposits. A dietary change as well as medication was prescribed to diminish the size of the stones. The screening of contact patients and careful microbiological investigation of the hospital environment did not reveal carbapenem-resistant Enterobacteriaceae. The patient was discharged home, to the community. The patient was scheduled for hospitalization to the specialized urological department. The three urinary isolates were identified as K. pneumoniae subsp. pneumoniae by sequencing of the first 500 bp of the 16S RNA gene (MicroSeq ID 16S rDNA 500 Library V. 2.1). Multilocus sequence typing was performed as described on the web site of the Pasteur Institute, France (http://www.pasteur.fr/ recherche/genopole/PF8/mlst/Kpneumoniae.html); all three isolates belonged to sequence type ST340, which has been associated with NDM-1-positive isolates from Oman and South Korea. The isolates were tested by PFGE of XbaI-digested DNA (PulseNet standard operating procedure for E. coli). The PFGE patterns of the NDM-1-producing K. pneumoniae isolates are shown in Figure 1. All isolates from the patient’s urine belonged to the same PFGE type. The PFGE profile of a reference strain of K. pneumoniae producing NDM-1 carbapenemase from Finland (K. pneumoniae, NDM-1, ESBL no. 2050, National Institute for Health and Welfare, Turku, Finland) was completely different (Figure 1). Antibiotic susceptibilities were determined on Mueller–Hinton agar by disc diffusion (Oxoid, UK) and by a microdilution method (Sensititre, Trek Diagnostic Systems, USA). The results were interpreted, where possible, using CLSI guidelines or, in the absence of a CLSI breakpoint (e.g. colistin), using EUCAST guidelines. The isolates were resistant to all b-lactams except aztreonam (Table S1, available as Supplementary data at JAC Online); Research letters