Prior to modern typing methods, cross-infection of P. aeruginosa between people with cystic fibrosis (CF) was felt to be rare. Recently a number of studies have demonstrated the presence of clonal strains of P. aeruginosa infecting people with CF. The aim of this study was to determine whether strains of P. aeruginosa demonstrated differences in resistance to desiccation and whether preincubation in subminimum inhibitory concentrations (MICs) of β-lactam affected desiccation resistance. The experimental data were modelled to a first-order decay model and a Weibull decay model using least squares nonlinear regression. The Weibull model was the preferred model for the desiccation survival. The presence of a mucoid phenotype promoted desiccation survival. Preincubation with antibiotics did not have a consistent effect on the strains of P. aeruginosa. Meropenem reduced desiccation resistance, whereas ceftazidime had much less effect on the strains studied. 1. Introduction Pseudomonas aeruginosa is a gram-negative, nonfermentative, aerobic bacillus belonging to the family Pseudomonadaceae. The organism is ubiquitous within the environment and is particularly isolated from moist areas such as water and soil. P. aeruginosa causes chronic respiratory infections in people with cystic fibrosis (CF) and acts as opportunistic pathogen causing bacteraemia, urinary tract infections, and hospital acquired pneumonia in patients with burns, urinary catheters, and those on invasive ventilation [1]. Although P. aeruginosa is a nonfermentative aerobe, it can grow under anaerobic conditions using nitrate as an electron receptor. Its ability to survive in a wide range of environmental conditions is partially explained by its versatile nutritional abilities and its ability to resist high concentrations of salt, dyes, disinfectants, and many common antibiotics. The bacteria has been commonly found in the drains of wash basins in hospital wards [2], and aerosols containing P. aeruginosa can be detected when opening a tap [3, 4]. Isolation of P. aeruginosa from tap water is due to contamination of the tap itself, rather than the mains water supply [5]. Prior to the advent of modern genetic typing methods cross-infection of P. aeruginosa between people with CF was felt to be a rare event. More recently a number of studies have been undertaken that demonstrate the presence of clonal strains of P. aeruginosa infecting multiple patients in CF clinics [6–9]. P. aeruginosa is intrinsically resistant to most commonly used antibiotics. Antibiotic resistance is achieved through a
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