Density of microbial colonization on external and internal surfaces of concurrently placed intravascular devices.

BACKGROUND: Intravascular devices provide essential vascular access for management of critically ill patients but can be associated with bloodstream infections. OBJECTIVES: To determine colonization rates in segments of concurrently placed peripheral arterial, nontunnelled short-term central venous catheters and peripherally inserted central catheters and the pattern of heaviest colonization when the catheters are removed. METHODS: A prospective study was conducted on inpatients with intravascular devices in place for 9 days or more. At removal, each catheter was cut into 3 segments, and each segment was cultured separately. The density of colonization on external and internal surfaces of each segment was compared by estimating odds ratios by repeated-measures ordinal logistic regression. RESULTS: A total of 48 peripheral arterial, 135 central venous, and 106 peripherally inserted central catheters were obtained from 289 patients. Colonization was greatest at the proximal external segment of all catheters. On the external surface, colonization was lower on the middle (odds ratio, 0.70; P < .001) and distal (odds ratio, 0.56; P < .001) segments than on the proximal segments. On the internal surface, colonization was lower on the proximal (odds ratio, 0.39; P < .001), middle (odds ratio, 0.30; P < .001), and distal (odds ratio, 0.31; P < .001) segments than on the external proximal segments. This trend was similar for all catheter types. CONCLUSION: Colonization of intravascular devices was heaviest on proximal segments.

Serological evidence of an antibody response in farmed southern bluefin tuna naturally infected with the blood fluke Cardicola forsteri.

In this study, adaptive immune response was investigated in farmed southern bluefin tuna, Thunnus maccoyii, infected with a sanguinicolid Cardicola forsteri. A cohort (Cohort(2005)) of southern bluefin tuna was sampled between March 2005 and August 2006. Samples were taken at the transfer of wild caught tuna to sea cages and then at regular intervals. Parasite intensity, abundance and prevalence data were recorded. An ELISA was developed to detect and quantify an antibody response against the blood fluke in southern bluefin tuna serum. Intensity and prevalence of the blood fluke were shown to peak in May 2005 at 10.9 flukes per infected fish (SE=1.72) and 97.5% prevalence and then decreased to low prevalence (10%) and intensity (1.0). There were no significant changes in prevalence or intensity in 2006. Antibody titres and seroprevalence increased from 1.37 U microl(-1) and 10% at transfer in March 2005 to reach a peak in December 2005 of 25.86 U microl(-1) (SE=6.26 U microl(-1)) and 66.66%. No significant changes were observed in antibody titres for the same cohort of fish during 2006. Parasitological and serological values from Cohort(2005) were compared to a 2006 cohort (Cohort(2006)) in March 2006 and August 2006 to determine if prior infection in Cohort(2005) elicited any protection against infection in 2006. Although significant differences were not observed in intensities between cohorts it was shown that Cohort(2005) had significantly lower abundances and prevalences of blood fluke infection than Cohort(2006). Although there was no significant difference in mean antibody titres between cohorts in March 2006, the mean antibody titre of Cohort(2006) was significantly greater than that of Cohort(2005) in August 2006. No significant differences were observed in seroprevalence. This is one of the few studies to demonstrate the development of acquired resistance in fish against a parasite in an aquaculture environment under natural infection conditions.

Maintenance of Atlantic salmon (Salmo salar) at elevated temperature inhibits cytochrome P450 aromatase activity in isolated ovarian follicles.

Atlantic salmon (Salmo salar) broodstock were transferred from natural (12-16 degrees C) to controlled temperatures of 14, 18 or 22 degrees C for 3 months during vitellogenesis. Fertility and survival were significantly reduced in eggs from broodstock held at 22 degrees C relative to 14 or 18 degrees C. Endocrine mechanisms were disrupted after only one month at 22 degrees C, as evidenced by decreased plasma vitellogenin (Vtg) and increased plasma testosterone (T) levels and, at later stages, decreased levels of plasma 17beta-estradiol (E2). In vitro incubations of isolated ovarian follicles were carried out at monthly intervals, with follicles exposed to human chorionic gonadotropin, N-2-0-dibutyryladenosine 3,5-cyclic monophosphate, and the gonadal steroid precursors 17-hydroxyprogesterone, androstenedione, and T. After one month of exposure to controlled temperature, T synthesis was generally enhanced in response to all treatments at all temperatures, but E2 synthesis was inhibited at 22 degrees C, suggesting temperature impairment of cytochrome P450 aromatase (P450arom) synthesis or activity. The effect became less marked as follicles matured suggesting that temperature sensitivity is stage dependent. The results of this study suggest that the inhibitory effects of elevated temperature on E2 and Vtg synthesis, and subsequent egg development found in the present and earlier studies, arise at least partly, from temperature modulation of P450arom.