Mean CFU/g faeces and corresponding standard deviation values are shown. The fim2 locus is not a virulence factor in a murine lung infection model K. pneumoniae is a clinically important cause of lung infections and various potential virulence factors have been determined [40, 41]. The influence of fim2 on pneumovirulence was investigated
by intranasal inoculation of five mice with a mixture comprising equal numbers of KR2107 and KR2107∆fim2. An 4SC-202 mw equivalent competition experiment between KR2107∆fim and KR2107∆fim∆fim2 was also performed. 30 h post-infection all mice displayed significant signs of disease and were sacrificed. High numbers of K. pneumoniae were found in the lungs of all mice (5 × 105 – 1 × 107 CFU/lung). Similar Fosbretabulin supplier lung CFU counts were obtained for both competition assays. Furthermore, no significant deviation in fim2-positive to fim2-negative strain ratios was evident for either competition assay (Figure 7A). These data suggest that both fim and fim2 do not impact significantly on pneumovirulence of K. pneumoniae in a murine lung infection model. Figure 7 Murine lung infection model studies with KR2107 and its isogenic fim and/or fim2 mutants. (A) Comparison of the ability of KR2107 and its isogenic mutants to infect the lungs as assessed by two head-to-head competition assays. A mixture containing an equal ratio of each competing
Salubrinal price strain was inoculated intranasally into five mice. The competitive index (CI) is the ratio of the number of fim2-positive to fim2-negative bacteria recovered from infected organs divided by the equivalent ratio as present in the intranasal inoculum. (B) Differential CFU counts for each of the competing strains in the liver at 30 h post-inoculation. (C) Liver CFU counts obtained in the five mice used for the competition assay between KR2107 and its
isogenic fim2 mutant. In A and B, horizontal bars represent the median, with data points for each mouse as indicated. The lower limit of detection is represented by the dotted line. P values were calculated using the Mann–Whitney U test. Total liver and spleen CFU counts were used as a measure of the ability of bacteria to disseminate from the lungs into the bloodstream. Much lower numbers and greater mouse-to-mouse variation occurred in CFU counts for the livers (<15 – 1.6 × 104) and spleens (<20 to – 200) of these mice. The median CFU count per liver for KR2107 (2.1 × 103) was elevated compared to that of KR2107∆fim2 (3.0 × 101), although this difference was not significant (P = 0.340). When liver CFU counts were examined individually for each mouse, two mice exhibited greater than 1-log more KR2107 than KR2107∆fim2, while the difference, though still hinting at an advantage for KR2107, was less than 0.5 log for two other mice (Figure 7B and C). The liver CFU counts in mouse 3 for both strains were equal to the lower limit of detection and extrapolated from a single colony each, thus preventing meaningful comparison of these values.