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We report the characterization of six carbapenem-resistant Raoultella spp. (CRRS) in our hospital and a genomic analysis of 58 publicly available isolates. CRRS isolates are sporadically identified around the world, and different transposons carrying carbapenemases were the resistant mechanisms. Mobile genetic elements play an important role in acquiring antibiotic resistance genes from the hospital., We report the characterization of six carbapenem-resistant Raoultella spp. (CRRS) in our hospital and a genomic analysis of 58 publicly available isolates. CRRS isolates are sporadically identified around the world, and different transposons carrying carbapenemases were the resistant mechanisms. Mobile genetic elements play an important role in acquiring antibiotic resistance genes from the hospital. An improved understanding of these transposon and targeted control measures will be very valuable to prevent CRRS dissemination.

Raoultella terrigena R1Gly is a diazotrophic endophyte isolated from surface-sterilized roots of Nicotiana tabacum . The whole-genome sequence was obtained to investigate the endophytic characteristics of this organism at the genetic level, as well as to compare this strain with its close relatives. To our knowledge, this is the first genome obtained from the Raoultella terrigena species and only the third genome from the Raoultella genus, after Raoultella ornitholytic and Raoultella planticola . This genome will provide a foundation for further comparative genomic, metagenomic, and functional studies of this genus.

Enterobacterial strains of Raoultella spp. display a penicillinase-related β-lactam resistance pattern suggesting the presence of a chromosomal bla gene. From whole-cell DNA of Raoultella planticola strain ATCC 33531 T and Raoultella ornithinolytica strain ATCC 31898 T , bla genes were cloned and expressed into Escherichia coli . Each gene encoded an Ambler class A β-lactamase, named PLA-1 and ORN-1 for R. planticola and R. ornithinolytica , respectively. These β-lactamases (291 amino acids), with the same pI value of 7.8, had a shared amino acid identity of 94%, 37 to 47% identity with the majority of the chromosome-encoded class A β-lactamases previously described for Enterobacteriaceae , and 66 to 69% identity with the two β-lactamases LEN-1 and SHV-1 from Klebsiella pneumoniae . However, the highest identity percentage (69 to 71%) was found with the plasmid-mediated β-lactamase TEM-1. PLA-1, which displayed very strong hydrolytic activity against penicillins, also displayed significant hydrolytic activity against cefepime and, to a lesser extent, against cefotaxime and aztreonam, but there was no hydrolytic activity against ceftazidime. Such a substrate profile suggests that the Raoultella β-lactamases PLA-1 and ORN-1 should be classified into the group 2be of the β-lactamase classification of K. Bush, G. A. Jacoby, and A. A. Medeiros (Antimicrob. Agents Chemother. 39: 1211-1233, 1995). The highly homologous regions upstream of the bla PLA-1A and bla ORN-1A genes comprised a nucleotide sequence identical to the −35 region and another one very close to the −10 region of the bla LEN-1 gene. From now on, as the bla gene sequences of the most frequent Raoultella and Klebsiella species are available, the bla gene amplification method can be used to differentiate these species from each other, which the biochemical tests currently carried out in the clinical laboratory are unable to do.

Histamine fish poisoning is caused by histamine-producing bacteria (HPB). Klebsiella pneumoniae and Klebsiella oxytoca are the best-known HPB in fish. However, 22 strains of HPB from fish first identified as K. pneumoniae or K. oxytoca by commercialized systems were later correctly identified as Raoultella planticola (formerly Klebsiella planticola ) by additional tests. Similarly, five strains of Raoultella ornithinolytica (formerly Klebsiella ornithinolytica ) were isolated from fish as new HPB. R. planticola and R. ornithinolytica strains were equal in their histamine-producing capabilities and were determined to possess the hdc genes, encoding histidine decarboxylase. On the other hand, a collection of 61 strains of K. pneumoniae and 18 strains of K. oxytoca produced no histamine.

In this study, we designed and evaluated a microalgal pretreatment method using cellulolytic bacteria that naturally degrades microalgae in their native habitat. Bacterial strains were isolated from each of two mollusk species in a medium containing 1% carboxymethyl cellulose agar. We selected nine bacterial strains that had endoglucanase activity: five strains from Mytilus chilensis , a Chilean mussel, and four strains from Mesodesma donacium , a clam found in the Southern Pacific. These strains were identified phylogenetically as belonging to the genera Aeromonas , Pseudomonas , Chryseobacterium , and Raoultella . The cellulase-producing capacities of these strains were characterized, and the degradation of cell walls in Botryococcus braunii and Nannochloropsis gaditana was tested with “whole-cell” cellulolytic experiments. Aeromonas bivalvium MA2, Raoultella ornithinolytica MA5, and Aeromonas salmonicida MC25 degraded B. braunii , and R. ornithinolytica MC3 and MA5 degraded N. gaditana . In addition, N. gaditana was pretreated with R. ornithinolytica strains MC3 and MA5 and was then subjected to an anaerobic digestion process, which increased the yield of methane by 140.32% and 158.68%, respectively, over that from nonpretreated microalgae. Therefore, a “whole-cell” cellulolytic pretreatment can increase the performance and efficiency of biogas production.

The genus Raoultella is composed of Gram-negative, aerobic, oxidase-negative, catalase-positive, nonmotile, capsulated rods belonging to the Enterobacteriaceae family ([1][1]). Raoultella ornithinolytica is found in aquatic and hospital environments ([2][2]). Occurrence of Raoultella in human

The enterobacterial repetitive intergenic consensus 1R PCR method, which provided recognizable profiles for reference strains of the three species of Raoultella and the two genetic groups of Klebsiella oxytoca , was applied to 19 clinical isolates identified as K. oxytoca . By this method, as confirmed by species-specific gene sequencing, two Raoultella ornithinolytica and two unclassifiable K. oxytoca isolates were identified.

Two strains of Raoultella planticola and one of Raoultella ornithinolytica showing carbapenem resistance were recovered from patients hospitalized in New Jersey and Ohio. All patients had received previous antimicrobial treatment, including carbapenems. These strains harbored bla KPC-2 and bla KPC-3 . Carbapenemase genes were embedded in isoforms of Tn 4401 and were plasmidic and chromosomal in location.