Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii in the Intensive Care Unit of Uruguay's University Hospital Identifies the First rmtC Gene in the Species.

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are an increasing concern in intensive care units (ICUs) worldwide. The combination of carbapenemases and 16S rRNA-methyltransferases (16S-RMTases) further reduces the therapeutic options. OXA-carbapenemase/A. baumannii clone tandems in Latin America have already been described; however, no information exists in this region regarding the occurrence of 16S-RMTases in this microorganism. In addition, the epidemiology of A. baumannii in ICUs and its associated resistance profiles are poorly understood. Our objectives were as follows: to study the clonal relationship and antibiotic resistance profiles of clinical and digestive colonizing A. baumannii isolates in an ICU, to characterize the circulating carbapenemases, and to detect 16S-RMTases. Patients admitted between August 2010 and July 2011 with a clinically predicted hospital stay > 48 hr were included. Pharyngeal and rectal swabs were obtained during the first fortnight after hospitalization. Resistance profiles were determined with MicroScan® and VITEK2 system. Carbapenemases and 16S-RMTases were identified by PCR and sequencing, and clonality was assessed by pulsed-field gel electrophoresis and multilocus sequence typing. Sixty-nine patients were studied and 63 were diagnosed with bacterial infections. Among these, 29 were CRAB isolates; 49 A. baumannii were isolated as digestive colonizers. These 78 isolates were clustered in 7 pulsetypes, mostly belonging to ST79. The only carbapenemase genes detected were blaOXA-51 (n = 78), blaOXA-23 (n = 62), and blaOXA-58 (n = 3). Interestingly, two clinical isolates harbored the rmtC 16S-RMTase gene. To the best of our knowledge, this is the first description of the presence of rmtC in A. baumannii.

CTX-M-15 in combination with aac(6')-Ib-cr is the most prevalent mechanism of resistance both in Escherichia coli and Klebsiella pneumoniae, including K. pneumoniae ST258, in an ICU in Uruguay.

The objectives of this study were (i) to determine the extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EcKp) clones circulating in an intensive care unit (ICU) in Uruguay between August 2010 and July 2011, (ii) to characterise the ESBL and plasmid-mediated quinolone resistance (PMQR) genes of the studied isolates and (iii) to determine the virulotype of the clinical isolates. Clinical and gut-colonising ESBL-EcKp from ICU patients were studied. Bacterial identification and antibiotic susceptibility determination were performed using a VITEK(®)2 system. Detection of ESBL, KPC and PMQR genes was performed by PCR and sequencing. Clonality was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). In total, 54 ESBL-EcKp isolates (40 K. pneumoniae and 14 E. coli), with or without PMQR genes, were recovered from 30 of 68 inpatients. Forty-seven isolates were CTX-M-15-producers (36 as a single ESBL and 11 together with CTX-M-14). In addition, four isolates produced CTX-M-14, two produced CTX-M-2 and one produced SHV-5. No carbapenemases were detected either in E. coli or K. pneumoniae isolates. Among the ESBL-producing isolates, 42 also harboured PMQR genes: 27 aac(6')-Ib-cr; 14 aac(6')-Ib-cr and qnrB; and a single isolate carrying only qnrB. K. pneumoniae ST258, ST48 and ST16 and E. coli ST10 and ST405 were detected in 46/54 isolates, including 9 clinical isolates. In conclusion, non-KPC-producing K. pneumoniae ST258 harbouring different ESBL and PMQR genes was the main clone disseminated in the ICU. Extensive surveillance measures must be implemented to prevent the emergence of acquired plasmid-encoded blaKPC by ST258 K. pneumoniae.