Molecular analysis of population structure and antibiotic resistance of Klebsiella isolates from a three-year surveillance program in Florence hospitals, Italy.

We report the results of a three-year surveillance program of Klebsiella spp. in six hospitals in Florence (Italy). A total of 172 Klebsiella isolates were identified and typed by AFLP: 122 were K. pneumoniae and 50 were K. oxytoca. Most K. pneumoniae (80%) and K. oxytoca (93%) showed unrelated AFLP profiles. Beside this heterogeneous population structure, we found five small epidemic clonal groups of K. pneumoniae. Four of these groups were involved in outbreak events, three of which occurred in neonatal ICUs. The fifth clonal group spread in three different wards of two hospitals. Only one non-epidemic clonal group of K. oxytoca was detected. The frequencies of isolates with multiple antibiotic resistances increased with time; at the end of the study period, most K. pneumoniae were resistant to all the antibiotics tested. A PCR analysis of seven ertapenem resistant isolates was unable to detect any of the major genes known to underlie carbapenem resistance in K. pneumoniae.

Isolation and characterisation of bacterial colonies from seeds and in vitro cultures of Fraxinus spp. from Italian sites.

Culturable bacteria were isolated from seeds, embryos and contaminated in vitro cultures of ash (Fraxinus excelsior L., F. ornus L. and F. angustifolia L.) and were identified using morphological and molecular analyses. Fourteen morphologically distinct isolates were recovered from seeds of Fraxinus spp. 16S rDNA sequencing categorised these isolates into ten separate genera. Three strains isolated from contaminated in vitro cultures, Pantoea agglomerans, Staphylococcus succinus and Aerococcus viridans, were used for comparative analysis with isolates from seeds. Antibiotic sensitivity testing of the isolated contaminants, including phytotoxicity of antibiotics on in vitro cultures of ash, was also investigated. Phytotoxic effects on explants immersed in ampicillin or cultured on medium containing ampicillin were negligible, however tetracycline, either alone or in combination with other antibiotics, had phytotoxic effects. We conclude that ampicillin is a suitable antibiotic to limit the growth of contaminating bacteria during the in vitro culture of ash.

Cloning, nucleotide sequencing, and expression of the Azospirillum brasilense lon gene: involvement in iron uptake.

The lon gene of Escherichia coli encodes the lon (La) protease, which is associated with cellular protein degradation. A lon gene homolog from Azospirillum brasilense, a nitrogen-fixing soil bacterium which lives in association with the roots of cereal grasses, was cloned and characterized. The nucleotide sequence of the A. brasilense lon gene was determined. It contains an open reading frame that encodes a protein of 810 amino acids with a predicted molecular mass of about 90 kDa. The deduced amino acid sequence showed a high level of homology with the sequences of all the known lon gene products. An open reading frame homologous to the E. coli clpX gene was found in front of the lon gene. Transcriptional analysis showed that the lon gene of A. brasilense is induced by heat shock and that the mRNA is monocistronic. An A. brasilense mutant, with Tn5 inserted in the lon gene, was shown to be defective in iron uptake and failed to express two membrane proteins that are induced by iron starvation in the parental strain.