High Prevalence of Carbapenem-Resistant Acinetobacter baumannii Carrying the bla OXA-143 Gene in Brazilian Hospitals

A recent article by Higgins et al. reported the identification of a novel carbapenem-hydrolyzing class D β-lactamase (CHDL), defined as OXA-143, in a carbapenem-resistant Acinetobacter baumannii strain isolated in Brazil in 2004 (5). This enzyme, which has 88% identity with OXA-40, is the first representative of a novel subgroup of CHDLs whose prevalence remains to be determined (5). In an attempt to carry out this task, we have conducted a surveillance study of carbapenem-resistant A. baumannii isolates in order to determine the antimicrobial susceptibility patterns and prevalence of blaOXA-type carbapenemase genes in medical centers in both the southeastern and southern regions of Brazil. We report here a high prevalence of carbapenem-resistant A. baumannii carrying the blaOXA-143 and blaOXA-23 genes, along with the first isolation of strains carrying the blaOXA-72 (OXA-72 is a single-amino-acid variant of OXA-40) and blaOXA-58 genes in Brazilian hospitals. From 2004 to 2008, 36 carbapenem-resistant A. baumannii isolates recovered from different patients hospitalized in eight medical centers were screened for the presence of genes encoding metallo-β-lactamases (MβLs) and OXA-type β-lactamases (6, 15). Flanking sequences of blaOXA-type genes were characterized by PCR using primers targeting ISAba-1 or -3 (12). PCR products were confirmed by sequencing, and the genetic diversity of blaOXA-positive strains was determined by enterobacterial repetitive intergenic consensus (ERIC)-PCR analysis (11). All isolates were found to be resistant to imipenem, meropenem, ceftazidime, aztreonam, piperacillin-tazobactam, and ciprofloxacin. Tobramycin (61.1%), ampicillin-sulbactam (61.1%), gentamicin (47.2%), amikacin (27.8%), and cefepime (11.1%) susceptibility rates were determined. MβL-encoding genes were not identified, whereas a high prevalence of blaOXA genes was noticed among carbapenem-resistant isolates (Table ​(Table1). 1). In this regard, 21 strains (58.3%) carried the blaOXA-143 gene, 15 strains (41.7%) carried the ISAba-1/blaOXA-23 gene array, one strain carried the ISAba-3/blaOXA-58/ISAba-3 gene array, and two isolates carried the blaOXA-72 gene (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"FJ628170","term_id":"223585696","term_text":"FJ628170"}}FJ628170, {"type":"entrez-nucleotide","attrs":{"text":"FJ492877","term_id":"219563065","term_text":"FJ492877"}}FJ492877, {"type":"entrez-nucleotide","attrs":{"text":"FJ969387","term_id":"238866561","term_text":"FJ969387"}}FJ969387, and {"type":"entrez-nucleotide-range","attrs":{"text":"HM804278 to HM804281","start_term":"HM804278","end_term":"HM804281","start_term_id":"308737170","end_term_id":"308737176"}}HM804278 to HM804281). Although the presence of the blaOXA-51 and ISAba-1 genes was confirmed in all of the isolates, no colinearity of the two genes (i.e., ISAba-1 adjacent to the blaOXA-23 gene) was observed. Isolates harboring the blaOXA-143, blaOXA-72, and blaOXA-58 genes were restricted to hospitals located in Sao Paulo (the largest and most populous metropolitan area in southeastern Brazil), while blaOXA-23-harboring A. baumannii isolates were obtained from hospitals in Sao Paulo and Parana (in southern Brazil), confirming previous reports of widespread dissemination of OXA-23-producing A. baumannii in this region (2, 9). Finally, ERIC-PCR typing revealed genetic diversity among blaOXA-143- and blaOXA-23-positive A. baumannii isolates. TABLE 1. Characteristics of carbapenem-resistant A. baumannii isolates carrying blaOXA-type genes encoding class D carbapenemasesa In summary, the blaOXA-143 gene was commonly identified among the carbapenem-resistant A. baumannii isolates surveyed in this study. Also, we report the first isolation of blaOXA-72- and blaOXA-58-carrying strains in Brazilian hospitals. OXA-143 is a new subgroup of CHDL identified in isolates of A. baumannii from Brazil (5). We would only bring to mind that the blaOXA-72 gene was first reported from an A. baumannii strain in Thailand in 2004 (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"AY739646","term_id":"52699554","term_text":"AY739646"}}AY739646), and so far it has been restricted to Acinetobacter sp. isolates from Asian and Mediterranean countries (1, 4, 7, 8, 14).