Analysis of pCl107 a large plasmid carried by an ST25 Acinetobacter baumannii strain reveals a complex evolutionary history and links to multiple antibiotic resistance and metabolic pathways.

Acinetobacter baumannii has successfully spread during the last decades as one of the main critically important pathogens. However, many aspects including plasmids, are still under-investigated. Here, we report the complete sequence of an Acinetobacter baumannii strain, belonging to the ST25IP (Institut Pasteur) sequence type recovered in 2012 in Lebanon, using a combination of Illumina MiSeq and Oxford Nanopore sequencing and a hybrid assembly approach. This strain (Cl107) carries a 198 kb plasmid called pCl107 that encodes the MPFI conjugative transfer system. The plasmid carries the aacA1, aacC2, sul2, strAB, and tetA(B) antibiotic resistance genes. pCl107 region encompassing the sul2, strAB, tetA(B) is closely related to AbGRI1 chromosomal resistance islands, which are widespread in A. baumannii strains belonging to Global Clone 2. The resistance region found in pCl107 is one of the missing links in the evolutionary history of the AbGRI1 islands. pCl107 also contains a BREX Type 1 region and represents one of the two main evolution patterns observed in BREX clusters found in plasmids related to pCl107. pCl107 also harbours a ptx phosphonate metabolism module, which plays an ancestral structure compared to other large plasmids in ST25 strains. While the uric acid metabolic module found in pCl107 is incomplete, we identified possible ancestors from plasmids and chromosomes of Acinetobacter spp. Our analyses indicate a complex evolutionary history of plasmids related to pCl107 with many links to multiple antibiotic resistance and metabolic pathways.

Molecular mechanisms of antimicrobial resistance in Acinetobacter baumannii, with a special focus on its epidemiology in Lebanon.

Acinetobacter baumannii is an opportunistic bacterium involved in several types of infection with high mortality and morbidity, especially in intensive care units. Treatment of these infections remains a challenge due to the worldwide emergence of broad-spectrum resistance to many antibiotics. Following the implementation of molecular techniques to study A. baumannii outbreaks, it has been shown that they are mainly caused by specific clones such as international clones I, II and III. The present work aims to review the available data on the mechanisms underlying antimicrobial resistance in A. baumannii, with a special focus on the molecular epidemiology of this species in Lebanon.

Wide spread of OXA-23-producing carbapenem-resistant Acinetobacter baumannii belonging to clonal complex II in different hospitals in Lebanon.

OBJECTIVES: To investigate the molecular epidemiology of Acinetobacter baumannii strains isolated from different hospitals in Lebanon. METHODS: A total of 119 non-duplicate Acinetobacter strains were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and partial rpoB gene sequencing. Antibiotic susceptibility testing was performed by disc diffusion method and all identified carbapenem-resistant isolates were investigated by PCR assays for the presence of the carbapenemase-encoding genes. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for molecular typing. RESULTS: Of the 119 A. baumannii isolates, 76.5% were resistant to carbapenems. The most common carbapenemase was the OXA-23-type, found in 82 isolates. The study of population structure using MLST revealed the presence of 30 sequence types (STs) including 18 new ones, with ST2 being the most commonly detected, accounting for 61% of the isolates typed. PFGE performed on all strains of ST2 identified a major cluster of 53 isolates, in addition to three other minor clusters and ten unique profiles. CONCLUSIONS: This study highlights the wide dissemination of highly related OXA-23-producing carbapenem-resistant A. baumannii belonging to the international clone II in Lebanon. Thus, appropriate infection control measures are recommended in order to control the geographical spread of this clone in this country.

Diversity of Acinetobacter species isolated from different environments in Lebanon: a nationwide study.

AIM: To investigate the extrahospital reservoirs of Acinetobacter spp. in Lebanon. MATERIALS & METHODS: Two thousand three hundred and sixty-one samples from different ecological niches were analyzed by culture methods. Species identification was confirmed by rpoB-gene sequencing. Multilocus sequence typing was used to characterize the Acinetobacter baumannii clones. RESULTS & CONCLUSION: Acinetobacter spp. were detected in 14% of environmental samples and 8% of food samples. Furthermore, 9% of animals and 3.4% of humans were colonized. Non-baumannii Acinetobacter were the most common species isolated and newly susceptible A. baumannii clones were detected. Interestingly, 21 isolates were not identified at the species level and were considered as putative novel species. To our knowledge, this is the largest epidemiological study investigating the epidemiology of Acinetobacter spp. outside hospitals.

Reservoirs of Non-baumannii Acinetobacter Species.

Acinetobacter spp. are ubiquitous gram negative and non-fermenting coccobacilli that have the ability to occupy several ecological niches including environment, animals and human. Among the different species, Acinetobacter baumannii has evolved as global pathogen causing wide range of infection. Since the implementation of molecular techniques, the habitat and the role of non-baumannii Acinetobacter in human infection have been elucidated. In addition, several new species have been described. In the present review, we summarize the recent data about the natural reservoir of non-baumannii Acinetobacter including the novel species that have been described for the first time from environmental sources and reported during the last years.