Article Figures & Data
Figures
- FIG. 1.
Role of CPS in the resistance to antimicrobial peptides and proteins. Survival of bacteria (percentage of colony counts of cells not exposed to the agents) with different amounts of HNP-1 (A), HBD1 (B), lactoferrin (C), protamine sulfate (D), and polymyxin B (E). Each point represents the mean and standard deviation of eight samples from four independently grown batches of bacteria, and significant survival differences between 52145 and 52K10 are indicated by asterisks. Symbols: •, K. pneumoniae 52145; ▵, K. pneumoniae 52O21; ○, K. pneumoniae 52K10.
- FIG. 2.
Role of CPS and O antigen in the resistance to antimicrobial peptides. (A) Survival of bacteria (percentage of the colony counts of cells not exposed to polymyxin B) after incubation with 1 U of polymyxin B/ml. Error bars display the standard deviation from the mean of three experiments, each one run in duplicate. Also shown are the CPS serotype, the amount of capsule bound to the cell surface, and whether the strains tested express O antigen. (B) Survival of bacteria (percentage of colony counts of cells not exposed to polymyxin B) after incubation with different amounts of polymyxin B. Each point represents the mean and standard deviation of four samples from two independently grown batches of bacteria. Symbols: •, K. pneumoniae USA0352/78 (wild-type strain); ○, K. pneumoniae USA0352/78-3 (CPS mutant).
- FIG. 3.
CPS affects the self-promoted pathway. Effect of polymyxin B on the permeability of the OM determined as SDS-induced lysis (A), lysozyme-induced lysis (B), and NPN partition (C). In the absence of polymyxin B, K. pneumoniae 52145 took up more NPN (17,560 ± 200 RLU) than K. penumoniae 52K10 (10,450 ± 200 RLU). Each point represents the mean and standard deviation of four samples from two independently grown batches of bacteria, and significant differences between 52145 and 52K10 are indicated by asterisks. Symbols: •, K. pneumoniae 52145; ○, K. pneumoniae 52K10.
- FIG. 4.
CPS affects the binding of polymyxin B to the cell surface. Binding of polymyxin B to purified OMs (A), purified LPSs (B), and bacteria (C) is shown. Each point represents the mean and standard deviation (covered by the symbol) of four samples, and significant differences between 52145 and 52K10 are indicated by asterisks. Symbols: •, K. pneumoniae 52145; ○, K. pneumoniae 52K10.
Tables
- TABLE 1.
Effect of antimicrobial peptides on capsule polysaccharide production and transcriptiona
Induction condition Mean ± SD Amt of capsule (μg/104 CFU) RLU None 76.3 ± 7 1,269 ± 80 Protamine sulfate (50 μg/ml) 78.0 ± 5 1,223 ± 50 Polymyxin B (0.5 U/ml) 114.1 ± 4* 1,708 ± 40* Lactoferrin (100 μg/ml) 108.4 ± 10* 2,989 ± 97* ↵ a The amount of capsule was quantified by measuring uronic acid (a component of the K2 polymer). Luciferase activity was measured in a strain carrying the transcriptional fusion cps::lucFF and expressed as relative luminescence units (RLU). *, Significantly different from the result in the absence of inducing conditions (P < 0.05, [two-tailed t test]).
