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Reactive oxygen species (ROS) are part of the weapons used by the immune system to kill and degrade infecting microorganisms. Bacteria can produce macromolecules, such as polysaccharides, that are able to scavenge ROS. Species belonging to the Burkholderia cepacia complex are involved in serious lung infection in cystic fibrosis patients and produce a characteristic polysaccharide, cepacian. The interaction between ROS and bacterial polysaccharides was first investigated by killing experiments, where bacteria cells were incubated with sodium hypochlorite (NaClO) with and without prior incubation with cepacian. The results showed that the polysaccharide had a protective effect towards bacterial cells. Cepacian was then treated with different concentrations of NaClO and the course of reactions was followed by means of capillary viscometry. The degradation products were characterised by size-exclusion chromatography, NMR and mass spectrometry. The results showed that hypochlorite depolymerised cepacian, removed side chains and O-acetyl groups, but did not cleave the glycosidic bond between glucuronic acid and rhamnose. The structure of some oligomers produced by NaClO oxidation is reported.

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This study describes the dissemination of a carbapenem-resistant Acinetobacter baumannii (CRAB) strain in a university hospital in Northeast Italy. Characterization of the outbreak strain was combined with a retrospective analysis of all CRAB isolates collected in the same hospital during the 5 years preceding the outbreak, with the aim of elucidating the origin of the epidemic spread. The outbreak strain was shown to belong to the International Clone II and carry the bla gene, flanked by two ISAba1 sequences in opposite orientation (Tn2006 arrangement). The epidemic clone harbored also the bla allele of the carbapenemase intrinsic to A. baumannii, the determinant of ArmA 16S rRNA methylase and a class 1 integron, with the aacA4, catB8, and aadA1 cassette array. Genotype analysis, performed by macrorestriction analysis and VRBA, revealed that isolates related to outbreak strain had been sporadically collected from inpatients in the 2 years preceding outbreak start. Carriage of bla, armA, and the integron further supported relatedness of these isolates to the outbreak clone. Outbreak initially involved three medical wards, typically hosting elderly patients with a history of prolonged hospitalization. The study highlights the need to adopt strict infection control measures also when CRAB isolation appears to be a sporadic event.

Il biofilm prodotto da Burkholderia cepacia complex: aspetti molecolari e relazione con gli esopolisaccaridi SUMMARY Introduction. In cystic fibrosis patients, Burkholderia cepacia complex (Bcc) can cause serious pulmonary chronic infections thanks in part to the ability to form biofilm, matrix rich in exopolysaccharides. In Bcc grown in the planktonic state, the main exopolysaccharide is cepacian while in biofilm its presence is controversial. Methods and Results. Two clinical isolates, named BTS7 and BTS2, were studied. BTS7 produces abundant cepacian but not much biofilm (quantified by colorimetric method).At least two of the genes involved in cepacian biosynthesis are not necessary for biofilm production as two BTS7 derivatives, bceB and bceQ knocked out by transposon mutagenesis, produce biofilm levels comparable to the wild-type. BTS2 sinthesyzes cepacian only if cultured on a specific medium. It has been colonizing a patient for almost ten years, showing a significant reduction of biofilm production during this period. This reduction did not appear together with the lack of factors required for the initial adhesion to the surface, or to differences in some of the Bcc genes involved in biofilm formation. Moreover, sequencing of its bce locus revealed a bceX gene, absent in BTS7, coding for a trascriptional regulator. Its product may negatively regulate the production of cepacian but not the one of other polysaccharides, promoting the formation of biofilm. Conclusions. Cepacian seems to be marginal in the production of biofilm.The reduced ability to produce biofilm of BTS2 suggests possible gene mutations occurred over time. Using custom arrays we will compare the gene expression of the BTS2 isolates, to identify the genes responsible for the observed phenotypic changes.