Escherichia coli ST131 Producing Extended-Spectrum -Lactamases Plus VIM-1 Carbapenemase: Further Narrowing of Treatment Options

TO THE EDITOR—Escherichia coli of sequence type (ST) 131 producing the CTX-M-15 extended-spectrum β-lactamase (ESBL) is emerging as a major pandemic clone causing community- and hospital-acquired infections [1]. Isolates of this lineage usually exhibit a multidrug-resistance (MDR) phenotype, including expanded-spectrum cephalosporins, fluoroquinolones, and aminoglycosides, and leaving carbapenems as the first therapeutic option for serious infections. We report on the first detection of an E. coli ST131 isolate that, in addition to CTX-M-15, produces the SHV-12 ESBL and the VIM-1 carbapenemase. E. coli FI-M-146 was isolated in Florence, Italy, in June 2009 from a 72-year-old septic carrier of an indwelling hepatic drainage. The patient had developed hepatic abscesses after splenectomy and partial hepatic resection due to a hepatosplenic histiocytic sarcoma. After admission, the patient was febrile and was empirically treated with teicoplanin (400 mg every 24 h), meropenem (1 g every 8 h), and levofloxacin (500 mg every 24 h). After 3 days of continuous fever, meropenem and levofloxacin were changed with colistin (1 million IU every 8 h) and rifampin (600 mg every 24 h). After 5 days, the results of microbiological testing indicated presence of E. coli and a methicillin-resistant Staphylococcus aureus (MRSA) in blood and E. coli in the hepatic drainage fluid. The 2 E. coli isolates exhibited the same MDR phenotype; they retained susceptibility only to meropenem, amikacin, and colistin with minimum inhibitory concentrations of 0.38, 12, and 0.5 mg/L, respectively (Table 1). Treatment was then modified by adding tigecycline (100 mg loading dose, then 50 mg every 12 h) and increasing colistin dosage (2 millions IU every 8 h). Anidulafungin (100 mg every 24 h) was also added after the isolation of Candida albicans from blood. Fever subsided after 3 days of this regimen that was continued for 7 days for antibiotics and 21 days for anidulafungin. However, 3 days after discontinuation of therapy, fever relapsed and treatment was initially restarted with tigecycline, yielding no improvement. After the blood culture results were available (5 days), yielding again E. coli, MRSA, and C. albicans, treatment was changed by addition to anidulafungin of colistin (2 millions IU every 8 h) plus rifampin (600 mg every 24 h) and linezolid (600 mg every 12 h) and was continued for 3 weeks. After 2 weeks, the patient became apiretic, and after 3 weeks, the patient was discharged. All compounds were administered endovenously.