Emergence of NDM-1 and OXA-72 producing Acinetobacter pittii clinical isolates in Lebanon.

Acinetobacter spp. have emerged as global opportunistic pathogen causing a wide range of infections. Emergence of carbapenem resistance in these organisms is a matter of great concern. We report here the first detection of Acinetobacter pittii clinical isolates in Lebanon carrying either the bla NDM-1 or the bla OXA-72 gene.

The genus Acinetobacter comprises to date more than 50 species, among which Acinetobacter baumannii is the most clinically relevant, often associated with pneumonia, septicaemia, urinary tract infections, wound infections and meningitis [1]. Treatment of infections caused by this opportunistic bacterium is a challenge as a result of its strong ability to develop resistance to a wide range of antimicrobial agents, especially carbapenems. This resistance trait is mainly related to production of acquired carbapenem-hydrolyzing class D β-lactamases and metallo-β-lactamases [2]. In the last decades, the role of non-baumannii Acinetobacter in human infections has been increasingly recognized as a result of advances in molecular biology [3]. There are several reports of multidrug-resistant strains of Acinetobacter pittii and Acinetobacter nosocomialis in healthcare facilities around the world [4].

This study was initiated by the isolation of two imipenem-resistant A. pittii strains recovered in two hospitals in Tripoli, North Lebanon, in 2015. The first one, designated CMUL332, was isolated from the urine of a 4-month-old child who was admitted to the intensive care unit for fever and nephritic syndrome. The second one, CMUL334, was isolated from the urine of a 15-year-old girl patient hospitalized with febrile gastroenteritis. Bacterial identification was performed by matrix-assisted desorption ionization–time of flight mass spectrometry and partial rpoB gene sequencing [5]. Antimicrobial susceptibility was determined by the disk diffusion method according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing (http://www.eucast.org). Both isolates were resistant to ticarcillin, ticarcillin/clavulanate and ceftazidime and were of intermediate susceptibility to piperacillin/tazobactam. In contrast, they remained susceptible to aminosides, tigecycline, rifampin, ciprofloxacin and colistin, except strain CMUL332, which was resistant to tobramycin and netilmicin. The Etest method confirmed the carbapenem-resistant phenotype because the minimum inhibitory concentration for meropenem was >32 mg/L and for imipenem either >32 mg/L (CMUL332) or 16 mg/L (CMUL334). Screening of blaOXA-23-like, blaOXA-24-like, blaOXA-58-like and blaNDM genes by real-time PCR revealed that CMUL332 harboured the blaNDM gene, while CMUL334 carried the blaOXA-24 like gene. Sequencing of the entire carbapanemase genes showed that they encoded for NDM-1 and OXA-72 variants, respectively.

OXA-72-producing A. pittii was first described in Colombia in 2012 from a catheter tip–positive culture of a patient who had ischaemic hepatitis and multiorgan failure [6]. This enzyme has subsequently been reported from carbapenem-resistant clinical isolates of A. pittii in France [7]. On the other hand, identification of NDM-positive non-baumannii Acinetobacter is now increasingly reported worldwide, concomitantly with those of A. baumannii isolates. Indeed, recent studies have demonstrated the emergence and the dissemination of NDM-1-producing A. pittii in several countries, including China [4], [8], Turkey [9] and recently Brazil [10].

This study is the first report of A. pittii producing OXA-72 and NDM-1 in Lebanon, which highlights the clinical relevance of this bacterium, in accordance with a series of recent studies [3]. Therefore, surveillance is warranted, and early detection of carbapenemase genes is recommended to avoid their major spread to more clinically relevant bacterial species.