Browsing by keyword "Colony Count, Microbial"
Now showing items 1-7 of 7
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A fractal clonotype distribution in the CD8+ memory T cell repertoire could optimize potential for immune responsesThe nature of CD8(+) T cell memory is still incompletely understood. We have previously reported that the response to an HLA-A2-restricted influenza-derived peptide results in a complex T cell repertoire. In this study we extend this analysis and describe the repertoire with more rigor. In one individual we defined 141 distinct T cell clonotypes on the basis of the unique DNA sequence of the third complementarity-determining region of the TCR beta-chain. The frequency distribution of the clonotypes is not what is expected of a normal distribution but is characterized by a large low-frequency tail. The existence of a complex population indicates a mechanism for maintaining a large number of Ag-specific clonotypes at a low frequency in the memory pool. Ranking the clonotypes allowed us to describe the population in terms of a power law-like distribution with a parameter of decay of approximately 1.6. If the repertoire is divided into subsets, such as clonotypes that use BJ2.7 or those whose third complementarity-determining region encodes the amino acid sequence IRSS, the clonotype frequencies could also be described by a power law-like distribution. This indicates a self similarity to the repertoire in which smaller pieces are slightly altered copies of the larger piece. The power law-like description is stable with time and was observed in a second individual. The distribution of clonotypes in the repertoire could be mapped onto a polygonal spiral using a recursive algorithm. Self similarity, power laws, and recursive mapping algorithms are associated with fractal systems. Thus, Ag-specific memory CD8 T cell repertoires can be considered as fractal, which could indicate optimized flexibility and robustness.
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Anti-infective external coating of central venous catheters: a randomized, noninferiority trial comparing 5-fluorouracil with chlorhexidine/silver sulfadiazine in preventing catheter colonizationOBJECTIVE: The antimetabolite drug, 5-fluorouracil, inhibits microbial growth. Coating of central venous catheters with 5-fluorouracil may reduce the risk of catheter infection. Our objective was to compare the safety and efficacy of central venous catheters externally coated with 5-fluorouracil with those coated with chlorhexidine and silver sulfadiazine. DESIGN: Prospective, single-blind, randomized, active-controlled, multicentered, noninferiority trial. SETTING: Twenty-five US medical center intensive care units. PATIENTS: A total of 960 adult patients requiring central venous catheterization for up to 28 days. INTERVENTIONS: Patients were randomized to receive a central venous catheter externally coated with either 5-fluorouracil (n = 480) or chlorhexidine and silver sulfadiazine (n = 480). MEASUREMENTS AND MAIN RESULTS: The primary antimicrobial outcome was a dichotomous measure (/= 15 colony-forming units) for catheter colonization determined by the roll plate method. Secondary antimicrobial outcomes included local site infection and catheter-related bloodstream infection. Central venous catheters coated with 5-fluorouracil were noninferior to chlorhexidine and silver sulfadiazine coated central venous catheters with respect to the incidence of catheter colonization (2.9% vs. 5.3%, respectively). Local site infection occurred in 1.4% of the 5-fluorouracil group and 0.9% of the chlorhexidine and silver sulfadiazine group. No episode of catheter-related bloodstream infection occurred in the 5-fluorouracil group, whereas two episodes were noted in the chlorhexidine and silver sulfadiazine group. Only Gram-positive organisms were cultured from 5-fluorouracil catheters, whereas Gram-positive bacteria, Gram-negative bacteria, and Candida were cultured from the chlorhexidine and silver sulfadiazine central venous catheters. Adverse events were comparable between the two central venous catheter coatings. CONCLUSIONS: Our results suggest that central venous catheters externally coated with 5-fluorouracil are a safe and effective alternative to catheters externally coated with chlorhexidine and silver sulfadiazine when used in critically ill patients.
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Effect of perineal cleansing on contamination rate of mid-stream urine cultureSTUDY OBJECTIVE: Urinary tract infection (UTI) and chlamydial or gonococcal urethritis are the most common causes of female dysuria. While chlamydia and gonorrhea can be detected with a nucleic acid amplification test performed on an uncleansed first part voided urine sample, urine cultures to test for UTI require a mid-stream clean caught sample. In order to determine whether collecting two sequential non-clean caught urine samples during the same void to test for chlamydia, gonorrhea, and UTI is a reasonable approach, we assessed the degree to which perineal cleansing reduces bacterial contamination of mid-stream urine cultures. DESIGN: Experimental study comparing mid-stream urine samples collected with (n = 25) and without (n = 25) perineal cleansing. SETTING: A university-based adolescent clinic PARTICIPANTS: We recruited fifty 14-23-year-old (mean 18.5 yrs, SD 2.3) asymptomatic females. MAIN OUTCOME MEASURE: Perineal flora contamination rate of mid-stream urine cultures collected with and without perineal cleansing. RESULTS: No culture grew >10(4) colonies of a pathogenic bacterium. Eleven (44%) of the experimental group samples and 9 (36%) of the control samples grew >10(4) colonies of perineal bacterial flora (chi(2) = .33, P = 0.56). Participants' previous experience collecting mid-stream urine was not associated with less bacterial contamination. CONCLUSIONS: Among this small sample of asymptomatic young women, perineal cleansing did not significantly reduce perineal flora contamination of mid-stream urine cultures. If larger studies of symptomatic young women replicate these findings, young women could collect two sequential urine samples from the same void to test for chlamydia, gonorrhea, and UTI.
