Capsule

Abstract: OBJECTIVE. The purpose of our study was to determine whether there is a relationship between renal cortical thickness or length measured on ultrasound and the degree of renal impairment in chronic kidney disease (CKD).MATERIALS AND METHODS. From October to December 2007, 25 patients (13 men and 12 women, mean age 73 years) were identified who had CKD but were not on dialysis. The patients were from a single institution and had undergone renal ultrasound and at least three serum creatinines within 90 days. The lowest creatinine was used for estimated glomerular filtration rate (eGFR) calculation using both the Cockcroft-Gault (CG) and the Modification of Diet in Renal Disease Study (MDRD) equations. Ultrasounds were consensus reviewed by three radiologists (2 attendings and a resident) blinded to specific renal function. Cortical thickness was measured in the sagittal plane over a medullary pyramid, perpendicular to the capsule. Length was measured pole-to-pole. Linear regression was used for statistical a...

Abstract: CpsA, CpsB, CpsC, and CpsD are part of a tyrosine phosphorylation regulatory system involved in modulation of capsule synthesis in Streptococcus pneumoniae and many other gram-positive and gram-negative bacteria. Using an immunoblotting technique, we observed distinct laddering patterns of S. pneumoniae capsular polysaccharides of various serotypes and found that transfer of the polymer from the membrane to the cell wall was independent of size. Deletion of cps2A, cps2B, cps2C, or cps2D in the serotype 2 strain D39 did not affect the ability to transfer capsule to the cell wall. Deletion of cps2C or cps2D, which encode two domains of an autophosphorylating tyrosine kinase, resulted in the production of only short-chain polymers. The function of Cps2A is unknown, and the polymer laddering pattern of the cps2A deletion mutants appeared similar to that of the parent, although the total amount of capsule was decreased. Loss of Cps2B, a tyrosine phosphatase and a kinase inhibitor, resulted in an increase in capsule amount and a normal ladder pattern. However, Cps2B mutants exhibited reduced virulence following intravenous inoculation of mice and were unable to colonize the nasopharynx, suggesting a diminished capacity to sense or respond to these environments. In D39 and its isogenic mutants, the amounts of capsule and tyrosine-phosphorylated Cps2D (Cps2D∼P) correlated directly. In contrast, restoration of type 2 capsule production followed by deletion of cps2B in Rx1, a laboratory passaged D39 derivative containing multiple uncharacterized mutations, resulted in decreased capsule amounts but no alteration in Cps2D∼P levels. Thus, a factor outside the capsule locus, which is either missing or defective in the Rx1 background, is important in the control of capsule synthesis.

Abstract: The polysaccharide capsule of Streptococcus pneumoniae defines over ninety serotypes, which differ in their carriage prevalence and invasiveness for poorly understood reasons. Recently, an inverse correlation between carriage prevalence and oligosaccharide structure of a given capsule has been described. Our previous work suggested a link between serotype and growth in vitro. Here we investigate whether capsule production interferes with growth in vitro and whether this predicts carriage prevalence in vivo. Eighty-one capsule switch mutants were constructed representing nine different serotypes, five of low (4, 7F, 14, 15, 18C) and four of high carriage prevalence (6B, 9V, 19F, 23F). Growth (length of lag phase, maximum optical density) of wildtype strains, nontypeable mutants and capsule switch mutants was studied in nutrient-restricted Lacks medium (MLM) and in rich undefined brain heart infusion broth supplemented with 5% foetal calf serum (BHI+FCS). In MLM growth phenotype depended on, and was transferred with, capsule operon type. Colonization efficiency of mouse nasopharynx also depended on, and was transferred with, capsule operon type. Capsule production interfered with growth, which correlated inversely with serotype-specific carriage prevalence. Serotypes with better growth and higher carriage prevalence produced thicker capsules (by electron microscopy, FITC-dextran exclusion assays and HPLC) than serotypes with delayed growth and low carriage prevalence. However, expression of cpsA, the first capsule gene, (by quantitative RT-PCR) correlated inversely with capsule thickness. Energy spent for capsule production (incorporation of H3-glucose) relative to amount of capsule produced was higher for serotypes with low carriage prevalence. Experiments in BHI+FCS showed overall better bacterial growth and more capsule production than growth in MLM and differences between serotypes were no longer apparent. Production of polysaccharide capsule in S. pneumoniae interferes with growth in nutrient-limiting conditions probably by competition for energy against the central metabolism. Serotype-specific nasopharyngeal carriage prevalence in vivo is predicted by the growth phenotype.