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The antibiotic management of catheter-related infections (CRIs) often fails owing to the emergence of antimicrobial-resistant strains and/or biofilm/persister apparitions. Thus, we investigated the efficacy of two novel antimicrobial agents, i.e., the synthetic peptide SAAP-148 and the novel antibiotic halicin, against Gram-negative bacteria (GNB) colonizing catheters. The antibacterial, anti-biofilm, and anti-persister activities of both agents were evaluated against Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae strains. The enrolled strains were isolated from catheters and selected based on their resistance to at least three antibiotic classes and biofilm formation potential. Furthermore, the hemolysis and endotoxin neutralization abilities of these agents were explored. The bactericidal activity of both agents was reduced in urine and plasma as compared to buffered saline. In a dose-dependent manner, SAAP-148 and halicin reduced bacterial counts in 24 h preformed biofilms on silicone elastomer discs and eliminated persisters originating from antibiotic-exposed mature 7-day biofilms, with halicin being less effective than SAAP-148. Importantly, SAAP-148 and halicin acted synergistically on E. coli and K. pneumoniae biofilms but not on A. baumannii biofilms. The peptide, but not halicin, decreased the production of IL-12p40 upon exposure to UV-killed bacteria. This preliminary study showed that SAAP-148 and halicin alone/in combination are promising candidates to fight GNB colonizing catheters. [ABSTRACT FROM AUTHOR]

Within the genus Acinetobacter, A. baumannii is clinically the most relevant species, frequently involved in hospital outbreaks and affecting critically ill humans (1 ,2). The strains involved are usually multidrug [...]

The name 'Acinetobacter venetianus' has been used previously to designate three marine hydrocarbon-degrading Acinetobacter strains, of which strain RAG-1 (=ATCC 31012) has industrial applications for the production of the bioemulsifier emulsan. However, to date, the name of this taxon has not been validly published. In this study, five strains were examined to corroborate the delineation of this taxon by means of phenotypic characterization, DNA-DNA hybridization, selective restriction fragment amplification (AFLP), amplified rDNA restriction analysis (ARDRA), rpoB gene sequence analysis and tRNA intergenic spacer length polymorphism analysis (tDNA-PCR) and to emend the description of 'Acinetobacter venetianus' (ex Di Cello et al. 1997). AFLP analysis showed that the five strains formed a tight cluster at 56.8+/-5.0 % genomic relatedness that was separated from strains of other haemolytic species of the genus Acinetobacter and from the type and reference strains of other Acinetobacter species at

The taxonomic status of 24 haemolytic, non-glucose acidifying Acinetobacter strains that did not belong to any previously described species was investigated by means of a polyphasic approach. Using AFLP fingerprinting, amplified rDNA restriction analysis and phenotypic characterization, the strains were classified into two phenetically coherent groups (comprising 15 and 9 strains) that were distinct from each other and from all known Acinetobacter species. Confirmation that these groups formed two separate lineages within the genus Acinetobacter was obtained from comparative analysis of partial sequences of the gene encoding the beta-subunit of RNA polymerase in all strains and also from 16S rRNA gene sequence analysis of representative strains. Previously published DNA-DNA reassociation data for some of the strains used also supported the species rank for both groups, for which the names Acinetobacter beijerinckii sp. nov. and Acinetobacter gyllenbergii sp. nov. are proposed. The strains of A. beijerinckii sp. nov. originated from human and animal specimens and from various environmental sources, whereas those of A. gyllenbergii sp. nov. were isolated exclusively from human clinical specimens. The phenotypic characteristics most useful for the differentiation of these species from other Acinetobacter species that comprise haemolytic strains were the inability of A. beijerinckii sp. nov. to grow on l-arginine and the ability of A. gyllenbergii sp. nov. to grow on azelate. The type strain of A. beijerinckii sp. nov. is NIPH 838T (=LUH 4759T=CCUG 51249T=CCM 7266T=58aT) and the type strain of A. gyllenbergii sp. nov. is NIPH 2150T (=RUH 422T=CCUG 51248T=CCM 7267T=1271T).

Using tDNA-PCR, the type strain CCM 7198T (<--CIP 107470T <--17A04T) of Acinetobacter grimontii was found to be indistinguishable from Acinetobacter junii strains. Therefore, the phenotypic properties, amplified fragment length polymorphism (AFLP) patterns and 16S rRNA and rpoB gene sequences of the type strain of A. grimontii (CCM 7198T) were determined. We found that the strain used l-arginine and l-glutamate, in contrast to the original description and in accordance with the phenotypic properties of A. junii. By AFLP analysis, A. grimontii CCM 7198T clustered at 50.2 % with a set of A. junii strains previously identified by DNA-DNA hybridization, which is in accordance with the previously established intraspecies values of this technique. Sequence similarity of the 16S rRNA gene between the type strains of the two species was found to be 99.9 %. Finally, DNA-DNA relatedness between the type strains of A. junii and A. grimontii was redetermined and was found to be 85 %. These findings were corroborated for a second representative of the A. grimontii type strain, DSM 14968T. These data confirm that Acinetobacter grimontii is a later heterotypic synonym of Acinetobacter junii.