Decreased virulence of cystic fibrosis Pseudomonas aeruginosa in Dictyostelium discoideum

The characteristics of clinical and environmental isolates of Pseudomonas aeruginosa from both hospital and community settings were analyzed in a eukaryotic virulence model employing the AX2 and X22 mutants of Dictyostelium discoideum. Thirty-one strains, including two Australian epidemic strains, of P. aeruginosa were analyzed, five from environmental sources, six from clinical sources other than cystic fibrosis (CF) patients and nineteen from CF patients’ respiratory secretions. The majority of CF isolates almost uniquely supported the growth of D. discoideum. CF isolates of P. aeruginosa were found to be less virulent than isolates from other sources. Varying degrees of inhibition of the developmental cycle of D. discoideum when growing on CF isolates were also noted. This is the first description of P. aeruginosa isolates from clinical and environmental sources supporting the growth of D. discoideum

Antimicrobial susceptibility testing of cystic fibrosis and non-cystic fibrosis clinical isolates of Pseudomonas aeruginosa : a comparison of three methods

Pseudomonas aeruginosa is an important pathogen in humans, particularly in the context of nosocomial infection and infections of the cystic fibrosis (CF) lung. In order to provide clinicians with information about the likely effectiveness of specific antimicrobial treatment for P. aeruginosa infections, clinical laboratories employ in vitro antimicrobial susceptibility testing. Two commonly employed methods are the CLSI disc diffusion and Etest methods. The purpose of this study is to compare the accuracy of susceptibility results generated by these two methods against agar dilution as the reference method. Susceptible or nonsusceptible (resistant and intermediate) results of the Etestand CLSI disc diffusion methods are compared with CLSI agar dilution results for a large cohort of clinical cystic fibrosis (CF, n=71) and non-cystic fibrosis (n=83) isolates using Clinical and Laboratory Standards Institute (CLSI) interpretive criteria. An unacceptable number of major and very major errors were observed for various antimicrobials tested against both CF and non-CF isolates when using the Etest and CLSI disc-diffusion methods. The potential for error in standard laboratory antimicrobial susceptibility testing should be considered by clinicians when being guided by the results of such tests in the prescription of antimicrobial agents for P. aeruginosa infection

Emergence of multi-resistant Pseudomonas aeruginosa in a Western Australian hospital

Multi-resistant Pseudomonas aeruginosa (MRPa) has been isolated from patients in a Western Australian teaching hospital with increasing frequency since first encountered in 2006. Between 2006 and 2008 the number of patients with MRPa increased from three to nine per annum, and their location shifted from intensive care to a high dependency unit. A novel water-saving device (aerator) in a staff hand basin was identified as a likely disseminator, with MRPa being isolated from biofilm in the basin's plumbing. The disposal of patient waste, surplus intravenous antibiotic infusions and solid items via hand basins were possible contributory factors. Genotyping of MRPa from patients in other hospitals showed distinct genotypic lineages. The third seasonal cluster persisted for longer, indicating adaption to environment. More effective environmental control of P. aeruginosa is urgently needed

Deployable laboratory response to influenza pandemic: PCR assay field trials and comparison with reference methods

Background: The influenza A/H1N1/09 pandemic spread quickly during the Southern Hemisphere winter in 2009 and reached epidemic proportions within weeks of the official WHO alert. Vulnerable population groups included indigenous Australians and remote northern population centres visited by international travellers. At the height of the Australian epidemic a large number of troops converged on a training area in northern Australia for an international exercise, raising concerns about their potential exposure to the emerging influenza threat before, during and immediately after their arrival in the area. Influenza A/H1N1/09 became the dominant seasonal variant and returned to Australia during the Southern winter the following year. Methods: A duplex nucleic acid amplification assay was developed within weeks of the first WHO influenza pandemic alert, demonstrated in northwestern Australia shortly afterwards and deployed as part of the pathology support for a field hospital during a military exercise during the initial epidemic surge in June 2009. Results: The nucleic acid amplification assay was twice as sensitive as a point of care influenza immunoassay, as specific but a little less sensitive than the reference laboratory nucleic acid amplification assay. Repetition of the field assay with blinded clinical samples obtained during the 2010 winter influenza season demonstrated a 91.7% congruence with the reference laboratory method. Conclusions: Rapid in-house development of a deployable epidemic influenza assay allowed a flexible laboratory response, effective targeting of limited disease control resources in an austere military environment, and provided the public health laboratory service with a set of verification tools for resource-limited settings. The assay method was suitable for rapid deployment in time for the 2010 Northern winter