Transmissible strains of Pseudomonas aeruginosa have been described for cystic fibrosis (CF) and may be associated with a worse prognosis. Using a comprehensive strain biobank spanning 3 decades, we sought to determine the prevalence and stability of chronic P. aeruginosa infection in an adult population. P. aeruginosa isolates from sputum samples collected at initial enrollment in our adult clinic and at the most recent clinic visit were examined by a combination of pulsed-field gel electrophoresis and multilocus sequence typing and compared against a collection of established transmissible and local non-CF bronchiectasis (nCFB) isolates. A total of 372 isolates from 107 patients, spanning 674 patient-years, including 66 patients with matched isolates from initial and final encounters, were screened. A novel clone with increased antibacterial resistance, termed the prairie epidemic strain (PES), was found in 29% (31/107 patients) of chronically infected patients referred from multiple prairie-based CF centers. This isolate was not found in those diagnosed with CF as adults or in a control population with nCFB. While 90% (60/66 patients) of patients had stable infection over a mean of 10.8 years, five patients experienced strain displacement of unique isolates, with PES occurring within 2 years of transitioning to adult care. PES has been present in our cohort since at least 1987, is unique to CF, generally establishes chronic infection during childhood, and has been found in patients at the time of transition of patients from multiple prairie-based CF clinics, suggesting broad endemicity. Studies are under way to evaluate the clinical implications of PES infection.

Establishing the risk of human infection is one of the goals of public health. For bacterial pathogens, the virulence and zoonotic potential can often be related to their host source. Escherichia coli bacteria are common contaminants of water associated with human recreation and consumption, and many strains are pathogenic. In this study, we analyzed three promoter-containing intergenic regions from 284 diverse E. coli isolates in an attempt to identify molecular signatures associated with specific host types. Promoter sequences controlling production of curli fimbriae, flagella, and nutrient import yielded a phylogenetic tree with isolates clustered by established phylogenetic grouping (A, B1, B2, and D) but not by host source. Virulence genes were more prevalent in groups B2 and D isolates and in human isolates. Group B1 isolates, primarily from nonhuman sources, were the most genetically similar, indicating that they lacked molecular adaptations to specific host environments and were likely host generalists. Conversely, B2 isolates, primarily from human sources, displayed greater genetic distances and were more likely to be host adapted. In agreement with these hypotheses, prevalence of S activity and the rdar morphotype, phenotypes associated with environmental survival, were significantly higher in B1 isolates than in B2 isolates. Based on our findings, we speculate that E. coli host specificity is not defined by genome-wide sequence changes but, rather, by the presence or absence of specific genes and associated promoter elements. Furthermore, the requirements for colonization of the human gastrointestinal tract may lead to E. coli lifestyle changes along with selection for increased virulence.Pathogenic strains of Escherichia coli cause millions of cases of human infection each year (52) as well as severe problems in the livestock industry (78). Yet in other situations, many E. coli strains coexist peacefully as commensals in the intestinal tract of their warm-blooded hosts. A significant amount of research has sought to understand the relationship between pathogenic and commensal E. coli strains and determine if they can be distinguished from each other (18,55,72,95). E. coli is also a common contaminant of water and various food sources (63). From a public health standpoint, it is important to establish the zoonotic and virulence potential of strains, which may be related to their natural lifestyle and host source.E. coli has been proposed to have two principal habitats, the primary being the intestinal tract of mammals and birds and the secondary being water, sediment, and soil (58, 81). Survival and adaptation in both habitats are necessary for continued evolutionary success. For isolates that have evolved toward commensalism, signs of adaptation should be apparent, be it through altered regulatory sequences, gene expression, or metabolism (29). E. coli strains can be differentiated into four main phylogenetic groups (A, B1, B2, and D) along with two minor groups (C and E) (41). In general, these grou...

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To determine whether drinking water contaminated with antimicrobial-resistant E. coli is associated with the carriage of resistant E. coli, selected households sending water samples to Ontario and Alberta laboratories in 2005-2006 were asked to participate in a cross-sectional study. Household members aged ≥12 years were asked to complete a questionnaire and to submit a rectal swab. In 878 individuals, 41% carried a resistant strain of E. coli and 28% carried a multidrug-resistant strain. The risk of carriage of resistant E. coli was 1·26 times higher for users of water contaminated with resistant E. coli. Other risk factors included international travel [prevalence ratio (PR) 1·33], having a child in nappies (PR 1·33), being male (PR 1·33), and frequent handling of raw red meats (PR 1·10). Protecting private water sources (e.g. by improving systems to test and treat them) may help slow the emergence of antimicrobial resistance in E. coli.

The genetic relatedness of Streptococcus milleri group isolates from the airways of cystic fibrosis patients was determined by using pulsed-field gel electrophoresis. This study reveals no evidence for patient-to-patient transmission in our patient population; however, within individual patients, complex inter-and intraspecies diversity and dynamics can be observed.In addition to their role in purulent infections (3,7,11), members of the Streptococcus milleri group (SMG), also known as the Streptococcus anginosus group, comprised of Streptococcus constellatus, Streptococcus intermedius, and Streptococcus anginosus, have emerged as clinically relevant in chronic airway infections in cystic fibrosis (CF) patients and have been implicated as etiologic agents of pulmonary exacerbation (6,10,13,14). We have recently described the isolation of a large number of SMG strains from a cohort of CF patients by using the semiselective medium McKay agar (12). This collection of SMG respiratory isolates was not recovered by conventional CF microbiology and enabled us to characterize the phenotypic properties of airway isolates and compare them to invasive strains (5). These results, in combination with analysis of the nucleotide sequence of the 16S rRNA gene of these strains, revealed clusters of isolates that included both CF and invasive isolates with indistinguishable phenotypic characteristics (5, 9).In this study, we evaluated whether patient-to-patient transmission was occurring in our CF patient cohort. The molecular epidemiological relationship of the SMG isolates was determined by using pulsed-field gel electrophoresis (PFGE) (4,8,15).PFGE was performed by modification of a protocol described by Bartie et al. (2). The isolates were cultured at 37°C for 48 h on brain heart infusion agar supplemented with colistin sulfate (10 g/ml) and oxolinic acid (5 g/ml) under anaerobic conditions. The cells were harvested and suspended to 20% transmittance (600 nm) in 100 mM Tris-HCl buffer (pH 7.6). Mutanolysin (100 U; Sigma-Aldrich, St. Louis, MO) was added to 500 l of cell suspension before an equal volume of molten 1% SeaKem Gold agarose (Lonza, Rockland, ME) was added. Plugs were cast at room temperature and then transferred to 1.5 ml of lysis solution (0.25 M EDTA [pH 9.0], 0.5% Brij 58, 2 g/liter sodium deoxycholate, 5 g/liter lauroyl sarcosine, 100 U/ml mutanolysin) and incubated at 37°C for 2 h. The lysis solution was replaced with 1.5 ml ESP solution (0.25 M EDTA [pH 9.5], 1% sodium lauroyl sarcosine, 0.5 mg/ml proteinase K) and incubated at 55°C for 2 h. The plugs were rinsed with 1 ml of distilled water and then washed for 10-min intervals, once with distilled water and three times with 1ϫ Tris-EDTA (TE; 10 mM Tris-Hcl, 1 mM EDTA [pH 8.0]) at room temperature.For restriction digestion, the plugs were preincubated in 300 l of 1ϫ reaction buffer (Invitrogen, Carlsbad, CA) at room temperature for 15 min and then replaced with fresh 1ϫ reaction buffer supplemented with 90 U of SmaI or ApaI (New England BioLabs, Beverly, MA)...