1192. Identification of a Novel Enterobacter cloacae Isolate Producing an IMP-13 Metallo-β-Lactamase

Abstract

BackgroundMetallo-β-lactamases (MBLs) have been identified as emerging resistance determinants in Enterobacteriaceae, A. baumanii, and P. aeruginosa. Early identification of carbapenemase-producing organisms (CPOs) is essential to prevent dissemination within healthcare settings. We report a case of a patient who was blood culture positive for a multidrug-resistant E. cloacae which was subsequently found to be positive for the MBL blaIMP-13.MethodsA 74-year-old female, with no significant past medical or travel history, developed sepsis 2 days after undergoing debulking surgery for stage IIIc ovarian carcinoma. Blood cultures were positive for Gram-negative bacilli and the organisms identified as Enterobacter spp. with blaIMP MBL (Verigene). Antimicrobial susceptibility testing demonstrated high-level resistance to all penicillins, ureidopenicillins, cephalosporins, and β-lactam/inhibitor antibiotics, and susceptibility to colistin, tigecycline, and monobactams.ResultsFurther testing using micro-broth dilution, BD phoenix, and Etest, demonstrated susceptible MICs to meropenem and imipenem, with intermediate to resistant MICs to ertapenem. The patient was treated with a combination therapy of amikacin, aztreonam, and ceftazidime-avibactam and responded clinically. Per standard protocol, the organism was sent to WI Laboratory of Hygiene for further characterization. Phenotypic testing using the modified carbapenem inactivation test (mCIM) was positive, indicating the presence of a carbapenemase; however, results using Xpert CarbaR (Cepheid) were negative. Subsequent sequencing of the isolate confirmed the presence of blaIMP-13.ConclusionThis was an important case for several reasons. First, blaIMP-13 is historically reported in Pseudomonas aeruginosa. Indeed, this was the first report of Enterobacteriaceae harboring blaIMP in WI. Second, it had unique susceptibility pattern to carbapenems and was not detected by the CarbaR. Third, these data demonstrate clinical success in treating an MBL CPO with a combination anti-microbial regimen, based on an understanding of resistance mechanisms involved. This report calls for more vigilant screening for CPO using both phenotypic and genotypic methods.Disclosures N. Ledeboer, Luminex: Consultant, Consulting fee.