Epidemiological analysis of methicillin-resistant Staphylococcus aureus isolates from adult patients with cystic fibrosis

Using pulsed-field gel electrophoresis, we genotyped 21 methicillin-resistant Staphylococcus aureus isolates from patients attending an adult cystic fibrosis unit. Eleven patients exhibited pulsotypes related to 2 locally endemic strains. Eleven chronically colonized patients were assessed over a period of up to 2 years, and all demonstrated a retention of strain type.

Genomovar diversity amongst Burkholderia cepacia complex isolates from an Australian adult cystic fibrosis unit

In this study, a combination of recA-based PCR assays and 16S rDNA restriction fragment length polymorphism (RFLP) analysis was used to determine the genomovar diversity of clinical Burkholderia cepacia complex isolates. Twenty-eight isolates were prospectively collected from patients attending a large Australian adult cystic fibrosis (CF) unit, 22 isolates were referred from other Australian CF units and a further eight isolates originated from patients without CF. The 28 prospectively collected isolates were distributed amongst the following genomovars: Burkholderia cepacia genomovar I (28.6%), Burkholderia multivorans (21.4%), Burkholderia cepacia genomovar III (39.3%), Burkholderia vietnamiensis(3.6%) and Burkholderia ambifaria (7.1%). The results of this study highlight the usefulness of 16S rDNA RFLP typing for the identification of other Burkholderia spp. and non-fermenting gram-negative bacteria.

Characterization of nontypable Haemophilus influenzae isolates recovered from adult patients with underlying chronic lung disease reveals genotypic and phenotypic traits associated with persistent infection

Nontypable Haemophilus influenzae (NTHi) has emerged as an important opportunistic pathogen causing infection in adults suffering obstructive lung diseases. Existing evidence associates chronic infection by NTHi to the progression of the chronic respiratory disease, but specific features of NTHi associated with persistence have not been comprehensively addressed. To provide clues about adaptive strategies adopted by NTHi during persistent infection, we compared sequential persistent isolates with newly acquired isolates in sputa from six patients with chronic obstructive lung disease. Pulse field gel electrophoresis (PFGE) identified three patients with consecutive persistent strains and three with new strains. Phenotypic characterisation included infection of respiratory epithelial cells, bacterial self-aggregation, biofilm formation and resistance to antimicrobial peptides (AMP). Persistent isolates differed from new strains in showing low epithelial adhesion and inability to form biofilms when grown under continuous-flow culture conditions in microfermenters. Self-aggregation clustered the strains by patient, not by persistence. Increasing resistance to AMPs was observed for each series of persistent isolates; this was not associated with lipooligosaccharide decoration with phosphorylcholine or with lipid A acylation. Variation was further analyzed for the series of three persistent isolates recovered from patient 1. These isolates displayed comparable growth rate, natural transformation frequency and murine pulmonary infection. Genome sequencing of these three isolates revealed sequential acquisition of single-nucleotide variants in the AMP permease sapC, the heme acquisition systems hgpB, hgpC, hup and hxuC, the 3-deoxy-D-manno-octulosonic acid kinase kdkA, the long-chain fatty acid transporter ompP1, and the phosphoribosylamine glycine ligase purD. Collectively, we frame a range of pathogenic traits and a repertoire of genetic variants in the context of persistent infection by NTHi.

Intraspecific variation in nitrogen source utilisation by isolates of the ericoid mycorrhizal fungus Hymenoscyphus Ericae (Read) Korf and Kernan

Variation in the abilities of 35 isolates of the ericoid mycorrhizal fungal endophyte Hymenoscyphus ericae from two field sites to utilise inorganic and organic nitrogen sources in axenic culture has been investigated. While most isolates showed a preference for NH₄/^- as a sole nitrogen source, considerable variation was observed in the abilities of isolates to utilise amino acids and protein (BSA). In particular, large intraspecific variation was observed for glutamine and BSA utilisation, with some isolates thriving on these substrates while others produced little growth. The data suggest that individual isolates of H. ericae may vary considerably in their abilities to supply their host plants with nitrogen from different substrates in soil. (C) 2000 Elsevier Science Ltd.