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Epidemiologic and diagnostic aspects of bacteriuria: a longitudinal study in older women.OBJECTIVE: To examine month-by-month variability of bacteriuria in a cohort of older women and to evaluate the performance of rapid diagnostic tests commonly used to indicate the presence of significant bacteriuria. DESIGN: Prospective, observational study. SETTING: Community housing sites and a long-term care institution. PARTICIPANTS: Sixty-one women, mean age 77.6, took part in the study. MEASUREMENTS: Midstream clean-catch urine samples and medical information on subjects were collected at baseline, and then monthly for 6 months. RESULTS: Bacteriuria alone (> or = 10(5) organisms per mL) occurred in 17% of all urine samples (28% of patients), bacteriuria with pyuria in 15% (26% of patients), and bacteriuria with symptoms in 3% (10% of patients). Spontaneous clearance of bacteriuria with pyuria was common (P = .30), as were new occurrences (P = .12) over 6 months of follow-up. For the outcome of bacteriuria with symptoms, sensitivity of urinary diagnostic tests such as bacteria and pyuria on microscopic analysis, and leukocyte esterase on dipstick testing, ranged from 79 to 93%. Negative predictive values of these tests approached 100%. CONCLUSIONS: Bacteriuria was a very common event, occurring in almost one-fifth of all urine samples and one-third of all subjects during 6 months of follow-up. Month-by-month follow-up indicates that the natural history of bacteriuria is marked by frequent spontaneous alternation between positive and negative events. The high negative predictive value of many simple diagnostic tests commonly used for urinary tract disease suggests that they can quickly and cost-effectively rule out bacteriuria in the older female patient.
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Heptose I glycan substitutions on Neisseria gonorrhoeae lipooligosaccharide influence C4b-binding protein binding and serum resistanceLipooligosaccharide (LOS) heptose (Hep) glycan substitutions influence gonococcal serum resistance. Several gonococcal strains bind the classical complement pathway inhibitor, C4b-binding protein (C4BP), via their porin (Por) molecule to escape complement-dependent killing by normal human serum (NHS). We show that the proximal glucose (Glc) on HepI is required for C4BP binding to Por1B-bearing gonococcal strains MS11 and 1291 but not to FA19 (Por1A). The presence of only the proximal Glc on HepI (lgtE mutant) permitted maximal C4BP binding to MS11 but not to 1291. Replacing 1291 lgtE Por with MS11 Por increased C4BP binding to levels that paralleled MS11 lgtE, suggesting that replacement of the Por1B molecule dictated the effects of HepI glycans on C4BP binding. The remainder of the strain background did not affect C4BP binding; replacing the Por of strain F62 with MS11 Por (F62 PorMS11) and truncating HepI mirrored the findings in the MS11 background. C4BP binding correlated with resistance to killing by NHS in most instances. F62 PorMS11 and its lgtE mutant were sensitive to NHS despite binding C4BP, secondary to kinetically overwhelming classical pathway activation and possibly increased alternative pathway activation (measured by factor Bb binding) by the F62 background. FA19 lgtF (HepI unsubstituted) resisted killing by only 10% NHS, not 50% NHS, despite binding levels of C4BP similar to those of FA19 and FA19 lgtE (both resistant to 50% serum), suggesting a role for the proximal Glc in serum resistance independently of C4BP binding. This study provides mechanistic insights into how HepI LOS substitutions affect the serum resistance of N. gonorrhoeae.
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Hypercholesterolemia impairs immunity to tuberculosisWe demonstrate that apolipoprotein E -deficient (ApoE(-/-)) mice are highly susceptible to tuberculosis and that their susceptibility depends on the severity of hypercholesterolemia. Wild-type (WT) mice and ApoE(-/-) mice fed a low-cholesterol (LC) or high-cholesterol (HC) diet were infected with approximately 50 CFU Mycobacterium tuberculosis Erdman by aerosol. ApoE(-/-) LC mice were modestly more susceptible to tuberculosis than WT LC mice. In contrast, ApoE(-/-) HC mice were extremely susceptible, as evidenced by 100% mortality after 4 weeks with tuberculosis. The lung pathology of ApoE(-/-) HC mice was remarkable for giant abscess-like lesions, massive infiltration by granulocytes, elevated inflammatory cytokine production, and a mean bacterial load approximately 2 log units higher than that of WT HC mice. Compared to WT HC mice, the gamma interferon response of splenocytes restimulated ex vivo with M. tuberculosis culture filtrate protein was delayed in ApoE(-/-) HC mice, and they failed to control M. tuberculosis growth in the lung. OT-II cells adoptively transferred into uninfected ApoE(-/-) HC mice had a weak proliferative response to their antigen, indicating impaired priming of the adaptive immune response. Our studies show that ApoE(-/-) deficiency is associated with delayed expression of adaptive immunity to tuberculosis caused by defective priming of the adaptive immune response and that elevated serum cholesterol is responsible for this effect.
